Method for producing sulfide

Abstract

Provided is a method for producing a sulfide. The sulfide contains Li, P, S, and M as main constituent elements, M being at least one selected from Ge and Sn. The method for producing a sulfide, which is a liquid-phase synthesis method with which it is possible to reduce the amount of organic solvent used, comprises: a first step for obtaining a first solution by adding an Li source, an S source, and an M source to an aqueous solvent in which the amount of an organic solvent is 50 wt% or less; a second step for obtaining a second solution by adding P2S5 as a P source to the first solution; and a third step for removing the aqueous solvent in the second solution and performing crystallization by heat treatment.

Description

Method for producing sulfides

[0001] The present disclosure relates to a method for producing a sulfide, and in particular to a method for producing a sulfide useful as an inorganic solid electrolyte for an all-solid-state battery.

[0002] All-solid-state batteries using inorganic solid electrolytes are expected to be safe and reliable next-generation batteries. Among inorganic solid electrolytes, sulfide-based solid electrolytes, which have high ionic conductivity and excellent formability, have been actively researched (Patent Document 1).

[0003] N. Kamaya et al., Nat. Energy, 10 (2011) 682.

[0004] Conventionally, sulfide-based solid electrolytes have been produced by solid-phase synthesis or mechanochemical methods. In this disclosure, we focus on liquid-phase synthesis methods that are suitable for mass production. Until now, organic solvents have been widely used as reaction media in liquid-phase synthesis methods for sulfide-based solid electrolytes. However, from the perspective of reducing environmental impact, it is preferable to be able to reduce the amount of organic solvent used. In this disclosure, we provide a method for producing sulfides using a liquid-phase synthesis method that can reduce the amount of organic solvent used.

[0005] The present disclosure includes the following aspects: [Item 1] A method for producing a sulfide, wherein the sulfide has Li, P, S, and M as main constituent elements, and M is at least one selected from Ge and Sn, and the production method includes: a first step of adding a Li source, an S source, and an M source to an aqueous solvent having an organic solvent amount of 50 wt % or less to obtain a first solution; ２ S ５ to obtain a second solution, and a third step of removing the aqueous solvent and crystallizing the second solution by heat treatment. [Item 2] The manufacturing method according to Item 1, wherein the amount of the organic solvent in the aqueous solvent is 25% by weight or less. [Item 3] The manufacturing method according to Item 1 or 2, wherein the amount of the organic solvent in the aqueous solvent is 5% by weight or less. [Item 4] The manufacturing method according to any one of Items 1 to 3, wherein the reaction in the first solution is advanced by heat treatment at 50°C or higher and 120°C or lower. [Item 5] The manufacturing method according to any one of Items 1 to 3, wherein the reaction in the first solution is advanced by heat treatment at 50°C or higher and 120°C or lower. ４４－ ions or SnS ４ ４－ Item 6. The method according to Item 4, wherein the M source is GeS ４ ４－ ions or SnS ４ ４－ [Item 7] The manufacturing method according to any one of Items 1 to 5, wherein the Ge source does not have GeS ions in its structure. ２ [Item 8] The manufacturing method according to any one of Items 1 to 6, wherein the Sn source contains metallic tin. [Item 9] The manufacturing method according to any one of Items 1 to 8, wherein the S source contains elemental sulfur. [Item 10] The manufacturing method according to any one of Items 1 to 9, wherein the sulfide has an LGPS-type crystal phase. [Item 11] The manufacturing method according to any one of Items 1 to 10, wherein in the third step, the heat treatment is carried out at 450°C or higher and 800°C or lower. [Item 12] The sulfide is Li ３．０±０．２ P.S. ４．０±０．２ -Li ４．０±０．２ MS ４．０±０．２ The manufacturing method according to any one of items 1 to 11, wherein the sulfide is a compound that can be represented by the formula: [Item 13] The sulfide is a compound that can be represented by the formula: ３ P.O. ４ [Item 14] The manufacturing method according to any one of Items 1 to 13, wherein the sulfide is an electrolyte for a solid-state battery. [Item 15] A manufacturing method for a solid-state battery, comprising a step of using the sulfide obtained by the manufacturing method according to any one of Items 1 to 14 as a component of an electrolyte layer, a positive electrode, or a negative electrode.

[0006] The sulfide production method of the present disclosure uses liquid-phase synthesis, making it suitable for mass production and industrially advantageous. For example, liquid-phase synthesis has the advantages of enabling homogeneous mixing, shortening heat treatment time, simplifying synthesis equipment, and enabling processes such as misting in the liquid phase (aqueous solution), impregnation into gaps, and coating. Furthermore, the sulfide production method of the present disclosure reduces the amount of organic solvent used and has a low environmental impact. The sulfides obtained by the present disclosure are useful as solid electrolytes for batteries.

[0007] 1 is a synthesis flowchart for Comparative Example 1; FIG. 2 is an XRD pattern of a sample obtained in Comparative Example 1; FIG. 3 is a synthesis flowchart for Example 1; FIG. 4 is an XRD pattern of a sample obtained in Example 1 (HT 600°C); FIG. 5 is a Raman spectrum of a sample obtained in Example 1 (HT 600°C); FIG. 6 is a graph showing the temperature dependence of ionic conductivity of a sample obtained in Example 1; FIG. 7 is a graph showing the SEM and EDX mapping results of a sample obtained in Example 1 (HT 600°C); FIG. 8 is a graph showing the charge / discharge curve and cycle characteristics of an all-solid-state cell prepared using the sample obtained in Example 1 as a solid electrolyte for a positive electrode composite; and FIG. 9 is a graph showing the XRD pattern and temperature dependence of ionic conductivity of samples obtained in Example 2 (HT (600°C holding time): 30 min) and Example 3 (HT (600°C holding time): 0 min) (Example 1 (HT: 2 h) is also included for reference). 1 shows XRD patterns of samples obtained in Examples 6 to 8 (550°C, 500°C, 450°C) and Comparative Examples 2 to 4 (400°C, 350°C, 200°C) (Reference: Example 1 (600°C)). 1 shows a graph showing the temperature dependence of ionic conductivity of samples obtained in Examples 6 to 8 (550°C, 500°C, 450°C) and Comparative Examples 2 to 4 (400°C, 350°C, 200°C) (Reference: Example 1 (600°C)). 1 shows a graph showing the relationship between ionic conductivity at 25°C and heat treatment temperature of room-temperature molded samples obtained in Examples 6 to 8 (550°C, 500°C, 450°C) and Comparative Examples 2 to 4 (400°C, 350°C, 200°C) (Reference: Example 1 (600°C)). 1 is a table summarizing the test results of the samples obtained in Examples 6 to 8 (550°C, 500°C, 450°C) and Comparative Examples 2 to 4 (400°C, 350°C, 200°C) (Reference: Example 1 (600°C)). ３ aq) (Reference: Example 1 (water only)). Example 9 (water + NH ３ aq) (Reference: Example 1 (water only)) Example 9 (water + NH ３ aq) of the sample obtained ３１ P NMR spectrum (Reference: Example 1 (water only)) Example 9 (water + NH ３10 is a graph showing the temperature dependence of ionic conductivity of a sample obtained by the method (aq) (Reference: Example 1 (water only)). FIG. 11 is a synthesis flowchart in Example 10.

[0008] <Method of Producing Sulfide> The method of producing a sulfide in the present disclosure includes a first step of adding a Li source, an S source, and an M source to an aqueous solvent in which the amount of an organic solvent is 50 wt % or less to obtain a first solution; ２ S ５ to obtain a second solution, and a third step of removing the aqueous solvent from the second solution and crystallizing the solution by heat treatment. Each step is preferably performed under an inert atmosphere (e.g., a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, or the like) while avoiding exposure to the air.

[0009] [Sulfide] The sulfide obtained by the production method of the present disclosure has Li, P, S, and M as main constituent elements, where M is at least one element selected from Ge and Sn.

[0010] In the sulfide of the present disclosure, the total proportion of Li, P, S, and M may be 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, 99% by weight or more, 98% by weight or more, or 99% by weight or more, or may be 100% by weight.

[0011] The sulfides in the present disclosure may have an LGPS-type crystalline phase. Sulfides having an LGPS-type crystalline phase are generally [M / P]S ４ Tetrahedron and PS ４ (M is Ge, Sn, etc.) The presence of lithium ions in the spaces in the framework formed by the tetrahedral units exhibits high lithium ion conductivity. Specific examples of sulfides in the LGPS crystal phase include Li １０ GeP ２ S １２ , Li １０ SnP ２ S １２ In the present disclosure, sulfides having an LGPS-type crystal phase include compounds having an isomorphous structure in which the M element is partially or completely substituted, for example, Li SiO 2 in which Ge and Sn are mixed at any ratio. １０ (Ge ｘ Sn１－ｘ ) P ２ S １２ (0<x<1, for example, x is 0.3 or more, 0.6 or more, 0.9 or more, or 0.95 or more), compounds in which part of the sulfur (for example, 10% or less, 5% or less, 1% or less) is substituted with anions such as oxygen or halogen (chlorine, bromine, iodine, etc.), and compounds in which P is in excess relative to Ge (for example, 120% or less, 110% or less, 105% or less relative to Ge). Sulfides having an LGPS-type crystal phase include Li １０±０．４ M ±０．２ P ２±０．２ S １２±０．２ O ±０．２ X ±０．２ In the formula, ±0.4 and ±0.2 indicate that the fluctuation range of each value is -0.4 or more and +0.4 or less and -0.2 or more and +0.2 or less, respectively, which is due to composition fluctuations due to defects or substitutions within the crystal lattice. ±0.4 may be ±0.35, ±0.30, ±0.25, ±0.20, ±0.15, ±0.10, ±0.05, ±0.03, or ±0.01. ±0.2 may be ±0.15, ±0.10, ±0.05, ±0.03, or ±0.01, respectively.

[0012] The sulfide in this disclosure is Li ３．０±０．２ P.S. ４．０±０．２ -Li ４．０±０．２ MS ４．０±０．２ Here, ±0.2 indicates that the fluctuation range of each value is between -0.2 and +0.2, which is due to composition fluctuations caused by defects or substitutions in the crystal lattice. ±0.2 may be ±0.15, ±0.10, ±0.05, ±0.03, or ±0.01.

[0013] The sulfide in this disclosure contains Li as an impurity. ３ P.O. ４ and the amount may be 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, 3% by weight or more, or 5% by weight or more, for example 1% by weight or more, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7.5% by weight or less, 5% by weight or less, or 3% by weight or less, and in one embodiment is 0.1% by weight or more and 10% by weight or less, based on the sulfides.

[0014] [First Step] In the first step, a Li source, an S source, and an M source are added to an aqueous solvent containing an organic solvent in an amount of 50 wt % or less to obtain a first solution. The first solution does not contain a P source.

[0015] [Aqueous Solvent] An aqueous solvent is a solvent primarily composed of water. In the aqueous solvent, the amount of organic solvent may be 50 wt% or less, 40 wt% or less, 30 wt% or less, 25 wt% or less, 20 wt% or less, 10 wt% or less, 5 wt% or less, 3 wt% or less, 1 wt% or less, 0.5 wt% or less, 0.1 wt% or less, or 0 wt%. From the viewpoint of reducing the environmental impact, a small amount of organic solvent is preferably used, for example, 25 wt% or less, particularly 5 wt% or less, or no organic solvent may be used. When an organic solvent is used, the type is not particularly limited, and examples include water-soluble organic solvents that are miscible with water, highly volatile, and easily removed (e.g., ether-based solvents such as THF and 1,4-dioxane). A water-immiscible organic solvent with a low specific gravity (less than 1, e.g., less than 0.8) (e.g., hydrocarbon solvents such as hexane and heptane) may be added to prevent contact with the air.

[0016] [Li Source] Examples of the Li source include lithium sulfide and metallic lithium.

[0017] [S Source] Examples of the S source include lithium sulfide, germanium sulfide, tin sulfide, and elemental sulfur, for example, elemental sulfur.

[0018] [M Source (Ge Source, Sn Source)] Examples of the Ge source include germanium sulfide and metallic germanium, such as GeS ２ is.

[0019] Examples of the Sn source include tin sulfide and metallic tin, for example metallic tin.

[0020] The M source is GeS ４ ４－ ions or SnS ４ ４－ The ions may not be present in the structure.

[0021] [Addition of Raw Materials] The raw materials are added to an aqueous solvent and mixed. Various methods can be used to add the raw materials. The raw materials may be mixed by dropping them into the aqueous medium as an aqueous solution (aqueous dispersion), or the raw materials may be mixed in advance in solid form and added to the aqueous medium simultaneously. Mixing is preferably performed with stirring.

[0022] The amount of each raw material added may be adjusted to achieve the stoichiometric ratio of the composition of the target sulfide (e.g., LGPS-type crystalline phase sulfide). The total concentration of the raw materials in the first solution may be 3 wt% or more, 5 wt% or more, 8 wt% or more, 10 wt% or more, 12 wt% or more, or 15 wt% or more, and may be 60 wt% or less, 50 wt% or less, 40 wt% or less, 30 wt% or less, 20 wt% or less, or 10 wt% or less, and in one embodiment, is 10 wt% or more and 30 wt% or less.

[0023] [Reaction] The reaction of the raw materials may proceed in the first solution. ４ ４－ ions or SnS ４ ４－ Intermediate products such as ions may also be produced.

[0024] The reaction can proceed at room temperature, but heat treatment can accelerate the reaction. The heat treatment temperature may be 30°C or higher, 40°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, or 90°C or higher, and 200°C or lower, 150°C or lower, 120°C or lower, or 100°C or lower, and in one embodiment, 50°C or higher and 120°C or lower. The heat treatment time may vary depending on the heat treatment temperature, but may be 1 hour or higher, 3 hours or higher, 6 hours or higher, 8 hours or higher, 10 hours or higher, or 12 hours or higher, and may be 48 hours or lower, 40 hours or lower, 32 hours or lower, 24 hours or lower, 16 hours or lower, 12 hours or lower, 8 hours or lower, 6 hours or lower, or 4 hours or lower, and in one embodiment, 3 hours or higher and 12 hours or lower. The heat treatment time can be shortened by pulverizing the raw materials by milling or the like. In one embodiment, the heat treatment may be performed at 50°C or higher and 120°C or lower for 3 hours or higher and 12 hours or lower. When the first solution is heat-treated, the solvent is not distilled off but is allowed to remain by reflux or the like in order to carry out liquid phase synthesis in the second step.

[0025] The pH of the first solution may be 7.5 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, or 13 or more, and may be 14 or less, 13.5 or less, 13 or less, 12.5 or less, 12 or less, 11.5 or less, or 10 or less, and in one embodiment, is 10 or more and 14 or less. Here, the pH of the first solution refers to P ２ S ５ It may also refer to the pH at the time of addition (immediately before the second step). The pH of the first solution may be adjusted to keep it basic, for example, by adding aqueous ammonia or the like.

[0026] [Second step] In the second step, P is added to the first solution as a P source. ２ S ５ The sulfide of the present disclosure can be suitably obtained by separately carrying out the second step after the first step.

[0027] The pH of the second solution may be 7.5 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, or 13 or more, and may be 14 or less, 13.5 or less, 13 or less, 12.5 or less, 12 or less, 11.5 or less, or 10 or less, and in one embodiment, is 9 or more and 13 or less. Here, the pH of the second solution refers to P ２ S ５ may refer to the pH after stirring for 3 minutes at room temperature. The pH may be adjusted to keep the second solution basic, for example, by adding aqueous ammonia.

[0028] [P source] Examples of the P source include phosphorus sulfide, elemental phosphorus, etc. In one embodiment, phosphorus sulfide, particularly diphosphorus pentasulfide (P ２ S ５ ) may be.

[0029] [Addition of P Source] The P source is added to the first solution and mixed. Various methods can be used to add the P source. The P source may be added in powder form to the first solution and mixed. Mixing is preferably performed by stirring. The P source may be adjusted to have a stoichiometric ratio of the composition of the target sulfide (e.g., LGPS-type crystalline phase sulfide). The addition of the P source causes a reaction between the components in the second solution (e.g., a reaction between the components in the first solution and the P source), but the reaction may also proceed during the third step described below.

[0030] [Third Step] In the third step, the aqueous solvent is removed from the second solution, and the second solution is crystallized by heat treatment.

[0031] [Removal of aqueous solvent] Examples of methods for removing the aqueous solvent include reduced pressure and heat treatment. Heat treatment may be performed under reduced pressure. The temperature of the heat treatment at the time of removing the transition solvent is not limited as long as the solvent can be removed, but the removal of the aqueous solvent may be performed simultaneously with crystallization by heat treatment, in which case the heat treatment is performed up to the temperature described below. The reaction in the second solution may be progressing simultaneously with the removal of the aqueous solvent.

[0032] [Crystallization by Heat Treatment] Crystallization can be promoted by heat treatment. The reaction in the second solution may proceed simultaneously with the crystallization by heat treatment. The heat treatment temperature may be 300 ° C. or higher, 350 ° C. or higher, 400 ° C. or higher, 425 ° C. or higher, 450 ° C. or higher, 475 ° C. or higher, 500 ° C. or higher, 525 ° C. or higher, 550 ° C. or higher, 575 ° C. or higher, or 600 ° C. or higher, preferably 400 ° C. or higher, particularly 450 ° C. or higher, and 800 ° C. or lower, 775 ° C. or lower, 750 ° C. or lower, 725 ° C. or lower, 700 ° C. or lower, 675 ° C. or lower, 650 ° C. or lower, 625 ° C. or lower, 600 ° C. or lower, 575 ° C. or lower, 550 ° C. or lower, 525 ° C. or lower, 500 ° C. or lower, 475 ° C. or lower, 450 ° C. or lower, or 425 ° C. or lower, for example, 700 ° C. or lower, particularly 600 ° C. or lower, and in a preferred embodiment, 450 ° C. or higher and 800 ° C. or lower, particularly 450 ° C. or higher and 600 ° C. or lower. In particular, it is preferable that the maximum temperature reached during heat treatment is equal to or higher than the above lower limit. The heat treatment time may vary depending on the heat treatment temperature, but may be 30 seconds or more, 1 minute or more, 5 minutes or more, 10 minutes or more, 20 minutes or more, 30 minutes or more, 1 hour or more, 3 hours or more, 6 hours or more, 8 hours or more, 10 hours or more, or 12 hours or more, or 48 hours or less, 40 hours or less, 32 hours or less, 24 hours or less, 16 hours or less, 12 hours or less, 10 hours or less, 8 hours or less, 6 hours or less, 4 hours or less, 3 hours or less, 2 hours or less, 1 hour or less, 30 minutes or less, 15 minutes or less, 10 minutes or less, 5 minutes or less, 3 minutes or less, or 1 minute or less. In one embodiment, the heat treatment is performed at 450 ° C. or higher and 600 ° C. or lower for 1 minute to 5 hours, for example, 30 minutes to 3 hours.

[0033] <Uses of sulfide> The sulfide in the present disclosure can be suitably used as an inorganic solid electrolyte, which is a component of each member (e.g., a positive electrode, a negative electrode, or a solid electrolyte layer) of a battery (particularly a lithium ion battery). Here, the battery is preferably a solid-state battery (all-solid-state battery).

[0034] <Battery Manufacturing Method> The battery manufacturing method according to the present disclosure includes a step of using the sulfide obtained by the sulfide manufacturing method described above. The sulfide according to the present disclosure can be used as an electrolyte in a known battery manufacturing method. For example, the solid-state battery manufacturing method according to the present disclosure may include a step of mixing the sulfide with other components in the electrolyte layer, positive electrode, or negative electrode, and may further include a step of coating, drying, molding, or the like of the obtained mixture, or a step of stacking each component.

[0035] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims.

[0036] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0037] <Measurement Method> The obtained samples were evaluated by X-ray diffraction (XRD) measurement and Raman spectroscopic analysis. In addition, the samples were pressed at room temperature at 360 MPa to obtain powder compacts, and the ionic conductivity of the resulting compacts was determined by the AC impedance method. Furthermore, the obtained samples were used as solid electrolytes in all-solid-state cells (Li-In / Li ３ P.S. ４ / NMC-Li １０ GeP ２ S １２ ) was prepared, and the current density was 0.13 mA cm -２ A constant current charge / discharge test was carried out at room temperature.

[0038] Comparative Examples Comparative Example 1 A synthesis flow chart is shown in FIG. ２ S: Mitsuwa Chemicals, 99.9%, P ２ S ５ :Sigma-Aldrich, 99%, GeS ２ : High purity chemical, 99.99% was used as the starting material, and in a glass vessel with a volume of 110 mL, Li ２ S and P ２ S ５ , GeS ２ The composition of the feed is Li １０ GeP ２ S １２ Li so that the stoichiometric ratio２ S:P ２ S ５ : GeS ２ After weighing out 2.0 g of the solid electrolyte precursor solution at a molar ratio of 5:1:1, 10 g of ion-exchanged water was added, and the solution was heated to 80°C and stirred for 6 hours to prepare a solid electrolyte precursor solution. The resulting precursor solution was dried under reduced pressure at 200°C for 3 hours (W-LGPS (vac 200°C) sample), and then heat-treated at 600°C for 2 hours in a dry argon atmosphere to obtain a powder sample (W-LGPS (HT 600°C)). The heating rate was 10°C / min to reach 570°C. Thereafter, the heating rate was 1°C / min to reach 600°C. The temperature was lowered to room temperature in the furnace. In the above process, the raw materials were weighed in a glove box filled with Ar gas, and then transferred to the air in a sealed container to avoid exposure to the atmosphere. After exposure to the atmosphere, ion-exchanged water was added immediately, and the container was sealed again to allow the reaction to proceed.

[0039] [Results of Comparative Example] Figure 2 shows the XRD pattern of the sample obtained after heat treatment at 600°C for 2 hours. ４ GeS ４ and Li ３ P.O. ４ It can be seen that a mixture of Li and Ge is obtained. ２ S and GeS ２ reacts with Li ４ GeS ４ It can be seen that the following can be obtained. Focusing on P, Li ２ S and P ２ S ５ and water (H ２ O) reacts to Li ３ P.O. ４ This shows that, as per the public information and general understanding, the Li １０ GeP ２ S １２ It is clear that the synthesis of Li is not easy. ４ GeS ４ and Li ３ P.O. ４ Li １０ GeP ２ S １２It is known that the conductivity of SiO2 is at least two orders of magnitude lower than that of SiO2.

[0040] <Example> From the examination of comparative examples, Li ２ S and P ２ S ５ and H ２ O reacts and Li ３ P.O. ４ From the findings obtained in the research of the present inventors, it is clear that it is necessary to reduce the reaction in which Li ２ S and P ２ S ５ reacts with Li ３ P.S. ４ is produced, which is dissolved in water and ＋ and P.S. ４ ３－ When this happens, ２ S ５ Compared to Li ３ P.O. ４ (i.e. PO ４ ３－ Based on this information, the rate of Li １０ GeP ２ S １２ The present disclosure was completed as a result of extensive research and development into processes by which this phase can be obtained.

[0041] [Example 1: 600 °C 2 h] Figure 3 shows a synthesis flow chart. The basic experimental setup is the same as in Comparative Example 1. The starting material, Li ２ S and GeS ２ After weighing, 10 g of ion-exchanged water was added and stirred at 80°C for 6 hours to obtain Li ２ S-GeS ２ The resulting aqueous solution was added with P ２ S ５ The precursor solution was obtained by adding Li and stirring at room temperature for 3 minutes. ２ S and P ２ S ５ , GeS ２ The composition of the feed is Li １０ GeP ２ S １２ Li so that the stoichiometric ratio ２ S:P ２ S５ : GeS ２ The molar ratio of the precursor solution was adjusted to 5:1:1. The resulting aqueous precursor solution was dried under reduced pressure at 200°C for 3 hours, and then heat-treated at 600°C for 2 hours in a dry argon atmosphere to obtain a powder sample (LGPS (HT600°C)).

[0042] [Results of Example 1] FIG. 4 shows the XRD pattern of the sample (LGPS (HT600°C)) obtained in Example 1. As a result of the XRD measurement, the target crystalline phase, Li １０ GeP ２ S １２ The diffraction pattern of the Li type crystal was mainly observed. １０ GeP ２ S １２ It was found that Li-type crystals were obtained as the main phase. ３ P.O. ４ Although Li was also confirmed, the amount of Li produced was not large. １０ GeP ２ S １２ It is expected that the amount of PS is at most 10 wt % or less compared to the amount of PS. ４ ３－ and GeS ４ ４－ A band that can be assigned to the ionic conductivity of the sample obtained in Example 1 (LGPS (HT 600°C)) compacted at room temperature was observed. Figure 6 shows the temperature dependence of the ionic conductivity of the sample obtained in Example 1 (LGPS (HT 600°C)). The ionic conductivity of the prepared sample showed an Arrhenius-type temperature dependence. The ionic conductivity of the sample compacted at room temperature (25°C) was 1.6 × 10 -３ SCM -１This confirmed that the process of the present disclosure can produce a solid electrolyte with ionic conductivity at a practical level. Figure 7 shows the results of SEM and EDX mapping of the sample obtained in Example 1. It can be seen that oxygen is unevenly distributed. Figure 8 shows the charge / discharge curves and cycle characteristics of an all-solid-state cell produced using the sample obtained in Example 1 as the solid electrolyte for the positive electrode composite. It was confirmed that the all-solid-state cell produced using the obtained electrolyte operated reversibly even after 200 or more charge / discharge cycles at room temperature, further demonstrating the usefulness of the solid electrolyte obtained in the present disclosure.

[0043] [Examples 2 and 3: 600°C Holding Time of 30 Minutes and 0 Minutes] Powder samples were obtained in the same manner as in Example 1, except that the heat treatment time at 600°C (600°C holding time) was reduced to 30 minutes (Example 2) and 0 minutes (Example 3).

[0044] [Results of Examples 2 and 3] Figure 9(a) shows the XRD patterns of the samples (LGPS (HT600°C)) obtained in Examples 2 and 3. In both cases, the target crystalline phase, Li １０ GeP ２ S １２ The diffraction pattern of the Li type crystal was mainly observed. １０ GeP ２ S １２ Figure 9(b) shows the temperature dependence of the ionic conductivity of the samples formed at room temperature in Examples 2 and 3. The samples formed at room temperature had an ionic conductivity of 1.2 × 10 at 25 °C. －３ SCM －１ (Example 2) 0.75 × 10 －３ SCM －１ (Example 3) and about 1 × 10 －３ SCM －１ It was confirmed that a practical solid electrolyte can be synthesized even with short-term heat treatment.

[0045] Examples 4 and 5: Heat Treatment Temperature of 580°C or 620°C Powder samples were obtained in the same manner as in Example 1, except that the heat treatment temperature at 600°C was changed to 580°C or 620°C.

[0046] [Results of Examples 4 and 5] In both cases, the target crystalline phase, Li １０ GeP ２ S １２ The diffraction pattern of the Li type crystal was mainly observed. １０ GeP ２ S １２ It was found that the type crystal was obtained as the main phase.

[0047] Examples 6 to 8: Heat Treatment Temperatures of 550°C, 500°C, and 450°C Powder samples were obtained in the same manner as in Example 1, except that the heat treatment temperature at 600°C was changed to 550°C, 500°C, or 450°C, respectively.

[0048] Comparative Examples 2 to 4: Heat Treatment Temperatures of 400°C, 350°C, and 200°C Powder samples were obtained in the same manner as in Example 1, except that the heat treatment temperature at 600°C was changed to 400°C, 350°C, or 200°C, respectively.

[0049] [Results of Examples 6 to 8 and Comparative Examples 2 to 4] Figure 10 shows the XRD patterns of the samples obtained in Examples 6 to 8 and Comparative Examples 2 to 4 (unassigned peaks are attributed to LGPS-type crystals). In all of Examples 6 to 8 (heat treatment at 450°C or higher), Li １０ GeP ２ S １２ It was found that the Li-type crystal (LGPS-type crystal) was obtained as the main phase. ３ P.O. ４ Diffraction patterns attributed to Li were also observed. ３ P.O. ４ , Li ３ P.S. ４ The intensity of the peaks not attributable to either Li or LGPS-type crystals decreased as the heat treatment temperature increased. １０ GeP ２ S １２ It was suggested that the Li-type crystal was not formed. ３ P.S. ４ It is presumed that LGPS is formed by the reaction of the Ge component contained in the amorphous phase or the phase that cannot be assigned to Li.３ P.S. ４ In Comparative Example 4 (heat treatment at 200°C), a peak that could not be assigned to Li ３ P.S. ４ A peak was observed near the

[0050] Figure 11 shows the temperature dependence of the ionic conductivity of the room temperature molded samples obtained in samples 6 to 8 and comparative examples 2 to 4. Figure 12 shows the relationship between the ionic conductivity at 25°C and the heat treatment temperature of the room temperature molded samples obtained in samples 6 to 8 and comparative examples 2 to 4. Figure 13 summarizes the test results (precipitated phases and ionic conductivity, etc.) of the samples obtained in samples 6 to 8 and comparative examples 2 to 4. By heat treating at 450°C or higher, the ionic conductivity improved due to the precipitation of LGPS-type crystals with high ionic conductivity. In the sample heat treated at 600°C, where the peak intensity of other phases was relatively small, the maximum ionic conductivity of 1.6 × 10 -３ SCM -１ It showed an ionic conductivity of

[0051] Example 9: Ammonia water (NH ３ aq.) Li prepared using water as a solvent １０ GeP ２ S １２ In the electrolyte, about 25% of the total P is PO ４ ３- In this experiment, it was found that P ２ S ５ Keeping the aqueous solution basic before addition, ２ S ５ Ammonia water (NH ３ aq.) was used to attempt production.

[0052] P ２ S ５ Before the addition, 5 mL of ammonia water (28%: Fujifilm Wako Pure Chemical Industries) was added, and then P ２ S ５ A sample was obtained in the same manner as in Example 1, except that an aqueous solution was formed by adding and rapidly stirring.

[0053] [Results of Example 9] Figure 14 shows the XRD pattern of the sample obtained in Example 9. １０GeP ２ S １２ It was found that Li-type crystals were obtained as the main phase. ３ P.O. ４ The following pattern was observed. Figure 15 shows the Raman spectrum of the sample obtained in Example 9. PS ４ ３- and GeS ４ ４- A band that can be assigned to the sample obtained in Example 9 was observed. ３１ 17 shows the temperature dependence of the ionic conductivity of the room temperature compact of the sample obtained in Example 9. The room temperature compact had an ionic conductivity of 1.7 × 10 at 25 °C. -３ SCM -１ Ionic conductivity of 26 kJ mol -１ By using basic conditions, the activation energy of the sample prepared using only water (1.6 × 10 -３ SCM -１ , 29 kJmol -１ ) had the advantage of lowering the activation energy and increasing the conductivity at low temperatures.

[0054] [Supplementary information from the results of Examples 1 to 5] The heat treatment time and temperature were １０ GeP ２ S １２ The crystallinity of the crystalline phase is affected, and higher crystallinity tends to result in higher electrical conductivity. From the viewpoints of productivity and environmental impact, a shorter heat treatment time is preferable, and from the viewpoint of performance, higher ionic conductivity is preferable. The heat treatment time and temperature can be controlled depending on the purpose.

[0055] Example 10: Li １０ SnP ２ S １２ Synthesis of Li ２ S: Mitsuwa Chemicals, 99.9%, P ２ S ５ : Sigma-Aldrich, 99%, Sn: Nilaco, 99.999%, S: Sigma-Aldrich, 99.998% were used as starting materials, and Li ２After weighing 2 g of S, Sn, and S, 20 g of ion-exchanged water was added and stirred at 80°C for 24 hours to obtain Li. ２ S-SnS ２ The resulting aqueous solution was added with P ２ S ５ The precursor solution was obtained by adding Li and stirring at room temperature for 3 minutes. ２ S, Sn, S, P ２ S ５ The composition of the feed is Li １０ SnP ２ S １２ Li so that the stoichiometric ratio ２ S:Sn:S:P ２ S ５ The resulting aqueous precursor solution was dried under reduced pressure at 200°C for 3 hours, and then heat-treated at 600°C for 2 hours in a dry argon atmosphere to obtain a powder sample (Li １０ SnP ２ S １２ (HT 600°C) was obtained.

[0056] [Results of Example 10] The target crystalline phase, Li １０ GeP ２ S １２ Li having a structure similar to the crystalline phase １０ SnP ２ S １２ The diffraction pattern of Li １０ SnP ２ S １２ It was found that crystals were obtained as the main phase. ４ SnS ４ and Li ３ P.O. ４ The diffraction pattern of 345 cm was also confirmed. －１ and 418 cm －１ SnS with a peak near ４ ３－ and P.S. ４ ３－ The Raman band of 0.83 × 10 was mainly confirmed for all room temperature molded specimens at 25 °C. －３ SCM －１ and about 1 x 10 －３ SCM－１ It showed ionic conductivity of Li １０ SnP ２ S １２ We have demonstrated that this process is also useful for the synthesis of

Claims

1. A method for producing a sulfide, wherein the sulfide has Li, P, S, and M as main constituent elements, and M is at least one selected from Ge and Sn, and the production method includes: a first step of adding a Li source, an S source, and an M source to an aqueous solvent having an organic solvent amount of 50 wt % or less to obtain a first solution; ２ S ５ to obtain a second solution; and a third step of removing the aqueous solvent from the second solution and performing crystallization by heat treatment.

2. The method according to claim 1, wherein the amount of said organic solvent in said aqueous solvent is 25% by weight or less.

3. The method according to claim 1 or 2, wherein the amount of the organic solvent in the aqueous solvent is 5% by weight or less.

4. The method of any one of claims 1 to 3, comprising carrying out a reaction in the first solution by heat treatment at a temperature of 50°C or higher and 120°C or lower.

5. The reaction in the first solution produces GeS ４ ４－ ions or SnS ４ ４－ The method of claim 4, wherein ions are generated.

6. The M source is GeS ４ ４－ ions or SnS ４ ４－ The method according to any one of claims 1 to 5, wherein the structure does not contain ions.

7. The Ge source is GeS ２ The method of any one of claims 1 to 6, comprising:

8. The manufacturing method according to any one of claims 1 to 7, wherein the Sn source contains metallic tin.

9. The method of any one of claims 1 to 8, wherein the S source comprises elemental sulfur.

10. The method of any one of claims 1 to 9, wherein the sulfide has an LGPS-type crystal phase.

11. The manufacturing method according to any one of claims 1 to 10, wherein in the third step, the heat treatment is carried out at a temperature of 450°C or higher and 800°C or lower.

12. The sulfide is Li ３．０±０．２ P.S. ４．０±０．２ -Li ４．０±０．２ MS ４．０±０．２ The method according to any one of claims 1 to 11, wherein the compound can be represented by the formula:

13. The sulfide contains 0.1% by weight or more and 10% by weight or less of Li based on the sulfide. ３ P.O. ４ The method according to any one of claims 1 to 12, wherein the compound is a hydroxybenzoate.

14. The method of any one of claims 1 to 13, wherein the sulfide is an electrolyte for a solid-state battery.

15. A method for producing a solid-state battery, comprising a step of using the sulfide obtained by the production method according to any one of claims 1 to 14 as a component of an electrolyte layer, a positive electrode, or a negative electrode.

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