Crushing method of sulfur compound, crushing method of solid electrolyte, production method of solid electrolyte, and solid electrolyte

Abstract

Provided is a crushing method for crushing a sulfur compound, the method satisfying the relationship represented by formula (1) below: D2 / D1<0.49 (1) (In the formula, D1 represents the median diameter of a non-crushed sulfur compound, when the crushing method has only one crushing step. D1 represents the median diameter of a sulfur compound before performing the crushing step in any crushing step, when the crushing method has two or more crushing steps. D2 represents the median diameter of a sulfur compound after crushing, when the crushing method has only one crushing step. D2 represents the median diameter of a sulfur compound after performing the crushing step in the any crushing step, when the crushing method has two or more crushing steps.).

Description

Method for crushing sulfur compounds, method for crushing solid electrolytes, method for manufacturing solid electrolytes, and solid electrolytes

[0001] The present invention relates to a method for pulverizing a sulfur compound, a method for pulverizing a solid electrolyte, a method for producing a solid electrolyte, and a solid electrolyte.

[0002] Currently, most lithium-ion secondary batteries use electrolytes containing flammable organic solvents. In contrast, solid-state batteries, which use solid electrolytes instead of electrolytes and do not contain flammable organic solvents, are expected to be put to practical use as batteries that combine safety and high energy density.

[0003] In order to realize solid-state batteries, the development of solid electrolytes has been actively pursued. Solid electrolytes generally have lower ionic conductivity than organic electrolyte solutions, making their practical use difficult. Solid electrolytes can be obtained by mixing and firing predetermined raw materials to obtain a crystalline solid electrolyte raw material powder, which is then pulverized using a bead mill or the like (Patent Documents 1 to 3).

[0004] JP 2009-211950 A JP 2010-140893 A JP 2008-004459 A

[0005] However, when a solid electrolyte is pulverized by a conventional pulverization method, the ionic conductivity decreases compared to before pulverization, and there is a problem that the properties as a solid-state battery cannot be fully exhibited.

[0006] Therefore, an object of the present invention is to provide a solid electrolyte powder having excellent ionic conductivity.

[0007] As a result of extensive research to solve the above problems, the inventors have devised a pulverization method and found that the desired solid electrolyte powder can be obtained by pulverizing the solid electrolyte so that the particle size before and after pulverization satisfies a predetermined relationship.

[0008] That is, the present invention provides a method for pulverizing a sulfur compound, which satisfies the relationship shown in the following formula (1): D2 / D1<0.49 (1) (In the formula, D1 represents the median diameter of the unpulverized sulfur compound when the pulverization method includes only one pulverization step, and represents the median diameter of the sulfur compound before any pulverization step when the pulverization method includes two or more pulverization steps. D2 represents the median diameter of the sulfur compound after pulverization when the pulverization method includes only one pulverization step, and represents the median diameter of the sulfur compound after any pulverization step when the pulverization method includes two or more pulverization steps.)

[0009] The present invention also provides a method for pulverizing a sulfur compound, which satisfies the relationship shown in the following formula (2): A / B<3.6×10 －３ (2) (In the formula, A (S / cm) represents the difference between the ionic conductivity (S / cm) of the sulfur compound after a single pulverization step and the ionic conductivity (S / cm) of the unpulverized sulfur compound when the pulverization method includes only one pulverization step. Furthermore, when the pulverization method includes two or more pulverization steps, A represents the difference between the ionic conductivity of the sulfur compound before an optional pulverization step and the ionic conductivity of the sulfur compound after the optional pulverization step. B (μm) represents the difference between the median diameter (μm) of the unpulverized sulfur compound after the pulverization step when the pulverization method includes only one pulverization step. Furthermore, when the pulverization method includes two or more pulverization steps, B represents the difference between the median diameter (μm) of the sulfur compound before the optional pulverization step and the median diameter (μm) of the sulfur compound after the optional pulverization step.)

[0010] The present invention further provides a method for pulverizing a solid electrolyte, comprising: a preparation step of preparing a solid electrolyte; and a pulverization step of pulverizing the solid electrolyte, wherein the pulverization step satisfies the relationship shown in the following formula (3): D4 / D3<0.49 (3) (In the formula, D3 represents the median diameter of the unpulverized solid electrolyte when the pulverization step is performed only once. In addition, when the pulverization step is performed twice or more, D4 ​​represents the median diameter of the solid electrolyte before the pulverization step in any of the pulverization steps. In addition, when the pulverization step is performed twice or more, D4 ​​represents the median diameter of the solid electrolyte after the pulverization step in any of the pulverization steps.)

[0011] The present invention also provides a method for pulverizing a solid electrolyte, comprising: a preparation step of preparing a solid electrolyte; and a pulverization step of pulverizing the solid electrolyte, wherein the pulverization step satisfies the relationship shown in the following formula (4): C / D<3.6×10 －３ (4) (In the formula, C (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once and the ionic conductivity (S / cm) of the unpulverized solid electrolyte when the pulverization step is performed twice or more times. Furthermore, in the formula, C (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte before any pulverization step and the ionic conductivity (S / cm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more times. D (μm) represents the difference between the median diameter (μm) of the unpulverized solid electrolyte and the median diameter (μm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once. Furthermore, in the formula, D (μm) represents the difference between the median diameter (μm) of the solid electrolyte before any pulverization step and the median diameter (μm) of the solid electrolyte after the pulverization step when the pulverization method includes two or more pulverization steps.)

[0012] Furthermore, the present invention provides a method for producing a solid electrolyte, which includes a step of pulverizing solid electrolyte base powder, wherein the pulverization step satisfies the relationship shown in the following formula (5): D6 / D5<0.49 (5) (In the formula, D5 represents the median diameter of the base powder when the pulverization step is performed only once, and represents the median diameter of the solid electrolyte before any pulverization step when the pulverization step is performed twice or more. D6 represents the median diameter of the solid electrolyte after the pulverization step when the pulverization step is performed only once, and represents the median diameter of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more.)

[0013] The present invention also provides a method for producing a solid electrolyte, which includes a step of pulverizing a solid electrolyte base powder, wherein the pulverization step satisfies the relationship shown in the following formula (6): E / F<3.6×10 －３ (6) (In the formula, E (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once and the ionic conductivity (S / cm) of the unpulverized solid electrolyte when the pulverization step is performed twice or more times. Furthermore, E represents the difference between the ionic conductivity (S / cm) of the solid electrolyte before any pulverization step and the ionic conductivity (S / cm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more times. F (μm) represents the difference between the median diameter (μm) of the unpulverized solid electrolyte after the pulverization step when the pulverization step is performed only once. Furthermore, F represents the difference between the median diameter (μm) of the solid electrolyte before any pulverization step and the median diameter (μm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more times.)

[0014] Furthermore, in the present invention, the specific surface area measured by the BET method is S1 (m ２ / g), and the specific surface area calculated from the particle size distribution is S2 (m ２ / g), the value of S1 to S2 is less than 4.5.

[0015] The present invention will be described below based on preferred embodiments. First, the solid electrolyte pulverization method of the present invention will be described. The pulverization method of the present invention comprises a preparation step of preparing a solid electrolyte and a pulverization step of pulverizing the solid electrolyte, and is characterized in that the pulverization step satisfies the relationship shown in the following formula (3): D4 / D3<0.49 (3) (In the formula, D3 represents the median diameter (μm) of the unpulverized solid electrolyte when the pulverization step is performed only once. Furthermore, when the pulverization step is performed twice or more times, it represents the median diameter (μm) of the solid electrolyte before performing the pulverization step in any of the pulverization steps. When the pulverization step is performed only once, D4 ​​represents the median diameter (μm) of the solid electrolyte after pulverization. When the pulverization step is performed twice or more times, it represents the median diameter (μm) of the solid electrolyte immediately after performing the pulverization step in any of the pulverization steps.)

[0016] The pulverization method of the present invention will be described below. First, a solid electrolyte is prepared. Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes. Among these, sulfide solid electrolytes, which are solid electrolytes containing sulfur (S), are preferred.

[0017] The sulfide solid electrolyte may be, for example, one containing lithium (Li) and sulfur (S) elements and having lithium ion conductivity, or one containing lithium (Li), phosphorus (P), and sulfur (S) elements and having lithium ion conductivity. The sulfide solid electrolyte may be any of a crystalline material, glass ceramics, and glass. The sulfide solid electrolyte may have an argyrodite-type crystal structure. Examples of the sulfide solid electrolyte include Li, ２ S-P ２ S ５ , Li ２ S-P ２ S ５ -LiX (X represents one or more halogen elements), Li ２ S-P ２ S ５ -P ２ O ５ , Li ２S-Li ３ P.O. ４ -P ２ S ５ , Li ３ P.S. ４ , Li ４ P ２ S ６ , Li １０ GeP ２ S １２ , Li ３．２５ Ge ０．２５ P ０．７５ S ４ , Li ７ P ３ S １１ , Li ３．２５ P ０．９５ S ４ , Li ａ P.S. ｂ X ｃ (X represents at least one halogen element, a represents a number of 3.0 or more and 6.0 or less, b represents a number of 3.5 or more and 4.8 or less, and c represents a number of 0.1 or more and 3.0 or less.) In addition to these, for example, the sulfide solid electrolytes described in WO 2013 / 099834 and WO 2015 / 001818 can be mentioned.

[0018] When a sulfide solid electrolyte is used as the solid electrolyte, it is preferable to use, as raw materials, a compound of a Li element source, a compound of a P element source, a S element source, and, if necessary, a compound of an X element source. As the Li element source compound, for example, lithium sulfide (Li ２ As a source compound of P element, for example, diphosphorus pentasulfide (P ２ S ５ ) can be used. When the Li element source compound and / or the P element source compound is a sulfide, the sulfide can be used as the S element source compound. As the X element source compound, for example, LiX can be used. The above raw materials are mixed so that the Li element, the P element, the S element, and, if necessary, the X element, are in a predetermined molar ratio.

[0019] The mixing is carried out using a jet mill, a ball mill, a rod mill, a vibrating ball mill, a planetary mill, a disc mill, or the like.

[0020] The raw material composition obtained by mixing is then fired, for example, in an inert gas atmosphere, such as a nitrogen atmosphere or an argon atmosphere. If the raw material composition is a sulfide, it may be fired in a hydrogen sulfide gas atmosphere.

[0021] The firing temperature is, for example, preferably 300°C or higher, more preferably 350°C or higher, and even more preferably 400°C or higher. On the other hand, the firing temperature is, for example, preferably 700°C or lower, more preferably 600°C or lower, and even more preferably 550°C or lower. The firing time is, for example, preferably 0.5 hours or higher, more preferably 2 hours or higher, and even more preferably 3 hours or higher. On the other hand, the firing time is, for example, preferably 20 hours or lower, more preferably 10 hours or lower, and even more preferably 5 hours or lower. By firing the raw material composition under the above conditions, a solid electrolyte with even higher ionic conductivity is more likely to be obtained.

[0022] Next, the fired product is crushed using a mortar and pestle, a ball mill, or the like to obtain a crushed product. Next, preferably, the crushed product is pre-crushed before being subjected to main crushing to obtain a solid electrolyte powder of a predetermined size (median diameter D3). However, if the median diameter of the crushed product and the median diameter of the solid electrolyte powder obtained by pre-crushing satisfy the following formula (3) and also satisfy the formula (4) described below, the pre-crushing may be used as the main crushing and the pre-crushing may be omitted. In this specification, the term "median diameter" refers to the volume cumulative particle diameter D at 50% cumulative volume as determined by a laser diffraction / scattering particle size distribution measurement method. ５０ This is what I mean.

[0023] Preliminary grinding can be performed by a wet method or a dry method. Various media mills can be used for preliminary grinding. Examples of media mills that can be used include ball mills, bead mills, paint shakers, and homogenizers. Grinding media used in media mills include balls and beads made of various ceramics such as alumina and zirconia. The diameter of the grinding media can be, for example, 0.1 mm or more and 50 mm or less.

[0024] When wet grinding is performed, it is preferable to use an organic solvent as a dispersion medium, since this can suppress the generation of hydrogen sulfide gas caused by the reaction between the solid electrolyte and water. Examples of organic solvents include aromatic organic solvents such as toluene, xylene, benzene, and solvent naphtha, and aliphatic organic solvents such as heptane, decane, normal hexane, cyclohexane, and mineral spirits. These organic solvents can be used alone or in combination of two or more.

[0025] Next, the solid electrolyte powder having a median diameter D3 (μm) obtained by pre-pulverization is preferably wet-pulverized (main pulverization) to a median diameter D4 (μm). The pulverization must be carried out so as to satisfy the following formula (3): D4 / D3<0.49 (3). D4 / D3 preferably satisfies, for example, the relationship D4 / D3≦0.45, more preferably the relationship D4 / D3≦0.4, and even more preferably the relationship D4 / D3≦0.3. Meanwhile, D4 / D3 preferably satisfies, for example, the relationship 0.05≦D4 / D3, more preferably the relationship 0.1≦D4 / D3, and even more preferably the relationship 0.15≦D4 / D3. This makes it possible to provide a solid electrolyte powder with excellent ionic conductivity.

[0026] The grinding process in this grinding can be performed multiple times by changing the diameter of the grinding media, etc., so as to satisfy the above-mentioned grinding conditions and the grinding conditions described below. Therefore, D3 represents the median diameter of the unground solid electrolyte when the grinding step is performed only once. Furthermore, when the grinding step is performed twice or more, it represents the median diameter of the solid electrolyte before the grinding step in any of the grinding steps. D4 represents the median diameter of the solid electrolyte immediately after grinding when the grinding step is performed only once. When the grinding step is performed twice or more, it represents the median diameter of the solid electrolyte immediately after the grinding step in any of the grinding steps.

[0027] When the grinding time is t (minutes) and the weight of the solid electrolyte powder is m (g), the value t / m of the grinding time t (minutes) relative to the weight m (g) is preferably greater than 0. On the other hand, t / m is preferably less than 2.3, more preferably 1.5 or less, and even more preferably 0.7 or less. This makes it possible to provide a solid electrolyte powder with superior ionic conductivity.

[0028] The main pulverization may be carried out so as to satisfy the relationship shown in the following formula (4): C / D<3.6×10 －３ (4) (In the formula, C (S / cm) is the ionic conductivity σ of the solid electrolyte immediately after the pulverization step when the pulverization step is performed only once.) Ｃ１ (S / cm) and the ionic conductivity σ of the unground solid electrolyte Ｃ２ (S / cm) and the difference (σ Ｃ１ -σ Ｃ２ In addition, when the pulverization step is performed twice or more, the ionic conductivity σ of the solid electrolyte before any pulverization step is Ｃ３ (S / cm) and the ionic conductivity σ of the solid electrolyte immediately after the optional grinding process Ｃ４ (S / cm) and the difference (σ Ｃ３ -σ Ｃ４ ) D (μm) represents the median diameter d of the unpulverized solid electrolyte when the pulverization step is performed only once. Ｄ１ (μm) and the median diameter d of the solid electrolyte immediately after the pulverization process Ｄ２ (μm) and the difference (d Ｄ１ -d Ｄ２ In addition, when the pulverization step is performed two or more times, the median diameter d of the solid electrolyte before any pulverization step is Ｄ３ (μm) and the median diameter d of the solid electrolyte immediately after the optional pulverization step Ｄ４ (μm) and the difference (d Ｄ３ -d Ｄ４ ) In this specification, when "ionic conductivity" is mentioned, the ionic conductivity refers to a value measured at 25°C.

[0029] Equation (3) defines the conditions for the main pulverization of the solid electrolyte by focusing on the median diameter, which is a direct pulverization condition, whereas Equation (4) defines the conditions for the main pulverization of the solid electrolyte by focusing on not only the median diameter but also the ionic conductivity, which is a target physical property.

[0030] It is preferable that C / D in the formula (4) satisfies the relationship of, for example, 0≦C / D. On the other hand, C / D may be, for example, C / D≦3.0×10 －３ It is more preferable that the following relationship is satisfied: C / D≦2.5×10 －３ It is more preferable that the following relationship be satisfied: This makes it possible to provide a solid electrolyte powder with even better ion conductivity.

[0031] The reason why the ionic conductivity of the solid electrolyte powder is improved by adopting the above-described grinding conditions, i.e., formulas (3) and (4), is that the solid electrolyte powder is refined, increasing the contact area between the solid electrolyte powder particles, improving the ionic volume conductivity, and reducing the proportion of fine powder that does not contribute to the volume conductivity, thereby suppressing an increase in the interface of the solid electrolyte powder, which is a cause of a decrease in ionic conductivity.

[0032] From this viewpoint, the pulverization is preferably carried out at 25°C or lower, more preferably 15°C or lower, and even more preferably 5°C or lower. On the other hand, the pulverization is preferably carried out at -15°C or higher, and more preferably -10°C or higher. This suppresses aggregation of the solid electrolyte powder, refines the solid electrolyte powder, and further improves the ionic conductivity due to an increase in volume conductivity, and suppresses an increase in the interface of the solid electrolyte powder, which is a cause of a decrease in ionic conductivity. The above temperature is the temperature of the refrigerant circulating in the jacket portion of the pulverizer.

[0033] The diameter of the grinding media used in the grinding process is preferably, for example, 0.1 mm or more, while the diameter of the grinding media is preferably, for example, 50 mm or less, more preferably 10 mm or less, and even more preferably 1.0 mm or less.

[0034] When the pulverization is performed by wet pulverization, an organic solvent and a solid electrolyte powder are mixed to form a slurry, and this slurry is subjected to wet pulverization. The concentration of the solid electrolyte powder contained in the slurry is preferably set to, for example, 5% by mass or more and 50% by mass or less, in order to successfully obtain a solid electrolyte powder with high lithium ion conductivity. In wet pulverization using a media mill, the ratio of the grinding media to the slurry is preferably, for example, 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the slurry, in order to easily obtain a solid electrolyte powder that constitutes a solid electrolyte with high lithium ion conductivity. The dispersion time using the media mill is generally set to 0.1 hours or more and 60 hours or less, particularly 0.5 hours or more and 60 hours or less, in order to easily obtain a solid electrolyte powder with high lithium ion conductivity.

[0035] The solid electrolyte obtained after pulverization (hereinafter sometimes referred to as "solid electrolyte powder") has a specific surface area S1 (m ２ / g), and the specific surface area calculated from the particle size distribution is S2 (m ２ / g), the ratio S1 / S2 is less than 4.5. The ratio S1 / S2 is, for example, preferably 4.2 or less, more preferably 3.9 or less, and even more preferably 3.5 or less. On the other hand, the ratio S1 / S2 may be, for example, greater than 0, 0.5 or more, or 1.0 or more. The specific surface area S1 measured by the BET method is a physical quantity indicating the total surface area including the main body of the solid electrolyte powder and fine powder that does not contribute to ionic conductivity. In contrast, the specific surface area calculated from the particle size distribution is a physical quantity indicating the specific surface area of ​​the solid electrolyte powder excluding the fine powder. Therefore, a small value of S1 / S2 means that the proportion of fine powder that does not contribute to ionic conductivity is small. Therefore, it can be understood that the solid electrolyte powder obtained by the above-mentioned pulverization method has a dominant volume conductivity and exhibits high ionic conductivity, based on its physical properties.

[0036] The solid electrolyte powder is measured by a laser diffraction scattering particle size distribution measurement method, and the volume cumulative particle size D ９０is, for example, preferably less than 40 μm, more preferably 30 μm or less, even more preferably less than 5.9 μm, even more preferably 5.0 μm or less, and even more preferably 4.0 μm or less. ９０ When the solid electrolyte powder has such a particle size, the particles of the solid electrolyte powder are in close contact with each other, and the volume conductivity becomes dominant, making it possible to provide a solid electrolyte with high ionic conductivity.

[0037] Median diameter D of solid electrolyte powder ５０ The ratio of ionic conductivity (S / cm) to surface roughness (μm) is, for example, 1.3 × 10 －３ Preferably, it is greater than 2.0×10 －３ More preferably, it is 2.5×10 or more. －３ More preferably, it is 3.0 x 10 or more. －３ On the other hand, the median diameter D ５０ The ratio of ionic conductivity (S / cm) to area (μm) is preferably, for example, 1.0 or less, and more preferably 0.1 or less. When the solid electrolyte powder satisfies this relationship, high ionic conductivity is exhibited.

[0038] Median diameter D of solid electrolyte powder ５０ The ratio of the crystallite size (Å) of the solid electrolyte to the median diameter (μm) of the solid electrolyte powder is, for example, preferably 325 or more, more preferably 330 or more, even more preferably 400 or more, and even more preferably 750 or more. ５０ The ratio of the crystallite size (Å) of the solid electrolyte to the surface area (μm) may be, for example, 1200 or less, or may be 900 or less. When the crystallite size of the solid electrolyte is large, the interfaces between the crystal grains are reduced, which further increases the volume conductivity and makes it possible to provide a solid electrolyte powder with high ionic conductivity.

[0039] The solid electrolyte powder of the present invention thus obtained can be used, for example, as a material for forming a solid electrolyte layer or as a material contained in an electrode mixture containing an active material. Specifically, it can be used as a positive electrode mixture for forming a positive electrode layer containing a positive electrode active material, or as a negative electrode mixture for forming a negative electrode layer containing a negative electrode active material. Therefore, the solid electrolyte powder of the present invention can be used in batteries having a solid electrolyte layer, so-called solid-state batteries. More specifically, it can be used in lithium solid-state batteries. Lithium solid-state batteries may be primary batteries or secondary batteries, but lithium secondary batteries are particularly preferred. The term "solid-state battery" includes not only solid-state batteries that do not contain any liquid or gel-like substance as an electrolyte, but also embodiments that contain, for example, 50% by mass or less, 30% by mass or less, or 10% by mass or less of a liquid or gel-like substance as an electrolyte.

[0040] The solid electrolyte layer in a solid-state battery can be produced, for example, by dropping a slurry containing the solid electrolyte powder of the present invention, a binder, and a solvent onto a substrate and scraping it off with a doctor blade or the like, by contacting the substrate with the slurry and then cutting it with an air knife, or by forming a coating film by screen printing or the like and then removing the solvent by heating and drying. Alternatively, the solid electrolyte layer can be produced by press-molding the solid electrolyte powder of the present invention and then appropriately processing it. In addition to the solid electrolyte powder of the present invention, the solid electrolyte layer may contain other solid electrolyte powders. The thickness of the solid electrolyte layer in the present invention is typically preferably 5 μm or more and 300 μm or less, and more preferably 10 μm or more and 100 μm or less.

[0041] From the viewpoint of enhancing lithium ion conductivity, the solid electrolyte layer containing the solid electrolyte powder of the present invention preferably has a porosity of, for example, 50% or less, more preferably 30% or less, and even more preferably 20% or less. The porosity of the solid electrolyte layer can be adjusted, for example, by the pressing pressure when the solid electrolyte powder of the present invention is compacted. The pressing pressure is preferably, for example, 20 MPa or more.

[0042] The porosity can be calculated from the true density and apparent density of the solid electrolyte layer, which are determined by, for example, a liquid phase method (Archimedes method), using the following relational formula: Porosity (%) = (true density - apparent density) / true density x 100

[0043] The solid-state battery preferably has a positive electrode layer, a negative electrode layer, and a solid electrolyte layer between the positive electrode layer and the negative electrode layer, and the solid electrolyte layer contains the solid electrolyte of the present invention. Examples of the shape of the solid-state battery include a laminate type, a cylindrical type, and a prismatic type.

[0044] The cathode mixture in the solid-state battery containing the solid electrolyte powder of the present invention contains a cathode active material. As the cathode active material, for example, a material used as a cathode active material in a lithium secondary battery can be appropriately used. Examples of the cathode active material include spinel-type lithium transition metal compounds and lithium metal oxides having a layered structure. In addition to the cathode active material, the cathode mixture may also contain other materials, such as a conductive additive.

[0045] The negative electrode mixture in the solid-state battery containing the solid electrolyte powder of the present invention contains a negative electrode active material. For example, a negative electrode mixture used as a negative electrode active material in lithium secondary batteries can be used as appropriate. Examples of negative electrode active materials include lithium metal, carbon materials such as artificial graphite, natural graphite, and non-graphitizable carbon (hard carbon), lithium titanate, titanium-niobium composite oxide, silicon, silicon compounds, tin, and tin compounds. In addition to the negative electrode active material, the negative electrode mixture may also contain other materials, such as a conductive additive.

[0046] Although the above description has been given in terms of the concept of a method for crushing a solid electrolyte, the present invention can also be applied to a method for crushing a sulfur compound that is not specific to a solid electrolyte (i.e., whether or not it has ionic conductivity). The sulfur compound may be any compound containing sulfur (S), and preferably a compound containing at least one of lithium (Li), phosphorus (P), and a halogen (X). The X element may be at least one of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). When the present invention is applied to a method for crushing a sulfur compound, the formulas (3) and (4) are expressed by the following formulas (1) and (2):

[0047] D2 / D1<0.49 (1) (In the formula, D1 represents the median diameter (μm) of the unpulverized sulfur compound when the pulverization method includes only one pulverization step. When the pulverization method includes two or more pulverization steps, D1 represents the median diameter (μm) of the sulfur compound before the pulverization step in any of the pulverization steps. When the pulverization method includes only one pulverization step, D2 represents the median diameter (μm) of the sulfur compound immediately after pulverization. When the pulverization method includes two or more pulverization steps, D2 represents the median diameter (μm) of the sulfur compound immediately after the pulverization step in any of the pulverization steps.)

[0048] A / B<3.6×10 －３ (2) (wherein A (S / cm) is the ionic conductivity σ of the sulfur compound immediately after the pulverization step when the pulverization method includes only one pulverization step) Ａ１ (S / cm) and the ionic conductivity σ of the unground sulfur compound Ａ２ (S / cm) and the difference (σ Ａ１ -σ Ａ２ In addition, when the pulverization method includes two or more pulverization steps, the ionic conductivity σ of the sulfur compound before any pulverization step is Ａ３ (S / cm) and the ionic conductivity σ of the sulfur compound immediately after the optional grinding step Ａ４ (S / cm) and the difference (σ Ａ３ -σ Ａ４B represents the median diameter d of the unpulverized sulfur compound when the pulverization method includes only one pulverization step. Ｂ１ (μm) and the median diameter d of the sulfur compound immediately after the pulverization process Ｂ２ (μm) and the difference (d Ｂ１ -d Ｂ２ In addition, when the pulverization method includes two or more pulverization steps, the median diameter d of the sulfur compound before any one of the pulverization steps is Ｂ３ (μm) and the median diameter d of the sulfur compound immediately after the optional pulverization step Ｂ４ (μm) and the difference (d Ｂ３ -d Ｂ４ ) represents.

[0049] In addition, the present invention can also apply the above-described solid electrolyte pulverization method to a method for producing a solid electrolyte. The method for producing a solid electrolyte includes the steps of producing solid electrolyte base powder using predetermined raw materials and pulverizing the solid electrolyte base powder. In this production method, the formulas (3) and (4) in the above-described method for pulverizing a solid electrolyte are expressed by the following formulas (5) and (6): D6 / D5<0.49 (5) (In the formula, D5 represents the median diameter (μm) of the base powder when the pulverization is performed only once. Furthermore, when the pulverization step is performed twice or more, D6 represents the median diameter (μm) of the solid electrolyte before any pulverization step. When the pulverization step is performed only once, D6 represents the median diameter (μm) of the solid electrolyte immediately after pulverization. When the pulverization step is performed twice or more, D6 represents the median diameter (μm) of the solid electrolyte immediately after pulverization.)

[0050] E / F<3.6×10 －３ (6) (wherein E (S / cm) is the ionic conductivity σ of the solid electrolyte immediately after the pulverization step when the pulverization step is performed only once) Ｅ１ (S / cm) and the ionic conductivity σ of the unground solid electrolyte Ｅ２ (S / cm) and the difference (σ Ｅ１ -σ Ｅ２ In addition, when the pulverization step is performed twice or more, the ionic conductivity σ of the solid electrolyte before any pulverization step is Ｅ３(S / cm) and the ionic conductivity σ of the solid electrolyte immediately after the optional grinding process Ｅ４ (S / cm) and the difference (σ Ｅ３ -σ Ｅ４ F represents the median diameter d of the unpulverized solid electrolyte when the pulverization step is performed only once. Ｆ１ (μm) and the median diameter d of the solid electrolyte immediately after the pulverization process Ｆ２ (μm) and the difference (d Ｆ１ -d Ｆ２ In addition, when the pulverization method includes two or more pulverization steps, the median diameter d Ｆ３ (μm) and the median diameter d of the solid electrolyte immediately after the optional pulverization step Ｆ４ (μm) and the difference (d Ｆ３ -d Ｆ４ ) represents.

[0051] The sulfur compound preferably has lithium ion conductivity. In this specification, lithium ion conductivity refers to the ability to function as an electrolyte used in a lithium ion battery. The lithium ion conductivity of the sulfur compound is, for example, preferably 4.0 mS / cm or more at room temperature, i.e., 25°C, and more preferably 4.2 mS / cm or more, particularly preferably 5.0 mS / cm or more, and even more preferably 5.5 mS / cm or more, 6.0 mS / cm or more. The lithium ion conductivity can be measured using the method described in the Examples below.

[0052] The present invention includes the following embodiments. [1] A method for pulverizing a sulfur compound, the method satisfying the relationship shown in the following formula (1): D2 / D1<0.49 (1) (In the formula, D1 represents the median diameter of the unpulverized sulfur compound when the pulverization method includes only one pulverization step. When the pulverization method includes two or more pulverization steps, it represents the median diameter of the sulfur compound before the pulverization step in any of the pulverization steps. When the pulverization method includes only one pulverization step, D2 represents the median diameter of the sulfur compound after pulverization. When the pulverization method includes two or more pulverization steps, it represents the median diameter of the sulfur compound after the pulverization step in any of the pulverization steps.) [2] The method for pulverizing a sulfur compound according to [1], wherein, when the pulverization time of the sulfur compound is t (minutes) and the weight of the sulfur compound is m (g), the value of t (minutes) to m (g) is greater than 0 and less than 2.3. [3] A method for pulverizing a sulfur compound, the method satisfying the relationship shown in the following formula (2): A / B<3.6×10 －３(2) (In the formula, A (S / cm) represents the difference between the ionic conductivity (S / cm) of the sulfur compound after a pulverization step and the ionic conductivity (S / cm) of the unpulverized sulfur compound when the pulverization method includes only one pulverization step. Also, when the pulverization method includes two or more pulverization steps, A represents the difference between the ionic conductivity (S / cm) of the sulfur compound before an optional pulverization step and the ionic conductivity (S / cm) of the sulfur compound after the optional pulverization step. B (μm) represents the difference between the particle size (μm) of the unpulverized sulfur compound and the median diameter (μm) of the sulfur compound after the optional pulverization step when the pulverization method includes only one pulverization step. Also, when the pulverization method includes two or more pulverization steps, B represents the difference between the median diameter (μm) of the sulfur compound before the optional pulverization step and the median diameter (μm) of the sulfur compound after the optional pulverization step.) [4] The method for pulverizing a sulfur compound according to any one of [1] to [3], wherein the sulfur compound has lithium ion conductivity. [5] A method for pulverizing a solid electrolyte, comprising: a preparation step of preparing a solid electrolyte; and a pulverization step of pulverizing the solid electrolyte, wherein the pulverization step satisfies the relationship shown in the following formula (3): D4 / D3<0.49 (3) (In the formula, D3 represents the median diameter of the unpulverized solid electrolyte when the pulverization step is performed only once. Furthermore, when the pulverization step is performed twice or more, it represents the median diameter of the solid electrolyte before the pulverization step in any of the pulverization steps. D4 represents the median diameter of the pulverized solid electrolyte when the pulverization step is performed only once. When the pulverization step is performed twice or more, it represents the median diameter of the solid electrolyte after the pulverization step in any of the pulverization steps.) [6] The method for pulverizing a solid electrolyte according to [5], wherein, when the pulverization time of the solid electrolyte is t (minutes) and the weight of the solid electrolyte is m (g), the value of t (minutes) to m (g) is greater than 0 and less than 2.3. [7] A method for pulverizing a solid electrolyte, comprising: a preparation step of preparing a solid electrolyte; and a pulverization step of pulverizing the solid electrolyte, wherein the pulverization step satisfies the relationship shown in the following formula (4): C / D<3.6×10 －３(4) (In the formula, C (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once and the ionic conductivity (S / cm) of the unpulverized solid electrolyte when the pulverization step is performed twice or more times. Furthermore, in the formula, C (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte before any pulverization step and the ionic conductivity (S / cm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more times. D (μm) represents the difference between the median diameter (μm) of the unpulverized solid electrolyte after the pulverization step when the pulverization step is performed only once. Furthermore, in the formula, D (μm) represents the difference between the median diameter (μm) of the solid electrolyte before any pulverization step and the median diameter (μm) of the solid electrolyte after any pulverization step when the pulverization method includes two or more pulverization steps.) [8] The method for pulverizing a solid electrolyte according to any one of [5] to [7], wherein the preparation step includes a mixing step of mixing raw materials constituting the solid electrolyte to obtain a raw material mixture, and a firing step of firing the raw material mixture. [9] A method for producing a solid electrolyte, comprising a step of pulverizing a solid electrolyte base powder, wherein the pulverization step satisfies the relationship shown in the following formula (5). D6 / D5<0.49 (5) (In the formula, D5 represents the median diameter of the base powder when the pulverization step is performed only once. Furthermore, when the pulverization step is performed twice or more, it represents the median diameter of the solid electrolyte before any of the pulverization steps. D6 represents the median diameter of the solid electrolyte after the pulverization step when the pulverization step is performed only once. When the pulverization step is performed twice or more, it represents the median diameter of the solid electrolyte after any of the pulverization steps.)

[10] The method for producing a solid electrolyte according to [9], wherein, when the pulverization time in the pulverization step is t (minutes) and the weight of the solid electrolyte is m (g), the value of t (minutes) to m (g) is greater than 0 and less than 2.3.

[11] A method for producing a solid electrolyte, comprising a step of pulverizing solid electrolyte base powder, wherein the pulverization step satisfies the relationship shown in the following formula (6). E / F<3.6×10 －３(6) (In the formula, E (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once and the ionic conductivity (S / cm) of the unpulverized solid electrolyte when the pulverization step is performed twice or more. When the pulverization step is performed twice or more, E represents the difference between the ionic conductivity (S / cm) of the solid electrolyte before any pulverization step and the ionic conductivity (S / cm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more. F (μm) represents the difference between the median diameter (μm) of the unpulverized solid electrolyte and the median diameter (μm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once. When the pulverization step is performed twice or more, F represents the difference between the median diameter (μm) of the solid electrolyte before any pulverization step and the median diameter (μm) of the solid electrolyte after the pulverization step when the pulverization step is performed twice or more.)

[12] The specific surface area measured by the BET method is expressed as S1 (m ２ / g), and the specific surface area calculated from the particle size distribution and true density is S2 (m ２

[13] A solid electrolyte, wherein the value of S1 relative to S2 is less than 4.5 when the ratio of S1 to S2 is 1 / g. ９０

[14] The solid electrolyte according to

[12] , wherein the volume cumulative particle size D at 50% by volume of the cumulative volume is determined by a laser diffraction / scattering particle size distribution measurement method. ５０ The conductivity (S / cm) for the thickness (μm) is 1.3 × 10 －３

[15] The solid electrolyte according to

[12] or

[13] , wherein the volume cumulative particle size D at 50% by volume of the cumulative volume is larger than ５０

[16] The solid electrolyte according to any one of

[12] to

[14] , wherein the value of the crystallite size (Å) to (μm) is 325 or more.

[16] The solid electrolyte according to any one of

[12] to

[15] , wherein the solid electrolyte contains lithium (Li), phosphorus (P), and sulfur (S).

[0053] (Example 1) Li ５．４ P.S. ４．４ Cl ０．８ Br ０．８ Li ２ S powder and P ２ S ５Lithium powder, LiCl powder, and LiBr powder were weighed. These powders were pulverized and mixed using a ball mill to obtain a mixed powder. The mixed powder was fired to obtain a fired product consisting of a lithium ion conductive sulfide. The firing was carried out using a tubular electric furnace. During the firing, 100% pure hydrogen sulfide gas was circulated through the electric furnace at 3.0 L / min. The firing temperature was set to 490°C, and firing was carried out for 4 hours. As a result of XRD measurement, it was confirmed that this fired product had a crystalline phase with an argyrodite-type crystal structure.

[0054] The fired material is pre-pulverized by a conventional method to obtain a median diameter D ５０ After obtaining a solid electrolyte having a particle size of approximately 3 μm, the pulverized material was mixed with an organic solvent to form a slurry with a concentration of 15% by mass. This slurry was subjected to wet pulverization (main pulverization) in a bead mill (Ashizawa Finetech Co., Ltd.'s "Fast Mill"). The beads used in the bead mill were made of alumina with a diameter of 0.2 mm, and a 0°C refrigerant was passed through the jacket of the bead mill. Toluene was used as the organic solvent. 31 parts by mass of beads were used per 100 parts by mass of the slurry, and wet pulverization was performed for 10 minutes. At this time, the ratio D2 / D1 of the median diameter D1 of the solid electrolyte powder after pre-pulverization to the median diameter D2 of the solid electrolyte powder after main pulverization was 0.27, and the pulverization time per gram (t / m) was 0.67 min / g.

[0055] After wet grinding, the slurry was subjected to solid-liquid separation, and the solid content was dried. The dried fired product was sieved through a sieve with a mesh size of 53 μm to obtain the desired solid electrolyte powder. Other conditions, such as energy, were appropriately selected according to the desired solid electrolyte powder.

[0056] Other properties are shown in Table 1.

[0057] Median diameter D of solid electrolyte powder ５０ and particle size D ９０ The specific surface area, crystallite size, ionic conductivity and particle size change were measured under the following conditions.

[0058] <Median diameter D ５０ and D ９０Using an automatic sample feeder for laser diffraction particle size distribution measurement equipment (Microtrac SDC manufactured by Microtrac Bell Co., Ltd.), the sample (powder) was put into an organic solvent, and after irradiating it with 30W ultrasonic waves for 60 seconds at a flow rate of 50%, the particle size distribution was measured using a laser diffraction particle size distribution measurement equipment (MT3000II manufactured by Microtrac Bell Co., Ltd.), and the D was determined from the obtained volume-based particle size distribution chart. ５０ and D ９０ was measured. Toluene was used as the organic solvent. The particle size distribution of the solid electrolyte was measured by the laser diffraction scattering particle size distribution measurement method according to the following procedure. Using an automatic sample feeder for a laser diffraction particle size distribution measurement device (Microtrac SDC manufactured by Microtrac Bell Corporation), the flow rate of the measurement sample containing the solid electrolyte was set to 50%, and the measurement sample containing the solid electrolyte was irradiated with 30 W ultrasonic waves for 60 seconds. Thereafter, the particle size distribution was measured using a laser diffraction particle size distribution measurement device "MT3000II" manufactured by Microtrac Bell Corporation, and the particle sizes at which the cumulative volumes were 50% and 90% by volume were determined from the obtained volume-based particle size distribution chart, and the D ５０ and D ９０ In addition, D ５０ and D ９０ When measuring, the organic solvent was passed through a 60 μm filter, the solvent refractive index was 1.50, the particle permeability condition was "transmission", the particle refractive index was 1.59, the shape was "non-spherical", the measurement range was 0.133 μm to 704.0 μm, the measurement time was 10 seconds, and the measurement was performed twice, and the average of the obtained measurement values ​​was taken as D ５０ and D ９０ The measurement sample containing the solid electrolyte was prepared as follows. First, 0.3 g of the solid electrolyte and 5.7 g of a dispersant-containing liquid (mass of toluene: mass of dispersant (SN Dispersant 9228 manufactured by San Nopco Ltd.) = 19:1 (mass ratio)) were mixed by hand to prepare a slurry containing the solid electrolyte. Next, 6 ml of the slurry containing the solid electrolyte was poured into an organic solvent (toluene) to prepare a measurement sample containing the solid electrolyte. The D of the raw material powder of the solid electrolyte ５０ and D ９０The measurement was carried out in the same manner as described above, except that a measurement sample containing raw material powder was used. The measurement sample containing raw material powder was prepared as follows. First, as described below, a slurry containing raw material powder (raw material slurry) was prepared. Next, a few drops of a dispersant (SN Dispersant 9228 manufactured by San Nopco Ltd.) were added to an organic solvent (toluene), and then a few drops of the slurry containing raw material powder were added to prepare a measurement sample containing raw material powder.

[0059] <Specific Surface Area> [Measurement of BET Specific Surface Area] A sample (powder) was heated in a vacuum at 120°C for 1 hour using a pretreatment device "BELPREP-vacII" manufactured by Microtrac-Bell Corporation. Thereafter, using a specific surface area measuring device "BELSORP-miniII" manufactured by Microtrac-Bell Corporation, the specific surface area was calculated by the BET (Brunauer-Emmett-Teller) method from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K). The pretreatment was carried out at 120°C for 30 minutes or more in a reduced pressure environment. He was used as the purge gas and N was used as the adsorbate. ２ The specific surface area measured by the BET method was S1 (m ２ / g).

[0060] [Specific surface area calculated from particle size distribution and true density] (CS value) The CS value of a powder is the surface area per unit volume of the powder when the shape of the particles constituting the powder is assumed to be spherical, and is expressed in m ２ / cm ３ The CS value of a powder is calculated based on the volume-based particle size distribution of the powder measured by a laser diffraction / scattering particle size distribution measurement method using the following formula: CS value (m ２ / cm ３ ) = 6 / MA. MA is the area average particle size (μm), and is calculated from the following formula: MA (μm) = ΣVi / Σ(Vi / di) [where Vi is the frequency and di is the median value of the particle size division.]. The CS value is measured by D ５０ and D ９０In the same manner as in the measurement of , the particle size distribution was measured using a laser diffraction particle size distribution analyzer "MT3000II" manufactured by Microtrac-Bell Corporation, and the CS value was calculated from the obtained volume-based particle size distribution chart. (True Density) The true density was calculated by the gas substitution method using a true density evaluation device "BELPycno" manufactured by Microtrac-Bell Corporation. Pretreatment was carried out five times by purging. An alumina 10 cc cell was used for the measurement, and the sample was filled up to about 70% of the cell. The unit of the true density thus obtained is g / cm ３ <S2=X / Y> For a certain powder, the following formula: S2=X / Y [wherein X is the true density of the powder (g / cm ３ ), and Y is the CS value (m ２ / cm ３ ) is calculated based on the CS value (m ２ / cm ３ ) is the true density (g / cm ３ ) and the specific surface area S2 (m ２ / g).

[0061] <Crystallite size> Measurements were performed using a powder X-ray diffractometer "SmartLab SE" manufactured by Rigaku Corporation, without exposure to air. The measurement conditions were as follows: Tube voltage: 40 kV Tube current: 50 mA X-ray: Cu Kα radiation (CuKα1 radiation and CuKα2 radiation at a 2:1 intensity ratio) Optical system: Focused beam method Detector: One-dimensional detector Measurement range: 2θ = 10-120° Step width: 0.02° Scan speed: 1° / min. SRM660c (compound name: LaB6) manufactured by NIST (National Institute of Standards and Technology) was measured under the same conditions and used as a width standard, and SRM640f (compound name: Si) was measured under the same conditions and used as an angle standard. The analysis was performed using Rigaku Corporation's SmartLab Studio II. The analysis procedure was as follows. First, identification was performed. The CIF file (Crystalographic Information File) described below was read and the material was identified. The CIF file was obtained from the ICSD (Inorganic Crystal Structure Database). The ICSD Collection Code 418488 was used to analyze the sulfide solid electrolyte. Next, Rietveld analysis was performed using WPPF. For width correction, a width standard data file was selected. This file corresponds to a file in which the XRD data measured on SRM660c was identified with LaB6, analyzed in the same manner as described below, and saved. Furthermore, for angle correction, an angle standard data file was selected. This file corresponds to a file in which the XRD data measured on SRM640f was identified with Si, analyzed in the same manner as described below, and saved. The peak angles and widths were corrected using external standard samples. The "split pseudo-Voigt function" was used as the peak shape model function. Next, from the "Basic" tab, "Refinition Parameter Settings" - "Method" was selected to select "Rietveld / dl Pattern." Next, refinement was performed. During refinement, various parameters were adjusted until sufficient convergence was achieved. For example, an S value of 1.5 or less is a good guideline. The analyzed crystallite size was obtained from "Display" - "Analysis Results."

[0062] <Ionic Conductivity> The solid electrolyte powders obtained in the examples and comparative examples were subjected to a measurement of approximately 6 t / cm in a glove box filled with sufficiently dried Ar gas (dew point -60°C or lower). ２ The pellets were uniaxially pressed under a load of 1000 kJ / cm2 to prepare samples for measuring lithium ion conductivity. The lithium ion conductivity was measured using a Solartron 1255B electrochemical measurement system (1280C) and an impedance / gain-phase analyzer (SI 1260) manufactured by Solartron Analytical. The measurement conditions were an AC impedance method at a temperature of 25°C, a frequency of 100 Hz to 1 MHz, and an amplitude of 100 mV.

[0063] <Particle size change> When the pulverization step is performed only once, the particle size d of the unpulverized sulfur compound Ｂ１ (μm) and the particle size d of the sulfur compound after the pulverization process Ｂ２ (μm) and the difference (d Ｂ１ -d Ｂ２ In addition, when the pulverization method includes two or more pulverization steps, the particle diameter d of the sulfur compound before any of the pulverization steps was calculated. Ｂ３ (μm) and the particle size d of the sulfur compound immediately after the optional pulverization step Ｂ４ (μm) and the difference (d Ｂ３ -d Ｂ４ ) (μm) was calculated.

[0064] (Example 2) A solid electrolyte powder was obtained in the same manner as in Example 1, except that the bead diameter was 0.5 mm, the grinding time for the main grinding was 35 minutes, the ratio D2 / D1 of the median diameter D1 of the solid electrolyte powder after preliminary grinding to the median diameter D2 of the solid electrolyte powder after main grinding was 0.37, and the grinding time per 1 g (t / m) was 2.3 min / g. The results are shown in Table 1.

[0065] Comparative Example 1 A solid electrolyte powder was obtained in the same manner as in Example 1, except that the bead diameter was 0.3 mm, the grinding time for main grinding was 35 minutes, a 10°C refrigerant was flowed through the jacket of the bead mill device, the ratio D2 / D1 of the median diameter D1 of the solid electrolyte powder after preliminary grinding to the median diameter D2 of the solid electrolyte powder after main grinding was 0.49, and the grinding time per 1 g (t / m) was 2.3 min / g. The results are shown in Table 1.

[0066]

[0067] According to the examples, the above-mentioned formulas (1) and (2), as well as formulas (3) and (4), are satisfied, so the ionic conductivity of the solid electrolyte obtained by pulverization (specifically, the volume cumulative particle diameter D ５０ The ionic conductivity (S / cm) value (ionic conductivity / D ５０ )) is 1.3 x 10 －３ On the other hand, in the comparative examples that do not satisfy the above-mentioned formulas (1) and (2), and further the formulas (3) and (4), the (ionic conductivity / D ５０ ) is 1.3 x 10 －３ It can be seen that this value is lower than that of the example.

[0068] According to the present invention, it is possible to provide a solid electrolyte powder that constitutes a solid electrolyte having excellent ion conductivity.

Claims

1. A method for pulverizing a sulfur compound, which satisfies the relationship shown in the following formula (1): D2 / D1<0.49 (1) (In the formula, D1 represents the median diameter of the unpulverized sulfur compound when the pulverization method includes only one pulverization step, or represents the median diameter of the sulfur compound before any pulverization step when the pulverization method includes two or more pulverization steps. D2 represents the median diameter of the sulfur compound after pulverization when the pulverization method includes only one pulverization step, or represents the median diameter of the sulfur compound after any pulverization step when the pulverization method includes two or more pulverization steps.) 2. A method for crushing a sulfur compound according to claim 1, wherein the value of t (minutes) relative to m (g) is greater than 0 and less than 2.3, where t (minutes) is the crushing time of the sulfur compound and m (g) is the weight of the sulfur compound.

3. A method for pulverizing a sulfur compound, which satisfies the relationship shown in the following formula (2): A / B<3.6×10 －３ (2) (In the formula, A (S / cm) represents the difference between the ionic conductivity (S / cm) of the sulfur compound after a single pulverization step and the ionic conductivity (S / cm) of the unpulverized sulfur compound when the pulverization method includes only one pulverization step. Furthermore, when the pulverization method includes two or more pulverization steps, A represents the difference between the ionic conductivity (S / cm) of the sulfur compound before any pulverization step and the ionic conductivity (S / cm) of the sulfur compound after the pulverization step. B (μm) represents the difference between the particle size (μm) of the unpulverized sulfur compound and the median diameter (μm) of the sulfur compound after the pulverization step when the pulverization method includes only one pulverization step. Furthermore, when the pulverization method includes two or more pulverization steps, B represents the difference between the median diameter (μm) of the sulfur compound before the pulverization step and the median diameter (μm) of the sulfur compound after the pulverization step.) 4. The method for crushing a sulfur compound according to any one of claims 1 to 3, wherein the sulfur compound has lithium ion conductivity.

5. A method for pulverizing a solid electrolyte, comprising: a preparation step of preparing a solid electrolyte; and a pulverization step of pulverizing the solid electrolyte, wherein the pulverization step satisfies the relationship shown in the following formula (3): D4 / D3<0.49 (3) (In the formula, D3 represents the median diameter of the unpulverized solid electrolyte when the pulverization step is performed only once. Furthermore, when the pulverization step is performed twice or more, it represents the median diameter of the solid electrolyte before the pulverization step in any of the pulverization steps. When the pulverization step is performed only once, D4 ​​represents the median diameter of the solid electrolyte after the pulverization step in any of the pulverization steps.) 6. The method for crushing a solid electrolyte according to claim 5, wherein, when the crushing time for the solid electrolyte is t (minutes) and the weight of the solid electrolyte is m (g), the value of t (minutes) relative to m (g) is greater than 0 and less than 2.

3.

7. A method for pulverizing a solid electrolyte, comprising: a preparation step of preparing a solid electrolyte; and a pulverization step of pulverizing the solid electrolyte, wherein the pulverization step satisfies the relationship shown in the following formula (4): C / D<3.6×10 －３ (4) (In the formula, C (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once and the ionic conductivity (S / cm) of the unpulverized solid electrolyte when the pulverization step is performed twice or more times. Furthermore, in the formula, C (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte before any pulverization step and the ionic conductivity (S / cm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more times. D (μm) represents the difference between the median diameter (μm) of the unpulverized solid electrolyte after the pulverization step when the pulverization step is performed only once. Furthermore, in the formula, D (μm) represents the difference between the median diameter (μm) of the solid electrolyte before any pulverization step and the median diameter (μm) of the solid electrolyte after any pulverization step when the pulverization method includes two or more pulverization steps.) 8. A method for crushing a solid electrolyte according to any one of claims 5 to 7, wherein the preparation step includes a mixing step of mixing raw materials constituting the solid electrolyte to obtain a raw material mixture, and a firing step of firing the raw material mixture.

9. A method for producing a solid electrolyte, comprising a step of pulverizing solid electrolyte base powder, wherein the pulverization step satisfies the relationship shown in the following formula (5): D6 / D5<0.49 (5) (In the formula, D5 represents the median diameter of the base powder when the pulverization step is performed only once, and represents the median diameter of the solid electrolyte before any pulverization step when the pulverization step is performed twice or more. D6 represents the median diameter of the solid electrolyte after the pulverization step when the pulverization step is performed only once, and represents the median diameter of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more.) 10. The method for producing a solid electrolyte according to claim 9, wherein, when the grinding time in the grinding step is t (minutes) and the weight of the solid electrolyte is m (g), the value of t (minutes) relative to m (g) is greater than 0 and less than 2.

3.

11. A method for producing a solid electrolyte, comprising a step of pulverizing a solid electrolyte base powder, wherein the pulverization step satisfies the relationship shown in the following formula (6): E / F<3.6×10 －３ (6) (In the formula, E (S / cm) represents the difference between the ionic conductivity (S / cm) of the solid electrolyte after the pulverization step when the pulverization step is performed only once and the ionic conductivity (S / cm) of the unpulverized solid electrolyte when the pulverization step is performed twice or more times. Furthermore, E represents the difference between the ionic conductivity (S / cm) of the solid electrolyte before any pulverization step and the ionic conductivity (S / cm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more times. F (μm) represents the difference between the median diameter (μm) of the unpulverized solid electrolyte after the pulverization step when the pulverization step is performed only once. Furthermore, F represents the difference between the median diameter (μm) of the solid electrolyte before any pulverization step and the median diameter (μm) of the solid electrolyte after any pulverization step when the pulverization step is performed twice or more times.) 12. The specific surface area measured by the BET method is S1 (m ２ / g), and the specific surface area calculated from the particle size distribution and true density is S2 (m ２ / g), the value of S1 to S2 is less than 4.

5.

13. Volume cumulative particle size D at 90% cumulative volume by laser diffraction scattering particle size distribution measurement method ９０ 13. The solid electrolyte of claim 12, wherein the average particle size is less than 40 μm.

14. Volume cumulative particle size D at 50% cumulative volume by laser diffraction scattering particle size distribution measurement method ５０ The ionic conductivity (S / cm) for the thickness (μm) is 1.3 × 10 －３ The solid electrolyte of claim 12 or 13, wherein the solid electrolyte has a molecular weight of 1000 or more.

15. Volume cumulative particle size D at 50% cumulative volume by laser diffraction scattering particle size distribution measurement method ５０ 14. The solid electrolyte according to claim 12 or 13, wherein the value of crystallite size (Å) to (μm) is 325 or more.

16. The solid electrolyte according to claim 12 or 13, wherein the solid electrolyte contains lithium (Li), phosphorus (P), and sulfur (S).