Method for producing sulfide solid electrolyte and method for pulverizing sulfide solid electrolyte material

Abstract

To provide a method for producing a sulfide solid electrolyte that does not show a decrease in ionic conductivity even when using the wet grinding process.SOLUTION: The inventive method includes wet-grinding a ground material that contains a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): R1-COO-R2 where R1 is a C1-10 monovalent hydrocarbon group and R2 is a C2-10 monovalent hydrocarbon group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a sulfide solid electrolyte, a method for pulverizing a sulfide solid electrolyte material, and a sulfide solid electrolyte. [Background technology]

[0002] Due to their high energy density, lithium ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. The lithium ion secondary batteries generally have a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring lithium ions between the electrodes. Furthermore, capacitors such as lithium ion capacitors are also widely used as energy storage elements other than lithium ion secondary batteries.

[0003] In recent years, energy storage elements have been proposed that use solid electrolytes such as sulfide solid electrolytes as the nonaqueous electrolyte, instead of nonaqueous electrolyte solutions in which an electrolyte salt is dissolved in a liquid such as an organic solvent. To obtain a high-performance solid electrolyte, it is necessary to microparticulate the sulfide solid electrolyte material. As a method for microparticulating the sulfide solid electrolyte material, a method for producing sulfide-based solid electrolyte glass has been proposed, which uses wet milling and includes a step of milling and reacting raw materials in a hydrocarbon solvent (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-25098 Summary of the Invention [Problem to be solved by the invention]

[0005] The wet grinding is preferable because it can uniformly mix the raw material compounds. However, when the sulfide solid electrolyte material is ground using the wet grinding method of the conventional technique, there is a risk that the ionic conductivity will decrease.

[0006] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a method for producing a sulfide solid electrolyte, which can provide a sulfide solid electrolyte in which a decrease in ionic conductivity is suppressed even when a wet grinding method is used. [Means for solving the problem]

[0007] A method for producing a sulfide solid electrolyte according to one aspect of the present invention includes wet-pulverizing a material to be ground that includes a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): R 1 -COO-R 2 ···(1) In formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms.

[0008] A method for grinding a sulfide solid electrolyte material according to another aspect of the present invention includes wet-grinding a material to be ground that includes a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula 1: R 1 -COO-R 2 ··· (1) In formula (1), R 1 and R 2 is an unsubstituted monovalent hydrocarbon group having from 2 to 10 carbon atoms.

[0009] A sulfide solid electrolyte according to another aspect of the present invention is a wet-ground material containing a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): R 1 -COO-R 2 ···(1) In formula (1), R 1R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms. [Effects of the Invention]

[0010] According to the method for producing a sulfide solid electrolyte according to one aspect of the present invention, even when a wet pulverization method is used, a sulfide solid electrolyte in which a decrease in ionic conductivity is suppressed can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an image of Example 1 observed by a scanning electron microscope. [Figure 2] FIG. 2 is an image of Comparative Example 1 observed with a scanning electron microscope. [Figure 3] FIG. 3 is an image of the reference example observed under a scanning electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0012] First, an outline of the method for producing a sulfide solid electrolyte, the method for pulverizing a sulfide solid electrolyte material, and the sulfide solid electrolyte disclosed in this specification will be described.

[0013] A method for producing a sulfide solid electrolyte according to one aspect of the present invention includes wet-pulverizing a material to be ground that includes a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): R 1 -COO-R 2 ···(1) In formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms.

[0014] The method for producing the sulfide solid electrolyte includes wet-grinding a material containing a sulfide solid electrolyte material and a solvent containing the compound, and 1 and R 2When the number of carbon atoms in the sulfide is within the above range, a sulfide solid electrolyte can be obtained in which the decrease in ion conductivity is suppressed even when a wet pulverization method is used. The reason why such an effect occurs is not clear, but the following reason is presumed. The compound contained in the solvent used for the wet pulverization has an ester group, and this ester group is provided with R, which is a monovalent hydrocarbon group having one or more carbon atoms. 1 and R is a monovalent hydrocarbon group having two or more carbon atoms. 2 It is thought that the bond of R reduces the reactivity with sulfide solid electrolyte materials due to steric hindrance. 1 and R 2 is a monovalent hydrocarbon group having 10 or less carbon atoms, the compound is more likely to evaporate in the drying step after wet pulverization, facilitating removal of the solvent. Therefore, even when the wet pulverization method is used, the method for producing a sulfide solid electrolyte can provide a sulfide solid electrolyte in which a decrease in ionic conductivity is suppressed. Here, "wet pulverization" refers to a method of mechanically pulverizing a material in the presence of a liquid.

[0015] In the method for producing a sulfide solid electrolyte, it is preferable that the following formulas (2) and (3) be satisfied, where a [g] is the mass of the solvent excluding the compound, b [g] is the mass of the compound, and c [g] is the mass of the sulfide solid electrolyte material. 0.10≦b / (a+b+c)≦0.90 (2) 0.10≦c / (a+b+c)≦0.50 (3) When b / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte material is easily dispersed in the solvent, allowing for efficient wet-pulverization. When b / (a+b+c) is equal to or less than the upper limit, the solvent can be efficiently removed in the drying step after wet-pulverization. Furthermore, when c / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte after wet-pulverization can maintain high ionic conductivity. Furthermore, a large amount of sulfide solid electrolyte material can be pulverized by wet-pulverization at one time, improving productivity. When c / (a+b+c) is equal to or less than the upper limit, the sulfide solid electrolyte material is easily dispersed in the solvent, allowing for efficient wet-pulverization.

[0016] A method for grinding a sulfide solid electrolyte material according to another aspect of the present invention includes wet-grinding a material to be ground that includes a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula 1: R 1 -COO-R 2 ···(1) In formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms.

[0017] The method for pulverizing a sulfide solid electrolyte material includes wet-pulverizing a material containing a sulfide solid electrolyte material and a solvent containing the compound, and 1 and R 2 When the number of carbon atoms in the sulfide is within the above range, a sulfide solid electrolyte can be obtained in which the decrease in ion conductivity is suppressed even when a wet pulverization method is used. The reason why such an effect occurs is not clear, but the following reason is presumed. The compound contained in the solvent used for the wet pulverization has an ester group, and this ester group is provided with R, which is a monovalent hydrocarbon group having one or more carbon atoms. 1 and R is a monovalent hydrocarbon group having two or more carbon atoms. 2 It is thought that the bond of R reduces the reactivity with sulfide solid electrolyte materials due to steric hindrance. 1 and R 2 is a monovalent hydrocarbon group having 10 or less carbon atoms, the compound is more likely to evaporate in the drying step after wet pulverization, facilitating removal of the solvent. Therefore, it is presumed that the method for pulverizing the sulfide solid electrolyte material can obtain a sulfide solid electrolyte in which a decrease in ionic conductivity is suppressed, even when the wet pulverization method is used.

[0018] In the method for pulverizing a sulfide solid electrolyte material, when the mass of the solvent excluding the compound is a [g], the mass of the compound is b [g], and the mass of the sulfide solid electrolyte material is c [g], it is preferable that the following formulas (2) and (3) are satisfied: 0.10≦b / (a+b+c)≦0.90 (2) 0.10≦c / (a+b+c)≦0.50 (3) When b / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte material is easily dispersed in the solvent, allowing for efficient wet-pulverization. When b / (a+b+c) is equal to or less than the upper limit, the solvent can be efficiently removed in the drying step after wet-pulverization. Furthermore, when c / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte after wet-pulverization can maintain high ionic conductivity. Furthermore, a large amount of sulfide solid electrolyte material can be pulverized by wet-pulverization at one time, improving productivity. When c / (a+b+c) is equal to or less than the upper limit, the sulfide solid electrolyte material is easily dispersed in the solvent, allowing for efficient wet-pulverization.

[0019] A sulfide solid electrolyte according to another aspect of the present invention is a wet-ground material containing a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): R 1 -COO-R 2 ···(1) In formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms.

[0020] The sulfide solid electrolyte is a wet-ground material containing a sulfide solid electrolyte material and a solvent containing a compound represented by the above formula (1), and R 1 and R 2 The decrease in ionic conductivity is suppressed by the number of carbon atoms being within the above range. The reason for this effect is not clear, but the following reason is presumed. The compound contained in the solvent, which is the material for the grinding material used to obtain the wet-ground product, has an ester group, and this ester group is provided with R, a monovalent hydrocarbon group having one or more carbon atoms. 1 and R is a monovalent hydrocarbon group having two or more carbon atoms. 2It is thought that the bond of R reduces the reactivity with sulfide solid electrolyte materials due to steric hindrance. 1 and R 2 is a monovalent hydrocarbon group having 10 or less carbon atoms, the solvent can be easily removed from the wet-ground product. Therefore, it is presumed that the sulfide solid electrolyte is prevented from decreasing in ionic conductivity even when it is a wet-ground product.

[0021] A method for producing a sulfide solid electrolyte, a method for pulverizing a sulfide solid electrolyte material, and a sulfide solid electrolyte according to an embodiment of the present invention will be described in detail. Note that the names of the components used in each embodiment may differ from the names of the components used in the background art.

[0022] <Method of manufacturing sulfide solid electrolyte> A method for producing a sulfide solid electrolyte according to one embodiment of the present invention includes wet-pulverizing a material to be ground, the material including a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1) (wet-pulverizing step). R 1 -COO-R 2 ···(1) In formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms. Furthermore, the method for producing a sulfide solid electrolyte according to one embodiment of the present invention preferably includes heating the sulfide solid electrolyte material before undergoing the wet-pulverization step or the sulfide solid electrolyte after undergoing the wet-pulverization step (heating step).

[0023] [Wet grinding process] In this step, a material to be ground containing a sulfide solid electrolyte material and a solvent containing the compound is wet-ground.

[0024] (Sulfide solid electrolyte material) Examples of sulfide solid electrolyte materials include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-Li3N, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S 2n (where m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In.) Li 10 GeP2S 12 Examples include: In addition to the above compounds, the compound may also include, for example, lithium-containing compounds such as Li2CO3 and metallic lithium; phosphorus-containing compounds such as P2S3, P2O5, P3N5, and elemental phosphorus; sulfur-containing compounds such as Al2S3, MgS, and elemental sulfur; halides such as MgCl2, MgBr2, MgI2, CaCl2, CaBr2, and CaI2; oxides such as MgO and CaO; and nitrides such as Mg3N2. Furthermore, the compound may also include compounds containing elements other than the above-mentioned elements. These compounds may be used alone or in combination of two or more.

[0025] (solvent) The solvent used in the wet grinding step contains a compound represented by the following formula (1). R 1 -COO-R 2 ···(1)

[0026] In the above formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms. 1 and R 2When R is a monovalent hydrocarbon group having a carbon number equal to or greater than the lower limit, the reactivity with the sulfide material is reduced due to steric hindrance. 1 and R 2 When the carbon number of the monovalent hydrocarbon group is 10 or less, the compound is easily evaporated in the drying step after wet grinding, and the solvent can be easily removed.

[0027] Above R 1 and R 2 Examples of the R include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups, cycloalkyl groups such as cyclopentyl and cyclohexyl groups, and aromatic hydrocarbon groups such as phenyl and benzyl groups. 1 and R 2 As the alkyl group, a hydrocarbon group having no hydrophilic substituent is preferred, and an unsubstituted hydrocarbon group is more preferred.

[0028] The above compounds are ester compounds, and specific examples of the ester compounds include ethyl butyrate, butyl butyrate, butyl isobutyrate, and butyl acetate.

[0029] The solvent used in the wet grinding step may further contain a solvent other than the compound represented by formula (1). The other solvent is not particularly limited, and for example, a hydrocarbon solvent can be used. Examples of the hydrocarbon solvent include pentane, hexane, heptane, octane, nonane, decane, 2-methylhexane, decalin, tetralin, benzene, xylene, and toluene. A mixture of these solvents can also be used. Among these, heptane is preferred. In the present invention, a low water content of the solvent is preferred. Specifically, the water content of the solvent is preferably 30 ppm or less, and more preferably 10 ppm or less. By keeping the water content of the solvent below the upper limit, a decrease in the ionic conductivity of the sulfide solid electrolyte material can be suppressed.

[0030] In the method for producing a sulfide solid electrolyte, where a [g] is the mass of the solvent excluding the compound, b [g] is the mass of the compound, and c [g] is the mass of the sulfide solid electrolyte material, the lower limit of b / (a+b+c) is preferably 0.10, more preferably 0.20, and even more preferably 0.30. When b / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte material is easily dispersed in the solvent, thereby enabling efficient wet-pulverization. Furthermore, the sulfide solid electrolyte after wet-pulverization can maintain high ionic conductivity. On the other hand, the upper limit of b / (a+b+c) is preferably 0.90, more preferably 0.80, and even more preferably 0.70. When b / (a+b+c) is equal to or less than the upper limit, the solvent can be efficiently removed in the drying step after wet-pulverization. Furthermore, the sulfide solid electrolyte after wet-pulverization can maintain high ionic conductivity. Furthermore, from the viewpoint of the ionic conductivity of the sulfide solid electrolyte after wet pulverization, it is more preferable that b / (a+b+c) be 0.30 or more and 0.70 or less.

[0031] The lower limit of b / (a+b) is preferably 0.12, more preferably 0.15. Alternatively, b / (a+b) may be 1.00. When b / (a+b) is equal to or greater than the lower limit, a sulfide solid electrolyte having a higher effect of suppressing a decrease in ion conductivity can be obtained.

[0032] The lower limit of c / (a+b+c) is preferably 0.10, more preferably 0.13, and even more preferably 0.15. When c / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte after wet pulverization can maintain high ionic conductivity. Furthermore, a large amount of sulfide solid electrolyte material can be pulverized by wet pulverization at one time, improving productivity. On the other hand, the upper limit of c / (a+b+c) is preferably 0.50, more preferably 0.40, and even more preferably 0.30. When c / (a+b+c) is equal to or less than the upper limit, the sulfide solid electrolyte material can be easily dispersed in the solvent, thereby enabling efficient wet pulverization.

[0033] (wet grinding) The method for producing the sulfide solid electrolyte comprises wet pulverization. By including wet pulverization, the raw material compounds can be mixed more uniformly. The wet pulverization is preferably performed by mechanical milling. Examples of mechanical milling include milling using a container-driven mill, a media-agitating mill, a high-speed rotary pulverizer, a roller mill, a jet mill, etc. Examples of container-driven mills include a rotary mill, a vibration mill, a planetary mill, etc. Examples of media-agitating mills include an attritor, a bead mill, etc. Examples of milling using a high-speed rotary pulverizer include a hammer mill, a pin mill, etc. Among these, a container-driven mill is preferred, and a planetary mill is particularly preferred.

[0034] The upper limit of the drying temperature after the wet mechanical milling is preferably lower than the crystallization temperature of the sulfide solid electrolyte material. The lower limit of the drying temperature is not particularly limited as long as the solvent containing the compound represented by formula (1) can be removed by drying. The upper limit of the drying time is preferably 10 hours or less, more preferably 5 hours or less. By setting the drying time to the upper limit or less, re-aggregation of the finely divided sulfide solid electrolyte can be suppressed. For the drying, a hot plate, a drying furnace, an electric furnace, or the like can be used.

[0035] The average particle size of the sulfide solid electrolyte after the wet-pulverization step is preferably, for example, 0.10 μm or more and 10 μm or less. By setting the average particle size of the sulfide solid electrolyte to the above-mentioned lower limit or more, a decrease in the ionic conductivity of the sulfide solid electrolyte can be suppressed. By setting the average particle size of the sulfide solid electrolyte to the above-mentioned upper limit or less, the contact area between the sulfide solid electrolyte and the active material can be improved. The "average particle size" refers to the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50% based on the particle size distribution measured by laser diffraction / scattering in accordance with JIS-Z-8825 (2013) for a diluted solution obtained by diluting particles with a solvent. The average particle size of the sulfide solid electrolyte can be adjusted by controlling the wet-pulverization conditions.

[0036] [Heating process] In this step, the sulfide solid electrolyte material before undergoing the wet-pulverization step or the sulfide solid electrolyte after undergoing the wet-pulverization step is heated (heat-treated). As a result, a sulfide solid electrolyte in which at least a portion is crystallized is obtained. The heating (heat treatment) may be performed under a reduced pressure atmosphere or an inert gas atmosphere such as argon. For sulfide solid electrolytes that are heated (heat-treated) at high temperatures, such as the argyrodite-type sulfide solid electrolyte described below, the sulfide solid electrolyte material can be subjected to the wet-pulverization step after the heating step to suppress aggregation of the sulfide solid electrolyte due to heating (heat treatment).

[0037] The sulfide solid electrolyte obtained by the heating step has at least a part of a crystalline structure. The crystalline structure of the sulfide solid electrolyte may be an LGPS type, an argyrodite type, or a Li7P3S 11 , HICP (High Ion Conduction Phase: a metastable phase with high ionic conductivity formed by a sulfide solid electrolyte containing Li, P, S, and specific elements), Thio-LISICON system, and the like.

[0038] The heating temperature in the heating step is preferably 350°C or higher and lower than 700°C, more preferably 400°C or higher and 600°C or lower, in the case of LGPS type and argyrodite type. 11 In the case of HICP, the heating temperature is preferably 200°C or higher and lower than 400°C, and more preferably 250°C or higher and 350°C or lower. In the case of HICP, the heating temperature is preferably 100°C or higher and lower than 350°C, and more preferably 150°C or higher and 300°C or lower. In the case of Thio-LISICON-based materials, the heating temperature is preferably 150°C or higher and lower than 350°C, and more preferably 200°C or higher and 300°C or lower. By setting the heating temperature within the above range, crystallization progresses sufficiently, and a sulfide solid electrolyte with higher ion conductivity can be obtained.

[0039] The lower limit of the ionic conductivity at 25°C of the sulfide solid electrolyte produced by this method for producing a sulfide solid electrolyte is preferably 0.50 mS / cm, more preferably 1.0 mS / cm, and even more preferably 1.5 mS / cm. When the ionic conductivity of the sulfide solid electrolyte at 25°C is equal to or greater than this lower limit, the charge / discharge performance of an energy storage device including the sulfide solid electrolyte can be further improved. The upper limit of the ionic conductivity is not particularly limited and may be, for example, 100 mS / cm.

[0040] The ionic conductivity of the sulfide solid electrolyte was determined by measuring AC impedance as follows. In an argon atmosphere with a dew point of -50°C or less, 120 mg of sample powder was placed in a powder molder with an inner diameter of 10 mm and then uniaxially pressed at 50 MPa or less using a hydraulic press. After releasing the pressure, 120 mg of SUS316L powder was placed on the top surface of the sample as a current collector and then uniaxially pressed at 50 MPa or less using a hydraulic press. Next, 120 mg of SUS316L powder was placed on the bottom surface of the sample as a current collector and then uniaxially pressed at 360 MPa for 5 minutes to obtain a pellet for ionic conductivity measurement. This pellet for ionic conductivity measurement was inserted into a Hohsen HS cell, and AC impedance measurement was performed at a specified temperature. The measurement conditions were an applied voltage amplitude of 20 mV, a frequency range of 1 MHz to 100 mHz, and a measurement temperature of 25°C.

[0041] The sulfide solid electrolyte produced by the method for producing a sulfide solid electrolyte can be suitably used as an electrolyte for storage elements such as lithium ion secondary batteries, particularly lithium ion storage elements. In particular, it can be suitably used as an electrolyte for all-solid-state batteries. The sulfide solid electrolyte can be used in any of the positive electrode layer, separator layer, negative electrode layer, etc., of the storage element.

[0042] According to the method for producing a sulfide solid electrolyte, even when a wet pulverization method is used, it is possible to obtain a sulfide solid electrolyte in which a decrease in ion conductivity is suppressed, and also to obtain a sulfide solid electrolyte in the form of fine particles.

[0043] <Method for crushing sulfide solid electrolyte material> A method for pulverizing a sulfide solid electrolyte material according to one embodiment of the present invention includes wet-pulverizing a material to be ground, the material including a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): R 1 -COO-R 2 ···(1) In formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms. The method for pulverizing a sulfide solid electrolyte material includes wet-pulverizing a material containing a sulfide solid electrolyte material and a solvent containing the compound, and 1 and R 2 When the number of carbon atoms is within the above range, a sulfide solid electrolyte in which a decrease in ion conductivity is suppressed can be obtained even when a wet pulverization method is used.

[0044] In the method for pulverizing a sulfide solid electrolyte material, when the mass of the solvent excluding the compound is a [g], the mass of the compound is b [g], and the mass of the sulfide solid electrolyte material is c [g], it is preferable that the following formulas (2) and (3) are satisfied: 0.10≦b / (a+b+c)≦0.90 (2) 0.10≦c / (a+b+c)≦0.50 (3) When b / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte material is easily dispersed in the solvent, allowing for efficient wet-pulverization. When b / (a+b+c) is equal to or less than the upper limit, the solvent can be efficiently removed in the drying step after wet-pulverization. Furthermore, when c / (a+b+c) is equal to or greater than the lower limit, the sulfide solid electrolyte after wet-pulverization can maintain high ionic conductivity. Furthermore, a large amount of sulfide solid electrolyte material can be pulverized by wet-pulverization at one time, improving productivity. When c / (a+b+c) is equal to or less than the upper limit, the sulfide solid electrolyte material is easily dispersed in the solvent, allowing for efficient wet-pulverization.

[0045] The details of the wet-pulverization step in the pulverization method for the sulfide solid electrolyte material are the same as those of the wet-pulverization step in the production method for the sulfide solid electrolyte.

[0046] <Sulfide solid electrolyte> The sulfide solid electrolyte is a wet-ground material containing a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1). R 1 -COO-R 2 ···(1) In formula (1), R 1 R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. 2 is a monovalent hydrocarbon group having 2 to 10 carbon atoms. The sulfide solid electrolyte is a wet-ground material containing a sulfide solid electrolyte material and a solvent containing a compound represented by the above formula (1), and R 1 and R 2 When the number of carbon atoms is within the above range, a decrease in ionic conductivity is suppressed.

[0047] The configuration of the wet-pulverized sulfide solid electrolyte is the same as that described in the wet-pulverization step in the method for producing a sulfide solid electrolyte.

[0048] <Other embodiments> The method for producing a sulfide solid electrolyte, the method for pulverizing a sulfide solid electrolyte material, and the sulfide solid electrolyte of the present invention are not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment or well-known technology. Furthermore, part of the configuration of one embodiment can be deleted. Also, well-known technology can be added to the configuration of one embodiment.

[0049] <Example> The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0050] [Examples 1 to 6, Comparative Examples 1 and 2] (Wet grinding process) A crushed material was prepared containing a sulfide solid electrolyte material made of Li6PS5Cl and a solvent having the composition shown in Table 1. In Table 1, "-" indicates that the corresponding component was not contained. The ground material was placed in a sealed 80 mL zirconia pot containing 70 g of 1 mm diameter zirconia balls, and wet mechanical milling was performed for 20 hours at a revolution speed of 200 rpm using a planetary ball mill (FRITSCH, model number Premium line P-7).

[0051] (Heating process) The sulfide solid electrolyte after the wet grinding step was taken out of the zirconia pot and heated (dried) at 100°C for 3 hours under vacuum to remove the solvent.

[0052] [Reference example] The sulfide solid electrolyte material before undergoing the wet grinding process was used as a reference example.

[0053] [evaluation] (ionic conductivity) The ionic conductivity (σ) at 25°C of the sulfide solid electrolytes obtained by the manufacturing methods of each of the Examples and Comparative Examples and the sulfide solid electrolyte material of the Reference Example 25 ) was determined by measuring AC impedance using the method described above using a Bio-Logic VMP-300. The measurement results are shown in Table 1.

[0054] (Relative value of ionic conductivity) The ratio (%) of the ionic conductivity at 25°C of the sulfide solid electrolyte obtained by the manufacturing method of each Example and Comparative Example to the sulfide solid electrolyte material of the Reference Example was calculated as a relative value of ionic conductivity. The results are shown in Table 1.

[0055] (Evaluation of particle size of sulfide solid electrolyte) The sulfide solid electrolytes obtained by the manufacturing methods of Example 1 and Comparative Example 1 and the sulfide solid electrolyte material of the Reference Example were observed using a scanning electron microscope (SEM). Fig. 1 shows an SEM image of the sulfide solid electrolyte obtained by the manufacturing method of Example 1, Fig. 2 shows an SEM image of the sulfide solid electrolyte obtained by the manufacturing method of Comparative Example 1, and Fig. 3 shows an SEM image of the sulfide solid electrolyte material of the Reference Example.

[0056] [Table 1]

[0057] As shown in Table 1, the sulfide solid electrolytes of Examples 1 to 6, which were produced by wet-pulverizing a powder containing a sulfide solid electrolyte material and a solvent containing the compound represented by the above formula 1, had sufficiently high ionic conductivity compared to Comparative Examples 1 and 2. Furthermore, from the SEM images of Example 1, Comparative Example 1, and Reference Example shown in FIGS. 1 to 3, it can be seen that the sulfide solid electrolyte obtained by the production method of Example 1 is a finer particle compared to the sulfide solid electrolyte material of the Reference Example, and is refined to the same extent as the sulfide solid electrolyte obtained by the production method of Comparative Example 1.

[0058] The above results demonstrate that the method for producing a sulfide solid electrolyte can provide a sulfide solid electrolyte in which a decrease in ionic conductivity is suppressed, even when a wet pulverization method is used. Therefore, the sulfide solid electrolyte produced by the method for producing a sulfide solid electrolyte can be suitably used as the sulfide solid electrolyte for energy storage elements such as all-solid-state batteries.

Claims

1. The method includes wet-grinding a material to be ground, the material including a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): The solvent further contains a hydrocarbon solvent, A method for producing a sulfide solid electrolyte that satisfies the following formula (2), where a [g] is the mass of the solvent excluding the compound, b [g] is the mass of the compound, and c [g] is the mass of the sulfide solid electrolyte material. R １ -COO-R ２ ・・・(1) 0.10≦b / (a+b+c)≦0.70...(2) In formula (1), R １ R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. ２ is a monovalent hydrocarbon group having 2 to 10 carbon atoms.

2. The method includes wet-grinding a material to be ground, the material including a sulfide solid electrolyte material and a solvent containing a compound represented by the following formula (1): The solvent further contains a hydrocarbon solvent, A method for pulverizing a sulfide solid electrolyte material, wherein the mass of the solvent excluding the compound is a [g], the mass of the compound is b [g], and the mass of the sulfide solid electrolyte material is c [g], satisfies the following formula (2): R １ -COO-R ２ ・・・(1) 0.10≦b / (a+b+c)≦0.70...(2) In formula (1), R １ R is a monovalent hydrocarbon group having 1 to 10 carbon atoms. ２ is a monovalent hydrocarbon group having 2 to 10 carbon atoms.

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