JP2017027772A - Lithium ion secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel method for setting a liquid quantity of an electrolytic solution of a lithium ion secondary battery, which enables the enhancement in life characteristic in a lithium ion secondary battery having a negative electrode including silicon.SOLUTION: A method for manufacturing a lithium ion secondary battery including a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer including silicon, a separator and a nonaqueous electrolyte solution comprises the step of setting a liquid quantity of the nonaqueous electrolyte solution so as to meet the following formula (1): 0.89≤Liquid quantity (ml) of the nonaqueous electrolyte solution÷(Quantity (ml) of pores in the positive electrode active material layer+Quantity (ml) of pores in the separator+Quantity (ml) of pores in the negative electrode active material layer)<1.13 Formula (1).SELECTED DRAWING: None

Description

  The present invention relates to a lithium ion secondary battery and a method for manufacturing the same.

  Products using non-aqueous electrolyte secondary batteries are steadily increasing, and in general, non-aqueous electrolyte secondary batteries are recognized as essential for portable devices such as mobile phones and laptop computers. Among non-aqueous electrolyte secondary batteries, lithium ion secondary batteries are widely used because of their small size and large capacity, and are also used in aircraft and automobiles.

In recent years, research on lithium ion secondary batteries has been actively conducted, and as a negative electrode active material for lithium ion secondary batteries, silicon, silicon alloys, silicon oxides, and the like having a charge / discharge capacity that greatly exceeds the theoretical capacity of carbon materials These silicon-based materials have been studied. For example, in Patent Document 1, CaSi ₂ and an acid are reacted to synthesize a layered silicon compound mainly composed of layered polysilane, and the layered silicon compound is heated at 300 ° C. or higher to produce a silicon material. And a lithium ion secondary battery including the silicon material as an active material. In addition, when a silicon-based material is used as a negative electrode active material, it is known that the silicon-based material expands and contracts with the insertion and extraction of lithium (Li) during charge and discharge.

  Now, the amount of the electrolytic solution used for the lithium ion secondary battery is generally set so that the lithium ion secondary battery operates well and does not lower the energy density of the battery. It is known that when the amount of the electrolyte is too small, the resistance of the lithium ion secondary battery increases, and when the resistance of the battery increases, the life of the lithium ion secondary battery is shortened. Moreover, since electrolyte solution may be decomposed | disassembled with charging / discharging, it was supposed that the amount of electrolyte solution was as much as possible.

  The amount of the electrolytic solution in the lithium ion secondary battery varies depending on the electrode and separator used. In particular, since silicon expands and contracts due to charging and discharging, in a lithium ion secondary battery using a negative electrode active material containing silicon, it is difficult to set the amount of the electrolytic solution. Accordingly, there has been a demand for a new method for setting the amount of the electrolytic solution that can improve the life characteristics of a lithium ion secondary battery having a negative electrode active material containing silicon.

International Publication No. 2014/080608

  The present invention has been made in view of such circumstances, and the amount of electrolyte in a lithium ion secondary battery that can improve the life characteristics of a lithium ion secondary battery having a negative electrode containing silicon. It aims to provide a new setting method.

  As a result of earnest research, the inventors of the present invention can improve the life of a lithium ion secondary battery having a negative electrode containing silicon if the amount of the electrolyte is set based on a new equation. I found it.

That is, the method for producing a lithium ion secondary battery of the present invention includes a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer containing silicon, a separator, and a nonaqueous electrolyte solution. And a liquid amount setting step of setting the liquid amount of the non-aqueous electrolyte so as to satisfy the following formula (1).
0.89 ≦ Non-aqueous electrolyte volume (ml) / (Positive electrode active material layer void volume (ml) + Separator void volume (ml) + Negative electrode active material layer void volume (ml)) <1.13 .... Formula (1)

A step of reacting CaSi ₂ with an acid to produce a layered silicon compound mainly composed of layered polysilane, a step of producing a silicon material by heating the layered silicon compound at 300 ° C. or higher, and a negative electrode containing the silicon material. A negative electrode manufacturing step to be manufactured.

  Furthermore, it is preferable to include a liquid amount calculation step of calculating the liquid amount of the non-aqueous electrolyte so as to satisfy the formula (1).

  The lithium ion secondary battery of the present invention includes a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer containing silicon, a separator, and a non-aqueous electrolyte. The expression (1) is satisfied.

  The negative electrode active material layer preferably contains a silicon material having a structure in which plate-like silicon bodies are laminated in the thickness direction.

  According to the method for producing a lithium ion secondary battery of the present invention having the liquid amount setting step of the non-aqueous electrolyte, the life of the lithium ion secondary battery having a negative electrode containing silicon can be improved.

  Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

<Method for producing lithium ion secondary battery>
A method for producing a lithium ion secondary battery according to the present invention includes a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer containing silicon, a separator, and a non-aqueous electrolyte. It is a manufacturing method, Comprising: The liquid quantity setting process which sets the liquid quantity of a non-aqueous electrolyte so that following formula (1) may be satisfy | filled is characterized.
0.89 ≦ Non-aqueous electrolyte volume (ml) / (Positive electrode active material layer void volume (ml) + Separator void volume (ml) + Negative electrode active material layer void volume (ml)) <1.13 .... Formula (1)

  The manufacturing method of the lithium ion secondary battery of this invention includes the liquid quantity setting process which sets the liquid quantity of a non-aqueous electrolyte so that Formula (1) may be satisfy | filled.

(Liquid volume setting process)
In the liquid volume setting step, the liquid volume of the non-aqueous electrolyte is set. At this time, the calculation method of the amount of the non-aqueous electrolyte is not particularly limited. For example, it may be confirmed whether the amount of the electrolyte calculated by a known calculation method satisfies the formula (1), and the amount of the liquid that satisfies the formula (1) may be set as the amount of the electrolyte.

  In addition to the liquid volume setting step, a liquid volume calculation step of calculating the liquid volume of the non-aqueous electrolyte so as to satisfy the formula (1) may be included. In the liquid amount calculation step, the liquid amount of the nonaqueous electrolytic solution is calculated so as to satisfy Expression (1).

  Here, (the amount of voids in the positive electrode active material layer (ml) + the amount of voids in the separator (ml) + the amount of voids in the negative electrode active material layer (ml)) was measured or calculated in the state where the amount of each void was added Alternatively, each void amount may be measured or calculated, and the numerical values may be added together.

  For example, each void amount can be calculated as follows.

  The amount of voids in the positive electrode active material layer is a value obtained by subtracting the theoretical volume of each component calculated from the blending amount and true density of each component contained in the positive electrode active material layer from the apparent volume of the positive electrode active material layer. It is.

When the components included in the positive electrode active material layer are, for example, a positive electrode active material, a conductive additive, and a binder, the void amount of the positive electrode active material layer is calculated by the following formula.
Void amount = (apparent volume of positive electrode active material layer−sum of theoretical volume of each component of positive electrode active material layer)
Apparent volume of positive electrode active material layer = actual thickness of positive electrode active material layer × area of surface on which positive electrode active material layer is formed Sum of theoretical volumes of components of positive electrode active material layer = mass of positive electrode active material ÷ positive electrode True density of active material + mass of conductive aid ÷ true density of conductive aid + mass of binder ÷ true density of binder

  The void amount of the negative electrode active material layer is a value obtained by subtracting the theoretical volume of each component calculated from the blending amount and true density of each component contained in the negative electrode active material layer from the apparent volume of the negative electrode active material layer. It is obtained in the same manner as the void amount of the positive electrode active material layer.

  The amount of voids in the separator is a value obtained by subtracting the sum of the theoretical volumes of each component calculated from the blending amount and true density of each component contained in the separator from the apparent volume of the separator.

  In the manufacturing method of the lithium ion secondary battery of the present invention, a known method may be used for manufacturing steps other than the liquid amount setting step and the liquid amount calculating step.

  In the method for producing a lithium ion secondary battery of the present invention, the lithium ion secondary battery includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolytic solution.

  A positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte will be described below.

(Positive electrode)
The positive electrode has a positive electrode active material layer containing a positive electrode active material. The positive electrode active material layer is disposed on the surface of the current collector.

  The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery. Examples of the current collector material include metal materials such as stainless steel, titanium, nickel, aluminum, and copper, or conductive resins. In particular, from the viewpoint of electrical conductivity, workability, and cost, the material for the current collector is preferably aluminum or copper. The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. As the current collector, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, or a stainless steel foil can be suitably used. When the current collector is a foil, sheet or film, the thickness of the current collector is preferably 10 μm to 50 μm. In view of increasing the battery capacity while maintaining high strength in the current collector, the thickness of the current collector is particularly preferably 12 μm to 30 μm.

(Positive electrode active material layer)
The positive electrode active material layer has a positive electrode active material. The positive electrode active material layer may include a binder and a conductive additive as necessary.

Examples of the positive electrode active material include lithium-containing compounds or other metal compounds. Examples of the lithium-containing compound, for example, lithium-cobalt composite oxide having a layered structure, the lithium nickel composite oxide having a layered structure, the lithium manganese composite oxide having a spinel structure represented by the general _{formula: Li a Co p Ni q Mn} r D _s O _x (D is at least one selected from Al, Mg, Ti, Sn, Zn, W, Zr, Mo, Fe and Na, p + q + r + s = 1, 0 <p <1, 0 ≦ q <1, 0 ≦ r <1, 0 ≦ s <1, 0.8 ≦ a <2.0, −0.2 ≦ x− (a + p + q + r + s) ≦ 0.2) things, the general formula: olivine-type lithium phosphate compound oxide represented by LiMPO ₄ (at least one of M is Mn, Fe, Co and Ni), the general _formula: represented by Li 2 MPO ₄ F That fluoride olivine-type lithium phosphate compound oxide (M is Mn, Fe, at least one of Co and Ni), the general _formula: Li 2 MSiO silicate lithium composite oxide represented by ₄ (M is _{one or more of} At least one of Mn, Fe, Co, and Ni). Examples of other metal compounds include oxides such as titanium oxide, vanadium oxide, and manganese dioxide, and sulfides such as titanium sulfide and molybdenum sulfide.

The positive electrode active material preferably has an average particle diameter _{D 50} is a powder shape is 1 m to 20 m. When the average particle diameter D ₅₀ of the positive electrode active material is small, the specific surface area of the positive electrode active material is increased. Thus, the reaction area of the average particle diameter D ₅₀ of the positive electrode active material is too small and the positive electrode active material and the electrolyte becomes excessive increase it, as a result, are accelerated decomposition of the electrolytic solution, the lithium ion secondary The cycle characteristics of the battery may be deteriorated. When the average particle diameter D ₅₀ of the positive electrode active material is too large resistance of the lithium ion secondary battery increases, there is a possibility that the output characteristics of the lithium ion secondary battery decreases.

Note that the average particle diameter D ₅₀ refers to the particle size cumulative value of the volume distribution in the particle size distribution measurement by laser diffraction method is equivalent to 50%. That is, the average particle diameter D ₅₀ means the median size measured by volume.

  The binder plays a role of connecting the positive electrode active material to the current collector. As the binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer (abbreviation FEP), fluorine-containing resin such as fluorine rubber, thermoplastic resin such as polypropylene and polyethylene, polyimide, Examples thereof include imide resins such as polyamide imide, acrylic resins such as poly (meth) acrylic acid, alkoxysilyl group-containing resins, styrene / butadiene rubber, carboxymethyl cellulose, polyethylene glycol, and polyacrylonitrile.

  The blending ratio of the binder in the positive electrode active material layer is preferably a mass ratio of positive electrode active material: binder = 1: 0.001 to 1: 0.3. The positive electrode active material: binder is more preferably 1: 0.005 to 1: 0.2, and further preferably 1: 0.01 to 1: 0.15. If the amount of the binder is too small, the moldability of the electrode may be lowered, and if the amount of the binder is too large, the energy density of the electrode may be lowered.

  A conductive support agent is added to a positive electrode active material layer as needed, in order to improve the electroconductivity of an electrode. Carbon black, graphite, acetylene black (abbreviated as AB), ketjen black (registered trademark) (abbreviated as KB), vapor-grown carbon fiber (abbreviated as VGCF), etc., which are carbonaceous fine particles, are used alone or in combination as conductive aids. These can be used in combination. Although there are no particular limitations on the amount of conductive aid used, for example, it can be about 1 to 30 parts by mass with respect to 100 parts by mass of the active material contained in the electrode.

  In order to dispose the positive electrode active material layer on the surface of the current collector, a positive electrode active material layer-forming composition containing a positive electrode active material, a binder, and, if necessary, a conductive additive is prepared. A suitable solvent may be added to form a paste, which is then applied to the surface of the current collector and then dried. In addition, you may compress the electrical power collector in which the positive electrode active material layer is arrange | positioned so that an electrode density may be raised as needed.

  As a coating method of the composition for forming a positive electrode active material layer, conventionally known methods such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, a curtain coating method, a lip coating method, a comma coating method, and a die coating method are known. A method may be used.

  As the solvent for adjusting the viscosity, water, N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone and the like can be used.

(Negative electrode)
The negative electrode has a negative electrode active material layer containing silicon. The negative electrode active material layer is disposed on the surface of the current collector. The current collector is the same as that described for the positive electrode.

(Negative electrode active material layer)
The negative electrode active material layer has a negative electrode active material. The negative electrode active material layer may contain a binder and a conductive additive as necessary. The binder and the conductive assistant are the same as those described for the positive electrode.

  The negative electrode active material contains silicon. Silicon has a high charge / discharge capacity, but has the property of expanding and contracting with the insertion and extraction of lithium (Li) during charge / discharge.

Examples of the negative electrode active material containing silicon include silicon and silicon compounds. Examples of the silicon compound include SiO _x (0.3 ≦ x ≦ 1.6), SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi _{2. , Cu 5 Si, FeSi 2,} MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SnSiO 3, LiSiO , and the present inventors, is particularly The silicon material which has the structure where the plate-shaped silicon body investigated was laminated | stacked in the thickness direction is mentioned. As the negative electrode active material containing silicon, a silicon material having a structure in which plate-like silicon bodies are laminated in the thickness direction is preferable.

  The structure of the silicon material having a structure in which the plate-like silicon bodies are laminated in the thickness direction can be confirmed by observation with a scanning electron microscope or the like. In consideration of using a silicon material as an active material of a lithium ion secondary battery, the plate-like silicon body has a thickness in the range of 10 nm to 100 nm for efficient insertion and desorption reaction of lithium ions. A thing in the range of 20 nm-50 nm is more preferable. The length of the plate-like silicon body in the major axis direction is preferably in the range of 0.1 μm to 50 μm. The plate-like silicon body preferably has a (length in the major axis direction) / (thickness) range of 2 to 1000.

The silicon material may be pulverized or classified to form particles having a certain particle size distribution. As a preferable particle size distribution of the silicon material, D ₅₀ can be exemplified within a range of 1 μm to 30 μm when measured by a general laser diffraction type particle size distribution measuring apparatus.

  X-ray diffraction measurement (XRD measurement) is performed on the silicon material, and the silicon crystallite size is calculated from the Scherrer equation using the half-value width of the diffraction peak of the Si (111) plane of the obtained XRD chart. The silicon crystallite size is preferably nano-sized. Specifically, the silicon crystallite size is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, still more preferably in the range of 1 nm to 50 nm, and particularly in the range of 1 nm to 10 nm. preferable.

The silicon material can be manufactured by the following manufacturing process. The production process includes a process of producing a layered silicon compound mainly composed of layered polysilane by reacting CaSi ₂ and an acid, and a process of producing a silicon material by heating the layered silicon compound at 300 ° C. or higher.

CaSi ₂ generally has a structure in which a Ca layer and a Si layer are laminated. CaSi ₂ may be synthesized by a known production method, or a commercially available one may be adopted. CaSi ₂ used for producing the layered silicon compound is preferably pulverized in advance.

  Acids include hydrogen fluoride, hydrogen chloride, hydrogen bromide, hydrogen iodide, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, methanesulfonic acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluoroarsenic acid, fluoro Examples include antimonic acid, hexafluorosilicic acid, hexafluorogermanic acid, hexafluorotin (IV) acid, trifluoroacetic acid, hexafluorotitanic acid, hexafluorozirconic acid, trifluoromethanesulfonic acid, and fluorosulfonic acid. These acids may be used alone or in combination.

  In addition, the acid is preferably used as an aqueous solution from the viewpoints of easy work and safety, and removal of by-products.

Acid may be used in an amount capable of providing 2 or more equivalents of protons relative CaSi _2. Therefore, in the case of a monovalent acid, the acid may be used in an amount of 2 mol or more with respect to 1 mol of CaSi ₂ .

  The reaction conditions are preferably reduced pressure conditions such as vacuum or an inert gas atmosphere, and are preferably temperature conditions of room temperature or lower such as an ice bath. What is necessary is just to set reaction time suitably.

Now, in the reaction step of reacting CaSi ₂ and an acid, the reaction formula when hydrogen chloride is used as the acid is as follows.
3CaSi ₂ + 6HCl → Si ₆ H ₆ + 3CaCl ₂

Si ₆ H ₆ which is polysilane corresponds to an ideal layered silicon compound. It can be considered that this reaction forms Si—H bonds while Ca in the layered CaSi ₂ is substituted with 2H. The layered silicon compound has a layer shape because the basic skeleton of the Si layer in the raw material CaSi ₂ is maintained.

As described above, the acid is preferably used as an aqueous solution in the reaction step of reacting CaSi ₂ with the acid. Here, since Si ₆ H ₆ can react with water, the layered silicon compound is rarely obtained only with a compound of Si ₆ H ₆ , and contains an element derived from oxygen or an acid.

  By heating the layered silicon compound at 300 ° C. or higher, hydrogen or the like is released to obtain a silicon material. The process of heating the layered silicon compound at 300 ° C. or higher is sometimes referred to as a silicon material manufacturing process.

The silicon material manufacturing process is represented by an ideal reaction formula as follows.
Si ₆ H ₆ → 6Si + 3H ₂ ↑

  However, the layered silicon compound actually used in the silicon material manufacturing process contains elements derived from oxygen and acid, and also contains inevitable impurities, so the silicon material actually obtained also contains elements derived from oxygen and acid, Further, inevitable impurities are also contained. In the silicon material, when the molar amount of silicon is 100, the molar amount of oxygen element is preferably 50 or less, and particularly preferably 40 or less. Further, when the molar amount of silicon is 100, the molar amount of the acid-derived element is preferably 8 or less, and particularly preferably 5 or less.

  The silicon material manufacturing process is preferably performed in a non-oxidizing atmosphere having a lower oxygen content than in normal air. Examples of the non-oxidizing atmosphere include a reduced pressure atmosphere including a vacuum and an inert gas atmosphere. The heating temperature is preferably in the range of 350 ° C to 1200 ° C, more preferably in the range of 400 ° C to 1200 ° C. If the heating temperature is too low, hydrogen may not be released sufficiently. On the other hand, if the heating temperature is too high, energy is wasted. What is necessary is just to set a heating time suitably according to heating temperature, and it is also preferable to determine a heating time, measuring the quantity of hydrogen etc. which escapes out of a reaction system.

  By appropriately selecting the heating temperature and the heating time, the ratio of amorphous silicon and silicon crystallites contained in the silicon material to be manufactured, and the size of the silicon crystallites can also be adjusted, and further manufactured. The shape and size of a nano-level layer containing amorphous silicon and silicon crystallites contained in the silicon material can also be prepared.

  In addition, when a silicon material is used as a negative electrode active material for a secondary battery such as a lithium ion secondary battery, the silicon material is preferably coated with carbon. The carbon may be only amorphous carbon, may be crystalline carbon, or may be a mixture of amorphous carbon and crystalline carbon.

  The method for coating the silicon material with carbon is not particularly limited. Carbon coating methods include mixing carbon powder and silicon material (for example, mechanical milling), heating the mixture obtained from the composite of resin and silicon material, and carbonizing the resin, and non-oxidizing silicon material. Examples thereof include a method (thermal CVD method) in which an organic gas is carbonized by being brought into contact with an organic gas in an atmosphere and heated.

  The content of the negative electrode active material containing silicon in the negative electrode active material layer is preferably 30 parts by mass or more and 85 parts by mass or less, and 40 parts by mass or more and 80 parts by mass or less when the negative electrode active material layer is 100 parts by mass. More preferably, it is 50 parts by mass or more and 75 parts by mass or less. By including the negative electrode active material containing silicon in the above range, the charge / discharge capacity of the battery can be increased and the life of the battery can be extended.

  The negative electrode active material may contain other negative electrode active materials in addition to the negative electrode active material containing silicon. As another negative electrode active material, a carbon-based material capable of inserting and extracting lithium, an element capable of being alloyed with lithium, a compound having an element capable of being alloyed with lithium, a polymer material, or the like can be used.

  Examples of the carbon-based material include graphite, non-graphitizable carbon, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.

  Elements that can be alloyed with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Ge, Sn, Pb. , Sb, Bi.

Examples of the compound having an element that can be alloyed with lithium include ZnLiAl, AlSb, Mg ₂ Sn, SnO _w (0 <w ≦ 2), LiSnO, and the like.

  As the polymer material, polyacetylene, polypyrrole, or the like can be used.

  As the other negative electrode active material, a carbon-based material is preferable.

The negative electrode active material is preferably in powder form. When the negative electrode active material is in a powder form, the average particle diameter D ₅₀ of the negative electrode active material is preferably 0.5 μm or more and 30 μm or less, and more preferably 1 μm or more and 20 μm or less. When the average particle diameter D ₅₀ of the negative electrode active material is too small, the specific surface area of the powder of the negative electrode active material is increased, it increases the contact area of the powder of the anode active material and the electrolyte solution, proceed decomposition of the electrolyte solution Therefore, the cycle characteristics of the lithium ion secondary battery may be deteriorated. When the average particle diameter D ₅₀ of the negative electrode active material is too large, conductivity of the whole electrode becomes uneven, charging and discharging characteristics may deteriorate.

  The negative electrode active material layer can be disposed on the surface of the current collector in the same manner as the positive electrode active material layer is disposed on the surface of the current collector.

(Separator)
The separator separates the positive electrode and the negative electrode and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. Examples of the separator include a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, polyethylene, polyester, and polyamide, or a porous film made of ceramics. The separator preferably includes a porous film made of a synthetic resin so as to easily follow expansion and contraction due to charging / discharging of the negative electrode including the silicon-based material.

  The separator made of synthetic resin may have a single layer structure using a single synthetic resin or a laminated structure in which a plurality of synthetic resin layers are stacked. The thickness of the separator is not particularly limited, but is preferably in the range of 5 μm to 100 μm, more preferably in the range of 10 μm to 50 μm, and particularly preferably in the range of 15 μm to 30 μm.

(Nonaqueous electrolyte)
The nonaqueous electrolytic solution contains a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent.

  Examples of the non-aqueous solvent include cyclic esters, chain esters, and ethers. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of the chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which part or all of hydrogen in the chemical structure of the specific non-aqueous solvent is substituted with fluorine may be employed. Examples of the compound in which part or all of hydrogen in the chemical structure of the non-aqueous solvent is fluorine-substituted include, for example, fluoroethylene carbonate and difluoroethylene carbonate.

Moreover, as an electrolyte dissolved in the non-aqueous electrolyte, for example, a lithium salt such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ can be used.

As the non-aqueous electrolyte, for example, a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3 in} a solvent such as ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate is used in an amount of 0.5 mol / l to 1. A solution dissolved at a concentration of about 7 mol / l can be used.

  A separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. The electrode body may be any of a stacked type in which a positive electrode, a separator and a negative electrode are stacked, or a wound type in which a positive electrode, a separator and a negative electrode are sandwiched. After connecting the current collector for the positive electrode and the current collector for the negative electrode to the positive electrode tab portion and the negative electrode tab portion that communicate with the outside using a current collector lead, etc., a non-aqueous electrolyte is added to the electrode body and lithium is added. An ion secondary battery is used.

  At that time, the amount of the non-aqueous electrolyte is set so as to satisfy the formula (1).

  The shape of the lithium ion secondary battery is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be employed.

  The lithium ion secondary battery can be mounted on a vehicle. Since the lithium ion secondary battery has high safety, a vehicle equipped with the lithium ion secondary battery has high safety.

  The vehicle may be a vehicle that uses electric energy from a battery as a whole or a part of a power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, an electric forklift, an electric wheelchair, and an electric assist. Bicycles and electric motorcycles are examples.

  As mentioned above, although embodiment of the lithium ion secondary battery and its manufacturing method of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Creation of positive electrode)
(Positive electrode A)
LiNi _0.5 Co _0.2 Mn _0.3 O ₂ having an average particle diameter D ₅₀ of 6 μm as a positive electrode active material, and LiFePO ₄ having an average particle diameter D ₅₀ of 1.5 μm having a carbon coating on the surface as a positive electrode active material, Acetylene black as a conductive auxiliary agent and polyvinylidene fluoride (hereinafter referred to as PVDF) as a binder were mixed in a ratio of 67 parts by mass, 27 parts by mass, 3 parts by mass, and 3 parts by mass, respectively. A positive electrode active material layer slurry was prepared by dispersing in an appropriate amount of N-methyl-2-pyrrolidone (hereinafter referred to as NMP).

Here, the true density of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ is 4.8 g / cm ³ , the true density with LiFePO ₄ is 3.6 g / cm ³ , and the true density of acetylene black is 2 g / cm 2. The true density of cm ³ and PVDF was 1.78 g / cm ³ .

An aluminum foil having a thickness of 15 μm was prepared as a current collector. The positive electrode active material layer slurry was placed on the current collector, and the positive electrode active material layer slurry was applied in a film form using a comma coater. The current collector coated with the positive electrode active material layer slurry was dried at 90 ° C. for 5 minutes and then dried at 120 ° C. for 5 minutes to volatilize and remove NMP. After coating on one side, the aluminum foil was turned over and coated on the back side in the same manner so that the same coating amount was obtained. Thereafter, the current collector and the coated material on the current collector were firmly and closely joined by a roll press. At this time, the basis weight on one side of the positive electrode active material layer was set to 27.0 mg / cm ² . Here, the basis weight of the positive electrode active material layer was calculated from the equation: mass of positive electrode active material layer (g) ÷ area of positive electrode active material layer (cm ² ). The bonded product was heated in a vacuum dryer at 120 ° C. for 6 hours. The bonded product after heating was cut into a predetermined shape (rectangular shape of 40 mm × 80 mm) to obtain a positive electrode A. The thickness of one surface of the positive electrode active material layer of the positive electrode A was 93 μm. From this, the volume of one surface of the positive electrode active material layer of the positive electrode A was calculated to be 0.2976 cm ³ .

Here, the mass of one surface of the positive electrode active material layer of the positive electrode A was 864 mg. The sum of the volume of each component contained in the positive electrode active material layer and the theoretical amount calculated from the blending amount (parts by mass) and true density of each component contained in the positive electrode active material layer is the volume of one side of the positive electrode active material layer. The void amount was calculated by subtracting from 2976 cm ³ . The amount of voids on one side of the positive electrode active material layer of positive electrode A was 0.081 ml.

(Positive electrode B)
94 parts by mass of LiNi _0.5 Co _0.2 Mn _0.3 O ₂ having an average particle diameter D ₅₀ of 6 μm as a positive electrode active material, acetylene black as a conductive additive, and PVDF as a binder, Mixing at a ratio of 3 parts by mass and 3 parts by mass, this mixture is dispersed in an appropriate amount of NMP to produce a slurry for the positive electrode active material layer, and the basis weight on one side of the positive electrode active material layer is 18.0 mg / cm ^2. A positive electrode B was produced in the same manner as the positive electrode A except that the above procedure was performed. The thickness of one surface of the positive electrode active material layer of the positive electrode B was 61 μm. From this, the volume of one surface of the positive electrode active material layer of the positive electrode B was calculated to be 0.1952 cm ³ .

Here, the mass of one surface of the positive electrode active material layer of the positive electrode B was 576 mg. The sum of the volume of each component contained in the positive electrode active material layer and the theoretical amount calculated from the blending amount (parts by mass) and true density of each component contained in the positive electrode active material layer is the volume of one side of the positive electrode active material layer. The void amount was calculated by subtracting from 1952 cm ³ . The amount of voids on one side of the positive electrode active material layer of positive electrode B was 0.052 ml.

(Positive electrode C)
A positive electrode C was produced in the same manner as the positive electrode A, except that the bonded product after heating was cut into a predetermined shape (rectangular shape of 130 mm × 101.5 mm). The thickness of one surface of the positive electrode active material layer of the positive electrode C was 93 μm. From this, the volume of one surface of the positive electrode active material layer of the positive electrode C was calculated to be 1.227 cm ³ .

Here, the mass of one surface of the positive electrode active material layer of the positive electrode C was 3.562 g. The volume of one side of the positive electrode active material layer is defined as the sum of the mass of the positive electrode active material layer and the theoretical volume of each component calculated from the blending amount (parts by mass) and true density of each component contained in the positive electrode active material layer. The void amount was calculated by subtracting from 227 cm ³ . The amount of voids on one side of the positive electrode active material layer of positive electrode C was 0.24 ml.

(Positive electrode D)
A positive electrode D was produced in the same manner as the positive electrode B, except that the bonded product after heating was cut into a predetermined shape (rectangular shape of 130 mm × 101.5 mm). The thickness of one surface of the positive electrode active material layer of the positive electrode D was 61 μm. From this, the volume of one surface of the positive electrode active material layer of the positive electrode D was calculated to be 0.805 cm ³ .

Here, the mass of one surface of the positive electrode active material layer of the positive electrode D was 2.375 g. The sum of the volume of each component contained in the positive electrode active material layer and the theoretical amount calculated from the blending amount (parts by mass) and true density of each component contained in the positive electrode active material layer is the volume of one side of the positive electrode active material layer. The void amount was calculated by subtracting from 805 cm ³ . The amount of voids on one side of the positive electrode active material layer of positive electrode D was 0.21 ml.

(Preparation of negative electrode)
(Production of silicon material)
A silicon material coated with carbon was prepared as follows.

A mixed solution of 7 ml of an aqueous HF solution having a concentration of 46% by mass and 56 ml of an aqueous HCl solution having a concentration of 36% by mass was brought to 0 ° C. in an ice bath, and 3.3 g of CaSi ₂ was added thereto and stirred in an argon gas stream. . After confirming the completion of foaming, the mixed solution was warmed to room temperature, stirred for another 2 hours at room temperature, then added with 20 ml of distilled water and further stirred for 10 minutes. At this time, yellow powder floated.

  The obtained mixed solution was filtered, and the obtained residue was washed with 10 ml of distilled water and then with 10 ml of ethanol. The residue after washing was vacuum dried to obtain 2.5 g of layered polysilane.

1 g of this layered polysilane was weighed, and a heat treatment was performed in an argon gas containing O ₂ in an amount of 1% by volume or less at 500 ° C. for 1 hour to obtain a silicon material.

The obtained silicon material was put into a rotary kiln type reactor, and a carbonization process by thermal CVD was performed under a condition of 850 ° C. and a residence time of 5 minutes under a flow of propane gas to obtain a silicon material coated with carbon. In the rotary kiln type reactor, since the silicon material is heated while being circulated in a rotary type, uneven coating of carbon hardly occurs. The rotation speed of the reactor was 1 rpm. The average particle diameter D ₅₀ of the silicon material coated with this carbon was 5 [mu] m.

(Negative electrode A)
As an anode active material, the silicon material and the average particle diameter D ₅₀ coated with carbon was prepared 15μm natural graphite. A polyamide-imide resin was prepared as a binder resin. Acetylene black was prepared as a conductive aid.

Here, the true density of the silicon material is 2.31 g / cm ^3, the true density of natural graphite 2.25 g / cm ^3, the true density of the polyamide-imide resin 1.41 g / cm ^3, the true density of the acetylene black 2g / Cm ³ .

  The negative electrode active material, the conductive auxiliary agent, and the binder resin were mixed at a mass ratio of silicon material: graphite: conductive auxiliary agent: binder resin = 58: 24: 7: 11. An appropriate amount of NMP was added as a solvent to the above mixture to prepare a negative electrode active material layer slurry.

A 20 μm copper foil was prepared as a negative electrode current collector, and the slurry for negative electrode active material layer was applied to the copper foil in a film form using a comma coater. The copper foil coated with the negative electrode active material layer slurry was dried at 80 ° C. for 5 minutes to volatilize and remove NMP. After coating on one side, the copper foil was turned over and coated on the back side in the same way so that the same coating amount was obtained. Thereafter, the current collector and the coated material on the current collector were firmly and closely joined by a roll press. At this time, the basis weight on one side of the negative electrode active material layer was set to 4.9 mg / cm ² . Here, the basis weight of the negative electrode active material layer was calculated from the equation: mass of negative electrode active material layer (g) ÷ area of negative electrode active material layer (cm ² ). The joined product was heated in a vacuum dryer at 200 ° C. for 2 hours, and then cut into a predetermined shape (rectangular shape having a negative electrode active material layer area of 44 mm × 84 mm) to form a negative electrode A. The thickness of one surface of the negative electrode active material layer of the negative electrode A was 43 μm. From this, the volume of one side of the negative electrode active material layer of the negative electrode A was calculated to be 0.1589 cm ³ .

Here, the mass of one surface of the negative electrode active material layer of the negative electrode A was 181.1 mg. The sum of the theoretical volume calculated from the mass of the negative electrode active material layer, the blending amount (parts by mass) and the true density of each component contained in the negative electrode active material layer is the volume of one side of the negative electrode active material layer. The void amount was calculated by subtracting from 1589 cm ³ . The amount of voids on one side of the negative electrode active material layer of negative electrode A was 0.065 ml.

(Negative electrode B)
A mixture of 98 parts by mass of natural graphite, 1 part by mass of styrene-butadiene rubber (hereinafter referred to as SBR) and 1 part by mass of carboxymethyl cellulose (hereinafter referred to as CMC) as a binder is used as a negative electrode active material. A negative electrode B was produced in the same manner as the negative electrode A, except that the basis weight on one side of the layer was 11 mg / cm ² .

Here, the true density of natural graphite was 2.25 g / cm ³ , the true density of SBR was 0.93 g / cm ³ , and the true density of CMC was 0.8 g / cm ³ .

The thickness of one surface of the negative electrode active material layer of the negative electrode B was about 77 μm. From this, the volume of one side of the negative electrode active material layer of the negative electrode B was calculated to be 0.2845 cm ³ .

Here, the mass of one surface of the negative electrode active material layer of the negative electrode B was 405.6 mg. The sum of the theoretical volume calculated from the mass of the negative electrode active material layer, the blending amount (parts by mass) and the true density of each component contained in the negative electrode active material layer is the volume of one side of the negative electrode active material layer. The void amount was calculated by subtracting from 2845 cm ³ . The amount of voids on one side of the negative electrode active material layer of negative electrode B was 0.108 ml.

(Negative electrode C)
Negative electrode C was produced in the same manner as negative electrode A, except that the bonded product after heating was cut into a predetermined shape (rectangular shape of 136 mm × 108.5 mm). The thickness of the negative electrode active material layer of the negative electrode C was 43 μm. From this, the volume of one surface of the negative electrode active material layer of the negative electrode C was calculated to be 0.594 cm ³ .

Here, the mass of one surface of the negative electrode active material layer of the negative electrode C was 723.0 mg. The sum of the theoretical volume calculated from the mass of the negative electrode active material layer, the blending amount (parts by mass) and the true density of each component contained in the negative electrode active material layer is the volume of one side of the negative electrode active material layer. The void amount was calculated by subtracting from 594 cm ³ . The amount of voids on one side of the negative electrode active material layer of negative electrode C was 0.374 ml.

(Negative electrode D)
A negative electrode D was produced in the same manner as the negative electrode B except that the bonded product after heating was cut into a predetermined shape (rectangular shape of 136 mm × 108.5 mm). The thickness of one surface of the negative electrode active material layer of the negative electrode D was 77 μm. From this, the volume of one side of the negative electrode active material layer of the negative electrode D was calculated to be 1.136 cm ³ .

Here, the mass of one surface of the negative electrode active material layer of the negative electrode D was 1.619 g. The volume of one side of the negative electrode active material layer is the sum of the theoretical volume calculated from the mass of the negative electrode active material layer, the blending amount (parts by mass) of each component contained in the negative electrode active material layer, and the true density. The void amount was calculated by subtracting from 136 cm ³ . The amount of voids on one side of the negative electrode active material layer of negative electrode D was 0.416 ml.

(Separator)
A porous polyethylene film was prepared as a separator. The void amount of the rectangular sheet of polyethylene film (48 mm × 88 mm, thickness 25 μm) was 0.049 ml, and the void amount of the rectangular sheet of polyethylene film (136 mm × 112 mm, thickness 25 μm) was 0.179 ml. .

<Production of laminated lithium-ion secondary battery>
(Example 1-1)
The laminate type lithium ion secondary battery of Example 1-1 was produced as follows.

  A laminate type lithium ion secondary battery was manufactured using one positive electrode A and two negative electrodes A. Specifically, a rectangular sheet (48 mm × 88 mm, thickness 25 μm) made of a porous polyethylene film as a separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then an electrolyte solution was injected into the bag-like laminated film. At this time, the total amount of voids of one positive electrode A, two negative electrodes A, and two separators was 0.52 ml, and the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids = 0.89.

As an electrolyte, ethylene carbonate (hereinafter referred to as EC), ethyl methyl carbonate (hereinafter referred to as EMC), and dimethyl carbonate (hereinafter referred to as DMC) were EC: EMC: DMC = 3: 3: 4 (volume ratio). ) Was used to dissolve LiPF ₆ to 1 mol / l. Thereafter, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. The positive electrode and the negative electrode have a tab portion that can be electrically connected to the outside, and a part of the tab portion extends to the outside of the laminated lithium ion secondary battery. Through the above steps, a laminate type lithium ion secondary battery of Example 1-1 was produced.

(Example 1-2)
A laminated lithium ion secondary battery of Example 1-2 was produced in the same manner as the laminated lithium ion secondary battery of Example 1-1 except that the size of the electrode and the number of stacked layers were changed. The positive electrode A and the positive electrode C have the same configuration except for the size of the electrodes. Similarly, the negative electrode A and the negative electrode C have the same configuration except for the size of the electrodes.

  Specifically, a laminate type lithium ion secondary battery was manufactured using 67 positive electrodes C and 68 negative electrodes C. Specifically, a rectangular sheet (136 mm × 112 mm, thickness 25 μm) made of a porous polyethylene film as a separator was sandwiched between each positive electrode and each negative electrode to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then an electrolyte solution was injected into the bag-like laminated film. At this time, the total amount of voids of the positive electrode C67 sheets, the negative electrode C68 sheets, and the separator 134 sheets was 107.0 ml, and the injection amount of the electrolytic solution was set to the electrolytic solution amount / void amount = 0.89.

(Example 2-1)
The laminate type of Example 2-1 was the same as the laminate type lithium ion secondary battery of Example 1-1, except that the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids = 0.94. A lithium ion secondary battery was produced.

(Example 2-2)
The laminate type of Example 2-2 was the same as the laminate type lithium ion secondary battery of Example 1-2 except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 0.94. A lithium ion secondary battery was produced.

(Example 3-1)
The laminate type of Example 3-1 was the same as the laminate type lithium ion secondary battery of Example 1-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 0.98. A lithium ion secondary battery was produced.

(Example 3-2)
The laminate type of Example 3-2 was the same as the laminate type lithium ion secondary battery of Example 1-2 except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 0.98. A lithium ion secondary battery was produced.

(Example 4-1)
The laminate type of Example 4-1 was the same as the laminate type lithium ion secondary battery of Example 1-1, except that the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids was 1.04. A lithium ion secondary battery was produced.

(Example 4-2)
The laminate type of Example 4-2 was the same as the laminate type lithium ion secondary battery of Example 1-2, except that the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids was 1.04. A lithium ion secondary battery was produced.

(Example 5-1)
The laminate type of Example 5-1 was the same as the laminate type lithium ion secondary battery of Example 1-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 1.11. A lithium ion secondary battery was produced.

(Example 5-2)
The laminate type of Example 5-2 was the same as the laminate type lithium ion secondary battery of Example 1-2 except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 1.11. A lithium ion secondary battery was produced.

(Example 6-1)
The laminate type of Example 6-1 was the same as the laminate type lithium ion secondary battery of Example 1-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 1.12. A lithium ion secondary battery was produced.

(Example 6-2)
The laminate type of Example 6-2 was the same as the laminate type lithium ion secondary battery of Example 1-2, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 1.12. A lithium ion secondary battery was produced.

(Comparative Example 1-1)
The laminate type of Comparative Example 1-1 was the same as the laminate type lithium ion secondary battery of Example 1-1, except that the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids = 0.79. A lithium ion secondary battery was produced.

(Comparative Example 1-2)
The laminate type of Comparative Example 1-2 was the same as the laminate type lithium ion secondary battery of Example 1-2, except that the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids = 0.79. A lithium ion secondary battery was produced.

(Comparative Example 2-1)
The laminate type of Comparative Example 2-1 was the same as the laminate type lithium ion secondary battery of Example 1-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 0.83. A lithium ion secondary battery was produced.

(Comparative Example 2-2)
The laminate type of Comparative Example 2-2 was the same as the laminate type lithium ion secondary battery of Example 1-2 except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 0.83. A lithium ion secondary battery was produced.

(Comparative Example 3-1)
The positive electrode B and the negative electrode B were used, and the amount of electrolyte solution injected was the same as that of the laminated lithium ion secondary battery of Example 1-1 except that the amount of electrolyte solution / amount of voids was 0.91. A laminated lithium ion secondary battery of Comparative Example 3-1 was produced. At this time, the total amount of voids of one positive electrode B, two negative electrodes B, and two separators was 0.634 ml.

(Comparative Example 3-2)
Using the positive electrode D and the negative electrode D, the amount of electrolyte solution injected was the same as that of the laminated lithium ion secondary battery of Example 1-2 except that the amount of electrolyte solution / amount of voids was 0.91. A laminated lithium ion secondary battery of Comparative Example 3-2 was produced. At this time, the total amount of voids in the 65 positive electrodes, 66 negative electrodes, and 130 separators was 105.5 ml.

(Comparative Example 4-1)
The laminate type of Comparative Example 4-1 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / amount of voids = 0.97. A lithium ion secondary battery was produced.

(Comparative Example 4-2)
The laminate type of Comparative Example 4-2 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-2 except that the amount of electrolyte solution injected was such that the electrolyte amount / void amount = 0.97. A lithium ion secondary battery was produced.

(Comparative Example 5-1)
The laminate type of Comparative Example 5-1 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / amount of voids was 1.05. A lithium ion secondary battery was produced.

(Comparative Example 5-2)
The laminate type of Comparative Example 5-2 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-2 except that the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids was 1.05. A lithium ion secondary battery was produced.

(Comparative Example 6-1)
The laminate type of Comparative Example 6-1 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 1.13. A lithium ion secondary battery was produced.

(Comparative Example 6-2)
The laminate type of Comparative Example 6-2 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-2 except that the amount of the electrolyte solution injected was such that the electrolyte amount / void amount = 1.13. A lithium ion secondary battery was produced.

(Comparative Example 7-1)
The laminate type of Comparative Example 7-1 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 1.21. A lithium ion secondary battery was produced.

(Comparative Example 7-2)
The laminate type of Comparative Example 7-2 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-2 except that the amount of electrolyte solution injected was such that the amount of electrolyte solution / the amount of voids = 1.21. A lithium ion secondary battery was produced.

(Comparative Example 8-1)
The laminate type of Comparative Example 8-1 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-1, except that the amount of electrolyte injected was such that the amount of electrolyte solution / the amount of voids = 1.29. A lithium ion secondary battery was produced.

(Comparative Example 8-2)
The laminate type of Comparative Example 8-2 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-2, except that the amount of electrolyte solution injected was such that the electrolyte amount / void amount = 1.29. A lithium ion secondary battery was produced.

(Comparative Example 9-1)
The laminate type of Comparative Example 9-1 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-1, except that the amount of electrolyte injected was such that the amount of electrolytic solution / amount of voids = 1.37. A lithium ion secondary battery was produced.

(Comparative Example 9-2)
The laminate type of Comparative Example 9-2 was the same as the laminate type lithium ion secondary battery of Comparative Example 3-2 except that the amount of electrolyte injected was such that the amount of electrolyte solution / amount of voids = 1.37. A lithium ion secondary battery was produced.

  Here, for example, the laminate type lithium ion secondary battery of Example 1-1 and the laminate type lithium ion secondary battery of Example 1-2 differ from each other only in the size of the electrode and the number of stacked electrodes. The configuration is the same. Hereinafter, when the test results are referred to, the results of Example 1-1 and the results of Example 1-2 may be collectively referred to as Example 1, and other examples and comparative examples may also be referred to similarly. . For example, when referred to as Example 2, it may refer to either or both of Example 2-1 and Example 2-2.

  Each of the above-described laminate type lithium ion secondary batteries has the same positive electrode material and negative electrode material, although the amount of the electrolyte is different. Specifically, the laminated lithium ion secondary batteries of Examples 1 to 6, Comparative Example 1 and Comparative Example 2 are laminated lithium ion secondary batteries having the same electrode material configuration, although the amount of the electrolyte is different. The laminated lithium ion secondary battery of 3 to Comparative Example 9 is a laminated lithium ion secondary battery having the same electrode material configuration although the amount of electrolyte is different.

<Battery resistance evaluation>
Examples 1-1, 2-1, 3-1, 4-1, 5-1, 6-1; Comparative Examples 1-1, 2-1, 3-1, 4-1, 5-1, 6- The battery resistances of the laminate type lithium ion secondary batteries 1, 7-1, 8-1 and 9-1 were measured. The battery resistance (Ω) was measured at a voltage of 20% SOC (State of charge) at a 2.5 C rate and 10 seconds of discharge.

  The battery resistance (Ω) of each laminate-type secondary battery was measured, and the battery resistance of each laminate-type lithium ion secondary battery in which the amount of electrolyte was changed with the same electrode material configuration was compared. Specifically, the batteries having the same electrode material configuration are the laminated lithium ion secondary batteries of Examples 1 to 6, Comparative Example 1 and Comparative Example 2, and the laminated lithium ion batteries of Comparative Examples 3 to 9. Next battery. The battery resistances of the laminated lithium ion secondary batteries of Examples 1 to 6, Comparative Example 1 and Comparative Example 2 are compared with each other, and the battery resistances of the laminated lithium ion secondary batteries of Comparative Examples 3 to 9 are compared with each other. Then, the battery resistance of each laminated lithium ion secondary battery increases from the high value to a certain battery resistance value as the amount of electrolyte increases in each battery material configuration, and even if the amount of electrolyte increases further. It no longer changes from a certain battery resistance. Therefore, in each battery material configuration, the value of the battery resistance that no longer changed was set to 1, and the ratio of the other battery resistance values was obtained. The value of this ratio is called normalized resistance. The results are shown in Table 1.

<Evaluation of life characteristics>
Examples 1-2, 2-2, 3-2, 4-2, 5-2, 6-2, Comparative Examples 1-2, 2-2, 3-2, 4-2, 5-2, 6- Charged up to a voltage of 85% SOC under the conditions of CC charging (constant current charging) at a temperature of 25 ° C. and a 1C rate, respectively, using laminated type lithium ion secondary batteries of 2, 7-2, 8-2 and 9-2 Then, after a 1-minute pause, a cycle test was conducted in which a cycle of 1-C rate CC discharge (constant current discharge) was discharged to a voltage of 15% SOC and paused for 1 minute for 500 cycles. The discharge capacity after 500 cycles was measured.

  The discharge capacities after 500 cycles of the laminated lithium ion secondary batteries of Examples 1 to 6, Comparative Example 1 and Comparative Example 2 were compared with each other, and 500 of the laminated lithium ion secondary batteries of Comparative Examples 3 to 9 were compared. Comparing the discharge capacities after cycling with each other, the discharge capacities after 500 cycles of each laminate-type lithium ion secondary battery change from a small value to a certain discharge capacity as the amount of the electrolytic solution increases. Even if the amount increased further, it did not change from a certain discharge capacity value. Therefore, in each battery material configuration, the value of the discharge capacity that no longer changed was set to 1, and the ratio of the other discharge capacity values was determined. The value of this ratio is referred to as the normalized life. The results are shown in Table 1.

  Comparing the amount of electrolytic solution / void amount, normalized resistance, and normalized life of Example 1 and Comparative Example 3 in Table 1, in Comparative Example 3 in which the negative electrode material does not include a material containing silicon, electrolysis is performed with respect to the void amount. When the liquid amount was about 90%, the standardized resistance was 1.31, the standardized life was 0.43, the battery resistance was high, and the discharge capacity after the 500 cycle test was also greatly reduced. On the other hand, in Example 1 having a material containing silicon as the negative electrode material, the normalized resistance is 1.12 and the normalized life is 0.90 even when the amount of the electrolyte is about 90% of the void amount. The battery resistance did not increase so much, and the discharge capacity after the 500 cycle test did not decrease so much. Therefore, compared to the case of using a negative electrode material having no silicon-containing material, the use of the negative electrode material having a silicon-containing material has a longer life even when the amount of the electrolyte of the lithium ion secondary battery is small. It was inferred that it was difficult to decrease.

  Moreover, when Examples 1-6 and Comparative Examples 3-6 are compared, battery resistance becomes high in Comparative Examples 3-6 in the range where the amount of electrolyte solution / void amount is 0.89 or more and less than 1.13, and after 500 cycle tests. In Examples 1 to 6 having a material containing silicon in the negative electrode material in a range where the electrolytic solution amount / void amount is 0.89 or more and less than 1.13, the battery resistance does not increase so much. It was found that the discharge capacity after the 500 cycle test did not decrease so much.

  Therefore, if a negative electrode containing silicon is included and the amount of electrolyte / void is in the range of 0.89 to less than 1.13, the battery resistance of the lithium ion secondary battery will not be so high, and the lifetime will not be shortened. I understood.

Claims (5)

A method for producing a lithium ion secondary battery comprising a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer containing silicon, a separator, and a non-aqueous electrolyte,
The manufacturing method of the lithium ion secondary battery characterized by including the liquid quantity setting process which sets the liquid quantity of the said non-aqueous electrolyte so that following formula (1) may be satisfy | filled.
0.89 ≦ Non-aqueous electrolyte volume (ml) / (Positive electrode active material layer void volume (ml) + Separator void volume (ml) + Negative electrode active material layer void volume (ml)) <1.13 .... Formula (1) A step of reacting CaSi ₂ with an acid to produce a layered silicon compound mainly composed of layered polysilane;
Heating the layered silicon compound at 300 ° C. or higher to produce a silicon material;
A negative electrode manufacturing process for manufacturing a negative electrode containing the silicon material;
The manufacturing method of the lithium ion secondary battery of Claim 1 which has these.   Furthermore, the manufacturing method of the lithium ion secondary battery of Claim 1 or 2 including the liquid volume calculation process of calculating the liquid volume of the said non-aqueous electrolyte so that the said Formula (1) may be satisfy | filled. Including a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer containing silicon, a separator, and a non-aqueous electrolyte,
The lithium ion secondary battery, wherein the amount of the non-aqueous electrolyte satisfies the following formula (1).
0.89 ≦ Non-aqueous electrolyte volume (ml) / (Positive electrode active material layer void volume (ml) + Separator void volume (ml) + Negative electrode active material layer void volume (ml)) <1.13 .... Formula (1)   5. The lithium ion secondary battery according to claim 4, wherein the negative electrode active material layer includes a silicon material having a structure in which plate-like silicon bodies are laminated in a thickness direction.