Method for manufacturing Sn-containing sulfide-based solid electrolyte

Abstract

According to the present invention, there is provided a method for manufacturing a sulfide-based solid electrolyte, which includes: a solution preparation step of preparing a homogeneous solution containing at least lithium (Li) element, tin (Sn) element, phosphorus (P) element, and sulfur (S) element in an organic solvent; a drying step of obtaining a precursor by removing the organic solvent from the homogeneous solution; and a heat treatment step of obtaining a sulfide-based solid electrolyte by subjecting the precursor to a heat treatment.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a Sn-containing sulfide-based solid electrolyte. Background Art

[0002] In recent years, in applications such as portable information terminals, portable electronic devices, electric vehicles, hybrid electric vehicles, and stationary energy storage systems, the demand for lithium-ion secondary batteries has been increasing. However, current lithium-ion secondary batteries use flammable organic solvents as electrolytes and require a strong outer package to prevent leakage of the organic solvents. In addition, in portable personal computers, etc., a structure to cope with the risk in case of electrolyte leakage is required, and there are also restrictions on the structure of the device.

[0003] Furthermore, as their applications expand to moving bodies such as automobiles and airplanes, a large capacity is required for stationary lithium-ion secondary batteries. In such a situation, safety is more emphasized than ever, and efforts are being made to develop all-solid-state lithium-ion secondary batteries that do not use harmful substances such as organic solvents.

[0004] For example, as solid electrolytes in all-solid-state lithium-ion secondary batteries, the use of oxides, phosphate compounds, organic polymers, sulfides, etc. has been investigated.

[0005] Among these solid electrolytes, sulfides have the characteristics of high ionic conductivity, being relatively soft, and easily forming an interface between solids. They are also stable to active materials, and the development as a practical solid electrolyte is being promoted.

[0006] In sulfide-based solid electrolytes, it is known that Sn-containing sulfide-based solid electrolytes can obtain good ionic conductivity and high water resistance, and there is high expectation for practical use (Non-Patent Document 1).

[0007] As a method for manufacturing a solid electrolyte, a method of reacting while crushing raw materials using a ball mill, a vibration mill, etc. is known. In addition, a method for synthesizing a solid electrolyte in a solvent has been recently developed (Patent Document 1). The synthesis productivity in the solvent is excellent and is highly expected.

[0008] In existing Sn-containing sulfide-based solid electrolytes, the raw material mostly uses Sn sulfide SnS 2 . However, SnS 2 has poor solubility in a solvent. Therefore, in the synthesis in a solvent, it is difficult to uniformly disperse Sn in the solid electrolyte during synthesis, and there is a technical problem that it is difficult to obtain a solid electrolyte showing stable performance.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-169459

[0012] Non-Patent Document

[0013] Non-Patent Document 1: J. Am. Chem. Soc. 2013, 135, 15694 - 15697 Summary of the Invention

[0014] Technical Problem to be Solved by the Invention

[0015] Under such circumstances, it is desired to provide a method for manufacturing a sulfide-based solid electrolyte with excellent productivity, few impurities, and stable performance.

[0016] Technical Solution for Solving the Technical Problem

[0017] For this reason, the inventors of the present invention conducted in-depth research in view of the above technical problems and unexpectedly found that: by preparing a Li - Sn - S homogeneous solution containing at least lithium (Li) element, tin (Sn) element, and sulfur (S) element in an organic solvent and using it as a raw material, a stable sulfide-based solid electrolyte with few impurities can be manufactured.

[0018] That is, the present invention relates to the following.

[0019] <1> A method for manufacturing a sulfide-based solid electrolyte, comprising: a solution preparation step of preparing a homogeneous solution containing at least lithium (Li) element, tin (Sn) element, phosphorus (P) element, and sulfur (S) element in an organic solvent; a drying step of obtaining a precursor by removing the organic solvent from the homogeneous solution; and a heat treatment step of obtaining a sulfide-based solid electrolyte by heat-treating the precursor.

[0020] <2> The method for manufacturing a sulfide-based solid electrolyte according to <1> above, wherein the solution preparation step includes: by mixing Li 2 S and P 2 S 5 in the organic solvent to prepare a Li - P - S homogeneous solution in a first solution preparation step; and a second solution preparation step of preparing a Li - Sn - S homogeneous solution containing at least lithium (Li) element, tin (Sn) element, and sulfur (S) element in the organic solvent,

[0021] including a step of mixing the Li - P - S homogeneous solution and the Li - Sn - S homogeneous solution to prepare a homogeneous solution.

[0022] <3> The method for manufacturing a sulfide-based solid electrolyte according to <1> above, wherein the solution preparation step includes: by mixing Li 2 S and P 2 S5 Mix in the above-mentioned organic solvent to prepare Solution Preparation Step 1 of a homogeneous Li-P-S solution; prepare Solution Preparation Step 2 of a homogeneous Li-Sn-S solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in the above-mentioned organic solvent; and by mixing Li 2 S and S in the above-mentioned organic solvent to prepare Solution Preparation Step 3 of a homogeneous Li-S solution.

[0023] It includes the step of mixing the above-mentioned Li-P-S homogeneous solution, the above-mentioned Li-Sn-S homogeneous solution, and the above-mentioned Li-S homogeneous solution to prepare a homogeneous solution.

[0024] <4> The method for manufacturing a sulfide-based solid electrolyte as described in <1> above, wherein the above-mentioned solution preparation step includes: by mixing Li 2 S and P 2 S 5 Mix in the above-mentioned organic solvent to prepare Solution Preparation Step 1 of a homogeneous Li-P-S solution; prepare Solution Preparation Step 2 of a homogeneous Li-Sn-S solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in the above-mentioned organic solvent; by mixing Li 2 S and S in the above-mentioned organic solvent to prepare Solution Preparation Step 3 of a homogeneous Li-S solution; and prepare Solution Preparation Step 4 of a homogeneous Li-Si-S solution containing at least lithium (Li), silicon (Si), and sulfur (S) elements in the above-mentioned organic solvent.

[0025] It includes the step of mixing the above-mentioned Li-P-S homogeneous solution, the above-mentioned Li-Sn-S homogeneous solution, the above-mentioned Li-S homogeneous solution, and the above-mentioned Li-Si-S homogeneous solution to prepare a homogeneous solution.

[0026] <5> The method for manufacturing a sulfide-based solid electrolyte as described in any one of <2> to <4> above, wherein the above-mentioned solution preparation step 2 includes mixing Li 2 S, SnS, and S in the above-mentioned organic solvent to prepare a homogeneous Li-Sn-S solution.

[0027] <6> The method for manufacturing a sulfide-based solid electrolyte as described in <4> above, wherein the above-mentioned solution preparation step 4 includes mixing Li 2 S, SiS 2 and S in the above-mentioned organic solvent to prepare a homogeneous Li-Si-S solution.

[0028] <7> A method for manufacturing a sulfide-based solid electrolyte, characterized by including: preparing a composition containing Li 3 PS 4Slurry chemical process 1 of the slurry; Solution chemical process of preparing a homogeneous Li-Sn-S solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in an organic solvent; Mixing the above slurry containing Li 3 PS 4 with the above Li-Sn-S homogeneous solution to prepare a mixed slurry in slurry chemical process 2; Drying process of removing the above organic solvent from the above mixed slurry to obtain a precursor; and Heat treatment process of obtaining a sulfide-based solid electrolyte by heat-treating the above precursor.

[0029] <8> The method for manufacturing a sulfide-based solid electrolyte as described in <7> above, wherein the above solution chemical process includes adding Li 2 S, SnS, and S to the above organic solvent and mixing them to prepare a homogeneous Li-Sn-S solution.

[0030] <9> The method for manufacturing a sulfide-based solid electrolyte as described in any one of <1> to <8> above, wherein the above organic solvent is at least one selected from ether-based solvents, nitrile-based solvents, and ester-based solvents.

[0031] <10> The method for manufacturing a sulfide-based solid electrolyte as described in any one of <1> to <9> above, wherein the above organic solvent is at least one selected from tetrahydrofuran, acetonitrile, ethyl acetate, and methyl acetate.

[0032] <11> The method for manufacturing a sulfide-based solid electrolyte as described in any one of <1> to <10> above, wherein the temperature in the above drying process is 60 to 280 °C.

[0033] <12> The method for manufacturing a sulfide-based solid electrolyte as described in any one of <1> to <11> above, wherein the temperature in the above heat treatment process is 200 °C to 700 °C.

[0034] <13> The method for manufacturing a sulfide-based solid electrolyte as described in any one of <1> to <12> above, wherein the above sulfide-based solid electrolyte contains an LGPS-based solid electrolyte, and in X-ray diffraction has peaks at least at positions of 2θ = 19.90° ± 0.50°, 20.20° ± 0.50°, 26.70° ± 0.50°, and 29.20° ± 0.50°.

[0035] Effects of the invention

[0036] According to the present invention, a method for manufacturing a sulfide-based solid electrolyte with excellent productivity, few impurities, and stable performance can be provided. In particular, compared with using insoluble raw material SnS 2In contrast to the BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram showing the crystal structure of a sulfide-based solid electrolyte according to an embodiment of the present invention.

[0038] Figure 2 is a schematic cross-sectional view of an all-solid-state battery according to an embodiment of the present invention.

[0039] Figure 3 is a graph showing the results of X-ray diffraction measurements of the sulfide-based solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 2. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in detail below. In addition, the materials, configurations, etc. described below do not limit the present invention, and various modifications can be made within the scope of the gist of the present invention.

[0041] A first embodiment of the present invention relates to a method for manufacturing a sulfide-based solid electrolyte, which is characterized by including: a solution preparation step of preparing a homogeneous solution containing at least lithium (Li), tin (Sn), phosphorus (P), and sulfur (S) elements in an organic solvent; a drying step of obtaining a precursor by removing the organic solvent from the homogeneous solution; and a heat treatment step of obtaining a sulfide-based solid electrolyte by heat-treating the precursor.

[0042] In the present invention, a homogeneous solution containing at least lithium (Li), tin (Sn), phosphorus (P), and sulfur (S) elements in an organic solvent is defined as a solution containing at least lithium (Li), tin (Sn), phosphorus (P), and sulfur (S) elements in an organic solvent and having no undissolved precipitate.

[0043] In a first embodiment of the present invention, preferably, the solution preparation step includes: by mixing Li 2 S and P 2 S 5 in the organic solvent to prepare a solution preparation step 1 of a Li-P-S homogeneous solution; and a solution preparation step 2 of preparing a Li-Sn-S homogeneous solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in the organic solvent, and including a step of mixing the Li-P-S homogeneous solution and the Li-Sn-S homogeneous solution to prepare a homogeneous solution.

[0044] In addition, in the first embodiment of the present invention, preferably, in addition to the above solution preparation steps 1 and 2, the solution preparation step further includes a solution preparation step 3 of preparing a homogeneous Li-S solution by mixing Li 2 S and S in the above organic solvent, and includes a step of mixing the above Li-P-S homogeneous solution, the above Li-Sn-S homogeneous solution, and the above Li-S homogeneous solution to prepare a homogeneous solution.

[0045] Furthermore, in the first embodiment of the present invention, preferably, in addition to the above solution preparation steps 1 to 3, the solution preparation step further includes a solution preparation step 4 of preparing a Li-Si-S homogeneous solution in which at least lithium (Li) element, silicon (Si) element, and sulfur (S) element are contained in the above organic solvent, and includes a step of mixing the above Li-P-S homogeneous solution, the above Li-Sn-S homogeneous solution, the above Li-S homogeneous solution, and the above Li-Si-S homogeneous solution to prepare a homogeneous solution.

[0046] The solution preparation steps 1 to 4, the drying step, and the heat treatment step will be described in detail below.

[0047] In the present invention, the so-called "Li-P-S homogeneous solution" is defined as a solution in which at least lithium (Li) element, phosphorus (P) element, and sulfur (S) element are contained in an organic solvent and there is no undissolved precipitate. Similarly, the so-called "Li-Sn-S homogeneous solution" is defined as a solution in which at least lithium (Li) element, tin (Sn) element, and sulfur (S) element are contained in an organic solvent and there is no undissolved precipitate. In addition, the so-called "Li-S homogeneous solution" is defined as a solution in which at least lithium (Li) element and sulfur (S) element are contained in an organic solvent and there is no undissolved precipitate. Furthermore, the so-called "Li-Si-S homogeneous solution" is defined as a solution in which at least lithium (Li) element, silicon (Si) element, and sulfur (S) element are contained in an organic solvent and there is no undissolved precipitate.

[0048] <Solution Preparation Step 1>

[0049] Solution preparation step 1 is a step of preparing a Li-P-S homogeneous solution by mixing Li 2 S and P 2 S 5 in an organic solvent. Preferably, Li 2 S and P 2 S 5 are mixed in an organic solvent at a molar ratio of Li 2 S / P 2 S 5 = 0.7 to 1.5 to prepare a Li-P-S homogeneous solution.

[0050] When mixing in Solution Chemical Process 1, it is in a slurry state for matrix dispersion, but the reaction occurs quickly. No special stirring operation for crushing particles is required, and it is sufficient to provide stirring power enough to suspend and disperse the slurry.

[0051] Regarding the reaction temperature in Solution Chemical Process 1, although the reaction can proceed slowly at room temperature, heating can also be carried out to increase the reaction rate. When heating is carried out, it is sufficient to carry out below the boiling point of the organic solvent. Although it varies depending on the organic solvent used, it is usually below 120 °C. Although an autoclave or the like can also be used to carry out the reaction under pressure, if mixing is carried out at a high temperature above 120 °C, side reactions may occur.

[0052] As the reaction time in Solution Chemical Process 1, although it varies depending on the type of organic solvent, the particle size of the raw material, and the concentration, the reaction can be completed and made into a solution by carrying out, for example, 0.1 to 24 hours.

[0053] The Li-P-S homogeneous solution is preferably generated by mixing and reacting Li 2 S and P 2 S 5 in an organic solvent at a molar ratio of Li 2 S / P 2 S 5 = 0.7 to 1.5, and more preferably Li 2 S / P 2 S 5 = 0.75 to 1.4, and particularly preferably Li 2 S / P 2 S 5 = 0.8 to 1.35. When in the range of the molar ratio of Li 2 S / P 2 S 5 = 0.7 to 1.5, Li 2 S and P 2 S 5 can be made into a solution at room temperature. When outside the range of the above molar ratio, precipitation may occur.

[0054] In this solution, unreacted Li 2 S, P 2 S 5 can also be contained. In addition, impurities mixed in by Li 2 S, P 2 S 5 can also be contained. Since the impurities are hardly soluble in the solvent and most of them will precipitate, it is preferable to filter and centrifuge the obtained solution to remove the precipitate and separate the solution, thereby obtaining a high-purity Li-P-S homogeneous solution.

[0055] Li2 S can be a synthetic product or a commercially available product. Since the incorporation of moisture deteriorates other raw materials and precursors, it is preferably low in moisture, more preferably 300 ppm or less, and particularly preferably 50 ppm or less. Li 2 When the particle size of S is small, the reaction rate becomes fast, which is thus preferred. As the diameter of the particles, the range of 10 nm to 100 μm is preferred, more preferably 100 nm to 30 μm, and particularly preferably 300 nm to 10 μm. The particle size can be measured by using SEM, a particle size distribution measuring device using laser scattering, etc. In addition, the Li 2 S used in Solution Chemical Processes 2 to 4 described later can also preferably be the same Li 2 S.

[0056] P 2 S 5 can be a synthetic product or a commercially available product. P 2 S 5 When the purity of S is high, the impurities mixed into the solid electrolyte become less, which is thus preferred. P 2 S 5 When the particle size of S is small, the reaction rate becomes fast, which is thus preferred. As the diameter of the particles, the range of 10 nm to 100 μm is preferred, more preferably 100 nm to 30 μm, and particularly preferably 300 nm to 10 μm. Since the incorporation of moisture deteriorates other raw materials and precursors, it is preferably low, more preferably 300 ppm or less, and particularly preferably 50 ppm or less.

[0057] The organic solvent is not particularly limited as long as it does not react with Li 2 S and P 2 S 5 For example, ether solvents, ester solvents, hydrocarbon solvents, nitrile solvents, etc. can be listed. Specifically, tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether, diethyl ether, dimethyl ether, dioxane, methyl acetate, ethyl acetate, butyl acetate, acetonitrile, etc. can be listed. Among them, at least one selected from tetrahydrofuran, acetonitrile, ethyl acetate, and methyl acetate is preferred, and acetonitrile is particularly preferred. Since the structure of acetonitrile does not contain an oxygen atom, it is not easy to introduce oxygen into the raw material composition, and deterioration can be suppressed. In addition, in order to prevent the deterioration of the raw material composition, it is preferred to remove oxygen and water, especially moisture, in the organic solvent in advance, preferably 100 ppm or less, and more preferably 50 ppm or less. In addition, the organic solvent used in Solution Chemical Processes 2 to 4 described later can also preferably be the same organic solvent as above.

[0058] <Solution Chemical Process 2>

[0059] Solution chemical process 2 is a process for preparing a homogeneous Li-Sn-S solution in which an organic solvent contains at least lithium (Li), tin (Sn), and sulfur (S) elements. Preferably, in solution chemical process 2, by using Li 2 S, SnS, and S (elemental sulfur) are mixed in an organic solvent to prepare a homogeneous Li-Sn-S solution.

[0060] Most of the existing Sn-containing sulfide-based solid electrolytes use tin sulfide SnS 2 as a raw material. However, SnS 2 has poor solubility in solvents. Therefore, in the synthesis in a solvent, it is difficult to uniformly disperse Sn in the solid electrolyte during synthesis, and there is a technical problem that it is difficult to obtain a solid electrolyte showing stable performance. The inventors of the present invention found that: by using a combination of Li 2 S, SnS, and S, a homogeneous Li-Sn-S solution in which they are dissolved in an organic solvent can be prepared.

[0061] Solution chemical process 2 more preferably uses Li 2 S, SnS, and S in a molar ratio of Li 2 S﹕SnS﹕S = 2﹕1﹕12 to 6﹕1﹕36, and particularly preferably uses Li 2 S, SnS, and S in a molar ratio of Li 2 S﹕SnS﹕S = 3﹕1﹕18 to 5﹕1﹕30 and mixes them in an organic solvent to prepare a homogeneous Li-Sn-S solution.

[0062] During mixing in solution chemical process 2, it is in a slurry state dispersed as a matrix, but reacts quickly. No special stirring operation for crushing particles is required, and it is sufficient to provide stirring power sufficient to suspend and disperse the slurry.

[0063] Regarding the reaction temperature in solution chemical process 2, it is sufficient to carry out the reaction below the boiling point of the organic solvent. Although it varies depending on the organic solvent used, it is usually below 120 °C. The preferred reaction temperature is 50 to 100 °C, and more preferably 60 to 90 °C. Although it can also be carried out under pressure using an autoclave or the like, side reactions may occur when mixing at a high temperature above 120 °C.

[0064] As the reaction time in solution chemical process 2, although it varies depending on the type of organic solvent, the particle size of the raw materials, and the concentration, the reaction can be completed and made into a solution by carrying out, for example, 0.1 to 24 hours.

[0065] In this solution, unreacted Li 2 S, SnS, and S may also be contained. In addition, it may also contain Li 2S, SnS, and impurities mixed in S. Since the impurities are hardly soluble in the solvent and most of them will precipitate, it is preferred to remove the precipitate by filtering and centrifuging the obtained solution, and separate the solution, thereby obtaining a highly pure and homogeneous solution of Li-Sn-S.

[0066] The concentrations of the elements in the obtained homogeneous solution are analyzed by ICP, and the molar ratio is preferably Li﹕Sn﹕S = 4﹕1﹕15 to 12﹕1﹕43, more preferably Li﹕Sn﹕S = 5﹕1﹕18 to 11﹕1﹕40, and particularly preferably Li﹕Sn﹕S = 6﹕1﹕22 to 10﹕1﹕36.

[0067] Synthetic or commercially available SnS can be used. When the purity of SnS is high, the impurities mixed into the solid electrolyte are less, so it is preferred. When the particle size of SnS is small, the reaction rate becomes faster, so it is preferred. As the diameter of the particles, the range of 10 nm to 100 μm is preferred, more preferably 100 nm to 30 μm, and particularly preferably 300 nm to 10 μm. The particle size can be measured by using SEM measurement, a particle size distribution measuring device using laser scattering, etc. In addition, even if a part of the above raw materials is amorphous, it can be used without problems. Since the mixing of moisture deteriorates other raw materials and precursors, it is preferably low, more preferably 300 ppm or less, and particularly preferably 50 ppm or less.

[0068] Synthetic or commercially available elemental sulfur can be used. Usually, cyclic S8 sulfur is used. Since the mixing of moisture deteriorates other raw materials and precursors, it is preferred that the moisture is low, more preferably 300 ppm or less, and particularly preferably 50 ppm or less. When the particle size of elemental sulfur is small, the reaction rate becomes faster, so it is preferred. As the diameter of the particles, the range of 10 nm to 100 μm is preferred, more preferably 100 nm to 30 μm, and particularly preferably 300 nm to 10 μm. In addition, the S (elemental sulfur) used in Solution Chemical Process 3 and 4 described later can also preferably use the same substance as above.

[0069] <Solution Chemical Process 3>

[0070] Solution Chemical Process 3 is a process of preparing a Li-S homogeneous solution by mixing Li 2 S and S (elemental sulfur) in an organic solvent.

[0071] Solution Chemical Process 3 preferably mixes Li 2 S and S with a molar ratio of Li 2 S﹕S = 1﹕4 to 1﹕10, and more preferably mixes Li 2 S and S with a molar ratio of Li 2S: An Li-S homogeneous solution is prepared by mixing in an organic solvent at a molar ratio of S:S = 1:5 to 1:8.

[0072] During the mixing in Solution Chemical Process 3, it is in a slurry state with the matrix dispersed, but the reaction occurs quickly. No special stirring operation for crushing particles is required. It is sufficient to provide a stirring power sufficient to suspend and disperse the slurry.

[0073] Regarding the reaction temperature in Solution Chemical Process 3, it is sufficient to carry out the reaction below the boiling point of the organic solvent. Although it varies depending on the organic solvent used, it is usually below 120 °C. The preferred reaction temperature is 50 - 100 °C, and more preferably 60 - 90 °C. Although it is also possible to carry out the reaction under pressure using an autoclave or the like, side reactions may occur when mixing at a high temperature above 120 °C.

[0074] As the reaction time in Solution Chemical Process 3, it varies depending on the type of organic solvent, the particle size of the raw materials, and the concentration. By carrying out the reaction for, for example, 0.1 - 24 hours, the reaction can be completed and the solution can be formed.

[0075] In this solution, unreacted Li 2 S, S may also be contained. In addition, impurities mixed in by Li 2 S, S may also be contained. Since the impurities are hardly soluble in the solvent and most of them will precipitate, it is preferred to remove the precipitate by filtering or centrifuging the obtained solution and separate the solution to obtain a high-purity Li-S homogeneous solution.

[0076] <Solution Chemical Process 4>

[0077] Solution Chemical Process 4 is a process for preparing an Li-Si-S homogeneous solution containing at least lithium (Li) element, silicon (Si) element, and sulfur (S) element in an organic solvent. By using the Li-Si-S homogeneous solution, a sulfide-based solid electrolyte with few impurities and high ionic conductivity can be stably obtained. When using SiS 2 as the starting material, it is difficult to uniformly disperse Si in the solid electrolyte during synthesis. In addition, SiS 2 has a high reactivity with the atmosphere and thus contains oxygen-containing compounds, or often contains unreacted raw material Si, etc. It is difficult to prepare SiS 2 without impurities. Moreover, it is difficult to remove these impurities from SiS 2 .

[0078] On the other hand, the Li-Si-S homogeneous solution can easily uniformly disperse Si in the solid electrolyte during synthesis. After subsequent precipitation removal operations, impurities can be reduced, so side reactions are not likely to occur. Therefore, it is considered that a sulfide-based solid electrolyte with high ionic conductivity can be stably manufactured.

[0079] The Li-Si-S homogeneous solution is preferably prepared by mixing Li 2 S, SiS 2 and S (elemental sulfur) in an organic solvent and reacting them to form a solution in which Li, Si, and S are dissolved. In this solution, unreacted Li 2 S, SiS 2 , and S may also be contained. In addition, impurities mixed in by Li 2 S, SiS 2 , and S may also be contained.

[0080] More preferably, the obtained solution is filtered and centrifuged to remove the precipitate, and the solution is separated to obtain a homogeneous Li-Si-S solution. The concentrations of the respective elements in the obtained homogeneous solution are analyzed by ICP, and the molar ratio is preferably Li / Si = 0.6 to 2.0. Here, the above molar ratio is more preferably Li / Si = 0.7 to 1.6, and particularly preferably Li / Si = 0.8 to 1.4.

[0081] The removal of the precipitate can be carried out by filtration and centrifugation. When using a filter for filtration, the pore size of the filter is preferably 10 μm or less, more preferably 5 μm or less, and particularly preferably 2 μm or less.

[0082] What is obtained as the precipitate is unreacted Li 2 S, SiS 2 such raw materials, and impurities mixed in by SiS 2 . As impurities, Si, SiS 2 oxygen-containing compounds, SiO 2 , etc. can be cited.

[0083] SiS 2 can be a synthetic product or a commercially available product. When the purity of SiS 2 is high, the impurities mixed into the solid electrolyte become less, so it is preferred. When the particle size of SiS 2 is small, the reaction rate becomes fast, so it is preferred. As the diameter of the particles, the range of 10 nm to 100 μm is preferred, more preferably 100 nm to 30 μm, and particularly preferably 300 nm to 10 μm. The particle size can be measured by measurement using SEM, a particle size distribution measuring device using laser scattering, etc. In addition, even if a part of the above raw materials is amorphous, it can be used without problems. Since the mixing of moisture deteriorates other raw materials and precursors, it is preferably low, more preferably 300 ppm or less, and particularly preferably 50 ppm or less.

[0084] The total concentration of Li, Si and S in the organic solvent is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, and particularly preferably 2 to 10% by mass. When the total concentration of Li, Si and S in the organic solvent is higher than 20% by mass, it is difficult to form a homogeneous solution due to solid precipitation. On the other hand, when the total concentration of Li, Si and S in the organic solvent is lower than 0.5%, the load of solvent recovery increases due to the use of a large amount of organic solvent, and it becomes a factor that makes the reactor size too large.

[0085] <Preparation of homogeneous mixed solution>

[0086] In the first embodiment of the present invention, it is preferable to (i) mix the Li-P-S homogeneous solution obtained in solution chemical process 1 and the Li-Sn-S homogeneous solution obtained in solution chemical process 2, (ii) mix the Li-P-S homogeneous solution obtained in solution chemical process 1, the Li-Sn-S homogeneous solution obtained in solution chemical process 2 and the Li-S homogeneous solution obtained in solution chemical process 3, or (iii) mix the Li-P-S homogeneous solution obtained in solution chemical process 1, the Li-Sn-S homogeneous solution obtained in solution chemical process 2, the Li-S homogeneous solution obtained in solution chemical process 3 and the Li-Si-S homogeneous solution obtained in solution chemical process 4 to prepare a homogeneous mixed solution.

[0087] The concentration of the elements constituting the homogeneous mixed solution obtained by the above (i) is preferably in a molar ratio of Li﹕Sn﹕P = 8﹕1﹕1 to 15﹕1﹕4, more preferably Li﹕Sn﹕P = 10﹕1﹕2 to 13﹕1﹕3.

[0088] In addition, the concentration of the elements constituting the homogeneous mixed solution obtained by the above (ii) is preferably in a molar ratio of Li﹕Sn﹕P = 8﹕1﹕1 to 15﹕1﹕4, more preferably Li﹕Sn﹕P = 10﹕1﹕2 to 13﹕1﹕3.

[0089] In addition, the concentration of the elements constituting the homogeneous mixed solution obtained by the above (iii) is preferably in a molar ratio of Li﹕Sn﹕Si﹕P = 32﹕1﹕2﹕4 to 44﹕1﹕6﹕8, more preferably Li﹕Sn﹕Si﹕P = 35﹕1﹕3﹕5 to 41﹕1﹕5﹕7.

[0090] The type and concentration of the elements can be confirmed by, for example, an ICP emission analyzer. Since the performance of the sulfide-based solid electrolyte varies greatly depending on a slight deviation in the composition, it is preferable to accurately control the element composition by performing ICP emission analysis on the homogeneous solution.

[0091] In addition, a halogen compound can also be added thereto. At this time, the halogen compound is also preferably dissolved in an organic solvent. Specific examples of the halogen compound include LiCl, LiBr, LiI, PCl 5 、PCl 3 、PBr 5 and PBr 3 , and LiCl, LiBr and LiI are more preferred. They can be used individually or in combination of two or more.

[0092] <Drying process>

[0093] The drying process is a process of removing the organic solvent by drying the obtained homogeneous solution to obtain a precursor. Drying is preferably heat drying or vacuum drying in an inert gas atmosphere.

[0094] The drying temperature is preferably in the range of 60 to 280°C, more preferably 100 to 250°C. Although the optimal range varies slightly depending on the type of organic solvent, the temperature range is important. When the drying temperature is too high in the presence of the organic solvent, in most cases, the precursor deteriorates. In addition, when the drying temperature is too low, there are more residual solvents. If the subsequent heat treatment process is carried out directly, the organic solvent will carbonize, and the conductivity of the obtained sulfide-based solid electrolyte will become high. Depending on the use method of the solid electrolyte, conductivity is sometimes preferred, but Figure 2 the solid electrolyte used in the "2" part requires a sufficiently low conductivity. In the case of using it for such purposes, it is necessary to make the residual solvent as little as possible.

[0095] The drying time varies slightly depending on the type of organic solvent and the drying temperature, but by implementing for 1 to 24 hours, the organic solvent can be sufficiently removed. In addition, by removing the organic solvent under reduced pressure like vacuum drying, or by flowing an inert gas such as nitrogen or argon with sufficiently little moisture, the temperature for removing the organic solvent can be reduced, and the required time can be shortened.

[0096] In addition, the subsequent heat treatment process and the drying process can also be carried out simultaneously.

[0097] <Heat treatment process>

[0098] The heat treatment process is a process of obtaining a sulfide-based solid electrolyte by heat-treating the precursor obtained in the drying process.

[0099] The heat treatment temperature is generally preferably in the range of 200 to 700°C, more preferably in the range of 350 to 650°C, and particularly preferably in the range of 400 to 600°C. When the temperature is lower than the above range, it is difficult to form the desired crystal. On the other hand, when the temperature is higher than the above range, crystals other than the target may sometimes be formed.

[0100] The heating time varies slightly depending on the relationship with the heating temperature, but it is generally possible to achieve sufficient crystallization within the range of 0.1 to 24 hours. When heating at a high temperature for a long time beyond the above range, there is a concern about the deterioration of the sulfide-based solid electrolyte, so it is not preferred.

[0101] Heating can be carried out in a vacuum or an inert gas atmosphere, preferably in an inert gas atmosphere. As the inert gas, nitrogen, helium, argon, etc. can be used, and argon is preferred. It is preferably low in oxygen and moisture, and the conditions are the same as those during the mixing in the slurry chemical process.

[0102] The second embodiment of the present invention relates to a method for manufacturing a sulfide-based solid electrolyte, which is characterized by including: a slurry chemical process 1 for preparing a slurry containing Li 3 PS 4 ; a solution chemical process for preparing a homogeneous Li-Sn-S solution containing at least lithium (Li) element, tin (Sn) element, and sulfur (S) element in an organic solvent; a slurry chemical process 2 for mixing the above slurry containing Li 3 PS 4 and the above homogeneous Li-Sn-S solution to prepare a mixed slurry; a drying process for obtaining a precursor by removing the above organic solvent from the above mixed slurry; and a heat treatment process for obtaining a sulfide-based solid electrolyte by performing a heat treatment on the above precursor.

[0103] In the slurry chemical process 1 of the second embodiment, as long as a slurry containing Li 3 PS 4 can be prepared, there is no particular limitation. Preferably, Li 2 S and P 2 S 5 are mixed in an organic solvent in a molar ratio of Li 2 S / P 2 S 5 = 2 to 4 to prepare a slurry containing Li 3 PS 4 .

[0104] The other processes in the second embodiment can be carried out according to the processes described in the first embodiment.

[0105] The LGPS-type crystal structure has an octahedron O composed of Li element and S element, a tetrahedron T1 composed of one or more elements selected from P, Ge, Si, and Sn and S element, and a tetrahedron T2 composed of P element and S element (PS 4 3-(anions), and a crystal structure in which the tetrahedron T1 and the octahedron O share an edge, and the tetrahedron T2 and the octahedron O share a vertex. The solid electrolyte having the LGPS-type crystal structure has a particularly high ionic conductivity and is thus more preferred. When the Si-containing LGPS-based solid electrolyte comes into contact with water, hydrogen sulfide is easily formed, while Sn does not produce hydrogen sulfide even when in contact with water, having the advantages of high safety and easy manufacture.

[0106] The solid electrolyte having the LGPS-type crystal structure as a preferred embodiment of the present invention is preferably subjected to X-ray diffraction measurement and has peaks at least at positions of 2θ = 19.90° ± 0.50°, 20.20° ± 0.50°, 26.70° ± 0.50°, and 29.20° ± 0.50°.

[0107] The sulfide-based solid electrolyte of the present invention obtained as described above can be formed into a desired molded body by various means and used in various applications typified by the all-solid-state battery described below. The molding method is not particularly limited. For example, the same method as the molding method of each layer constituting the all-solid-state battery described in <All-Solid-State Battery> below can be used.

[0108] <All-Solid-State Battery>

[0109] The sulfide-based solid electrolyte of the present invention can be used as a solid electrolyte for an all-solid-state battery, for example. In addition, according to another embodiment of the present invention, an all-solid-state battery containing the above solid electrolyte for an all-solid-state battery is provided.

[0110] Here, the so-called "all-solid-state battery" refers to an all-solid-state lithium-ion secondary battery. Figure 2 is a schematic cross-sectional view of an all-solid-state battery according to an embodiment of the present invention. The all-solid-state battery 10 has a structure in which a solid electrolyte layer 2 is disposed between a positive electrode layer 1 and a negative electrode layer 3. The all-solid-state battery 10 can be used in various devices typified by mobile phones, personal computers, automobiles, etc.

[0111] The sulfide-based solid electrolyte of the present invention can be included as a solid electrolyte in any one or more of the positive electrode layer 1, the negative electrode layer 3, and the solid electrolyte layer 2. When the sulfide-based solid electrolyte of the present invention is contained in the positive electrode layer 1 or the negative electrode layer 3, the sulfide-based solid electrolyte of the present invention is used in combination with a known positive electrode active material or negative electrode active material for a lithium-ion secondary battery. The quantitative ratio of the sulfide-based solid electrolyte contained in the positive electrode layer 1 or the negative electrode layer 3 is not particularly limited.

[0112] The sulfide-based solid electrolyte of the present invention can be formed alone or can be used in appropriate combination with an oxide solid electrolyte as needed (for example, Li 7 La 3 Zr2 O 12 ) Sulfide-based solid electrolytes (e.g., Li 2 S-P 2 S 5 ), and other complex hydride solid electrolytes (e.g., LiBH 4 , 3LiBH 4 -LiI), etc.

[0113] The all-solid-state battery is manufactured by forming and laminating the above-described layers, but the forming method and the laminating method of each layer are not particularly limited.

[0114] For example, there are: a method of forming a film by dispersing a solid electrolyte and / or an electrode active material in a solvent to form a slurry, coating it by a doctor blade or spin coating, and calendering it; a vapor phase method of forming and laminating a film by a vacuum evaporation method, an ion plating method, a sputtering method, a laser ablation method, etc.; a pressure molding method of forming a powder by hot pressing or cold pressing without heating and laminating it.

[0115] Since the sulfide-based solid electrolyte of the present invention is relatively soft, it is particularly preferable to manufacture the all-solid-state battery by forming and laminating each layer by a pressure molding method. As the pressure molding method, there are a hot pressing method performed by heating and a cold pressing method without heating, and molding can be sufficiently performed by cold pressing.

[0116] In addition, the present invention includes a molded body obtained by heat-forming the sulfide-based solid electrolyte of the present invention. This molded body can be suitably used as an all-solid-state battery. Further, the present invention includes a method for manufacturing an all-solid-state battery, which includes a step of heat-forming the sulfide-based solid electrolyte of the present invention.

[0117] Examples

[0118] Hereinafter, the present embodiment will be described in more detail by way of examples, but the present embodiment is not limited to these examples.

[0119] (Example 1)

[0120] <Solution preparation step 1>

[0121] In a glove box under an argon atmosphere, Li 2 S﹕P 2 S 5 was measured in a molar ratio of 1﹕1, 101 mg of Li 2 S (manufactured by Sigma Aldrich, purity 99.8%) and 487 mg of P 2 S 5 (manufactured by Sigma Aldrich, purity 99%). Then, for 6.0 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade), Li was successively added.2 S and P 2 S 5 , so that the concentration of (Li 2 S + P 2 S 5 ) is about 10% by mass, and they are mixed at room temperature for 3 hours. The mixture gradually dissolves to obtain a homogeneous Li-P-S solution.

[0122] <Solution Chemical Process 2>

[0123] In a glove box under an argon atmosphere, Li 2 S﹕SnS﹕S is measured in a molar ratio of 3﹕1﹕18, taking 1.0 g of Li 2 S (manufactured by SigmaAldrich, purity 99.8%), 1.0 g of SnS (manufactured by Kojundo Chemical Laboratory Co., Ltd.) and 3.7 g of S (manufactured by Kojundo Chemical Laboratory Co., Ltd.). Then, 100 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) is added so that the concentration of (Li 2 S + SnS + S) is about 6% by mass, and they are mixed at 80 °C for 24 hours. Although the mixture gradually dissolves, there are insoluble substances remaining at this stage.

[0124] The obtained solution is filtered through a membrane filter (PTFE, pore size 1.0 μm) to obtain 300 mg of filter residue and 100 g of filtrate (Li-Sn-S homogeneous solution). ICP analysis of the Li-Sn-S homogeneous solution shows that Li﹕Sn﹕S = 6﹕1﹕26 (molar ratio). In addition, the concentration of Sn is 0.76% by mass.

[0125] <Solution Chemical Process 3>

[0126] In a glove box under an argon atmosphere, Li 2 S﹕S is measured in a molar ratio of 1﹕6, taking 1.0 g of Li 2 S (manufactured by Sigma Aldrich, purity 99.8%) and 3.7 g of S (manufactured by Kojundo Chemical Laboratory Co., Ltd.). Then, 75 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) is added so that the concentration of (Li 2 S + S) is about 6% by mass, and they are mixed at 80 °C for 24 hours. Although the mixture gradually dissolves, there are insoluble substances remaining at this stage.

[0127] The obtained solution is filtered through a membrane filter (PTFE, pore size 1.0 μm) to obtain 200 mg of filter residue and 75 g of filtrate (Li-S homogeneous solution). ICP analysis of the Li-S homogeneous solution shows that Li﹕S = 1﹕3 (molar ratio). In addition, the concentration of Li is 0.5% by mass.

[0128] <Preparation of Homogeneous Mixed Solution>

[0129] Mix 6.6 g of the prepared Li-P-S homogeneous solution, 25.08 g of the Li-Sn-S homogeneous solution, and 7.97 g of the Li-S homogeneous solution in a molar ratio of Li:Sn:P = 12:1:3, and stir for 3 hours to prepare a homogeneous mixed solution.

[0130] <Drying process>

[0131] Dry the obtained homogeneous mixed solution under vacuum at 180 °C for 4 hours to remove the solvent. Remove the solvent while stirring the solution. Then, cool to room temperature to obtain a precursor.

[0132] <Heat treatment process>

[0133] Place the obtained precursor in a glass reaction tube inside a glove box, and set the precursor in an electric tube furnace without exposure to the atmosphere. Blow argon (Grade G3) into the reaction tube, heat it to 550 °C over 3 hours, and then calcine it at 550 °C for 8 hours to synthesize Li 9.81 Sn 0.81 P 2.19 S 12 crystals.

[0134] (Example 2)

[0135] <Solution chemical process 1>

[0136] Perform the same operations as in Example 1 to obtain a Li-P-S homogeneous solution.

[0137] <Solution chemical process 2>

[0138] Inside a glove box under an argon atmosphere, measure Li 2 S:SnS:S in a molar ratio of 4.5:1:24 to obtain 1.25 g of Li 2 S (manufactured by SigmaAldrich, purity 99.8%), 1 g of SnS (manufactured by Kojundo Chemical Laboratory Co., Ltd.), and 5 g of S (manufactured by Kojundo Chemical Laboratory Co., Ltd.). Then, add 100 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) to make the concentration of (Li 2 S + SnS + S) approximately 7% by mass, and mix at 80 °C for 24 hours. Although the mixture gradually dissolves, there are insoluble residues at this stage.

[0139] Filter the obtained solution with a membrane filter (PTFE, pore size 1.0 μm) to obtain 300 mg of filter residue and 100 g of filtrate (Li-Sn-S homogeneous solution). Perform ICP analysis on the Li-Sn-S homogeneous solution, and the results are Li:Sn:S = 9:1:30 (molar ratio). In addition, the concentration of Sn is 0.89% by mass.

[0140] <Preparation of homogeneous mixed solution>

[0141] Mix 6.6 g of the prepared Li-P-S homogeneous solution and 33.28 g of the Li-Sn-S homogeneous solution in a molar ratio of Li:Sn:P = 12:1:3, and stir for 3 hours to prepare a homogeneous mixed solution.

[0142] <Drying process>

[0143] Perform the same operation as in Example 1 to obtain a precursor.

[0144] <Heat treatment process>

[0145] Perform the same operation as in Example 1 to synthesize Li 9.81 Sn 0.81 P 2.19 S 12 crystals.

[0146] (Comparative Example 1)

[0147] <Solution chemical process>

[0148] Perform the same operation as in Example 1 to obtain a Li-P-S homogeneous solution.

[0149] <Slurry chemical process>

[0150] Mix 6.6 g of the prepared Li-P-S homogeneous solution, 296 mg of powdered SnS 2 (manufactured by High Purity Chemical Co., Ltd.) and 350 mg of Li 2 S in a molar ratio of Li:Sn:P = 12:1:3, and stir for 3 hours to prepare a slurry solution. Here, Sn is not in a state of being completely dissolved in the organic solvent.

[0151] <Drying process>

[0152] Dry the obtained slurry solution under vacuum at 180 °C for 4 hours to remove the solvent. Remove the solvent while stirring the solution. Then, cool to room temperature to obtain a precursor.

[0153] <Heat treatment process>

[0154] Perform the same operation as in Example 1 to synthesize Li 9.81 Sn 0.81 P 2.19 S 12 crystals.

[0155] (Example 3)

[0156] <Solution chemical process 1>

[0157] Perform the same operations as in Example 1 to obtain a homogeneous Li-P-S solution.

[0158] <Solution Chemical Process 2>

[0159] Perform the same operations as in Example 1 to obtain a homogeneous Li-Sn-S solution.

[0160] <Solution Chemical Process 3>

[0161] Perform the same operations as in Example 1 to obtain a homogeneous Li-S solution.

[0162] <Solution Chemical Process 4>

[0163] In a glove box under an argon atmosphere, measure Li 2 S﹕SiS 2 ﹕S at a molar ratio of 0.5﹕1﹕0.4. Weigh 4.0 g of Li 2 S (manufactured by SigmaAldrich, purity 99.8%), 16.0 g of SiS 2 (manufactured by HANGZHOU), and 2.4 g of S (manufactured by Kojundo Chemical Laboratory Co., Ltd.). Then, add them to 610 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) so that the concentration of (Li 2 S+SiS 2 +S) becomes approximately 3.5% by mass, and mix at room temperature for 24 hours. Although the mixture gradually dissolves, impurities remain in the raw materials at this stage.

[0164] Filter the resulting solution through a membrane filter (PTFE, pore size 1.0 μm) to obtain 2.0 g of filter residue and 578 g of filtrate (Li-Si-S homogeneous solution). Perform ICP analysis on the Li-Si-S homogeneous solution. The result shows that the molar ratio of Li﹕Si﹕S is 1﹕1﹕3. In addition, the concentration of (Li 2 S+SiS 2 +S) is 3.43% by mass.

[0165] <Preparation of Homogeneous Mixed Solution>

[0166] Mix 6.6 g of the above-prepared Li-P-S homogeneous solution, 11.11 g of Li-Sn-S homogeneous solution, 13.48 g of Li-Si-S homogeneous solution, and 22.93 g of Li-S homogeneous solution in a molar ratio of Li﹕Sn﹕Si﹕P = 38﹕1﹕4﹕6, and stir for 3 hours to prepare a homogeneous mixed solution.

[0167] <Drying Process>

[0168] The resulting homogeneous mixed solution is dried at 180 °C for 4 hours under vacuum to remove the solvent. The solvent is removed while stirring the solution. Then, it is cooled to room temperature to obtain a precursor.

[0169] <Heating treatment process>

[0170] In the glove box, the obtained precursor is placed in a glass reaction tube, and the precursor is set in an electric tube furnace without being exposed to the atmosphere. Argon (Grade G3) is blown into the reaction tube, heated to 550 °C over 3 hours, and then fired at 550 °C for 8 hours to synthesize Li 10.35 Sn 0.27 Si 1.08 P 1.65 S 12 crystal.

[0171] (Comparative Example 2)

[0172] <Solution chemical process 1>

[0173] The same operation as in Example 1 is carried out to obtain a Li-P-S homogeneous solution.

[0174] <Solution chemical process 2>

[0175] The same operation as in Example 3 is carried out to obtain a Li-Si-S homogeneous solution.

[0176] <Slurry mixing process>

[0177] 6.6 g of the above-prepared Li-P-S homogeneous solution, 131 mg of SnS 2 powder, 13.48 g of the Li-Si-S homogeneous solution, and 461 mg of Li 2 S are mixed in a molar ratio of Li﹕Sn﹕Si﹕P = 38﹕1﹕4﹕6 and stirred for 3 hours to prepare a slurry solution. Here, Sn is not in a state of being completely dissolved in the organic solvent.

[0178] <Drying process>

[0179] The obtained slurry solution is dried at 180 °C for 4 hours under vacuum to remove the solvent. The solvent is removed while stirring the solution. Then, it is cooled to room temperature to obtain a precursor.

[0180] <Heating treatment process>

[0181] The same operation as in Example 3 is carried out to synthesize Li 10.35 Sn 0.27 Si 1.08 P 1.65 S 12 crystal.

[0182] (Example 4)

[0183] <Slurry Chemical Process 1>

[0184] In a glove box under an argon atmosphere, take Li 2 S﹕P 2 S 5 at a molar ratio of 2.4﹕1. Weigh 236 mg of Li 2 S (manufactured by SigmaAldrich, purity 99.8%) and 487 mg of P 2 S 5 (manufactured by Sigma Aldrich, purity 99%). Then, for 7.0 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade), add Li 2 S and P 2 S 5 in sequence to make the concentration of (Li 2 S + P 2 S 5 ) approximately 10% by mass, and mix at room temperature for 12 hours. A Li 3 PS 4 precipitate is formed to obtain a slurry containing Li 3 PS 4 .

[0185] <Solution Chemical Process>

[0186] Perform the same operations as in Example 1 to obtain a homogeneous Li-Sn-S solution.

[0187] <Slurry Chemical Process 2>

[0188] Mix 7.72 g of the slurry containing Li 3 PS 4 prepared above and 20.71 g of the homogeneous Li-Sn-S solution in a molar ratio of Li﹕Sn﹕P = 12﹕1﹕3, and stir for 3 hours to prepare a slurry mixed solution.

[0189] <Drying Process>

[0190] Dry the obtained slurry mixed solution under vacuum at 180 °C for 4 hours to remove the solvent. Remove the solvent while stirring the solution. Then, cool to room temperature to obtain a precursor.

[0191] <Heat Treatment Process>

[0192] Perform the same operations as in Example 1. Synthesize Li 9.81 Sn 0.81 P 2.19 S 12 crystals.

[0193] <X-ray Diffraction Measurement>

[0194] For the powders of the sulfide-based solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 2, X-ray diffraction measurements were carried out at room temperature (25 °C) under an Ar atmosphere using “X'Pert3 Powder” manufactured by PANalytical Co., ).

[0195] The results of the X-ray diffraction measurements of the sulfide-based solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Figure 3 .

[0196] As Figure 3 shown, in Examples 1 to 4 and Comparative Examples 1 to 2, diffraction peaks were observed at least at 2θ = 19.90° ± 0.50°, 20.20° ± 0.50°, 26.70° ± 0.50°, and 29.20° ± 0.50°. This pattern is consistent with Li 10 GeP 2 S 12 in the ICSD database, confirming the presence of a LGPS-type crystal structure.

[0197] In addition, more impurity peaks were confirmed in Comparative Example 1. It is considered that these are impurities confirmed because Sn was not uniformly dispersed in the solid electrolyte during synthesis due to the poor solubility of the raw material SnS 2 in the solvent.

[0198] <Lithium Ion Conductivity Measurement>

[0199] The sulfide-based solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were uniaxially molded (420 MPa) to obtain disks with a thickness of about 1 mm and a diameter of 10 mm. Using a full solid-state battery evaluation unit (manufactured by Takizawa Co., Ltd.), alternating current impedance measurements were carried out at room temperature (25 °C) using the four-terminal method with “SI1260 IMPEDANCE / GAIN-PHASE ANALYZER” manufactured by Solartron Co., and the lithium ion conductivity was calculated.

[0200] Specifically, the sample was placed in a thermostat set at 25 °C, and after keeping it warm for 30 minutes, the lithium ion conductivity was measured. The measurement frequency range was 0.1 Hz to 1 MHz, and the amplitude was 50 mV. The measurement results of the lithium ion conductivity are shown in Table 1 below.

[0201] [Table 1]

[0202]

[0203] Symbol Explanation

[0204] 1: Positive electrode layer; 2: Solid electrolyte layer; 3: Negative electrode layer; 10: All-solid-state battery.

Claims

1. A method for manufacturing a sulfide-based solid electrolyte, characterized in that, comprising: a solution preparation step of preparing a homogeneous solution containing at least lithium (Li), tin (Sn), phosphorus (P), and sulfur (S) elements in an organic solvent; a drying step of obtaining a precursor by removing the organic solvent from the homogeneous solution; and a heat treatment step of obtaining a sulfide-based solid electrolyte by heat-treating the precursor, The solution chemical process includes: by mixing Li 2 S and P 2 S 5 in the organic solvent to prepare a Li-P-S homogeneous solution in solution chemical process 1; and solution chemical process 2 for preparing a Li-Sn-S homogeneous solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in the organic solvent. the solution preparation step further includes a step of mixing the Li-P-S homogeneous solution and the Li-Sn-S homogeneous solution to prepare a homogeneous solution, The solution chemical process 2 includes the step of mixing Li 2 S, SnS, and S in the organic solvent to prepare a homogeneous Li-Sn-S solution. the drying temperature in the drying step is 60 to 280 °C, the heating temperature in the heat treatment step is 200 to 700 °C, the heating time in the heat treatment step is 0.1 to 24 hours.

2. A method for manufacturing a sulfide-based solid electrolyte, characterized in that, comprising: a solution preparation step of preparing a homogeneous solution containing at least lithium (Li), tin (Sn), phosphorus (P), and sulfur (S) elements in an organic solvent; a drying step of obtaining a precursor by removing the organic solvent from the homogeneous solution; and a heat treatment step of obtaining a sulfide-based solid electrolyte by heat-treating the precursor, The solution chemical process includes: by mixing Li 2 S and P 2 S 5 in the organic solvent, a solution chemical process 1 for preparing a homogeneous Li-P-S solution; a solution chemical process 2 for preparing a homogeneous Li-Sn-S solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in the organic solvent; and a solution chemical process 3 for preparing a homogeneous Li-S solution by mixing Li 2 S and S in the organic solvent, the solution preparation step further includes a step of mixing the Li-P-S homogeneous solution, the Li-Sn-S homogeneous solution, and the Li-S homogeneous solution to prepare a homogeneous solution, the drying temperature in the drying step is 60 to 280 °C, the heating temperature in the heat treatment step is 200 to 700 °C, the heating time in the heat treatment step is 0.1 to 24 hours.

3. A method for manufacturing a sulfide-based solid electrolyte, characterized in that, comprising: a solution preparation step of preparing a homogeneous solution containing at least lithium (Li), tin (Sn), phosphorus (P), and sulfur (S) elements in an organic solvent; a drying step of obtaining a precursor by removing the organic solvent from the homogeneous solution; and a heat treatment step of obtaining a sulfide-based solid electrolyte by heat-treating the precursor, The solution chemical process includes: by mixing Li 2 S and P 2 S 5 in the organic solvent, a solution chemical process 1 for preparing a Li-P-S homogeneous solution; a solution chemical process 2 for preparing a Li-Sn-S homogeneous solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in the organic solvent; a solution chemical process 3 for preparing a Li-S homogeneous solution by mixing Li 2 S and S in the organic solvent; and a solution chemical process 4 for preparing a Li-Si-S homogeneous solution containing at least lithium (Li), silicon (Si), and sulfur (S) elements in the organic solvent, the solution preparation step further includes a step of mixing the Li-P-S homogeneous solution, the Li-Sn-S homogeneous solution, the Li-S homogeneous solution, and the Li-Si-S homogeneous solution to prepare a homogeneous solution, the drying temperature in the drying step is 60 to 280 °C, the heating temperature in the heat treatment step is 200 to 700 °C, the heating time in the heat treatment step is 0.1 to 24 hours.

4. The method for manufacturing a sulfide-based solid electrolyte according to claim 2 or 3, characterized in that: The solution chemical process 2 includes the step of mixing Li 2 S, SnS, and S in the organic solvent to prepare a homogeneous Li-Sn-S solution.

5. The method for manufacturing a sulfide-based solid electrolyte according to claim 3, characterized in that: The solution chemical process 4 includes the step of mixing Li 2 S, SiS 2 and S in the organic solvent to prepare a homogeneous Li-Si-S solution.

6. A method for manufacturing a sulfide-based solid electrolyte, characterized in that, comprising: Prepare a slurry containing Li 3 PS 4 in the slurry chemical process 1 of the slurry; a solution preparation step of preparing a Li-Sn-S homogeneous solution containing at least lithium (Li), tin (Sn), and sulfur (S) elements in an organic solvent; Mix the slurry containing Li 3 PS 4 with the Li-Sn-S homogeneous solution to prepare the slurry for the slurry chemical process 2 of the mixed slurry; a drying step of removing the organic solvent from the mixed slurry to obtain a precursor; and A heat treatment step of obtaining a sulfide-based solid electrolyte by subjecting the precursor to heat treatment The drying temperature in the drying step is 60 to 280 °C The heating temperature in the heat treatment step is 200 to 700 °C The heating time in the heat treatment step is 0.1 to 24 hours 7. The method for manufacturing a sulfide-based solid electrolyte according to claim 6 Characterized in that The solution chemical process includes the step of adding Li 2 2S, SnS and S into the organic solvent and mixing them to prepare a homogeneous solution of Li-Sn-S.

8. The method for manufacturing a sulfide-based solid electrolyte according to any one of claims 1 to 3 and 6 Characterized in that The organic solvent is at least one selected from ether solvents, nitrile solvents, and ester solvents 9. The method for manufacturing a sulfide-based solid electrolyte according to any one of claims 1 to 3 and 6 Characterized in that The organic solvent is at least one selected from tetrahydrofuran, acetonitrile, ethyl acetate, and methyl acetate 10. The method for manufacturing a sulfide-based solid electrolyte according to any one of claims 1 to 3 and 6 Characterized in that The sulfide-based solid electrolyte contains an LGPS-based solid electrolyte. In the X-ray diffraction with CuKα: peaks are present at least at positions of 2θ = 19.90° ± 0.50°, 20.20° ± 0.50°, 26.70° ± 0.50°, and 29.20° ± 0.50°.

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