JP2020027781A - Method for manufacturing lgps-based solid electrolyte - Google Patents

Abstract

To provide a method for manufacturing an LGPS-based solid electrolyte which is excellent in productivity, suppresses generation of a by-product, and exhibits stable performance.SOLUTION: A method for manufacturing an LGPS-based solid electrolyte includes: a slurry liquefaction step of stirring LiPSin an organic solvent to prepare a slurry liquid; a homogeneous liquefaction step of dissolving LiSnSin an alcohol-based solvent to prepare a homogeneous solution; a homogeneous mixing liquefaction step of mixing the slurry liquid and the homogeneous solution to prepare a homogeneous mixing solution; a drying step of removing a mixed solvent of the organic solvent and the alcohol-based solvent from the homogeneous mixing solution to obtain a precursor; and a heat treatment step of heat-treating the precursor at 200-700°C to obtain an LGPS-based solid electrolyte.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an LGPS-based solid electrolyte. Note that the LGPS-based solid electrolyte refers to a solid electrolyte having a specific crystal structure including Li, P, and S. For example, Li, M (M is at least one selected from the group consisting of Ge, Si, and Sn) ), A solid electrolyte containing P and S.

  In recent years, demand for lithium ion secondary batteries has increased for applications such as portable information terminals, portable electronic devices, electric vehicles, hybrid electric vehicles, and stationary power storage systems. However, the current lithium ion secondary battery uses a flammable organic solvent as an electrolytic solution, and requires a strong exterior so that the organic solvent does not leak. In addition, in the case of a portable personal computer or the like, there is a restriction on the structure of the device, such as the necessity of taking a structure for the risk in the event of leakage of the electrolyte.

  Further, its use has been extended to mobile objects such as automobiles and airplanes, and large capacity is required for stationary lithium ion secondary batteries. Under these circumstances, safety has tended to be more important than ever, and efforts have been made to develop an all-solid-state lithium ion secondary battery that does not use harmful substances such as organic solvents.

For example, use of an oxide, a phosphate compound, an organic polymer, a sulfide, or the like as a solid electrolyte in an all-solid-state lithium ion secondary battery has been studied.
Among these solid electrolytes, sulfides have a high ionic conductivity and are relatively soft and easily form a solid-solid interface. It is stable for active materials and is being developed as a practical solid electrolyte.

All-solid-state batteries have difficulty in forming a solid-solid interface, and need to be molded under a high press pressure. On the other hand, it is disclosed that a good interface is formed at a low press pressure by using a solution-formed solid electrolyte (Patent Document 1). However, the positive electrode layer and the negative electrode layer need to be formed under a high press pressure, and when the sulfide solid electrolyte is dissolved in an alcohol solvent, the sulfide solid electrolyte is gradually decomposed to generate hydrogen sulfide. Was. Further, a method of homogenizing a Li ₂ SP ₂ S ₅ -based solid electrolyte using an N-methylformamide solvent is also disclosed, but the ionic conductivity of the solid electrolyte obtained from this system is 2.6 × 10 5 ⁻⁶ S / cm, which is not always high.

JP 2015-2080 A

The 54th Battery Symposium, 3E17 (2013)

  Under such circumstances, it is desired to provide a method for producing an LGPS-based solid electrolyte which is excellent in productivity, suppresses generation of by-products, and exhibits stable performance.

  Therefore, the present inventors have conducted intensive studies in view of the above problems, and have obtained unexpected findings that the following present invention can produce an LGPS-based solid electrolyte having stable performance with less impurities. .

That is, the present invention is as follows.
<1> a slurry liquefaction step of preparing a slurry liquid by stirring Li ₃ PS ₄ in an organic solvent;
A uniform solution preparation step of preparing a uniform solution by dissolving Li ₄ SnS ₄ in an alcohol-based solvent;
A mixed uniform solution preparation step of preparing a mixed uniform solution by mixing the slurry liquid and the uniform solution,
A drying step of removing a mixed solvent of the organic solvent and the alcohol-based solvent from the mixed homogeneous solution to obtain a precursor,
A heat treatment step of subjecting the precursor to heat treatment at 200 to 700 ° C. to obtain an LGPS-based solid electrolyte.
<2> The above-mentioned <1>, wherein the Li ₃ PS ₄ has a peak at 420 ± 10 cm ⁻¹ in Raman measurement, and the Li ₄ SnS ₄ has a peak at 346 ± 10 cm ⁻¹ in Raman measurement. It is a manufacturing method of.
<3> The method according to <1> or <2>, wherein the organic solvent is at least one selected from the group consisting of tetrahydrofuran, acetonitrile, ethyl acetate, and methyl acetate.
<4> The method according to any one of <1> to <3>, wherein the alcohol-based solvent is at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 1-butanol. is there.
<5> The method according to any one of <1> to <4>, wherein the temperature in the drying step is 60 to 280 ° C.
<6> At least 2θ = 19.80 ° ± 0.50 °, 20.10 ° ± 0.50 °, 26.10 ° in X-ray diffraction (CuKα: λ = 1.5405 °) of the LGPS-based solid electrolyte. The method according to any one of the above items <1> to <5>, having peaks at positions of 60 ° ± 0.50 ° and 29.10 ° ± 0.50 °.
<7> the diffraction intensity of the peak of the 2θ = 29.10 ° ± 0.50 ° and _{I A,} the diffraction intensity of the peak of 2θ = 27.33 ° ± 0.50 ° when the _{I B,} I the value of _B / _{I a} is less than 0.50, a method according to the <6>.
<8> The LGPS based solid electrolyte, and a octahedron O composed of Li element and S elements, a tetrahedron T ₁ composed of one or more elements and S element selected from the group consisting of P and Sn, and a tetrahedron T ₂ composed of P element and S elements, the tetrahedron T ₁ and the octahedron O share the crest the tetrahedron T ₂ and the octahedron O share a vertex crystals The method according to any one of <1> to <7>, wherein the method mainly includes a structure.
<9> The method according to any one of <1> to <8>, wherein the heat treatment step is performed in an inert gas atmosphere.
<10> A molded product obtained by press-molding the LGPS solid electrolyte obtained by the production method according to any one of <1> to <9>.
<11> A method for producing an all-solid battery, including a step of pressure-forming the LGPS-based solid electrolyte obtained by the production method according to any one of <1> to <9>.

  According to the present invention, a method for producing an LGPS-based solid electrolyte can be provided. Moreover, this manufacturing method is applicable to mass production.

FIG. 1 is a schematic diagram illustrating a crystal structure of an LGPS-based solid electrolyte according to an embodiment of the present invention. 1 is a schematic sectional view of an all solid state battery according to one embodiment of the present invention. 5 is a graph showing the results of X-ray diffraction measurement of the ionic conductors obtained in Examples 1 to 4 and Reference Example 1. 5 is a graph showing the results of ionic conductivity measurement of the ionic conductors obtained in Examples 1 to 4 and Reference Example 1. 5 is a graph showing the results of Raman spectroscopy measurement of β-Li ₃ PS ₄ and Li ₄ SnS ₄ prepared in Example 1.

  Hereinafter, the method for producing the LGPS-based solid electrolyte of the present invention will be specifically described. Note that the materials, configurations, and the like described below do not limit the present invention, but can be variously modified within the scope of the present invention.

<Method for producing LGPS-based solid electrolyte>
The method for producing an LGPS solid electrolyte of the present invention comprises a slurry liquefaction step of preparing a slurry liquid by stirring Li ₃ PS ₄ in an organic solvent, and a uniform method by dissolving Li ₄ SnS ₄ in an alcohol solvent. A uniform solution preparation step of preparing a solution, a mixed uniform solution preparation step of preparing a mixed uniform solution by mixing the slurry liquid and the uniform solution, and the organic solvent and the alcohol solvent from the mixed uniform solution. And a heat treatment step of heating the precursor at 200 to 700 ° C. to obtain an LGPS solid electrolyte.
Li ₃ PS ₄ used in the present invention preferably has a peak at 420 ± 10 cm ⁻¹ in Raman measurement. In addition, Li ₄ SnS ₄ used in the present invention preferably has a peak at 346 ± 10 cm ⁻¹ in Raman measurement.
In the X-ray diffraction (CuKα: λ = 1.5405 °), at least 2θ = 19.80 ° ± 0.50 °, 20.10 ° ± 0.50 °, 26.60 ° ± It is preferable to have peaks at 0.50 ° and 29.10 ° ± 0.60 ° (more preferably 29.10 ° ± 0.50 °). 2θ = 17.00 ± 0.50 °, 19.80 ° ± 0.50 °, 20.10 ° ± 0.50 °, 23.50 ± 0.50 °, 26.60 ° ± 0.50 °, 28.60 ± 0.50 °, 29.10 ° ± 0.60 ° (more preferably 29.10 ° ± 0.50 °) and more preferably has a peak.

Further, the LGPS based solid electrolyte, the 2 [Theta] = 29.10 diffraction intensity of the peak of ° ± 0.50 ° and _{I A,} the diffraction intensity of the peak of _{2θ = 27.33 ° ± 0.50 ° I} B in case of _a, it is preferable the value of I B / _{I a} is less than 0.50. More _preferably, the value of I B / _{I A} is less than 0.40. This is the peak of LGPS crystal to correspond to I _A, I _B is for ionic conductivity is low crystalline phase.
Further, as shown in FIG. 1, the LGPS-based solid electrolyte is composed of an octahedron O composed of an Li element and an S element, and one or more elements selected from the group consisting of P and Sn and an S element. A tetrahedron T ₁ and a tetrahedron T ₂ composed of a P element and an S element, wherein the tetrahedron T ₁ and the octahedron O share an edge, and the tetrahedron T ₂ and the octahedron O O preferably contains mainly a crystal structure sharing a vertex.

As a conventional method for producing an LGPS-based solid electrolyte, an ion conductor is synthesized using Li ₂ S, P ₂ S _5, and M _x S _y (eg, GeS ₂ ) as raw materials, and then mechanical milling using a vibration mill or a planetary ball mill. Method (WO2011-118801) and the melt quenching method described in WO2014-196442. However, it is difficult to increase the size of the mechanical milling method to an industrial scale, and there is a great limitation in terms of atmosphere control when the melting and quenching method is performed without exposure to the atmosphere. The LGPS-based solid electrolyte and its raw material have a property of reacting with moisture or oxygen in the atmosphere and being deteriorated. On the other hand, the manufacturing method according to the present invention does not require an amorphization step. Using Li ₃ PS ₄ and Li ₄ SnS ₄ as raw materials, a slurry solution is prepared by stirring Li ₃ PS ₄ in an organic solvent, and a uniform solution is obtained by dissolving Li ₄ SnS ₄ in an alcohol solvent. And preparing a mixed homogeneous solution by mixing the slurry solution and the uniform solution, removing a mixed solvent of an organic solvent and an alcohol solvent from the mixed homogeneous solution to obtain a precursor, and then performing a heat treatment. Is performed, an LGPS-based solid electrolyte can be obtained. Since Li ₄ SnS ₄ is stable to alcohol, it can be dissolved in alcohol in advance. By doing so, the dissolution time of the raw material can be shortened. On the other hand, Li ₃ PS ₄ gradually decomposes in alcohol, and therefore, when suspended in THF or the like, the stability to alcohol increases. This is presumed that THF suppresses the reaction with alcohol by solvating with Li ₃ PS ₄ . In addition, using Li ₃ PS ₄ as a raw material is important because volatilization and decomposition of a precursor during heat treatment can be suppressed. When P ₂ S ₅ is present in the precursor (can be determined by Raman measurement), by the influence of P ₂ S ₅ having high volatility and decomposability, generation of by-products and unreacted raw materials are large in the heat treatment step. Therefore, it is difficult to obtain a stable and high-performance LGPS solid electrolyte.

<Li ₃ PS ₄ >
Li ₃ PS ₄ can be used in any of α, β, and γ, but is more preferably β-LPS. The reason for this is that it is relatively stable in the LGPS synthesis system.
Li ₃ PS ₄ in the present invention may be a commercially available product. For example, it can be synthesized from sulfides represented by Li ₂ S and P ₂ S ₅ under an inert gas atmosphere such as argon. . As an example of the method for producing Li ₃ PS ₄ , Li ₂ S and P ₂ S ₅ are weighed to give a molar ratio of Li ₂ S: P ₂ S ₅ = 1.5: 1, and (Li ₂ S + P _A homogeneous solution can be obtained by adding Li ₂ S and P ₂ S ₅ in this order to tetrahydrofuran so that the concentration of ₂ S ₅ ) becomes 10 wt% and mixing at room temperature for a predetermined time. At this time, depending on the purity of the raw material and the degree of progress of the reaction, a slight amount of precipitate may be present, but the purity of the finally obtained Li ₃ PS ₄ is not significantly affected. However, when a precipitate is generated, the precipitate can be removed by performing filtration. Li ₂ S is further added to the obtained homogeneous solution so that the total raw material composition including the above becomes Li ₂ S: P ₂ S ₅ = 3: 1 by weight, and mixed at room temperature for a predetermined time. , Get a precipitate. Li ₃ PS ₄ can be manufactured by vacuum-drying the filter obtained by filtering this.

Li ₂ S can be used as a synthetic product or a commercial product. Since the mixing of moisture deteriorates other raw materials and precursors, the lower the amount, the more preferable it is, more preferably 300 ppm or less, and particularly preferably 50 ppm or less.
In addition, even if some of the above-mentioned raw materials are amorphous, they can be used without any problem.
It is important that the particle diameter of any of the raw materials is small, preferably the particle diameter is in the range of 10 nm to 10 μm, more preferably 10 nm to 5 μm, and still more preferably 100 nm to 1 μm. The particle size can be measured by a SEM or a particle size distribution measuring device using laser scattering. When the particles are small, the reaction becomes easy during the heat treatment, and the generation of by-products can be suppressed.

<Slurry liquefaction process>
In the slurry liquefaction step, a slurry liquid is prepared by stirring Li ₃ PS ₄ in an organic solvent.
The stirring method using an organic solvent is suitable for a case where a large amount is synthesized because the stirring method can be performed uniformly. It is preferable that the organic solvent used does not react with the raw materials and the obtained precursor. For example, ether solvents, ester solvents, hydrocarbon solvents, nitrile solvents and the like can be mentioned. Specific examples include tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether, diethyl ether, dimethyl ether, dioxane, methyl acetate, ethyl acetate, butyl acetate, acetonitrile and the like. Among these, at least one selected from the group consisting of tetrahydrofuran, acetonitrile, ethyl acetate, and methyl acetate is preferable. In order to prevent the raw material composition from deteriorating, it is preferable to remove oxygen and water in the solvent, and the water content is particularly preferably 100 ppm or less, more preferably 50 ppm or less.
The stirring is preferably performed under an inert gas atmosphere. Nitrogen, helium, argon, or the like can be used as the inert gas, and the deterioration of the raw material composition can be suppressed by removing oxygen and moisture in the inert gas. The concentrations of oxygen and moisture in the inert gas are both preferably 1000 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less.

<Li ₄ SnS ₄ >
Li ₄ SnS ₄ in the present invention may be a commercially available product. For example, it can be synthesized from a sulfide represented by Li ₂ S and SnS ₂ under an inert gas atmosphere such as argon. As an example of the method for producing Li ₄ SnS ₄ , Li ₂ S: SnS ₂ = 2: 1 is weighed out and mixed in an agate mortar. Then, the resulting mixture was poured into a zirconia pot, and further charged with zirconia balls, was completely sealed pot, attach the pot planetary ball mill, by performing mechanical milling, Li ₄ SnS ₄ can be manufactured. Since SnS ₂ is not dissolved in alcohol in the subsequent homogeneous solution formation step, the purity of Li ₄ SnS ₄ is preferably high, specifically, 95% or more, more preferably 98% or more. .

<Homogeneous solution process>
In the uniform solution preparation step, a uniform solution is prepared by dissolving Li ₄ SnS ₄ in an alcohol-based solvent.
Examples of the alcohol solvent include methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol and the like. Among these, at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 1-butanol is preferable.
The dissolution is preferably performed in an inert gas atmosphere. Nitrogen, helium, argon, or the like can be used as the inert gas, and the deterioration of the raw material composition can be suppressed by removing oxygen and moisture in the inert gas. The concentrations of oxygen and moisture in the inert gas are both preferably 1000 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less.

<Mixing uniform solution process>
In the mixed uniform solution forming step, a mixed uniform solution is prepared by mixing the slurry liquid and the uniform solution. The molar ratio may be adjusted so as to be the element ratio constituting the above-mentioned crystal structure, but it can be obtained if the molar ratio is Li ₃ PS ₄ : Li ₄ SnS ₄ = 3: 1 to 2: 3. In the XRD measurement, the ionic conductor almost has a peak of only the LGPS crystal, and the ionic conductivity is high. For example, in the case of Li ₁₀ SnP ₂ S ₁₂ , the mixture is performed at a molar ratio of Li ₃ PS ₄ : Li ₄ SnS ₄ = 2: 1.

  The mixing is preferably performed under an inert gas atmosphere. Nitrogen, helium, argon, or the like can be used as the inert gas, and the deterioration of the raw material composition can be suppressed by removing oxygen and moisture in the inert gas. The concentrations of oxygen and moisture in the inert gas are both preferably 1000 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less.

It is preferable that all of the raw materials are uniformly dissolved by mixing the slurry solution and the uniform solution.
The temperature for mixing does not need to be heated, but when an organic solvent is used, it can be heated to increase the solubility and dissolution rate of the substrate. When heating, it is sufficient to perform the heating at a temperature lower than the boiling point of the organic solvent. However, it is also possible to carry out in a pressurized state using an autoclave or the like. Note that when mixing is performed at a high temperature, the reaction proceeds before the raw materials are well mixed, and a by-product is easily generated. Therefore, the mixing is preferably performed at around room temperature.
As the mixing time, it is sufficient that the time for the mixture to be uniform can be secured. Although the time often depends on the production scale, it can be made uniform by, for example, performing for 0.1 to 24 hours.

<Drying process>
In the drying step, a precursor is obtained by removing the mixed solvent of the organic solvent and the alcoholic solvent from the mixed homogeneous solution obtained in the mixed uniform solution forming step. The solvent is removed by heating or vacuum drying, and the optimum temperature varies depending on the type of the organic solvent. By applying a temperature sufficiently higher than the boiling point, the solvent removal time can be shortened. In addition, the type of solvent and the drying temperature have an important relationship, and by maintaining a temperature at which the solvent can be sufficiently removed, and by not increasing the drying temperature more than necessary, it is possible to suppress a side reaction between the precursor and the solvent. it can. The temperature at which the organic solvent is removed is preferably in the range of 60 to 280 ° C, and more preferably 100 to 250 ° C. In addition, by removing the organic solvent under reduced pressure such as vacuum drying, the temperature for removing the organic solvent can be reduced and the required time can be shortened. Also, by flowing an inert gas such as nitrogen or argon having a sufficiently low moisture content, the time required for removing the solvent can be shortened. Note that the subsequent heat treatment step and solvent removal can be performed simultaneously.

<Heat treatment step>
In the production method of the present invention, an LGPS solid electrolyte is obtained by subjecting the precursor obtained in the drying step to a heat treatment at 300 to 700 ° C. The heating temperature is preferably in the range of 350 to 650 ° C, more preferably in the range of 400 to 600 ° C. If the temperature is lower than 300 ° C., desired crystals are less likely to be generated. On the other hand, if the temperature is higher than 700 ° C., crystals other than the target are formed, and the ionic conductivity is reduced.

Although the heating time varies slightly depending on the heating temperature, the crystallization is usually sufficient in the range of 0.1 to 24 hours. Heating at a high temperature beyond the above range for a long time is not preferable because there is a concern about deterioration of the LGPS solid electrolyte.
The heating can be performed under vacuum or an inert gas atmosphere, but is preferably performed under an inert gas atmosphere. As the inert gas, nitrogen, helium, argon and the like can be used, and among them, argon is preferable. It is preferable that oxygen and moisture are low, and the conditions are the same as those in the dissolution in the uniform solution process.

  The LGPS-based solid electrolyte of the present invention obtained as described above can be formed into a desired molded body by various means, and can be used for various applications including the all solid state battery described below. The molding method is not particularly limited. For example, a method similar to the method of forming each layer constituting the all-solid-state battery described below in the all-solid-state battery can be used.

<All-solid-state battery>
The LGPS-based solid electrolyte of the present invention can be used, for example, as a solid electrolyte for an all-solid battery. According to a further embodiment of the present invention, there is provided an all-solid battery including the above-described solid electrolyte for an all-solid battery.

Here, the "all solid state battery" is an all solid state lithium ion secondary battery. FIG. 2 is a schematic sectional view of the all-solid-state battery according to one 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 such as a mobile phone, a personal computer, and an automobile.
The LGPS solid electrolyte of the present invention may be contained 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 positive electrode layer 1 or the negative electrode layer 3 contains the LGPS solid electrolyte of the present invention, the LGPS 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 amount ratio of the LGPS solid electrolyte of the present invention contained in the positive electrode layer 1 or the negative electrode layer 3 is not particularly limited.
When the solid electrolyte layer 2 contains the LGPS solid electrolyte of the present invention, the solid electrolyte layer 2 may be composed of the solid LGPS solid electrolyte of the present invention alone, or may be an oxide solid electrolyte (for example, if necessary). , Li ₇ La ₃ Zr ₂ O ₁₂ ), a sulfide-based solid electrolyte (eg, Li ₂ S—P ₂ S ₅ ), and other complex hydride solid electrolytes (eg, LiBH ₄ , 3LiBH ₄ —LiI). They may be used in combination.

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.
For example, a method in which a solid electrolyte and / or an electrode active material is dispersed in a solvent to form a slurry and applied by a doctor blade or spin coating and the like is rolled to form a film; vacuum deposition, ion plating Gas phase method of forming and laminating a film using a sputtering method, a laser ablation method, etc .; a pressure molding method of forming a powder by hot pressing or cold pressing without applying a temperature and laminating the powder; .

Since the LGPS solid electrolyte of the present invention is relatively soft, it is particularly preferable to form and laminate each layer by a pressure molding method to produce an all-solid battery. As a pressure molding method, there are a hot press performed by heating and a cold press not heated, but a cold press can also sufficiently mold.
In addition, the present invention includes a molded article obtained by pressure-forming the LGPS-based solid electrolyte of the present invention. The molded article is suitably used as an all-solid battery. The present invention also includes a method for manufacturing an all-solid battery, including a step of pressure-forming the LGPS-based solid electrolyte of the present invention.

Hereinafter, the present embodiment will be described in more detail with reference to examples, but the present embodiment is not limited to these examples.
(Example 1)
<Method for producing β-Li ₃ PS ₄ >
In a glove box under an argon atmosphere, Li ₂ S (manufactured by Aldrich, purity 99.8%) and P ₂ S ₅ (manufactured by Aldrich, purity 99%) were added to Li ₂ S: P ₂ S ₅ = 1. It was weighed to give a 5: 1 molar ratio. _{Next, (Li 2 S + P 2} S 5) in tetrahydrofuran to a concentration of 10 wt% of (Wako Pure Chemical Industries, Ltd., super dehydrated grade) with respect _to, Li 2 _S, in addition to the order of P 2 _{S 5,} at room temperature Mix under for 12 hours. The slurry gradually dissolved to obtain a nearly uniform solution containing a small amount of insolubles.
Li ₂ S is further added to the obtained solution so that the total raw material composition including the above becomes Li ₂ S: P ₂ S ₅ = 3: 1 by weight, and mixed at room temperature for 12 hours, A precipitate was obtained. The resulting filter was dried under vacuum at 150 ° C. for 4 hours to obtain β-Li ₃ PS ₄ having a peak at 420 ± 10 cm ⁻¹ in Raman measurement. A series of operations was performed in a glove box under an argon atmosphere.

<Method for producing Li ₄ SnS ₄ >
In a glove box under an argon atmosphere, Li ₂ S (manufactured by Aldrich, purity 99.8%) and SnS ₂ (Santa Cruz Biotechnology, Inc.> 98 Weight%) were converted into Li ₂ S: SnS ₂ = 2: 1. , And mixed in an agate mortar.
Next, the obtained mixture was put into a 45 mL zirconia pot, and further, zirconia balls (“YTZ” manufactured by Nikkato Co., Ltd., φ10 mm, 18 pieces) were put therein, and the pot was completely sealed. The pot was attached to a planetary ball mill (“P-7” manufactured by Fritsch), and mechanical milling was performed at a rotation speed of 370 rpm for 4 hours, and a Li ₄ SnS ₄ amorphous having a peak at 346 ± 10 cm ⁻¹ in Raman measurement. I got a body.

<Synthesis of LGPS (Li ₁₀ SnP ₂ S ₁₂ )>
In a glove box under an argon atmosphere, the above β-Li ₃ PS ₄ was stirred in acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) to a concentration of 10 wt%, whereby acetonitrile in which Li ₃ PS ₄ was dispersed was obtained. A suspension (slurry liquid) was obtained. Next, an acetonitrile-ethanol mixed solution was prepared by preparing a solution in which the above Li ₄ SnS ₄ was dissolved in ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) so as to have a concentration of 10 wt% and mixing with an acetonitrile suspension. Was prepared. At this time, the composition ratio in the mixed solution was adjusted such that the molar ratio of β-Li ₃ PS ₄ : Li ₄ SnS _{4 was} 2: 1. When mixed at room temperature for 10 minutes, the slurry was dissolved to obtain a uniform solution. The precursor was obtained by performing vacuum drying of the obtained homogeneous solution at 180 ° C. for 3 hours. A series of operations was performed in a glove box under an argon atmosphere.
The obtained precursor was put in a glass reaction tube and set in an electric tubular furnace. The reaction tube was heated at the center of the electric tube furnace at the portion where the sample was placed, and was almost at room temperature with the other portion connected to the argon blowing line protruding from the electric tube furnace. By baking at 550 ° C. for 8 hours, Li ₁₀ SnP ₂ S ₁₂ crystals were obtained.

(Example 2)
Li ₃ PS ₄ is dispersed by stirring the above β-Li ₃ PS ₄ in tetrahydrofuran (THF: manufactured by Wako Pure Chemical Industries, Ltd.) in a glove box under an argon atmosphere so that the concentration becomes 10 wt%. A THF suspension was obtained. Next, a solution prepared by dissolving the above Li ₄ SnS ₄ in ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) so as to have a concentration of 10 wt% is prepared, and mixed with a THF suspension to prepare a THF-ethanol mixed solution. Was prepared. At this time, the composition ratio in the mixed solution was adjusted so as to have a molar ratio of β-Li ₃ PS ₄ : Li ₄ SnS ₄ = 2: 1. When mixed at room temperature for 10 minutes, the slurry was dissolved to obtain a uniform solution. The precursor was obtained by subjecting the obtained homogeneous solution to vacuum drying at 150 ° C. for 3 hours. A series of operations was performed in a glove box under an argon atmosphere.
The obtained precursor was operated in the same manner as in Example 1 to obtain a Li ₁₀ SnP ₂ S ₁₂ crystal.

(Example 3)
In a glove box under an argon atmosphere, the above-mentioned β-Li ₃ PS ₄ was stirred in ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) so as to have a concentration of 10 wt%, whereby Li ₃ PS ₄ was dispersed. An ethyl acetate suspension was obtained. Next, a solution in which the above Li ₄ SnS ₄ was dissolved in ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) to a concentration of 10 wt% was prepared, and mixed with an ethyl acetate suspension to prepare ethyl acetate-ethanol. A mixture was prepared. At this time, the composition ratio in the mixed solution was adjusted so as to have a molar ratio of β-Li ₃ PS ₄ : Li ₄ SnS ₄ = 2: 1. When mixed at room temperature for 10 minutes, the slurry was dissolved to obtain a uniform solution. The obtained homogeneous solution was vacuum-dried at 170 ° C. for 3 hours to obtain a precursor. A series of operations was performed in a glove box under an argon atmosphere.
The obtained precursor was operated in the same manner as in Example 1 to obtain a Li ₁₀ SnP ₂ S ₁₂ crystal.

(Example 4)
In a glove box under an argon atmosphere, the above β-Li ₃ PS ₄ was stirred in acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) to a concentration of 10 wt%, whereby acetonitrile in which Li ₃ PS ₄ was dispersed was obtained. A suspension was obtained. Next, a solution was prepared by dissolving the above Li ₄ SnS ₄ in 1-propanol (manufactured by Wako Pure Chemical Industries, Ltd.) so as to have a concentration of 10 wt%, and mixed with an acetonitrile suspension to prepare acetonitrile-1. -A propanol mixture was prepared. At this time, the composition ratio in the mixed solution was adjusted so as to have a molar ratio of β-Li ₃ PS ₄ : Li ₄ SnS ₄ = 2: 1. When mixed at room temperature for 10 minutes, the slurry was dissolved to obtain a uniform solution. The precursor was obtained by subjecting the obtained homogeneous solution to vacuum drying at 150 ° C. for 3 hours. A series of operations was performed in a glove box under an argon atmosphere.
The obtained precursor was operated in the same manner as in Example 1 to obtain a Li ₁₀ SnP ₂ S ₁₂ crystal.

(Reference Example 1)
In the LGPS synthesis, the raw materials were weighed out so as to have a molar ratio of Li ₂ S: P ₂ S ₅ : GeS ₂ = 5: 1: 1 and mixed in an agate mortar. Next, the obtained mixture was put into a 45 mL zirconia pot, and further, zirconia balls (“YTZ” manufactured by Nikkato Co., Ltd., φ10 mm, 18 pieces) were put therein, and the pot was completely sealed. The pot was attached to a planetary ball mill (“P-7” manufactured by Fritsch), and mechanical milling was performed at a rotation speed of 370 rpm for 40 hours to obtain an amorphous body.
The obtained amorphous body was put in a glass reaction tube and placed in an electric tubular furnace. By firing at 550 ° C. for 8 hours in an argon atmosphere, Li ₁₀ GeP ₂ S ₁₂ crystals were synthesized.

<X-ray diffraction measurement>
The ion conductor powders obtained in Examples 1 to 4 and Reference Example 1 were subjected to X-ray diffraction measurement (“X'Pert3 Powder” manufactured by PANalytical, CuKα: λ) at room temperature (25 ° C.) under an Ar atmosphere. = 1.5405 °).

The measurement results of Examples 1 to 4 and Reference Example 1 are shown in FIG.
As shown in FIG. 3, in Examples 1 to 4, at least 2θ = 19.80 ° ± 0.50 °, 20.10 ° ± 0.50 °, 26.60 ° ± 0.50 °, and 29 A diffraction peak was observed at .10 ° ± 0.50 °. The XRD pattern of the Li ₁₀ SnP ₂ S ₁₂ sample of Example 1 was identical to that of Li ₁₀ GeP ₂ S ₁₂ obtained by the standard synthesis method of Reference Example 1.

<Lithium ion conductivity measurement>
The ionic conductors obtained in Examples 1 to 4 and Reference Example 1 were subjected to uniaxial molding (240 MPa) to obtain a disk having a thickness of about 1 mm and a diameter of 10 mm. AC impedance measurement by a four-terminal method using an indium electrode at room temperature (25 ° C.) and at a temperature range of 30 ° C. to 100 ° C. and at a temperature range of −20 ° C. at 10 ° C. intervals (“SI1260 IMPEDANCE / GAIN-PHASE ANALYZER” manufactured by Solartron). )) To calculate the lithium ion conductivity.
Specifically, the sample was placed in a thermostat set at 25 ° C., held for 30 minutes, and then measured for lithium ion conductivity. Then, the thermostat was heated from 30 ° C. to 100 ° C. in increments of 10 ° C. , And the ionic conductivity was measured. After finishing the measurement at 100 ° C., the temperature of the thermostat was lowered by 10 ° C. from 90 ° C. to 30 ° C., and the temperature was kept at each temperature for 40 minutes, and then the lithium ion conductivity was measured. Next, the lithium ion conductivity of the sample after being kept in a thermostat set at 25 ° C. for 40 minutes was measured. Thereafter, the temperature of the thermostatic bath was lowered by 10 ° C. from 20 ° C. to −20 ° C., and the temperature was kept at each temperature for 40 minutes, and then the lithium ion conductivity was measured. The measurement frequency range was 0.1 Hz to 1 MHz, and the amplitude was 50 mV. FIG. 4 shows the measurement results of the lithium ion conductivity at the time of temperature decrease.

<Raman spectroscopy>
(1) Sample preparation A measurement sample was prepared using a sealed container having quartz glass (Φ60 mm, thickness 1 mm) as an optical window on the upper part. After holding the sample in contact with the quartz glass in a glove box under an argon atmosphere, the container was closed and taken out of the glove box, and Raman spectroscopy was performed.
(2) Measurement conditions Measurement was performed using a laser Raman spectrophotometer NRS-5100 (manufactured by JASCO Corporation) at an excitation wavelength of 532.15 nm and an exposure time of 5 seconds.

Example 1 of _<β-Li 3 PS ₄ of production method> In the resulting _{β-Li 3} PS _4, the results of Raman spectroscopy of _Li 4 SnS ₄ obtained in _<Production method of Li 4 SnS _4> As shown in FIG. In Raman spectroscopy, in _β-Li 3 PS ₄ obtained in <Production method of _β-Li 3 PS _4>, peaks at least 420 ± 10 cm ^-1 _is obtained in _<Production method of Li 4 SnS _4> With the obtained Li ₄ SnS ₄ , a peak was obtained at least at 346 ± 10 cm ⁻¹ .

DESCRIPTION OF SYMBOLS 1 Positive electrode layer 2 Solid electrolyte layer 3 Negative electrode layer 10 All solid state battery

Claims (11)

A slurry liquefaction step of preparing a slurry liquid by stirring Li ₃ PS ₄ in an organic solvent;
A uniform solution preparation step of preparing a uniform solution by dissolving Li ₄ SnS ₄ in an alcohol-based solvent;
A mixed uniform solution preparation step of preparing a mixed uniform solution by mixing the slurry liquid and the uniform solution,
A drying step of removing a mixed solvent of the organic solvent and the alcohol-based solvent from the mixed homogeneous solution to obtain a precursor,
A heat treatment step of subjecting the precursor to heat treatment at 200 to 700 ° C. to obtain an LGPS-based solid electrolyte. The method according to claim 1, wherein the Li ₃ PS ₄ has a peak at 420 ± 10 cm ⁻¹ in Raman measurement, and the Li ₄ SnS ₄ has a peak at 346 ± 10 cm ⁻¹ in Raman measurement.   3. The method according to claim 1, wherein the organic solvent is at least one selected from the group consisting of tetrahydrofuran, acetonitrile, ethyl acetate, and methyl acetate.   The method according to any one of claims 1 to 3, wherein the alcohol-based solvent is at least one selected from the group consisting of methanol, ethanol, 1-propanol, and 1-butanol.   The method according to any one of claims 1 to 4, wherein the temperature in the drying step is 60 to 280C.   In the X-ray diffraction (CuKα: λ = 1.5405 °), at least 2θ = 19.80 ° ± 0.50 °, 20.10 ° ± 0.50 °, 26.60 ° ± The production method according to any one of claims 1 to 5, having peaks at 0.50 ° and 29.10 ° ± 0.50 °. The diffraction intensity of the peak of the 2θ = 29.10 ° ± 0.50 ° and _{I A,} the diffraction intensity of the peak of 2θ = 27.33 ° ± 0.50 ° when the _{I B, I B} / _{I The} method according to claim 6, wherein the value of _A is less than 0.50. The LGPS solid electrolyte comprises an octahedron O composed of Li element and S element, a tetrahedron T ₁ composed of one or more elements selected from the group consisting of P and Sn and S element, a P element and and a tetrahedron T ₂ composed of S elements, the tetrahedron T ₁ and the octahedron O share a crest main crystal structure that share vertices the tetrahedron T ₂ and the octahedron O is The production method according to any one of claims 1 to 7, wherein the method comprises:   The method according to any one of claims 1 to 8, wherein the heat treatment step is performed in an inert gas atmosphere.   A molded product obtained by press-molding the LGPS-based solid electrolyte obtained by the production method according to claim 1.   A method for producing an all-solid-state battery, comprising a step of pressure-forming the LGPS-based solid electrolyte obtained by the production method according to claim 1.