WO2015163356A1

WO2015163356A1 - Positive electrode active material for non-aqueous secondary cell, and non-aqueous secondary cell

Info

Publication number: WO2015163356A1
Application number: PCT/JP2015/062212
Authority: WO
Inventors: 呈▲民▼ 金; 直人丸; 真一郎今井; 田中　克知; 曽我　巌
Original assignee: 三菱化学株式会社
Priority date: 2014-04-22
Filing date: 2015-04-22
Publication date: 2015-10-29
Also published as: JPWO2015163356A1; JP2019165010A

Abstract

　The first problem to be addressed by the present invention is to provide, with regards to a non-aqueous secondary cell, a positive electrode active material for a non-aqueous secondary cell that yields a non-aqueous secondary cell in which any increase in positive electrode resistance after cycle charge/discharge is minimized and any decrease in cell capacity is reduced, and a non-aqueous secondary cell in which the positive electrode active material for a non-aqueous secondary cell is used. The present invention pertains to a positive electrode active material for a non-aqueous secondary cell satisfying the following conditions (1)-(3). (1) A positive electrode active material core is a lithium compound having a structure that contains Ni, Co, and M (where M is Mn and/or Al) and into/from which Li ions can be inserted and extracted. (2) A Zr-containing region containing all of Zr, Ni, Co, and M is present in a portion located at a depth of 0.1-100 nm from the active material surface. (3) The molar ratio of Zr in relation to (Zr+Ni+Co+M) in the Zr-containing region is 1.5-30%.

Description

Cathode active material for non-aqueous secondary battery and non-aqueous secondary battery

The present invention relates to a positive electrode active material for a non-aqueous secondary battery and a non-aqueous secondary battery.

Technology is rapidly advancing in portable information electronic devices such as smartphones, tablet terminals and notebook computers; electric vehicles; and power tools, and their supply is also increasing. Along with this, the required performance for the batteries used for these main power supplies and backup power supplies is increasing. Non-aqueous secondary batteries such as lithium ion secondary batteries, which have a higher energy density than nickel-cadmium batteries and nickel-hydrogen batteries, have attracted attention as a means that can meet this demand.

Usually, in a lithium ion secondary battery, a transition metal composite oxide that can mainly store and release lithium ions is used for the positive electrode, and a material that can mainly store and release lithium ions is used for the negative electrode. ing. Typical examples of the transition metal in the transition metal composite oxide include cobalt, nickel, manganese, iron and the like. Examples of the negative electrode active material used for the negative electrode include carbonaceous materials such as natural graphite, artificial graphite, and amorphous carbon; metals that can achieve high capacity, metals and alloys using tin, and the like. .

Moreover, as a typical example of the electrolyte solution of a lithium ion secondary battery, electrolytes such as LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO ₃ , ethylene carbonate, propylene carbonate Non-aqueous electrolyte solution dissolved in a mixed solvent of a high dielectric constant solvent such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

Since such a lithium ion secondary battery uses a positive electrode and a negative electrode with high activity, a side reaction between the electrode and the electrolytic solution causes a decrease in charge / discharge capacity, an increase in gas generation, and a resistance. It is known to increase. These lead to shortened battery life.

Especially when used / stored at high temperature or high voltage, the problem of oxidative decomposition of the electrolytic solution due to the side reaction becomes large. Therefore, various studies have been made on each component of the non-aqueous secondary battery in order to improve battery characteristics.

For example, one of the methods for improving the positive electrode active material is the addition of trace elements. Significantly suppress the deterioration of the positive electrode active material in the battery by stabilizing the crystal structure of the active material by adding a small amount of an element different from the main constituent element such as Al or Zr to the positive electrode active material Can do.

Also, surface treatment technology can be cited as another positive electrode active material improvement technique. In the surface treatment technique, a layer of a compound containing a metal element such as a metal oxide is formed on the surface of the positive electrode active material. Since this layer acts as a protective layer, in a battery using a positive electrode active material that has been subjected to surface treatment, a decrease in battery capacity and an increase in positive electrode resistance after cycle charge / discharge are reduced.

As an example of the improvement of the positive electrode active material as described above, in Non-Patent Document 1, ZrO ₂ is used on the surface of the positive electrode active material having a composition of LiNi _0.33 Mn _0.33 Co _0.33 O _2. It is disclosed to form a protective layer of metal oxide. In the same document, it is reported that the battery characteristics can be improved by forming the protective layer.

In Patent Document 1, by adding AlO (OH) and Al (OH) ₃ in the surface treatment layer of the positive electrode active material, excellent life characteristics and high discharge potential characteristics are imparted to a battery to which this is applied. It is stated that you can.

In Patent Document 2, by covering the particle surface of the positive electrode active material made of Li, Al, Co, and Ni with a compound containing Al, a region in which the concentration of Al continuously decreases from the particle surface toward the inside is disclosed. Producing technology has been proposed. This document states that this improves the thermal stability of the positive electrode active material.

Patent Document 3 discloses that a positive active material containing Ni, Co, and Mn is subjected to water treatment, brought into contact with an aqueous solution of a zirconium compound, and then heated at 600 to 1000 ° C. It has been reported that a positive electrode active material having discharge cycle durability can be obtained.

Patent Document 4 describes that the cycle characteristics are improved by coating the surface of the positive electrode with a metal oxide.

JP 2009-218217 A Japanese Patent Laid-Open No. 2001-196063 JP 2011-187174 A JP-A-8-236114

However, in Non-patent Document 1, Patent Document 1 and Patent Document 4, the crystal structure of the positive electrode active material cannot be stabilized only by forming a protective layer on the surface of the positive electrode active material. Therefore, the improvement of the battery characteristics is limited, especially when the battery is used / stored in high temperature or high pressure environment, the oxidative decomposition of the electrolyte on the positive electrode surface cannot be sufficiently suppressed, and the metal elution occurs on the positive electrode surface. Can happen.

Further, in Patent Document 2, it is necessary to add a large amount of Al to the positive electrode active material in order to further coat Al on the surface of the positive electrode active material containing Al. It is known that when Al is added, Li desorption and insertion characteristics in the positive electrode active material deteriorate. Therefore, in the technique of Patent Document 2, there is a problem that the capacity reduction of the positive electrode active material becomes large.

In Patent Document 3, since heat treatment is performed at a high temperature, Zr penetrates into the positive electrode active material, and the Zr concentration in the vicinity of the surface is diluted. Therefore, the improvement of battery characteristics is limited.

Regarding the above problems of the prior art, the first object of the present invention is to provide a non-aqueous secondary battery in which the increase in positive electrode resistance after cycle charge / discharge is suppressed and the decrease in battery capacity is small. It is to provide a positive electrode active material for a non-aqueous secondary battery, and a non-aqueous secondary battery using the positive electrode active material for a non-aqueous secondary battery.

The second object of the present invention is to provide a non-aqueous secondary battery having excellent storage characteristics in a high temperature and high voltage environment.

As a result of intensive studies on the above problems, the present inventors have formed the above first problem by forming a region containing a predetermined amount of Zr in the vicinity of the surface of the positive electrode active material having a core having a specific composition. The inventors have found that this can be solved and have reached the present invention.

Further, regarding the second problem, the present inventors, in a non-aqueous secondary battery, the positive electrode active material in the positive electrode has Zr and a predetermined functional group on the particle surface, and the non-aqueous electrolyte solution is The inventors have found that the second problem can be solved by adopting a configuration containing a predetermined compound, and have reached the present invention.

That is, the gist of the present invention 1 for solving the first problem resides in a positive electrode active material for a non-aqueous secondary battery that satisfies the following conditions (1) to (3).
(1) A lithium compound having a structure capable of desorbing and inserting Li ions, wherein the positive electrode active material core includes Ni, Co, and M (M is Mn and / or Al).
(2) A Zr-containing region containing all of Zr, Ni, Co, and M exists at a depth of 0.1 to 100 nm from the active material surface.
(3) The molar ratio of Zr to (Zr + Ni + Co + M) in the Zr-containing region is 1.5 to 30%.

Another aspect of the present invention is a nonaqueous solution comprising a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material for a nonaqueous secondary battery. It exists in the positive electrode for secondary batteries.

Another aspect of the present invention is a nonaqueous secondary battery including a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and a nonaqueous electrolyte, wherein the positive electrode is used for the nonaqueous secondary battery of the present invention. It exists in the non-aqueous secondary battery which is a positive electrode.

Further, the gist of the present invention 2 for solving the second problem is a non-aqueous secondary battery comprising at least a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte, wherein the positive electrode Zr and at least one group selected from the group consisting of a hydroxyl group, an aldehyde group, an alkoxy group, and a carboxyl group are present on the particle surface of the active material, and the non-aqueous electrolyte is carbon-carbon unsaturated. At least one compound selected from the group consisting of a cyclic carbonate having a bond, an isocyanate compound or a condensate thereof, a fluorinated oxo acid salt, a nitrile compound, an aromatic compound, a phosphonic acid ester compound, a halogen-containing cyclic carbonate, and an oxalate salt. In a non-aqueous secondary battery.

According to the positive electrode active material for a non-aqueous secondary battery of the present invention, a non-aqueous secondary battery in which deterioration of the positive electrode active material is small, increase in positive electrode resistance is suppressed, and decrease in battery capacity is small even after cycle charge / discharge. Can be provided.

Further, according to the present invention, it is possible to provide a non-aqueous secondary battery having excellent storage characteristics in a high temperature and high voltage environment.

Sections obtained from the positive electrode prepared in Example 1-1 were observed with a transmission electron microscope (TEM), and the results of elemental composition analysis with energy dispersive X-ray spectroscopy (EDS) at regular intervals are shown. Sections obtained from the positive electrode prepared in Comparative Example 1-1 were observed with a transmission electron microscope (TEM), and the results of analyzing the elemental composition with energy dispersive X-ray spectroscopy (EDS) at regular intervals are shown. The result of having performed charging / discharging 3 times about the nonaqueous secondary battery obtained using the positive electrode obtained by the reference examples 1 and 2, and analyzing the positive electrode in a battery by XPS after that is shown.

Hereinafter, embodiments of the present invention will be described in detail, but the description of the configuration described below is an example (representative example) of the embodiments of the present invention, and the present invention does not exceed the gist thereof. It is not limited to these contents.

Below, the positive electrode active material for nonaqueous secondary batteries of the present invention 1 that solves the first problem will be described first, and then the nonaqueous secondary battery of the present invention 2 that solves the second problem will be described. .

[Positive Electrode Active Material for Nonaqueous Secondary Battery of Invention 1]
First, the positive electrode active material for a non-aqueous secondary battery of the present invention 1 (hereinafter, also simply referred to as “the positive electrode active material of the present invention 1”) will be described. The positive electrode active material satisfies the predetermined conditions (1) to (3) as described above. In summary, the positive electrode active material has a specific composition as a positive electrode active material core, and there is a region containing Zr and all elements constituting the specific composition of the positive electrode active material core in the vicinity of the surface of the active material. In addition, the amount of Zr in the region is in a predetermined range. Hereinafter, the conditions (1) to (3) will be described in order.

<"(1) The positive electrode active material core is a lithium compound having a structure capable of desorbing and inserting Li ions, including Ni, Co and M (M is Mn and / or Al)">
The positive electrode active material core constituting the positive electrode active material for a non-aqueous secondary battery of the present invention 1 can desorb and insert Li ions containing Ni, Co and M (M is Mn and / or Al). It is a lithium compound having a simple structure.

Examples of the structure of the lithium compound include a spinel structure capable of three-dimensional diffusion and a layered structure capable of two-dimensional diffusion of lithium ions. Specific examples of lithium compounds that can have such a structure include LiNi _1-xy Co _x Mn _y O ₂ , LiNi _1-xy Co _x Al _y O ₂ , LiNi _1- _xy _z Co _x Mn _y Al _z O _{2 and the} like. x, y and z will be described below.

From the viewpoint of the size of the battery capacity, the element composition of the positive electrode active material core is Li _x Ni _1-yz-α Co _y Al _z M ′ _α O ₂ (M ′ is other than Li, Ni, Co, Al) It is preferable that it is one or more elements.

In the above formula, the value of x is usually 0.9 or more, preferably 0.92 or more, more preferably 0.95 or more, usually 1.1 or less, preferably 1.09 or less, more preferably 1.08 or less. is there.
The value of y is greater than 0, preferably 0.08 or more, more preferably 0.1 or more, usually 0.4 or less, preferably 0.3 or less, more preferably 0.25 or less.
The value of z is larger than 0, preferably 0.02 or more, more preferably 0.03 or more, usually 0.5 or less, preferably 0.25 or less, more preferably 0.1 or less.
The value of α is usually 0 or more, preferably 0.001 or more, more preferably 0.002 or more, usually 0.01 or less, preferably 0.007 or less, more preferably 0.005 or less. When M ′ is two or more elements, α represents the sum of the compositions of the elements included in M ′.

If x, y, z and α are within this range, a non-aqueous secondary battery obtained by using the positive electrode active material of the present invention 1 (hereinafter, also simply referred to as “non-aqueous secondary battery of the present invention 1”). A positive electrode active material excellent in thermal stability can be obtained without impairing the battery capacity.

From the above, x, y, z, and α are 0.9 ≦ x ≦ 1.1, 0 <y ≦ 0.4, 0 <z ≦ 0.5, and 0 ≦ α ≦ 0.01. preferable.

From the viewpoint of battery life, the element composition of the positive electrode active material core is Li _x Ni _1-yz-α Co _y Mn _z M ′ _α O ₂ (where M ′ is other than Li, Ni, Co, Mn). It is preferably one or more elements.

In the above formula, the value of x is usually 0.9 or more, preferably 0.92 or more, more preferably 0.95 or more, usually 1.1 or less, preferably 1.09 or less, more preferably 1.08 or less. is there.
The value of y is greater than 0, preferably 0.05 or more, more preferably 0.08 or more, usually 0.4 or less, preferably 0.37 or less, more preferably 0.35 or less.
The value of z is greater than 0, preferably 0.1 or more, more preferably 0.2 or more, usually 0.5 or less, preferably 0.45 or less, more preferably 0.4 or less.
The value of α is usually 0 or more, preferably 0.001 or more, more preferably 0.002 or more, usually 0.01 or less, preferably 0.007 or less, more preferably 0.005 or less. When M ′ is two or more elements, α represents the sum of the compositions of the elements included in M ′.

Within this range, the positive electrode active material can be produced at a low raw material cost without impairing the battery life of the nonaqueous secondary battery of the first invention.

In the composition formula of the positive electrode active material core, the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. Moreover, x in the said composition formula is a preparation composition in the manufacture stage of a lithium compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the amount of Li in the positive electrode active material may be reduced with charge and discharge. In that case, x may be measured as a numerical value in the range of 0.45 or more and 2 or less when discharged to 3 V in composition analysis.

(Element M ')
As described above, one or more elements M ′ other than Ni, Co, and M (M is Mn and / or Al) may be introduced into the positive electrode active material core. As the element M ′, B, Na, Mg, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te, Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si and Sn can be mentioned.

These elements M ′ may be incorporated into the crystal structure of the positive electrode active material core, or may not be incorporated into the crystal structure of the positive electrode active material core, and may be incorporated into the active material particle surface, crystal grain boundaries, or the like. It may be unevenly distributed as a compound.

<Regarding “(2) A Zr-containing region containing all of Zr, Ni, Co, and M is present at a depth of 0.1 to 100 nm from the active material surface”>
The positive electrode active material of the present invention 1 is a region containing all of Zr, Ni, Co, and M (M is Mn and / or Al) at a depth of 0.1 to 100 nm from the surface of the positive electrode active material (containing Zr) Area).

In the present invention, the phrase “having a Zr-containing region in the depth portion” means that there is a portion where Zr, Ni, Co, and M can be detected simultaneously at a depth of 0.1 to 100 nm from the surface of the positive electrode active material. Is defined as For example, in FIG. 1 showing the result of elemental analysis of Example 1-1 to be described later, since all the peaks of Zr, Ni, Co, and Mn can be confirmed at a depth of 5 nm from the surface of the positive electrode active material, FIG. It can be said that this positive electrode active material has a Zr-containing region at a depth of 5 nm from the surface of the positive electrode active material.

In the Zr-containing region, “a peak can be confirmed” means that there is a peak having a molar ratio of each element amount to the total element amount of 1.5% or more. For example, an extremely small peak having a molar ratio of 1.0% is not regarded as a peak when determining whether it corresponds to a Zr-containing region.

In addition, a state in which a plurality of arbitrary depths are selected in a region included in a depth of 0.1 to 100 nm from the surface of the positive electrode active material, and Zr, Ni, Co, and M detected at each arbitrary depth are combined. If only Zr, Ni, Co and M can be said to exist, it does not mean that the Zr-containing region in the present invention exists. For example, when a Zr peak is confirmed only at a depth of 5 nm from the surface of the positive electrode active material and Ni, Co, and Mn peaks are confirmed only at a depth of 10 nm from the surface of the positive electrode active material, a Zr-containing region exists. It can be said that it is not.

In the present invention 1, by using a positive electrode active material having a Zr-containing region, it is possible to extremely effectively suppress an increase in positive electrode resistance after cycle charge / discharge in the nonaqueous secondary battery of the present invention 1. It is. The following mechanism is assumed as this reason.

One of the deterioration forms of the positive electrode active material in the battery is known to be a change in crystal structure caused by the diffusion of Ni or Co constituting the positive electrode active material in the crystal structure of the positive electrode active material. It has been found that the crystal structure changes particularly easily in the vicinity of the surface of the positive electrode active material. Since this crystal structure change induces an increase in positive electrode resistance in the battery, it is a big problem in improving battery characteristics. In the present invention 1, by forming a Zr-containing region containing all of Zr, Ni, Co and M in the vicinity of the surface of the positive electrode active material, the diffusion of Ni and Co in the crystal structure is inhibited. It is considered that the change in the crystal structure can be suppressed, and as a result, the increase in positive electrode resistance after cycle charge / discharge is suppressed.

Further, when the Zr-containing region is formed in the vicinity of the surface of the positive electrode active material, the adverse effect on the capacity of the non-aqueous secondary battery using the positive electrode active material is small as compared with the case where Zr is added to the entire positive electrode active material. In addition, the adverse effect on the battery capacity can be kept small compared to the case where a similar region is formed using other elements such as Al. Although the detailed reason for obtaining such an effect is unknown, the following mechanism is presumed as the reason.

In other words, since the ion radius of Zr is very close to the ion of Li, the Zr ion can enter the crystal site occupied by the Li ion in the positive electrode active material without requiring a large amount of energy, and is stably Zr, Ni, A region containing all of Co and M is formed. As a result, the distortion of the crystal structure in this region is reduced, and the characteristics relating to the desorption and insertion of Li ions are not greatly impaired, so that it is considered that the battery capacity deterioration due to cycle charge / discharge can be suppressed to a small level.

The Zr-containing region may be only one or a plurality of regions may exist at a depth of 0.1 to 100 nm from the surface of the positive electrode active material. The presence of a plurality of regions means that, for example, all of Zr, Ni, Co, and M are contained in a portion having a depth of 5 to 10 nm, and at least one of these is not contained in a portion having a depth of 10 to 15 nm. , And at a depth of 15-20 nm, these are all contained.

The depth from the surface of the positive electrode active material where the Zr-containing region is formed is a portion of 0.1 to 100 nm as described above, preferably a portion of 0.2 to 70 nm, and more preferably 0.3 to It is a part of 60 nm. When the depth at which the Zr-containing region is formed is shallow, the effect of suppressing the change in the crystal structure of the positive electrode active material is reduced, and when the depth is deep, the battery capacity is greatly deteriorated.

Note that the depth at which the Zr-containing region exists can be measured, for example, by the following method. That is, a slice is prepared using a focused ion beam (FIB) from a positive electrode manufactured by applying a slurry containing a positive electrode active material to a current collector. The section is observed with a transmission electron microscope (TEM). The elemental composition is analyzed by energy dispersive X-ray spectroscopy (EDS) at regular intervals from the observed surface portion of the positive electrode active material toward the inside. At this time, in the vicinity of the surface of the positive electrode active material, the point at which at least one of the constituent elements of the positive electrode active material core is detected for the first time is taken as the surface of the positive electrode active material, and the depth can be measured as the distance from that point. As described above, the Zr-containing region is a region in which the molar ratios of the element amounts of Zr, Ni, Co, and M to the total element amount are all 1.5% or more.

<Regarding “(3) The molar ratio of Zr to (Zr + Ni + Co + M) in the Zr-containing region is 1.5 to 30%”>
In the positive electrode active material of the present invention 1, in the Zr-containing region, the molar ratio of Zr to the total of four (Zr + Ni + Co + M) elements (5 when M is Mn and Al) is 1.5-30. %. The molar ratio is preferably 1.6 to 30%, more preferably 1.8 to 20%, and further preferably 2 to 15%. When the molar ratio of Zr is small, the effect of suppressing the crystal structure change of the positive electrode active material becomes small (although it is not called a Zr-containing region if it is less than 1.5%). On the other hand, when the molar ratio of Zr is large, the battery capacity is greatly deteriorated due to cycle charge / discharge, and the Zr-containing region causes a large positive electrode resistance.

Also, in the portion farthest from the surface and deeper than the portion where the Zr-containing region exists, the molar ratio of Zr to (Zr + Ni + Co + M) should be small. The molar ratio is usually 1.2% or less, preferably 1% or less, particularly preferably 0.8% or less. If the molar ratio of Zr in the deep part is larger than this range, the battery capacity may be deteriorated.

Further, the molar ratio of Zr in the Zr-containing region is obtained as an average value of the molar ratio of Zr to (Zr + Ni + Co + M) at each measurement point in the Zr-containing region (existing over a certain depth range) measured by the above method. Can do.

The positive electrode active material of the present invention 1 satisfies the conditions (1) to (3) described above. The positive electrode active material preferably satisfies at least one of the characteristics described below.

(Volume-based average particle size)
The volume-based average particle diameter of the positive electrode active material of the present invention 1 is a volume-based average particle diameter (median diameter) obtained by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. It is preferably 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

If the volume-based average particle size is below the above range, it may be difficult to control the liquidity of the slurry applied to the positive electrode current collector when the positive electrode is manufactured. Moreover, when it exceeds the said range, there exists a possibility that positive electrode resistance may increase in a battery.

Measure the volume-based average particle size as follows. The positive electrode active material is dispersed in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant. The obtained dispersion is measured using a laser diffraction / scattering particle size distribution analyzer (for example, LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the positive electrode active material of the first invention.

(BET specific surface area)
BET specific surface area of the positive electrode active material of the present invention 1 is a measured specific surface area using the BET method is usually 0.01 m ² · ^{g -1} or more, 0.05 m ² · ^{g -1} or more, 0 .1m ² · ^{g -1} or more, and also generally not more than ^{10 m} 2 · ^{g -1,} preferably from ^{5 m} 2 · ^{g -1} or less, more preferably ^3m 2 · ^{g -1} or less.

If the BET specific surface area is less than this range, the lithium acceptability may deteriorate during charging when used as a positive electrode material, and battery stability may be reduced. On the other hand, if it exceeds this range, the reactivity with the non-aqueous electrolyte may increase when used as the positive electrode material. In this case, gas generation increases and a preferable nonaqueous secondary battery may not be obtained.

The measurement of the specific surface area by the BET method is performed using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken). Specifically, after the sample was preliminarily dried at 350 ° C. for 15 minutes under a nitrogen flow, a nitrogen-helium mixed gas that was accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure was 0.3 was obtained. The specific surface area is measured by the nitrogen adsorption BET one-point method using the gas flow method.

(Tap density)
The tap density of the positive electrode active material of the present invention 1 is usually 0.1 g · cm ⁻³ or more, preferably 0.5 g · cm ⁻³ or more, more preferably 0.7 g · cm ⁻³ or more, and 1 g · cm. particularly preferably ³ or more, and is preferably 5 g · ^{cm -3} or less, 4g · ^{cm -3} and more preferably less, 3.5 g · ^{cm -3} or less are particularly preferred.

If the tap density is below the above range, the packing density is difficult to increase when used as a positive electrode, and a high-capacity non-aqueous secondary battery may not be obtained. Moreover, when it exceeds the said range, the space | gap between the particles in an electrode will decrease, the electroconductivity between particles will not be ensured, and a favorable battery characteristic may not be acquired.

The tap density is measured as follows. The sample is passed through a sieve having an opening of 300 μm, and the sample is dropped into a 20 cm ³ tapping cell to fill the sample up to the upper end surface of the cell. Thereafter, tapping with a stroke length of 10 mm is performed 1000 times using a powder density measuring instrument (for example, tap denser manufactured by Seishin Enterprise Co., Ltd.), and the tap density is calculated from the sample volume and the sample mass at that time.

[Method for Producing Cathode Active Material of Invention 1]
Hereinafter, an example of a method for producing a positive electrode active material for a non-aqueous secondary battery of the present invention 1 will be described. As long as a positive electrode active material that does not depart from the gist of the present invention 1 can be obtained, any production method can be used to produce the positive electrode active material. A substance may be produced.

The positive electrode active material of the present invention 1 can be produced through two processing steps. That is,
Mixing the positive electrode active material core and the Zr-containing surface treatment material in a dispersion medium under appropriate conditions to form a bond between the Zr-containing surface treatment material and the surface of the positive electrode active material core; and
A step of allowing Zr bonded to the surface of the positive electrode active material core to penetrate into the vicinity of the surface of the positive electrode active material core by performing heat treatment under a specific temperature condition;
It is. Hereinafter, each step will be described.

<Positive electrode active material core and Zr-containing surface treatment material are mixed in a dispersion medium under appropriate conditions to form a bond between the Zr-containing surface treatment material and the surface of the positive electrode active material core>
The positive electrode active material core is not particularly limited as long as it is a lithium compound that becomes the positive electrode active material core described above. Such a lithium compound can be obtained by a production method described in, for example, Japanese Patent Application Laid-Open Nos. 2010-92848 and 2001-196063.

The Zr surface treatment material is not particularly limited as long as it is a compound containing Zr. The material is a compound that is activated under specific conditions, such as addition of a catalyst or a reaction initiator, stimulation by light or heat, in order to efficiently form a bond with the surface of the positive electrode active material core. Is preferred. Specifically, such compounds include Zr (OC ₂ H ₅ ) ₄ , Zr (OC ₃ H ₇ ) ₄ , Zr (OCH (CH ₃ ) ₂ ) ₄ , Zr (OC ₄ H ₁₀ ) ₄ , ZrCl _4. Etc.

The mixing amount of the Zr-containing surface treatment material is usually 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, usually 3 parts by mass with respect to 100 parts by mass of the positive electrode active material core. Part or less, preferably 2 parts by weight or less, more preferably 1.5 parts by weight or less. If it is the said range, since the increase suppression effect of the positive electrode resistance after cycle charging / discharging by surface treatment will be acquired, without causing the fall of battery capacity, it is preferable.

The dispersion medium for mixing the positive electrode active material core and the Zr-containing surface treatment material is not particularly limited as long as it has an affinity for the positive electrode active material core and can dissolve the Zr-containing surface treatment material. Specific examples of such a dispersion medium include water, methanol, ethanol, propanol, isopropanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, acetone and the like.

The mixing amount of the dispersion medium is usually 20 parts by mass or more, preferably 30 parts by mass or more, more preferably 40 parts by mass or more, usually 200 parts by mass or less, preferably 180 parts by mass or less with respect to 100 parts by mass of the positive electrode active material core. More preferably, it is 150 parts by mass or less. If it is the said range, since a Zr containing surface treatment material and the surface of a positive electrode active material core can be formed uniformly, without making manufacturing cost high, it is preferable.

The dispersion medium preferably contains a catalyst for activating the Zr-containing surface treatment material, and water is particularly preferable in terms of high activation ability. The addition amount of the catalyst is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and particularly preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material core. If the amount of catalyst added is small, bond formation between the surface of the positive electrode active material core and the Zr-containing surface treatment material does not proceed sufficiently. Moreover, when there is too much catalyst addition amount, there exists a possibility that Zr containing surface treatment material may raise | generate self-association. Note that when the dispersion medium is water, the water functions as both the dispersion medium and the catalyst.

In the mixing process of the positive electrode active material core and the Zr-containing surface treatment material, in order to sufficiently activate the Zr-containing surface treatment material and promote bond formation between the positive electrode active material core surface and the Zr-containing surface treatment material, It is preferable to heat. The temperature at that time is preferably 30 to 100 ° C., and 40 to 80 ° C. is particularly preferable from the viewpoint of processing efficiency.

The mixing time of the positive electrode active material core and the Zr-containing surface treatment material is preferably 5 minutes to 3 hours, more preferably 20 minutes to 2 hours, and particularly preferably 30 to 90 minutes. If the mixing time is too short, bond formation between the positive electrode active material core surface and the Zr-containing surface treatment material may not proceed sufficiently. On the other hand, if the mixing time is too long, Li is liberated from the positive electrode active material core, which may cause deterioration of the positive electrode active material core.

<Step of allowing Zr bonded to the surface of the positive electrode active material core to penetrate into the vicinity of the surface of the positive electrode active material core by heat treatment under specific temperature conditions>
After mixing the positive electrode active material core and the Zr-containing surface treatment material, heat treatment is performed under specific temperature conditions in order to infiltrate Zr from the surface of the positive electrode active material core and form a Zr-containing region. The temperature at that time is preferably more than 100 ° C. and less than 500 ° C., particularly preferably 110 ° C. or more and less than 450 ° C. If the temperature is too low, the Zr-containing ratio in the portion that becomes the Zr-containing region may be insufficient. On the other hand, when the temperature is too high, the penetration of Zr into the positive electrode active material core proceeds excessively, and the battery capacity may be deteriorated.

Particularly when the temperature is 600 ° C. or higher, the penetration of Zr into the positive electrode active material is promoted, and the amount of Zr near the surface becomes insufficient. As a result, a positive electrode active material that satisfies the gist of the present invention cannot be obtained.

The heat treatment time is preferably 30 minutes to 10 hours, more preferably 45 minutes to 8 hours, and particularly preferably 1 to 7 hours. If the heat treatment time is too short, the Zr-containing ratio in the portion that becomes the Zr-containing region may be insufficient, and if it is too long, the production cost may be too high.

Note that the heat treatment may be performed under reduced pressure conditions, or after preliminarily performing the treatment under reduced pressure conditions, the main treatment may be performed at a higher temperature.

In this stage, it is particularly preferable to preliminarily heat at a temperature not lower than 105 ° C. and not higher than 150 ° C., preferably not lower than 110 ° C. and not higher than 140 ° C. The time for preliminary heating under reduced pressure is usually 1 to 10 hours, preferably 2 to 9 hours. The atmosphere in the furnace during the heat treatment may be air, or the oxygen partial pressure may be higher than that of air.

[Positive electrode for non-aqueous secondary battery of the present invention 1]
Using the positive electrode active material for a non-aqueous secondary battery of the present invention 1, a positive electrode for a non-aqueous secondary battery (hereinafter also simply referred to as “the positive electrode of the present invention 1”) can be produced. The positive electrode of the present invention 1 includes a positive electrode current collector and a positive electrode active material layer including the positive electrode active material of the present invention 1 formed on the positive electrode current collector.

The positive electrode active material layer is usually prepared by dry mixing a positive electrode active material (which is the positive electrode active material of the present invention 1), a binder, and a conductive material and a thickener used as necessary. It is produced by pressure-bonding a sheet shape to a positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, and the slurry is applied to the positive electrode current collector and dried.

The positive electrode current collector is usually formed of a metal material such as aluminum, stainless steel, nickel plating, titanium, or tantalum, or a carbon material such as carbon cloth or carbon paper. As the shape of the positive electrode current collector, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc. A carbon thin film, a carbon cylinder, etc. are mentioned. In addition, you may form a thin film suitably in mesh shape.

When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but a range of usually 1 μm or more and 100 μm or less is suitable. If it is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

As the binder used for producing the positive electrode active material layer, those conventionally used for producing the positive electrode active material layer can be used without any particular limitation. When the active material layer is produced by a coating method, the binder may be any material that is stable with respect to the liquid medium used at the time of manufacturing the positive electrode.

Specific examples thereof include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, resin polymers such as nitrocellulose,
Rubber polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber,
Styrene / butadiene / styrene block copolymer and hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene styrene block copolymer and the like Thermoplastic elastomeric polymers such as hydrogenated products,
Soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer,
Fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer,
Examples thereof include a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions).

In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more and 80% by mass or less. If the ratio of the binder is low, the positive electrode active material cannot be sufficiently retained, and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. On the other hand, if the ratio is high, battery capacity and conductivity may be reduced.

The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type. Specific examples of the conductive material include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and carbon materials such as amorphous carbon such as needle coke. be able to.

In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by mass or more and 50% by mass or less. If the ratio of the conductive material is low, the conductivity may be insufficient. Conversely, when the ratio is high, the battery capacity may decrease.

<Thickener>
When an aqueous solvent is used for the slurry used for forming the positive electrode active material layer, it is preferable to form a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry. Specific examples of the thickener include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

When a thickener is further added, the proportion of the thickener in the positive electrode active material layer is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. Moreover, it is added so that it may become normally 5 mass% or less, Preferably it is 3 mass% or less, More preferably, it is the range of 2 mass% or less. When it is in the above range, good coatability can be obtained, and a decrease in battery capacity and an increase in resistance can be suppressed.

As the liquid medium for forming the slurry, it is possible to dissolve or disperse the positive electrode active material of the present invention 1, which is a positive electrode forming material, the binder, and the conductive material and thickener used as necessary. There are no particular restrictions on the type of the solvent. As the liquid medium, either an aqueous solvent or an organic solvent may be used.

Examples of the aqueous solvent include water and alcohol.
Examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF) Toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.

The content ratio of the positive electrode active material of the present invention 1 in the positive electrode active material layer is usually 10% by mass or more and 99.9% by mass or less. If the proportion of the active material in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.

The thickness of the positive electrode active material layer is usually about 10 to 200 μm.
The electrode density after pressing of the positive electrode is usually 2.2 g / cm ³ or more and 4.2 g / cm ³ or less.

The positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material of the first invention. In addition, the temperature at the time of roller press may be room temperature, and may be heated if it is below the thermal decomposition temperature of the said binder.

Thus, the positive electrode for a non-aqueous secondary battery of the first invention can be prepared.

[Non-aqueous secondary battery]
<Battery configuration>
By using the positive electrode for a non-aqueous secondary battery according to the first aspect described above, an increase in positive electrode resistance is suppressed even after cycle charge / discharge, and a non-aqueous secondary battery with a small decrease in battery capacity is manufactured. Can do. Here, the nonaqueous secondary battery (nonaqueous secondary battery of the present invention 1) obtained by using the positive electrode of the present invention 1 generally has a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and nonaqueous electrolysis. It has liquid.

Of these, the positive electrode is as described above. The configuration of the negative electrode, the separator and the outer case that are usually provided in the non-aqueous secondary battery, and the configuration of the electrode group are the same as the corresponding configurations of the non-aqueous secondary battery of the present invention 2 described later. Hereinafter, the nonaqueous electrolytic solution will be described.

<Non-aqueous electrolyte>
As the non-aqueous electrolyte in the non-aqueous secondary battery of the present invention 1, a non-aqueous electrolyte conventionally used in non-aqueous secondary batteries can be used without particular limitation. The nonaqueous electrolytic solution usually contains a known electrolyte, an organic solvent, and an additive.

(Electrolytes)
As the electrolyte, a lithium salt is usually used. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiTaF ₆ , LiWF ₇ , lithium tungstates, lithium carboxylates, sulfonic acid lithium salts, lithium imide salts, lithium metide salts, lithium oxalates. Latoborate salts, lithium oxalatophosphate salts, fluorine-containing organic lithium salts and the like can be mentioned. These lithium salts may be used alone or in combination of two or more.

(Organic solvent)
Examples of the organic solvent include cyclic carbonates having no fluorine atom, chain carbonates, cyclic and chain carboxylic acid esters, ether compounds, and sulfone compounds. These organic solvents may be used alone or in combination of two or more.

(Additive)
Examples of the additive include a cyclic carbonate having a fluorine atom, a cyclic carbonate having a carbon-carbon unsaturated bond, a cyclic sulfonate ester, a compound having an isocyanate group, and a compound having a cyano group. These additives may be used alone or in combination of two or more.

Furthermore, various specific additives and additives other than the specific additives described in the non-aqueous electrolyte solution in the non-aqueous secondary battery of the present invention 2 described later can also be employed.

As described above, the nonaqueous secondary battery of the first aspect of the present invention includes the positive electrode for the nonaqueous secondary battery of the first aspect of the present invention obtained by using the positive electrode active material for the nonaqueous secondary battery of the first aspect of the present invention. Yes. In the positive electrode active material, the positive electrode active material core has a specific composition and has a Zr-containing region. With these configurations, even if the nonaqueous secondary battery of the first aspect of the present invention is subjected to cycle charge / discharge, an increase in positive electrode resistance is suppressed and a decrease in battery capacity is also suppressed.

Next, the non-aqueous secondary battery of the present invention 2 that solves the second problem will be described below.

[Nonaqueous Secondary Battery of Invention 2]
The non-aqueous secondary battery of the second aspect of the present invention includes at least a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte. Zr and at least one group selected from the group consisting of a hydroxyl group, an aldehyde group, an alkoxy group, and a carboxyl group are present on the particle surface of the positive electrode active material. The non-aqueous electrolyte includes a cyclic carbonate having a carbon-carbon unsaturated bond, an isocyanate compound or a condensate thereof, a fluorinated oxoacid salt, a nitrile compound, an aromatic compound, a phosphonic acid ester compound, a halogen-containing cyclic carbonate, And at least one compound selected from the group consisting of oxalate salts (hereinafter also referred to as “specific additives”).

The reason why the non-aqueous secondary battery of the present invention 2 has an effect of solving the second problem is not clear, but the following mechanism is presumed as the reason. That is, it is considered that the Zr-containing layer on the surface of the positive electrode active material, which will be described later, reacts with the specific additive in the non-aqueous electrolyte prior to the positive electrode active material. Hereinafter, each structure of the non-aqueous secondary battery of this invention 2 is demonstrated.

[Positive electrode active material]
The positive electrode active material used in the nonaqueous secondary battery of the present invention 2 is characterized in that Zr is present on the particle surface. A Zr-containing layer containing Zr is formed on the particle surface.

The positive electrode active material has a lithium transition metal oxide having a structure capable of desorbing and inserting Li ions as a core particle. Examples of the transition metal in the lithium transition metal oxide include at least one selected from the group consisting of cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe).

Examples of the structure of the lithium transition metal oxide include a spinel structure, a layered structure, and an olivine structure. Especially, the lithium transition metal oxide which can take a structure like a following formula is preferable from the point which can make the energy density of a non-aqueous secondary battery high.

Li _s M ″ _1- _{t At} O ₂ (1)
(In the formula, M ″ represents at least two elements selected from the group consisting of lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn). A represents Li, Ni, Co, and Mn. A is an element other than, for example, A, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru for improving battery performance. , Rh, Pd, Ag, In, Sb, Te, Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb, Lu, Bi, N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si, and Sn.

In the above formula, from the viewpoint of the battery capacity, 0.8 ≦ s ≦ 1.3, 0 ≦ t ≦ 0.2, preferably 0.9 ≦ s ≦ 1.2, 0 ≦ t ≦ 0 Within the range of .1. The composition formula of the lithium transition metal oxide is a composition at the production stage of the lithium transition metal oxide, and the amount of Li in the positive electrode active material or the charge / discharge of the nonaqueous secondary battery of the second aspect of the invention is as follows. The amount of oxygen may be impaired.

<Zr-containing layer>
The positive electrode active material used for the non-aqueous secondary battery of the present invention 2 has a Zr-containing layer containing Zr on the particle surface. The Zr-containing layer is provided on at least a part of the surface of the lithium transition metal oxide serving as the core particle of the positive electrode active material, and has an element or composition ratio different from that of the lithium transition metal oxide serving as the core particle. Is. The Zr-containing layer may exist in a form having a concentration change of constituent elements from the surface of the lithium transition metal oxide serving as the core particle toward the inside, or on the surface of the lithium transition metal oxide serving as the core particle. It may be scattered. Note that the Zr-containing layer may have nano-sized pores.

When a Zr-containing layer is formed on the surface of the positive electrode active material, a non-aqueous secondary battery with better battery characteristics can be obtained than when Zr is added to the entire positive electrode active material. The reason why such an effect is obtained is unknown, but the following is estimated as the reason. When the Zr-containing layer is present, the concentration of Zr ions is high near the surface of the lithium transition metal oxide. Since Zr ions have a great effect of suppressing the oxidation reaction between the positive electrode and the electrolyte, it is considered that a non-aqueous secondary battery with good battery characteristics can be obtained by using the positive electrode active material.

The thickness of the Zr-containing layer is usually from 0.1 to 100 nm, preferably from 0.2 to 70 nm, more preferably from 0.3 to 60 nm. If the thickness of the Zr-containing layer is too small, the effect of suppressing physical contact between the lithium transition metal oxide and the electrolytic solution may be reduced. If the thickness is too large, the movement of lithium ions becomes slow, which may increase the resistance of the positive electrode.

In the present invention, the presence or absence of the Zr-containing layer can be determined by the following method, for example. That is, analysis is performed by X-ray photoelectron spectroscopy (XPS) using a positive electrode produced by applying a positive electrode active material to a current collector or a positive electrode after charge / discharge as a sample. When a peak in the vicinity of 182 eV attributed to Zr is observed from the surface of the positive electrode, this means that a Zr-containing layer exists.

The molar ratio of Zr in the portion where Zr exists, that is, Zr in the Zr-containing layer existing on the particle surface of the positive electrode active material in all transition metals present in the portion is usually 1.5 to 30%. When the molar ratio is within this range, the change in the crystal structure of the positive electrode active material can be suppressed to prevent an increase in positive electrode resistance, and the battery capacity does not deteriorate.

<Surface functional group>
The positive electrode active material has at least one group selected from the group consisting of a hydroxyl group, an aldehyde group, an alkoxy group, and a carboxyl group on the particle surface. Since the positive electrode active material has such a predetermined surface functional group, the reactivity with the electrolytic solution is high, and in this reaction, resistance increase and volume expansion of the nonaqueous secondary battery are unlikely to occur. Such surface functional groups are present in the lithium transition metal oxide and / or Zr-containing layer in the vicinity of the surface of the positive electrode active material.

The presence of these surface functional groups can be confirmed by thermal desorption-GC / MS analysis. Specifically, a predetermined compound derived from a surface functional group generated by thermal desorption can be detected by GC / MS analysis.

The carbon number of the compound derived from the surface functional group that can be confirmed by thermal desorption-GC / MS analysis is usually 1 or more, preferably 3 or more, usually 20 or less, preferably 10 or less. Within this range, excessive gas generation due to side reactions in the battery can be suppressed without reducing the reactivity with the non-aqueous electrolyte. Specific examples of the compound include 1-propanol, 2-propanol, 2-methyl-1-propanol, 1-phenyl-2-methyl-2-propanol, 3-phenyl-1-propanol, propanal, 2-methylprop And compounds such as panal and 3-phenyl-2-methylpropanal.

The positive electrode active material in the non-aqueous secondary battery of the present invention 2 described above preferably satisfies at least one of the characteristics described below.

(Volume-based average particle size)
The positive electrode active material may be primary particles or secondary particles composed of primary particles. The volume-based average particle diameter of the positive electrode active material is a volume-based average particle diameter (median diameter) determined by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, Usually, it is 100 micrometers or less, 50 micrometers or less are preferable, 40 micrometers or less are more preferable, and 30 micrometers or less are still more preferable.

If the volume-based average particle size is below the above range, it may be difficult to control the liquidity of the slurry applied to the positive electrode current collector when the positive electrode is manufactured. Moreover, when it exceeds the said range, positive electrode resistance may increase in a battery.

Measure the volume-based average particle size as follows. A positive electrode active material is dispersed in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and this is used as a sample for a laser diffraction / scattering particle size distribution analyzer (for example, , Using a Horiba LA-920). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the positive electrode active material.

(BET specific surface area)
BET specific surface area of the positive electrode active material, with the measured specific surface area using the BET method is usually 0.01 m ² · ^{g -1} or more, preferably 0.05 m ² · ^{g -1} or more, 0.1 m ² · g ^-1 or more, and also generally not more than ^{10 m} 2 · ^{g -1,} preferably from ^{5 m} 2 · ^{g -1} or less, more preferably ^3m 2 · ^{g -1} or less.

If the BET specific surface area is less than this range, the lithium acceptability may deteriorate during charging when used as a positive electrode material, and therefore battery performance may be reduced. On the other hand, if it exceeds this range, when used as a positive electrode material, the reactivity with the non-aqueous electrolyte increases, gas generation increases, and a preferred non-aqueous secondary battery may not be obtained.

The measurement of the specific surface area by the BET method is performed using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken). After pre-drying the sample for 15 minutes at 150 ° C. under a nitrogen flow, using a nitrogen helium mixed gas that was accurately adjusted so that the relative pressure of nitrogen with respect to atmospheric pressure was 0.3, The specific surface area is measured by the nitrogen adsorption BET one-point method by the flow method.

(Tap density)
The tap density of the positive electrode active material is usually 0.5 g · cm ⁻³ or more, preferably 1.0 g · cm ⁻³ or more, more preferably 1.5 g · cm ⁻³ or more, and 2 g · cm ⁻³ or more. Particularly preferred. If the tap density is below the above range, the packing density is difficult to increase when used as a positive electrode, and a high-capacity non-aqueous secondary battery may not be obtained.

The tap density is measured as follows. The sample passed through a sieve having an opening of 150 μm is dropped into a 20 cm ³ tapping cell to fill the sample up to the upper end surface of the cell. Thereafter, tapping with a stroke length of 10 mm is performed 1000 times using a powder density measuring instrument (for example, tap denser manufactured by Seishin Enterprise Co., Ltd.), and the tap density is calculated from the sample volume and the sample mass at that time.

<Method for producing positive electrode active material having Zr-containing layer and surface functional group>
Next, an example of a method for producing a positive electrode active material having a Zr-containing layer and a predetermined surface functional group, which is used in the nonaqueous secondary battery of the present invention 2, will be described. The positive electrode active material may be obtained by any manufacturing method as long as it does not depart from the gist of the present invention.

The positive electrode active material can be manufactured through two processing steps. That is,
A step of forming a bond between the Zr-containing surface treatment material and the surface of the raw material positive electrode active material by mixing the raw material positive electrode active material serving as a nucleus and the Zr-containing surface treatment material in a dispersion medium under appropriate conditions ( Stage 1), and
In this step, the dispersion medium is removed by heat treatment under a specific temperature condition, and the bond between the Zr-containing surface treatment material and the surface of the raw material positive electrode active material is strengthened (step 2). Hereinafter, each step will be described.

(Stage 1)
The raw material positive electrode active material is not particularly limited as long as it is a lithium transition metal oxide. The lithium transition metal oxide can be obtained, for example, by a production method described in JP 2010-92848 A, JP 2001-196063 A, or the like.

The Zr surface treatment material is not particularly limited as long as it is a compound containing Zr. The material may be a compound that is activated under specific conditions such as addition of a catalyst or reaction initiator, stimulation by light or heat, etc. in order to efficiently form a bond with the surface of the raw material positive electrode active material. preferable. Specific examples of such compounds include Zr (OC ₂ H ₅ ) ₄ , Zr (OC ₃ H ₇ ) ₄ , Zr (OCH (CH ₃ ) ₂ ) ₄ , Zr (OC ₄ H ₁₀ ) ₄ , ZrCl _{4 and the} like. Is mentioned.

The mixing amount of the Zr-containing surface treatment material is usually 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more, usually 3 parts by mass with respect to 100 parts by mass of the raw material positive electrode active material. Part or less, preferably 2 parts by weight or less, more preferably 1.5 parts by weight or less. If it is the said range, since the increase suppression effect of the positive electrode resistance by surface treatment is acquired, without causing the fall of battery capacity, it is preferable.

The dispersion medium for mixing the raw material positive electrode active material and the Zr-containing surface treatment material is not particularly limited as long as it has an affinity for the raw material positive electrode active material and can dissolve the Zr-containing surface treatment material. Examples of such a dispersion medium include water, methanol, ethanol, propanol, isopropanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and acetone.

The mixing amount of the dispersion medium is usually 20 parts by mass or more, preferably 30 parts by mass or more, more preferably 40 parts by mass or more, usually 200 parts by mass or less, preferably 180 parts by mass or less with respect to 100 parts by mass of the raw material positive electrode active material. More preferably, it is 150 parts by mass or less. If it is the said range, since a bond can be uniformly formed between the Zr containing surface treatment material and the surface of a raw material positive electrode active material, without raising manufacturing cost, it is preferable.

The dispersion medium preferably contains a catalyst for activating the Zr-containing surface treatment material, and water is particularly preferable in terms of high activation ability. The addition amount of the catalyst is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, and particularly preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the raw material positive electrode active material. When the catalyst content is low, bond formation between the surface of the raw material positive electrode active material and the Zr-containing surface treatment material does not proceed sufficiently. On the other hand, if the content is too large, the Zr-containing surface treatment material may cause self-association. Note that when the dispersion medium is water, the water functions as both the dispersion medium and the catalyst.

In the mixing process of the raw material positive electrode active material and the Zr-containing surface treatment material, in order to sufficiently activate the Zr-containing surface treatment material and promote bond formation between the raw material positive electrode active material surface and the Zr-containing surface treatment material, It is preferable to heat. The temperature at that time is preferably 30 to 100 ° C., and 40 to 80 ° C. is particularly preferable from the viewpoint of processing efficiency.

The mixing time of the raw material positive electrode active material and the Zr-containing surface treatment material is preferably 5 minutes to 3 hours, more preferably 20 minutes to 2 hours, and particularly preferably 30 to 90 minutes. If the mixing time is too short, bond formation between the surface of the raw material positive electrode active material and the Zr-containing surface treatment material may not proceed sufficiently. On the other hand, if the mixing time is too long, Li may be liberated from the raw material positive electrode active material and the resulting positive electrode active material may be deteriorated.

(Stage 2)
After mixing the core positive electrode active material and the Zr-containing surface treatment material, in Step 2, the dispersion medium is removed and the bond between the Zr-containing surface treatment material and the surface of the positive electrode active material is strengthened. In order to achieve this, heat treatment is performed under specific temperature conditions.

The temperature of the heat treatment is preferably more than 80 ° C. and less than 500 ° C., particularly preferably 100 ° C. or more and less than 400 ° C. If the temperature is too low, the dispersion medium may not be sufficiently removed, or the bonding between the Zr-containing surface treatment material and the surface of the raw material positive electrode active material may be insufficient. On the other hand, if the temperature is too high, Zr permeates into the raw material positive electrode active material, which may cause deterioration of battery capacity.

The heat treatment time is preferably 30 minutes to 10 hours, more preferably 45 minutes to 8 hours, and particularly preferably 1 to 7 hours. If the heat treatment time is too short, there is a risk that the dispersion medium may not remain or be bonded as described above. On the other hand, if the heat treatment is too long, the production cost may be too high.

In this stage 2, it is particularly preferable to preheat at a temperature of usually 105 ° C. to 150 ° C., preferably 110 ° C. to 140 ° C. under reduced pressure. The time for preliminary heating under reduced pressure is usually 1 to 10 hours, preferably 2 to 9 hours. The atmosphere in the furnace during the heat treatment may be air, or the oxygen partial pressure may be higher than that of air.

[Positive electrode for non-aqueous secondary batteries]
The positive electrode for a non-aqueous secondary battery used in the non-aqueous secondary battery according to the second aspect of the present invention is obtained by forming a positive electrode active material layer containing a positive electrode active material and a binder described above on a current collector. It is. The configuration of the positive electrode in the nonaqueous secondary battery of the present invention 2 is the same as that of the present invention 1 except that the positive electrode active material having the Zr-containing layer and the surface functional group described above is used as the positive electrode active material in the positive electrode active material layer. This is the same as the positive electrode for a non-aqueous secondary battery in the non-aqueous secondary battery.

[Non-aqueous electrolyte]
Nonaqueous electrolytes used in the production of the nonaqueous secondary battery of the present invention 2 include cyclic carbonates having a carbon-carbon unsaturated bond, isocyanate compounds or condensates thereof, fluorinated oxoacid salts, nitrile compounds, aromatics There is no particular limitation as long as it contains at least one compound (specific additive) selected from the group consisting of a group compound, a phosphonic acid ester compound, a halogen-containing cyclic carbonate, and an oxalate salt. This is combined with known electrolytes, organic solvents, and other additives as required, which are usually used for non-aqueous electrolytes, to form non-aqueous electrolytes. The electrolyte and the organic solvent are respectively the same as the electrolyte and the organic solvent constituting the nonaqueous electrolytic solution in the nonaqueous secondary battery of the first aspect described above.

The non-aqueous secondary battery of the present invention 2 includes the positive electrode active material having the Zr-containing layer and the surface functional group described above and the non-aqueous electrolyte containing a specific additive. Due to such a configuration, even when stored in a high temperature and high voltage environment, the non-aqueous secondary battery has a small increase in volume and resistivity. Hereinafter, the specific additive will be described in order.

<Cyclic carbonate having a carbon-carbon unsaturated bond>
The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter sometimes referred to as “unsaturated cyclic carbonate”) is a cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond. There is no restriction | limiting in particular, Arbitrary unsaturated carbonates can be used. The cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.

Examples of unsaturated cyclic carbonates include vinylene carbonates, aromatic carbonates, ethylene carbonates substituted with a substituent having a carbon-carbon double bond or carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, Catechol carbonates etc. are mentioned.

Examples of the vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate, 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5 A fluoro vinylene carbonate etc. are mentioned.

Specific examples of the ethylene carbonates substituted with a substituent having the aromatic ring or carbon-carbon double bond or carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5 -Vinylethylene carbonate, 4-allyl-5-vinylethylene carbonate, ethynylethylene carbonate, 4,5-diethynylethylene carbonate, 4-methyl-5-ethynylethylene carbonate, 4-vinyl-5-ethynylethylene carbonate, 4- Allyl-5-ethynylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate Boneto, 4,5 diallyl carbonate, 4-methyl-5-allyl carbonate and the like.

Among these, preferable unsaturated cyclic carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene. Carbonate, vinylethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate, 4-allyl- 5-vinylethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl 5-ethynyl ethylene carbonate.

Among these, vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate are more preferable because they form a particularly stable interface protective film, and vinylene carbonate and vinyl ethylene carbonate are particularly preferable.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 80 or more, more preferably 85 or more, and preferably 250 or less, more preferably 150 or less. If it is this range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to a non-aqueous electrolyte, and the effect of this invention will fully be expressed easily.

The production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method. It is also commercially available.

Unsaturated cyclic carbonates may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The content of the unsaturated cyclic carbonate is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and further preferably 0.1% by mass with respect to the entire non-aqueous electrolyte (100% by mass). % Or more, preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 4% by mass or less, and particularly preferably 3% by mass or less. If it is in this range, the effect of the nonaqueous secondary battery of the present invention 2 can be fully enjoyed. Specifically, it is easy to avoid a situation where the high-temperature storage characteristics of the battery are reduced, the amount of gas generated is increased, and the discharge capacity retention rate is reduced. Furthermore, if the content is within the above range, the non-aqueous secondary battery can also exhibit sufficient cycle characteristics.

<Isocyanate compound or condensate thereof>
The isocyanate compound is not particularly limited as long as it is a compound having an isocyanate group in the molecule. Compounds having at least two isocyanate groups are preferred.

Specific examples of the isocyanate compound include, for example, methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, tertiary butyl isocyanate, pentyl isocyanate hexyl isocyanate, cyclohexyl isocyanate, vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, propynyl isocyanate, Monoisocyanate compounds such as phenyl isocyanate and fluorophenyl isocyanate;
Monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, 1,3-diisocyanate Natopropane, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2-pentene, 1,5 -Diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6 Diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanato) Methyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1 ′ -Diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, bicyclo [2.2.1] heptane 2,5-diylbis (methylisocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (methylisocyanate), isophorone diisocyanate, carbonyl diisocyanate, 1,4-diisocyanatobutane-1,4- Diisocyanate compounds such as dione, 1,5-diisocyanatopentane-1,5-dione, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate;
In addition, biurets, isocyanurates, adducts, and bifunctional type modified polyisocyanate compounds represented by the basic structures of the following formulas (1) to (4) are mentioned (in the formula, R ¹ and R ² are arbitrary, respectively) Hydrocarbon group).

Etc.

Among these, monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane-4,4′-diisocyanate, bicyclo [2.2.1] heptane-2,5-diylbis (methylisocyanate), bicyclo [2.2.1] heptane- 2,6-diylbis (methylisocyanate), isophorone diisocyanate, 2,2,4-trimethylhexamethyle Diisocyanates, 2,4,4-trimethylhexamethylene diisocyanate and the like, and biurets, isocyanurates, adducts, and bifunctional types represented by the basic structures of the above formulas (1) to (4) A modified polyisocyanate compound is preferable from the viewpoint of improving storage characteristics,
Hexamethylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane-4,4′-diisocyanate, bicyclo [2.2.1] heptane-2,5-diylbis (methyl isocyanate), bicyclo [2. 2.1] Heptane-2,6-diylbis (methyl isocyanate), 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate are more preferable.

An isocyanate compound or a condensate thereof may be used alone or in combination of two or more in any combination and ratio. The content of the isocyanate compound or the condensate thereof in the nonaqueous electrolytic solution is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably based on the whole nonaqueous electrolytic solution (100% by mass). Is 0.1% by mass or more, more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

When the above range is satisfied, in addition to the effect of the non-aqueous secondary battery of the present invention 2, the output characteristics, load characteristics, low temperature characteristics, cycle characteristics, etc. of the battery are improved.

<Fluorinated oxo acid salt>
In addition to the effect of the non-aqueous secondary battery of the present invention 2, a fluorinated oxoacid salt is used in the non-aqueous electrolyte in order to form a film on the negative electrode surface of the battery and achieve a long battery life. It is effective.

Examples of fluorinated oxoacid salts include fluorine-substituted phosphates, fluorine-substituted carboxylates, fluorine-substituted sulfonates, and fluorine-substituted sulfates.

The counter cation of the fluorinated oxoacid salt is not particularly limited, but lithium, sodium, potassium, magnesium, calcium, and NR ³ R ⁴ R ⁵ R ⁶ (wherein R ³ to R ⁶ are each independently As an example, ammonium represented by a hydrogen atom or an organic group having 1 to 12 carbon atoms can be given.

The organic group having 1 to 12 carbon atoms represented by R ³ to R ⁶ of ammonium is not particularly limited. For example, the organic group may be substituted with a halogen atom, a halogen atom or an alkyl group. Examples thereof include an cycloalkyl group which may be substituted, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent. In particular, R ³ to R ⁶ are each independently preferably a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.

In addition, lithium is most preferable among the above counter cations from the viewpoint of lithium electrodeposition resistance and oxidation resistance of the non-aqueous electrolyte.

Examples of the fluorine-substituted phosphates include monofluorophosphate and difluorophosphate. Specific examples thereof include lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate and the like. Among these, lithium monofluorophosphate and lithium difluorophosphate are preferable, and lithium difluorophosphate is more preferable.

Examples of the fluorine-substituted carboxylates include fluoroformate, monofluoroacetate, difluoroacetate and trifluoroacetate. Specific examples thereof include lithium fluoroformate, lithium monofluoroacetate, lithium difluoroacetate, and lithium trifluoroacetate.

Examples of the fluorine-substituted sulfonates include fluorosulfonate, trifluoromethanesulfonate, and pentafluoroethanesulfonate. Specific examples thereof include lithium fluorosulfonate, lithium trifluoromethanesulfonate, and lithium pentafluoroethanesulfonate.

Examples of the fluorine-substituted sulfates include trifluoromethyl sulfate and pentafluoroethyl sulfate. Specific examples thereof include lithium trifluoromethyl sulfate and lithium pentafluoroethyl sulfate.

Among these, preferred fluorinated oxoacid salts are lithium fluorosulfonate, lithium trifluoromethanesulfonate, lithium monofluorophosphate, and lithium difluorophosphate. This is because a stable interface protective film is formed.

The fluorinated oxoacid salts may be used alone or in combination of two or more in any combination and ratio. The blending amount of the fluorinated oxoacid salt is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and further preferably 0.1% by mass or more in 100% by mass of the non-aqueous electrolyte. Moreover, it is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less. Within this range, in addition to the effect of the nonaqueous secondary battery of the second aspect, the battery is likely to exhibit a sufficient cycle characteristic improving effect. In addition, it is easy to avoid a situation in which the high-temperature storage characteristics are reduced, the amount of gas generated is increased, and the discharge capacity maintenance rate is reduced.

<Nitrile compound>
The nitrile compound is not particularly limited as long as it is a compound having a nitrile group in the molecule. Compounds having at least two nitrile groups are preferred.

Specific examples of nitrile compounds include, for example,
Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile Crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitryl, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, 2-hexenenitrile, Fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-diph Oropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3 ' Compounds having one nitrile group such as thiodipropionitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, pentafluoropropionitrile;

Malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, dodecandinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, 2,3,3-trimethylsuccinonitrile, 2,2,3,3-tetramethylsuccinonitrile, 2,3-diethyl- 2,3-dimethylsuccinonitrile, 2,2-diethyl-3,3-dimethylsuccinonitrile, bicyclohexyl-1,1-dicarbonitrile, bicyclohexyl-2,2-dicarbonitrile, bicyclohexyl- , 3-dicarbonitrile, 2,5-dimethyl-2,5-hexanedicarbonitrile, 2,3-diisobutyl-2,3-dimethylsuccinonitrile, 2,2-diisobutyl-3,3-dimethylsuccino Nitrile, 2-methylglutaronitrile, 2,3-dimethylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,3,3-tetramethylglutaronitrile, 2,2,4,4-tetra Methylglutaronitrile, 2,2,3,4-tetramethylglutaronitrile, 2,3,3,4-tetramethylglutaronitrile, maleonitrile, fumaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-didianobenzene, 1,3-disi Nobenzene, 1,4-dicyanobenzene, 3,3 ′-(ethylenedioxy) dipropionitrile, 3,3 ′-(ethylenedithio) dipropionitrile, 3,9-bis (2-cyanoethyl) -2,4 , 8,10-tetraoxaspiro [5,5] undecane and other compounds having two nitrile groups;
Compounds having three nitrile groups such as cyclohexanetricarbonitrile, triscyanoethylamine, triscyanoethoxypropane, tricyanoethylene, pentanetricarbonitrile, propanetricarbonitrile, heptanetricarbonitrile;
Etc.

Of these, lauronitrile, crotononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, dodecandinitrile, fumaronitrile, 3,9-bis (2-cyanoethyl)- 2,4,8,10-Tetraoxaspiro [5,5] undecane is preferred from the viewpoint of improving storage characteristics.

In addition, succinonitrile, glutaronitrile, adiponitrile, pimonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, dodecandinitrile, fumaronitrile, 3,9-bis (2-cyanoethyl) -2,4,8,10-tetra A compound having two nitrile groups such as oxaspiro [5,5] undecane is more preferable,
More preferred are succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, suberonitrile, azeronitrile, and sebaconitrile.

A nitrile compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. The content of the nitrile compound in the nonaqueous electrolytic solution is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass relative to the whole nonaqueous electrolytic solution (100% by mass). It is at least mass%, more preferably at least 0.3 mass%, and usually at most 10 mass%, preferably at most 5 mass%, more preferably at most 3 mass%. When the above range is satisfied, the output characteristics, load characteristics, low temperature characteristics, cycle characteristics and the like of the battery are improved in addition to the effects of the nonaqueous secondary battery of the second aspect.

<Aromatic compounds>
The aromatic compound is not particularly limited as long as it is a compound having an aromatic group. Specific examples thereof include aromatic hydrocarbons such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran;
Methyl phenyl carbonate, ethyl phenyl carbonate, n-propyl phenyl carbonate, i-propyl phenyl carbonate, n-butyl phenyl carbonate, i-butyl phenyl carbonate, sec-butyl phenyl carbonate, t-butyl phenyl carbonate, n-pentyl phenyl carbonate, Examples thereof include aromatic carbonates such as t-amylphenyl carbonate, (1,1-dimethylbutyl) phenyl carbonate, and diphenyl carbonate.

Among these, preferred aromatic compounds are t-butylbenzene, t-amylbenzene, methylphenyl carbonate, ethylphenyl carbonate, n-propylphenyl carbonate, n-butylphenyl carbonate, and diphenyl carbonate. This is because when these are used, side reactions at the positive electrode are suppressed because there is no active benzyl hydrogen.

An aromatic compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. The content of the aromatic compound in the non-aqueous electrolyte is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.001% by mass or more with respect to the whole non-aqueous electrolyte (100% by mass). 1% by mass or more, still more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

<Phosphonate compounds>
The phosphonate compound is not particularly limited, and specifically, trimethylphosphonoformate,
Methyl diethylphosphonoformate,
Methyldipropylphosphonoformate,
Methyldibutylphosphonoformate,
Triethylphosphonoformate,
Ethyldimethylphosphonoformate,
Ethyldipropylphosphonoformate,
Ethyldibutylphosphonoformate,
Tripropylphosphonoformate,
Propyldimethylphosphonoformate,
Propyl diethylphosphonoformate,
Propyldibutylphosphonoformate,
Tributylphosphonoformate,
Butyldimethylphosphonoformate,
Butyl diethylphosphonoformate,
Butyl dipropyl phosphonoformate,
Methylbis (2,2,2-trifluoroethyl) phosphonoformate,
Ethylbis (2,2,2-trifluoroethyl) phosphonoformate,
Propylbis (2,2,2-trifluoroethyl) phosphonoformate,
Trimethylphosphonoacetate such as butylbis (2,2,2-trifluoroethyl) phosphonoformate,
Methyl diethylphosphonoacetate,
Methyldipropylphosphonoacetate,
Methyldibutylphosphonoacetate,
Triethylphosphonoacetate,
Ethyldimethylphosphonoacetate,
Ethyldipropylphosphonoacetate,
Ethyl dibutylphosphonoacetate,
Tripropylphosphonoacetate,
Propyldimethylphosphonoacetate,
Propyl diethylphosphonoacetate,
Propyl dibutyl phosphonoacetate,
Tributylphosphonoacetate,
Butyldimethylphosphonoacetate,
Butyl diethylphosphonoacetate,
Butyl dipropyl phosphonoacetate,
Methylbis (2,2,2-trifluoroethyl) phosphonoacetate,
Ethyl bis (2,2,2-trifluoroethyl) phosphonoacetate,
Propylbis (2,2,2-trifluoroethyl) phosphonoacetate,
Butyl bis (2,2,2-trifluoroethyl) phosphonoacetate trimethyl-3-phosphonopropionate,
Methyldiethyl-3-phosphonopropionate,
Methyldipropyl-3-phosphonopropionate,
Methyldibutyl-3-phosphonopropionate,
Triethyl-3-phosphonopropionate,
Ethyldimethyl-3-phosphonopropionate,
Ethyldipropyl-3-phosphonopropionate,
Ethyldibutyl-3-phosphonopropionate,
Tripropyl-3-phosphonopropionate,
Propyldimethyl-3-phosphonopropionate,
Propyl diethyl-3-phosphonopropionate,
Propyldibutyl-3-phosphonopropionate,
Tributyl-3-phosphonopropionate,
Butyldimethyl-3-phosphonopropionate,
Butyl diethyl-3-phosphonopropionate,
Butyldipropyl-3-phosphonopropionate,
Methyl bis (2,2,2-trifluoroethyl) -3-phosphonopropionate,
Ethyl bis (2,2,2-trifluoroethyl) -3-phosphonopropionate,
Propyl bis (2,2,2-trifluoroethyl) -3-phosphonopropionate,
Butyl bis (2,2,2-trifluoroethyl) -3-phosphonopropionate,
Trimethyl-4-phosphonobutyrate,
Methyldiethyl-4-phosphonobutyrate,
Methyldipropyl-4-phosphonobutyrate,
Methyldibutyl-4-phosphonobutyrate,
Triethyl-4-phosphonobutyrate,
Ethyldimethyl-4-phosphonobutyrate,
Ethyldipropyl-4-phosphonobutyrate,
Ethyldibutyl-4-phosphonobutyrate,
Tripropyl-4-phosphonobutyrate,
Propyldimethyl-4-phosphonobutyrate,
Propyldiethyl-4-phosphonobutyrate,
Propyldibutyl-4-phosphonobutyrate,
Tributyl-4-phosphonobutyrate,
Butyldimethyl-4-phosphonobutyrate,
Butyldiethyl-4-phosphonobutyrate,
Butyldipropyl-4-phosphonobutyrate,
2-propynyl 2- (dimethoxyphosphoryl) acetate, 2-propynyl-2- (diethoxyphosphoryl) acetate, 2-propynyl-2- (diphenoxyphosphoryl) acetate, 2-propynyl-2- (diethoxyphosphoryl) -2 -Fluoroacetate, 2-propynyl-3- (diethoxyphosphoryl) propanoate, 1-methyl-2-propynyl-2- (diethoxyphosphoryl) acetate, 1,1-dimethyl-2-propynyl-2- (diethoxyphosphoryl) ) Acetate, 2-trifluoromethylphenyl-2- (diethoxyphosphoryl) acetate, 4-trifluoromethylphenyl-2- (diethoxyphosphoryl) acetate, methyl-2- (2-oxide-1,3,2- Dioxaphosphoran-2-yl) acetate, -(2- (diethoxyphosphoryl) acetoxy) ethyl methyl oxalate, 2-butyne-1,4-diylbis (2- (diethoxyphosphoryl) acetate), and 2-cyanoethyl-2- (diethoxyphosphoryl) acetate Is mentioned.

Among these, preferred phosphonate compounds are trimethylphosphonoacetate,
Methyl diethylphosphonoacetate,
Methyldipropylphosphonoacetate,
Methyldibutylphosphonoacetate,
Triethylphosphonoacetate,
Ethyldimethylphosphonoacetate,
Ethyldipropylphosphonoacetate,
Ethyl dibutylphosphonoacetate,
Tripropylphosphonoacetate,
Propyldimethylphosphonoacetate,
Propyl diethylphosphonoacetate,
Propyl dibutyl phosphonoacetate,
Tributylphosphonoacetate,
Butyldimethylphosphonoacetate,
Butyl diethylphosphonoacetate,
Butyl dipropyl phosphonoacetate,
Methylbis (2,2,2-trifluoroethyl) phosphonoacetate,
Ethyl bis (2,2,2-trifluoroethyl) phosphonoacetate,
Propylbis (2,2,2-trifluoroethyl) phosphonoacetate,
Butylbis (2,2,2-trifluoroethyl) phosphonoacetate, 2-propynyl-2- (dimethoxyphosphoryl) acetate, 2-propynyl-2- (diethoxyphosphoryl) acetate, 2-propynyl-2- (diphenoxy) Phosphoryl) acetate, 2-propynyl-2- (diethoxyphosphoryl) -2-fluoroacetate, 2-propynyl-3- (diethoxyphosphoryl) propanoate, 1-methyl-2-propynyl-2- (diethoxyphosphoryl) acetate 1,1-dimethyl-2-propynyl-2- (diethoxyphosphoryl) acetate, 2-trifluoromethylphenyl-2- (diethoxyphosphoryl) acetate, 4-trifluoromethylphenyl-2- (diethoxyphosphoryl) Acetate, methyl-2- (2 Oxide-1,3,2-dioxaphosphoran-2-yl) acetate, 2- (2- (diethoxyphosphoryl) acetoxy) ethyl methyl oxalate, 2-butyne-1,4-diylbis (2- ( Diethoxyphosphoryl) acetate), and 2-cyanoethyl-2- (diethoxyphosphoryl) acetate. This is because these have a structure that facilitates chelate coordination, and thus have a strong protective effect on the positive electrode.

A phosphonic acid ester compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. The content of the phosphonic acid ester compound in the nonaqueous electrolytic solution is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0, relative to the entire nonaqueous electrolytic solution (100% by mass). 0.1% by mass or more, still more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

<Halogen-containing cyclic carbonate>
Examples of the halogen-containing cyclic carbonate include cyclic carbonates having fluorine atoms (hereinafter sometimes referred to as “fluorinated cyclic carbonates”). The fluorinated cyclic carbonate is not particularly limited as long as it is a cyclic carbonate having a fluorine atom.

Examples of the fluorinated cyclic carbonate include fluorinated cyclic carbonates having a C 2-6 alkylene group, and derivatives thereof. Specific examples include fluorinated ethylene carbonate and derivatives thereof. Examples of the derivatives of fluorinated ethylene carbonate include fluorinated ethylene carbonate substituted with an alkyl group (eg, an alkyl group having 1 to 4 carbon atoms). Of these, ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferred.

Specifically, as the fluorinated cyclic carbonate,
Monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4-fluoro-5-methyl Ethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4- (fluoro Methyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene Boneto, 4,4-difluoro-5,5-dimethylethylene carbonate.

Among these, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate and 4,5-difluoroethylene carbonate, in addition to the effect of the nonaqueous secondary battery of the present invention 2, This is more preferable because it imparts high ion conductivity to the non-aqueous electrolyte and suitably forms an interface protective film.

The halogen-containing cyclic carbonates described above may be used alone or in combination of two or more in any combination and ratio.

The content of the halogen-containing cyclic carbonate is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and further preferably 0.1% by mass with respect to the entire non-aqueous electrolyte (100% by mass). Above, still more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, most preferably 2% by mass or more, preferably 10% by mass or less, more preferably 7% by mass or less, More preferably, it is 5 mass% or less.

If it is within the above range, it is easy to avoid a situation in which the high-temperature storage characteristics of the non-aqueous secondary battery of the second aspect of the invention are lowered or the discharge capacity retention rate is lowered due to an increase in the amount of gas generated. Furthermore, in the non-aqueous secondary battery, cycle characteristics are improved.

<Oxalate salt>
There is no restriction | limiting in particular in the said oxalate salt, Arbitrary oxalate salts can be used. Examples of the oxalate salt include bis (oxalate) boric acid, difluoro (oxalate) borate, tris (oxalate) phosphate, difluoro (bisoxalate) phosphate, tetrafluoro (oxalate) phosphate, and the like. .

The counter cation of the oxalate salt is not particularly limited, and examples thereof include lithium, sodium, and potassium. Among the counter cations, lithium is most preferable from the viewpoint of the lithium electrodeposition resistance and oxidation resistance of the non-aqueous electrolyte.

In particular,
Lithium bis (oxalate) borate,
Lithium difluoro (oxalate) borate,
Tris (oxalate) lithium phosphate,
Difluoro (bisoxalate) lithium phosphate,
Tetrafluoro (oxalate) lithium phosphate,
Potassium bis (oxalate) borate,
Potassium difluoro (oxalate) borate,
Tris (oxalate) potassium phosphate,
Difluoro (bisoxalate) potassium phosphate,
Tetrafluoro (oxalate) potassium phosphate,
Sodium bis (oxalate) borate,
Sodium difluoro (oxalate) borate,
Tris (oxalate) sodium phosphate,
Difluoro (bisoxalate) sodium phosphate,
An example is sodium tetrafluoro (oxalate) phosphate.

Among them, preferred oxalate salts include
Lithium bis (oxalate) borate,
Lithium difluoro (oxalate) borate,
Tris (oxalate) lithium phosphate,
Difluoro (bisoxalate) lithium phosphate,
Tetrafluoro (oxalate) lithium phosphate is more preferably used from the viewpoint of lithium electrodeposition resistance.

The oxalate salt may be used alone or in combination of two or more in any combination and ratio. The content of the oxalate salt in the nonaqueous electrolytic solution is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass with respect to the entire nonaqueous electrolytic solution (100% by mass). % By mass or more, still more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

<Content of specific additive>
The specific additive described above has a preferable content in the non-aqueous electrolyte in each type. The content of the specific additive in the non-aqueous electrolyte is preferably 0.001% by mass or more and 10% by mass or less with respect to the entire non-aqueous electrolyte (100% by mass). Within this range, in addition to the effect of the nonaqueous secondary battery of the second aspect, the effect of each added specific additive can be enjoyed. Moreover, if it is this range, any specific additive will not be mix | blended excessively, and the disadvantageous effect by an excessive mix | blending will not express.

<Additives other than specific additives>
In the non-aqueous electrolyte used in the non-aqueous secondary battery of the present invention 2, other additives may be appropriately used in addition to the specific additive depending on the purpose. Examples of other additives include cyclic sulfonic acid esters shown below and other additives.

(Cyclic sulfonate ester)
The cyclic sulfonate ester is not particularly limited as long as it is a sulfonate ester having a cyclic structure.

Specific examples of the cyclic sulfonate ester include, for example, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, and 3-fluoro-1,3-propane. Sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone 1-propene-1,3-sultone, 2-propene-1, 3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro- 2-propene-1,3-sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propyl Pen-1,3-sultone, 2-methyl-1-propene-1,3-sultone, 3-methyl-1-propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3-methyl-2-propene-1,3-sultone, 1,4-butane sultone, 1-fluoro-1,4-butane sultone, 2-fluoro-1, 4-butane sultone, 3-fluoro-1,4-butane sultone, 4-fluoro-1,4-butane sultone, 1-methyl-1,4-butane sultone, 2-methyl-1,4-butane sultone, 3-methyl-1, 4-butane sultone, 4-methyl-1,4-butane sultone, 1-butene-1,4-sultone, 2-butene-1,4-sultone, 3-butene-1,4-sultone, 1-fluo -1-butene-1,4-sultone, 2-fluoro-1-butene-1,4-sultone, 3-fluoro-1-butene-1,4-sultone, 4-fluoro-1-butene-1,4 -Sultone, 1-fluoro-2-butene-1,4-sultone, 2-fluoro-2-butene-1,4-sultone, 3-fluoro-2-butene-1,4-sultone, 4-fluoro-2 -Butene-1,4-sultone, 1-fluoro-3-butene-1,4-sultone, 2-fluoro-3-butene-1,4-sultone, 3-fluoro-3-butene-1,4-sultone 4-fluoro-3-butene-1,4-sultone, 1-methyl-1-butene-1,4-sultone, 2-methyl-1-butene-1,4-sultone, 3-methyl-1-butene -1,4-sultone, 4-methyl-1-butene 1,4-sultone, 1-methyl-2-butene-1,4-sultone, 2-methyl-2-butene-1,4-sultone, 3-methyl-2-butene-1,4-sultone, 4- Methyl-2-butene-1,4-sultone, 1-methyl-3-butene-1,4-sultone, 2-methyl-3-butene-1,4-sultone, 3-methyl-3-butene-1, 4-sultone, 4-methyl-3-butene-1,4-sultone, 1,5-pentane sultone, 1-fluoro-1,5-pentane sultone, 2-fluoro-1,5-pentane sultone, 3-fluoro -1,5-pentane sultone, 4-fluoro-1,5-pentane sultone, 5-fluoro-1,5-pentane sultone, 1-methyl-1,5-pentane sultone, 2-methyl-1,5-pentane Sultone, 3-methyl 1,5-pentane sultone, 4-methyl-1,5-pentanthruton, 5-methyl-1,5-pentanthruton, 1-pentene-1,5-sultone, 2-pentene-1,5-sultone, 3 -Pentene-1,5-sultone, 4-pentene-1,5-sultone, 1-fluoro-1-pentene-1,5-sultone, 2-fluoro-1-pentene-1,5-sultone, 3-fluoro -1-pentene-1,5-sultone, 4-fluoro-1-pentene-1,5-sultone, 5-fluoro-1-pentene-1,5-sultone, 1-fluoro-2-pentene-1,5 -Sultone, 2-fluoro-2-pentene-1,5-sultone, 3-fluoro-2-pentene-1,5-sultone, 4-fluoro-2-pentene-1,5-sultone, 5-fluoro-2 -Bae Ten-1,5-sultone, 1-fluoro-3-pentene-1,5-sultone, 2-fluoro-3-pentene-1,5-sultone, 3-fluoro-3-pentene-1,5-sultone, 4-fluoro-3-pentene-1,5-sultone, 5-fluoro-3-pentene-1,5-sultone, 1-fluoro-4-pentene-1,5-sultone, 2-fluoro-4-pentene- 1,5-sultone, 3-fluoro-4-pentene-1,5-sultone, 4-fluoro-4-pentene-1,5-sultone, 5-fluoro-4-pentene-1,5-sultone, 1- Methyl-1-pentene-1,5-sultone, 2-methyl-1-pentene-1,5-sultone, 3-methyl-1-pentene-1,5-sultone, 4-methyl-1-pentene-1, 5-sultone, 5-me Til-1-pentene-1,5-sultone, 1-methyl-2-pentene-1,5-sultone, 2-methyl-2-pentene-1,5-sultone, 3-methyl-2-pentene-1, 5-sultone, 4-methyl-2-pentene-1,5-sultone, 5-methyl-2-pentene-1,5-sultone, 1-methyl-3-pentene-1,5-sultone, 2-methyl- 3-pentene-1,5-sultone, 3-methyl-3-pentene-1,5-sultone, 4-methyl-3-pentene-1,5-sultone, 5-methyl-3-pentene-1,5- Sultone, 1-methyl-4-pentene-1,5-sultone, 2-methyl-4-pentene-1,5-sultone, 3-methyl-4-pentene-1,5-sultone, 4-methyl-4- Pentene-1,5-sultone, 5-methyl- - pentene-1,5-sultone, methylene sulfate, ethylene sulfate, propylene sulfate, and the like.

Of these, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1, 3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1,4- Butane sultone, methylene methane disulfonate, and ethylene methane disulfonate are preferable from the viewpoint of improving the storage characteristics of the nonaqueous secondary battery of the present invention 2, and 1,3-propane sultone and 1-propene-1,3-sultone are more preferable. .

As the cyclic sulfonic acid ester, one kind may be used alone, and two kinds or more may be used in optional combination and ratio. The content of the cyclic sulfonic acid ester in the nonaqueous electrolytic solution is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0, relative to the entire nonaqueous electrolytic solution (100% by mass). 0.1% by mass or more, more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. When the above range is satisfied, the output characteristics, load characteristics, low temperature characteristics, cycle characteristics and the like of the battery are improved in addition to the effects of the nonaqueous secondary battery of the second aspect.

(Other additives)
Other known additives can be added to the non-aqueous electrolyte. Other additives include
Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate;
Succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, phenylsuccinic anhydride, And carboxylic anhydrides such as 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride;

Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane;
Ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, vinyl Methyl sulfonate, ethyl vinyl sulfonate, allyl vinyl sulfonate, propargyl vinyl sulfonate, methyl allyl sulfonate, ethyl allyl sulfonate, allyl sulfonate, propargyl allyl sulfonate, 1,2-bis (vinylsulfonoxy) Sulfur-containing compounds such as ethane;

Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide;
Trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, diethylphospho Phosphorus-containing compounds such as ethyl vinegar, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide;
Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane;
Fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride;
Etc.

These may be used alone or in combination of two or more. By adding these additives, capacity maintenance characteristics and cycle characteristics after high-temperature storage of the nonaqueous secondary battery of the second aspect of the invention can be improved.

The content of other additives in the nonaqueous electrolytic solution is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The content is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.2% by mass or more with respect to the entire non-aqueous electrolyte (100% by mass). In addition, it is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 1% by mass or less. If it is this range, the effect of other additives will be fully exhibited easily, and it will be easy to avoid the situation where battery characteristics, such as a high load discharge characteristic, fall.

The non-aqueous electrolyte used in the non-aqueous secondary battery of the second aspect described above includes those present inside the non-aqueous secondary battery.

Specifically, the following cases are mentioned.
Non-aqueous secondary battery prepared by separately synthesizing components of non-aqueous electrolyte such as electrolyte and organic solvent, preparing non-aqueous electrolyte from substantially isolated one, and separately assembling by the method described below When it is a non-aqueous electrolyte solution in a non-aqueous secondary battery obtained by pouring the solution into the inside.
When the components of the non-aqueous electrolyte are individually put in the non-aqueous secondary battery and mixed in the battery to obtain the same composition as the non-aqueous electrolyte.
When the compound constituting the non-aqueous electrolyte is generated in the non-aqueous secondary battery to obtain the same composition as the non-aqueous electrolyte.

In addition, the non-aqueous electrolyte used in the non-aqueous secondary battery of the present invention 2 contains an essential component (specific additive) such as a cyclic carbonate having a carbon-carbon unsaturated bond as described above, and a cyclic sulfonic acid Esters and other additives may optionally be included. The electrolytic solution preferably contains Zr or a Zr compound from the viewpoint of suppressing gas generation in the battery and reducing resistance. Examples of the Zr compound include (Zr (OC ₂ H ₅ ) ₄ , Zr (OC ₃ H ₇ ) ₄ , Zr (OCH (CH ₃ ) ₂ ) ₄ , Zr (OC ₄ H ₁₀ ) ₄ , ZrCl _{4 and the} like. These oxides are mentioned.

Note that Zr in the non-aqueous electrolyte may be added to the non-aqueous electrolyte from the outside. Further, the non-aqueous electrolyte initially does not contain Zr, but the non-aqueous secondary battery was manufactured and charged and discharged, and as a result of the Zr contained in the electrode being melted, the non-aqueous electrolyte that contained Zr was obtained. It may be an electrolytic solution.

Such a non-aqueous electrolyte containing Zr or a compound of Zr is also one of the inventions disclosed in the present specification, and by using this, an increase in positive electrode resistance after cycle charge / discharge and battery capacity can be improved. It is possible to manufacture a non-aqueous secondary battery in which the decrease is suppressed and the storage characteristics are excellent in a high temperature and high voltage environment. The nonaqueous secondary battery has a conventionally known configuration except that the nonaqueous secondary battery includes a nonaqueous electrolytic solution containing Zr or a compound of Zr. That is, the non-aqueous secondary battery includes a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte.

[Nonaqueous Secondary Battery of Invention 1 and Nonaqueous Secondary Battery of Invention 2]
As the nonaqueous secondary battery of the present invention 1 obtained using the positive electrode active material for the nonaqueous secondary battery of the present invention 1, a lithium secondary battery is particularly suitable. Moreover, the non-aqueous secondary battery of this invention 2 can also be utilized suitably as a lithium secondary battery. Hereinafter, the battery configuration of these non-aqueous secondary batteries (hereinafter collectively referred to as “non-aqueous secondary battery of the present invention”) will be described.

(Battery configuration)
The non-aqueous secondary battery of the present invention can adopt a known structure. Typically, the negative electrode capable of occluding and releasing ions (for example, lithium ions), and the non-aqueous secondary battery of the present inventions 1 and 2 are used. A positive electrode containing a predetermined positive electrode active material in a battery and a non-aqueous electrolyte are provided.

<Negative electrode for non-aqueous secondary battery>
The negative electrode can be produced by any known method as long as the effects of the present invention are not significantly impaired. For example, a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. are added to a negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed to collect current. A negative electrode having a negative electrode active material layer on the body can be formed. As the binder (binder), the thickener, and the conductive material, the same materials as those used for forming the positive electrode can be used.

Further, when an alloy material is used as the negative electrode active material, a method of forming a thin film layer (negative electrode active material layer) containing the negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.

(Negative electrode active material)
The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples thereof include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.

Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. It is done.

Further, the carbonaceous materials (1) to (6) may be used alone or in combination of two or more in any combination and ratio. When the natural graphite of (1) and other carbonaceous materials are used in combination, it is preferable that the ratio of natural graphite to the total carbonaceous material is 50% by mass or more.

The alloy material used as the negative electrode active material is lithium simple substance, single metal and alloy forming lithium alloy, or oxides, carbides, nitrides, silicides, sulfides thereof as long as lithium can be occluded / released. Or any of compounds, such as a phosphide, may be sufficient. The single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements (that is, excluding carbon), more preferably single metals of aluminum, silicon and tin and their atoms. An alloy or compound containing These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium. From the viewpoint of high current density charge / discharge characteristics, a material containing titanium and lithium is preferable, a lithium-containing composite metal composite oxide material containing titanium is more preferable, and a composite oxide of lithium and titanium is more preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure as the negative electrode active material because the output resistance of the nonaqueous secondary battery of the present invention is greatly reduced.

(Current collector)
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include those formed of a metal material such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. As the material, copper is particularly preferable from the viewpoint of ease of processing and cost.

<Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among these, a separator made of a material that is stable with respect to the non-aqueous electrolyte, that is, a resin, glass fiber, an inorganic substance, or the like is preferable. Moreover, it is preferable to use the separator of the porous sheet or nonwoven fabric form excellent in the liquid retention property.

<Battery design>
(Electrode group)
The electrode group may have either a laminated structure in which the positive electrode and the negative electrode are interposed via the separator, or a structure in which the positive electrode and the negative electrode are wound in a spiral shape via the separator. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

When the electrode group occupancy falls below the above range, the battery capacity decreases. Further, if the above range is exceeded, the void space is small, and the battery becomes hot and the member expands or the vapor pressure of the liquid component of the electrolyte increases. As a result, the internal pressure of the battery rises, and various characteristics such as charge / discharge repetition performance and high-temperature storage as the battery deteriorate. Furthermore, a gas release valve that releases the internal pressure to the outside may operate.

(Exterior case)
The material of the outer case is not particularly limited as long as it is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

As an exterior case using metals, laser welding, resistance welding, ultrasonic welding, metals are welded together to form a sealed and sealed structure, and the above-mentioned metals are used for caulking structure via a resin gasket The thing which was done is mentioned. Examples of the exterior case using the laminate film include a case in which a resin-sealed structure is formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used. Moreover, the shape of the exterior body is also arbitrary. Examples of the shape include a cylindrical shape, a square shape, a laminate shape, a coin shape, and a large size.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

[Examples and Comparative Examples for Invention 1]
First, the Example and comparative example regarding the positive electrode active material for non-aqueous secondary batteries of this invention 1, the positive electrode for non-aqueous secondary batteries, and a non-aqueous secondary battery are shown.

Example 1-1
<Preparation of positive electrode active material 1>
50 parts by mass of propanol was added to 100 parts by mass of the positive electrode active material core having an elemental composition of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ . 2 parts by mass of zirconium (IV) tetrapropoxide dissolved in 17 parts by mass of propanol was added and stirred. Thereafter, 0.7 parts by mass of water and 16 parts by mass of propanol were added dropwise to the resulting reaction mixture, and the mixture was further stirred for 1 hour while heating at 60 ° C. The powder obtained by removing the solvent was heated at 120 ° C. under reduced pressure for 5 hours. Thereafter, heat treatment was performed at a temperature of 400 ° C. for 3 hours in an air-fired furnace, whereby a positive electrode active material 1 was obtained.

<Preparation of positive electrode>
85 parts by mass of the positive electrode active material 1, 10 parts by mass of acetylene black as a conductive material, and 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed with a disperser in an N-methylpyrrolidone solvent. Slurried. This slurry was uniformly applied to a 15 μm thick aluminum foil, dried, and then pressed to produce a positive electrode.

<Production of negative electrode>
Graphite powder as the negative electrode active material, aqueous dispersion of sodium carboxymethylcellulose as the thickener (concentration of 1% by mass of sodium carboxymethylcellulose), aqueous dispersion of styrene butadiene rubber as the binder (concentration of styrene butadiene rubber of 50% by mass) Were prepared and mixed with a disperser to form a slurry. This slurry was uniformly applied to one side of a 10 μm thick copper foil, dried, and then pressed to prepare a negative electrode. In addition, each component was mix | blended in the case of slurry preparation so that it might become a mass ratio of natural graphite: Carboxymethylcellulose sodium: styrene butadiene rubber = 98: 1: 1 in the negative electrode after drying.

<Non-aqueous electrolyte>
As the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ as an electrolyte at a rate of 1 mol / L in a mixed solvent composed of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (mixing volume ratio 3: 4: 3) is used. It was.

<Production of secondary battery>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element. This battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were covered with a resin layer while projecting positive and negative terminals. Thereafter, a non-aqueous electrolyte was poured into the bag and vacuum sealed to produce a sheet-like non-aqueous secondary battery.

<Evaluation of initial resistance>
The nonaqueous secondary battery was charged to a voltage of 4.1 V over 12 hours at 25 ° C. in a state where the nonaqueous secondary battery was pressed between glass plates, and then a constant current discharge was performed to 3.0 V. Furthermore, after carrying out constant current charge to 4.2V over 3 hours or more, operation which carries out constant current discharge to 3.0V was performed twice. Then, after carrying out constant current charge to 4.5V over 3 hours or more, operation which carries out constant current discharge to 3.0V was performed twice. The capacity at the time of the second discharge at this time was defined as “reference capacity”.

Note that 1C represents a current value for discharging the reference capacity of the battery in one hour, and for example, 0.2C represents a current value of 1/5 thereof.

After the above operation, the impedance measurement was performed on the nonaqueous secondary battery charged to a voltage of 3.8 V under the conditions of a temperature of 25 ° C., a voltage amplitude of 10 mV, and a frequency range of 20000 to 0.02 Hz. From the obtained impedance measurement results, the measurement frequency and the imaginary part of the complex impedance were plotted. The maximum value in the region of 100 to 1 Hz was set as an “index of initial positive electrode resistance” of the nonaqueous secondary battery.

<Evaluation of resistance after cycle charge / discharge>
About the non-aqueous secondary battery which implemented initial resistance evaluation, cycle charging / discharging was performed and the subsequent resistance was evaluated. Specifically, it is as follows.

In an environment of a temperature of 60 ° C., the non-aqueous secondary battery was charged at a constant current to 4.5 V at a current value of 1 C, and further charged at a constant voltage until the current value reached 0.1 C. Then, constant current discharge was performed to 3.0V at 1C. The above charging / discharging process was made into 1 cycle, and 50 cycles of charging / discharging was implemented.

For the non-aqueous secondary battery after 50 cycles, impedance measurement was performed in the same manner as the initial resistance evaluation to obtain an index of positive electrode resistance. The value of the positive electrode resistance index after 50 cycles when the “initial positive electrode resistance index” obtained above was 100 was defined as “the relative resistance value of the positive electrode after cycle charge / discharge”.

<Evaluation of Zr-containing region>
From the positive electrode produced using the positive electrode active material 1, a section was prepared using a focused ion beam (FIB), and this section was observed with a transmission electron microscope (TEM). The element composition was analyzed by energy dispersive X-ray spectroscopy (EDS) at regular intervals from the observed particle surface portion of the positive electrode active material 1 toward the inside. At this time, in the vicinity of the surface of the positive electrode active material 1, the point where the constituent elements of the positive electrode active material core are detected for the first time is defined as the surface of the positive electrode active material 1, and the distance from that point is defined as the depth. The results are shown in FIG.

Note that the Zr-containing region was determined as a region containing all Ni, Co, Mn, and Zr in a molar ratio of 1.5% or more. The molar ratio of Zr to (Zr + Ni + Co + M) was measured as the average value of the Zr content ratio at each measurement point in the region.

From FIG. 1, the positive electrode active material 1 of Example 1-1 has Zr and the constituent metal elements (Ni, Co, Mn) of the positive electrode active material core at a depth of 0.8 to 8 nm from the surface of the positive electrode active material. It has a Zr containing region. In this region, the molar ratio of Zr to (Zr + Ni + Co + Mn) is 15%, but the molar ratio of Zr at a depth exceeding 8 nm deeper than the Zr-containing region and up to 80 nm is 0.1%.

[Example 1-2]
A positive electrode active material 2 was prepared by performing the same operation as in Example 1-1 except that the heat treatment at a temperature of 400 ° C. was not performed, and a battery was manufactured and evaluated by performing the same operation as in Example 1-1. did.

Example 1-3
38 parts by mass of propanol was added to 100 parts by mass of the positive electrode active material core having an element composition of LiNi _0.80 Co _0.15 Al _0.05 O ₂ . To this, 0.6 parts by mass of zirconium (IV) tetrapropoxide dissolved in 6 parts by mass of propanol was added and stirred. Thereafter, a mixture of 0.5 part by mass of water and 12 parts by mass of propanol was added dropwise to the reaction mixture, followed by further stirring for 1 hour while heating at 60 ° C. The powder obtained by distilling off the solvent was heated at 120 ° C. under reduced pressure for 8 hours to obtain a positive electrode active material 3.

Thereafter, Example 1-1 except that 85 parts by mass of the positive electrode active material 1 was changed to 95 parts by mass of the positive electrode active material 3, acetylene black was changed to 3 parts by mass, and PVdF was changed to 2 parts by mass. The same operation was performed to produce a positive electrode.

The production of the negative electrode, the non-aqueous electrolyte, and the non-aqueous secondary battery were carried out in the same manner as in Example 1-1.

<Evaluation of initial resistance>
A non-aqueous secondary battery produced using the positive electrode active material 3 is charged to a voltage of 4.2 V over 5 hours at 25 ° C. in a state where the non-aqueous secondary battery is sandwiched between glass plates and pressurized. The operation of discharging current was performed 4 times. The capacity at the time of the fourth discharge at this time was defined as “reference capacity”.

Thereafter, the non-aqueous secondary battery charged to 4.1 V was allowed to stand at 60 ° C. for 12 hours. After the above operation, the battery discharged to 3.0 V was recharged to 3.7 V, and impedance measurement was performed under the conditions of a temperature of −10 ° C., a voltage amplitude of 10 mV, and a frequency range of 20000 to 0.02 Hz. From the obtained impedance measurement results, the measurement frequency and the imaginary part of the complex impedance were plotted. The maximum value in the region of 100 to 1 Hz was taken as “an index of initial positive electrode resistance”.

<Evaluation of resistance and capacity after cycle charge / discharge>
About the non-aqueous secondary battery which implemented initial resistance evaluation, cycle charging / discharging was performed and subsequent resistance and capacity | capacitance were evaluated. Specifically, it is as follows.

In an environment at a temperature of 60 ° C., constant current charging was performed up to 4.2 V at a current value of 2 C, and further constant voltage charging was performed until the current value reached 0.1 C. Then, constant current discharge was performed to 3.0V at 2C. The above charging / discharging process was made into 1 cycle, and 100 cycles of charging / discharging was implemented.

In charge / discharge after the first time, 50 cycles, and 100 cycles, the discharge was performed at a current value of 0.2 C, and the capacity at the time of discharge after 100 cycles when the capacity at the time of the first discharge was assumed to be 100. It was defined as “capacity index after cycle charge / discharge”. In addition, the battery after 50 cycles was subjected to impedance measurement in the same manner as the measurement of the initial positive electrode resistance index to obtain the positive electrode resistance index. The value of the positive electrode resistance index after 50 cycles when the “initial positive electrode resistance index” was 100 was defined as “the relative resistance value of the positive electrode after cycle charge / discharge”.

[Comparative Example 1-1]
85 parts by mass of the positive electrode active material 4 having an elemental composition of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , 5 parts by mass of acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) 10 as a binder A part by mass was mixed with a disperser in an N-methylpyrrolidone solvent to form a slurry. This slurry was uniformly applied to a 15 μm thick aluminum foil, dried, and then pressed to produce a positive electrode. Using this positive electrode, a non-aqueous secondary battery was produced and evaluated in the same manner as in Example 1-1.

Note that the Zr-containing region of the positive electrode active material 4 was evaluated in the same manner as in Example 1-1. The results are shown in FIG. Since Zr was not detected, Zr is not plotted in FIG. From FIG. 2, it can be seen that the positive electrode active material 4 of Comparative Example 1-1 that has not been surface-treated does not have a Zr-containing region near the surface of the active material.

[Comparative Example 1-2]
To 100 parts by mass of the positive electrode active material having an elemental composition of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , 0.5 part by mass of ZrO ₂ nanoparticles (particle size less than 100 nm) is added, and the mechano to the mixture is added. Chemical treatment was performed. As a result, a positive electrode active material 5 having a ZrO ₂ coating layer on the surface but having no region containing both Zr and the constituent metal elements (Ni, Co, Mn) of the positive electrode active material core was produced.

A positive electrode was produced in the same manner as in Comparative Example 1-1 except that the positive electrode active material 5 was used as the positive electrode active material. Using this positive electrode, a non-aqueous secondary battery was produced and evaluated in the same manner as in Example 1-1.

[Comparative Example 1-3]
95 parts by mass of a positive electrode active material 6 having an elemental composition of LiNi _0.80 Co _0.15 Al _0.05 O ₂ , 3 parts by mass of acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) 2 as a binder A part by mass was mixed with a disperser in an N-methylpyrrolidone solvent to form a slurry. This slurry was uniformly applied to a 15 μm thick aluminum foil, dried, and then pressed to produce a positive electrode.

Using this positive electrode, a non-aqueous secondary battery was produced and evaluated in the same manner as in Example 1-3. However, an index of battery capacity after cycle charge / discharge is not obtained.

[Comparative Example 1-4]
A positive electrode active material 7 was produced in the same manner as in Example 1-3, except that zirconium (IV) tetrapropoxide was changed to aluminum (III) isopropoxide. Using this positive electrode active material 7, the same operation as in Example 1-3 was performed to produce and evaluate a nonaqueous secondary battery. However, the relative resistance value of the positive electrode after cycle charge / discharge is not obtained.

[Comparative Example 1-5]
A positive electrode active material 8 was produced in the same manner as in Example 1-1 except that the heat treatment temperature in the firing furnace was 800 ° C. Using this positive electrode active material 8, a non-aqueous secondary battery was fabricated and evaluated in the same manner as in Example 1-1.

The above evaluation results are shown in Table 1 and Table 2 below.

In the non-aqueous secondary battery produced using Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-3 using the positive electrode active material of the present invention 1, the relative resistance value after cycle charge / discharge is It can be seen that it is kept small.

Further, the following can be seen from Example 1-1 and Comparative Example 1-2. In the non-aqueous secondary battery (Example 1-1) manufactured using the positive electrode active material of the first invention, a Zr-containing region exists in the vicinity of the surface of the positive electrode active material. On the other hand, the positive electrode active material manufactured in Comparative Example 1-2 has a ZrO ₂ coating layer, but does not have a region containing both Zr and the constituent metal elements (Ni, Co, Mn) of the positive electrode active material core. When the non-aqueous secondary battery of Example 1-1 and the non-aqueous secondary battery of Comparative Example 1-2 are compared, the increase in resistance after cycle charge / discharge is greatly suppressed in the former. .

In Example 1-3 and Comparative Example 1-4, in the nonaqueous secondary battery (Example 1-3) manufactured using the positive electrode active material of the present invention 1, instead of the Zr-containing surface treatment material, Al The battery capacity after cycle charge / discharge is higher than that in the non-aqueous secondary battery (Comparative Example 1-4) manufactured using the positive electrode active material subjected to the same surface treatment using the surface treatment material containing It can be seen that the decrease is suppressed.

From Example 1-1 and Comparative Example 1-5, in the battery manufactured using the positive electrode active material of the present invention 1 (Example 1-1), the heat treatment temperature at the time of manufacture was high, and the vicinity of the surface of the active material was high. It can be seen that the relative resistance value after cycle charge / discharge is suppressed smaller than in the non-aqueous secondary battery (Comparative Example 1-5) manufactured using the positive electrode active material having an insufficient amount of Zr.

[Examples and Comparative Examples for Invention 2]
Next, the Example and comparative example regarding the non-aqueous secondary battery of this invention 2 are shown.

<Preparation of positive electrode active material for non-aqueous secondary battery>
38 parts by mass of propanol was added to 100 parts by mass of a lithium transition metal oxide having an elemental composition of LiNi _0.80 Co _0.15 Al _0.05 O ₂ . To this was added 0.6 parts by mass of zirconium (IV) tetrapropoxide dissolved in 6 parts by mass of propanol, and after that, a mixture of 0.5 parts by mass of water and 12 parts by mass of propanol was added dropwise. Furthermore, the obtained mixed liquid was stirred for 1 hour while heating at 60 ° C. The powder obtained by distilling off the solvent from the mixture was heated under reduced pressure at a temperature of 120 ° C. for 8 hours to obtain a positive electrode active material for a non-aqueous secondary battery of the present invention 2.

As a result of thermal desorption-GC / MS analysis of this positive electrode active material, 1-propanol and propanal were confirmed. 1-propanol and propanal could not be confirmed in the positive electrode active material that was not subjected to the Zr-containing layer formation treatment in Reference Example 2 described later.

The details of thermal desorption-GC / MS analysis are as follows. 10 mg of the sample was heat-treated at 300 ° C. for 5 minutes, and the generated gas was extracted under a He stream, and trapped on the column using liquefied nitrogen. The trapped collection was analyzed.

[Reference Example 1]
<Preparation of positive electrode>
95 parts by mass of the positive electrode active material for a non-aqueous secondary battery, 3 parts by mass of acetylene black as a conductive material, and 2 parts by mass of polyvinylidene fluoride (trade name L # 1120, manufactured by Kureha Chemical) as a binder. In a N-methylpyrrolidone solvent, the mixture was slurried by mixing with a disperser. This slurry was uniformly applied to a 15 μm thick aluminum foil, dried, and then pressed to produce a positive electrode.

Using the obtained positive electrode, a nonaqueous secondary battery was produced in the same manner as in Example 1-1, and was charged and discharged three times. Thereafter, the positive electrode is taken out from the battery, and the result of analyzing the positive electrode by X-ray photoelectron spectroscopy (XPS) is shown in FIG.

The XPS evaluation conditions are as follows. The positive electrode was sampled in a glove box in an Ar atmosphere. Using a transfer vessel, a positive electrode was introduced into a measuring apparatus (PCA, ESCA5700ci) without being exposed to the atmosphere. X-rays were Al Kα (1486.7 eV), acceleration voltage 14 kV, 350 W, using an electron neutralizing gun, and the take-off angle was set to 65 °. The measurement area was 800 μmφ of the electrode. The positive electrode was subjected to solvent washing before measurement, and then attached to a carbon tape as a sample for measurement.

[Reference Example 2]
95 parts by mass of a positive electrode active material having an elemental composition of LiNi _0.80 Co _0.15 Al _0.05 O ₂ , 3 parts by mass of acetylene black as a conductive material, and polyvinylidene fluoride (manufactured by Kureha Chemical, 2 parts by mass of a product name L # 1120) was mixed with a disperser in an N-methylpyrrolidone solvent to form a slurry. This slurry was uniformly applied to a 15 μm thick aluminum foil, dried, and then pressed to produce a positive electrode.

Using the obtained positive electrode, a nonaqueous secondary battery was produced in the same manner as in Example 1-1, and was charged and discharged three times. Thereafter, the positive electrode was taken out from the battery, and the positive electrode was analyzed by XPS. The results are shown in FIG.

<Production of negative electrode>
A negative electrode was produced in the same manner as in <Preparation of negative electrode> in Example 1-1.

<Non-aqueous electrolyte>
The same electrolytic solution as the <nonaqueous electrolytic solution> in Example 1-1 was used.

<Production of secondary battery>
Using the positive electrode, negative electrode, and polyethylene separator of Reference Example 1 or 2, a sheet-like non-aqueous secondary battery was prepared in the same manner as in <Preparation of secondary battery> in Example 1-1. did.

<Initial evaluation>
In a state where the nonaqueous secondary battery was sandwiched between glass plates and pressurized, the operation of charging to a voltage of 4.2 V over 25 hours at 25 ° C. and then discharging to a constant current of 2.5 V were performed twice. . Thereafter, the battery was charged at a constant current to 4.2 V over 5 hours and then immersed in an ethanol bath at room temperature to measure the battery volume (referred to as “initial volume (mL / cell)”).

Thereafter, impedance measurement of the positive electrode was performed under the conditions of a temperature of −10 ° C., a voltage amplitude of 10 mV, and a frequency region of 100,000 to 0.001 Hz. From the obtained impedance measurement results, the measurement frequency and the imaginary part of the complex impedance were plotted. The maximum value in the region of 10 to 0.005 Hz was used as an index of the initial positive electrode resistance (referred to as “initial resistance (Ω / cell)”).

<Storage test under high temperature and high voltage>
For the non-aqueous secondary battery that was initially evaluated, a battery that was discharged and charged under the same conditions as the initial evaluation and was charged up to 4.2 V twice (the capacity at this time is referred to as “charging capacity before storage”) And stored at 85 ° C. for 3 days.

The battery after storage was discharged to 2.5 V at 25 ° C. (“Remaining capacity: discharge capacity after storage”) and then constant-current charging to 4.2 V (“Recovery capacity: charge capacity after storage”) The obtained battery was immersed in an ethanol bath at room temperature and its volume was measured (referred to as “volume after storage (mL / cell)”).

Thereafter, impedance measurement of the positive electrode was performed under the conditions of a temperature of −10 ° C., a voltage amplitude of 10 mV, and a frequency region of 100,000 to 0.001 Hz. From the obtained impedance measurement results, the measurement frequency and the imaginary part of the complex impedance were plotted. The maximum value in the region of 10 to 0.005 Hz was used as an index of positive electrode resistance after storage (referred to as “resistance after storage (Ω / cell)”).

The battery performance index was determined as follows.
Residual rate (%) = remaining capacity / charge capacity before storage x 100
Recovery rate (%) = Recovery capacity / Charge capacity before storage × 100
Volume change after storage (mL / cell) = Volume after storage-Initial volume

The volume change rate (%) is the volume change (mL / cell) after storage of Reference Example 1 for Examples 2-1 to 2-4 below, and Reference Example 2 for Comparative Examples 2-1 to 2-4 below. The volume change after storage of (mL / cell) was calculated as a standard (100%).

Initial resistivity (%) = initial resistance of Example or Comparative Example / initial resistance of Reference Example 1 or 2 × 100
Resistivity after storage (%) = Resistance after storage in Examples or Comparative Examples / Resistance after storage in Reference Example 1 or 2 × 100
* Regarding the resistivity, the positive electrode resistance of the example is divided by the positive electrode resistance of Reference Example 1, and the positive electrode resistance of the comparative example is divided by the positive electrode resistance of Reference Example 2.

[Example 2-1]
In Reference Example 1, a non-aqueous secondary battery was produced and evaluated in the same manner as Reference Example 1 except that a non-aqueous electrolyte solution added with vinylene carbonate to a content of 0.5% by mass was used.

[Example 2-2]
In Reference Example 1, a nonaqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 1 except that a nonaqueous electrolytic solution in which hexamethylene diisocyanate was added to a content of 0.5 part by mass was used.

[Example 2-3]
In Reference Example 1, a nonaqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 1 except that a nonaqueous electrolytic solution in which lithium difluorophosphate was added to a content of 0.5% by mass was used. .

[Example 2-4]
A nonaqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 1 except that a nonaqueous electrolyte solution in which adiponitrile was added to a content of 0.5% by mass was used in Reference Example 1.

[Comparative Example 2-1]
In Reference Example 2, a nonaqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 2 except that a nonaqueous electrolytic solution in which vinylene carbonate was added to a content of 0.5% by mass was used.

[Comparative Example 2-2]
In Reference Example 2, a nonaqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 2 except that a nonaqueous electrolytic solution in which hexamethylene diisocyanate was added to a content of 0.5% by mass was used.

[Comparative Example 2-3]
In Reference Example 2, a nonaqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 2 except that a nonaqueous electrolyte solution added with lithium difluorophosphate so as to have a content of 0.5% by mass was used. .

[Comparative Example 2-4]
In Reference Example 2, a nonaqueous secondary battery was produced and evaluated in the same manner as Reference Example 2 except that a nonaqueous electrolyte solution added with adiponitrile to a content of 0.5% by mass was used.

The evaluation results of the batteries obtained in Reference Examples 1-2, Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-4 are shown in Tables 3 and 4 below.

As shown in Table 3, when Reference Example 1 (with Zr on the surface of the positive electrode active material) and Reference Example 2 (without Zr on the surface of the positive electrode active material) were compared, Reference Example 1 had a higher temperature and higher voltage environment than Reference Example 2. It can be seen that the resistance value after storage below is low. However, this still does not have sufficient battery performance.

Next, as in Example 2-1 to Example 2-4, in the positive electrode having a Zr-containing layer (Reference Example 1), a specific additive is further added to the non-aqueous electrolyte so that a high temperature and high voltage can be obtained. In a storage test under an environment, a non-aqueous secondary battery having low resistance and low volume change could be obtained. On the other hand, as in Comparative Examples 2-1 to 2-4, even with a positive electrode that does not have a Zr-containing layer, the volume after storage can be generally reduced by adding an additive to the electrolyte, It was found that the resistance after storage was high.

More specifically, Example 2-1 to Example 2-4 use a positive electrode having a Zr-containing layer and to which a predetermined specific additive is added. Comparative Examples 2-1 to 2 -4 is obtained by using a positive electrode having no Zr-containing layer and adding the same specific additive as in the example having the same number. When the same numbers are compared, the following can be understood.

When vinylene carbonate is added (Example 2-1 and Comparative Example 2-1), the volume change rate is increased in the comparative example, whereas the volume change rate is reduced in the example. . Although the initial resistivity and the resistivity after storage are decreased in the examples and comparative examples (except for the initial resistivity in comparative example 2-1), the degree of the decrease is larger in the examples.

About hexamethylene diisocyanate (Example 2-2 and Comparative Example 2-2), lithium difluorophosphate (Example 2-3 and Comparative Example 2-3) and adiponitrile (Example 2-4 and Comparative Example 2-4) However, when the positive electrode having the Zr-containing layer is used (Example), the volume change rate, the initial resistivity, and the resistivity after storage are reduced, or the degree of reduction is large.

The reason why such an effect is obtained is unknown, but it is presumed to be due to a synergistic effect between the Zr-containing layer formed on the surface of the positive electrode active material particles and the specific additive.

[Example 2-5]
In Reference Example 1, a non-aqueous electrolyte was used in the same manner as in Reference Example 1 except that a non-aqueous electrolyte solution containing 2-propynyl-2- (diethoxyphosphoryl) acetate added to a content of 0.5% by mass was used. A secondary battery was fabricated and evaluated.

[Example 2-6]
A non-aqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 1 except that a non-aqueous electrolyte solution added with t-amylbenzene in a content of 0.5% by mass was used in Reference Example 1. .

[Example 2-7]
In Reference Example 1, a non-aqueous secondary battery was prepared and evaluated in the same manner as in Reference Example 1 except that a non-aqueous electrolyte solution added with monofluoroethylene carbonate to a content of 0.5% by mass was used. .

[Example 2-8]
In Reference Example 1, a non-aqueous secondary battery was prepared in the same manner as in Reference Example 1 except that a non-aqueous electrolyte solution added with a difluoro (bisoxalate) lithium phosphate content of 0.5% by mass was used. Prepared and evaluated.

Table 5 below shows the evaluation results of the batteries obtained in Reference Example 1 and Examples 2-5 to 2-8.

As shown in Table 5, in any of Examples 2-5 to 2-8, a low resistance non-aqueous secondary battery could be obtained in a storage test under a high temperature and high voltage environment.

Claims

Positive electrode active material for non-aqueous secondary battery that satisfies the following conditions (1) to (3):
(1) A lithium compound having a structure capable of desorbing and inserting Li ions, wherein the positive electrode active material core includes Ni, Co, and M (M is Mn and / or Al).
(2) A Zr-containing region containing all of Zr, Ni, Co, and M exists at a depth of 0.1 to 100 nm from the active material surface.
(3) The molar ratio of Zr to (Zr + Ni + Co + M) in the Zr-containing region is 1.5 to 30%.
The element composition of the positive electrode active material core is expressed as Li x Ni 1-yz-α Co y Al z M ′ α O 2 , where M ′ is 1 other than Li, Ni, Co, and Al. The element according to claim 1, wherein the element is a seed or more element, and 0.9 ≦ x ≦ 1.1, 0 <y ≦ 0.4, 0 <z ≦ 0.5, and 0 ≦ α ≦ 0.01. Positive electrode active material for water secondary battery.
The positive electrode active material for a non-aqueous secondary battery according to claim 1 or 2, wherein the Zr-containing region is present at a depth of 0.2 to 70 nm from the surface of the active material.
A positive electrode current collector, and a positive electrode active material layer containing the positive electrode active material for a nonaqueous secondary battery according to any one of claims 1 to 3 formed on the positive electrode current collector, Positive electrode for water secondary battery.
A nonaqueous secondary battery comprising a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and a nonaqueous electrolyte, wherein the positive electrode is the positive electrode for a nonaqueous secondary battery according to claim 4. Next battery.
A non-aqueous secondary battery comprising at least a positive electrode having a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte,
Zr and at least one group selected from the group consisting of a hydroxyl group, an aldehyde group, an alkoxy group, and a carboxyl group exist on the particle surface of the positive electrode active material,
The non-aqueous electrolyte includes a cyclic carbonate having a carbon-carbon unsaturated bond, an isocyanate compound or a condensate thereof, a fluorinated oxo acid salt, a nitrile compound, an aromatic compound, a phosphonic acid ester compound, a halogen-containing cyclic carbonate, and an oxalate A non-aqueous secondary battery containing at least one compound selected from the group consisting of salts.
The positive electrode active material is a lithium transition metal oxide having a structure capable of desorbing and inserting Li ions, the elemental composition of which is expressed as Li s M ″ 1-t AtO 2 , M ″ is at least two elements selected from the group consisting of Li, Ni, Co and Mn, A is an element other than Li, Ni, Co and Mn, and 0.9 ≦ s ≦ 1.2. The nonaqueous secondary battery according to claim 6, wherein 0 ≦ t ≦ 0.1.
Selected from the group consisting of the above cyclic carbonate having a carbon-carbon unsaturated bond, isocyanate compound or condensate thereof, fluorinated oxo acid salt, nitrile compound, aromatic compound, phosphonic acid ester compound, halogen-containing cyclic carbonate, and oxalate salt. The non-aqueous secondary battery according to claim 6 or 7, wherein at least one kind of compound is contained in an amount of 0.001% by mass or more and 10% by mass or less based on the whole non-aqueous electrolyte.
The non-aqueous secondary according to any one of claims 6 to 8, wherein in the portion where Zr is present, the molar ratio of Zr to all transition metals present in the portion is 1.5 to 30%. battery.
Zr or a compound containing Zr;
Selected from the group consisting of cyclic carbonates having a carbon-carbon unsaturated bond, isocyanate compounds or condensates thereof, fluorinated oxo acid salts, nitrile compounds, aromatic compounds, phosphonic acid ester compounds, halogen-containing cyclic carbonates, and oxalate salts. A non-aqueous electrolyte containing at least one compound.
A nonaqueous secondary battery comprising a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and a nonaqueous electrolyte solution, wherein the nonaqueous electrolyte solution is the nonaqueous electrolyte solution according to claim 10. Next battery.
A cyclic carbonate having a carbon-carbon unsaturated bond, an isocyanate compound or a condensate thereof, a fluorinated oxoacid salt, for producing the nonaqueous secondary battery according to any one of claims 6 to 9 and 11. Use of a nonaqueous electrolytic solution containing at least one compound selected from the group consisting of a nitrile compound, an aromatic compound, a phosphonic acid ester compound, a halogen-containing cyclic carbonate, and an oxalate salt.