JP2015049991A - Method for manufacturing negative electrode mixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a negative electrode mixture which enables the enhancement of charge and discharge cycle characteristics.SOLUTION: A method for manufacturing a negative electrode mixture comprises the step of mixing up a negative electrode active material, a solid electrolyte, and a solvent with a ball-mill. The solid electrolyte satisfies the following condition: (1) LiS vs. PScomposition ratio is given as LiS:PS=72:28-78:22 (molar ratio) in terms of LiS and PSfor elements in the solid electrolyte; or (2)LiS vs. PScomposition ratio is given as LiS:PS=72:28-78:22 (molar ratio) in terms of LiS, PSand LiX (where X represents a halogen atom) for the elements in the solid electrolyte.

Description

  The present invention relates to a method for producing a negative electrode composite material.

  With the recent development of mobile communication and information electronic devices, the demand for high-capacity and lightweight lithium secondary batteries tends to increase. Most electrolytes exhibiting high lithium ion conductivity at room temperature are liquids, and many of the commercially available lithium ion secondary batteries use organic electrolytes. The lithium secondary battery using this organic electrolyte has a risk of leakage, ignition and explosion, and a battery with higher safety is desired.

  An all solid state battery using a solid electrolyte has a feature that electrolyte leakage and ignition hardly occur, but it is difficult to put it to practical use. For example, Patent Document 1 discloses a method for producing an electrode material slurry containing an active material and a solid electrolyte as a material for a negative electrode of an all-solid lithium battery. Although silicon, which is a negative electrode active material used in Patent Document 1, has a high capacity, higher cycle performance has been desired.

JP 2010-040190 A

  The objective of this invention is providing the manufacturing method of the negative electrode compound material which can improve charging / discharging cycling characteristics.

According to one form of this invention, the manufacturing method of the following negative electrode compound materials is provided.
1. Negative electrode active material,
A method for producing a negative electrode mixture comprising a step of mixing a solid electrolyte containing lithium atoms, phosphorus atoms and sulfur atoms, and a solvent using a ball mill,
The manufacturing method of the negative electrode compound material in which the said solid electrolyte satisfy | fills following (1) or (2).
(1) the composition ratio of Li ₂ S and _P 2 _{S 5} when the element in the solid electrolyte in terms of Li ₂ S and _P 2 _{S 5 is, Li 2 S: P 2 S} 5 = 72: 28~78: (2) When the element in the solid electrolyte is converted to Li ₂ S, P ₂ S ₅ and LiX (X is a halogen atom), the composition ratio of Li ₂ S and P ₂ S ₅ is 1. Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22 (molar ratio) is satisfied Negative electrode active material,
A method for producing a negative electrode mixture comprising a step of mixing a solid electrolyte containing a lithium atom, a phosphorus atom and a sulfur atom, and a solvent using a ball mill,
The solid electrolyte has a peak in at least one of 86.1 ± 0.6 ppm and 83.0 ± 1.0 ppm in the solid ³¹ PNMR spectrum, and the ratio of phosphorus atoms contained in the peak is included in all peaks The manufacturing method of the negative electrode compound material which is 62 mol% or more with respect to the phosphorus atom.
3. In the solid ³¹ PNMR spectrum, the solid electrolyte has a peak in at least one of 91.0 ± 0.6 ppm and 90.5 ± 0.6 ppm, and the ratio of phosphorus atoms contained in the peak is included in all peaks The manufacturing method of the negative electrode compound material of 2 which is less than 15 mol% with respect to the phosphorus atom which is made.
4). The manufacturing method of the negative electrode compound material in any one of 1-3 whose said negative electrode active material is silicon metal powder.
5. The manufacturing method of the negative electrode compound material in any one of 1-4 whose average particle diameter of the said negative electrode active material is 0.01 micrometer or more and 200 micrometers or less.
6). The method for producing a negative electrode mixture according to any one of 1 to 5, wherein the solvent is a hydrocarbon solvent or a polar aprotic solvent.
7). The manufacturing method of the negative mix in any one of 1-6 whose said solvent is a solvent represented by following formula (2) or (3).
Ph- (R) n (2)
(In the formula, Ph is an aromatic hydrocarbon group, and each R is independently an alkyl group.
n is an integer selected from 1 to 5)
N≡C−R ′ (3)
(In the formula, R ′ is a substituted or unsubstituted group having a main chain which is a hydrocarbon having 1 to 13 carbon atoms and a side chain which is a hydrocarbon having 1 to 13 carbon atoms, or a group having 3 to 7 carbon atoms. It is a group having a cyclic structure.)
8). The solvent is a solvent represented by the formula (3),
8. R ′ in the formula (3) is a substituted or unsubstituted group having a main chain which is a hydrocarbon having 1 to 13 carbon atoms and a side chain which is a hydrocarbon having 1 to 13 carbon atoms. A method for producing a negative electrode composite.
9. The R ′ in the formula (3) is an unsubstituted group having a main chain which is a hydrocarbon having 1 to 13 carbon atoms and a side chain which is a hydrocarbon having 1 to 13 carbon atoms. A method for producing a negative electrode composite.
10. The method for producing a negative electrode mixture according to any one of 7 to 9, wherein R ′ in the formula (3) is a hydrocarbon group having 3 and 4 carbon atoms having an unsubstituted branched structure.
11. The method for producing a negative electrode mixture according to any one of 7 to 10, wherein the solvent represented by the formula (3) is isobutyronitrile.
12 The negative electrode mixture according to any one of 1 to 11, wherein a mixing ratio of the negative electrode active material and the solid electrolyte is 10% by weight: 90% by weight to 70% by weight: 30% by weight.
13. An electrode comprising a negative electrode mixture obtained from the method for producing a negative electrode mixture according to any one of 1 to 12.
A lithium ion battery comprising the electrode according to 14.13.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the negative electrode compound material which can improve charging / discharging cycling characteristics can be provided.

It is a schematic sectional drawing of the uniaxial compression apparatus used in the Example. It is a figure which shows the measurement procedure of the space ratio (epsilon) _r accompanying the elastic recovery by a uniaxial compression apparatus in an Example.

The manufacturing method of the 1st negative electrode compound material which concerns on one form of this invention includes the process of mixing a negative electrode active material; The solid electrolyte containing a lithium atom, a phosphorus atom, and a sulfur atom; and a solvent using a ball mill, and mixes it. The solid electrolyte satisfies the following (1) or (2):
(1) the composition ratio of Li ₂ S and _P 2 _{S 5} when the element in the solid electrolyte in terms of Li ₂ S and _P 2 _{S 5 is, Li 2 S: P 2 S} 5 = 72: 28~78: (2) When the element in the solid electrolyte is converted to Li ₂ S, P ₂ S ₅ and LiX (X is a halogen atom), the composition ratio of Li ₂ S and P ₂ S ₅ is Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22 (molar ratio) is satisfied

The halogen atom is one or more selected from, for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Here, “converted” means that all the lithium atoms contained in the solid electrolyte are Li ₂ S, and all the phosphorus atoms contained in the solid electrolyte are P ₂ S ₅ . However, excessive lithium may be included in the solid electrolyte, such as when lithium is contained in the impurities in the raw material lithium sulfide, but this is excluded as not included in the above conversion.
Further, when a halogen atom is contained in the solid electrolyte, it is assumed that all the halogen atoms are compounds represented by LiX, and all of the Li content obtained by subtracting the Li content of LiX from the Li content in the solid electrolyte is Assume Li ₂ S.

  The analysis of the elemental composition of the solid electrolyte can be performed by ICP emission analysis. The ICP analysis is performed by dissolving the sample in water and adjusting the volume, and then measuring the elemental amounts of lithium, phosphorus, and, if necessary, the halogen with an ICP analyzer.

The manufacturing method of the 2nd negative electrode compound material which concerns on one form of this invention includes the process of mixing a negative electrode active material; The solid electrolyte containing a lithium atom, a phosphorus atom, and a sulfur atom; and a solvent using a ball mill, and mixes it. The solid electrolyte has a peak in at least one of 86.1 ± 0.6 ppm and 83.0 ± 1.0 ppm in the solid ³¹ PNMR spectrum, and the ratio of phosphorus atoms contained in the peak is included in all peaks It is 62 mol% or more with respect to phosphorus atoms.

In both the first negative electrode mixture production method and the second negative electrode mixture production method, a specific solid electrolyte is wet pulverized and mixed together with a negative electrode active material and a solvent, so that the negative electrode active material also becomes a medium. Thus, the solid electrolyte can be pulverized, and the solid electrolyte can be further refined. Thereby, the compactness of the negative electrode mixture (adhesion between the particles in the negative electrode mixture) is improved, and at the same time, both particles of the negative electrode active material and the solid electrolyte can be highly dispersed by wet mixing.
The obtained negative electrode mixture can form a good lithium ion conduction path and electron conduction path. Therefore, the charge / discharge cycle characteristics can be improved. In addition, the high rate characteristics during discharge can be improved.
Hereinafter, materials, implementation means, conditions, and the like used in the method for manufacturing the first and second negative electrode composites according to an embodiment of the present invention will be described.

[Solid electrolyte]
(1) 1st solid electrolyte The solid electrolyte (it may be called 1st solid electrolyte) used for the manufacturing method of the 1st negative electrode compound material which concerns on one form of this invention is a lithium atom, a phosphorus atom, and a sulfur atom. The solid electrolyte satisfies the following (1) or (2).
(1) the composition ratio of Li ₂ S and _P 2 _{S 5} when the element in the solid electrolyte in terms of Li ₂ S and _P 2 _{S 5 is, Li 2 S: P 2 S} 5 = 72: 28~78: (2) When the element in the solid electrolyte is converted to Li ₂ S, P ₂ S ₅ and LiX (X is a halogen atom), the composition ratio of Li ₂ S and P ₂ S ₅ is _{li 2 S: P 2 S 5} = 72: 28~78: 22 meet (molar ratio).

The composition ratio when converted to Li ₂ S and P ₂ S ₅ in the above (1) and (2) is preferably Li ₂ S: P ₂ S ₅ = 74: 26 to 76:24.

  The first solid electrolyte can exhibit high ionic conductivity, is difficult to hydrolyze, and is a solid electrolyte that is easily pulverized. Therefore, the negative electrode active material can also be used as a medium to pulverize the solid electrolyte, and the solid electrolyte can be further refined.

(2) a solid electrolyte used in the second manufacturing method of the negative electrode material according to an embodiment of the second solid electrolyte present invention (sometimes referred to as a second solid electrolyte), in a solid-state ³¹ PNMR spectrum, 86. It has a peak in at least one of 1 ± 0.6 ppm and 83.0 ± 1.0 ppm, and the ratio of phosphorus atoms contained in the peak is 62 mol% or more with respect to phosphorus atoms contained in all peaks.
In addition, the ratio of the phosphorus atom which produces the peaks of 86.1 ± 0.6 ppm and 83.0 ± 1.0 ppm is included in a specific peak with respect to the total amount of phosphorus atoms measured by the solid ³¹ PNMR spectrum. It means the ratio of phosphorus atoms. In the above, “all peaks” means all peaks having a peak intensity of 3% or more with respect to the maximum intensity of the peak, for example.

That the second solid electrolyte has a peak in at least one of 86.1 ± 0.6 ppm and 83.0 ± 1.0 ppm in the solid ³¹ PNMR spectrum has a PS ₄ ^3- structure. Indicates.
Moreover, the proportion of the phosphorus atoms contained in the peak of 86.1 ± 0.6 ppm and 83.0 ± 1.0 ppm is at 62 mol% or more with respect to the phosphorus atoms contained in all the peaks, the PS ₄ It is estimated that ^3- structure is 62 mol% or more of the entire structure. The ratio of phosphorus atoms contained in the peaks at 86.1 ± 0.6 ppm and 83.0 ± 1.0 ppm is preferably 65 mol% or more, more preferably 70 mol% or more.
The upper limit is not particularly specified, but is usually 99 mol% or less.

When the second solid electrolyte has PS ₄ ^3- structure and the PS ₄ ^3- structure is 62 mol% or more of the total structure, high ion conductivity can be exhibited, and hydrolysis can be performed. It is a solid electrolyte that is difficult and easy to grind. Therefore, the negative electrode active material can also be used as a medium to pulverize the solid electrolyte, and the solid electrolyte can be further refined.
Further, even when the solid electrolyte is used in the method for producing a negative electrode mixture according to one embodiment of the present invention, there is little change in the structure.

The second solid electrolyte preferably has a peak in at least one of 91.0 ± 0.6 ppm and 90.5 ± 0.6 ppm in the solid ³¹ PNMR spectrum, and the ratio of phosphorus atoms contained in the peak is , Less than 20 mol% with respect to phosphorus atoms contained in all peaks. Having a peak in at least one of 91.0 ± 0.6 ppm and 90.5 ± 0.6 ppm indicates having a P ₂ S ₇ ^4- structure.
The ratio of phosphorus atoms contained in the above 91.0 ± 0.6 ppm and 90.5 ± 0.6 ppm is more preferably less than 18 mol%, and still more preferably less than 15 mol%.
The lower limit is not particularly defined, but is usually 1 mol% or more.

(3) Solid Electrolyte Preparation Method The first solid electrolyte and the second solid electrolyte (hereinafter sometimes simply referred to as “solid electrolyte”) are all sulfide-based solids containing a lithium atom, a phosphorus atom and a sulfur atom. The sulfide-based solid electrolyte can be produced from, for example, lithium sulfide and diphosphorus pentasulfide, or lithium sulfide, simple phosphorus and simple sulfur, as well as lithium sulfide, diphosphorus pentasulfide, simple phosphorus and / or simple substance. It can also be produced from raw materials such as sulfur.
The sulfide-based solid electrolyte may be a sulfide-based solid electrolyte that is further subjected to a flame retardant treatment.

The solid electrolyte may be, for example, glass, glass ceramics, or a mixture of glass and glass ceramics. The mixture of glass and glass ceramics means that glass and glass ceramics are mixed in one particle. In the solid electrolyte to be used, the above-mentioned plural kinds of solid electrolytes may be present, or one kind of solid electrolyte may be used.
The shape of the solid electrolyte is not particularly limited, and may be a particulate body, a plate body, or a rod-shaped body.
The composition ratio of each element can be controlled by adjusting the blending amount of the raw material compound when producing the solid electrolyte.

The first solid electrolyte can be manufactured from raw materials such as lithium sulfide, diphosphorus pentasulfide, simple phosphorus and / or simple sulfur. In addition, a raw material represented by LiX (X is a halogen atom) selected from lithium fluoride, lithium chloride, lithium bromide, lithium iodide and the like can also be used.
The first solid electrolyte is preferably a solid electrolyte obtained from lithium sulfide and diphosphorus pentasulfide, or a solid electrolyte obtained from a compound represented by lithium sulfide, diphosphorus pentasulfide and LiX.

For example, when the raw materials are lithium sulfide and phosphorous pentasulfide, the first solid electrolyte is adjusted by adjusting the amount of the raw materials so that Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22. Can be manufactured.
Moreover, when the raw material is a compound represented by lithium sulfide, diphosphorus pentasulfide, and LiX, the composition ratio of lithium sulfide and diphosphorus pentasulfide is Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22. It is good to adjust the compounding quantity of a raw material so that.
The amount of the compound represented by LiX is, for example, 40 mol% or less, 5 mol% or more, and 30 mol% or less, 10 mol% or more with respect to the total amount of lithium sulfide and diphosphorus pentasulfide.

In the second solid electrolyte, for example, when the raw materials are lithium sulfide and phosphorous pentasulfide, the blending amount of the raw materials is adjusted to be Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22. Can be manufactured.
The second solid electrolyte is preferably a solid electrolyte obtained from lithium sulfide and diphosphorus pentasulfide.

As lithium sulfide, those commercially available without particular limitation can be used, but high-purity lithium sulfide is preferred.
The high-purity lithium sulfide is preferably lithium sulfide having a total content of lithium salts of sulfur oxides of 0.15% by mass or less, more preferably a total content of lithium salts of sulfur oxides of 0.1% by mass. % Lithium sulfide. The high-purity lithium sulfide is preferably lithium sulfide having a content of lithium N-methylaminobutyrate of 0.15% by mass or less, more preferably a content of lithium N-methylaminobutyrate of 0.1% by mass. % Lithium sulfide.
When the total content of the lithium salt of sulfur oxide is 0.15% by mass or less, the solid electrolyte obtained by the melt quenching method or the mechanical milling method becomes a glassy electrolyte (fully amorphous). On the other hand, if the total content of the lithium salt of sulfur oxide exceeds 0.15% by mass, the obtained electrolyte may become a crystallized product from the beginning, and the ionic conductivity of this crystallized product is low. Further, even if this crystallized product is subjected to a heat treatment, the crystallized product is not changed, and there is a possibility that a sulfide-based solid electrolyte having high ion conductivity cannot be obtained.
In addition, when the content of lithium N-methylaminobutyrate is 0.15% by mass or less, a deteriorated product of lithium N-methylaminobutyrate does not deteriorate the cycle performance of the lithium ion battery. When lithium sulfide with reduced impurities is used, a high ion conductive electrolyte can be obtained.

The method for producing lithium sulfide is not particularly limited as long as it can reduce at least the above impurities. For example, it can be obtained by purifying lithium sulfide produced by the following methods ac. Among the following production methods, the method a or b is particularly preferable.
a. A method in which lithium hydroxide and hydrogen sulfide are reacted at 0 to 150 ° C. in an aprotic organic solvent to produce lithium hydrosulfide, and then this reaction solution is dehydrosulfurized at 150 to 200 ° C. 7-330312 gazette).
b. A method in which lithium hydroxide and hydrogen sulfide are reacted at 150 to 200 ° C. in an aprotic organic solvent to directly produce lithium sulfide (see JP-A-7-330312).
c. A method of reacting lithium hydroxide and a gaseous sulfur source at a temperature of 130 to 445 ° C. (see JP-A-9-283156).

There is no restriction | limiting in particular as a purification method of the lithium sulfide obtained as mentioned above. As a preferable purification method, for example, a purification method described in International Publication No. WO2005 / 40039 and the like can be mentioned. Specifically, the lithium sulfide obtained as described above is washed at a temperature of 100 ° C. or higher using an organic solvent.
The organic solvent used for washing is preferably an aprotic polar solvent, and more preferably, the aprotic organic solvent used for lithium sulfide production and the aprotic polar organic solvent used for washing are the same. .
Examples of the aprotic polar organic solvent preferably used for washing include aprotic polar organic compounds such as amide compounds, lactam compounds, urea compounds, organic sulfur compounds, cyclic organophosphorus compounds, Or it can use suitably as a mixed solvent. In particular, N-methyl-2-pyrrolidone (NMP) is selected as a good solvent.
The amount of the organic solvent used for washing is not particularly limited, and the number of times of washing is not particularly limited, but is preferably 2 or more. Cleaning is preferably performed under an inert gas such as nitrogen or argon.
The washed lithium sulfide is dried at a temperature equal to or higher than the boiling point of the organic solvent used for washing for 5 minutes or more, preferably about 2 to 3 hours or more under an inert gas stream such as nitrogen under normal pressure or reduced pressure. Thus, lithium sulfide used in the present invention can be obtained.

As long as diphosphorus pentasulfide (P ₂ S ₅ ) is industrially manufactured and sold, it can be used without particular limitation. Further, instead of P ₂ S ₅ , simple phosphorus (P) and simple sulfur (S) in a corresponding molar ratio can be used. Simple phosphorus (P) and simple sulfur (S) can be used without particular limitation as long as they are industrially produced and sold.
The mixing molar ratio of lithium sulfide to diphosphorus pentasulfide or simple phosphorus and simple sulfur is preferably Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22, and particularly preferably Li ₂ S: P _2. S ₅ = 74: 26~76: a 24 (molar ratio). When lithium sulfide, elemental phosphorus, and elemental sulfur are raw materials, the molar ratio of Li ₂ S and P ₂ S ₅ described above is converted.

The sulfide-based solid electrolyte obtained with Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22 (molar ratio) is easy to grind, and the solid electrolyte is refined during mixing using a ball mill, and the negative electrode composite In addition to improving adhesion between particles such as negative electrode active material particles and solid electrolyte particles in the material, it is possible to highly disperse negative electrode active material particles and solid electrolyte particles by wet mixing using a solvent and a ball mill. it can. The negative electrode mixture in which the negative electrode active material particles and the solid electrolyte particles are highly dispersed can form a good lithium ion conduction path and electron conduction path.

As a method for producing a sulfide-based glass solid electrolyte, there are a melt quenching method and a mechanical milling method (MM method).
In the case of the melt quenching method, P ₂ S ₅ and Li ₂ S mixed in a predetermined amount in a mortar and pelletized are placed in a carbon-coated quartz tube and vacuum-sealed. After reacting at a predetermined reaction temperature, a sulfide-based glass solid electrolyte is obtained by putting it in ice and rapidly cooling it.
The reaction temperature at this time is preferably 400 ° C to 1000 ° C, more preferably 800 ° C to 900 ° C. Moreover, reaction time becomes like this. Preferably it is 0.1 to 12 hours, More preferably, it is 1 to 12 hours.
The quenching temperature of the reactant is usually 10 ° C. or less, preferably 0 ° C. or less, and the cooling rate is usually about 1 to 10,000 K / sec, preferably 10 to 10,000 K / sec.

In the case of the MM method, a sulfide-based glass solid electrolyte is obtained by mixing a predetermined amount of P ₂ S ₅ and Li ₂ S in a mortar and reacting them for a predetermined time using, for example, various ball mills.
The MM method using the above raw materials can be reacted at room temperature. According to the MM method, since a glass solid electrolyte can be produced at room temperature, there is an advantage that a glass solid electrolyte having a charged composition can be obtained without thermal decomposition of raw materials. Further, the MM method has an advantage that the glass solid electrolyte can be made into fine powder simultaneously with the production of the glass solid electrolyte.
In the MM method, various types such as a rotating ball mill, a rolling ball mill, a vibrating ball mill, and a planetary ball mill can be used.
As conditions for the MM method, for example, when a planetary ball mill is used, the rotational speed may be set to several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours.
Although specific examples of the sulfide-based glass solid electrolyte by the melt quenching method and the MM method have been described above, manufacturing conditions such as temperature conditions and processing time can be appropriately adjusted according to the equipment used.

Thereafter, the obtained sulfide-based glass solid electrolyte is heat-treated at a predetermined temperature as required, whereby a sulfide-based crystallized glass (glass ceramic) solid electrolyte can be generated.
The heat treatment temperature for producing the sulfide-based crystallized glass solid electrolyte is preferably 180 ° C to 330 ° C, more preferably 200 ° C to 320 ° C, and particularly preferably 210 ° C to 310 ° C.
The heat treatment time is preferably from 3 to 240 hours, particularly preferably from 4 to 230 hours, when the temperature is from 180 ° C to 210 ° C. Moreover, in the case of temperature higher than 210 degreeC and 330 degrees C or less, 0.1 to 240 hours are preferable, 0.2 to 235 hours are especially preferable, Furthermore, 0.3 to 230 hours are preferable.

[Negative electrode active material]
Examples of the negative electrode active material include carbon (carbon) -containing material, Al (aluminum) metal-containing material, Sn (tin) metal-containing material, Si (silicon) metal-containing material, etc. It is a material that contains.
Carbon materials include artificial graphite, graphite carbon fiber, resin-fired carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fiber, vapor-phase growth Examples thereof include carbon fibers, natural graphite, non-graphitizable carbon, and mixtures thereof.

Carbon materials, such as scale-like natural graphite particles, can be spheroidized by surface treatment.
The average particle size of D50 is preferably 0.1 μm or more and 80 μm or less, more preferably 1 μm or more and 80 μm or less, and further preferably 3 μm or more and 60 μm or less.

The carbon material is usually a mixture of carbon materials of different particle sizes. In the mixture of carbon materials, the carbon material having a particle size of 3 μm or less is 9% by volume or less, preferably 8.7% by volume or less, and more preferably 1% by volume or less.
When the carbon material having a particle size of 3 μm or less is 9% by volume or less, the irreversible capacity can be reduced, which contributes to improvement in cycle performance.

D50 and the particle ratio (volume%) of the carbon material having a particle size of 3 μm or less are measured by a LASER diffraction method using a Mastersizer 2000 of MALVERN and calculated from a volume-based average particle size. The measurement is performed in a slurry state.
Further, BET specific surface area of the carbon material is more preferably 0.1 m ² / g or more 500 meters ² / g or less, still more preferably 0.1 m ² / g or more ^{50 m} 2 / g or less, more preferably ^{1 m} 2 / g to 20 m ² / g.

  As the silicon metal material, silicon metal alone or an alloy containing silicon can be used, and preferably silicon alone. The silicon metal material has a theoretical capacity of, for example, 800 mAh / g or more, and a negative electrode mixture having a large energy density can be obtained by using it as a negative electrode active material.

The silicon metal material is preferably used as a silicon metal powder, and its average particle size is preferably 0.01 μm or more and 200 μm or less, more preferably 0.05 μm or more and 100 μm or less, and further preferably 0.1 μm or more and 70 μm or less. It is.
If the average particle diameter of the silicon metal particles is 0.01 μm or more, the production of the negative electrode active material becomes easy. If the average particle diameter of the silicon metal particles is 200 μm or less, a negative electrode mixture having sufficiently high cycle characteristics is obtained. It becomes possible to manufacture.
The average particle size of the silicon particles can be adjusted by, for example, pulverization, classification, and sieving, and can be confirmed by a laser diffraction particle size distribution measurement method.

[solvent]
As a solvent at the time of wet pulverization and mixing, for example, one or more solvents selected from hydrocarbon solvents and polar aprotic solvents can be used.
The hydrocarbon solvent is a solvent composed of carbon atoms and hydrogen atoms, and examples of the hydrocarbon solvent include saturated hydrocarbons, unsaturated hydrocarbons, and aromatic hydrocarbons.
Examples of the saturated hydrocarbon solvent include hexane, pentane, 2-ethylhexane, heptane, octane, decane, cyclohexane, methylcyclohexane, IP solvent 1016 (manufactured by Idemitsu Kosan Co., Ltd.), IP solvent 1620 (manufactured by Idemitsu Kosan), and the like. It is done. As the saturated hydrocarbon solvent, one or more selected from the group consisting of the above-mentioned solvents can be used.
Examples of the unsaturated hydrocarbon include hexene, heptene, cyclohexene and the like.
As aromatic hydrocarbons, toluene, xylene, ethylbenzene, decalin, 1,2,3,4-tetrahydronaphthalene, Ipsol 100 (manufactured by Idemitsu Kosan Co., Ltd.), Ipsol 150 (manufactured by Idemitsu Kosan Co., Ltd.), etc. Is mentioned.
One hydrocarbon solvent may be used alone, or two or more hydrocarbon solvents may be used.

  The water content in the hydrocarbon solvent is preferably 50 ppm (weight) or less in consideration of the reaction with the raw material and the obtained solid electrolyte. Moisture causes the modification of the sulfide-based solid electrolyte due to the reaction, and deteriorates the performance of the solid electrolyte. Therefore, the lower the water content, the better. The water content in the hydrocarbon solvent is more preferably 30 ppm or less, and further preferably 20 ppm or less.

The polar aprotic solvent is a solvent having at least one polar group and not having a proton donating property.
Examples of polar aprotic solvents include anisole, acetonitrile, isobutyronitrile, propionitrile, malononitrile, succinonitrile, fumaronitrile, trimethylsilylcyanide, N-methylpyrrolidone, triethylamine, pyridine, dimethylformamide, dimethylacetamide, nitromethane, Carbon disulfide, diethyl ether, diisopropyl ether, t-butyl methyl ether, phenyl methyl ether, dimethoxymethane, diethoxyethane, tetrahydrofuran, dioxane, trimethylmethoxysilane, dimethyldimethoxysilane, tetramethoxysilane, tetraethoxysilane, cyclohexyl Methyldimethoxysilane, acetone, methyl ethyl ketone, acetaldehyde, ethylene carbonate, propylene Boneto, dimethyl sulfoxide, methylene chloride, chloroform, dichloroethane, dichlorobenzene, hexafluoride Oro benzene, trifluoromethyl benzene and the like. As the polar aprotic solvent, one or more selected from the group consisting of the above-mentioned solvents can be used.

Examples of the polar aprotic solvent include ether solvents. The ether solvent is a solvent having at least one ether bond. The ether solvent includes a cyclic ether solvent.
Examples of the ether solvent include anisole, diethoxyethane, diethyl ether, tetrahydrofuran and the like. Among these, the cyclic ether is tetrahydrofuran.
Examples of polar aprotic solvents include nitrile solvents. A nitrile solvent is a solvent having at least one nitrile group. Examples of the nitrile solvent include isobutyronitrile, propionitrile, malononitrile, succinonitrile, and fumaronitrile.

The solvent is preferably an aromatic hydrocarbon solvent represented by the following formula (2) or a nitrile solvent represented by the following formula (3).
Ph- (R) _n (2)
(In the formula, Ph is an aromatic hydrocarbon group, and each R is independently an alkyl group.
n is an integer selected from 1 to 5 (preferably an integer of 1 or 2))
N≡C−R ′ (3)
(In the formula, R ′ is a substituted or unsubstituted group having a main chain which is a hydrocarbon having 1 to 13 carbon atoms and a side chain which is a hydrocarbon having 1 to 13 carbon atoms, or a group having 3 to 7 carbon atoms. It is a group having a cyclic structure.)

In the formula (2), examples of the aromatic hydrocarbon group of Ph include a phenyl group and a naphthacenyl group. An aromatic hydrocarbon group having 6 to 24 carbon atoms is preferable, and an aromatic hydrocarbon group having 6 to 12 carbon atoms is more preferable.
In the formula (2), R is an alkyl group, and examples thereof include a methyl group, an ethyl group, and a propyl group. The number of carbon atoms of the alkyl group is preferably 1 or more and 24 or less, and more preferably 1 or more and 12 or less.
Examples of the aromatic hydrocarbon solvent represented by the formula (2) include toluene, xylene, and ethylbenzene.

In Formula (3), R ′ is a substituted or unsubstituted group having a main chain composed of a hydrocarbon having 1 to 13 carbon atoms and a side chain composed of a hydrocarbon having 1 to 13 carbon atoms, or 3 to 3 carbon atoms. 7 groups having a cyclic structure, which may be saturated or unsaturated.
The cyclic structure of the group having a cyclic structure having 3 to 7 carbon atoms is preferably an aromatic ring structure, and the carbon number of the cyclic structure is preferably 5 or 6. The group having a cyclic structure having 3 to 7 carbon atoms is more preferably a phenyl group.

  In the formula (3), when R ′ has a substituent, the substituent is alkyl, ether, carbonyl, thio, thioxy, nitrile, nitro, amide, amino, or halogen, preferably alkyl, thio, Nitrile.

The nitrile solvent represented by the formula (3) is preferably a group having a main chain composed of an unsubstituted hydrocarbon having 1 to 13 carbon atoms and a side chain composed of a hydrocarbon having 1 to 13 carbon atoms, or R ′. A group having an unsubstituted cyclic structure having 3 to 7 carbon atoms,
More preferably, R ′ is a hydrocarbon group having 3 and 4 carbon atoms having an unsubstituted branched structure, or a group containing an unsubstituted 6-membered ring structure. Specifically, isobutyronitrile, isovaleronitrile And benzonitrile. Most preferred is isobutyronitrile.
The nitrile solvent does not degrade the solid electrolyte, and the solubility and solid dispersibility of the binder are good.

  When the solvent to be used is a mixed solvent of a hydrocarbon solvent and a polar aprotic solvent, the mixing ratio of the hydrocarbon solvent and the polar aprotic solvent is preferably 95: 5 to 5:95 (volume ratio). It is.

  In addition, you may add another solvent as needed. Specific examples include ketones such as acetone and methyl ethyl ketone, alcohols such as ethanol and butanol, esters such as ethyl acetate, and halogenated hydrocarbons such as dichloromethane and chlorobenzene.

[Other materials]
In the method for producing a negative electrode mixture according to one embodiment of the present invention, in addition to the negative electrode active material, the solid electrolyte, and the solvent, other components shown below may be used as long as the effects of the present invention are not impaired. .

[binder]
Other components include binders, fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and fluororubber; thermoplastic resins such as polypropylene and polyethylene; ethylene-propylene-diene polymer ( EPDM), sulfonated EPDM, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more.
In addition, an aqueous dispersion of cellulose or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used.

[Conductive fine particles]
Conductive fine particles that can be used as other components The conductive fine particles have an electron conductivity of 1.0 × 10 ³ S / m or more, preferably 1.0 × 10 ⁴ S / m or more, more preferably It is 1.0 × 10 ⁵ S / m or more.
The higher the conductivity of the conductive material, the higher the output density of the battery manufactured using the negative electrode mixture of the present invention, and the higher the energy density.
Examples of the conductive substance that satisfies the electronic conductivity include carbon, metal powder, metal compound, and the like, preferably carbon. Since carbon has high electrical conductivity and low specific gravity, a battery having a high output density per mass and a high energy density can be obtained.
Carbon, which is a conductive material, includes graphite, hard carbon, soft carbon, amorphous carbon, acetylene black, ketjen black, fullerene, carbon nanotubes, etc. Of these, graphite has high electrical conductivity and graphite itself. Since it functions as a negative electrode active material, it is possible to manufacture a battery having both high output density and energy density, which is more preferable.
The particle size and the like are not particularly limited as long as the conductive material is granular, but the particle size in the laser diffraction particle size distribution measurement method is preferably 0.001 μm to 100 μm, more preferably 0.01 μm to 3 μm. It is. If it is less than 0.001 μm, aggregation of primary particles occurs and handling may be difficult. On the other hand, if it is larger than 100 μm, the electrode manufactured using the electrode material for a secondary battery of the present invention may be thick.

[Mixing process]
In the method for producing a negative electrode mixture according to one embodiment of the present invention, a negative electrode active material, a solid electrolyte, and a solvent are mixed using a ball mill.
The mixing ratio of the negative electrode active material and the solid electrolyte is preferably negative electrode active material: solid electrolyte = 95 wt%: 5 wt% to 5 wt%: 95 wt%, 90 wt%: 10 wt% to 10 wt%: 90 wt%. % Is more preferable, and 85% by weight: 15% by weight to 15% by weight: 85% by weight is more preferable.

  In the method for producing a negative electrode mixture according to one aspect of the present invention, by performing a wet mechanical milling process in which a negative electrode active material, a solid electrolyte, and a solvent are mixed using a ball mill, the grain growth effect during the treatment is suppressed, The synthesis reaction can be efficiently promoted. Thereby, it is possible to obtain a glassy solid electrolyte having excellent uniformity and low content of unreacted raw materials. Further, it is possible to prevent the raw materials and reactants from sticking to the vessel wall and the like, and to improve the product yield.

  The amount of the solvent is preferably such that the raw material becomes a solution or slurry by the addition of the solvent. Usually, the amount of the raw material (total amount) added per liter of solvent is 0.01 kg or more and 1 kg or less. Preferably they are 0.1 kg or more and 1 kg or less, Most preferably, they are 0.2 kg or more and 0.8 kg or less.

Various types of grinding methods can be used for the wet mechanical milling treatment. In particular, it is preferable to use a planetary ball mill.
The planetary ball mill can efficiently generate very high impact energy by rotating the platform while the pot rotates.

  The rotation speed and rotation time of the wet mechanical milling process are not particularly limited, but the higher the rotation speed, the faster the production rate of the glassy solid electrolyte, and the longer the rotation time, the conversion rate of the raw material to the glassy solid electrolyte Becomes higher. However, if the rotational speed of the mechanical milling process is increased, the burden on the pulverizer may be increased. If the rotation time is increased, it takes time to produce a glassy electrolyte.

The balls of the ball mill may be used by mixing balls having different diameters.
In addition to the above, the temperature in the mill during MM processing may be adjusted. As conditions for the MM method, for example, when a planetary ball mill is used, the rotational speed may be set to several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours.

Since mechanical milling is performed in the presence of a solvent, the processing time can be shortened. You may heat from room temperature to 200 degreeC as needed.
The resultant after mechanical milling is dried and the solvent is removed to obtain a negative electrode mixture.

Production Example 1
[Production of solid electrolyte]
(1) Production of lithium sulfide Production and purification of lithium sulfide were carried out in the same manner as in the examples of International Publication WO2005 / 040039A1. Specifically, it is as follows.
A 10-liter autoclave equipped with a stirring blade was charged with 3326.4 g (33.6 mol) of N-methyl-2-pyrrolidone (NMP) and 287.4 g (12 mol) of lithium hydroxide, and the temperature was raised to 130 rpm at 300 rpm. . After the temperature rise, hydrogen sulfide was blown into the liquid at a supply rate of 3 liters / minute for 2 hours.
Subsequently, this reaction solution was heated in a nitrogen stream (200 cc / min) to dehydrosulfide a part of the reacted hydrogen sulfide. As the temperature increased, water produced as a by-product due to the reaction between hydrogen sulfide and lithium hydroxide started to evaporate, but this water was condensed by the condenser and extracted out of the system. While water was distilled out of the system, the temperature of the reaction solution rose, but when the temperature reached 180 ° C., the temperature increase was stopped and the temperature was kept constant. After the dehydrosulfurization reaction was completed (about 80 minutes), the reaction was completed to obtain lithium sulfide.

(2) Purification of lithium sulfide After decanting NMP in the 500 mL slurry reaction solution (NMP-lithium sulfide slurry) obtained in (1) above, 100 mL of dehydrated NMP was added and stirred at 105 ° C. for about 1 hour. . NMP was decanted at that temperature. Further, 100 mL of NMP was added, stirred at 105 ° C. for about 1 hour, NMP was decanted at that temperature, and the same operation was repeated a total of 4 times. After completion of the decantation, lithium sulfide was dried at 230 ° C. (temperature higher than the boiling point of NMP) under a nitrogen stream for 3 hours under normal pressure. The impurity content in the obtained lithium sulfide was measured.
Incidentally, lithium sulfite _(Li 2 _SO 3), the content of each sulfur oxide lithium sulfate _(Li 2 SO ₄₎ and lithium thiosulfate _{(Li 2 S 2 O 3)} , and N- methylamino acid lithium (LMAB) Was quantified by ion chromatography. As a result, the total content of sulfur oxides was 0.13% by mass, and LMAB was 0.07% by mass.

(3) Production of solid electrolyte 3.90 g of Li ₂ S having an average particle diameter of about 30 μm prepared in (2) and 6.10 g of P ₂ S ₅ (manufactured by Aldrich) having an average particle diameter of about 50 μm are produced with an alumina having a diameter of 10 mm. The container was sealed in a 500 ml alumina container containing 600 g of balls. These weighing and sealing operations were all carried out in the glove box, and all the instruments used were those that had been previously dehydrated with a dryer.
The sealed alumina container was mechanically milled at room temperature for 20 hours with a planetary ball mill (LP-4 manufactured by Ito Seisakusho) to obtain white yellow solid electrolyte glass particles. The recovery rate at this time was 65%.
The conductivity of the obtained solid electrolyte glass ceramic particles was 0.2 × 10 ⁻³ S / cm.

Production Example 2
[Preparation of silicon powder]
Using a silicon (Si) powder having an average particle size of 5 μm (purity 99.9%, manufactured by High Purity Chemical Laboratory) and toluene (made by Wako Pure Chemical Industries) deaerated by bubbling nitrogen as a solvent, a bead mill (LMZ015) Wet pulverized with Ashizawa Finetech. The pulverized slurry was vacuum-dried at 150 ° C. for 3 hours to remove the solvent and obtain silicon powder. The average particle size of the pulverized silicon powder was 0.7 μm.

Example 1
[Preparation of negative electrode mixture]
8.40 g of the silicon powder prepared in Production Example 2 as the negative electrode active material, 3.60 g of the solid electrolyte powder prepared in Production Example 1, and 12.0 g of isobutyronitrile (manufactured by Kishida Chemical) as the solvent and a diameter of 10 mm Twenty zirconia balls were put into an alumina mill pot (internal volume: 45 mL). Wet pulverization mixing (P-7, manufactured by Fritsch) was performed at a rotation speed of 370 rpm for 30 minutes. The solvent was removed by vacuum-drying the mixed slurry for 3 hours at 150 ° C. The product after removal of the solvent was mixed in a mortar for 10 minutes to obtain a silicon negative electrode mixture.
With respect to the obtained negative electrode mixture, the space ratio εr accompanied by elastic recovery and the lithium ion desorption capacity were evaluated. The results are shown in Table 1.

[Evaluation of porosity with elastic recovery of negative electrode composite]
The space ratio εr was evaluated using the uniaxial compression device shown in FIG. FIG. 1 is a schematic cross-sectional view of a uniaxial compression device. The uniaxial compression device 1 pressurizes a pressure-resistant cylindrical container 10 and a negative electrode mixture charged in the internal space of the cylindrical container 10 to form a negative electrode. The pressure rod 20 increases the density of the composite material to the true density, the measuring means (micrometer) 30 for measuring the height of the negative electrode composite material, and the fixture 40.
The cylindrical container 10 has an outer diameter of 43 mm, an inner diameter of 13 mm, a height of 40 mm, a side surface thickness of 15 mm, a bottom surface of an outer diameter of 13 mm and a thickness of 10 mm, and a cylindrical container made of SKD11 was used. . SKD11 is die steel (manufactured by Daido Steel).
The pressure rod 20 is smoothly inserted into the cylindrical container 10 and has an outer diameter of 13 mm and a length of 50 mm, and is made of SKD11. Above the pressure rod 20 is a pressing means (not shown) for applying pressure. Further, a transmission unit that transmits the displacement of the pressure rod 20 to the micrometer 30 is provided.

Next, the measurement of the space ratio ε _r accompanied by the elastic recovery by the uniaxial compression device will be described with reference to FIG.
First, the value (l ₀ ) of the micrometer in a state where no negative electrode mixture is inserted is confirmed (FIG. 2 (1)).
Next, 0.3 g of the negative electrode mixture 50 is introduced into the cylindrical container 10 to make the negative electrode mixture uniform. When the bulk density to be evaluated is large, the input amount may be 0.1 g or 0.05 g.
The pressure rod 20 is inserted into the container 10 and pressurized and compressed until the apparent density of the negative electrode mixture 50 becomes the same as the true density of the negative electrode mixture (FIG. 2 (2)). Here, “the apparent density and the true density of the negative electrode mixture 50 are the same” means that the density of the negative electrode mixture 50 is the same as the height of the negative electrode mixture in the container 10 when the density of the negative electrode mixture 50 is assumed to be the true density. It means the case where the negative electrode composite is compressed by the pressure rod 20. Note that the side surfaces of the container 10 may slightly swell outward due to pressurization by the pressurizing rod 20, but this is regarded as an error in measurement.
Next, the pressure applied by the pressure rod 20 is stopped, and the force for pressing the composite 5 with the pressure rod 20 is set to 0 (FIG. 2 (3)). After compression of the negative electrode mixture 50 the value of the micrometer while the pressure in the 0 to l _3.

Void ratio epsilon _r with elastic recovery is calculated from the following formula (A), and l ₃ -l ₀ obtained by the above procedure corresponds to the L of formula (A).
ε _r = 1− {m / (ρ _p SL)} (A)
(Where, m is the weight of the complex to be inserted into the cylindrical container.
ρ _p is the true density of the complex.
S is the area of the pressure rod.
L is the height of the composite when pressurized by a pressure rod until the apparent density of the composite inserted into the cylindrical container is equal to the true density, and then the pressure is released. Cylindrical container A cylindrical container made of SKD11 having an outer diameter of 43 mm, an inner diameter of 13 mm, a height of 40 mm, a side surface thickness of 15 mm, a bottom surface of 13 mm outer diameter and a thickness of 10 mm.
Pressure rod: rod-shaped body made of SKD11 with an outer diameter of 13 mm, a length of 50 mm. )

The true density ρ _p of the negative electrode mixture of the formula (A) can be obtained by the following formula (B) or (C).
ρ _p = {(true density of solid electrolyte in negative electrode mixture) × (weight% of solid electrolyte in negative electrode mixture) + (true density of silicon powder in negative electrode mixture) × (of silicon powder in negative electrode mixture) % By weight)} ÷ 100 (B)
ρ _p = {(true density of the solid electrolyte used when manufacturing the negative electrode mixture) × (weight of the solid electrolyte used when manufacturing the negative electrode mixture) + (used when manufacturing the negative electrode mixture) (True density of silicon powder) x (weight of silicon powder used in producing negative electrode mixture)} / (weight of solid electrolyte used in producing negative electrode mixture + used in producing negative electrode mixture) Weight of silicon powder) (C)

In Example 1, the weight m of the negative electrode mixture was 0.3 g, the true density ρ _p was 2.2033 g / cm ³ , and the height L of the negative electrode mixture after releasing the pressure by the pressure rod was 1.18 mm.

[Evaluation of ion desorption capacity of negative electrode mixture]
(1) Production of half cell 60 mg of solid electrolyte powder, which is the solid electrolyte glass prepared in Production Example 1, is put into a ceramic cylinder having a diameter of 10 mm, and pressure-molded to form an electrolyte layer (electrolyte sheet, inorganic solid electrolyte powder basis weight) : 76.4 mg / cm ² ).
Next, 4.7 mg of the prepared negative electrode mixture (weight per unit area of negative electrode mixture: 6.0 mg / cm ² ) was pressure-molded so as to be in contact with the electrolyte layer to obtain a working electrode. From the opposite side of the working electrode, a LiIn alloy foil was applied as a reference electrode and a counter electrode, followed by pressure molding. Finally, the periphery of the cell was screwed at four positions every 90 degrees to pressurize in the stacking direction. In this way, a bipolar half cell having a three-layer structure was produced.
When the atomic ratio Li / In is 0.8 or less, the LiIn alloy can be used as a reference electrode because the Li desorption reaction potential is kept constant (0.62 V vs. Li / Li ⁺ ). Is possible.

(2) Evaluation of half cell using negative electrode composite material The prepared half cell was 0.5 mA / cm ² and the potential was 0.01 Vvs. Until Li / Li ⁺ , then 0.01 V vs. Li / Li ⁺ is, by inserting Li ions until 0.127mA / cm ^2, the potential 1.52Vvs at 0.5 mA / cm ^2. Li ions were desorbed to Li / Li ⁺ . Subsequently, at 0.5 mA / cm ² , the potential was 0.01 Vvs. Until Li / Li ⁺ , continue to 0.01Vvs. Li / Li ⁺ is, by inserting Li ions until 0.127mA / cm ^2, the potential 1.52Vvs at 10 mA / cm ^2. Li ions were desorbed to Li / Li ⁺ . Table 1 shows the capacity per weight of Si contained in the working electrode when Li ions are desorbed at 10 mA / cm ² .
Next, at 1.0 mA / cm ² , the potential was 0.01 Vvs. Until Li / Li ⁺ , then 0.01 V vs. Li / Li ⁺ is, by inserting Li ions until 0.127mA / cm ^2, the potential 1.52Vvs at 1.0 mA / cm ^2. Li ions were desorbed to Li / Li ⁺ . The charge / discharge cycle was repeated under these conditions, and the Li ion desorption capacity retention rate [%] after 80 cycles (80th cycle Li ion desorption capacity / 1st cycle Li ion desorption capacity × 100) was calculated. The obtained results are shown in Table 1.

Comparative Example 1
[Preparation and Evaluation of Negative Electrode Compound]
A silicon negative electrode mixture was obtained by mixing 0.070 g of the silicon powder prepared in Production Example 2 as a negative electrode active material and 0.030 g of the solid electrolyte powder prepared in Production Example 1 for 10 minutes in an agate mortar.
The space ratio εr accompanied by elastic recovery of the obtained negative electrode composite was evaluated in the same manner as in Example 1. The results are shown in Table 1. The weight m of the negative electrode mixture was 0.3 g, the true density ρ ^p was 2.2033 g / cm ³ , and the height L of the composite after releasing the pressure by the pressure rod was 1.55 mm. It was.
Further, the ion desorption capacity of the obtained negative electrode mixture was also evaluated in the same manner as in Example 1. The results are shown in Table 1.

As shown in Table 1, in Example 1 in which the negative electrode mixture was prepared by wet pulverization and mixing in a solvent, εr was smaller than that in Comparative Example 1 in which the negative electrode mixture was prepared by mortar mixing. I understand. Moreover, the capacity | capacitance when the negative electrode compound material of Example 1 desorbs Li ion at a high rate (10 mA / cm ² ) increases, and the capacity retention rate when the Li ion desorption cycle is repeated increases. I understand that.
The smaller the εr of the negative electrode mixture, the greater the number of contact points between the Si particles and the solid electrolyte particles in the mixture. That is, the smaller the εr, the better the Li ion conduction path (between the solid electrolyte particles and the solid electrolyte particles) and the electron conduction path (between the Si particles and the Si particles), and in addition, the electrochemical reaction area (solid electrolyte-Si particles). Increase). Therefore, it is estimated that the smaller the εr, the better the high rate characteristics and cycle characteristics.

DESCRIPTION OF SYMBOLS 1 Uniaxial compression apparatus 10 Cylindrical container 20 Pressure rod 30 Micrometer 40 Fixing tool 50 Negative electrode compound material

Claims (12)

Negative electrode active material,
A method for producing a negative electrode mixture comprising a step of mixing a solid electrolyte containing a lithium atom, a phosphorus atom and a sulfur atom, and a solvent using a ball mill,
The manufacturing method of the negative electrode compound material in which the said solid electrolyte satisfy | fills following (1) or (2).
(1) the composition ratio of Li ₂ S and _P 2 _{S 5} when the element in the solid electrolyte in terms of Li ₂ S and _P 2 _{S 5 is, Li 2 S: P 2 S} 5 = 72: 28~78: (2) When the element in the solid electrolyte is converted to Li ₂ S, P ₂ S ₅ and LiX (X is a halogen atom), the composition ratio of Li ₂ S and P ₂ S ₅ is Li ₂ S: P ₂ S ₅ = 72: 28 to 78:22 (molar ratio) is satisfied   The method for producing a negative electrode mixture according to claim 1, wherein the negative electrode active material is silicon metal powder.   3. The method for producing a negative electrode mixture according to claim 1, wherein the negative electrode active material has an average particle diameter of 0.01 μm to 200 μm.   The method for producing a negative electrode mixture according to any one of claims 1 to 3, wherein the solvent is a hydrocarbon solvent or a polar aprotic solvent. The said solvent is a solvent represented by following formula (2) or (3), The manufacturing method of the negative mix in any one of Claims 1-4.
Ph- (R) _n (2)
(In the formula, Ph is an aromatic hydrocarbon group, and each R is independently an alkyl group.
n is an integer selected from 1 to 5)
N≡C−R ′ (3)
(In the formula, R ′ is a substituted or unsubstituted group having a main chain which is a hydrocarbon having 1 to 13 carbon atoms and a side chain which is a hydrocarbon having 1 to 13 carbon atoms, or a group having 3 to 7 carbon atoms. It is a group having a cyclic structure.) The solvent is a solvent represented by the formula (3),
6. R ′ in the formula (3) is a substituted or unsubstituted group having a main chain which is a hydrocarbon having 1 to 13 carbon atoms and a side chain which is a hydrocarbon having 1 to 13 carbon atoms. The manufacturing method of the negative electrode compound material as described in any one of.   R 'in the formula (3) is an unsubstituted group having a main chain which is a hydrocarbon having 1 to 13 carbon atoms and a side chain which is a hydrocarbon having 1 to 13 carbon atoms. The manufacturing method of negative electrode compound material as described in any one of.   The method for producing a negative electrode mixture according to any one of claims 5 to 7, wherein R 'in the formula (3) is a hydrocarbon group having 3 and 4 carbon atoms having an unsubstituted branched structure.   The method for producing a negative electrode mixture according to any one of claims 5 to 8, wherein the solvent represented by the formula (3) is isobutyronitrile.   10. The negative electrode mixture according to claim 1, wherein a mixing ratio of the negative electrode active material and the solid electrolyte is 10 wt%: 90 wt% to 70 wt%: 30 wt%.   The electrode containing the negative electrode compound material obtained from the manufacturing method of the negative electrode compound material in any one of Claims 1-10. A lithium ion battery comprising the electrode according to claim 11.

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