JP7575981B2 - Method for producing solid electrolyte - Google Patents

Description

The present invention relates to a method for producing a solid electrolyte.

With the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones in recent years, the development of batteries to be used as power sources for these devices is becoming increasingly important. Conventionally, batteries used for such purposes have used electrolytes containing flammable organic solvents, but by making the battery all-solid-state, flammable organic solvents are not used in the battery, safety devices can be simplified, and manufacturing costs and productivity are excellent. Therefore, all-solid-state batteries in which the electrolyte is replaced with a solid electrolyte layer are being developed.

This solid electrolyte is required to have high ionic conductivity and be chemically stable.
From the viewpoint of improving ionic conductivity, it has been known to use a compound having a cubic argyrodite-type crystal structure containing lithium atoms, phosphorus atoms, and sulfur atoms (Patent Document 1). However, since compounds having a cubic argyrodite-type crystal structure are highly reactive with moisture and oxygen, they have problems in industrial use, such as the need to handle them under an inert gas with an ultra-low dew point.

For this reason, it has been disclosed that the composition of a compound having a cubic argyrodite-type crystal structure has been investigated in order to improve its chemical stability (Patent Document 1). However, the method described in Patent Document 1 has a problem in that the water resistance is insufficient and hydrogen sulfide (H ₂ S) is generated when the compound comes into contact with even dry air, resulting in a decrease in ionic conductivity.
In order to improve this, it has been investigated to coat the solid electrolyte with a compound having a cubic argyrodite type crystal structure (Patent Document 2).

JP 2016-24874 A International Publication No. 2018/003333

As a result of the inventors' investigations, it was found that although coating with a compound having a cubic argyrodite-type crystal structure is effective from the viewpoint of water resistance, the method of grinding and mixing a powder having a cubic argyrodite-type crystal structure and _{a P2S5} powder as described in Patent Document 2 involves a reaction between solids, making it difficult to obtain a homogeneous solid electrolyte material.
In addition, since the powder is pulverized and mixed for a long period of time, the process requires a large amount of energy input, which is not preferable from the viewpoint of reducing greenhouse gas (GHG) emissions.
Furthermore, when forming a coating by grinding and mixing, the surface of the solid electrolyte may become amorphous due to the shear energy generated within the system. For this reason, a heating process is required as the next step. However, this heating process causes granulation during the crystallization process, so it was found that the manufacturing method needs to be improved.

An object of the present invention is to provide a method for producing a compound having a cubic argyrodite-type crystal structure in which granulation and generation of H ₂ S are suppressed and a decrease in ionic conductivity is suppressed.

As a result of intensive research aimed at solving the above problems, the present inventors have discovered the following and have completed the present invention.
1. A solid electrolyte produced according to an embodiment of the present invention described below (hereinafter, sometimes referred to as "the present embodiment") suppresses the generation of H ₂ S even when exposed to moisture or the like.
2. By carrying out the above treatment in the presence of at least one solvent selected from a non-polar solvent and an aprotic solvent, a subsequent heating step is not required, so that granulation does not occur and the particle size is kept small, and further, by carrying out the treatment in at least one solvent selected from a non-polar solvent and an aprotic solvent, a solid-liquid reaction occurs, so that a homogeneous solid electrolyte can be obtained.
3. Since the process is carried out in at least one solvent selected from non-polar solvents and aprotic solvents, no special production equipment is required and a solid electrolyte can be obtained without excessive energy input.

That is, the present invention provides the following [1] to [13].
[1] A process for mixing (A) a sulfide containing lithium atoms, phosphorus atoms, and sulfur atoms and having an argyrodite-type crystal structure and (B) phosphorus sulfide in the presence of at least one solvent selected from a nonpolar solvent and an aprotic solvent without using a grinder;
A drying step for removing the solvent;
The method for producing a solid electrolyte comprising the steps of:
The method for producing a solid electrolyte according to [1], wherein [2] is carried out in at least one solvent selected from a nonpolar solvent and an aprotic solvent.
[3] The method for producing a solid electrolyte according to [1] or [2], wherein the phosphorus sulfide (B) is diphosphorus pentasulfide.

[4] The method for producing a solid electrolyte according to any one of [1] to [3], wherein heating is carried out in the mixing step.
[5] The method for producing a solid electrolyte according to [4], wherein the heating in the mixing step is carried out at less than 100° C.
[6] The method for producing a solid electrolyte according to any one of [1] to [5], wherein the amount of phosphorus sulfide (B) added per 100.0 parts by mass of the sulfide (A) in the mixing step is 0.5 parts by mass or more and 30.0 parts by mass or less.

[7] The method for producing a solid electrolyte according to any one of [1] to [6], wherein the at least one solvent selected from the group consisting of nonpolar solvents and aprotic solvents is at least one selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons, and aromatic hydrocarbons.
[8] The method for producing a solid electrolyte according to any one of [1] to [7], wherein the at least one solvent selected from the group consisting of nonpolar solvents and aprotic solvents is toluene, xylene, or heptane.
[9] The method for producing a solid electrolyte according to any one of [1] to [8], wherein the sulfide (A) further contains a halogen atom.

[10] The method for producing a solid electrolyte according to [9], wherein the halogen atom is at least one selected from the group consisting of a chlorine atom and a bromine atom.
[11] The method for producing a solid electrolyte according to any one of [1] to [10], wherein (A) the sulfide and (B) the phosphorus sulfide are used without being pulverized.
[12] The method for producing a solid electrolyte according to any one of [1] to [11], in which heating to 200° C. or higher is not performed after the drying step.
[13] The method for producing a solid electrolyte according to any one of [1] to [12], which does not use a media-type grinder.

According to the present invention, it is possible to provide a method for producing a compound having a cubic argyrodite-type crystal structure which suppresses granulation and generation of H ₂ S and inhibits a decrease in ionic conductivity.

Conceptual diagram of the test equipment used in the exposure test (Exposure test equipment 1)

The present embodiment will be described below. Note that the embodiment described below is merely one embodiment of the method for producing a solid electrolyte of the present invention, and the present invention is not limited thereto.
In addition, in this specification, lithium means both lithium and lithium ions, and should be interpreted appropriately unless a technical contradiction occurs.
In this specification, the upper and lower limit values of the numerical ranges of "greater than or equal to", "less than or equal to", and "to" can be arbitrarily combined, and the numerical values in the examples can also be used as the upper and lower limit values. Furthermore, provisions that are considered to be preferable can be adopted arbitrarily. That is, one provision that is considered to be preferable can be adopted in combination with one or more other provisions that are considered to be preferable. It can be said that a combination of preferred things is more preferable.

[Method for producing solid electrolyte]
The present embodiment is a method for producing a solid electrolyte, comprising the steps of: mixing (A) a sulfide containing lithium atoms, phosphorus atoms, and sulfur atoms and having an argyrodite-type crystal structure (hereinafter also referred to as “(A) sulfide”) and (B) phosphorus sulfide in the presence of at least one solvent selected from a nonpolar solvent and an aprotic solvent, without using a pulverizer; drying the mixture to remove the solvent; and drying the mixture to remove the solvent.

In this specification, a solid electrolyte refers to an electrolyte that remains solid at 25°C under a nitrogen atmosphere. The solid electrolyte in this embodiment is a solid electrolyte that contains lithium, sulfur, phosphorus, and halogen elements and has ionic conductivity due to the lithium element.

This manufacturing method can convert the Li ₂ S remaining in the solid electrolyte, which is one of the causes of the generation of H ₂ S, into Li ₃ PS ₄ , etc., which is relatively stable to moisture, etc., so that it is possible to improve water resistance while suppressing a decrease in ionic conductivity, and it is believed that the generation of H ₂ S is suppressed.
In addition, since the production method is carried out in the presence of at least one solvent selected from nonpolar solvents and aprotic solvents, preferably in at least one solvent selected from nonpolar solvents and aprotic solvents, it is not a reaction between solid (A) sulfide and solid (B) phosphorus sulfide, but rather a reaction in which part or all of the phosphorus (B) sulfide is dissolved in the aprotic solvent. This is considered to allow the phosphorus (B) sulfide to easily penetrate not only the surface of (A) sulfide but also into the pores of (A) sulfide, enabling the reaction to take place without the use of a grinder.
It is believed that the compound produced by the reaction between (A) sulfide and (B) phosphorus sulfide is also formed on the surface of (A) sulfide and on the wall surfaces inside the pores, thereby making it possible to obtain a solid electrolyte having a cubic argyrodite-type crystal structure in which the decrease in ionic conductivity is suppressed, water resistance is improved, and generation of _H2S is suppressed.

Furthermore, in a solid-solid reaction, the reaction does not proceed unless the solids come into contact with each other, so it is difficult to obtain a homogeneous solid electrolyte, and it is difficult to obtain a homogeneous solid electrolyte even if the reaction time is extended. In contrast, in this embodiment, a solid-liquid reaction is performed, so a homogeneous solid electrolyte can be obtained in a short time.
In addition, by carrying out the production in at least one solvent selected from a nonpolar solvent and an aprotic solvent, amorphization of the solid electrolyte can be minimized, and therefore a heating step is not required after that step. This is preferable because granulation due to heating does not occur, the production can be carried out with simple production equipment, and the amount of energy input during production can be reduced.

<Solvent>
The solvent of the present embodiment is at least one solvent selected from a non-polar solvent and an aprotic solvent. The solvent of the present embodiment is preferably one that dissolves phosphorus sulfide (B), which is the raw material of the present embodiment, from the viewpoint of homogeneously and easily producing a solid electrolyte, and it is preferable to use only one solvent from the viewpoint of ease of handling without requiring a mixing step, and it is also preferable to use two or more solvents in combination from the viewpoint of easily adjusting the solubility by appropriately selecting two or more solvents having different solubility.

The nonpolar solvent and aprotic solvent in this embodiment are solvents that do not have a proton (H ⁺ ) that is easily donated, and from the viewpoint of suppressing side reactions, a nonpolar solvent is preferable, and from the viewpoint of dissolving (B) phosphoric acid sulfide, inorganic salts, etc., an aprotic polar solvent is preferable.
The non-polar solvent of the present invention means a solvent having no polarity or low polarity, and is a solvent consisting of carbon atoms and hydrogen atoms. From the viewpoint of homogeneous and simple production of a solid electrolyte in terms of ease of availability and solubility, it is preferable that the non-polar solvent is a saturated hydrocarbon, an unsaturated hydrocarbon, or an aromatic hydrocarbon.

For the reasons mentioned above, the saturated hydrocarbon is preferably pentane, hexane, heptane, octane, 2-ethylhexane, decane, cyclohexane, methylcyclohexane, decalin, IP Solvent 1016 (manufactured by Idemitsu Kosan Co., Ltd.) or IP Solvent 1620 (manufactured by Idemitsu Kosan Co., Ltd.).
For the reasons mentioned above, the unsaturated hydrocarbon is preferably hexene, cyclohexene or heptene.
For the reasons mentioned above, the aromatic hydrocarbon is preferably benzene, toluene, xylene, ethylbenzene, tetrahydronaphthalene, IPZOL 100 (manufactured by Idemitsu Kosan Co., Ltd.) or IPZOL 150 (manufactured by Idemitsu Kosan Co., Ltd.).

Among the non-polar solvents, in terms of the solubility of the solute, boiling point, toxicity, and availability, hexane, heptane, cyclohexane, benzene, toluene, or xylene is more preferred, heptane, toluene, or xylene is even more preferred, and toluene is even more preferred.

The aprotic polar solvent of the embodiment is a solvent having a heteroatom, and from the viewpoint of dissolving (B) phosphoric acid sulfide, inorganic salts, etc., ether-based, ketone-based, ester-based, nitrile-based, amide-based, dioxolane-based, and sulfolane-based solvents are preferred.

This embodiment is carried out in the presence of at least one solvent selected from a nonpolar solvent and an aprotic solvent, and it is preferable that the mixing step of (A) the sulfide and (B) the phosphorus sulfide is carried out in at least one solvent selected from a nonpolar solvent and an aprotic solvent.
The mixing step being carried out in at least one solvent selected from a nonpolar solvent and an aprotic solvent preferably means that, at the initial stage of the mixing step, all of the phosphorus sulfide (B) is dissolved in the aprotic solvent or a portion of the phosphorus sulfide is dissolved therein, and the solid sulfide (A) is entirely present in the solvent.

In addition, in this embodiment, the mixing step of (A) sulfide and (B) phosphorus sulfide is carried out in the presence of at least one solvent selected from nonpolar solvents and aprotic solvents, so that excess (B) phosphorus sulfide and unnecessary compounds such as by-products can be removed, and a decrease in ionic conductivity can be suppressed, which is preferable.

In this embodiment, the amount of at least one solvent selected from nonpolar solvents and aprotic solvents is preferably 1 mL (milliliters, hereinafter, mL is used as milliliters) or more per 1 g of sulfide (A) from the viewpoint of obtaining a homogeneous solid electrolyte in which the decrease in ionic conductivity is suppressed, more preferably 5 mL or more, and even more preferably 8 mL or more, and is preferably 40 mL or less, more preferably 30 mL or less, and even more preferably 25 mL or less, since the production can be carried out with simple production equipment.

<(A) Sulfide>
The sulfide (A) used in this embodiment has an argyrodite-type crystal structure (JP 2011-096630 A, JP 2013-211171 A, etc.), such as Li ₆ PS ₅ X, Li _7-x PS _6-x X _x (X = Cl, Br, I, x = 0.0 to 1.8), but from the viewpoint of obtaining higher ionic conductivity, it is preferable that it has it as the main crystal. In this specification, "having it as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more.
Diffraction peaks of these argyrodite-based crystal structures appear, for example, at 2θ=15.3°, 17.7°, 31.1°, 44.9°, and 47.7°.

Further, the following argyrodite-based crystal structure is also included.
The crystal structure represented by the composition formula Li _{7 -x} P _1-y Si _y S ₆ and Li _7+x P _1-y Si _y S ₆ (x is −0.6 to 0.6, y is 0.1 to 0.6), which has the structural skeleton of Li 7 PS ₆ and in which a portion of P is replaced by Si, is a cubic or orthorhombic crystal, preferably a cubic crystal, and has peaks that appear mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0° in X-ray diffraction measurement using CuKα radiation.

The crystal structure represented by the above composition formula Li7 _{-x- 2yPS6-x-yClx (} 0.8≦x≦1.7, 0<y≦−0.25x+0.5) is preferably a cubic crystal, and has peaks appearing mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0° in X-ray diffraction measurement using CuKα radiation.
The crystal structure represented by the above composition formula Li7 _- xPS6 _{-xHax (} Ha is Cl or Br, and x is preferably 0.2 to 1.8) is preferably a cubic crystal, and has peaks appearing mainly at 2θ=15.5°, 18.0°, 25.0°, 30.0°, 31.4°, 45.3°, 47.0°, and 52.0° in X-ray diffraction measurement using CuKα radiation.
The positions of these peaks may vary within a range of ±0.5°.

From the viewpoint of obtaining a higher ionic conductivity, the sulfide (A) used in this embodiment is preferably one that does not contain crystalline Li ₃ PS ₄ (β-Li ₃ PS ₄ ). Whether or not it does not contain crystalline Li ₃ PS ₄ (β-Li ₃ PS ₄ ) can be confirmed by the presence or absence of diffraction peaks at 2θ = 17.5 ° and 26.1 ° seen in crystalline Li ₃ PS ₄ , and in this specification, it is considered not to contain crystalline Li ₃ PS ₄ (β-Li 3 PS 4 ) if it _does not have such diffraction peaks, or if it does have such diffraction peaks, if a peak that is extremely small compared to the diffraction peak of _the argyrodite type crystal structure is detected.

The shape of the sulfide (A) used in this embodiment is not particularly limited, but may be in accordance with the required shape of the solid electrolyte produced in this embodiment, and may be, for example, particulate. The average particle size ( _D50 ) of the particulate solid electrolyte is preferably 0.01 μm or more, more preferably 0.03 μm or more, more preferably 50 μm or less, even more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less, because the particle size of the solid electrolyte produced is the required particle size.

((A) Method for producing sulfide)
A preferred embodiment of the production of (A) the sulfide will be described below.
The (A) sulfide used in the present embodiment is obtained by mixing and grinding sulfide starting materials, such as lithium sulfide, phosphorus sulfide, and lithium halide, in a solvent, heating the resulting raw material mixture to form a calcined product, and firing the calcined product.
Alternatively, the raw material mixture is heated in a solvent to calcinate, and the resulting calcined product is fired to obtain the sulfide (A).

As the solvent, an organic solvent can be used, and preferably a non-polar solvent, a polar solvent, or a mixture of these. It is preferable to use a non-polar solvent or a solvent mainly composed of a non-polar solvent, for example, 95% by mass or more of the total organic solvent is a non-polar solvent.

The non-polar solvent is preferably a hydrocarbon solvent, and as the hydrocarbon solvent, a saturated hydrocarbon, an unsaturated hydrocarbon, or an aromatic hydrocarbon can be used.
Examples of saturated hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, decane, tridecane, cyclohexane, and decalin.
Examples of unsaturated hydrocarbons include hexene, heptene, and cyclohexene.
Examples of aromatic hydrocarbons include toluene, xylene, ethylbenzene, and 1,2,3,4-tetrahydronaphthalene.
Of these, toluene or xylene is preferred.

It is preferable that the hydrocarbon solvent is dehydrated in advance. Specifically, the water content is preferably 100 ppm by mass or less, and more preferably 30 ppm by mass or less.

In one embodiment, the organic solvent preferably contains at least one of a nitrile compound and an ether compound.
Examples of the ether compounds include tetrahydrofuran and diethyl ether.
The nitrile compound is preferably a nitrile compound represented by R(CN) _n , where R is an alkyl group having 1 to 10 carbon atoms or a group having an aromatic ring having 6 to 18 ring carbon atoms, and n is 1 or 2.

Examples of the nitrile include acetonitrile, propionitrile, 3-chloropropionitrile, benzonitrile, 4-fluorobenzonitrile, tertiary butyronitrile, isobutyronitrile, cyclohexylnitrile, capronitrile, isocapronitrile, malononitrile, and fumaronitrile. Preferred are propionitrile, isocapronitrile, and isobutyronitrile.
For example, nitrile compounds are preferred because they form an azeotrope with toluene and are therefore easily removed from the treated product together with toluene during drying.
The amount of the nitrile compound and the ether compound contained in the organic solvent is preferably from 0.01 to 5% by mass, more preferably from 0.1 to 3% by mass, and particularly preferably from 0.3 to 1% by mass.

For mixing and grinding, grinders such as planetary ball mills, vibration mills, tumbling mills, bead mills, and ball mills, and kneaders such as single-shaft kneaders and multi-shaft kneaders can be used.

The raw material mixture obtained by removing the solvent from the processed product after mixing and grinding is mainly composed of fine crystals. By mixing and grinding the raw materials, the raw materials are further atomized, and a raw material mixture consisting of fine crystals of each raw material is obtained.

The raw material mixture is calcined to obtain a calcined product. In one embodiment, the raw material mixture is obtained by removing the solvent as described above, and then calcined to obtain a powdered calcined product. The heating temperature and time in the calcination can be appropriately adjusted in consideration of the composition of the calcined product. For example, the heating temperature is preferably 150°C to 300°C, more preferably 160°C to 280°C, and particularly preferably 170°C to 250°C. The heating time is preferably 0.1 to 8 hours, more preferably 0.2 to 6 hours, and particularly preferably 0.25 to 4 hours.

There are no particular limitations on the heating device used in the calcination. Examples include shear-type dryers such as FM mixers and Nauta mixers, stationary furnaces such as hearth kilns, and rotary furnaces such as rotary kilns. Drying may be performed before calcination, or drying and calcination may be performed simultaneously. There are no particular limitations on the atmosphere in which the calcination is performed, but an inert gas atmosphere such as nitrogen or argon is preferred.

The calcined product is calcined to obtain the sulfide (A). The heating temperature and time in the calcination can be appropriately adjusted in consideration of the composition of the calcined product, etc. For example, in the case of an argyrodite-type solid electrolyte, the heating temperature is preferably 300°C to 470°C, more preferably more than 300°C to 460°C or less, even more preferably 320°C to 450°C, still more preferably 350°C to 440°C, and particularly preferably 380°C to 430°C.
The heating time is preferably from 1 to 360 minutes, more preferably from 5 to 120 minutes, and particularly preferably from 10 to 60 minutes.
The atmosphere during heating is not particularly limited, but is preferably not a hydrogen sulfide gas flow but an inert gas atmosphere such as nitrogen, argon, etc. In the firing step, a firing furnace such as a stationary hearth kiln or a rotary kiln can be used.

When the raw material mixture is calcined in a solvent, the above-mentioned non-polar solvent, polar solvent, or a mixture of these can be used as the solvent for calcination. Heat is applied to the slurry in which the raw material mixture is dispersed in the solvent. The solvent used for calcination may be the same as or different from the solvent used for mixing the raw materials. When the same solvent is used, it is preferable because a step of removing the solvent is not required.

The heating temperature and time in the calcination can be appropriately adjusted in consideration of the composition of the raw material. For example, the heating temperature is preferably 150°C to 300°C, more preferably 160°C to 280°C, further preferably 170°C to 270°C, and particularly preferably 180°C to 260°C. By setting the temperature within the above range, the _PS4 structure is formed, and halogen is easily incorporated into the crystal. As in the first embodiment, in this embodiment, the raw material mixture of fine crystals is calcined in a solution, so that it is possible to form crystals containing the _PS4 structure at a relatively low temperature.
The heating time is preferably from 10 minutes to 6 hours, more preferably from 10 minutes to 3 hours, and particularly preferably from 30 minutes to 2 hours.
There are no particular limitations on the heating device used in the calcination, but when the heating temperature exceeds the boiling point of the solvent used, it is preferable to use an autoclave.

The solvent is removed from the slurry used in the calcination to recover the calcined product. The method for removing the solvent is not particularly limited, but the solvent can be distilled off under normal pressure or reduced pressure. In order to further increase productivity, filtration can also be used in combination.
The calcined product is fired to obtain the sulfide (A).

<(B) Phosphorus Sulfide>
The phosphorus sulfide (B) of this embodiment can be the same as the phosphorus sulfides used as the raw material of the sulfide (A), such as lithium sulfide (Li ₂ S); diphosphorus trisulfide (P ₂ S ₃ ), diphosphorus pentasulfide (P ₂ S ₅ ), etc., but diphosphorus pentasulfide (P ₂ S ₅ ) is preferred because it provides a solid electrolyte in which the decrease in ionic conductivity is suppressed.

In this embodiment, since the process is carried out in the presence of at least one solvent selected from nonpolar solvents and aprotic solvents, the shape of the phosphorus sulfide (B) is not particularly limited. However, since the process can be carried out using simple production equipment, the average particle size ( _D50 ) is preferably 10 cm or less, more preferably 8 cm or less, and even more preferably 5 cm or less.
In this embodiment, since the reaction is carried out in the presence of at least one solvent selected from a nonpolar solvent and an aprotic solvent, it is preferable from the viewpoint of a simple production process to carry out the reaction without pulverizing the phosphorus sulfide (B).

(Amount of (A) Sulfide and (B) Phosphorus Sulfide Used)
The amount of the sulfide (A) used in this embodiment may be appropriately determined depending on the production equipment used.
The amount of phosphorus sulfide (B) used in this embodiment is preferably determined based on the amount of sulfide (A) and the amount of ^S2- contained in the sulfide (A). In order to obtain a homogeneous solid electrolyte in which a decrease in ion conductivity is suppressed, the amount is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 2.0 parts by mass or more, relative to 100.0 parts by mass of sulfide (A). In order to reduce the amount of unreacted phosphorus sulfide (B) remaining, the amount is preferably 30.0 parts by mass or less, more preferably 20.0 parts by mass or less, and even more preferably 15.0 parts by mass or less.

<Mixing step>
There is no particular limitation on the method for mixing (A) sulfide and (B) phosphorus sulfide in the presence of at least one solvent selected from nonpolar solvents and aprotic solvents in this embodiment, and the (A) sulfide and (B) phosphorus sulfide may be mixed in the presence of an aprotic solvent by introducing them into an apparatus capable of mixing (A) sulfide and (B) phosphorus sulfide in the presence of at least one solvent selected from nonpolar solvents and aprotic solvents.

In this embodiment, if a pulverizer exemplified as a pulverizer that can be used in the process in the sulfide manufacturing method (A) is used, a subsequent process such as crystallization will be required, and therefore it is necessary not to use a pulverizer. "Without using a pulverizer" literally means that a "pulverizer" is not used, and the "pulverizer" is a pulverizer exemplified as a pulverizer that can be used in the process in the sulfide manufacturing method (A).

In this embodiment, the device capable of mixing is, for example, a mechanical stirring mixer equipped with a stirring blade in a tank.
Although the mixer described below may also cause "pulverization," there is no problem in using the mixer since the main process is "mixing" and not "pulverization."
Examples of the mechanical stirring mixer include a high-speed stirring mixer and a double-arm mixer, and the high-speed stirring mixer is preferably used from the viewpoint of increasing the uniformity of the raw material in the mixture of the raw material content and the complexing agent, and obtaining a higher ion conductivity together with a predetermined average particle size and specific surface area. Also, examples of the high-speed stirring mixer include a vertical shaft rotary mixer and a horizontal shaft rotary mixer, and either type of mixer may be used.

The shapes of the impellers used in mechanically stirred mixers include blade type, arm type, ribbon type, multi-stage blade type, double arm type, shovel type, double-shaft blade type, flat blade type, C-shaped blade type, etc., and from the viewpoint of increasing the uniformity of the raw material in the raw material content and obtaining a higher ionic conductivity along with a specified average particle size and specific surface area, the shovel type, flat blade type, C-shaped blade type, etc. are preferred.

In addition, since this embodiment is carried out in the presence of at least one solvent selected from nonpolar solvents and aprotic solvents, it is preferable not to use a media-type grinding machine such as a ball mill as in Patent Document 2. This makes it possible to suppress the amorphization of (A) sulfide, and does not require a subsequent heating step to 200°C or higher for the purpose of converting it to an argyrodite-type crystal form, thereby suppressing granulation.

In this embodiment, the mixing process is not particularly limited, and may be performed without adjusting the temperature from the outside, such as by heating or cooling, but from the viewpoint of shortening the process time and obtaining a solid electrolyte with suppressed decrease in ionic conductivity, heating may be performed, and it is preferable to perform the process at less than 100°C, more preferably less than 90°C, and even more preferably less than 85°C. In order to maintain the solubility of the aprotic solvent, it is preferable to perform the process at -20°C or higher, more preferably 0°C or higher, and even more preferably to perform the process without heating.

In the method described in Patent Document 1, the mixed powder obtained by grinding and mixing in a ball mill is also heated at 200°C for 2 hours, but this is done to restore the crystal structure that has been destroyed by grinding and mixing to an argyrodite structure, and is different from heating to shorten the time of the mixing process as in this embodiment. For this reason, the temperature in Patent Document 1 is 200°C, which is high enough to cause a crystal transition to an argyrodite structure, and is significantly different from the less than 100°C used in this embodiment.

The time for performing the mixing step in this embodiment may be determined based on the consumption amount of phosphorus sulfide (B) and is not particularly limited. For example, the time is preferably 1 hour or more, more preferably 3 hours or more, and even more preferably 5 hours or more.
From the viewpoint of production efficiency, the reaction time is preferably 24 hours or less, more preferably 18 hours or less, even more preferably 12 hours or less, and even more preferably 10 hours or less.
From the viewpoint of suppressing a decrease in ion conductivity, the time is preferably 120 hours or less, more preferably 100 hours or less, and even more preferably 80 hours or less.

The mixing step of the present embodiment is preferably carried out in an inert gas atmosphere at a high dew point (eg, a dew point of −60 to −20° C.) at the dry room level.
The reaction may be carried out at atmospheric pressure, but when a compound having a low boiling point such as an aprotic solvent is used, it is also preferable to carry out the reaction under pressure in an autoclave or the like.

<Drying process>
In this embodiment, a drying step is further required after the step of mixing (A) the sulfide and (B) the phosphorus sulfide.
By carrying out a drying step to remove at least one solvent selected from the nonpolar solvent and the aprotic solvent used in this embodiment, impurities are reduced, and improvement in ionic conductivity can be expected. On the other hand, when the solid electrolyte is prone to forming aggregates by drying, it is preferable to appropriately adjust the drying temperature and drying time described later.

Drying may be performed without heating or with heating from the viewpoint of reducing drying time, and is preferably performed at 50° C. or higher, more preferably 70° C. or higher, and preferably 90° C. or higher. From the viewpoint of suppressing granulation and a decrease in ion conductivity, the temperature is preferably 150° C. or lower, more preferably 150° C. or lower, and even more preferably 120° C. or lower.
The drying time may be determined depending on the amount of the aprotic solvent remaining, and is not particularly limited, but is preferably 1 minute or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and even more preferably 1 hour or more. The upper limit of the drying time is not particularly limited, but is preferably 24 hours or less, more preferably 12 hours or less, even more preferably 6 hours or less, and even more preferably 3 hours or less.

The drying may be performed by filtering the precursor or mixture containing the solvent using a glass filter or the like, by solid-liquid separation using decantation, or by solid-liquid separation using a centrifuge, etc. In this embodiment, after the solid-liquid separation, drying may be performed under the above-mentioned temperature conditions.
Specifically, the solid-liquid separation can be easily carried out by decantation, in which the precursor or mixture accompanied with the solvent is transferred to a container, and the solvent that becomes the supernatant is removed after the precursor or mixture is precipitated, or by filtration using, for example, a glass filter having a pore size of about 10 to 200 μm, preferably 20 to 150 μm.
From the viewpoint of suppressing granulation of the solid electrolyte, it is preferable not to carry out heating after the drying step.

<Solid electrolyte>
The solid electrolyte of the present embodiment has a composition in which the content of Li ₂ S and the like is reduced relative to the content of the sulfide (A), and the content of a compound in which a component of the sulfide (A) reacts with phosphorus sulfide (B) is increased depending on the amount of phosphorus sulfide (B) used.
The crystal structure of the solid electrolyte of this embodiment has the above-mentioned argyrodite-type crystal structure, but from the viewpoint of obtaining higher ionic conductivity, it is preferable that the crystal structure has the argyrodite-type crystal structure as the main crystal. In this specification, "having the argyrodite-type crystal structure as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more.

The surface layer of the solid electrolyte, in which a larger amount of the compound in which (A) the sulfide component reacts with (B) phosphorus sulfide is present, may be an amorphous solid electrolyte. The presence of this amorphous solid electrolyte is preferable because it makes it easier for the solid electrolytes to be thermally fused together by pressure bonding or the like when manufacturing an all-solid-state battery.

The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.
1. Measurement method 1-1. (A) Crystal structure of sulfide and solid electrolyte A sample powder was cut into a groove 20 mm in diameter and 0.2 mm deep with glass to prepare a sample. This sample was measured with a Kapton film for XRD without exposing it to air.
The powder X-ray diffraction measurement was performed under the following conditions using a D2 PHASER powder X-ray diffraction measurement device manufactured by BRUKER Corporation.

Tube voltage: 30 kV
Tube current: 10 mA
X-ray wavelength: Cu-Kα ray (1.5418 Å)
Optical system: focusing method Slit configuration: Soller slit 4°, divergence slit 1 mm, Kβ filter (Ni plate) used

Detector: Semiconductor detector Measurement range: 2θ=10-60 deg
Step width, scan speed: 0.05 deg, 0.05 deg/sec
1-2. (A) Chemical Composition of Sulfide and Solid Electrolyte Composition analysis was performed by ICP analysis (inductively coupled plasma atomic emission spectrometry).

1-3. Ionic Conductivity of Solid Electrolyte A circular pellet with a diameter of 10 mm (cross-sectional area S: 0.785 ^cm2 ) and a height (L) of 0.1 to 0.3 cm was molded from the solid electrolyte to prepare a sample. Electrode terminals were attached to the top and bottom of the sample, and measurements were made at 25°C by an AC impedance method (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV) to obtain a Cole-Cole plot. The real part Z' (Ω) at the point where -Z'' (Ω) is minimum near the right end of the arc observed in the high frequency region was taken as the bulk resistance R (Ω) of the electrolyte, and the ionic conductivity σ (S/cm) was calculated according to the following formula:

1-4. Exposure test of solid electrolyte (amount of _H2S generated)
First, a test apparatus (exposure test apparatus 1) used in the exposure test will be described with reference to FIG.
The exposure test apparatus 1 mainly comprises a flask 10 for humidifying nitrogen, a static mixer 20 for mixing humidified nitrogen and non-humidified nitrogen, a dew point meter 30 (M170/DMT152 manufactured by VAISALA) for measuring the moisture content of the mixed nitrogen, a double reaction tube 40 in which a measurement sample is placed, a dew point meter 50 for measuring the moisture content of the nitrogen discharged from the double reaction tube 40, and a hydrogen sulfide meter 60 (Model 3000RS manufactured by AMI) for measuring the hydrogen sulfide concentration contained in the discharged nitrogen, and is configured to be connected by pipes (not shown). The temperature of the flask 10 is set to 10° C. by a cooling tank 11.
The components were connected to each other using Teflon tubes with a diameter of 6 mm. In this figure, the tubes are omitted, and instead the flow of nitrogen is indicated by arrows.

The evaluation procedure was as follows.
About 1.5 g of powder sample (solid electrolyte) 41 was weighed out in a nitrogen glove box with a dew point of −80° C., and placed and sealed inside reaction tube 40 so as to be sandwiched between quartz wool 42. Evaluation was performed at room temperature (20° C.).
Nitrogen was supplied from a nitrogen source (not shown) at 0.02 MPa into the apparatus 1. The supplied nitrogen passed through a bifurcated branch pipe BP, and a portion of the nitrogen was supplied to the flask 10 and humidified. The remaining portion was supplied directly to the static mixer 20 as unhumidified nitrogen. The amount of nitrogen supplied to the flask 10 was adjusted by a needle valve V.

The dew point is controlled by adjusting the flow rate of the non-humidified nitrogen and the humidified nitrogen with a flow meter FM equipped with a needle valve. Specifically, the non-humidified nitrogen is supplied to the static mixer 20 at a flow rate of 800 mL/min and the humidified nitrogen is supplied at a flow rate of 10 to 30 mL/min, and mixed. The dew point of the mixed gas (mixture of non-humidified nitrogen and humidified nitrogen) is confirmed with the dew point meter 30.

After adjusting the dew point to -30°C, the three-way cock 43 was rotated to circulate the mixed gas inside the reaction tube 40 for the time shown in Table 1. The amount of hydrogen sulfide contained in the mixed gas that passed through the sample 41 was measured with a hydrogen sulfide meter 60. The amount of hydrogen sulfide was recorded at 15-second intervals and measured as the amount generated per minute (mL/min). For reference, the dew point of the mixed gas after exposure was also measured with a dew point meter 50.
In order to remove hydrogen sulfide from the nitrogen after measurement, the nitrogen was passed through an alkali trap 70.

1-5. Average particle size The average particle size (D50) is the particle size at which the particle size distribution cumulative curve is drawn and accumulated from the smallest particle size to reach 50% of the total, and is measured, for example, as follows: It was measured using a laser diffraction/scattering type particle size distribution analyzer (HORIBA, LA-950V2 model LA-950W2).
A mixture of dehydrated toluene (Wako Pure Chemical Industries, special grade) and tertiary butyl alcohol (Wako Pure Chemical Industries, special grade) in a mass ratio of 93.8:6.2 was used as the dispersion medium. 50 mL of the dispersion medium was injected into the flow cell of the device and circulated, and then the measurement target was added and ultrasonicated, and the particle size distribution was measured. The amount of the measurement target was adjusted so that the red light transmittance (R) corresponding to the particle concentration was 80 to 90% and the blue light transmittance (B) was 70 to 90% on the measurement screen specified by the device. In addition, the calculation conditions used 2.16 as the refractive index of the measurement target and 1.49 as the refractive index of the dispersion medium. In the distribution form setting, the number of repetitions was fixed at 15 times, and the particle size calculation was performed.

1-6. BET specific surface area: This was measured by a nitrogen method using a gas adsorption measurement device (AUTOSORB6 (manufactured by Sysmex Corporation)).
1-7. Residual Solvent Amount The residual solvent amount was measured using a gas chromatograph (Model 6890 manufactured by Agilent).

2-1. Synthesis of lithium sulfide In a 500 mL separable flask (equipped with an anchor stirring blade), 200 g of lithium hydroxide anhydride (manufactured by Honjo Chemical Co., Ltd., particle size range: 0.1 mm to 1.5 mm, moisture content: 1 mass% or less) was charged under nitrogen gas flow, and the temperature was raised to 200 ° C. using an oil bath while stirring at 60 rpm, and the temperature was maintained at 200 ° C. The upper part of the separable flask was maintained at 100 ° C. using a ribbon heater. The nitrogen was switched to hydrogen sulfide (manufactured by Tomoe Shokai Co., Ltd.) and the reaction between lithium hydroxide and hydrogen sulfide was carried out while supplying it at a flow rate of 500 mL / min. The moisture generated by the progress of the reaction was condensed and collected by a condenser, and 144 mL of water was collected after 6 hours of reaction, and no water was generated even though the reaction was continued for another 3 hours.

Next, while maintaining the temperature at 200° C., the hydrogen sulfide was replaced with nitrogen, and nitrogen was passed through for 20 minutes to replace the hydrogen sulfide in the flask with nitrogen.
The obtained lithium sulfide (Li ₂ S) powder was measured by potentiometric titration, and the lithium sulfide content (purity) was found to be 99.1 mass % and the specific surface area was 7 m ² /g.

2-2. Preparation of sulfide (A-1) (A) Pulverization step The Li ₂ S obtained in 2-1 above was pulverized in a pin mill (100UPZ, manufactured by Hosokawa Micron Corporation) equipped with a constant-volume feeder under a nitrogen atmosphere. The feeding rate was 80 g/min, and the disk rotation speed was 18,000 rpm.
Similarly, _P2S5 (manufactured by Thermophos), LiBr (manufactured by Honjo Chemical Co., Ltd.), and LiCl (manufactured by Honjo Chemical Co., Ltd.) were each pulverized in a pin mill. The _injection rate of _P2S5 was 140 g/min, that of LiBr was 230 g/min, and that of LiCl was 250 g _/ min. The rotation speed of the disk was 18,000 rpm in each case.

(B) Preparation of raw material mixture In a glove box under a nitrogen atmosphere, the compounds pulverized in (A) above were weighed out so that the molar ratio of _Li2S : _P2S5 :LiBr:LiCl was 47.5:12.5:15.0:25.0, and the total amount was 110 g _. The compounds were then placed in a glass container and roughly mixed by shaking the container.
110 g of the crudely mixed raw material was dispersed in a mixed solvent of 1140 mL of dehydrated toluene (manufactured by Wako Pure Chemical Industries, Ltd.) and 7 mL of dehydrated isobutyronitrile (manufactured by Kishida Chemical Industries, Ltd.) under a nitrogen atmosphere to obtain a slurry of about 10% by mass. The slurry was mixed and ground using a bead mill (LMZ015, manufactured by Ashizawa Finetech Co., Ltd.) while maintaining the slurry in a nitrogen atmosphere. Specifically, 456 g of zirconia beads having a diameter of 0.5 mm were used as the grinding medium, and the bead mill was operated under conditions of a peripheral speed of 12 m/s and a flow rate of 500 mL/min, the slurry was put into the mill, and circulated for 1 hour. The treated slurry was placed in a nitrogen-substituted Schlenk flask, and then dried under reduced pressure to prepare a raw material mixture.

(C) Calcination Step 30 g of the raw material mixture obtained in (B) above was dispersed in 300 mL of ethylbenzene (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a slurry. This slurry was placed in an autoclave (capacity 1000 mL, made of SUS316) equipped with a stirrer and a heating oil bath, and heat-treated at 200° C. for 2 hours while stirring at a rotation speed of 200 rpm. After the treatment, the mixture was dried under reduced pressure to remove the solvent, and a calcined product was obtained.

(D) Firing step The calcined product obtained in (C) above was heated in an electric furnace (F-1404-A, manufactured by Tokyo Glass Machinery Co., Ltd.) in a glove box under a nitrogen atmosphere. Specifically, an Al ₂ O ₃ sagger (999-60S, manufactured by Tokyo Glass Machinery Co., Ltd.) was placed in the electric furnace, and the temperature was raised from room temperature to 380°C in 1 hour and maintained at 380°C for 1 hour or more. Thereafter, the door of the electric furnace was opened, and the calcined product was quickly poured into the sagger, after which the door was immediately closed and heated for 1 hour. Thereafter, the sagger was removed from the electric furnace and slowly cooled to obtain an argyrodite-type solid electrolyte (sulfide (A)).

(E) Microparticulation step The obtained argyrodite-type solid electrolyte was dispersed in a mixed solvent of dehydrated toluene (manufactured by Wako Pure Chemical Industries, Ltd.) and dehydrated isobutyronitrile (manufactured by Kishida Chemical Industries, Ltd.) under a nitrogen atmosphere to obtain a slurry of about 8% by mass. The slurry was mixed and pulverized using a bead mill (LMZ015, manufactured by Ashizawa Finetech Co., Ltd.) while maintaining the nitrogen atmosphere. The treated slurry was placed in a nitrogen-substituted Schlenk flask and then dried under reduced pressure to obtain a microparticulated argyrodite-type solid electrolyte (sulfide (A-1)).

As a result of X-ray diffraction (XRD) measurement, peaks derived from an argyrodite-type crystal structure were observed at 2θ=25.5±1.0 deg and 29.9±1.0 deg in the XRD pattern.
The d50 was 1.7 μm, and the ionic conductivity was 4.9 mS/cm.

2-3. Preparation of Sulfide (A-2) A finely divided argyrodite-type solid electrolyte (sulfide (A-2)) was obtained in the same manner as in Production Example 1, except that the grinding conditions were changed in the (E) fine particle forming step.
As a result of X-ray diffraction (XRD) measurement, peaks derived from an argyrodite-type crystal structure were observed at 2θ=25.5±1.0 deg and 29.9±1.0 deg in the XRD pattern.
The d50 was 0.6 μm, and the ionic conductivity was 4.6 mS/cm.

(Examples 1 to 3)
Under a nitrogen atmosphere, the argyrodite-type solid electrolyte (sulfide (A-1)) obtained in 2-2 and P ₂ S ₅ (manufactured by Thermophos) were weighed into a 50 mL Schlenk flask under the conditions shown in Table 1. While maintaining the nitrogen atmosphere, 20 mL of toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., moisture content 10 ppm or less) was added to obtain a mixture. In Table 1, the amount of P ₂ S ₅ added is the amount added when sulfide A-1 or sulfide A-2 is 100 parts by mass.

Further, while maintaining the nitrogen atmosphere, a stirrer chip was added and the mixture was stirred at room temperature (25°C) for 72 hours. After that, the mixture was vacuum dried at room temperature for 1 hour to remove the solvent, thereby obtaining a dry powder. The obtained dry powder was vacuum dried at 80°C for 1 hour to obtain solid electrolytes-1 to -3.
The evaluation results of the obtained solid electrolytes in terms of ionic conductivity, amount of hydrogen sulfide generated, average particle size d50, and amount of hydrogen sulfide generated are shown in Table 1. In addition, it was confirmed from the results of powder X-ray diffraction measurement that all of the solid electrolytes had an argyrodite structure.
The amount of toluene remaining in the solid electrolyte was less than 0.1% by weight in all cases.

(Comparative Example 1)
As Comparative Example 1, the results for sulfide (A-1) are shown in Table 1.

(Examples 4 and 5)
Solid electrolytes 4 and 5 were obtained in the same manner as in Example 1, except that sulfide (A-2) was used instead of sulfide (A-1) in Example 1, and the amount of diphosphorus pentasulfide used and the mixing time were as shown in Table 1. The results are shown in Table 1.
The ICP analysis and particle size measurement results of the obtained solid electrolytes 4 and 5 showed no significant difference from the sulfide (A-2).
Moreover, it was confirmed from the results of powder X-ray diffraction measurement that all the solid electrolytes had an argyrodite structure.
(Comparative Example 2)
As Comparative Example 2, the results for sulfide (A-2) are shown in Table 1.

(Examples 6 and 7)
Under a nitrogen atmosphere, the sulfide (A-2) and P ₂ S ₅ (manufactured by Thermophos) were weighed into a 50 mL high-pressure reaction and decomposition vessel under the conditions shown in Table 1. While maintaining the nitrogen atmosphere, 20 mL of toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., moisture content 10 ppm or less) was added to obtain a mixture. Furthermore, while maintaining the nitrogen atmosphere, a stirrer chip was added, the vessel was sealed, and stirred at 80°C for 8 hours. Thereafter, the mixture was vacuum-dried at room temperature for 1 hour to remove the solvent, thereby obtaining a dry powder. The obtained dry powder was vacuum-dried at 80°C for 1 hour to obtain solid electrolytes-6 and 7.
The evaluation results of the obtained solid electrolyte with respect to ionic conductivity, amount of hydrogen sulfide generated, average particle size d50 and amount of hydrogen sulfide generated are shown in Table 1.

The amount of toluene remaining in the solid electrolyte was less than 0.1% by weight in all cases.
The ICP analysis and particle size measurement results of the obtained solid electrolytes-6 and 7 showed no significant difference from the sulfide (A-2).
Moreover, it was confirmed from the results of powder X-ray diffraction measurement that all the solid electrolytes had an argyrodite structure.

(Comparative Example 3)
0.9445 g of the sulfide (A-1), 0.0505 g of P ₂ S ₅ (manufactured by Thermophos), and 26.5 g of zirconia balls having a diameter of 2 mm were placed in a zirconia pot (45 mL), which was completely sealed and the inside of the pot was filled with argon atmosphere. Without heating or cooling, the mixture was treated (mechanical milling) for 2 hours at a rotation speed of 100 rpm in a planetary ball mill (manufactured by Fritsch: model number P-7) as a "pulverizer" to obtain a powder.

The obtained powder was filled into a glass container and heated at 200° C. for 2 hours to obtain a solid electrolyte-C1.
The evaluation results of the obtained solid electrolyte-C1 in terms of ionic conductivity, amount of hydrogen sulfide generated, average particle size d50, and amount of hydrogen sulfide generated are shown in Table 1. In addition, it was confirmed from the results of the powder X-ray diffraction measurement device that the solid electrolyte-C1 has an argyrodite structure.

The amount of P ₂ S ₅ added (parts by mass) in Table 1 represents the amount of phosphorus sulfide (B) added (parts by mass) relative to 100.0 parts by mass of sulfide (A).
Note 1) in Table 1 means that "the obtained powder was filled into a glass vial container and heated in a tubular electric furnace at 200° C. for 2 hours" as described in Comparative Example 3.

A homogeneous solid electrolyte was easily obtained by the manufacturing method of the present invention. It was also found that the solid electrolyte obtained by the manufacturing method of the present invention can significantly reduce the generation of _H2S and can also improve the suppression of the decrease in ionic conductivity, compared to the sulfide not subjected to the above-mentioned mixing step (corresponding to Comparative Examples 1 and 2).
In Comparative Example 3, solid electrolyte-C1 was obtained by a manufacturing method using a pulverizer (planetary ball mill) corresponding to the manufacturing method of Patent Document 2. However, although the amount of H ₂ S generated by solid electrolyte-C1 was suppressed to the same level as that of the solid electrolyte manufactured by this manufacturing method, the ion conductivity was significantly reduced and the particle size became large due to granulation. From this, it was confirmed that it is necessary to perform the mixing step without using a "pulverizer". In addition, it was found that when a "pulverizer" is used in the "mixing step", the particle size needs to be reduced in order to be used in a solid electrolyte layer for an all-solid-state battery, and therefore a separate pulverization step is required.

In contrast, the surface of the solid electrolyte produced by this manufacturing method did not become amorphous, so there was no need for a subsequent heating step to crystallize it. As a result, no granulation was caused by heating, and no further pulverization step was required.

According to the method for producing a solid electrolyte of the present embodiment, it is possible to uniformly and easily produce a solid electrolyte having a cubic argyrodite-type crystal structure that improves water resistance, suppresses the generation of _H2S , and suppresses the decrease in ionic conductivity.
The crystalline solid electrolyte obtained by the manufacturing method of this embodiment is suitable for use in batteries, particularly in batteries used in information-related devices and communication devices such as personal computers, video cameras, and mobile phones.

1. Test equipment used in exposure tests (exposure test equipment)
10. Flask for humidifying nitrogen 11. Cooling tank 20. Static mixer 30. Dew point meter 40. Double reaction tube for placing the measurement sample 41. Powder sample 42. Quartz wool 43. Three-way cock 50. Dew point meter for measuring the moisture content of the nitrogen discharged from the double reaction tube 40 60. Hydrogen sulfide measuring instrument 70. Alkaline trap V. Needle valve

Claims (13)

In the presence of at least one solvent selected from a non-polar solvent and an aprotic solvent,
A step of mixing (A) a sulfide containing lithium atoms, phosphorus atoms, and sulfur atoms and having an argyrodite-type crystal structure and (B) phosphorus sulfide without using a grinder;
A drying step for removing the solvent;
The method for producing a solid electrolyte comprising the steps of: The method for producing a solid electrolyte according to claim 1, wherein the mixing step is carried out in at least one solvent selected from a non-polar solvent and an aprotic solvent. The method for producing a solid electrolyte according to claim 1 or 2, wherein the phosphorus sulfide (B) is diphosphorus pentasulfide. The method for producing a solid electrolyte according to any one of claims 1 to 3, wherein heating is performed in the mixing step. The method for producing a solid electrolyte according to claim 4, wherein the heating in the mixing step is performed at less than 100°C. The method for producing a solid electrolyte according to any one of claims 1 to 5, wherein the amount of phosphorus sulfide (B) added in the mixing step is 0.5 parts by mass or more and 30.0 parts by mass or less per 100.0 parts by mass of sulfide (A). The method for producing a solid electrolyte according to any one of claims 1 to 6, wherein at least one solvent selected from the nonpolar solvent and the aprotic solvent is one or more selected from the group consisting of saturated hydrocarbons, unsaturated hydrocarbons, and aromatic hydrocarbons. The method for producing a solid electrolyte according to any one of claims 1 to 7, wherein at least one solvent selected from the non-polar solvent and the aprotic solvent is toluene, xylene, or heptane. The method for producing a solid electrolyte according to any one of claims 1 to 8, wherein the sulfide (A) further contains a halogen atom. The method for producing a solid electrolyte according to claim 9, wherein the halogen atom is at least one selected from the group consisting of chlorine atoms and bromine atoms. The method for producing a solid electrolyte according to any one of claims 1 to 10, in which (A) sulfide and (B) phosphorus sulfide are used without being pulverized. The method for producing a solid electrolyte according to any one of claims 1 to 11, in which heating to 200°C or higher is not performed after the drying step. The method for producing a solid electrolyte according to any one of claims 1 to 12, which does not use a media-type grinder.