CN118019717A - Method for producing composite oxide and method for producing lithium ion battery - Google Patents

Abstract

The invention provides a method for manufacturing a positive electrode active material of a lithium ion battery which can be used in a low-temperature environment and has good discharge characteristics. The method for manufacturing the positive electrode active material comprises the following steps: a first step of heating lithium cobaltate having a median particle diameter (D50) of 10 [ mu ] m or less at a temperature of 700 ℃ to 1000 ℃ for 1 to 5 hours; a second step of producing a first mixture by mixing the lithium cobaltate subjected to the first step with a fluorine source and a magnesium source; a third step of heating the first mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 10 hours; a fourth step of producing a second mixture by mixing the first mixture subjected to the third step with a nickel source and an aluminum source; and a fifth step of heating the second mixture at a temperature of 800 ℃ to 950 ℃ for 1 hour to 5 hours.

Description

Method for producing composite oxide and method for producing lithium ion battery

Technical Field

The invention disclosed in the present specification and the like (hereinafter, referred to as "the invention" in some cases in the present specification and the like) relates to a power storage device, a secondary battery, and the like. And more particularly to a lithium ion battery.

In addition, the invention relates to an object, a method or a method of manufacturing. In addition, the present invention relates to a process, machine, product, or composition (composition of matter). The present invention also relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic apparatus, or a method for manufacturing the same.

Background

In recent years, various power storage devices such as lithium ion batteries, lithium ion capacitors, and air batteries have been under development. In particular, with the development of semiconductor industries such as portable information terminals such as mobile phones, smart phones, notebook computers, portable music players, digital cameras, medical equipment, hybrid Vehicles (HV), electric Vehicles (EV), and clean energy vehicles such as plug-in hybrid vehicles (PHV), the demand for lithium ion batteries with high output and high energy density has increased, and lithium ion batteries have become a necessity in modern information society as a rechargeable energy supply source.

The charge characteristics and/or discharge characteristics of a lithium ion battery vary according to the charge environment of the battery and/or the discharge environment of the battery. For example, it is known that the discharge capacity of a lithium ion battery varies according to the temperature at the time of discharge.

Therefore, a lithium ion battery having good battery characteristics even in a low-temperature environment is demanded (for example, refer to patent document 1).

[ Prior Art literature ]

[ Patent literature ]

Patent document 1 Japanese patent application laid-open No. 2015-026608

Disclosure of Invention

Technical problem to be solved by the invention

Patent document 1 describes that a lithium ion battery that can operate even in a low-temperature environment (for example, 0 ℃ or lower) can be realized by using the nonaqueous solvent described in patent document 1. However, in the stage of applying the present invention, even the lithium ion battery described in patent document 1 is difficult to say that the discharge capacity thereof is large when discharged in a low-temperature environment, and thus further improvement is desired.

In order to realize a lithium ion battery that can operate even in a low-temperature environment, it is necessary to develop not only a nonaqueous solvent (electrolyte) but also a positive electrode and a negative electrode that are suitable for a lithium ion battery that can operate even in a low-temperature environment. More specifically, the positive electrode is required to develop a positive electrode active material suitable for a lithium ion battery that can operate even in a low-temperature environment.

An object of one embodiment of the present invention is to provide a positive electrode active material for a lithium ion battery which can be used in a low-temperature environment and has excellent discharge characteristics. Specifically, an object of one embodiment of the present invention is to provide a positive electrode active material that can be used for a lithium ion battery having a large discharge capacity and/or a large discharge energy density even when discharge is performed in a low-temperature environment.

Note that in this specification and the like, "under a low-temperature environment" means 0 ℃ or lower. In the present specification, when the term "under a low-temperature environment" is used, an arbitrary temperature of 0 ℃ or lower may be selected. For example, in the present specification and the like, when the description is made as "under a low-temperature environment", one of 0 ℃ or lower, -10 ℃ or lower, -20 ℃ or lower, -30 ℃ or lower, -40 ℃ or lower, -50 ℃ or lower, -60 ℃ or lower, -80 ℃ or lower, and-100 ℃ or lower may be selected.

Another object of one embodiment of the present invention is to provide a lithium ion battery having excellent discharge characteristics even in a low-temperature environment. Another object of one embodiment of the present invention is to provide a lithium ion battery having excellent charging characteristics even in a low-temperature environment.

Specifically, an object of one embodiment of the present invention is to provide a lithium ion battery having a large discharge capacity and/or discharge energy density even when discharged in a low-temperature environment (for example, 0 ℃ or lower, -20 ℃ or lower, preferably-30 ℃ or lower, more preferably-40 ℃ or lower, still more preferably-50 ℃ or lower, and most preferably-60 ℃ or lower). It is another object of one embodiment of the present invention to provide a lithium ion battery which has a smaller reduction rate than a discharge capacity and/or a discharge energy density value when discharged at 25 ℃ even in a low-temperature environment (for example, 0 ℃ or lower, -20 ℃ or lower, preferably-30 ℃ or lower, more preferably-40 ℃ or lower, still more preferably-50 ℃ or lower, and most preferably-60 ℃ or lower).

Another object of one embodiment of the present invention is to provide a secondary battery having a high charging voltage. Another object of one embodiment of the present invention is to provide a secondary battery with high safety and reliability. Another object of one embodiment of the present invention is to provide a secondary battery with little degradation. Another object of one embodiment of the present invention is to provide a secondary battery with a long life. In addition, it is an object of one embodiment of the present invention to provide a novel secondary battery.

Another object of one embodiment of the present invention is to provide a novel substance, an active material, a power storage device, or a method for producing the same.

Note that the description of these objects does not hinder the existence of other objects. One embodiment of the present invention does not need to solve all of the above objects. Further, objects other than the above objects may be extracted from the descriptions of the present specification, drawings, claims, and the like.

Means for solving the technical problems

In order to solve the above-described object, one embodiment of the present invention has the following structure.

One embodiment of the present invention is a method for producing a composite oxide, including the steps of: a first step of heating lithium cobaltate having a median particle diameter (D50) of 10 [ mu ] m or less at a temperature of 700 ℃ to 1000 ℃ for 1 to 5 hours; a second step of producing a first mixture by mixing the lithium cobaltate subjected to the first step with a fluorine source and a magnesium source; a third step of heating the first mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 10 hours; a fourth step of producing a second mixture by mixing the first mixture subjected to the third step with a nickel source and an aluminum source; and a fifth step of heating the second mixture at a temperature of 800 ℃ to 950 ℃ for 1 hour to 5 hours.

In one embodiment of the present invention, the magnesium source contains magnesium in an atomic number of 0.3% or more and 3% or less of the atomic number of cobalt contained in the lithium cobaltate subjected to the first step.

In one embodiment of the present invention, the fluorine source is lithium fluoride, the magnesium source is magnesium fluoride, and a ratio of a molar number M _LiF of the lithium fluoride to a molar number M _MgF2 of the magnesium fluoride is M _LiF：M_MgF2 =x: 1 (0.1.ltoreq.x.ltoreq.0.5).

In one embodiment of the present invention, the nickel source contains nickel in an atomic number of 0.05% to 4% of the atomic number of cobalt contained in the lithium cobaltate subjected to the first step.

In one embodiment of the present invention, the aluminum source contains aluminum in an atomic number of 0.05% to 4% of the atomic number of cobalt contained in the lithium cobaltate subjected to the first step.

Alternatively, in one embodiment of the present invention, the first step is performed in an atmosphere containing oxygen in a state where a lid is covered with a sagger containing the lithium cobaltate.

Another embodiment of the present invention is a method for manufacturing a lithium ion battery having a positive electrode including a positive electrode active material, an electrolyte, and a negative electrode including a negative electrode active material that is a carbon material, wherein the positive electrode active material is formed by: a first step of heating lithium cobaltate having a median particle diameter (D50) of 10 [ mu ] m or less at a temperature of 700 ℃ to 1000 ℃ for 1 to 5 hours; a second step of producing a first mixture by mixing the lithium cobaltate subjected to the first step with a fluorine source and a magnesium source; a third step of heating the first mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 10 hours; a fourth step of producing a second mixture by mixing the first mixture subjected to the third step with a nickel source and an aluminum source; and a fifth step of heating the second mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 5 hours.

Another embodiment of the present invention is a method for producing a lithium ion battery having a positive electrode including a positive electrode active material, an electrolyte, and a negative electrode including a negative electrode active material that is a carbon material, wherein the electrolyte includes ethylene carbonate, methylethyl carbonate, and dimethyl carbonate, and a ratio of V _EC of the volume of ethylene carbonate, V _EMC of the volume of methylethyl carbonate, and V _DMC of the volume of dimethyl carbonate is V _EC：V_EMC：V_DMC =x: y:100-x-y (note that 5.ltoreq.x.ltoreq.35 and 0< y < 65), and the positive electrode active material is formed by the steps of: a first step of heating lithium cobaltate having a median particle diameter (D50) of 10 [ mu ] m or less at a temperature of 700 ℃ to 1000 ℃ for 1 to 5 hours; a second step of producing a first mixture by mixing the lithium cobaltate subjected to the first step with a fluorine source and a magnesium source; a third step of heating the first mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 10 hours; a fourth step of producing a second mixture by mixing the first mixture subjected to the third step with a nickel source and an aluminum source; and a fifth step of heating the second mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 5 hours.

Effects of the invention

According to one embodiment of the present invention, a positive electrode active material that can be used in a lithium ion battery having good discharge characteristics even in a low-temperature environment can be provided. Specifically, according to one embodiment of the present invention, a positive electrode active material that can be used for a lithium ion battery having a large discharge capacity and/or a large discharge energy density even when discharge is performed in a low-temperature environment can be provided.

According to one embodiment of the present invention, a lithium ion battery having a large discharge capacity and/or discharge energy density even when discharged in a low-temperature environment (for example, 0 ℃ or lower, -20 ℃ or lower, preferably-30 ℃ or lower, more preferably-40 ℃ or lower, still more preferably-50 ℃ or lower, and most preferably-60 ℃ or lower) can be provided. Further, according to an embodiment of the present invention, there can be provided a lithium ion battery having a smaller reduction rate than a value of discharge capacity and/or discharge energy density when discharging at 25 ℃ even when discharging at a low temperature environment (for example, 0 ℃ or lower, -20 ℃ or lower, preferably-30 ℃ or lower, more preferably-40 ℃ or lower, still more preferably-50 ℃ or lower, and most preferably-60 ℃ or lower).

Further, according to an embodiment of the present invention, a secondary battery having a high charging voltage can be provided. Further, according to an embodiment of the present invention, a secondary battery with high safety or reliability can be provided. Further, according to an embodiment of the present invention, a secondary battery with little degradation can be provided. In addition, according to an embodiment of the present invention, a long-life secondary battery can be provided. In addition, according to one embodiment of the present invention, a novel secondary battery may be provided.

Further, according to one embodiment of the present invention, a novel substance, an active material, a power storage device, or a method for manufacturing the same can be provided.

Drawings

Fig. 1A to 1D are diagrams illustrating a method for producing a positive electrode active material.

Fig. 2 is a diagram illustrating a manufacturing method of the positive electrode active material.

Fig. 3A to 3C are diagrams illustrating a method for manufacturing a positive electrode active material.

Fig. 4A to 4D are sectional views illustrating examples of the positive electrode of the secondary battery.

Fig. 5A is an exploded perspective view of the coin-type secondary battery, fig. 5B is a perspective view of the coin-type secondary battery, and fig. 5C is a cross-sectional perspective view thereof.

Fig. 6A shows an example of a cylindrical secondary battery. Fig. 6B shows an example of a cylindrical secondary battery. Fig. 6C shows an example of a plurality of cylindrical secondary batteries. Fig. 6D shows an example of an electric storage system including a plurality of cylindrical secondary batteries.

Fig. 7A and 7B are diagrams illustrating examples of secondary batteries, and fig. 7C is a diagram illustrating an internal condition of the secondary battery.

Fig. 8A to 8C are diagrams illustrating examples of secondary batteries.

Fig. 9A and 9B are external views of the secondary battery.

Fig. 10A to 10C are diagrams illustrating a method of manufacturing a secondary battery.

Fig. 11A shows a structural example of a battery pack, fig. 11B shows a structural example of a battery pack, and fig. 11C shows a structural example of a battery pack.

Fig. 12A is a perspective view showing a battery pack according to an embodiment of the present invention, fig. 12B is a block diagram of the battery pack, and fig. 12C is a block diagram of a vehicle including an engine.

Fig. 13A to 13D are diagrams illustrating an example of a transport vehicle. Fig. 13E is a diagram illustrating an example of a satellite vehicle.

Fig. 14A and 14B are diagrams illustrating an electric storage device according to an embodiment of the present invention.

Fig. 15A is a view showing an electric bicycle, fig. 15B is a view showing a secondary battery of the electric bicycle, and fig. 15C is a view explaining an electric motorcycle.

Fig. 16A to 16D are diagrams illustrating an example of an electronic device.

Fig. 17A shows an example of a wearable device, fig. 17B shows a perspective view of a wristwatch type device, and fig. 17C is a diagram illustrating a side face of the wristwatch type device.

Fig. 18 is a graph showing the particle size distribution of lithium cobaltate described in example 1.

Fig. 19A is a diagram showing SEM observation results of lithium cobalt oxide described in example 1, and fig. 19B is a diagram showing SEM observation results of lithium cobalt oxide as a starting material.

Fig. 20 is an external photograph of the secondary battery.

Fig. 21 is a graph showing discharge curves (temperature characteristics) for respective temperatures of the secondary battery.

Fig. 22 is a graph showing a charge curve and a discharge curve for each temperature of the secondary battery.

Detailed Description

The present embodiment will be described with appropriate reference to the drawings. Note that the present invention is not limited to the following description. It will be readily understood by those skilled in the art that the modes and details of the invention may be modified in various ways without departing from the spirit and scope of the invention. Accordingly, in the embodiments shown below, reference numerals representing the same components of the invention are common among the different figures.

Note that the following embodiments and examples can be appropriately combined with the embodiments and examples described in this specification and the like, unless otherwise specified.

In this specification and the like, the term "electronic apparatus" refers to all devices having a power storage device, and an electro-optical device having a power storage device, an information terminal device having a power storage device, and the like are electronic apparatuses.

Note that in this specification and the like, "power storage device" refers to all elements and devices having a power storage function. Examples thereof include a power storage device such as a lithium ion battery (also referred to as a "secondary battery"), a lithium ion capacitor, and an electric double layer capacitor.

In the present specification and the like, a space group is represented by a Short term of an international symbol (or Hermann-Mauguin symbol). In addition, the crystal plane and the crystal orientation are represented by miller indices. In crystallography, numbers are marked with superscript horizontal lines to represent space groups, crystal planes, and crystal orientations. (negative sign) to indicate space group, crystal face and crystal orientation, instead of superscript transversal line attached to the number. In addition, individual orientations showing orientations within the crystal are denoted by "[ ]", collective orientations showing all equivalent orientations are denoted by "< >", individual faces showing crystal faces are denoted by "()" and collective faces having equivalent symmetry are denoted by "{ }". In general, for ease of understanding the structure, the trigonal system represented by the space group R-3m is represented by a composite hexagonal lattice of hexagonal lattices, and in this specification, the space group R-3m is also represented by a composite hexagonal lattice unless otherwise specified. In addition, in some cases, (hkil) is used as the miller index in addition to (hkl). Here, i is- (h+k).

In the present specification and the like, the theoretical capacity of the positive electrode active material refers to the amount of electricity when all of lithium capable of intercalating and deintercalating in the positive electrode active material is deintercalated. For example, liCoO ₂ has a theoretical capacity of 274mAh/g, liNiO ₂ has a theoretical capacity of 275mAh/g, and LiMn ₂O₄ has a theoretical capacity of 148mAh/g.

For example, the amount of lithium that can be inserted and removed remaining in the positive electrode active material may be represented by x (the Li occupancy rate at the lithium position) in Li _xCoO₂. In the case of a positive electrode active material in a secondary battery, x= (theoretical capacity-charge capacity)/theoretical capacity. For example, when a secondary battery using LiCoO ₂ as a positive electrode active material is charged to 219.2mAh/g, it can be said that Li _0.2CoO₂ or x=0.2. The smaller x state in Li _xCoO₂ means, for example, x.ltoreq.0.24, and when the actual range is considered for a lithium ion battery, means, for example, 0.1< x.ltoreq.0.24.

When lithium cobaltate approximately satisfies the stoichiometric ratio, liCoO ₂ is used and x=1. In addition, lithium cobaltate in the secondary battery after the end of discharge can be said to be LiCoO ₂ and x=1. In addition, in general, the discharge voltage of a lithium ion battery using LiCoO ₂ drops sharply before reaching 2.5V. Therefore, in the present specification and the like, for example, a state in which a current of 100mA/g or less reaches a voltage of 2.5V (lithium is used as a counter electrode) is regarded as a discharge end state, and x=1. Therefore, for example, in order to obtain lithium cobalt oxide with x=0.2, 219.2mAh/g of the lithium cobalt oxide may be charged from the discharge-completed state.

The charge capacity and/or discharge capacity for calculating x in Li _xCoO₂ is preferably measured under the condition that there is no or little influence of decomposition of the short circuit and/or the electrolyte. For example, data of the secondary battery in which a sudden voltage change or a sudden capacity change, which is regarded as a short circuit, occurs is preferably not used for the calculation of x.

The space group of the crystal structure is identified by XRD, electron diffraction, neutron diffraction, or the like. Therefore, in the present specification and the like, the term "belonging to a certain space group" or "space group" means that the space group is identified as a certain space group.

In addition, a structure in which three layers of anions are stacked so as to deviate from each other like abcab is called a "cubic closest packing structure". Thus, the anions may also be loosely cubic lattice. Meanwhile, crystals have defects in practice, so that the analysis result may not be based on theory. For example, spots may occur at positions slightly different from the theoretical positions in an FFT (fast fourier transform) pattern such as an electron diffraction pattern or a TEM image. For example, it can be said that the cube closest packing structure is provided when the difference in orientation from the theoretical position is 5 ° or less or 2.5 ° or less.

In the present specification and the like, "layered rock salt crystal structure of a composite oxide containing lithium and a transition metal" means the following crystal structure: the rock salt type ion arrangement having alternate arrangement of cations and anions, the transition metal and lithium are regularly arranged to form a two-dimensional plane, and thus lithium can be two-dimensionally diffused therein. Defects such as vacancies of cations and anions may be included. Strictly speaking, the layered rock-salt type crystal structure is sometimes a structure in which the crystal lattice of the rock-salt type crystal is deformed.

In this specification and the like, "rock salt type crystal structure" refers to a structure in which cations and anions are alternately arranged. In addition, vacancies of cations or anions may also be included.

In this specification and the like, "homogeneity" refers to a phenomenon in which an element (e.g., a) is distributed in a solid containing a plurality of elements (e.g., A, B, C) with the same characteristics in a specific region. Specifically, the element concentration may be substantially the same between specific regions. For example, the difference in element concentration in the specific region may be within 10%. The specific region may be, for example, a surface layer portion, a surface, a convex portion, a concave portion, an interior portion, or the like.

In the present specification and the like, "segregation" refers to a phenomenon in which an element (e.g., B) is spatially unevenly distributed in a solid containing a plurality of elements (e.g., A, B, C). Or that the concentration of an element is different from the concentration of other elements. Segregation is synonymous with non-uniform distribution, precipitation, non-uniformity, variation, and mixing with regions of high concentration or regions of low concentration.

In the present specification, the term "surface layer portion" of the particles of the active material or the like means, for example, a region within 50nm, more preferably within 35nm, still more preferably within 20nm, and most preferably within 10nm from the surface. In addition, the surface generated by the split or the crack can be regarded as a surface. In this specification, a region deeper than the surface layer portion may be referred to as an "inside". In the present specification and the like, the term "grain boundary" means, for example, the following: a portion where the particles adhere together; a portion in which the crystal orientation changes inside the particle (including the central portion); a portion containing more defects; a portion with disordered crystalline structure; etc. In addition, the grain boundary is also one of the surface defects. The term "vicinity of grain boundary" means a region within 20nm, preferably within 10nm, from the grain boundary. In the present specification and the like, the "particles" are not limited to a spherical shape (a cross-sectional shape is a circle), and the cross-sectional shape of each particle may be an ellipse, a rectangle, a trapezoid, a cone, a quadrangle with curved corners, an asymmetric shape, or the like, and each particle may be amorphous.

(Embodiment 1)

In this embodiment, a method for manufacturing a positive electrode active material that can be used in a lithium ion battery having good discharge characteristics even in a low-temperature environment will be described with reference to fig. 1 to 3.

< Method for producing cathode active material example 1>

An example of a method for producing a positive electrode active material (example 1 of a method for producing a positive electrode active material) that can be used in one embodiment of the present invention will be described with reference to fig. 1A to 1D.

First, as step S10, lithium cobalt oxide is prepared as a starting material. As the lithium cobaltate used as the starting material, lithium cobaltate having a particle diameter (to be precise, a median particle diameter (D50)) of 10 μm or less (preferably 8 μm or less) can be used. Note that in this specification and the like, unless otherwise specified, the median particle diameter refers to D50 (particle diameter at which the frequency is accumulated to be 50%). As the lithium cobaltate having a median particle diameter (D50) of 10 μm or less, known or publicly used (in short, commercially available) lithium cobaltate may be used, or lithium cobaltate produced by steps S11 to S14 shown in fig. 1B may be used. Typical examples of commercially available lithium cobalt oxide having a median particle diameter (D50) of 10 μm or less include lithium cobalt oxide (trade name "CELLSEED C-5H") manufactured by Japanese chemical industry Co. The median particle diameter (D50) of lithium cobaltate (trade name "CELLSEED C-5H") manufactured by Japanese chemical industry Co., ltd.) was about 7. Mu.m. The following describes a method for producing lithium cobaltate having a median particle diameter (D50) of 10 μm or less obtained in steps S11 to S14.

< Step S11>

In step S11 shown in fig. 1B, a lithium source (Li source) and a cobalt source (Co source) are prepared as materials of lithium and a transition metal as starting materials, respectively.

As the lithium source, a compound containing lithium is preferably used, and for example, lithium carbonate, lithium hydroxide, lithium nitrate, lithium fluoride, or the like can be used. The purity of the lithium source is preferably high, and for example, a material having a purity of 99.99% or more is preferably used.

As the cobalt source, a compound containing cobalt is preferably used, and for example, tricobalt tetraoxide, cobalt hydroxide, or the like can be used. The purity of the cobalt source is preferably high, and for example, a material having a purity of 3N (99.9%) or more, preferably 4N (99.99%) or more, more preferably 4N5 (99.995%) or more, and even more preferably 5N (99.999%) or more is preferably used. By using a material of high purity, impurities in the positive electrode active material can be controlled. As a result, the capacity of the secondary battery is improved, and thus the reliability of the secondary battery is improved.

The cobalt source preferably has high crystallinity, and for example, preferably has single crystal particles. Examples of the method for evaluating crystallinity of the transition metal source include: judgment using a TEM (transmission electron microscope) image, STEM (scanning transmission electron microscope) image, HAADF-STEM (high angle annular dark field-scanning transmission electron microscope) image, ABF-STEM (annular bright field scanning transmission electron microscope) image, or the like; or by X-ray diffraction (XRD), electron diffraction, neutron diffraction, or the like. The method for evaluating crystallinity described above may evaluate other crystallinity in addition to the transition metal source.

< Step S12>

Next, as step S12 shown in fig. 1B, a lithium source and a cobalt source are crushed and mixed to produce a mixed material. The pulverization and mixing may be performed in a dry or wet method. The material may be ground to be finer by wet grinding and mixing, and it is preferable to grind and mix by wet grinding in order to obtain lithium cobaltate having a median particle diameter (D50) of 10 μm or less as a starting material. In addition, a solvent is prepared when pulverizing and mixing by a wet method. As the solvent, ketones such as acetone, alcohols such as ethanol and isopropanol, diethyl ether, dioxane, acetonitrile, N-methyl-2-pyrrolidone (NMP) and the like can be used, but an aprotic solvent which does not react easily with lithium is preferably used. In this embodiment, dehydrated acetone having a purity of 99.5% or more is used. Preferably, dehydrated acetone having a purity of 99.5% or more, which is obtained by mixing a lithium source and a transition metal source to a water content of 10ppm or less, is used for pulverization and mixing. By using the dehydrated acetone having the above purity, impurities which may be mixed in can be reduced.

As a means for performing pulverization, mixing, or the like, a ball mill, a sand mill, or the like can be used. When a ball mill is used, alumina balls or zirconia balls are preferably used as the pulverizing medium. The zirconia balls are preferable because of less discharge of impurities. In the case of using a ball mill, a sand mill, or the like, the peripheral speed is preferably set to 100mm/s or more and 2000mm/s or less in order to suppress contamination from the medium. In the present embodiment, the peripheral speed is preferably set to 838mm/s (the number of revolutions is 400rpm, and the diameter of the ball mill is 40 mm) and the mixture is pulverized.

< Step S13>

Next, as step S13 shown in fig. 1B, the above-described mixed material is heated. The heating is preferably performed at 800 ℃ to 1100 ℃, more preferably at 900 ℃ to 1000 ℃, still more preferably at 950 ℃ or so and 1000 ℃ or less. If the temperature is too low, there is a concern that the decomposition and melting of the lithium source and the transition metal source are insufficient. On the other hand, when the temperature is too high, defects may occur due to the following reasons: lithium is evaporated from a lithium source; and/or cobalt is excessively reduced; etc. For example, cobalt changes from trivalent to divalent, causing oxygen defects, and the like.

Lithium cobaltate is not synthesized when the heating time is too short, but productivity is lowered when the heating time is too long. Therefore, the heating time is preferably 1 hour or more and 100 hours or less, more preferably 2 hours or more and 20 hours or less, and still more preferably 2 hours or more and 10 hours or less.

Although it varies depending on the temperature to which the heating temperature is applied, the heating rate is preferably 80 ℃ per hour or more and 250 ℃ per hour or less. For example, in the case of heating at 1000℃for 10 hours, the heating rate is preferably 200℃per hour.

The heating is preferably performed in an atmosphere having less water such as dry air, for example, in an atmosphere having a dew point of-50 ℃ or lower, and more preferably in an atmosphere having a dew point of-80 ℃ or lower. In this embodiment, heating is performed in an atmosphere having a dew point of-93 ℃. In order to suppress impurities that may be mixed into the material, the impurity concentrations of CH ₄、CO、CO₂, H ₂, and the like in the heating atmosphere are preferably 5 to ppb (parts per billion).

The heating atmosphere is preferably an oxygen-containing atmosphere. For example, there is a method of continuously introducing dry air into the reaction chamber. In this case, the flow rate of the drying air is preferably 10L/min. The method of continuing to introduce oxygen into the reaction chamber and flowing the oxygen into the reaction chamber is called "flow".

In the case of using an oxygen-containing atmosphere as the heating atmosphere, a non-flowing method may be employed. For example, a method of filling oxygen by first depressurizing the reaction chamber to prevent the oxygen from leaking from the reaction chamber or the oxygen from entering the reaction chamber may be employed, and this method is referred to as purging. For example, the reaction chamber is depressurized to-970 hPa, and then the oxygen is continuously filled up to 50 hPa.

The cooling time from the predetermined temperature to room temperature is preferably in the range of 10 hours to 50 hours. Note that cooling to room temperature is not necessarily required, and cooling to a temperature allowed in the next step is sufficient.

In the heating in this step, heating by a rotary kiln (rotary kiln) or a roller kiln (roller HEARTH KILN) may be performed. Heating using a rotary kiln of a continuous type or a batch type (batch-type) may be performed while stirring.

The heating device is preferably an alumina crucible or an alumina sagger. Alumina crucible is made of material which hardly mixes with impurities. In this embodiment, an alumina sagger having a purity of 99.9% was used. In addition, the crucible or the sagger is preferably heated after the lid is covered, so that volatilization of the material can be prevented.

After the heating is completed, the powder may be pulverized and optionally screened. In recovering the heated material, the heated material may be recovered after moving from the crucible to the mortar. The mortar is preferably made of zirconia or agate. In the heating step other than step S13, the same heating conditions as in step S13 may be used.

< Step S14>

Through the above steps, lithium cobalt oxide (LiCoO ₂) shown in step S14 shown in fig. 1B can be synthesized. The lithium cobalt oxide (LiCoO ₂) shown in step S14 is an oxide containing a plurality of metal elements in its structure, and therefore may also be referred to as a composite oxide. Further, after step S13, the pulverizing step and the classifying step may be performed to adjust the particle size distribution, thereby obtaining lithium cobalt oxide (LiCoO ₂) shown in step S14.

As shown in steps S11 to S14, an example of manufacturing the composite oxide by the solid phase method is shown, but the composite oxide may be manufactured by the coprecipitation method. In addition, the composite oxide may be produced by a hydrothermal method.

By the steps S11 to S14, lithium cobaltate, which is a starting material for obtaining a positive electrode active material of a lithium ion battery that can be used in a low-temperature environment and also has excellent discharge characteristics, can be obtained. Specifically, as the starting material, lithium cobaltate having a median particle diameter (D50) of 10 μm or less can be obtained.

< Step S15>

Next, as step S15 shown in fig. 1A, the starting material lithium cobaltate is heated. The heating in step S15 is the first heating of lithium cobaltate, and therefore this heating may be referred to as initial heating in this specification or the like. In addition, the method comprises the following steps. This heating is also performed before step S31 shown below, and may be referred to as a preheating treatment or a pretreatment.

The lithium compound remaining on the surface of lithium cobaltate is not intentionally detached due to initial heating. In addition, an effect of improving the internal crystallinity can be expected. In addition, although impurities may be mixed in the lithium source and/or cobalt source prepared in step S11 or the like, the impurities in the starting material lithium cobaltate may be reduced by performing initial heating. The effect of improving the internal crystallinity is, for example, an effect of reducing distortion, deviation, or the like, which occurs due to a difference in shrinkage of lithium cobaltate or the like produced in step S14.

In addition, the initial heating has the effect of smoothing the surface of lithium cobaltate. In addition, by performing initial heating, cracks, crystal defects, and the like of lithium cobaltate can be relaxed. In the present specification and the like, the surface "smooth" means a state in which irregularities are less curved as a whole and corners are curved. In addition, a state in which foreign matter adhering to the surface is less is also referred to as "smoothing". It is considered that the foreign matter is a cause of the irregularities, and it is preferable that the foreign matter is not attached to the surface.

Note that when this initial heating is performed, a material serving as a lithium compound source, an additive element a source, or a flux may not be separately prepared.

When the heating time in this step is too short, a sufficient effect cannot be obtained, but when the heating time is too long, productivity is lowered. The range of the appropriate heating time may be selected from the heating conditions described in step S13, for example. In addition, in order to maintain the crystal structure of the composite oxide, the heating temperature of step S15 is preferably lower than the temperature of step S13. In addition, in order to maintain the crystal structure of the composite oxide, the heating time of step S15 is preferably shorter than that of step S13. For example, the heating is preferably performed at a temperature of 700 ℃ to 1000 ℃ (more preferably 800 ℃ to 900 ℃), for 1 hour to 20 hours (more preferably 1 hour to 5 hours).

In lithium cobaltate, a temperature difference may occur between the surface and the inside of lithium cobaltate by the heating in step S13. Sometimes the temperature difference results in a difference in shrinkage. It can also be considered that: shrinkage differences occur because the surface and interior flow properties differ according to temperature differences. The difference in internal stress occurs in lithium cobaltate due to energy associated with the difference in shrinkage. The difference in internal stress is also known as distortion and this energy is sometimes referred to as distortion energy. It can be considered that: the internal stress is removed by the initial heating of step S15, in other words, the distortion can be homogenized by the initial heating of step S15. When the distortion can be uniformized, the distortion of lithium cobaltate is relaxed. Thus, the surface of lithium cobaltate may be smoothed. Or it can be said that the surface is improved. That is, the difference in shrinkage occurring in lithium cobaltate is alleviated by step S15, and the surface of the composite oxide can be smoothed.

In addition, the difference in shrinkage sometimes causes the generation of minute deviations in lithium cobaltate such as the generation of deviations of crystallization. In order to reduce this deviation, the heating in step S15 is preferably performed. In step S15, the deviation of the composite oxide can be uniformized (the deviation of crystals or the like generated in the composite oxide is alleviated or crystal grains are aligned). As a result, the surface of the composite oxide becomes smooth.

By using lithium cobaltate with a smooth surface as the positive electrode active material, deterioration in charge and discharge as the secondary battery is reduced, and cracking of the positive electrode active material can be prevented.

As described above, lithium cobaltate having a previously synthesized median particle diameter (D50) of 10 μm or less may be used as step S10. In this case, steps S11 to S13 may be omitted. By performing step S15 on the previously synthesized lithium cobalt oxide, a smooth surface lithium cobalt oxide can be obtained.

Note that step S15 is not an essential structure in one embodiment of the present invention, and so a case where step S15 is omitted is also included in one embodiment of the present invention.

< Step S20>

Next, the details of step S20 of preparing the addition element a as the a source will be described with reference to fig. 1C and 1D.

< Step S21>

Step S20 shown in fig. 1C includes steps S21 to S23. In step S21, an additive element a is prepared. As specific examples of the additive element a, one or more selected from magnesium, fluorine, nickel, aluminum, titanium, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, and boron may be used. In addition, one or two or more selected from bromine and beryllium may be used. Fig. 1C shows an example of preparing a magnesium source (Mg source) and a fluorine source (F source). Note that in step S21, a lithium source may be prepared in addition to the additive element a.

When magnesium is selected as the additive element a, the additive element a source may be referred to as a magnesium source. As the magnesium source, magnesium fluoride (MgF ₂), magnesium oxide (MgO), magnesium hydroxide (Mg (OH) ₂), magnesium carbonate (MgCO ₃), or the like can be used. Multiple sources of magnesium may also be used.

When fluorine is selected as the additive element a, the additive element a source may be referred to as a fluorine source. As the fluorine source, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂), aluminum fluoride (AlF ₃), titanium fluoride (TiF ₄), cobalt fluoride (CoF ₂、CoF₃), nickel fluoride (NiF ₂), zirconium fluoride (ZrF ₄), vanadium fluoride (VF ₅), manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, zinc fluoride (ZnF ₂), calcium fluoride (CaF ₂), sodium fluoride (NaF), potassium fluoride (KF), barium fluoride (BaF ₂), cerium fluoride (CeF ₃、CeF₄), lanthanum fluoride (LaF ₃), or sodium aluminum hexafluoride (Na ₃AlF₆) can be used. Among them, lithium fluoride is preferable because it has a low melting point, that is, 848 ℃ and is easily melted in a heating step described later.

Magnesium fluoride can be used as both a fluorine source and a magnesium source. In addition, lithium fluoride may also be used as a lithium source. As another lithium source used in step S21, lithium carbonate may be mentioned.

The fluorine source may be a gas, and fluorine (F ₂), carbon fluoride, sulfur fluoride, oxygen fluoride (OF₂、O₂F₂、O₃F₂、O₄F₂、O₅F₂、O₆F₂、O₂F), or the like may be mixed in an atmosphere in a heating step described later. Multiple fluorine sources may also be used.

In this embodiment, lithium fluoride (LiF) was prepared as a fluorine source, and magnesium fluoride (MgF ₂) was prepared as a fluorine source and a magnesium source. When lithium fluoride and magnesium fluoride are present as LiF: mgF ₂ = 65:35 When mixed in about (molar ratio), it is most effective in lowering the melting point. In addition, when the proportion of lithium fluoride is too large, lithium becomes too large, and the cycle characteristics may be deteriorated. For this purpose, the molar ratio of lithium fluoride to magnesium fluoride is preferably LiF: mgF ₂ = x:1 (0.ltoreq.x.ltoreq.1.9), more preferably LiF: mgF ₂ = x:1 (0.1. Ltoreq.x. Ltoreq.0.5), more preferably LiF: mgF ₂ = x:1 (x=0.33 and its vicinity). Note that when not specifically described in this specification or the like, the vicinity means a value greater than 0.9 times and less than 1.1 times its value.

< Step S22>

Next, in step S22 shown in fig. 1C, the magnesium source and the fluorine source are pulverized and mixed. The present step may be performed by selecting the conditions for pulverization and mixing described in step S12.

< Step S23>

Next, in step S23 shown in fig. 1C, the above-mentioned crushed and mixed material is recovered to obtain an additive element a source (a source). The source of additive element a shown in step S23 comprises a plurality of starting materials, which may also be referred to as a mixture.

The median particle diameter (D50) of the mixture is preferably 100nm or more and 10 μm or less, more preferably 300 μm or more and 5 μm or less. When a material is used as the source of the additive element A, the median particle diameter (D50) is preferably 100nm or more and 10 μm or less, more preferably 300 μm or more and 5 μm or less.

When the mixture micronized by step S22 (including the case where the additive element is one) is mixed with lithium cobalt oxide in a later process, it is easy to uniformly adhere the mixture to the surface of lithium cobalt oxide. When the mixture is uniformly adhered to the surface of lithium cobaltate, it is easy to uniformly distribute or diffuse the additive element in the surface layer portion of the composite oxide after heating, so that it is preferable.

< Step S21>

A process different from that of fig. 1D will be described with reference to fig. 1C. Step S20 shown in fig. 1D includes steps S21 to S23.

In step S21 shown in fig. 1D, four sources of additive element a added to lithium cobaltate are prepared. That is, the type of the source of the additive element a of fig. 1D is different from that of fig. 1C. In addition, a lithium source may be prepared in addition to the source of the element a.

As four kinds of additive element a sources, a magnesium source (Mg source), a fluorine source (F source), a nickel source (Ni source), and an aluminum source (Al source) were prepared. The magnesium source and the fluorine source may be selected from the compounds illustrated in fig. 1C, and the like. As the nickel source, nickel oxide, nickel hydroxide, or the like can be used. As the aluminum source, aluminum oxide, aluminum hydroxide, or the like can be used.

< Step S22 and step S23>

Next, step S22 and step S23 shown in fig. 1D are similar to step S22 and step S23 described in fig. 1C.

< Step S31>

Next, in step S31 shown in fig. 1A, lithium cobaltate subjected to step S15 (initial heating) and an additive element a source (Mg source) are mixed. Here, the ratio of the atomic number Co of cobalt in lithium cobaltate to the atomic number Mg of magnesium in the source of additive element a through step S15 is preferably Co: mg=100: y (0.1. Ltoreq.y.ltoreq.6), more preferably Co: mg=100: y (y is more than or equal to 0.3 and less than or equal to 3). In addition, when the additive element a is added to the lithium cobaltate subjected to initial heating, the additive element a may be added uniformly. Therefore, it is preferable to adopt the order of adding the additive element a after the initial heating (step 15), rather than adopting the order of performing the initial heating (step 15) after the additive element a is added.

When nickel is selected as the additive element a, it is preferable to perform the mixing in step S31 so that the atomic number of nickel in the nickel source is 0.05% or more and 4% or less with respect to the atomic number of cobalt in the lithium cobaltate subjected to step S15. When aluminum is selected as the additive element a, it is preferable to perform the mixing in step S31 so that the atomic number of aluminum in the aluminum source is 0.05% or more and 4% or less with respect to the atomic number of cobalt in the lithium cobaltate subjected to step S15.

In order not to damage the shape of the lithium cobaltate particles, the mixing of step S31 is preferably performed under milder conditions than the mixing of step S12. For example, it is preferable to use a condition that the number of revolutions is smaller or the time is shorter than the number of revolutions of the pulverization/mixing in step S12. In addition, it can be said that the dry method is a milder condition than the wet method. The mixing may be performed by a ball mill, a sand mill, or the like. When using a ball mill, for example, zirconia balls are preferably used as a medium.

In this embodiment, mixing was performed by dry method at 150rpm for 1 hour using a ball mill using zirconia balls having a diameter of 1 mm. The mixing is performed in a drying chamber having a dew point of-100 ℃ or higher and-10 ℃ or lower.

< Step S32>

Next, in step S32 of fig. 1A, the above-described mixed materials are recovered to obtain a mixture 903. In the case of recovery, screening may be performed after grinding, if necessary.

< Step S33>

Next, in step S33 shown in fig. 1A, the mixture 903 is heated. The heating in step S33 is preferably performed at 800 ℃ or higher and 1100 ℃ or lower, more preferably 800 ℃ or higher and 950 ℃ or lower, and still more preferably 850 ℃ or higher and 900 ℃ or lower. The heating time in step S33 may be 1 hour or more and 100 hours or less, and preferably 1 hour or more and 10 hours or less. The lower limit value of the heating temperature in step S33 needs to be equal to or higher than the temperature at which the reaction between lithium cobaltate and the source of additive element a proceeds. The temperature at which the reaction proceeds may be set to a temperature at which interdiffusion of lithium cobaltate and the element contained in the source of the additive element a occurs, or may be lower than the melting temperature of the above-described material. For example, in the case of oxide, solid-phase diffusion occurs from 0.757 times the melting temperature T _m (taman temperature T _d). Therefore, the heating temperature in step S33 may be set to 500 ℃.

Note that when one or more temperatures at which one or more selected from the materials contained in the mixture 903 are melted or higher are set, the reaction proceeds more easily. For example, when LiF and MgF ₂ are contained as the additive element a source, the eutectic point of LiF and MgF ₂ is around 742 ℃, so the lower limit of the heating temperature in step S33 is preferably set to 742 ℃ or higher.

In addition, with LiCoO ₂：LiF：MgF₂ =100: 0.33:1 (molar ratio), and an endothermic peak was observed near 830 ℃ in the differential scanning calorimeter (DSC measurement) of the mixture 903 obtained by mixing. Therefore, the lower limit of the heating temperature is more preferably 830 ℃.

The higher the heating temperature, the more easily the reaction proceeds, the shorter the heating time and the higher the productivity, so that it is preferable.

The upper limit of the heating temperature was set to be lower than the decomposition temperature (1130 ℃) of lithium cobaltate. At a temperature around the decomposition temperature, there is a possibility that minute decomposition of lithium cobaltate occurs. Therefore, the heating temperature is preferably 1000 ℃ or lower, more preferably 950 ℃ or lower, and even more preferably 900 ℃ or lower.

In addition, when the mixture 903 is heated, the partial pressure of fluorine or fluoride due to a fluorine source or the like is preferably controlled to be within an appropriate range.

In the production method described in this embodiment, some materials such as LiF as a fluorine source may be used as a flux. By the above-described function, the heating temperature can be reduced to a temperature lower than the decomposition temperature of lithium cobaltate, for example, 742 ℃ or higher and 950 ℃ or lower, and the additive element such as magnesium can be distributed in the surface layer portion, whereby a positive electrode active material having excellent characteristics can be produced.

However, liF has a lighter specific gravity in the gaseous state than oxygen, so that LiF may volatilize or sublimate by heating LiF, and LiF in the mixture 903 decreases when volatilization occurs. At this time, the function of LiF as a flux is reduced. Therefore, it is preferable to perform heating while suppressing volatilization of LiF. In addition, even if LiF is not used as a fluorine source or the like, li on the surface of LiCoO ₂ may react with F as a fluorine source to generate LiF and volatilize. Thus, even if a fluoride having a higher melting point than LiF is used, volatilization needs to be suppressed as well.

Then, it is preferable to heat the mixture 903 in an atmosphere containing LiF, that is, to heat the mixture 903 in a state where the partial pressure of LiF in the heating furnace is high. By the above heating, volatilization of LiF in the mixture 903 can be suppressed.

The heating in this step is preferably performed so as not to bond the particles of the mixture 903 together. When the particles of the mixture 903 adhere together during heating, the area where the particles contact oxygen in the atmosphere is reduced, and a path along which an additive element (for example, fluorine) diffuses is blocked, so that the additive element (for example, magnesium and fluorine) may not be easily distributed in the surface layer portion.

In addition, when the additive element (for example, fluorine) is uniformly distributed in the surface layer portion, a positive electrode active material that is smooth and has less irregularities can be obtained. Therefore, in order to maintain the state of the surface which has been heated in step S15 smooth or further smooth in this step, it is preferable not to adhere the particles of the mixture 903 together.

In the case of heating by a rotary kiln, it is preferable to control the flow rate of the oxygen-containing atmosphere in the kiln (kiln) for heating. For example, it is preferable that: reducing the flow rate of the oxygen-containing atmosphere; firstly purging the atmosphere, introducing oxygen atmosphere into the kiln, and then not flowing the atmosphere; etc. It is possible that the fluorine source is vaporized while the oxygen is flowing, which is not preferable in order to maintain the smoothness of the surface.

In the case of heating by means of a roller kiln, the mixture 903 can be heated under an LiF-containing atmosphere, for example by capping the container containing the mixture 903.

< Step S34>

Next, in step S34 shown in fig. 1A, the heated material is recovered, and if necessary, ground to obtain the positive electrode active material 100. In this case, the recovered positive electrode active material 100 is preferably also subjected to screening. Through the above steps, the positive electrode active material 100 (composite oxide) having a median particle diameter (D50) of 12 μm or less (preferably 10.5 μm or less, more preferably 8 μm or less) can be produced. The positive electrode active material 100 contains an additive element a.

< Method example 2 for producing Positive electrode active Material >

Another example of a method for producing a positive electrode active material (example 2 of a method for producing a positive electrode active material) that can be used in one embodiment of the present invention will be described with reference to fig. 2 to 3. In example 2 of the method for producing a positive electrode active material, the number of times of adding the additive element and the mixing method are different from those in example 1 of the method for producing a positive electrode active material, but other descriptions can be referred to in example 1 of the method for producing a positive electrode active material.

In fig. 2, step S10 and step S15 are performed in the same manner as in fig. 1A, and initially heated lithium cobaltate is prepared. Note that step S15 is not an essential structure of one embodiment of the present invention, and a manner in which step S15 is omitted is also included in one embodiment of the present invention.

< Step S20a >

Next, as shown in step S20a, a first additive element A1 source (A1 source) is prepared. The details of step S20a are described with reference to fig. 3A.

< Step S21>

In step S21 shown in fig. 3A, a first additive element A1 source (A1 source) is prepared. The A1 source may be selected from the additive elements a described in step S21 shown in fig. 1C and used. For example, any one or more selected from magnesium, fluorine and calcium may be used as the additive element A1. Fig. 3A shows an example in which a magnesium source (Mg source) and a fluorine source (F source) are used as the additive element A1.

Steps S21 to S23 shown in fig. 3A can be performed by the same conditions as those of steps S21 to S23 shown in fig. 1C. As a result, the first additive element A1 source (A1 source) can be obtained in step S23.

In addition, in step S31 to step S33 shown in fig. 2, the same conditions as those in step S31 to step S33 shown in fig. 1A can be used.

< Step S34a >

Next, the material heated in step S33 is recovered to obtain lithium cobalt oxide containing the additive element A1. In order to distinguish it from the lithium cobaltate (first composite oxide) subjected to step S15, it is also referred to herein as a second composite oxide.

< Step S40>

In step S40 shown in fig. 2, a second additive element A2 source (A2 source) is prepared. Step S40 is described with reference to fig. 3B and 3C.

< Step S41>

In step S40 shown in fig. 3B, a second additive element A2 source (A2 source) is prepared. The A2 source may be selected from the additive elements a described in step S20 shown in fig. 1C and used. For example, any one or more selected from nickel, titanium, boron, zirconium, and aluminum may be suitably used as the additive element A2. Fig. 3B illustrates a case where a nickel source and an aluminum source are used as the additive element A2.

Steps S41 to S43 shown in fig. 3B can be manufactured by the same conditions as those of steps S21 to S23 shown in fig. 1C. As a result, a second additive element A2 source (A2 source) can be obtained in step S43.

Steps S41 to S43 shown in fig. 3C are modified examples of fig. 3B. In step S41 shown in fig. 3C, a nickel source (Ni source) and an aluminum source (Al source) are prepared, and in step S42a, they are pulverized independently. As a result, a plurality of second additive element A2 sources (A2 sources) are prepared in step S43. Thus, the difference between the step S40 of fig. 3C and the step S40 of fig. 3B is that: the additive elements are crushed separately in step S42 a.

< Step S51 to step S53>

Next, steps S51 to S53 shown in fig. 2 can be manufactured under the same conditions as those of steps S31 to S33 shown in fig. 1A. The condition of step S53 of the heating step is preferably a lower temperature and/or a shorter time than step S33 shown in fig. 2. Specifically, the heating temperature is preferably 800 ℃ to 950 ℃, more preferably 820 ℃ to 870 ℃, and still more preferably 850±10 ℃. The heating time is preferably 0.5 hours to 8 hours, more preferably 1 hour to 5 hours.

Note that, when nickel is selected as the second additive element A2, the mixing in step S51 is preferably performed so that the atomic number of nickel in the nickel source is 0.05% or more and 4% or less with respect to the atomic number of cobalt in the lithium cobaltate subjected to step S15. When aluminum is selected as the additive element A2, it is preferable to perform the mixing in step S51 so that the atomic number of aluminum in the aluminum source is 0.05% or more and 4% or less with respect to the atomic number of cobalt in the lithium cobaltate subjected to step S15.

< Step S54>

Next, in step S54 shown in fig. 2, the heated material is recovered and ground as needed, thereby obtaining the positive electrode active material 100. Through the above steps, the positive electrode active material 100 (composite oxide) having a median particle diameter (D50) of 12 μm or less (preferably 10.5 μm or less, more preferably 8 μm or less) can be produced. Or a positive electrode active material 100 that can be used in a lithium ion battery having excellent discharge characteristics even in a low-temperature environment can be produced. The positive electrode active material 100 includes a first additive element A1 and a second additive element A2.

In example 2 of the above-described production method, as shown in fig. 2 and 3, the additive elements are divided into a first additive element A1 and a second additive element A2, and the first additive element A1 and the second additive element A2 are introduced into lithium cobaltate, respectively. By introducing the additive elements separately, the distribution of each additive element in the depth direction can be changed. For example, the first additive element may be distributed so that the concentration in the surface layer portion is higher than that in the interior, and the second additive element may be distributed so that the concentration in the interior is higher than that in the surface layer portion. The positive electrode active material 100 manufactured by the steps of fig. 1A and 1D can be manufactured at low cost because a plurality of additive elements a are added at one time. On the other hand, the positive electrode active material 100 manufactured by fig. 2 and 3 is preferable because a plurality of additive elements a are added in a plurality of steps, so that the manufacturing cost is relatively high, but the distribution of each additive element a in the depth direction can be controlled more precisely.

(Embodiment 2)

[ Lithium ion Battery ]

A lithium ion battery that can be manufactured as one embodiment of the present invention includes a positive electrode, a negative electrode, and an electrolyte. In addition, when the electrolyte contains an electrolyte solution, a separator is included between the positive electrode and the negative electrode. The battery may further include an exterior body covering at least a part of the periphery of the positive electrode, the negative electrode, and the electrolyte.

In the present embodiment, a description will be given focusing on a structure of a lithium ion battery in order to realize a lithium ion battery having good discharge characteristics even in a low-temperature environment (for example, 0 ℃ or lower, -20 ℃ or lower, preferably-30 ℃ or lower, more preferably-40 ℃ or lower, still more preferably-50 ℃ or lower, and most preferably-60 ℃ or lower) and/or a lithium ion battery having good charge characteristics even in a low-temperature environment. Specifically, the positive electrode active material and the electrolyte included in the positive electrode will be described centering on the following. Details of the structure other than the positive electrode active material and the electrolyte included in the lithium ion battery will be described in embodiment 3.

[ Positive electrode ]

The positive electrode includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, and may further contain at least one of a conductive material and a binder.

< Cathode active Material >

The positive electrode active material has a function of extracting lithium ions and/or releasing lithium ions in accordance with charge and discharge. As the positive electrode active material used in one embodiment of the present invention, a material having little degradation (or a material having little increase in resistance) due to charge and/or discharge in a low-temperature environment (hereinafter also referred to as "charge and discharge") can be used even at a high charge voltage (hereinafter also referred to as "high charge voltage"). Specifically, a positive electrode active material (composite oxide) having a particle diameter (specifically, a median particle diameter (D50)) of 12 μm or less (preferably 10.5 μm or less, more preferably 8 μm or less) obtained by the production method described in embodiment 1 can be used. The positive electrode active material contains an additive element a or a first additive element A1 and a second additive element A2.

When the positive electrode active material is too small, coating at the time of manufacturing the positive electrode may not be easily performed. In addition, when the positive electrode active material is too small, the surface area is too large, which may cause excessive reaction of the surface of the positive electrode active material with the electrolyte. Or when the particle diameter of the positive electrode active material is too small, a large amount of conductive material serving as a conductive path between particles needs to be mixed, which may cause a decrease in capacity. Therefore, the particle diameter (median diameter (D50)) of the positive electrode active material is preferably 1 μm or more.

In the present specification and the like, unless otherwise specified, the "charge voltage" is represented by the potential of lithium metal as a reference. In the present specification and the like, the "high charging voltage" means, for example, a charging voltage of 4.6V or more, preferably 4.65V or more, more preferably 4.7V or more, still more preferably 4.75V or more, and most preferably 4.8V or more. Further, as long as the positive electrode active material is a material which undergoes little degradation due to charge and discharge even when a high charge voltage is used, two or more materials having different particle diameters and/or compositions may be used. In this specification and the like, "composition is different" includes not only the case where the structures of elements included in a material are different but also the case where the proportions of the included elements are different although the structures of the elements included in the material are the same.

Note that, as described above, in the present specification and the like, the "high charge voltage" refers to a potential of 4.6V or more when the negative electrode is based on lithium metal, but the potential of 4.5V or more when the negative electrode is a carbon material (for example, graphite) is referred to as "high charge voltage". Specifically, in the case of a half cell using lithium metal as the negative electrode, a charging voltage of 4.6V or more is referred to as a high charging voltage, and in the case of a full cell using a carbon material (e.g., graphite) as the negative electrode, a charging voltage of 4.5V or more is referred to as a high charging voltage.

Even at a high charge voltage, a lithium ion battery having a large discharge capacity even at a low temperature environment (for example, 0 ℃, -20 ℃, preferably-30 ℃, more preferably-40 ℃, still more preferably-50 ℃, and most preferably-60 ℃) can be realized by using a material with little deterioration of charge and discharge (or a material with little increase in resistance) as the positive electrode active material. In addition, a lithium ion battery in which the discharge capacity at low temperature (for example, 0 ℃, -20 ℃, preferably-30 ℃, more preferably-40 ℃, further preferably-50 ℃, and most preferably-60 ℃) is 50% or more (preferably 60% or more, more preferably 70% or more, further preferably 80% or more, and most preferably 90% or more) than the discharge capacity at 25 ℃ can be realized. Note that the value of the discharge capacity in the low-temperature environment is the same as the measurement condition of the value of the discharge capacity at 25 ℃ except for the temperature at the time of discharge (hereinafter, sometimes referred to as "discharge temperature" in this specification or the like).

In addition, a lithium ion battery having a large discharge energy density in a low-temperature environment (for example, 0 ℃, -20 ℃, preferably-30 ℃, more preferably-40 ℃, still more preferably-50 ℃, and most preferably-60 ℃) can be realized. In addition, a lithium ion battery having a discharge energy density at a low temperature environment (for example, 0 ℃, -20 ℃, preferably-30 ℃, more preferably-40 ℃, further preferably-50 ℃, and most preferably-60 ℃) of 50% or more (preferably 60% or more, more preferably 70% or more, further preferably 80% or more, and most preferably 90% or more) than a discharge energy density at 25 ℃ can be realized. The discharge energy density in the low-temperature environment was measured under the same conditions as the discharge energy density at 25 ℃ except for the temperature at the time of discharge.

The temperature at the time of charge or discharge described in the present specification or the like means the temperature of the lithium ion battery. In the measurement of battery characteristics at various temperatures, for example, the measurement may be performed as follows: after a battery to be measured (for example, a test battery or a half battery) is set in the constant temperature tank, measurement is started after a sufficient time (for example, 1 hour or more) elapses until the temperature of the test battery becomes the same as the temperature of the constant temperature tank.

< Electrolyte >

The electrolyte used in one embodiment of the present invention may be a material having excellent charge and/or discharge (charge-discharge) lithium ion conductivity even in a low-temperature environment (for example, 0 ℃ and-20 ℃, preferably-30 ℃, more preferably-40 ℃, still more preferably-50 ℃, and most preferably-60 ℃).

An example of the electrolyte is described below. Note that the electrolyte described in this embodiment mode is an electrolyte in which a lithium salt is dissolved in an organic solvent, and may be referred to as an electrolyte. The electrolyte is not limited to a liquid electrolyte (electrolyte solution) that is liquid at normal temperature, and a solid electrolyte may be used. Alternatively, an electrolyte (semi-solid electrolyte) including both a liquid electrolyte that is liquid at ordinary temperature and a solid electrolyte that is solid at ordinary temperature may be used.

As an example, the organic solvent described in this embodiment includes Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC), and when the total content of the ethylene carbonate, the ethylmethyl carbonate and the dimethyl carbonate is 100vol%, the volume ratio of the ethylene carbonate, the ethylmethyl carbonate and the dimethyl carbonate is x: y:100-x-y (note that 5.ltoreq.x.ltoreq.35 and 0< y < 65). More specifically, the following EC: EMC: dmc=30: 35:35 (volume ratio) organic solvents including EC, EMC and DMC. Note that the volume ratio may be a volume ratio before mixing the organic solvent, or the external air may be room temperature (typically 25 ℃) when the organic solvent is mixed.

EC is a cyclic carbonate, and has an effect of promoting dissociation of lithium salt because of its high relative dielectric constant. On the other hand, EC has a high viscosity and a high freezing point (melting point) of 38 ℃, and thus it is difficult to use it in a low temperature environment when only EC is used as an organic solvent. Thus, the organic solvent specifically described as one embodiment of the present invention includes not only EC but also EMC and DMC. EMC is a chain carbonate, has an effect of reducing the viscosity of the electrolyte, and has a freezing point of-54 ℃. DMC was also a chain carbonate, and had an effect of reducing the viscosity of the electrolyte, and the freezing point was-43 ℃. The total content of three organic solvents, namely EC, EMC and DMC, having the physical properties is 100vol% and the volume ratio is x: y:100-x-y (note that x is 5.ltoreq.x is 35 and 0< y < 65), and an electrolyte prepared by using the above organic solvent has a characteristic of having a freezing point of-40 ℃ or lower.

Since a general electrolyte used in a lithium ion battery is solidified at about-20 ℃, it is difficult to manufacture a battery that can be charged and discharged at-40 ℃. The electrolyte described as an example in this embodiment has a freezing point of-40 ℃ or lower, and thus a lithium ion battery that can be charged and discharged even in an extremely low-temperature environment of-40 ℃ can be realized.

As the lithium salt dissolved in the solvent, for example, at least one of LiPF₆、LiClO₄、LiAsF₆、LiBF₄、LiAlCl₄、LiSCN、LiBr、LiI、Li₂SO₄、Li₂B₁₀Cl₁₀、Li₂B₁₂Cl₁₂、LiCF₃SO₃、LiC₄F₉SO₃、LiC(CF₃SO₂)₃、LiC(C₂F₅SO₂)₃、LiN(CF₃SO₂)₂、LiN(C₄F₉SO₂)(CF₃SO₂)、LiN(C₂F₅SO₂)₂ and lithium bis (oxalato) borate (LiBOB) may be used in any combination and ratio.

In addition, as the electrolyte, it is preferable to use granular dust or elements other than constituent elements of the electrolyte (hereinafter, simply referred to as "impurities") in a small amount and highly purified. Specifically, the ratio of the impurity to the weight of the electrolyte is preferably 1% or less, more preferably 0.1% or less, and still more preferably 0.01% or less.

In addition, a coating film (Solid Electrolyte Interphase (solid electrolyte interface)) may be formed at the interface between the electrode (active material layer) and the electrolyte for the purpose of improving safety or the like, and an additive of Vinylene Carbonate (VC), propane Sultone (PS), t-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis (oxalato) borate (LiBOB), or a dinitrile compound of succinonitrile or adiponitrile may be added to the electrolyte. For example, the concentration of the additive may be set to 0.1wt% or more and 5wt% or less of the organic solvent.

An example of an electrolyte that can be used in the lithium ion battery of one embodiment of the present invention is described above, but the electrolyte that can be used in the lithium ion battery of one embodiment of the present invention is not limited to this example. Other materials may be used as long as they have excellent lithium ion conductivity even when charged and discharged in a low-temperature environment.

Since the lithium ion battery according to one embodiment of the present invention includes at least the positive electrode active material and the electrolyte, it is possible to realize a lithium ion battery having good discharge characteristics even in a low-temperature environment and/or a lithium ion battery having good charge characteristics even in a low-temperature environment. More specifically, when the lithium metal is used as the negative electrode and at least the positive electrode active material and the electrolyte are contained in the test battery, a lithium ion battery can be realized in which the test battery is charged at a constant current at a charge rate of 0.1C or 0.2C (note that 1c=200 mA/g) until a voltage of 4.6V is reached in a 25 ℃ environment, and then is discharged at a constant current at a discharge rate of 0.1C until a voltage of 2.5V is reached in a-40 ℃ environment, and the obtained discharge capacity has a value of 50% or more compared with the value of the discharge capacity obtained by the step of charging the test battery at a constant current at a charge rate of 0.1C or 0.2C (note that 1c=200 mA/g is reached in a 25 ℃ environment) until a voltage of 2.5V is reached, and in which the battery can realize a discharge capacity of 50% or more in an operating environment where the discharge capacity is reached at a temperature of 25 ℃ or less than any temperature of 25 ℃.

The content of this embodiment can be freely combined with the content of other embodiments.

Embodiment 3

In this embodiment, elements constituting a lithium ion battery will be described.

[ Positive electrode ]

The positive electrode includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, and may further contain at least one of a conductive material and a binder. The positive electrode active material described in embodiment 1 can also be used.

Fig. 4A shows an example of a schematic cross-section of the positive electrode.

For example, a metal foil may be used for the current collector 550. The positive electrode may be formed by coating a slurry on a metal foil and drying. In addition, pressing may be performed after drying. In the positive electrode, an active material layer is formed on the current collector 550.

The slurry is a material liquid for forming an active material layer on the current collector 550, and contains an active material, a binder, and a solvent, and preferably, a conductive material is mixed. The slurry is also referred to as an electrode slurry or an active material slurry, and is sometimes used for forming a positive electrode active material layer, and is sometimes referred to as a negative electrode slurry when forming a negative electrode active material layer.

The positive electrode active material 561 has a function of absorbing lithium ions and/or releasing lithium ions in accordance with charge and discharge. As the positive electrode active material 561 used in one embodiment of the present invention, a material that undergoes little degradation due to charge and discharge even when a high charge voltage is used. In the present specification and the like, unless otherwise specified, the charging voltage is represented by the potential of lithium metal as a reference. In the present specification, the high charging voltage refers to a charging voltage of, for example, 4.6V or more, preferably 4.65V or more, more preferably 4.7V or more, still more preferably 4.75V or more, and most preferably 4.8V or more.

As the positive electrode active material 561 used in one embodiment of the present invention, any material can be used as long as it is a material that undergoes little degradation due to charge and discharge even when a high charge voltage is used, and the materials described in embodiment mode 1 or embodiment mode 2 can be used. Further, as the positive electrode active material 561, two or more materials having different particle diameters may be used as long as the degradation accompanying charge and discharge is small even when a high charge voltage is used.

The conductive material is also called a conductivity imparting agent or a conductivity assistant, and a carbon material can be used in many cases. By attaching the conductive material between the plurality of active materials, the plurality of active materials are electrically connected to each other, and conductivity is improved. Note that in this specification and the like, "adhesion" does not mean that an active material is physically in close contact with a conductive material but means a concept including: in the case of covalent bonds; bonding by van der waals forces; a case where the conductive material covers a part of the surface of the active material; a case where the conductive material is embedded in the surface irregularities of the active material; and the like, which are not in contact with each other but are electrically connected.

Specific examples of the carbon material that can be used as the conductive material include carbon black (furnace black, acetylene black, graphite, and the like).

Fig. 4A shows carbon black 553 as an example of a conductive material and an electrolyte 571 contained in a space portion located between positive electrode active materials 561. .

In order to fix the current collector 550 and the active material such as a metal foil, a binder (resin) may be mixed with the positive electrode of the secondary battery. Adhesives are also known as binders. When a large amount of the binder is contained, the ratio of the active material in the positive electrode decreases, and the discharge capacity of the secondary battery decreases. Therefore, it is preferable to mix the amount of the binder to the minimum. In fig. 4A, the region not filled with the positive electrode active material 561, the second positive electrode active material 562, and the carbon black 553 is referred to as a void or a binder.

Fig. 4A shows an example in which the shape of the positive electrode active material 561 is spherical, but the shape is not particularly limited. The cross-sectional shape of the positive electrode active material 561 may be, for example, elliptical, rectangular, trapezoidal, tapered, or polygonal or asymmetric with a corner portion having a curved shape. For example, fig. 4B shows an example in which the positive electrode active material 561 has a polygonal shape with corners in an arc shape.

In the positive electrode of fig. 4B, graphene 554 is used as a carbon material used as a conductive material. In fig. 4B, a positive electrode active material layer including a positive electrode active material 561, graphene 554, and carbon black 553 is formed on a current collector 550.

Note that in the step of mixing the graphene 554 and the carbon black 553 to obtain an electrode slurry, the weight of the mixed carbon black is preferably 1.5 times or more and 20 times or less, and more preferably 2 times or more and 9.5 times or less, of that of the graphene.

When the mixing ratio of the graphene 554 and the carbon black 553 is set within the above range, the dispersion stability of the carbon black 553 is excellent and the aggregation is not likely to occur when the slurry is adjusted. Further, in the case where the mixture of the graphene 554 and the carbon black 553 is set within the above range, a high electrode density can be achieved as compared with a positive electrode in which only the carbon black 553 is used for the conductive material. By increasing the electrode density, the capacity per unit weight can be increased. Specifically, the density of the positive electrode active material layer measured by weight may be 3.5g/cc or more.

The electrode density is low compared to a positive electrode using only graphene for a conductive material, but the mixture of the first carbon material (graphene) and the second carbon material (acetylene black) is in the above-described range, whereby the corresponding rapid charge can be achieved. Therefore, this is particularly effective when used for an in-vehicle secondary battery.

Fig. 4C shows an example in which carbon fiber 555 is used instead of the positive electrode of graphene. Fig. 4C shows an example different from fig. 4B. By using the carbon fiber 555, aggregation of the carbon black 553 can be prevented, and dispersibility can be improved.

Note that in fig. 4C, the region not filled with the positive electrode active material 561, the carbon fiber 555, and the carbon black 553 refers to a void or a binder.

Fig. 4D shows examples of other positive electrodes. Fig. 4C shows an example in which carbon fiber 555 is used instead of graphene 554. By using the graphene 554 and the carbon fiber 555, aggregation of carbon black such as the carbon black 553 can be prevented, and therefore dispersibility can be improved.

Note that in fig. 4D, the region not filled with the positive electrode active material 561, the carbon fiber 555, the graphene 554, and the carbon black 553 is referred to as a void or a binder.

The secondary battery may be manufactured by: a separator is stacked on the positive electrode using any one of the positive electrodes in fig. 4A to 4D, and a stacked body in which a negative electrode is stacked on the separator is placed in a container (outer package, metal can, or the like) or the like, and the container is filled with an electrolyte.

< Adhesive >

As the binder, for example, a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber (styrene-isoprene-styrene rubber), acrylonitrile-butadiene rubber (butadiene rubber), or ethylene-propylene-diene copolymer (ethylene-propylene copolymer) is preferably used. Fluororubbers may also be used as binders.

In addition, for example, a water-soluble polymer is preferably used as the binder. As the water-soluble polymer, for example, polysaccharides and the like can be used. As the polysaccharide, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, regenerated cellulose, and the like, starch, and the like can be used. More preferably, these water-soluble polymers are used in combination with the rubber material.

Or as the binder, polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, nitrocellulose, and the like are preferably used.

As the binder, a plurality of the above materials may be used in combination.

For example, a material having a particularly good viscosity adjusting effect may be used in combination with other materials. For example, although rubber materials and the like have high adhesion and high elasticity, it is sometimes difficult to adjust viscosity when mixed in a solvent. In such a case, for example, it is preferable to mix with a material having a particularly good viscosity adjusting effect. As a material having a particularly good viscosity adjusting effect, for example, a water-soluble polymer can be used. The water-soluble polymer having a particularly good viscosity adjusting function may be the polysaccharide, and for example, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, or starch may be used.

Note that cellulose derivatives such as carboxymethyl cellulose are converted into salts such as sodium salts and ammonium salts of carboxymethyl cellulose, for example, to improve solubility, and thus can easily exhibit the effect as viscosity modifiers. The higher solubility can improve the dispersibility of the active material or other components in the electrode-forming slurry. In this specification and the like, cellulose and cellulose derivatives used as binders for electrodes include salts thereof.

The active material and other materials used as a binder composition, for example, styrene-butadiene rubber, can be stably dispersed in an aqueous solution by dissolving a water-soluble polymer in water to stabilize the viscosity. Since the water-soluble polymer has a functional group, it is expected to be easily and stably attached to the surface of the active material. Cellulose derivatives such as carboxymethyl cellulose often have functional groups such as hydroxyl groups and carboxyl groups, and thus, the polymers are expected to interact with each other to widely cover the surface of the active material.

When the binder forming film covers or contacts the surface of the active material, the binder forming film is also expected to be used as a passive film to exert an effect of suppressing decomposition of the electrolyte. The "passive film" is a film having no conductivity or extremely low conductivity, and for example, when the passive film is formed on the surface of the active material, decomposition of the electrolyte at the cell reaction potential is suppressed. More preferably, the passive film is capable of transporting lithium ions while inhibiting conductivity.

< Positive electrode collector >

As the positive electrode current collector, a metal such as stainless steel, gold, platinum, aluminum, titanium, or an alloy thereof, or a material having high conductivity can be used. In addition, the material for the positive electrode current collector is preferably not eluted by the potential of the positive electrode. Further, an aluminum alloy to which an element for improving heat resistance such as silicon, titanium, neodymium, scandium, or molybdenum is added may be used. In addition, a metal element that reacts with silicon to form silicide may also be used. As metal elements that react with silicon to form silicide, there are zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, and the like. The positive electrode current collector may be suitably in the form of a foil, a plate, a sheet, a net, a punched metal net, a drawn metal net, or the like. The thickness of the positive electrode current collector is preferably 5 μm or more and 30 μm or less.

[ Negative electrode ]

The anode includes an anode active material layer and an anode current collector. In addition, the anode active material layer may contain an anode active material and further include a conductive material and a binder.

< Negative electrode active Material >

As the negative electrode active material, for example, an alloy material, a carbon material, or the like can be used.

As the negative electrode active material, an element that can undergo a charge-discharge reaction by an alloying/dealloying reaction with lithium can be used. For example, a material containing at least one selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, and the like can be used. The capacity of this element is higher than that of carbon, especially that of silicon, and is 4200mAh/g. Therefore, silicon is preferably used for the anode active material. In addition, compounds containing these elements may also be used. For example, SiO、Mg₂Si、Mg₂Ge、SnO、SnO₂、Mg₂Sn、SnS₂、V₂Sn₃、FeSn₂、CoSn₂、Ni₃Sn₂、Cu₆Sn₅、Ag₃Sn、Ag₃Sb、Ni₂MnSb、CeSb₃、LaSn₃、La₃Co₂Sn₇、CoSb₃、InSb, sbSn, and the like are mentioned. Here, an element that can undergo a charge-discharge reaction by an alloying/dealloying reaction with lithium, a compound containing the element, or the like is sometimes referred to as an alloy-based material.

In the present specification and the like, "SiO" refers to silicon monoxide, for example. Or SiO may also be referred to as SiO _x. Here, x preferably represents 1 or a value around 1. For example, x is preferably 0.2 to 1.5, more preferably 0.3 to 1.2.

As the carbon material, graphite, easily graphitizable carbon (soft carbon), hard graphitizable carbon (hard carbon), carbon fiber (carbon nanotube), graphene, carbon black, or the like can be used.

Examples of the graphite include artificial graphite and natural graphite. Examples of the artificial graphite include Mesophase Carbon Microspheres (MCMB), coke-based artificial graphite (pitch-based ARTIFICIAL GRAPHITE), pitch-based artificial graphite (pitch-based ARTIFICIAL GRAPHITE), and the like. Here, as the artificial graphite, spherical graphite having a spherical shape may be used. For example, MCMB is sometimes of spherical shape, so is preferred. In addition, MCMB is relatively easy to reduce its surface area, so it is sometimes preferable. Examples of the natural graphite include scaly graphite and spheroidized natural graphite.

When lithium ions are intercalated into graphite (at the time of formation of lithium-graphite intercalation compound), graphite shows a low potential (0.05V or more and 0.3V or less vs. Li/Li ⁺) to the same extent as lithium metal. Thus, lithium ion batteries using graphite can show high operating voltages. Graphite also has the following advantages: the capacity per unit volume is large; the volume expansion is smaller; less expensive; safety higher than lithium metal is preferable.

Further, as the anode active material, an oxide such as titanium oxide (TiO ₂), lithium titanium oxide (Li ₄Ti₅O₁₂), lithium-graphite interlayer compound (Li _xC₆), niobium pentoxide (Nb ₂O₅), tungsten dioxide (WO ₂), molybdenum dioxide (MoO ₂), or the like can be used.

Further, as the anode active material, li _3-xM_x N (m=co, ni, cu) having a Li ₃ N type structure including a nitride of lithium and a transition metal may be used. For example, li _2.6Co_0.4N₃ shows a large charge-discharge capacity (900 mAh/g,1890mAh/cm ³) and is therefore preferable.

When a nitride containing lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, and thus can be combined with a material containing no lithium ions such as V ₂O₅、Cr₃O₈ used as the positive electrode active material, which is preferable. Note that when a material containing lithium ions is used as the positive electrode active material, a nitride containing lithium and a transition metal can also be used as the negative electrode active material by previously removing lithium ions contained in the positive electrode active material.

In addition, a material that causes a conversion reaction may be used for the anode active material. For example, a transition metal oxide such as cobalt oxide (CoO), nickel oxide (NiO), or iron oxide (FeO) that does not form an alloy with lithium is used for the negative electrode active material. Examples of the material that causes the conversion reaction include oxides such as Fe ₂O₃、CuO、Cu₂O、RuO₂、Cr₂O₃, sulfides such as CoS _0.89, niS and CuS, nitrides such as Zn ₃N₂、Cu₃N、Ge₃N₄, phosphides such as NiP ₂、FeP₂、CoP₃, and fluorine compounds such as FeF ₃、BiF₃.

As the conductive material and the binder that can be contained in the negative electrode active material layer, the same materials as the conductive material and the binder that can be contained in the positive electrode active material layer can be used.

< Negative electrode Current collector >

As the negative electrode current collector, copper foil, or the like may be used in addition to the same material as the positive electrode current collector. As the negative electrode current collector, a material that is not ionically alloyed with a carrier such as lithium is preferably used.

[ Electrolyte ]

As the electrolyte, the film described in embodiment mode 1 can be suitably used.

[ Spacer ]

When the electrolyte contains an electrolyte solution, a separator is disposed between the positive electrode and the negative electrode. As the separator, for example, the following materials can be used: the material is formed of a fiber having cellulose such as paper, a nonwoven fabric, a glass fiber, a ceramic, a synthetic fiber using nylon (polyamide), vinylon (polyvinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane, or the like. The separator is preferably processed into a bag shape and disposed so as to surround either the positive electrode or the negative electrode.

The separator may have a multi-layered structure. For example, a ceramic material, a fluorine material, a polyamide material, or a mixture thereof may be coated on a film of an organic material such as polypropylene or polyethylene. As the ceramic material, for example, alumina particles, silica particles, or the like can be used. As the fluorine-based material, PVDF, polytetrafluoroethylene, or the like can be used, for example. As the polyamide-based material, nylon, aromatic polyamide (meta-aromatic polyamide, para-aromatic polyamide) and the like can be used, for example.

The oxidation resistance is improved by coating the ceramic material, whereby deterioration of the separator during high-voltage charge and discharge can be suppressed, and the reliability of the secondary battery can be improved. The fluorine-based material is applied to facilitate the adhesion of the separator to the electrode, thereby improving the output characteristics. The improvement of heat resistance by coating a polyamide-based material (especially, an aromatic polyamide) improves the safety of the secondary battery.

For example, a mixture of alumina and aramid may be applied to both sides of the polypropylene film. Alternatively, a mixed material of alumina and aramid may be applied to the surface of the polypropylene film that contacts the positive electrode, and a fluorine-based material may be applied to the surface that contacts the negative electrode.

By adopting the separator of the multilayer structure, the safety of the secondary battery can be ensured even if the total thickness of the separator is small, and therefore the capacity per unit volume of the secondary battery can be increased.

[ Outer packaging body ]

As the exterior body included in the secondary battery, for example, a metal material such as aluminum or a resin material can be used. In addition, a film-shaped outer package may be used. As the film, for example, a film having the following three-layer structure can be used: a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide is provided with a metal thin film having excellent flexibility such as aluminum, stainless steel, copper, or nickel, and an insulating synthetic resin film such as polyamide resin or polyester resin may be provided as an outer surface of the exterior body.

Embodiment 4

In this embodiment, an example of the shape of a secondary battery including a positive electrode manufactured by the manufacturing method described in the above embodiment will be described.

[ Coin-type Secondary Battery ]

An example of a coin-type secondary battery will be described. Fig. 5A is an exploded perspective view of a coin-type (single-layer flat-type) secondary battery, fig. 5B is an external view thereof, and fig. 5C is a sectional view thereof. Coin-type secondary batteries are mainly used for small-sized electronic devices.

Fig. 5A is a schematic view for easy understanding of the overlapping relationship (up-down relationship and positional relationship) of the members. Thus, fig. 5A is not a diagram exactly identical to fig. 5B.

In fig. 5A, a positive electrode 304, a separator 310, a negative electrode 307, a separator 322, and a gasket 312 are stacked. The negative electrode can 302 and the positive electrode can 301 are sealed. Note that a gasket for sealing is not shown in fig. 5A. The spacer 322 and the gasket 312 are used to protect the inside or fix the position in the can when the positive electrode can 301 and the negative electrode can 302 are pressed together. Stainless steel or insulating material is used for the spacer 322 and the gasket 312.

The stacked-layer structure in which the positive electrode active material layer 306 is formed on the positive electrode current collector 305 is referred to as a positive electrode 304.

In order to prevent the short circuit between the positive electrode and the negative electrode, the separator 310 and the annular insulator 313 are disposed so as to cover the side surfaces and the top surface of the positive electrode 304. The area of the separator 310 is larger than the area of the positive electrode 304.

Fig. 5B is a perspective view of the fabricated coin-type secondary battery.

In the coin-type secondary battery 300, a positive electrode can 301 that doubles as a positive electrode terminal and a negative electrode can 302 that doubles as a negative electrode terminal are insulated and sealed by a gasket 303 formed using polypropylene or the like. The positive electrode 304 is formed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. In addition, the anode 307 is formed of an anode current collector 308 and an anode active material layer 309 provided in contact therewith. The negative electrode 307 is not limited to a stacked structure, and a lithium metal foil or an alloy foil of lithium and aluminum may be used.

In the positive electrode 304 and the negative electrode 307 for the coin-type secondary battery 300, active material layers may be formed on one surface of the positive electrode and the negative electrode, respectively.

As the positive electrode can 301 and the negative electrode can 302, metals having corrosion resistance to the electrolyte, such as nickel, aluminum, and titanium, alloys thereof, and alloys thereof with other metals (for example, stainless steel) can be used. In order to prevent corrosion due to the electrolyte solution or the like, the positive electrode can 301 and the negative electrode can 302 are preferably covered with nickel, aluminum, or the like. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

By impregnating these negative electrode 307, positive electrode 304, and separator 310 with an electrolyte, as shown in fig. 5C, positive electrode can 301 is placed below, positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order, and positive electrode can 301 and negative electrode can 302 are pressed together with gasket 303 interposed therebetween, to produce coin-type secondary battery 300.

By adopting the above-described structure, the coin-type secondary battery 300 having a high capacity, a high discharge capacity, and good cycle characteristics can be manufactured.

[ Cylindrical secondary cell ]

Next, an example of a cylindrical secondary battery will be described with reference to fig. 6A. As shown in fig. 6A, the top surface of the cylindrical secondary battery 616 includes a positive electrode cap (battery cap) 601, and the side and bottom surfaces thereof include a battery can (outer can) 602. The positive electrode cover 601 is insulated from the battery can (outer can) 602 by a gasket (insulating gasket) 610.

Fig. 6B is a view schematically showing a cross section of a cylindrical secondary battery. The cylindrical secondary battery shown in fig. 6B has a positive electrode cap (battery cap) 601 on the top surface, and battery cans (outer cans) 602 on the side surfaces and the bottom surface. The positive electrode cover 601 is insulated from the battery can (outer can) 602 by a gasket (insulating gasket) 610.

A battery element in which a band-shaped positive electrode 604 and a band-shaped negative electrode 606 are wound with a separator 605 interposed therebetween is provided inside a hollow cylindrical battery can 602. Although not shown, the battery element is wound around the center axis. One end of the battery can 602 is closed and the other end is open. As the battery can 602, metals having corrosion resistance to the electrolyte, such as nickel, aluminum, titanium, and the like, alloys thereof, and alloys thereof with other metals (e.g., stainless steel, and the like) can be used. In addition, in order to prevent corrosion by the electrolyte, the battery can 602 is preferably covered with nickel, aluminum, or the like. Inside the battery can 602, a battery element in which the positive electrode, the negative electrode, and the separator are wound is sandwiched between a pair of insulating plates 608 and 609 that face each other. A nonaqueous electrolyte (not shown) is injected into the battery can 602 in which the battery element is provided. As the nonaqueous electrolyte solution, the same electrolyte solution as that of the coin-type secondary battery can be used.

Since the positive electrode and the negative electrode for the cylindrical secondary battery are wound, the active material is preferably formed on both surfaces of the current collector.

By using the positive electrode active material 100 that can be obtained in embodiments 1,2, and the like for the positive electrode 604, a cylindrical secondary battery 616 with high capacity, high discharge capacity, and good cycle characteristics can be manufactured.

The positive electrode 604 is connected to a positive electrode terminal (positive electrode current collecting wire) 603, and the negative electrode 606 is connected to a negative electrode terminal (negative electrode current collecting wire) 607. As the positive electrode terminal 603 and the negative electrode terminal 607, a metal material such as aluminum can be used. The positive terminal 603 is resistance welded to the relief valve mechanism 613 and the negative terminal 607 is resistance welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cover 601 via a PTC (Positive Temperature Coefficient: positive temperature coefficient) element 611. When the internal pressure of the battery rises above a predetermined threshold value, the safety valve mechanism 613 cuts off the electrical connection between the positive electrode cover 601 and the positive electrode 604. In addition, the PTC element 611 is a thermosensitive resistor element whose resistance increases when the temperature rises, and limits the amount of current by the increase in resistance to prevent abnormal heat generation. As the PTC element, barium titanate (BaTiO ₃) semiconductor ceramics or the like can be used.

Fig. 6C shows an example of the power storage system 615. The power storage system 615 includes a plurality of secondary batteries 616. The positive electrodes of each secondary battery are in contact with the electrical conductor 624 separated by the insulator 625 and are electrically connected to each other. The conductor 624 is electrically connected to the control circuit 620 through a wiring 623. Further, the negative electrode of each secondary battery is electrically connected to the control circuit 620 through a wiring 626. As the control circuit 620, a charge/discharge control circuit that performs charge/discharge or the like, a protection circuit that prevents overcharge or/and overdischarge, or the like can be used.

Fig. 6D shows an example of the power storage system 615. The electric storage system 615 includes a plurality of secondary batteries 616, and the plurality of secondary batteries 616 are sandwiched between the conductive plate 628 and the conductive plate 614. The plurality of secondary batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 through the wiring 627. The plurality of secondary batteries 616 may be connected in parallel or in series, or may be connected in series after being connected in parallel. By constituting the power storage system 615 including the plurality of secondary batteries 616, large electric power can be obtained.

The plurality of secondary batteries 616 may be connected in parallel and then connected in series.

In addition, a temperature control device may be included between the plurality of secondary batteries 616. Can be cooled by the temperature control device when the secondary battery 616 is overheated, and can be heated by the temperature control device when the secondary battery 616 is supercooled. Therefore, the performance of the power storage system 615 is not easily affected by the outside air temperature.

In fig. 6D, the power storage system 615 is electrically connected to the control circuit 620 through the wiring 621 and the wiring 622. The wiring 621 is electrically connected to the positive electrodes of the plurality of secondary batteries 616 through the conductive plate 628, and the wiring 622 is electrically connected to the negative electrodes of the plurality of secondary batteries 616 through the conductive plate 614.

[ Other structural examples of Secondary Battery ]

A structural example of the secondary battery will be described with reference to fig. 7 and 8.

The secondary battery 913 shown in fig. 7A includes a wound body 950 provided with a terminal 951 and a terminal 952 inside a housing 930. The wound body 950 is impregnated with an electrolyte solution in the frame 930. The terminal 952 is in contact with the housing 930, and the insulating material prevents the terminal 951 from being in contact with the housing 930. Note that although the housing 930 is illustrated separately in fig. 7A for convenience, in reality, the wound body 950 is covered with the housing 930, and the terminals 951 and 952 extend outside the housing 930. As the housing 930, a metal material (for example, aluminum) or a resin material can be used.

As shown in fig. 7B, the frame 930 shown in fig. 7A may be formed using a plurality of materials. For example, in the secondary battery 913 shown in fig. 7B, a case 930a and a case 930B are bonded, and a winding body 950 is provided in a region surrounded by the case 930a and the case 930B.

As the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin for forming the surface of the antenna, shielding of an electric field due to the secondary battery 913 can be suppressed. In addition, if the electric field shielding by the housing 930a is small, an antenna may be provided inside the housing 930 a. As the frame 930b, for example, a metal material can be used.

Fig. 7C shows the structure of the winding body 950. The wound body 950 includes a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is formed by stacking the negative electrode 931 and the positive electrode 932 on each other with the separator 933 interposed therebetween to form a laminate sheet, and winding the laminate sheet. In addition, a plurality of stacks of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked.

In addition, a secondary battery 913 including a wound body 950a as shown in fig. 8 may be used. The wound body 950a shown in fig. 8A includes a negative electrode 931, a positive electrode 932, and a separator 933. The anode 931 includes an anode active material layer 931a. The positive electrode 932 includes a positive electrode active material layer 932a.

By using the positive electrode active material 100 which can be obtained in embodiments 1 and 2 for the positive electrode 932, a secondary battery 913 having a high capacity, a high discharge capacity, and good cycle characteristics can be manufactured.

The width of the separator 933 is larger than the anode active material layer 931a and the cathode active material layer 932a, and the separator 933 is wound so as to overlap the anode active material layer 931a and the cathode active material layer 932a. In addition, from the viewpoint of safety, the width of the anode active material layer 931a is preferably larger than that of the cathode active material layer 932a. The wound body 950a having the above-described shape is preferable because of good safety and productivity.

As shown in fig. 8B, the negative electrode 931 is electrically connected to the terminal 951 by ultrasonic bonding, soldering, or pressing. Terminal 951 is electrically connected to terminal 911 a. In addition, the positive electrode 932 is electrically connected to the terminal 952 by ultrasonic bonding, welding, or pressing. Terminal 952 is electrically connected to terminal 911 b.

As shown in fig. 8C, the wound body 950a and the electrolyte are covered with the case 930 to form the secondary battery 913. The housing 930 is preferably provided with a safety valve, an overcurrent protection element, and the like. The safety valve is a valve for preventing the inside of the battery rupture case 930 from being opened by a predetermined internal pressure.

As shown in fig. 8B, the secondary battery 913 may also include a plurality of windings 950a. By using a plurality of winding bodies 950a, the secondary battery 913 having a larger discharge capacity can be realized. For other components of the secondary battery 913 shown in fig. 8A and 8B, reference may be made to the description of the secondary battery 913 shown in fig. 7A to 7C.

< Laminated Secondary Battery >

Next, fig. 9A and 9B are external views showing an example of a laminated secondary battery. Fig. 9A and 9B each show the positive electrode 503, the negative electrode 506, the separator 507, the exterior body 509, the positive electrode lead electrode 510, and the negative electrode lead electrode 511.

Fig. 10A is an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 includes a positive electrode current collector 501, and a positive electrode active material layer 502 is formed on a surface of the positive electrode current collector 501. The positive electrode 503 has a region (hereinafter, referred to as a tab region) where the positive electrode current collector 501 is partially exposed. The anode 506 includes an anode current collector 504, and an anode active material layer 505 is formed on a surface of the anode current collector 504. In addition, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, i.e., a tab region. The area or shape of the tab region of the positive electrode and the negative electrode is not limited to the example shown in fig. 10A.

< Method for producing laminated Secondary Battery >

Here, an example of a method of manufacturing a laminated secondary battery, the appearance of which is shown in fig. 9A, will be described with reference to fig. 10B and 10C.

First, the anode 506, the separator 507, and the cathode 503 are stacked. Fig. 10B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. The laminate may be a laminate composed of a negative electrode, a separator, and a positive electrode. Next, tab regions of the positive electrode 503 are bonded to each other, and the positive electrode lead electrode 510 is bonded to the tab region of the outermost positive electrode. As the bonding, for example, ultrasonic welding or the like can be used. In the same manner, the tab regions of the negative electrode 506 are joined to each other, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

Next, the negative electrode 506, the separator 507, and the positive electrode 503 are disposed on the exterior body 509.

Next, as shown in fig. 10C, the exterior body 509 is folded along a portion indicated by a broken line. Then, the outer peripheral portion of the outer package 509 is joined. As the bonding, for example, thermal compression bonding or the like can be used. In this case, a non-joined region (hereinafter, referred to as an inlet) is provided in a part (or one side) of the exterior body 509 for injecting the electrolyte later.

Next, the electrolyte is introduced into the exterior body 509 from an inlet provided in the exterior body 509. The electrolyte is preferably introduced under a reduced pressure atmosphere or an inert gas atmosphere. Finally, the introduction port is joined. Thus, the laminated secondary battery 500 can be manufactured.

By using the positive electrode active material 100 that can be obtained in embodiments 1, 2, and the like for the positive electrode 503, the secondary battery 500 that has high capacity, high discharge capacity, and good cycle characteristics can be manufactured.

[ Example of Battery pack ]

An example of a secondary battery pack according to an embodiment of the present invention that can be charged wirelessly by an antenna will be described with reference to fig. 11.

Fig. 11A is a diagram showing an external appearance of a secondary battery pack 531 having a rectangular parallelepiped shape (also referred to as a thicker flat plate shape) with a thin thickness. Fig. 11B is a diagram illustrating the structure of secondary battery pack 531. Secondary battery pack 531 includes a circuit board 540 and a secondary battery 513. The label 529 is attached to the secondary battery 513. The circuit board 540 is fixed by the sealing tape 515. In addition, secondary battery pack 531 includes an antenna 517.

The secondary battery 513 may have a structure including a wound body or a stacked body inside.

As shown in fig. 11B, in the secondary battery pack 531, a control circuit 590 is provided, for example, on the circuit board 540. In addition, the circuit board 540 is electrically connected to the terminal 514. The circuit board 540 is electrically connected to the antenna 517, one 551 of the positive electrode lead and the negative electrode lead of the secondary battery 513, and the other 552 of the positive electrode lead and the negative electrode lead.

As shown in fig. 11C, the circuit system 590a provided on the circuit board 540 and the circuit system 590b electrically connected to the circuit board 540 via the terminal 514 may be included.

The shape of the antenna 517 is not limited to a coil shape, and may be, for example, a linear shape or a plate shape. In addition, antennas such as a planar antenna, a caliber antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may be used. Alternatively, the antenna 517 may be a flat conductor. The flat plate-shaped conductor may also be used as one of the conductors for electric field coupling. In other words, the antenna 517 may be used as one of two conductors included in the capacitor. Thus, not only electromagnetic and magnetic fields but also electric fields can be used to exchange electric power.

Secondary battery pack 531 includes a layer 519 between antenna 517 and secondary battery 513. The layer 519 has a function of shielding an electromagnetic field from the secondary battery 513, for example. As the layer 519, for example, a magnetic substance can be used.

Embodiment 5

In this embodiment, an example different from the cylindrical secondary battery shown in fig. 6D will be described. Fig. 12C shows an example for an Electric Vehicle (EV).

The electric vehicle is provided with secondary battery first batteries 1301a and 1301b for main driving and a second battery 1311 for supplying electric power to an inverter 1312 for starting an engine 1304. The second battery 1311 is also called a cranking battery (also called a starting battery). The second battery 1311 is high-output, and does not need to have a high capacity. In addition, the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

The internal structure of the first battery 1301a may be a winding type as shown in fig. 7C or 8A, or a stacked type as shown in fig. 9A or 9B. The first battery 1301a may use the all-solid-state battery according to embodiment 6. By using the all-solid-state battery according to embodiment 6 as the first battery 1301a, high capacity can be achieved, safety can be improved, and downsizing and weight saving can be achieved.

In the present embodiment, the first batteries 1301a and 1301b are connected in parallel, but three or more batteries may be connected in parallel. Further, the first battery 1301b may not be provided as long as sufficient power can be stored in the first battery 1301 a. By constituting the battery pack from a plurality of secondary batteries, a large electric power can be taken out. The plurality of secondary batteries may be connected in parallel, or may be connected in series after being connected in parallel. A plurality of secondary batteries are sometimes referred to as a battery pack.

In order to cut off the power from the plurality of secondary batteries, the in-vehicle secondary battery includes a charging plug or a breaker that can cut off a high voltage without using a tool, and is provided to the first battery 1301a.

Further, the electric power of the first batteries 1301a, 1301b is mainly used to rotate the engine 1304, and electric power is also supplied to 42V-series vehicle-mounted components (the electric power steering system 1307, the heater 1308, the defogger 1309, and the like) through the DCDC circuit 1306. The first battery 1301a is used to rotate the rear engine 1317 in the case where the rear wheel includes the rear engine 1317.

Further, the second battery 1311 supplies electric power to 14V-series vehicle-mounted members (audio 1313, power window 1314, lamps 1315, and the like) through the DCDC circuit 1310.

Next, a first battery 1301a is described with reference to fig. 12A.

Fig. 12A shows an example in which nine corner secondary batteries 1300 are used as one battery pack 1415. Further, nine corner secondary batteries 1300 are connected in series, one electrode is fixed by a fixing portion 1413 made of an insulator, and the other electrode is fixed by a fixing portion 1414 made of an insulator. In the present embodiment, the fixing portions 1413 and 1414 are used for fixing, but the battery can be housed in a battery housing (also referred to as a casing). Since the vehicle is subjected to vibration, or the like from the outside (road surface or the like), it is preferable to fix a plurality of secondary batteries using the fixing portions 1413, 1414, the battery storage case, or the like. One electrode is electrically connected to the control circuit unit 1320 through a wiring 1421. The other electrode is electrically connected to the control circuit unit 1320 through a wiring 1422.

The control circuit 1320 may use a memory circuit including a transistor using an oxide semiconductor. A charge control circuit or a battery control system including a memory circuit using a transistor of an oxide semiconductor is sometimes referred to as BTOS (Battery operating system: battery operating system or Battery oxide semiconductor: battery oxide semiconductor).

It is preferable to use a metal oxide used as an oxide semiconductor. For example, a metal oxide such as In-M-Zn oxide (element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like) is preferably used as the oxide. In particular, the In-M-Zn oxide that can be applied to the oxide is preferably CAAC-OS (C-Axis ALIGNED CRYSTAL Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor). In addition, an in—ga oxide or an in—zn oxide may be used as the oxide. The CAAC-OS is an oxide semiconductor including a plurality of crystal regions, the c-axis of which is oriented in a specific direction. The specific direction refers to the thickness direction of the CAAC-OS film, the normal direction of the surface on which the CAAC-OS film is formed, or the normal direction of the surface of the CAAC-OS film. The crystallization region is a region having periodicity of atomic arrangement. Note that the crystal region is also a region in which lattice arrangements are uniform when the atomic arrangements are regarded as lattice arrangements.

The "CAC-OS" refers to a structure in which a material is divided into a first region and a second region, and the first region is mosaic-shaped and distributed in a film (hereinafter also referred to as cloud-shaped). That is, CAC-OS refers to a composite metal oxide having a structure in which the first region and the second region are mixed. Note that it is sometimes difficult to observe a clear boundary between the first region and the second region.

For example, in the CAC-OS of the In-Ga-Zn oxide, it was confirmed that the structure In which the region mainly composed of In (first region) and the region mainly composed of Ga (second region) were unevenly distributed and mixed was obtained from the EDX-map image obtained by the energy dispersive X-ray spectrometry (EDX: ENERGY DISPERSIVE X-ray spectroscopy).

In the case of using the CAC-OS for the transistor, the CAC-OS can be provided with a switching function (a function of controlling on/off) by a complementary effect of the conductivity due to the first region and the insulation due to the second region. In other words, the CAC-OS material has a conductive function in one part and an insulating function in the other part, and has a semiconductor function in the whole material. By separating the conductive function from the insulating function, each function can be improved to the maximum extent. Thus, by using CAC-OS for the transistor, high on-state current (I _on), high field-effect mobility (μ), and good switching operation can be achieved.

Oxide semiconductors have various structures and various characteristics. The oxide semiconductor according to one embodiment of the present invention may include two or more kinds of amorphous oxide semiconductor, polycrystalline oxide semiconductor, a-like OS, CAC-OS, nc-OS, and CAAC-OS.

Further, the control circuit portion 1320 preferably uses a transistor including an oxide semiconductor because the transistor can be used in a high-temperature environment. The control circuit 1320 may be formed using a unipolar transistor in order to simplify the process. The range of the operating ambient temperature of the transistor including the oxide semiconductor in the semiconductor layer is larger than that of the single crystal Si transistor, that is, is-40 ℃ or higher and 150 ℃ or lower, and the characteristic change when the secondary battery is overheated is smaller than that of the single crystal Si transistor. The off-state current of a transistor including an oxide semiconductor is equal to or lower than the measurement lower limit even at 150 ℃, but the temperature dependence of the off-state current characteristic of a single crystal Si transistor is large. For example, the off-state current of a single crystal Si transistor increases at 150 ℃, and the on-off ratio of the current does not become sufficiently large. The control circuit part 1320 can improve safety. In addition, by combining with a secondary battery in which the positive electrode active material 100 that can be obtained in embodiments 1,2, and the like is used for a positive electrode, a synergistic effect of safety can be obtained. The use of the positive electrode active material 100 obtained in embodiments 1,2, and the like in the secondary battery of the positive electrode and the control circuit unit 1320 greatly contribute to reduction of accidents such as fire disaster caused by the secondary battery.

The control circuit portion 1320 using a memory circuit including a transistor using an oxide semiconductor can also be used as an automatic control device for a secondary battery which is responsible for instability such as a micro short circuit. As a function for solving the cause of the instability of the secondary battery, there are exemplified prevention of overcharge, prevention of overcurrent, control of overheat during charging, cell balance in assembled battery, prevention of overdischarge, capacitance meter, automatic control of charging voltage and current amount according to temperature, control of charging current amount according to degree of deterioration, detection of abnormal behavior of micro short circuit, prediction of abnormality concerning micro short circuit, and the like, and the control circuit section 1320 has at least one of the functions described above. In addition, the automatic control device of the secondary battery can be miniaturized.

The term "micro short circuit" refers to a phenomenon in which a short circuit current slightly flows in a portion of a small short circuit, rather than a state in which charge and discharge cannot be performed due to a short circuit occurring between the positive electrode and the negative electrode of the secondary battery. Since a large voltage change occurs even in a short and extremely small portion, the abnormal voltage value affects the following estimation.

One of the causes of the occurrence of the micro short circuit is considered to be that the uneven distribution of the positive electrode active material occurs due to the charge and discharge performed a plurality of times, and the localized current concentration occurs in a part of the positive electrode and a part of the negative electrode, so that a part of the separator does not function, or the side reaction occurs due to the side reaction, resulting in the occurrence of the micro short circuit.

The control circuit unit 1320 detects the terminal voltage of the secondary battery in addition to the micro short circuit, and manages the charge/discharge state of the secondary battery. For example, both the output transistor of the charging circuit and the blocking switch may be turned off at substantially the same time to prevent overcharge.

Next, fig. 12B shows an example of a block diagram of the battery pack 1415 shown in fig. 12A.

The control circuit unit 1320 includes: a switching section 1324 including at least a switch for preventing overcharge and a switch for preventing overdischarge: a control circuit 1322 for controlling the switching unit 1324; and a voltage measurement unit of the first battery 1301 a. The control circuit 1320 sets the upper limit voltage and the lower limit voltage of the secondary battery to be used, and controls the upper limit of the current flowing from the outside, the upper limit of the output current flowing to the outside, and the like. The range of the secondary battery above the lower limit voltage and below the upper limit voltage is the recommended voltage range. The switching section 1324 functions as a protection circuit when the voltage is out of this range. The control circuit unit 1320 controls the switching unit 1324 to prevent overdischarge and/or overcharge, and thus may be referred to as a protection circuit. For example, when the control circuit 1322 detects a voltage that is to be overcharged, the switch of the switch unit 1324 is turned off to block the current. In addition, the function of shielding the current according to the temperature rise may be set by providing PTC elements in the charge/discharge paths. The control circuit unit 1320 includes an external terminal 1325 (+in) and an external terminal 1326 (-IN).

The switching section 1324 may be configured by combining an n-channel transistor or a p-channel transistor. In addition to a switch including a Si transistor using single crystal silicon, the switch portion 1324 may be configured using, for example, a power transistor such as Ge (germanium), siGe (silicon germanium), gaAs (gallium arsenide), gaAlAs (gallium aluminum arsenide), inP (indium phosphide), siC (silicon carbide), znSe (zinc selenide), gaN (gallium nitride), gaOx (gallium oxide; x is a real number larger than 0), or the like. Further, since the memory element using the OS transistor can be freely arranged by being stacked over a circuit using the Si transistor or the like, integration is easy. Further, since the OS transistor can be manufactured by the same manufacturing apparatus as the Si transistor, it can be manufactured at low cost. That is, the switch portion 1324 and the control circuit portion 1320 can be integrated in one chip by integrating the control circuit portion 1320 using an OS transistor in a stacked manner over the switch portion 1324. The control circuit portion 1320 can be reduced in size, so that miniaturization can be achieved.

The first batteries 1301a, 1301b mainly supply electric power to 42V series (high voltage series) in-vehicle devices, and the second battery 1311 supplies electric power to 14V series (low voltage series) in-vehicle devices. The second battery 1311 employs a lead storage battery in many cases because of cost advantages. However, lead-acid batteries have a disadvantage in that they are large in self-discharge as compared with lithium ion batteries and are susceptible to deterioration due to a phenomenon called sulfation. Although there is an advantage in that maintenance is not required when the lithium ion battery is used as the second battery 1311, an abnormality which is difficult to distinguish at the time of manufacture may occur during a long period of use, for example, three years or more. In particular, in order to prevent the situation that the engine cannot be started even when the first batteries 1301a and 1301b have a residual capacity when the second battery 1311 for starting the inverter fails to operate, when the second battery 1311 is a lead acid battery, electric power is supplied from the first battery to the second battery to charge the battery while maintaining the fully charged state.

The present embodiment shows an example in which both the first battery 1301a and the second battery 1311 use lithium ion batteries. The second battery 1311 may also use a lead storage battery, an all-solid-state battery, or an electric double layer capacitor. For example, the all-solid battery of embodiment 6 may be used. By using the all-solid-state battery according to embodiment 6 as the second battery 1311, high capacity can be achieved, and downsizing and weight saving can be achieved.

The regenerative energy caused by the rotation of the tire 1316 is transmitted to the engine 1304 through the transmission 1305, and is charged from the engine controller 1303 and the battery controller 1302 to the second battery 1311 through the control circuit portion 1321. Further, the first battery 1301a is charged from the battery controller 1302 through the control circuit part 1320. Further, the battery controller 1302 is charged to the first battery 1301b through the control circuit unit 1320. In order to efficiently charge the regenerated energy, it is preferable that the first batteries 1301a and 1301b be capable of high-speed charging.

The battery controller 1302 may set the charging voltage, charging current, and the like of the first batteries 1301a, 1301 b. The battery controller 1302 sets a charging condition according to the charging characteristics of the secondary battery to be used, and performs high-speed charging.

Although not shown, when connected to an external charger, a socket of the charger or a connection cable of the charger is electrically connected to the battery controller 1302. The power supplied from the external charger is charged to the first batteries 1301a and 1301b through the battery controller 1302. In addition, although some chargers are provided with a control circuit without using the function of the battery controller 1302, it is preferable that the first batteries 1301a and 1301b are charged by the control circuit part 1320 in order to prevent overcharge. In addition, a control circuit may be provided to a connection cable or a connection cable of a charger. The control circuit unit 1320 is sometimes referred to as an ECU (Electronic Control Unit: electronic control unit). The ECU is connected to a CAN (Controller Area Network: controller area network) provided in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. In addition, the ECU includes a microcomputer. In addition, the ECU uses a CPU or GPU.

As external chargers provided in charging stations and the like, there are 100V sockets-200V sockets, three-phase 200V and 50kW sockets, and the like. In addition, the charging may be performed by supplying electric power from an external charging device by a contactless power supply system or the like.

In order to charge in a short time during high-speed charging, a secondary battery capable of withstanding charging at a high voltage is expected.

In addition, when graphene is used as a conductive material and the capacity is kept high by suppressing the capacity from decreasing even if the electrode layer is made thick, a secondary battery having greatly improved electrical characteristics can be realized by a synergistic effect. In particular, it is effective for a secondary battery for a vehicle that can realize a long travel distance, specifically, a distance of 500km or more per charge traveling without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

In particular, the secondary battery according to the present embodiment can increase the operating voltage of the secondary battery by using the positive electrode active material 100 described in embodiments 1 and 2, and the like, and can increase the usable capacity as the charging voltage increases. Further, by using the positive electrode active material 100 described in embodiments 1,2, and the like as a positive electrode, a secondary battery for a vehicle having excellent cycle characteristics can be provided.

Next, an example in which a secondary battery as an embodiment of the present invention is mounted on a vehicle, typically a transportation vehicle, will be described.

In addition, when the secondary battery shown in any one of fig. 6D, 8C, and 12A is mounted in a vehicle, a new generation of clean energy vehicles such as a Hybrid Vehicle (HV), an Electric Vehicle (EV), or a plug-in hybrid vehicle (PHV) can be realized. In addition, the secondary battery may be mounted in agricultural machinery, electric bicycles including electric-assisted bicycles, motorcycles, electric wheelchairs, electric carting cars, ships, submarines, airplanes, rockets, satellites, space probes, planetary probes, or spacecraft. The secondary battery according to one embodiment of the present invention may be a high-capacity secondary battery. Therefore, the secondary battery according to one embodiment of the present invention is suitable for downsizing and weight saving, and can be suitably used for transportation vehicles.

Fig. 13A to 13D show a transport vehicle using one embodiment of the present invention. The automobile 2001 shown in fig. 13A is an electric automobile using an electric motor as a power source for traveling. Or the vehicle 2001 is a hybrid vehicle that can be used as a power source for traveling by appropriately selecting an electric engine and an engine. When the secondary battery is mounted in a vehicle, the example of the secondary battery shown in embodiment 4 may be provided in one or more portions. The automobile 2001 shown in fig. 13A includes a battery pack 2200 including a secondary battery module connecting a plurality of secondary batteries. In addition, it is preferable to further include a charge control device electrically connected to the secondary battery module.

In the vehicle 2001, the secondary battery included in the vehicle 2001 may be charged by supplying electric power from an external charging device by a plug-in system, a contactless power supply system, or the like. In the case of charging, the charging method, the specification of the connector, and the like may be appropriately performed according to a predetermined scheme such as CHAdeMO (trademark registered in japan) or the Combined charging system "Combined CHARGING SYSTEM". As the secondary battery, a charging station provided in a commercial facility or a power supply in a home may be used. For example, by supplying electric power from the outside using the plug-in technology, the power storage device mounted in the automobile 2001 can be charged. The charging may be performed by converting AC power into DC power by a conversion device such as an AC/DC converter.

Although not shown, the power receiving device may be mounted in a vehicle and may be charged by supplying electric power from a power transmitting device on the ground in a noncontact manner. When the noncontact power feeding method is used, the power transmission device is assembled to the road or the outer wall, so that charging can be performed not only during the stop but also during the traveling. Further, the noncontact power feeding method may be used to transmit and receive electric power between two vehicles. Further, a solar cell may be provided outside the vehicle, and the secondary battery may be charged during parking or traveling. Such non-contact power supply can be realized by electromagnetic induction or magnetic resonance.

In fig. 13B, a large transport vehicle 2002 including an engine controlled electrically is shown as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 is, for example: a secondary battery module in which four secondary batteries having a nominal voltage of 3.0V or more and 5.0V or less are used as battery cells and 48 cells are connected in series and the maximum voltage is 170V. The battery pack 2201 has the same function as that of fig. 13A except for the number of secondary batteries and the like constituting the secondary battery module, and therefore, description thereof is omitted.

In fig. 13C, a large-sized transportation vehicle 2003 including an engine controlled by electricity is shown as an example. The secondary battery module of the transport vehicle 2003 is, for example, the following battery: a secondary battery module in which 100 or more secondary batteries having a nominal voltage of 3.0V or more and 5.0V or less are connected in series and a maximum voltage of 600V is provided. Therefore, a secondary battery having less characteristic unevenness is demanded. By using the positive electrode active material 100 described in embodiments 1,2, and the like for a secondary battery of a positive electrode, a secondary battery having stable battery characteristics can be manufactured, and mass production can be performed at low cost from the viewpoint of yield. The battery pack 2202 has the same function as that of fig. 16A except for the number of secondary batteries constituting the secondary battery module, and the like, and therefore, description thereof is omitted.

Fig. 13D shows, as an example, an aircraft carrier 2004 on which an engine that burns fuel is mounted. Since the aviation carrier 2004 shown in fig. 13D includes wheels for lifting, it can be said that the aviation carrier 2004 is one type of transport vehicle, and the aviation carrier 2004 is connected with a plurality of secondary batteries to form a secondary battery module and includes a battery pack 2203 having the secondary battery module and a charge control device.

The secondary battery module of the aerial vehicle 2004 has, for example, eight 4V secondary batteries connected in series and has a maximum voltage of 32V. The same functions as those of fig. 13A are provided except for the number of secondary batteries and the like constituting the secondary battery modules of the battery pack 2203, and therefore, the description thereof is omitted.

Fig. 13E shows an artificial satellite 2005 using a secondary battery 2204 as an example. Since the artificial satellite 2005 is used in a very low-temperature space, it is preferable to include the secondary battery 2204 of one embodiment of the present invention having excellent low-temperature resistance. The secondary battery 2204 is preferably mounted inside the artificial satellite 2005 in a state of being covered with a heat insulating member.

Embodiment 6

In this embodiment, an example in which a secondary battery according to an embodiment of the present invention is mounted in a building will be described with reference to fig. 14A and 14B.

The house shown in fig. 14A includes a power storage device 2612 and a solar cell panel 2610 that include a secondary battery module according to an embodiment of the present invention. The power storage device 2612 is electrically connected to the solar cell panel 2610 through a wiring 2611 or the like. Further, the power storage device 2612 may be electrically connected to the ground-mounted charging device 2604. The electric power obtained by the solar cell panel 2610 may be charged into the electric storage device 2612. Further, the electric power stored in the electric storage device 2612 may be charged into a secondary battery included in the vehicle 2603 through a charging device 2604. The electric storage device 2612 is preferably provided in an underfloor space portion. By being provided in the underfloor space portion, the above-floor space can be effectively utilized. Or the electric storage device 2612 may be provided on the floor.

The electric power stored in the electric storage device 2612 may also be supplied to other electronic devices in the house. Therefore, even when power supply from a commercial power source cannot be received due to a power failure or the like, the electronic device can be utilized by using the power storage device 2612 according to one embodiment of the present invention as an uninterruptible power source.

Fig. 14B shows an example of an electric storage device according to an embodiment of the present invention. As shown in fig. 14B, an electric storage device 791 according to an embodiment of the present invention is provided in an underfloor space portion 796 of a building 799. The control circuit described in embodiment 7 may be provided in the power storage device 791, and a secondary battery using the positive electrode active material 100 that can be obtained in embodiments 1, 2, or the like for the positive electrode may be used in the power storage device 791, whereby a synergistic effect of safety can be obtained. The use of the control circuit described in embodiment 7 and the positive electrode active material 100 described in embodiments 1, 2, and the like for the secondary battery of the positive electrode greatly contributes to reduction of accidents such as fire disaster caused by the power storage device 791 including the secondary battery.

A control device 790 is provided in the power storage device 791, and the control device 790 is electrically connected to the power distribution board 703, the power storage controller 705 (also referred to as a control device), the display 706, and the router 709 via wires.

Power is supplied from the commercial power supply 701 to the distribution board 703 through the inlet mount 710. Further, both the electric power from the power storage device 791 and the electric power from the commercial power supply 701 are supplied to the power distribution board 703, and the power distribution board 703 supplies the supplied electric power to the general load 707 and the power storage load 708 through a receptacle (not shown).

The general load 707 includes, for example, an electronic device such as a television or a personal computer, and the electric storage load 708 includes, for example, an electronic device such as a microwave oven, a refrigerator, or an air conditioner.

The power storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has a function of measuring the power consumption of the normal load 707 and the power storage load 708 in one day (for example, 0 to 24 points). The measurement unit 711 may also have a function of measuring the amount of electric power supplied from the commercial power supply 701, as well as the amount of electric power of the power storage device 791. The prediction unit 712 has a function of predicting the required power amount to be consumed by the general load 707 and the power storage load 708 in the next day based on the power consumption amounts of the general load 707 and the power storage load 708 in the day. Planning unit 713 also has a function of determining a charge/discharge plan of power storage device 791 based on the amount of electricity required predicted by prediction unit 712.

The amount of power consumed by the normal load 707 and the power storage load 708 measured by the measurement unit 711 can be confirmed using the display 706. Further, the electronic device such as a television or a personal computer may be used for confirmation via the router 709. Further, the mobile electronic terminal such as a smart phone or a tablet terminal may be used for confirmation via the router 709. In addition, the required power amount for each period (or each hour) predicted by the prediction unit 712 may be checked by the display 706, the electronic device, or the portable electronic terminal.

Embodiment 7

In the present embodiment, an example is shown in which the power storage device according to one embodiment of the present invention is mounted on a two-wheeled vehicle or a bicycle.

Fig. 15A shows an example of an electric bicycle using the power storage device according to one embodiment of the present invention. The electric bicycle 8700 shown in fig. 15A can use the power storage device according to one embodiment of the present invention. For example, an electric storage device according to an embodiment of the present invention includes a plurality of storage batteries and a protection circuit.

The electric bicycle 8700 includes an electric storage device 8702. The power storage device 8702 supplies electric power to an engine that assists the driver. Further, the power storage device 8702 is portable, and fig. 15B shows the power storage device 8702 taken out from the bicycle. The power storage device 8702 includes a plurality of storage batteries 8701 included in the power storage device according to one embodiment of the present invention, and the remaining power and the like can be displayed on the display unit 8703. Further, power storage device 8702 includes a control circuit 8704 that enables charge control or abnormality detection of the secondary battery as shown in embodiment 7. The control circuit 8704 is electrically connected to the positive electrode and the negative electrode of the battery 8701. In addition, by combining with a secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1, 2, and the like for a positive electrode, a synergistic effect of safety can be obtained. The secondary battery and the control circuit 8704 in which the positive electrode active material 100 obtained in embodiments 1, 2, and the like is used for the positive electrode greatly contribute to reduction of accidents such as fire of the secondary battery.

Fig. 15C shows an example of a two-wheeled vehicle using the power storage device according to the embodiment of the present invention. The scooter 8600 shown in fig. 15C includes a power storage device 8602, a side mirror 8601, and a turn signal 8603. The power storage device 8602 may supply electric power to the direction lamp 8603. Further, the power storage device 8602 in which a plurality of secondary batteries using the positive electrode active material 100 that can be obtained in embodiments 1, 2, and the like are mounted can have a high capacity, and can contribute to miniaturization.

In addition, in the scooter type motorcycle 8600 shown in fig. 15C, the power storage device 8602 may be housed in the under-seat housing portion 8604. Even if the underfloor storage unit 8604 is small, the power storage device 8602 can be stored in the underfloor storage unit 8604.

Embodiment 8

In this embodiment, an example in which a secondary battery according to an embodiment of the present invention is mounted in an electronic device will be described. Examples of the electronic device mounted with the secondary battery include a television device (also referred to as a television or a television receiver), a display for a computer or the like, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also referred to as a mobile phone or a mobile phone device), a portable game machine, a portable information terminal, a sound reproducing device, a large-sized game machine such as a pachinko machine, and the like. Examples of the portable information terminal include a notebook personal computer, a tablet terminal, an electronic book terminal, and a mobile phone.

Fig. 16A shows an example of a mobile phone. The mobile phone 2100 includes an operation button 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like, in addition to the display portion 2102 attached to the housing 2101. Further, the mobile phone 2100 includes a secondary battery 2107. By including the secondary battery 2107 in which the positive electrode active material 100 described in embodiments 1,2, and the like is used for the positive electrode, a high capacity can be achieved, and a structure that can cope with space saving required for downsizing of the housing can be achieved.

The mobile phone 2100 may execute various applications such as mobile phones, emails, reading and writing of articles, music playing, network communication, computer games, etc.

The operation button 2103 may have various functions such as a power switch, a wireless communication switch, setting and canceling of a mute mode, setting and canceling of a power saving mode, and the like, in addition to time setting. For example, by using an operating system incorporated in the mobile phone 2100, the functions of the operation buttons 2103 can be freely set.

In addition, the mobile phone 2100 may perform short-range wireless communication standardized by communication. For example, hands-free conversation may be performed by communicating with a wireless-enabled headset.

The mobile phone 2100 includes an external connection port 2104, and can directly transmit data to or receive data from another information terminal through a connector. In addition, charging may also be performed through the external connection port 2104. In addition, the charging operation may be performed by wireless power supply instead of using the external connection port 2104.

The mobile phone 2100 preferably includes a sensor. As the sensor, for example, a fingerprint sensor, a pulse sensor, a human body sensor such as a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like is preferably mounted.

Fig. 16B shows an unmanned aerial vehicle 2300 that includes a plurality of rotors 2302. The unmanned aerial vehicle 2300 is also referred to as an unmanned aerial vehicle. The unmanned aerial vehicle 2300 includes a secondary battery 2301, a camera 2303, and an antenna (not shown) according to one embodiment of the present invention. The unmanned aerial vehicle 2300 may be remotely operated through an antenna. The secondary battery using the positive electrode active material 100 obtained in embodiments 1 and 2 for the positive electrode has high energy density and high safety, and therefore can be safely used for a long period of time, and is therefore suitable as a secondary battery to be mounted on the unmanned aerial vehicle 2300.

Fig. 16C shows an example of a robot. The robot 6400 shown in fig. 16C includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display portion 6405, a lower camera 6406, an obstacle sensor 6407, a moving mechanism 6408, a computing device, and the like.

The microphone 6402 has a function of detecting a user's voice, surrounding voice, and the like. In addition, the speaker 6404 has a function of emitting sound. The robot 6400 may communicate with a user via a microphone 6402 and a speaker 6404.

The display portion 6405 has a function of displaying various information. The robot 6400 may display information required by the user on the display 6405. The display portion 6405 may be provided with a touch panel. The display unit 6405 may be a detachable information terminal, and by providing it at a fixed position of the robot 6400, charging and data transmission/reception can be performed.

The upper camera 6403 and the lower camera 6406 have a function of capturing images of the surrounding environment of the robot 6400. The obstacle sensor 6407 may detect whether or not an obstacle exists in the forward direction of the robot 6400 when the robot 6400 is moving forward, using the moving mechanism 6408. The robot 6400 can safely move by checking the surrounding environment using the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407.

The robot 6400 is internally provided with a secondary battery 6409 and a semiconductor device or an electronic component according to one embodiment of the present invention. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1,2, and the like as a positive electrode has a high energy density and high safety, and therefore can be safely used for a long period of time, and is therefore suitable as the secondary battery 6409 to be mounted on the robot 6400.

Fig. 16D shows an example of the sweeping robot. The robot 6300 includes a display portion 6302 arranged on the surface of a housing 6301, a plurality of cameras 6303 arranged on the side, brushes 6304, operation buttons 6305, a secondary battery 6306, various sensors, and the like. Although not shown, the sweeping robot 6300 also has wheels, suction ports, and the like. The sweeper robot 6300 may be self-propelled and may detect the debris 6310 and draw the debris into a suction opening provided below.

The sweeping robot 6300 can determine whether there is an obstacle such as a wall, furniture, or a step by analyzing an image photographed by the camera 6303. In addition, when an object such as an electric wire that may be entangled with the brush 6304 is found by image analysis, the rotation of the brush 6304 may be stopped. The inner area of the robot 6300 is provided with a secondary battery 6306 and a semiconductor device or an electronic component according to one embodiment of the present invention. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1,2, and the like for the positive electrode has high energy density and high safety, and therefore can be safely used for a long period of time, and is therefore suitable as the secondary battery 6306 to be mounted on the robot 6300.

Fig. 17A shows an example of a wearable device. The power supply of the wearable device uses a secondary battery. In addition, in order to improve splash-proof, waterproof, or dust-proof performance of a user in life or outdoor use, the user desires to enable wireless charging in addition to wired charging in which a connector portion for connection is exposed.

For example, the secondary battery according to one embodiment of the present invention may be mounted on the glasses-type device 4000 shown in fig. 17A. The eyeglass type apparatus 4000 includes a frame 4000a and a display 4000b. By attaching the secondary battery to the temple portion having the curved frame 4000a, the eyeglass-type apparatus 4000 which is lightweight and has a good weight balance and a long continuous service time can be realized. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1,2, and the like for the positive electrode has a high energy density, and a structure capable of coping with space saving required for miniaturization of the frame can be achieved.

In addition, the secondary battery according to one embodiment of the present invention may be mounted on the headset device 4001. The headset device 4001 includes at least a microphone portion 4001a, a flexible tube 4001b, and an ear speaker portion 4001c. In addition, a secondary battery may be provided in the flexible tube 4001b or in the ear speaker portion 4001c. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1,2, and the like for the positive electrode has a high energy density, and a structure capable of coping with space saving required for miniaturization of the frame can be achieved.

In addition, the secondary battery according to one embodiment of the present invention may be mounted on the device 4002 that can be directly mounted on the body. In addition, the secondary battery 4002b may be provided in a thin frame 4002a of the device 4002. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1,2, and the like for the positive electrode has a high energy density, and a structure capable of coping with space saving required for miniaturization of the frame can be achieved.

In addition, the secondary battery according to one embodiment of the present invention may be mounted on the clothes-mountable device 4003. In addition, the secondary battery 4003b may be provided in a thin frame 4003a of the device 4003. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1,2, and the like for the positive electrode has a high energy density, and a structure capable of coping with space saving required for miniaturization of the frame can be achieved.

In addition, the secondary battery according to one embodiment of the present invention may be mounted on the belt-type device 4006. The belt-type device 4006 includes a belt portion 4006a and a wireless power supply and reception portion 4006b, and the secondary battery can be mounted in an inner region of the belt portion 4006 a. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1,2, and the like for the positive electrode has a high energy density, and a structure capable of coping with space saving required for miniaturization of the frame can be achieved.

In addition, the secondary battery according to one embodiment of the present invention may be mounted on the wristwatch type device 4005. The wristwatch-type device 4005 includes a display portion 4005a and a band portion 4005b, and the secondary battery may be provided on the display portion 4005a or the band portion 4005 b. The secondary battery using the positive electrode active material 100 which can be obtained in embodiments 1, 2, and the like for the positive electrode has a high energy density, and a structure capable of coping with space saving required for miniaturization of the frame can be achieved.

The display portion 4005a can display various information such as an email and a telephone call in addition to time.

Further, since the wristwatch-type device 4005 is a wearable device wound directly around the wrist, a sensor for measuring the pulse, blood pressure, or the like of the user may be mounted. Thus, the exercise amount and the health-related data of the user can be stored for health management.

Fig. 17B is a perspective view showing the wristwatch-type device 4005 removed from the wrist.

In addition, fig. 17C is a side view. Fig. 17C shows a case where the secondary battery 913 is built in the internal region. The secondary battery 913 is a secondary battery shown in embodiment 4. The secondary battery 913 is provided at a position overlapping the display portion 4005a, and can achieve high density and high capacity, and is small and lightweight.

Since the wristwatch-type device 4005 needs to be small and lightweight, a high energy density and small-sized secondary battery 913 can be realized by using the positive electrode active material 100 that can be obtained in embodiments 1,2, and the like for the positive electrode of the secondary battery 913.

Example 1

< Method for producing sample 1 >

In this example, a positive electrode active material 100 (sample 1) having a median particle diameter (D50) of 12 μm or less was obtained from the description of embodiment 1, fig. 2 to 3, and the like.

As a starting material lithium cobalt oxide (LiCoO ₂) shown in step S10 of fig. 2, commercially available lithium cobalt oxide (CELLSEED C-5H manufactured by japan chemical industry co.) containing no additive element was prepared. In the following description and the like, it will be referred to as "C-5H" only. The median particle diameter (D50) of C-5H is about 7.0 μm, and the condition that the median particle diameter (D50) is 10 μm or less is satisfied.

Next, as heating in step S15, C-5H was placed in a sagger (container), covered with a lid, and then heated in a muffle furnace at 850℃for 2 hours. No flow (O ₂ purge) was performed after the atmosphere in the muffle furnace was changed to an oxygen atmosphere. When C-5H is placed in the sagger, it is placed so that the height of powder (also referred to as bulk) is 10mm or less in the sagger and is flat.

Next, a first additive element A1 source is manufactured according to step S20a shown in fig. 3A. First, lithium fluoride (LiF) was prepared as an F source, and magnesium fluoride (MgF ₂) was prepared as an Mg source. The following formula of LiF: the ratio of MgF ₂ is 1:3 (molar ratio) LiF and MgF ₂ were weighed. Then, liF and MgF ₂ were mixed with dehydrated acetone, and stirred at a rotation speed of 400rpm for 12 hours. A ball mill was used in combination, and zirconia balls were used as a grinding medium. Dehydrated acetone 20mL and zirconia balls22G and a total of about 10g of LiF source and MgF ₂ source were placed in a mixing ball mill having a container capacity of 45mL and mixed. Then, screening was performed using a sieve having a mesh size of 300 μm, thereby obtaining a first additive element A1 source.

Next, lithium cobaltate (lithium cobaltate after initial heating) obtained by the heating of step S15 and the first additive element A1 source obtained by step S20a are mixed according to step S31 shown in fig. 2. Specifically, about 9g in total of lithium cobaltate and the additive element A1 source were weighed so that the additive element A1 was 1mol% with respect to the lithium cobaltate, and then the initially heated lithium cobaltate and the first additive element A1 source were mixed in a dry manner. At this time, stirring was carried out at a rotation speed of 150rpm for 1 hour. Then, screening was performed using a sieve having a mesh size of 300 μm to obtain a mixture 903 (step S32).

Next, as step S33, the mixture 903 is heated. The heating conditions were 900℃for 5 hours. The sagger containing the mixture 903 is capped when heated. The atmosphere in the sagger was an atmosphere containing oxygen, and the entry and exit of the oxygen were blocked (purging). The composite oxide containing Mg and F (lithium cobalt oxide containing Mg and F) is obtained by heating (step S34 a).

Next, a second additive element A2 source is manufactured according to step S40 shown in fig. 3C. First, nickel hydroxide (Ni (OH) ₂) was prepared as a Ni source, and aluminum hydroxide (Al (OH) ₃) was prepared as an Al source. Next, nickel hydroxide and aluminum hydroxide were stirred in dehydrated acetone at a rotation speed of 400rpm for 12 hours, respectively. A ball mill was used in combination, and zirconia balls were used as a grinding medium. Dehydrated acetone 20mL and zirconia balls22G and about 10g of nickel hydroxide were placed in a ball mill vessel having a capacity of 45mL and stirred. Likewise, dehydrated acetone 20mL, zirconia balls/>22G and about 10g of aluminum hydroxide were placed in a ball mill vessel having a capacity of 45mL and stirred. Then, screening was performed using sieves having a mesh size of 300 μm, respectively, to thereby obtain a second additive element A2 source.

Next, as step S51, the composite oxide containing Mg and F and the second additive element A2 source are mixed in a dry method. Specifically, the mixture was stirred at a rotation speed of 150rpm for 1 hour. The mixing ratio was set so that the nickel hydroxide and aluminum hydroxide in the source of the second additive element A2 were each 0.5mol% with respect to lithium cobaltate. A ball mill was used in combination, and zirconia balls were used as a grinding medium. A ball mill vessel for mixing having a capacity of 45mL was charged with 22g of zirconia ballsAnd a total of about 7.5g of Ni source, al source and the composite oxide (lithium cobalt oxide containing Mg and F) obtained in the step S34 were mixed. Finally, screening was performed using a sieve having a mesh size of 300 μm to obtain a mixture 904 (step S52).

Next, as step S53, the mixture 904 is heated. The heating conditions were 850℃for 2 hours. Upon heating, the sagger containing the mixture 904 is capped. The atmosphere in the sagger was an atmosphere containing oxygen, and the entry and exit of the oxygen were blocked (purging). Lithium cobalt oxide (composite oxide) containing Mg, F, ni, and Al is obtained by heating (step S54). In the present specification and the like, lithium cobaltate containing Mg, F, ni, and Al obtained in this example is sometimes referred to as sample 1.

< Median particle diameter (D50) of sample 1>

Fig. 18 shows the particle size distribution of sample 1 in solid lines. The median particle diameter (D50) of sample 1 was about 9.7. Mu.m. From this, it was confirmed that the median diameter (D50) of sample 1 satisfied the condition of 12 μm or less (10.5 μm or less). The median particle diameter (D50) can be measured by, for example, observation by SEM (scanning electron microscope) or TEM, or a particle size distribution analyzer by a laser diffraction scattering method. In this example, measurement was performed using a laser diffraction particle size distribution measuring instrument SALD-2200 manufactured by Shimadzu corporation.

In addition, in fig. 18, as reference example 1, the particle size distribution of commercially available lithium cobaltate (CELLSEED C H manufactured by japan chemical industry co.) containing no additive element used as a starting material in this example is shown in a broken line. The median particle diameter (D50) of C-5H was about 7.0. Mu.m.

< Surface SEM observation of sample 1 >

Next, fig. 19A shows the (surface) SEM observation result of sample 1. In addition, FIG. 19B shows the (surface) SEM observation result of lithium cobalt oxide (C-5H) as a starting material of sample 1. As SEM observation in this example, fig. 19A is a result of measurement using a scanning electron microscope device S4800 manufactured by hitachi high new technology, and fig. 19B is a result of measurement using a scanning electron microscope device SU8030 manufactured by hitachi high new technology. The measurement conditions in fig. 19A and 19B were set to an acceleration voltage of 5kV and an amplification factor of 2 ten thousand times.

As shown in fig. 19A, the surface of sample 1 has very few irregularities. On the other hand, as shown in fig. 19B, the surface roughness of lithium cobalt oxide (C-5H) as the starting material of sample 1 was very large.

Example 2

< Manufacturing half cell Using sample 1 as cathode active Material >

In this example, the production conditions for producing a coin-type half cell using sample 1 produced in example 1 as a positive electrode active material will be described. In addition, in order to confirm reproducibility of the experiment, half cells 1 to 7 were manufactured under the same conditions.

First, sample 1 was prepared as a positive electrode active material, acetylene Black (AB) was prepared as a conductive material, and polyvinylidene fluoride (PVDF) was prepared as a binder. PVDF dissolved in N-methyl-2-pyrrolidone (NMP) in a weight ratio of 5% in advance was prepared. Next, a positive electrode active material was used: AB: pvdf=95: 3:2 (weight ratio) to prepare a slurry, and coating the slurry on an aluminum positive electrode current collector. As a solvent for the slurry, NMP was used.

Next, after the slurry is coated on the positive electrode current collector, the solvent is volatilized.

Then, in order to increase the density of the positive electrode active material layer on the positive electrode current collector, a pressing treatment is performed using a roll press. In the conditions of the pressing treatment, the line pressure was 210kN/m. The upper and lower rolls of the roll press were all 120 ℃.

Through the above steps, a positive electrode is obtained. The active material loading of the positive electrode was about 7mg/cm ².

The electrolytes for half cells 1 to 7 contain an organic solvent. As the organic solvents, the following were used: comprises Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC), and when the total content of the EC, the EMC and the DMC is 100vol%, the volume ratio of the EC, the EMC and the DMC is x: y:100-x-y (note, 5.ltoreq.x.ltoreq.35 and 0< y < 65). More specifically, preparation was made with EC: EMC: dmc=30: 35:35 (volume ratio) organic solvents including EC, EMC and DMC. Lithium hexafluorophosphate (LiPF ₆) dissolved in the organic solvent at a ratio of 1mol/L was used as an electrolyte. In the following description and the like, this electrolytic solution is referred to as "electrolytic solution a".

Since a general electrolyte for lithium ion batteries solidifies at around-20 ℃, it is difficult to manufacture a battery that can be charged and discharged at-40 ℃. The freezing point of the electrolyte used in this example was-40 ℃ or lower, which is one of the requirements required to realize a lithium ion battery capable of charge and discharge even in an extremely low temperature environment of-40 ℃.

The separator used was a polypropylene porous film. Further, lithium metal was used as the negative electrode (counter electrode). Coin-type half cells (half cell 1 to half cell 7) were manufactured using these materials. In addition, the half cells 1 to 7 may be referred to as test cells.

Example 3

In this embodiment, measurement results of half cells 1 to 7 manufactured in embodiment 2 are described.

<25 ℃ Discharge capacity >

The discharge capacity at 25℃was measured using half cell 1. Charging is performed as follows: constant-current charging is performed at a current of 0.1C (1c=200 mA/g) until the voltage reaches 4.60V, and then constant-voltage charging is performed at 4.60V until the charging current is equal to or less than 0.01C. The discharge conditions were constant current discharge at a discharge rate of 0.1C (note, 1c=200 mA/g) until 2.5V (off voltage) was reached.

The half cells 1 to 7 were repeatedly charged and discharged three times under the above charge and discharge conditions. Table 1 shows a current value of 0.1C, a discharge capacity at 25 ℃ (third discharge capacity), a weight of the positive electrode active material, and a discharge capacity per weight of the positive electrode active material (third discharge capacity). Fig. 20 is a photograph showing the appearance of half cell 2.

TABLE 1

< Temperature Properties of discharge capacity >

Next, the temperature characteristics measured using the half cell 1 will be described.

After the measurement shown in table 1, the discharge capacities of the half cells 1 were measured under a plurality of temperature conditions, respectively. The temperature at the time of discharge was set to 25 ℃,0 ℃, -20 ℃ and-40 ℃, and charging was performed at 25 ℃ before the discharge test was performed at each temperature. Charging is performed as follows: constant-current charging is performed at a current of 0.1C (1c=200 mA/g) until the voltage reaches 4.60V, and then constant-voltage charging is performed at 4.60V until the charging current is equal to or less than 0.01C. The conditions at the time of discharge were the same except for the temperature, and constant current discharge was performed at a discharge rate of 0.1C (note, 1c=200 mA/g) until 2.5V (off-voltage) was reached. The temperature at the time of charging or discharging described in the examples of the present specification was set to the temperature of the constant temperature tank in which the half cell was left for a certain period of time.

Fig. 21 shows discharge curves at respective temperatures at the time of discharge. In the discharge curve of fig. 21, the dotted line shows the result of the temperature at the time of discharge being 25 ℃, the dash-dot line shows the result of the temperature at the time of discharge being 0 ℃, the broken line shows the result of the temperature at the time of discharge being-20 ℃, and the solid line shows the result of the temperature at the time of discharge being-40 ℃. Table 2 shows the measurement results of the discharge capacity, the average discharge voltage, and the discharge energy density at each temperature during discharge. Table 3 shows the ratio (unit:%) of the discharge capacity, average discharge voltage, and discharge energy density at each temperature at the time of discharge, divided by the normalized discharge capacity, average discharge voltage, and discharge energy density at the time of discharge at a temperature of 25 ℃. The discharge capacity (unit: mAh/g) in Table 2 is a value calculated per unit weight of the positive electrode active material. The discharge energy density (unit: mWh/g) in Table 2 is a value calculated by multiplying the discharge capacity by the average discharge voltage (unit: V).

TABLE 2

TABLE 3

As shown in fig. 21, table 2 and table 3, the discharge capacity was very high under the conditions of 0 ℃ and-20 ℃, and almost the same even under the conditions of 25 ℃. Specifically, the discharge capacity at 0℃was 99.5% of the discharge capacity at 25℃and the discharge capacity at-20℃was 98.3% of the discharge capacity at 25 ℃. In addition, a high discharge capacity can be obtained even at-40 ℃. Specifically, the discharge capacity at-40 ℃ was 93.7% of the discharge capacity at 25 ℃, and it was confirmed that the discharge capacity of 90% or more of the discharge capacity at 25 ℃ could be obtained even in a very low temperature environment such as-40 ℃.

As is clear from the results shown in fig. 21, table 2 and table 3, the lithium ion battery including the positive electrode active material and the electrolyte a obtained by the manufacturing method described in embodiment 1 and the like can operate at least in a temperature range of-40 ℃ to 25 ℃.

As shown in fig. 21, tables 2 and 3, sample 1 can obtain a very high discharge capacity of 200mAh/g or more even at a discharge temperature of-40 ℃. From another point of view, excellent results were obtained in which the discharge capacity at-40℃discharge was 90% or more of the discharge capacity at 25℃discharge. From another point of view, a high discharge energy density of around 700mWh/g is obtained at a discharge temperature of-40 ℃. From another point of view, the discharge energy density at-40 ℃ discharge was 78.3% of the discharge energy density at 25 ℃. From this, the following results were achieved and obtained: the discharge capacity at-40 ℃ is 200mAh/g or more, the discharge capacity at-40 ℃ is 90% or more of the discharge capacity at 25 ℃ or more, the discharge energy density at-40 ℃ is 650mAh/g or more, and the discharge energy density at-40 ℃ is 75% or more of the discharge energy density at 25 ℃ or more.

Although the temperature at the time of discharge was low (i.e., in a low-temperature environment), the lithium ion battery using sample 1 as the positive electrode active material had a very high discharge capacity, and it was assumed that the composite oxide (positive electrode active material) of sample 1 and the electrolyte a had very small diffusion resistance of lithium ions even in a low-temperature environment. From the above results, it is clear that the positive electrode active material and the electrolyte a obtained by the production method described in embodiment 1 and the like are very useful as materials for lithium ion batteries used in low-temperature environments (for example, -40 ℃).

< Charge and discharge in Low temperature Environment >

Next, discharge capacity temperature characteristics measured using the half cell 7 will be described. In the measurements shown in fig. 21, table 2 and table 3, the charging was performed at 25 ℃ and the discharging was performed under a plurality of temperature conditions, whereas the present measurement was performed under the same temperature conditions and the discharging was performed under a plurality of temperature conditions.

The charge and discharge conditions in the low-temperature environment of the half cell 7 will be described. After charging and discharging at 25℃as shown in Table 1, charging and discharging were performed at a plurality of temperature conditions in the order of 0 ℃, 25 ℃, 20 ℃, 25 ℃ and 40 ℃. As charge and discharge conditions, constant current charge was performed at a current of 0.1C under all temperature conditions until the voltage reached 4.60V, and then constant voltage charge was performed at 4.60V until the current was equal to or less than 0.01C. The discharge conditions were that constant current discharge was performed at a current of 0.1C until 2.5V (off-voltage) was reached. In addition, 1c=200 mA/g.

Fig. 22 shows a charge curve and a discharge curve (also referred to as charge-discharge curve) of the half cell 7 manufactured using the sample 1.

In the charge-discharge curve of fig. 22, the dotted line shows the result of the temperature at the time of charge-discharge being 25 ℃, the dash-dot line shows the result of the temperature at the time of discharge being 0 ℃, the broken line shows the result of the temperature at the time of charge-discharge being-20 ℃, and the solid line shows the result of the temperature at the time of charge-discharge being-40 ℃. Table 4 shows the measurement results of the discharge capacity, the average discharge voltage, and the discharge energy density at each temperature during charge and discharge. Table 5 shows the ratio (unit:%) of the discharge capacity, average discharge voltage, and discharge energy density at each temperature at the time of discharge, divided by the normalized discharge capacity, average discharge voltage, and discharge energy density at the time of discharge at a temperature of 25 ℃. The discharge capacity (unit: mAh/g) in Table 4 is a value calculated per unit weight of the positive electrode active material. The discharge energy density (unit: mWh/g) in Table 4 is a value calculated by multiplying the discharge capacity by the average discharge voltage (unit: V).

TABLE 4

TABLE 5

As is clear from the results shown in fig. 22, table 4, and table 5, the lithium ion battery including the positive electrode active material and the electrolyte a obtained by the manufacturing method described in embodiment 1 and the like can perform the charge operation and the discharge operation at least in the temperature range of-40 ℃ to 25 ℃.

As shown in fig. 22, tables 4 and 5, sample 7 can obtain a very high discharge capacity of 170mAh/g or more even at a charge temperature and a discharge temperature of-40 ℃. From another point of view, excellent results were obtained in which the discharge capacity at-40℃was 80% or more of the discharge capacity at 25℃in charge-discharge. From this, the following results were achieved and obtained: the discharge capacity at the charge temperature and the discharge temperature is 170mAh/g or more at-40 ℃, and the discharge capacity at-40 ℃ is 80% or more of the discharge capacity at 25 ℃.

[ Description of the symbols ]

100: Positive electrode active material, 903: mixture, 904: mixture of

Claims (8)

1. A method for producing a composite oxide, comprising the steps of:

A first step of heating lithium cobaltate having a median particle diameter (D50) of 10 [ mu ] m or less at a temperature of 700 ℃ to 1000 ℃ for 1 to 5 hours;

A second step of producing a first mixture by mixing the lithium cobaltate subjected to the first step with a fluorine source and a magnesium source;

A third step of heating the first mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 10 hours;

A fourth step of producing a second mixture by mixing the first mixture subjected to the third step with a nickel source and an aluminum source; and

And a fifth step of heating the second mixture at a temperature of 800 ℃ to 950 ℃ for 1 hour to 5 hours.

2. The method for producing a composite oxide according to claim 1,

Wherein the atomic number of magnesium contained in the magnesium source is 0.3% or more and 3% or less of the atomic number of cobalt contained in the lithium cobaltate subjected to the first step.

3. The method for producing a composite oxide according to claim 2,

Wherein the fluorine source is lithium fluoride,

The magnesium source is magnesium fluoride, and the magnesium source is magnesium fluoride,

And the ratio of the number of moles of lithium fluoride M _LiF to the number of moles of magnesium fluoride M _MgF2 is M _LiF：M_MgF2 =x: 1 (0.1.ltoreq.x.ltoreq.0.5).

4. The method for producing a composite oxide according to claim 3,

Wherein the nickel source contains nickel with an atomic number of 0.05% to 4% of the atomic number of cobalt contained in the lithium cobaltate subjected to the first step.

5. The method for producing a composite oxide according to claim 4,

Wherein the aluminum source contains aluminum in an atomic number of 0.05% to 4% of the atomic number of cobalt contained in the lithium cobaltate subjected to the first step.

6. The method for producing a composite oxide according to claim 5,

Wherein the first step is performed under an atmosphere containing oxygen in a state where a lid is covered on a sagger containing the lithium cobaltate.

7. A method for manufacturing a lithium ion battery having a positive electrode containing a positive electrode active material, an electrolyte, and a negative electrode containing a negative electrode active material that is a carbon material,

Wherein the positive electrode active material is formed by the steps of:

A first step of heating lithium cobaltate having a median particle diameter (D50) of 10 [ mu ] m or less at a temperature of 700 ℃ to 1000 ℃ for 1 to 5 hours;

A second step of producing a first mixture by mixing the lithium cobaltate subjected to the first step with a fluorine source and a magnesium source;

A third step of heating the first mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 10 hours;

A fourth step of producing a second mixture by mixing the first mixture subjected to the third step with a nickel source and an aluminum source; and

And a fifth step of heating the second mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 5 hours.

8. A method for manufacturing a lithium ion battery having a positive electrode containing a positive electrode active material, an electrolyte, and a negative electrode containing a negative electrode active material that is a carbon material,

Wherein the electrolyte comprises ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate, and the ratio of the volume V _EC of the ethylene carbonate, the volume V _EMC of the ethylmethyl carbonate and the volume V _DMC of the dimethyl carbonate is V _EC：V_EMC：V_DMC =x: y:100-x-y (note, 5.ltoreq.x.ltoreq.35 and 0< y < 65),

And, the positive electrode active material is formed by the steps of:

A first step of heating lithium cobaltate having a median particle diameter (D50) of 10 [ mu ] m or less at a temperature of 700 ℃ to 1000 ℃ for 1 to 5 hours;

A second step of producing a first mixture by mixing the lithium cobaltate subjected to the first step with a fluorine source and a magnesium source;

A third step of heating the first mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 10 hours;

A fourth step of producing a second mixture by mixing the first mixture subjected to the third step with a nickel source and an aluminum source; and

And a fifth step of heating the second mixture at a temperature of 800 ℃ to 1100 ℃ for 1 hour to 5 hours.