Manufacturing methods for solid electrolyte powder and all-solid-state batteries

Abstract

According to the present invention, a method for manufacturing solid electrolyte powder is provided, comprising: step (1), adding a poor solvent to a good solvent solution containing a solid electrolyte and a good solvent to prepare a mixed solution, wherein the solid electrolyte contains at least one of an alkali metal element and an alkaline earth metal element, an element Sn, and an element S; step (2), removing at least a portion of the good solvent from the mixed solution to precipitate solid electrolyte particles; and step (3), drying the solid electrolyte particles to obtain solid electrolyte powder; wherein the volume ratio of the poor solvent to the volume of the good solvent (volume of poor solvent / volume of good solvent) is 5 or more.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing solid electrolyte powder and a method for manufacturing an all-solid-state battery. [Previous Technology]

[0002] Non-aqueous electrolyte secondary batteries have been widely used in applications such as portable information terminals and portable electronic devices. The electrolyte used in non-aqueous electrolyte secondary batteries typically employs a flammable organic solvent. Therefore, non-aqueous electrolyte secondary batteries require a robust casing to prevent leakage of the organic solvent and usually have features to protect against the risk of electrolyte leakage, thus imposing limitations on the device structure.

[0003] Furthermore, in recent years, the applications of non-aqueous electrolyte secondary batteries have expanded to electric vehicles, hybrid electric vehicles, aircraft, and other mobile applications, as well as stationary energy storage systems, with a focus on high-capacity non-aqueous electrolyte secondary batteries. High-capacity non-aqueous electrolyte secondary batteries seek to offer enhanced safety.

[0004] Given this situation, non-aqueous electrolyte secondary batteries that use solid electrolytes that achieve high safety without flammable organic solvents have attracted attention.

[0005] Non-aqueous electrolyte secondary batteries that use solid electrolytes typically have a relatively higher interfacial resistance between the electrolyte layer and the electrode layer compared to batteries that use liquid electrolytes. Therefore, methods to reduce the interfacial resistance between the electrolyte layer and the electrode layer have been explored in the past.

[0006] For example, Patent Document 1 describes an invention of sulfide-based solid electrolyte microparticles with an average particle size of 0.1 to 10 μm, which contain sulfur, lithium and phosphorus as main components.

[0007] Patent document 1 describes that by micronizing solid electrolytes, it is expected that the electrolyte layer can be thinned or the interfacial resistance between the electrolyte layer and the electrode agent can be reduced.

[0008] Furthermore, Patent Document 1 describes a method for manufacturing the aforementioned sulfide-based solid electrolyte particles by multi-stage pulverization in a non-aqueous solvent, a method for single-stage pulverization in a non-aqueous solvent with added dispersant and stabilizer, and a method for dry pulverization of sulfide-based solid electrolyte particles using a jet mill.

[0009] Regarding solid electrolytes, sulfide-based solid electrolytes and oxide-based solid electrolytes are known. Among them, sulfide-based solid electrolytes containing tin (Sn) exhibit high ionic conductivity and high water resistance, and therefore have received particular attention in recent years. [Previous Art Documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2008-4459 [Summary of the Invention]

[0011] [The problem that the invention aims to solve]

[0012] The method described in Patent Document 1 can micronize sulfide-based solid electrolytes by pulverization. However, it has been found that sulfide-based solid electrolytes containing tin (Sn) sometimes decompose due to the energy required during pulverization. Therefore, a method for manufacturing micronized tin (Sn)-containing sulfide-based solid electrolytes is required. [Means for Solving the Problem]

[0013] The inventors conducted in-depth research to solve the above-mentioned problems. As a result, they discovered that the above-mentioned problems could be solved, and the present invention could be completed, by using a method that employs both good and bad solvents for sulfide-based solid electrolytes containing tin (Sn).

[0014] That is, the present invention includes, for example, the following states. [1] A method for manufacturing a solid electrolyte powder, comprising: step (1), adding a poor solvent to a good solvent solution containing a solid electrolyte and a good solvent to prepare a mixed solution, wherein the solid electrolyte contains at least one of an alkali metal element and an alkaline earth metal element, an element Sn, and an element S; step (2), removing at least a portion of the aforementioned good solvent from the aforementioned mixed solution to precipitate solid electrolyte particles; and step (3), drying the aforementioned solid electrolyte particles to obtain a solid electrolyte powder; wherein the volume ratio of the aforementioned poor solvent to the aforementioned good solvent (volume of poor solvent / volume of good solvent) is 5 or more. [2] The manufacturing method described in [1] above, wherein the aforementioned solid electrolyte contains at least one of an element lithium (Li) and an element sodium (Na). [3] The manufacturing method described in [1] or [2] above, wherein the aforementioned solid electrolyte is a solid electrolyte composed of an element Li, an element Sn, and an element S. [4] The manufacturing method described in any one of [1] to [3] above, wherein the aforementioned good solvent includes an alcohol solvent. [5] The manufacturing method described in any one of [1] to [4] above, wherein the aforementioned poor solvent includes at least one of a nitrile solvent and an ester solvent. [6] The manufacturing method described in any one of [1] to [5] above, wherein the average particle size of the solid electrolyte powder is 20 μm or less. [7] A method for manufacturing an all-solid-state battery includes the following steps: stacking a solid electrolyte layer, a positive electrode layer, and a negative electrode layer to form an all-solid-state battery, wherein the solid electrolyte layer is formed using solid electrolyte powder obtained by any one of [1] to [6] above. [Effects of the Invention]

[0015] According to the present invention, a method for manufacturing a micronized tin (Sn) sulfide-based solid electrolyte is provided. Thereby, the solid electrolyte layer formed using this solid electrolyte can reduce the interfacial resistance with the electrode layer.

Implementation Method

[0016] Hereinafter, the present invention will be described in detail. Furthermore, the embodiments described below are not intended to limit the present invention, and various changes can be made within the scope of the concept of the present invention.

[0017] <Method for Manufacturing Solid Electrolyte Powder> This invention relates to a method for manufacturing solid electrolyte powder, comprising: step (1), adding a poor solvent to a good solvent solution containing a solid electrolyte and a good solvent to prepare a mixed solution, wherein the solid electrolyte contains at least one of an alkali metal element and an alkaline earth metal element, an element Sn, and an element S; step (2), removing at least a portion of the aforementioned good solvent from the aforementioned mixed solution to precipitate solid electrolyte particles; and step (3), drying the aforementioned solid electrolyte particles to obtain solid electrolyte powder. At this time, the volume ratio of the aforementioned poor solvent to the aforementioned good solvent (volume of poor solvent / volume of good solvent) is 5 or more.

[0018] According to the present invention, a micronized tin (Sn)-containing sulfide-based solid electrolyte can be manufactured. Specifically, a tin (Sn)-containing sulfide-based solid electrolyte (hereinafter sometimes referred to as "solid electrolyte") is first dissolved in a good solvent to obtain a good solvent solution. Then, the aforementioned good solvent solution is added to a poor solvent to obtain a mixed solution (step (1)). At this time, the volume ratio of the poor solvent to the good solvent (volume of poor solvent / volume of good solvent) is 5 or more. Then, by removing at least a portion of the good solvent from the mixed solvent, the solvent ratio of the poor solvent contained in the mixed solvent is increased, and solid electrolyte particles are precipitated (step (2)). By drying the obtained solid electrolyte particles, solid electrolyte powder can be manufactured (step (3)). According to the method of the present invention, since no energy is imparted to the solid electrolyte due to pulverization, etc., the solid electrolyte will not decompose or will hardly decompose. Furthermore, since the obtained solid electrolyte powder is micronized, for example, the interfacial resistance between the solid electrolyte layer formed using the solid electrolyte powder and the electrode layer will be reduced. As a result, all-solid-state batteries with high energy density and high output can be manufactured. Furthermore, in this specification, "microparticle-sized" refers to particles or powders with an average particle size of 20 μm or less.

[0019] The following is a detailed explanation of each step.

[0020] [Step (1)] Step (1) is a step of preparing a mixed solution by adding a poor solvent to a good solvent solution containing a solid electrolyte and a good solvent, wherein the solid electrolyte contains at least one of an alkali metal element and an alkaline earth metal element, tin (Sn) element, and sulfur (S) element.

[0021] (Good Solvent Solution) The good solvent solution contains at least one of an alkali metal element and an alkaline earth metal element, Sn element, and S element, a solid electrolyte and a good solvent. Other suitable and known additives may also be added.

[0022] (Solid Electrolyte) The solid electrolyte contains at least one alkali metal element and an alkaline earth metal element, Sn element, and S element. That is, the aforementioned solid electrolyte is a sulfide-based solid electrolyte containing tin (Sn). This sulfide-based solid electrolyte containing tin (Sn) exhibits high ionic conductivity and high water resistance.

[0023] The aforementioned alkali metal elements include: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

[0024] The aforementioned alkaline earth metal elements include: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Rd). Furthermore, in this specification, "alkaline earth metal elements" includes both beryllium (Be) and magnesium (Mg).

[0025] In the above-mentioned context, the aforementioned alkali metal element and alkaline earth metal element are preferably lithium (Li) and / or sodium (Na), with lithium (Li) being more preferred. That is, in one embodiment, the aforementioned solid electrolyte preferably contains at least one of lithium (Li) and sodium (Na), with lithium (Li) being more preferred. In addition, the aforementioned alkali metal element and alkaline earth metal element may be contained in a single form or in combination of two or more forms.

[0026] Solid electrolytes may also contain other elements. Examples of such other elements include: silicon (Si), germanium (Ge), phosphorus (P), halogens (fluorine (F), chlorine (Cl), bromine (Br), iodine (I), oxygen (O), etc. In addition, the aforementioned other elements may be contained individually or in combination of two or more.

[0027] Examples of solid electrolytes include: solid electrolytes composed of Li, Sn, and S; solid electrolytes composed of Na, Sn, and S; solid electrolytes composed of K, Sn, and S; solid electrolytes composed of Be, Sn, and S; solid electrolytes composed of Mg, Sn, and S; solid electrolytes composed of Ca, Sn, and S; solid electrolytes composed of Li, Sn, Si, and S; solid electrolytes composed of Li, Sn, P, and S; solid electrolytes composed of Li, Sn, F, and S; solid electrolytes composed of Li, Sn, Cl, and S; solid electrolytes composed of Li, Sn, Br, and S; and solid electrolytes composed of Li, Sn, O, and... Solid electrolytes composed of Na, Sn, Si, and S; solid electrolytes composed of Na, Sn, P, and S; solid electrolytes composed of Na, Sn, F, and S; solid electrolytes composed of Na, Sn, Cl, and S; solid electrolytes composed of Na, Sn, Br, and S; solid electrolytes composed of Na, Sn, O, and S; solid electrolytes composed of Li, Sn, Si, P, and S; solid electrolytes composed of Li, Ge, Sn, P, and S; solid electrolytes composed of Na, Ge, Sn, P, and S; solid electrolytes composed of Na, Sn, Si, P, and S. Among these, the solid electrolytes are preferably composed of Li, Sn, and S; Na, Sn, and S; Li, Sn, P, and S; Li, Sn, Si, P, and S; Li, Ge, Sn, P, and S; Na, Sn, P, and S; Na, Ge, Sn, P, and S; Na, Sn, Si, P, and S; and Li, Sn, and S. Solid electrolytes composed of Na, Sn, Si, P, and S are preferred, and solid electrolytes composed of Li, Sn, and S are especially preferred.

[0028] Specific examples of solid electrolytes are not particularly limited, but can be listed as follows: Li4SnS4, Li2SnS3, Li10SnP2S12, Li9.81Sn0.81P2.19S12, Li10(Ge0.5Sn0.5)P2S12, Li10(Si0.5Sn0.5)P2S12, Li3.45[Sn0.09Si0.36] The following are suitable solid electrolytes: P0.55S4, Na4SnS4, Na4SnS4, Na2SnS3, Na10SnP2S12, Na9.81Sn0.81P2.19S12, Na10(Ge0.5Sn0.5)P2S12, Na10(Si0.5Sn0.5)P2S12, Na3.45[Sn0.09Si0.36]P0.55S4, etc. Among these, the preferred solid electrolytes are Li4SnS4, Li2SnS3, Na4SnS4, Na4SnS4, and Na2SnS3, with Li4SnS4 and Na4SnS4 being more preferred, and Li4SnS4 being even more preferred. Furthermore, the specific solid electrolytes described above can be composed of any of the above-mentioned structures, and can be composed of a single crystalline structure or a combination of different crystalline structures. For example, a solid electrolyte composed of Li4SnS4 can also be composed of a combination of Li4Sn2S6 and Li2S with different crystal structures.

[0029] There are no particular limitations on the manufacturing method of the above-mentioned solid electrolyte, and known methods may be appropriately adopted. For example, the mechanical grinding method includes the step of preparing an amorphous precursor by mechanically grinding the raw material composition and heating the aforementioned amorphous precursor; the liquid phase method includes the step of preparing the precursor in a solution, removing the solvent, and then heating the precursor, etc. Among these, the solid electrolyte is preferably manufactured by mechanical grinding.

[0030] There are no particular restrictions on the raw materials used in the manufacture of solid electrolytes, but it is preferable that the constituent elements of raw materials such as lithium sulfide (Li2S), sodium sulfide (Na2S), magnesium sulfide (MgS), strontium sulfide (SrS), monomeric sulfur, tin sulfide (SnS), and tin (Sn) are selected from the group consisting of alkali metal elements, alkaline earth metal elements, Sn element, and S element. Among these, it is even more preferable that the constituent elements of raw materials such as lithium sulfide (Li2S), sodium sulfide (Na2S), monomeric sulfur, tin sulfide (SnS), and tin (Sn) are selected from the group consisting of alkali metal elements, Sn element, and S element.

[0031] When a solid electrolyte contains other elements, it is advisable to use raw materials containing those other elements. Specific examples include: silicon sulfide (SiS2), silicon (Si), silicon dioxide (SiO2), and other raw materials containing Si; germanium sulfide (GeS2), germanium (Ge), germanium dioxide (GeO2), and other raw materials containing Ge; phosphorus monomer (P), phosphorus trisulfide (P2S3), phosphorus pentasulfide (P2S5), phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), phosphorus pentabromide (PBr5), and other raw materials containing P; lithium bromide (LiBr), sodium bromide (NaBr), iodine... Raw materials containing halogen elements, such as lithium (LiI), sodium iodide (NaI), magnesium iodide (MgI2), phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), and phosphorus pentabromide (PBr5); raw materials containing oxygen elements, such as lithium oxide (Li2O), sodium oxide (Na2O), phosphorus pentoxide (P2O5), silicon dioxide (SiO2), germanium dioxide (GeO2), tin oxide (II)(SnO), tin oxide (IV)(SnO2), and tin oxide (IV)(SnO3).

[0032] These solid electrolyte raw materials can be used alone or in combination of two or more.

[0033] The content of solid electrolyte in the good solvent solution relative to the total mass of the good solvent should preferably be 1 to 50% by mass, and more preferably 3 to 30% by mass. A solid electrolyte content of 1% by mass or more reduces the amount of solvent used, which is ideal. On the other hand, a solid electrolyte content of 50% by mass or less reduces the amount of solid electrolyte residue, which is also ideal.

[0034] (Good solvent) A good solvent will dissolve at least a portion of the solid electrolyte. In addition, in this specification, "good solvent" means a solvent with a solubility of 1 mg / mL or more of the solid electrolyte at 25°C.

[0035] Good solvents are not particularly limited and can be listed as follows: alcohol solvents, carboxylic acid solvents, lactamine solvents, water, etc.

[0036] The aforementioned alcohol solvents are not particularly limited and can be listed as follows: methanol (boiling point: 64.7℃), ethanol (boiling point: 78.4℃), propanol (boiling point: 97℃), isopropanol (boiling point: 82.5℃), 1-butanol (boiling point: 117.7℃), etc.

[0037] The aforementioned carboxylic acid solvents are not particularly limited and can be listed as follows: formic acid (boiling point: 100.8℃), acetic acid (boiling point: 118℃), etc.

[0038] The aforementioned endo-amine solvents are not particularly limited and can be listed as follows: N-methylpyrrolidone (NMP) (boiling point: 202℃), etc.

[0039] Of the above, the good solvent preferably includes an alcohol solvent, preferably including at least one selected from the group consisting of methanol, ethanol, propanol, and isopropanol, and even more preferably including methanol. In addition, one of the above good solvents may be used alone, or two or more may be used in combination.

[0040] (Unsuitable Solvent) An unsuitable solvent is a solvent with low solubility for the solid electrolyte. If the dissolved solid electrolyte comes into contact with an unsuitable solvent, the solid electrolyte will precipitate. In addition, in this specification, "unsuitable solvent" means a solvent in which the solubility of the solid electrolyte at 25°C is less than 1 mg / mL.

[0041] Undesirable solvents include: aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, ketone solvents, ether solvents, ester solvents, nitrile solvents, halogen solvents, acetylene solvents, etc.

[0042] The aforementioned aliphatic hydrocarbon solvents are not particularly limited and can be listed as follows: hexane (boiling point: 69℃), heptane (boiling point: 98.4℃), octane (boiling point: 125.6℃), etc.

[0043] The aforementioned aromatic hydrocarbon solvents are not particularly limited and can be listed as follows: benzene (boiling point: 80.1℃), toluene (boiling point: 110.6℃), xylene (boiling point: 139℃), etc.

[0044] The aforementioned ketone solvents are not particularly limited and can be listed as follows: acetone (boiling point: 56℃), methyl ethyl ketone (MEK) (boiling point: 79.6℃), etc.

[0045] The aforementioned ether solvents are not particularly limited and can be listed as follows: diethyl ether (boiling point: 34.6℃), tetrahydrofuran (THF) (boiling point: 66℃), 1,4-dimethyl ether (boiling point: 101℃), etc.

[0046] The aforementioned ester solvents are not particularly limited and can be listed as follows: methyl acetate (boiling point: 57.1℃), ethyl acetate (boiling point: 77.1℃), propyl acetate (boiling point: 102℃), methyl propionate (boiling point: 79.8℃), ethyl propionate (boiling point: 99℃), etc.

[0047] The aforementioned nitrile solvents are not particularly limited and can be listed as follows: acetonitrile (boiling point: 82℃), isobutyronitrile (boiling point: 108℃), benzonitrile (boiling point: 191℃), etc.

[0048] The aforementioned halogen solvents are not particularly limited and can be listed as follows: dichloromethane (boiling point: 39.6℃), chloroform (boiling point: 61.2℃), etc.

[0049] The aforementioned amide solvents are not particularly limited and can be listed as follows: N,N-dimethylformamide (DMF) (boiling point: 153℃), etc.

[0050] The aforementioned monoxide solvents include: dimethyl monoxide (DMSO) (boiling point: 189℃), etc.

[0051] As described above, the undesirable solvent preferably includes at least one of nitrile solvents and ester solvents, preferably at least one selected from the group consisting of acetonitrile, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, and ethyl propionate, and even more preferably at least one selected from the group consisting of acetonitrile, methyl propionate, and ethyl propionate. Furthermore, the aforementioned undesirable solvent may be used alone or in combination with two or more solvents.

[0052] The boiling point of the undesirable solvent should preferably be higher than that of the good solvent. Having a higher boiling point for the undesirable solvent makes setting and maintaining the heating temperature in step (2) easier, for example, and is therefore more desirable. Furthermore, at the predetermined heating temperature, the removal rate of the good solvent will be faster than that of the undesirable solvent, and will ideally induce the precipitation of the solid electrolyte, which is also desirable. The difference between the boiling points of the undesirable solvent and the good solvent (boiling point of undesirable solvent - boiling point of good solvent) should preferably be 5°C or higher, preferably 10°C or higher, and even more preferably 15°C or higher. There is no particular upper limit to the difference between the boiling points of the undesirable solvent and the good solvent, but it should preferably be below 200°C, preferably below 160°C, and even more preferably below 100°C. That is, according to one embodiment, the difference between the boiling point of the poor solvent and the boiling point of the good solvent (boiling point of poor solvent - boiling point of good solvent) should preferably be 10~200℃, preferably 10~160℃, even better if it is 15~160℃, and especially preferably 15~100℃.

[0053] There are no particular restrictions on the combination of good and bad solvents, but examples include: methanol-heptane (boiling point difference: 33.7℃), methanol-octane (boiling point difference: 60.9℃), methanol-benzene (boiling point difference: 15.4℃), methanol-methyl ethyl ketone (MEK) (boiling point difference: 14.9℃), methanol-1,4-dimethyl ethyl ketone (boiling point difference: 36.3℃), methanol-propyl acetate (boiling point difference: 37.3℃), methanol-methyl propionate (boiling point difference: 15.1℃), methanol-ethyl propionate (boiling point: 34.3℃), methanol-acetonitrile (boiling point difference: 17.3℃), methanol-benzonitrile (boiling point difference: 126.3℃), methanol-N,N-dimethylformamide (… The following are examples of dimethyl methoxide (DMF) with a boiling point difference of 88.3℃: methanol-dimethyl methoxide (DMSO) with a boiling point difference of 124.3℃, ethanol-heptane with a boiling point difference of 20℃, ethanol-octane with a boiling point difference of 47.2℃, ethanol-toluene with a boiling point difference of 32.2℃, ethanol-1,4-dimethyl methoxide with a boiling point difference of 22.6℃, ethanol-propyl acetate with a boiling point difference of 23.6℃, ​​ethanol-ethyl propionate with a boiling point difference of 20.6℃, ethanol-benzonitrile with a boiling point difference of 112.6℃, ethanol-N,N-dimethylformamide (DMF) with a boiling point difference of 74.6℃, and ethanol-dimethyl methoxide (DMSO) with a boiling point difference of 110.6℃. Among these, the preferred combination of good and bad solvents is methanol-1,4-dimethylethanol (boiling point difference: 36.3℃), methanol-propyl acetate (boiling point difference: 37.3℃), methanol-methyl propionate (boiling point difference: 15.1℃), methanol-ethyl propionate (boiling point: 34.3℃), methanol-acetonitrile (boiling point difference: 17.3℃), ethanol-1,4-dimethylethanol (boiling point difference: 22.6℃), ethanol-propyl acetate (boiling point difference: 23.6℃), and ethanol-ethyl propionate (boiling point difference: 20.6℃), with methanol-ethyl propionate (boiling point: 34.3℃) and methanol-acetonitrile (boiling point difference: 17.3℃) being even better.

[0054] The volume ratio of the poor solvent to the good solvent (volume of poor solvent / volume of good solvent) is 5 or more, preferably 7.5 or more, more preferably 12.5 or more, and even more preferably 15 or more. If the aforementioned volume ratio is 5 or more, small solid electrolyte particles will precipitate in step (2) described later, which is ideal. In addition, if the upper limit of the aforementioned volume ratio is for preparing a mixed solution, there is no particular restriction, but it is preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less. That is, according to one embodiment, the volume ratio of the poor solvent to the good solvent (volume of poor solvent / volume of good solvent) is preferably 7.5 to 50, more preferably 12.5 to 50, even more preferably 15 to 50, particularly preferably 15 to 40, and best preferably 15 to 30.

[0055] (Mixed Solution) The mixed solution contains a solid electrolyte, a good solvent, and a poor solvent. The mixed solution may also contain known additives. In addition, the solid electrolyte is usually dissolved in the mixed solution.

[0056] The content of solid electrolyte in the mixed solution relative to the total mass of the mixed solution should preferably be 0.03 to 9% by mass, and 0.1 to 5% by mass is more preferred.

[0057] The total content of good solvent and bad solvent in the mixed solution relative to the total mass of the mixed solution should preferably be 91 to 99.9% by mass, and 95 to 99.9% by mass is even better.

[0058] [Step (2)] Step (2) is a step of removing at least a portion of the good solvent from the mixed solution to precipitate solid electrolyte particles. By removing at least a portion of the good solvent from the mixed solution, the content of the bad solvent will increase, and thus the solid electrolyte in the mixed solution will precipitate. In this way, by precipitating the solid electrolyte from the mixed solution in which the solid electrolyte is dissolved in the good solvent and the bad solvent, micronized solid electrolyte particles can be obtained.

[0059] (Removal of good solvents) There are no particular limitations on the methods for removing good solvents, and examples include: methods of heating the mixed solution, pervaporation, membrane distillation and other methods utilizing membrane separation, and selective adsorption and other methods of adsorbing good solvents. Among these, methods of heating the mixed solution are preferable for removing good solvents.

[0060] In an ideal embodiment, the boiling point of the poor solvent is higher than that of the good solvent. By heating the mixed solution, the good solvent is relatively easier to evaporate than the poor solvent, thus ideally removing the good solvent.

[0061] The heating temperature should be sufficient to remove at least a portion of the good solvent. Although this varies depending on the type of good solvent, a temperature above the boiling point of the good solvent and below the boiling point of the bad solvent is preferable. 10-100°C is more desirable, 20-80°C is even better, and 40-60°C is particularly ideal. A heating temperature within this range reduces manufacturing costs, making it more desirable. Furthermore, the heating temperature can be set below the boiling point of the good solvent by reducing pressure.

[0062] There are no particular restrictions on the heating pressure, but it is preferable to be below 1500 hPa, preferably 10⁻² hPa to 1024 hPa, and even more preferably 1 hPa to 300 hPa. If the heating pressure is within the above range, the temperature during solvent removal can be reduced and the decomposition and dissolution of solid electrolytes can be suppressed, which is ideal.

[0063] By removing at least a portion of the good solvent, the content ratio of the bad solvent will increase, and thus the solid electrolyte in the mixed solution will precipitate. At this time, in step (2), the good solvent can be completely removed or at least a portion of the good solvent can remain. It is preferable to remove the good solvent completely.

[0064] In addition, at least a portion of the solid electrolyte particles and the undesirable solvent or at least a portion of the undesirable solvent and the good solvent can be removed by performing filtration or the like after step (2) and before step (3).

[0065] [Step (3)] Step (3) is the step of drying the solid electrolyte particles to obtain solid electrolyte powder. By performing drying, undesirable solvents, good solvents, etc. that may remain inside the solid electrolyte particles can be removed.

[0066] (Drying) If the drying temperature is a temperature that can remove residual undesirable solvents, or undesirable solvents and good solvents, there is no particular limitation. It is preferable to be above 100°C, preferably 120~300°C, and even more preferably 150~250°C.

[0067] There are no particular restrictions on the drying pressure, but it is preferable to be below 500 hPa, preferably 10⁻² hPa to 200 hPa, and even better to be 1 hPa to 50 hPa. If the drying pressure is within the above range, residual undesirable solvents, or a mixture of undesirable and good solvents, can be effectively removed, which is ideal.

[0068] (Solid electrolyte powder) Because solid electrolyte powder is micronized, the interfacial resistance between the solid electrolyte layer formed using this solid electrolyte powder and the electrode layer is reduced. As a result, all-solid-state batteries with high energy density and high output can be manufactured.

[0069] The average particle size of the solid electrolyte powder is preferably 20 μm or less, more preferably 10 μm or less, even more preferably 5 μm or less, particularly preferably 3 μm or less, and best preferably 1.5 μm or less. Furthermore, from an operability perspective, the average particle size of the solid electrolyte powder is preferably 0.1 μm or more. Additionally, in this specification, "average particle size" refers to the median particle size (D50), which is determined using the method described in the examples.

[0070] <Method for Manufacturing an All-Solid-State Battery> According to one aspect of the present invention, a method for manufacturing an all-solid-state battery is provided. The method includes the steps of stacking a solid electrolyte layer, a positive electrode layer, and a negative electrode layer to form an all-solid-state battery, wherein the solid electrolyte layer is formed using solid electrolyte powder obtained by the above method. Furthermore, "all-solid-state battery" refers to a battery that uses a solid electrolyte. An all-solid-state battery typically includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

[0071] The aforementioned solid electrolyte layer is formed using solid electrolyte powder prepared by the above method. In this case, the aforementioned solid electrolyte layer may be manufactured using only the aforementioned solid electrolyte powder, or it may be manufactured using other solid electrolytes in combination. Examples of such other solid electrolytes include: tin-containing sulfide-based solid electrolytes, tin-free sulfide-based solid electrolytes, oxide-based solid electrolytes, and complex hydride solid electrolytes prepared by other methods. One of these other solid electrolytes may be used alone, or two or more may be used in combination.

[0072] The solid electrolyte powder prepared by the above method is a sulfide-based solid electrolyte containing tin (Sn), so the resulting solid electrolyte layer exhibits high ionic conductivity and high water resistance. Furthermore, the solid electrolyte powder prepared by the above method is micronized, so the interfacial resistance between the solid electrolyte layer and the electrode layer is reduced, which contributes to the high energy density and high output of the all-solid-state battery.

[0073] Furthermore, the positive electrode layer and / or negative electrode layer can also be formed using solid electrolyte powder prepared by the above method. When using solid electrolyte powder to manufacture the positive electrode layer and negative electrode layer, the positive electrode layer and negative electrode layer are formed by combining known positive electrode active materials or negative electrode active materials for lithium-ion secondary batteries. In this case, there is no particular limitation on the content ratio of solid electrolyte powder contained in the positive electrode layer or negative electrode layer. In addition, the positive electrode layer and negative electrode layer may also contain known current collectors, conductive additives, binders, etc.

[0074] The all-solid-state battery is made by forming and stacking the above-mentioned positive electrode layer, solid electrolyte layer and negative electrode layer, but there are no particular restrictions on the forming method and stacking method of each layer.

[0075] For example, there are: a method of forming a film by dispersing a solid electrolyte and / or electrode active material in a solvent to form a slurry, coating it with a doctor blade or spin coating, and then calendering it; a vapor phase method of forming and stacking films using vacuum evaporation, ion plating, sputtering, laser ablation, etc.; and a pressure forming method of forming powders by hot pressing or cold pressing without applying temperature and then stacking them.

[0076] The solid electrolyte powder obtained by the above method is a tin-containing sulfide solid electrolyte powder and is relatively soft. Therefore, it is particularly suitable for forming and stacking layers using a pressure forming method to manufacture an all-solid-state battery. The pressure forming method includes hot pressing with heating and cold pressing without heating; even in cold pressing, the shape can still be adequately formed. [Example]

[0077] Hereinafter, the present invention will be described in more detail by way of embodiments, but the present invention is not limited to these embodiments.

[0078] [Manufacturing Example] A solid electrolyte having the composition of Li4SnS4 is manufactured by the following method.

[0079] Li₂S (purity: 99.8%, manufactured by Sigma-Aldrich) and SnS₂ (purity: 99.9%, manufactured by High Purity Chemical Research Institute Co., Ltd.) were weighed in an argon-atmospheric glove box to achieve a stoichiometric ratio of Li₄SnS₄, and mixed for 15 minutes using an agate mortar. 1.0 g of the resulting mixture and 15 zirconia balls (outer diameter φ: 10 mm) were placed in a 45 mL zirconia jar and sealed. The zirconia jar was fixed in a planetary ball mill (manufactured by Fritsch-Japan Co., Ltd.) and ball milled at 370 rpm for 4 hours. The resulting precursor was calcined at 450 °C for 8 hours to obtain a solid electrolyte having the composition of Li₄SnS₄.

[0080] [Example 1] (Preparation of a good solvent solution) In a glove-operated chamber under argon atmosphere, 500 mg of Li4SnS4 was added to 5 mL of methanol (super-dehydrating grade, boiling point: 64°C, manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.), a good solvent, and mixed at room temperature (25°C) for 24 hours. The Li4SnS4 dissolved slowly. The insoluble matter from the Li4SnS4 manufacturing process contained in the resulting solution was filtered through a membrane (polytetrafluoroethylene (PTFE), pore size: 1.0 μm) to obtain a good solvent solution containing dissolved Li4SnS4. The concentration of Li4SnS4 in the good solvent solution was 13% by mass.

[0081] (Step (1)) Add 50 mL of acetonitrile, which is a poor solvent, to a good solvent solution and mix them to prepare a mixed solution.

[0082] (Step (2)) The mixed solution is heated at 50°C under reduced pressure (200 hPa) to precipitate Li4SnS4 particles. In addition, the heating causes a portion of the methanol and acetonitrile to evaporate, and the Li4SnS4 particles precipitate along with this evaporation.

[0083] (Step (3)) The solution in which Li4SnS4 particles have precipitated is stirred at 50°C under reduced pressure (100 hPa) while being continuously heated to remove the solvent. Then, the Li4SnS4 particles are dried at 180°C under vacuum (1 hPa) for 4 hours to remove the solvent located on the Li4SnS4 particles, thereby obtaining Li4SnS4 powder.

[0084] The average particle size of the Li4SnS4 powder obtained was determined by the following method.

[0085] A small sample of Li4SnS4 powder was taken and added to acetonitrile, which is the dispersion medium. The powder was then dispersed for 3 minutes using an ultrasonic homogenizer (SMT UH-50). The particle size distribution was then measured using a laser scattering-diffraction particle size analyzer (Nikko Misrotrac MT3000EXII) to determine the average particle size (D50).

[0086] As a result, the average particle size (D50) of the Li4SnS4 powder was 1.7 μm.

[0087] [Example 2] The amount of acetonitrile used was changed to 25 mL, and Li4SnS4 powder was prepared using the same method as in Example 1. The average particle size (D50) of the Li4SnS4 powder was measured to be 4 μm using the same method as in Example 1.

[0088] [Example 3] The amount of acetonitrile used was changed to 100 mL, and Li4SnS4 powder was prepared in the same manner as in Example 1. The average particle size (D50) of the Li4SnS4 powder was measured to be 1.1 μm in the same manner as in Example 1.

[0089] [Example 4] Li4SnS4 powder was prepared by replacing acetonitrile with 50 mL of ethyl propionate, except that it was prepared by the same method as in Example 1. The average particle size (D50) of the Li4SnS4 powder was measured to be 1.7 μm by the same method as in Example 1.

[0090] [Comparative Example 1] Li4SnS4 powder was prepared in the same manner as in Example 1, except that a good solvent solution was not added to acetonitrile. The average particle size (D50) of the Li4SnS4 powder was 24 μm when measured in the same manner as in Example 1.

[0091] The results obtained from Examples 1-4 and Comparative Example 1 are shown in Table 1 below.

[0092] [Table 1] good solvent Poor solvents Volume ratio of good solvent to bad solvent Average particle size of Li4SnS4 powder (μm) Li4SnS4 concentration (quality%) Solvent volume (mL) type Solvent volume (mL) Example 1 13 5 Acetonitrile 50 10 1.7 Example 2 13 5 Acetonitrile 25 5 4.0 Example 3 13 5 Acetonitrile 100 20 1.1 Example 4 13 5 Ethyl propionate 50 10 1.7 Comparative Example 1 13 5 - - - twenty four

[0093] As can be seen from the results in Table 1, the Li4SnS4 powder prepared by the methods in Examples 1 to 4 was micronized.

Claims

1. A method for manufacturing a solid electrolyte powder, comprising: step (1), adding a poor solvent to a good solvent solution containing a solid electrolyte and a good solvent to prepare a mixed solution, wherein the solid electrolyte contains at least one of an alkali metal element and an alkaline earth metal element, an element Sn, and an element S; step (2), removing at least a portion of the good solvent from the mixed solution to precipitate solid electrolyte particles; and step (3), drying the solid electrolyte particles to obtain a solid electrolyte powder; wherein the volume ratio of the poor solvent to the volume of the good solvent (volume of poor solvent / volume of good solvent) is 5 or more.

2. A method for manufacturing solid electrolyte powder as claimed in claim 1, wherein, The solid electrolyte contains at least one of lithium (Li) and sodium (Na).

3. A method for manufacturing solid electrolyte powder as claimed in claim 1, wherein, The solid electrolyte is composed of Li, Sn, and S elements.

4. A method for manufacturing solid electrolyte powder as claimed in claim 1, wherein, This good solvent includes alcohol solvents.

5. A method for manufacturing the solid electrolyte powder as described in any of claims 1 to 4, wherein, The undesirable solvent includes at least one of nitrile solvents and ester solvents.

6. A method for manufacturing the solid electrolyte powder as described in any of claims 1 to 4, wherein, The average particle size of the solid electrolyte powder is less than 20 μm.

7. A method for manufacturing the solid electrolyte powder as described in any of claims 1 to 4, wherein, The difference between the boiling point of a poor solvent and the boiling point of a good solvent (boiling point of poor solvent - boiling point of good solvent) is 10~200℃.

8. A method for manufacturing an all-solid-state battery, comprising the following steps: stacking a solid electrolyte layer, a positive electrode layer, and a negative electrode layer to form an all-solid-state battery, wherein the solid electrolyte layer is formed using solid electrolyte powder obtained by the method for manufacturing solid electrolyte powder as described in any one of claims 1 to 7.