Method for producing Sn-containing sulfide solid electrolyte, and Sn-containing sulfide solid electrolyte

Abstract

According to one embodiment, the present invention provides a method for producing an Sn-containing sulfide solid electrolyte, the method comprising: a step for preparing a raw material mixture containing Li element, Sn element, P element, and S element; and a step for obtaining a Sn-containing sulfide solid electrolyte by subjecting the starting material mixture to a mechanical polishing treatment, in which heat treatment is not performed after the mechanical polishing treatment.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a Sn-containing sulfide solid electrolyte and a novel Sn-containing sulfide solid electrolyte. BACKGROUND

[0002] In recent years, the demand for lithium ion secondary batteries has been increasing in applications such as portable information terminals, portable electronic devices, electric vehicles, hybrid electric vehicles, and stationary energy storage systems. However, the current lithium ion secondary batteries use flammable organic solvents as electrolytes, and require strong outer packaging to prevent leakage of the organic solvent. In addition, in the field of portable personal computers and the like, there are constraints on the device structure, such as the need to adopt a structure that takes precautions against the risk of electrolyte leakage.

[0003] Furthermore, as the use of lithium ion secondary batteries has expanded to mobile bodies such as automobiles and aircraft, stationary lithium ion secondary batteries are required to have a large capacity. Under such circumstances, safety is often given more importance than ever, and more efforts are being made to develop all-solid-state lithium ion secondary batteries that do not use harmful substances such as organic solvents.

[0004] As a solid electrolyte in all-solid-state lithium ion secondary batteries, the use of, for example, oxides, phosphoric acid compounds, organic polymers, sulfides, and the like has been studied.

[0005] Among these solid electrolytes, sulfides have the characteristics of high ionic conductivity and relatively softness, thus being easy to form a solid-solid interface. Furthermore, the development of practical solid electrolytes that are also stable with active materials has been advancing.

[0006] Among sulfide-based solid electrolytes, Sn-containing sulfide solid electrolytes are also highly expected for practical use because of their excellent ionic conductivity and water resistance, and low cost (Non-Patent Literature 1). As Sn-containing sulfide-based solid electrolytes, for example, Li4SnS4, which has the advantage of high water resistance, can be cited. On the other hand, the ionic conductivity of Li4SnS4 is on the order of 10 ﹣5 ~ 10 ﹣4 S / cm, and its low ionic conductivity is a technical problem. In addition, it has been reported that replacing part of the Sn elements in the Li4SnS4 skeleton with other elements (Sb, As, etc.) will improve the ionic conductivity (Non-Patent Literatures 2 and 3), but even in this case, the ionic conductivity is limited to the order of 10 ﹣4 S / cm.

[0007] Moreover, there are reports that by adding a P component to a Sn-containing raw material, performing amorphization (glassification) treatment by mechanical grinding, and then performing a heat treatment, a solid electrolyte (glass-ceramic) having high ionic conductivity can be obtained (Patent Literature 1 and Non-Patent Literature 4). However, since the heat treatment process requires a large amount of energy and is costly. In addition, in the case of sulfide-based solid electrolytes, there is also a problem that impurities are generated due to the volatilization of sulfur at the time of heat treatment, and a solid electrolyte having a desired composition cannot be obtained.

[0008] Prior Art Documents Patent Literature Patent Literature 1: Japanese Patent Application Publication No. 2022-139139 Non-Patent Literature Non-Patent Literature 1: Journal of Power Sources, 396, 2018, p.824-830 Journal of Power Sources , 396, 2018, p.824-830 Non-Patent Literature 2: Energy & Environmental Science, 41, 2020, p.171-176 Journal of Energy Chemistry , 41, 2020, p.171-176 Non-Patent Literature 3: Energy & Environmental Science, 7, 2014, p.1053-1058 Energy Environ. Sci. , 2014, 7, p.1053-1058 Non-Patent Literature 4: International Journal of Applied Ceramic Technology, 47, 2021, p.28377-28383 Ceramics International , 47, 2021, p.28377-28383 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION In the above background, there is a need for improvement in the manufacturing method of Sn-containing sulfide solid electrolytes.

[0010] TECHNICAL SOLUTION FOR SOLVING THE PROBLEMS In order to solve the above technical problems related to sulfide-based solid electrolytes, the inventors of the present invention have conducted intensive research and as a result, have found a method for manufacturing a Sn-containing sulfide solid electrolyte without heat treatment after mechanical grinding treatment of a raw material mixture.

[0011] The present invention is, for example, the following technical solution.

[0012] [1] A method for producing a Sn-containing sulfide solid electrolyte, comprising: a step of preparing a raw material mixture containing Li element, Sn element, P element, and S element; and a step of obtaining a Sn-containing sulfide solid electrolyte by subjecting the raw material mixture to mechanical milling treatment, wherein no heat treatment is performed after the mechanical milling treatment.

[0013] [1-1] The method according to the above [1], wherein the mixing ratio of the Li element, the Sn element, the P element, and the S element in the raw material mixture satisfies Li u Sn v P2S y with a composition of (6≤u≤14; 0.8≤v≤2.1; 9≤y≤16).

[0014] [2] The method according to the above [1] or [1-1], wherein the Sn-containing sulfide solid electrolyte has a lithium ion conductivity of 8.0 x 10 ﹣4 S / cm or more.

[0015] [3] The method according to any one of [1] to [2], wherein the Sn-containing sulfide solid electrolyte has a crystalline phase of an orthorhombic crystal system.

[0016] [4] The method according to any one of [1] to [3], wherein the Sn-containing sulfide solid electrolyte has diffraction peaks at least at 2θ = 14.08° ± 0.50°, 17.10° ± 0.50°, 17.89° ± 0.50°, 19.83° ± 0.50°, 25.66° ± 0.50°, 26.58° ± 0.50°, and 29.07° ± 0.50° in X-ray diffraction (CuKα: λ = 1.5405 Å).

[0017] [5] The method according to any one of [1] to [4], wherein the Sn-containing sulfide solid electrolyte has peaks at least at 415 ± 10 cm ﹣1 and 340 ± 10 cm ﹣1 in Raman spectrum measurement.

[0018] [6] The production method according to any one of [1] to [5], wherein the Sn-containing sulfide solid electrolyte contains, as a main body, a crystal structure having an octahedral O composed of Li element and S element, a tetrahedral T1 composed of one or more elements selected from P and Sn and S element, and a tetrahedral T2 composed of P element and S element, the tetrahedral T1 sharing an edge with the octahedral O, and the tetrahedral T2 sharing a vertex with the octahedral O.

[0019] [7] The method according to any one of [1] to [6], wherein the mechanical polishing is dry mechanical polishing.

[0020] [8] The method according to any one of [1] to [6], wherein the mechanical polishing is wet mechanical polishing.

[0021] [9] The method according to [8], wherein the wet mechanical polishing is performed in the presence of a hydrocarbon solvent.

[0022]

[10] The method according to [9], wherein the hydrocarbon solvent is selected from the group consisting of heptane, hexane, toluene and xylene.

[0023]

[11] The method according to any one of [1] to

[10] , wherein the mechanical polishing treatment is performed using a planetary ball mill under a condition of a gravity value of 27.5 G or more, the gravity value being calculated according to the following formula.

[0024] Gravity value (G) = 1118 x revolution radius (m) x rotation speed (rpm) 2 x 10 ﹣6 [11-2] The method according to any one of [1] to

[11] , wherein the mechanical polishing treatment is performed under a rotation speed of 100 to 1200 rpm for 0.1 to 300 hours.

[0025]

[12] A Sn-containing sulfide solid electrolyte containing Li element, Sn element, P element and S element, and having a crystalline phase of an orthorhombic crystal system, and having peaks at least at 2Θ = 14.08° ± 0.50°, 17.10° ± 0.50°, 17.89° ± 0.50°, 19.83° ± 0.50°, 25.66° ± 0.50°, 26.58° ± 0.50° and 29.07° ± 0.50° in X-ray diffraction (CuKα: λ = 1.5405 Å).

[0026]

[13] The Sn-containing sulfide solid electrolyte according to

[12] , wherein the sulfide solid electrolyte has a half-value width of a peak at 2Θ = 19.83° ± 0.50° in X-ray diffraction (CuKα: λ = 1.5405 Å) of 0.80 to 1.70°, and a half-value width of a peak at 2Θ = 29.07° ± 0.50° of 0.70 to 1.40°.

[0027]

[14] The Sn-containing sulfide solid electrolyte according to

[12] or

[13] , wherein the Sn-containing sulfide solid electrolyte has a lithium ion conductivity of 8.0 x 10 ﹣4 S / cm or more.

[0028]

[15] The Sn-containing sulfide solid electrolyte according to any one of

[12] to

[14] , wherein the Sn-containing sulfide solid electrolyte has peaks at least at 415 ± 10 cm ﹣1 and 340 ± 10 cm ﹣1 in Raman spectrum measurement.

[0029]

[16] The Sn-containing sulfide solid electrolyte according to any one of

[12] to

[15] , wherein the Sn-containing sulfide solid electrolyte contains a crystal structure having an octahedral O composed of Li and S elements, a tetrahedral T1 composed of one or more elements selected from P and Sn and S elements, and a tetrahedral T2 composed of P and S elements as a main body, and the tetrahedral T1 shares an edge with the octahedral O, and the tetrahedral T2 shares a vertex with the octahedral O.

[0030]

[17] An all-solid battery containing the Sn-containing sulfide solid electrolyte according to any one of

[12] to

[16] .

[0031] Effects of Invention According to the present application, a method for producing a Sn-containing sulfide solid electrolyte without a heating treatment after a mechanical polishing treatment can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a schematic diagram showing a crystal structure of a Sn-containing sulfide solid electrolyte according to an embodiment of the present application.

[0033] Figure 2 is a schematic diagram showing a crystal structure of a Sn-containing sulfide solid electrolyte according to an embodiment of the present application.

[0034] Figure 3 is a graph showing the results of X-ray diffraction measurement of crystals obtained in Examples and Reference Examples.

[0035] Figure 4 is a graph showing the results of Raman spectrum measurement of crystals obtained in Examples and Reference Examples. DETAILED DESCRIPTION

[0036] Hereinafter, an embodiment of the present application will be specifically described. Note that the materials and configurations and the like described below are not intended to limit the present application, and various modifications can be made within the scope of the gist of the present application.

[0037] One embodiment of the present application relates to a method for producing a Sn-containing sulfide solid electrolyte, characterized by comprising: a step of preparing a raw material mixture containing Li element, Sn element, P element, and S element; and a step of subjecting the raw material mixture to mechanical milling treatment to obtain a Sn-containing sulfide solid electrolyte, wherein no heating treatment is performed after the mechanical milling treatment. Conventionally, as a method for producing a sulfide solid electrolyte, a method of obtaining a high ionic conductor by performing heating treatment to induce phase transition (phase transition from glass to glass ceramic, or phase transition from crystal to crystal) after mixing a plurality of raw materials to achieve a glass state or a crystal state has been generally employed. However, as described above, this method has problems of high cost due to consumption of a large amount of energy required for the heating treatment step, and generation of impurities due to volatilization of sulfur at the time of heating treatment, and thus a solid electrolyte having a desired composition cannot be obtained. In addition, the heating treatment step (firing) in the production of a sulfide solid electrolyte needs to be performed under conditions avoiding exposure to the atmosphere, and thus a device for this purpose is also required.

[0038] Further, grain growth and sintering of the solid electrolyte in the heating treatment step also arise as problems. In order to achieve high energy density and high power of an all-solid-state battery, it is necessary to reduce the interface impedance between the solid electrolyte layer and the electrode layer. In order to achieve reduction of such impedance, a method of reducing the particle diameter of the solid electrolyte has been proposed (for example, Japanese Patent Application Publication No. 2008-00459), but even in the case where a material having a small particle diameter has been obtained at a stage before the heating treatment, grain growth and sintering occur due to the heating treatment at a high temperature, and thus a problem of increase in the particle diameter arises.

[0039] Therefore, in the background of the need for improvement in the production method of a Sn-containing sulfide solid electrolyte, the present inventors have intensively studied, and as a result, have found a method of producing a Sn-containing sulfide solid electrolyte without performing heating treatment after mechanical milling treatment. Since no heating treatment is performed, there are no problems such as the cost problem and the problem of generation of impurities described above. In addition, since there is also no problem of grain growth and sintering due to the heating step, a solid electrolyte having a small particle diameter can be produced (high energy density and high power are achieved), and it is expected that the ionic conductivity is improved. Further, the greatest advantage is that a Sn-containing sulfide solid electrolyte can be produced by a simple method regardless of anything.

[0040] Further, it has been confirmed that the Sn-containing sulfide solid electrolyte has high water resistance and is capable of suppressing generation of hydrogen sulfide, and is thus a material with high safety. Therefore, in the production of the Sn-containing sulfide solid electrolyte according to the embodiment of the present application, it is not necessary to prepare a low dew point environment, and in this respect, it is also possible to produce the sulfide solid electrolyte at a lower cost. Further, according to the embodiment of the present application, it is also possible to produce the sulfide solid electrolyte by mixing for a short time.

[0041] Hereinafter, the constituent elements of the present application will be described in order.

[0042] 1. Method for producing Sn-containing sulfide solid electrolyte According to one embodiment of the present application, there is provided a method for producing a Sn-containing sulfide solid electrolyte, comprising: a step (step 1) of preparing a raw material mixture containing Li element, Sn element, P element, and S element; and a step (step 2) of subjecting the raw material mixture to mechanical milling treatment to obtain a Sn-containing sulfide solid electrolyte, wherein no heating treatment is performed after the mechanical milling treatment.

[0043] (1) Step 1 In step 1, a raw material mixture containing Li element, Sn element, P element, and S element is first prepared. The raw materials and the mixing method are not particularly limited as long as a mixture containing these elements can be obtained, and for example, lithium sulfide (Li2S or the like), tin sulfide (SnS, SnS2, or the like), phosphorus sulfide (P2S3, P2S5, P4S3, P4S5, P4S7, or the like), metallic lithium (Li), phosphorus (P), metallic tin (Sn), sulfur (S), or the like can be used. Among these, it is preferable to use Li2S, SnS2, and P2S5 to prepare the raw material mixture. Because these raw materials are industrially produced raw materials, they are excellent in easiness of availability. As these raw materials, commercially available products can be used, and it is preferable to use high-purity products.

[0044] The raw material mixture can also contain other elements. As such other elements, there can be mentioned silicon (Si) element, germanium (Ge) element, halogen element (fluorine (F) element, chlorine (Cl) element, bromine (Br) element, iodine (I) element), oxygen (O) element, and the like. Note that these elements can be contained alone or two or more of them can be contained. As raw materials containing these elements, there can be mentioned, for example, silicon sulfide (SiS2), silicon (Si), silicon dioxide (SiO2), and the like as raw materials containing Si element; germanium sulfide (GeS2), germanium (Ge), germanium dioxide (GeO2), and the like as raw materials containing Ge element; phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), phosphorus pentabromide (PBr5), lithium bromide (LiBr), sodium bromide (NaBr), lithium iodide (LiI), sodium iodide (NaI), magnesium iodide (MgI2), phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), phosphorus pentabromide (PBr5), and the like as raw materials containing halogen; lithium oxide (Li2O), sodium oxide (Na2O), phosphorus pentoxide (P2O5), silicon dioxide (SiO2), germanium dioxide (GeO2), tin (II) oxide (SnO), tin (IV) oxide (SnO2), tin (IV) oxide (SnO3), and the like as raw materials containing O element, and the like. These raw materials can be used alone or two or more of them can be used in combination.

[0045] The mixing ratio of the Li element, the Sn element, the P element, and the S element in the raw material mixture is preferably Li u Sn v P2S y (6 ≤ u ≤ 14; 0.8 ≤ v ≤ 2.1; 9 ≤ y ≤ 16).

[0046] The mixing method is preferably, but not particularly limited to, mixing under an inert gas (for example, argon) atmosphere. As the mixing time, it is only necessary to be a time that ensures uniformity of the mixture. The time depends on the manufacturing scale, and for example, a uniform mixture can be obtained by mixing for 0.1 to 24 hours.

[0047] (2) Step 2 In Step 2, the raw material mixture obtained in Step 1 is subjected to mechanical milling treatment to obtain a Sn-containing sulfide solid electrolyte.

[0048] The mechanical grinding treatment, also referred to as a mechanochemical treatment, is a method of grinding and mixing a raw material in a state where mechanical energy is applied. According to this method, grinding and mixing is performed by applying mechanical impact and friction to the raw material, causing the raw material substances to come into contact with each other violently and to be finely divided (micronized), and causing the raw material to react. That is, mixing, pulverization, and reaction occur simultaneously at this time. Therefore, the raw material can be caused to react more reliably without being heated to a high temperature. By using the mechanical grinding treatment, a metastable crystal structure that cannot be obtained by conventional heat treatment can be produced.

[0049] As the mechanical grinding treatment, a treatment using a mechanical pulverization device such as a ball mill, a bead mill, a rod mill, a vibration mill, a disk mill, a hammer mill, a jet mill, or the like can be cited.

[0050] The mechanical grinding treatment can be a wet treatment using a solvent or a dry treatment not using a solvent. In the case of wet mechanical grinding, a solvent commonly used in the field can be used, and for example, a hydrocarbon solvent, a nitrile solvent, an ester solvent, an ether solvent, or the like can be used. As the hydrocarbon solvent, for example, heptane, hexane, toluene, xylene, or the like can be cited; as the nitrile solvent, for example, acetonitrile, isobutyronitrile, benzonitrile, or the like can be cited; as the ester solvent, for example, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or the like can be cited; and as the ether solvent, for example, diethyl ether, tetrahydrofuran (THF), 1,4-dioxane, or the like can be cited. Among these, a hydrocarbon solvent is preferred, and in particular, heptane, hexane, toluene, xylene, and more preferably heptane is preferred. Depending on the solvent, deterioration can be caused by reaction with the sulfide raw material during the mechanical grinding, but by using a solvent having low reactivity (for example, the solvents described above), deterioration of the raw material during wet mechanical grinding can be suppressed.

[0051] By performing the wet mechanical grinding treatment, a solid electrolyte having a smaller particle diameter than that of the dry treatment can be obtained. As described above, when a solid electrolyte having a small particle diameter is used, the interface resistance between the solid electrolyte layer and the electrode layer is reduced, and thus high energy density and high power of the solid electrolyte battery, and the like are expected.

[0052] In the case where the wet mechanical grinding treatment is employed, the solvent removal step and / or the drying step can be appropriately performed after the mechanical grinding treatment. These steps can be performed according to the methods generally used in the art, and for example, heating drying, vacuum drying can be mentioned. The optimum temperature thereof varies depending on the kind of solvent, but by applying a temperature sufficiently higher than the boiling point of the solvent, the solvent removal time can be shortened. The temperature during the removal of the solvent is preferably in the range of 60 to 280°C, more preferably 100 to 250°C. Note that by removing the solvent under reduced pressure by vacuum drying or the like, not only the temperature at the time of removal of the solvent can be lowered, but also the time required can be shortened. Further, by introducing an inert gas such as nitrogen, argon or the like having a sufficiently small amount of moisture, the time required for the removal of the solvent can also be shortened.

[0053] The conditions of the mechanical grinding treatment are preferably, but not particularly limited to, a treatment at a rotation speed of 100 to 1200 rpm for 0.1 to 300 hours. The rotation speed is more preferably 200 to 1000 rpm, and particularly preferably 400 to 800 rpm. The mechanical grinding treatment time is more preferably 1 to 100 hours, and particularly preferably 3 to 50 hours.

[0054] In particular, in the case where the mechanical grinding treatment is performed using a planetary ball mill, it is preferable to perform the treatment under conditions of a gravitational value of 27.5 G or more.

[0055] Note that the gravitational value is calculated according to the following formula.

[0056] Gravitational value (G) = 1118 x revolution radius (m) x rotation speed (rpm) 2 x 10 -6 Here, the revolution radius refers to the distance from the end portion of the base of the planetary ball mill to the center of the fixed position of the zirconia crucible.

[0057] By performing the mechanical grinding treatment under the conditions of the above gravitational value, a solid electrolyte having a higher ionic conductivity can be obtained. The gravitational value is preferably 27.5 G or more (for example, 27.5 to 94.7 G), and more preferably 40.0 G or more (for example, 40.0 to 94.7 G, 45.0 to 94.7 G, 48.0 to 94.7 G, etc.).

[0058] In the case where the mechanical grinding treatment is performed using a planetary ball mill, the bead diameter is preferably φ 0.1 to 10 mm, and more preferably φ 1 to 10 mm. By performing the mechanical grinding treatment under these conditions, a solid electrolyte having a higher ionic conductivity can be obtained. The mechanical grinding treatment is preferably performed in an environment of an inert gas (for example, argon).

[0059] The Sn-containing sulfide solid electrolyte obtained by the above method can be used directly without performing a heating step.

[0060] 2. Sn-containing sulfide solid electrolyte The Sn-containing sulfide solid electrolyte obtained by the above method has a novel crystal structure. That is, according to one embodiment of the present application, there is provided a Sn-containing sulfide solid electrolyte having a crystalline phase of an orthorhombic structure. Here, the orthorhombic structure refers to a crystal structure obtained by stretching a hexagonal lattice in two of the three orthogonal pairs by different multiples.

[0061] Further, the Sn-containing sulfide solid electrolyte of the present application has diffraction peaks at least at 2Θ = 14.08° ± 0.50°, 17.10° ± 0.50°, 17.89° ± 0.50°, 19.83° ± 0.50°, 25.66° ± 0.50°, 26.58° ± 0.50° and 29.07° ± 0.50° in X-ray diffraction (CuKα: λ = 1.5405 Å). Preferably, the Sn-containing sulfide solid electrolyte of the present application has diffraction peaks at least at 2Θ = 14.08° ± 0.40°, 17.10° ± 0.40°, 17.89° ± 0.40°, 19.83° ± 0.40°, 25.66° ± 0.40°, 26.58° ± 0.40° and 29.07° ± 0.40° in X-ray diffraction (CuKα: λ = 1.5405 Å). More preferably, the Sn-containing sulfide solid electrolyte of the present application has diffraction peaks at least at 2Θ = 14.08° ± 0.30°, 17.10° ± 0.30°, 17.89° ± 0.30°, 19.83° ± 0.30°, 25.66° ± 0.30°, 26.58° ± 0.30° and 29.07° ± 0.30° in X-ray diffraction (CuKα: λ = 1.5405 Å).

[0062] The Sn-containing sulfide solid electrolyte of the present application tends to have a larger half-peak width of the X-ray diffraction peak compared to the LGPS-based solid electrolyte known in the art. Here, the half-peak width refers to the width of the diffraction peak at the intensity 1 / 2 height of the diffraction peak. Generally, the half-peak width of a peak derived from a crystal tends to be small, while the half-peak width of a peak derived from a glass tends to be large.

[0063] The Sn-containing sulfide solid electrolyte of the present embodiment preferably has a peak at 2θ = 19.83° ± 0.50° in the X-ray diffraction measurement results (CuKα: λ = 1.5405 Å) with a half-peak width of 0.80 to 1.70°, more preferably 0.85 to 1.65°, particularly preferably 0.90 to 1.60° or 1.00 to 1.55°. In addition, the Sn-containing sulfide solid electrolyte preferably has a peak at 2θ = 29.07° ± 0.50° with a half-peak width of 0.70 to 1.40°, more preferably 0.75 to 1.35°, particularly preferably 0.80 to 1.30° or 0.90 to 1.20°. The half-peak width is calculated by fitting the diffraction peak data obtained by the X-ray diffraction measurement and performing data processing using crystal structure analysis software SmartLab studio II.

[0064] As described above, since the Sn-containing sulfide solid electrolyte of the present embodiment does not undergo a heating process, it is inferred to have a crystal structure different from the LGPS solid electrolyte known in the art. Since the Sn-containing sulfide solid electrolyte having the above-described crystal structure has low crystallinity, it has an advantage of excellent moldability when an electrode layer, a solid electrolyte layer, etc. are manufactured using the solid electrolyte.

[0065] In addition, the Sn-containing sulfide solid electrolyte of the present embodiment preferably has peaks at least at 415 ± 10 cm ﹣1 and 340 ± 10 cm ﹣1 in the Raman spectrum measurement. These peaks indicate that the crystal structure has a PS4 3- skeleton and a SnS4 4- skeleton.

[0066] In yet another embodiment, the Sn-containing sulfide solid electrolyte preferably contains, as a main body, a crystal structure having an octahedral O composed of Li element and S element, a tetrahedral T1 composed of one or more elements selected from P and Sn and S element, and a tetrahedral T2 composed of P element and S element, and the tetrahedral T1 shares an edge with the octahedral O, and the tetrahedral T2 shares a vertex with the octahedral O, as shown in Figure 1 . It is inferred that just because the crystal has such a structure, a higher ionic conductivity can be obtained.

[0067] The Sn-containing sulfide solid electrolyte of the present embodiment can be suitably used as a solid electrolyte material for, for example, a lithium ion secondary battery. The Sn-containing sulfide solid electrolyte of the present embodiment preferably has, for example, 8.0 × 10 -4 S / cm or more (for example, 8.0 × 10 -4 to 3.0 × 10 -3 S / cm), and is preferably 0.5 × 10 -3S / cm or more (e.g. 0.5×10 -3 S / cm~3.0×10 -3 S / cm), more preferably 1.0×10 -3 S / cm or more (e.g. 1.0×10 -3 ~3.0×10 -3 S / cm, 1.1×10 -3 ~3.0×10 -3 S / cm), particularly preferably 1.5×10 -3 S / cm or more (e.g. 1.5×10 -3 ~3.0×10 -3 S / cm, 1.7×10 -3 ~3.0×10 -3 S / cm) of lithium ion conductivity (25℃).

[0068] The composition of the Sn-containing sulfide solid electrolyte according to the embodiment of the present invention can be exemplified by, but not limited to, Li 3.27 Sn 0.27 P 0.73 S4, Li 3.33 Sn 0.33 P 0.67 S4, Li4SnS4, Li2SnS3, Li 10 SnP2S 12 、Li 10 (Ge 0.5 Sn 0.5 )P2S 12 、Li 10 (Si 0.5 Sn 0.5 )P2S 12 、Li 3.45 [Sn 0.09 Si 0.36 ] P 0.05 S4, Na4SnS4, Na4SnS4, Na2SnS3, Na 10 SnP2S 12 、Na 9.81 Sn 0.81 P 2.19 S 12 、Na 10 (Ge 0.5 Sn 0.5 )P2S 12 、Na 10 (Si 0.5 Sn 0.5 )P2S 12 、Na 3.45 [Sn 0.09 Si0.36 ]P 0.05 S4, preferably Li 3.27 Sn 0.27 P 0.73 S4, Li 3.33 Sn 0.33 P 0.67 S4, particularly preferably Li 3.27 Sn 0.27 P 0.73 S4.

[0069] 3. All-solid-state battery The Sn-containing sulfide solid electrolyte described above can be used for, for example, a lithium ion secondary battery, and particularly can be used for an all-solid-state lithium ion secondary battery. Therefore, according to still another embodiment of the present application, an all-solid-state battery containing the Sn-containing sulfide solid electrolyte described above can be provided.

[0070] The "all-solid-state battery" of the present embodiment refers to an all-solid-state lithium ion secondary battery. Figure 2 A schematic cross-sectional view of an all-solid-state battery according to an embodiment of the present application. 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 for various devices typified by mobile phones, personal computers, and automobiles.

[0071] The Sn-containing sulfide solid electrolyte according to the embodiment of the present application can 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 Sn-containing sulfide solid electrolyte according to the embodiment of the present application, the Sn-containing sulfide solid electrolyte is used in combination with a known positive electrode active material or negative electrode active material for a lithium ion secondary battery. The use ratio of the Sn-containing sulfide solid electrolyte contained in the positive electrode layer 1 or the negative electrode layer 3 to other materials is not particularly limited.

[0072] When the solid electrolyte layer 2 contains the Sn-containing sulfide solid electrolyte according to the embodiment of the present application, the solid electrolyte layer 2 can be composed only of the Sn-containing sulfide solid electrolyte according to the embodiment of the present application, or can be used in combination with an oxide solid electrolyte (for example, Li7La3Zr2O12), a sulfide-based solid electrolyte (for example, Li2S-P2S5), and other complex hydride solid electrolytes (for example, LiBH4, 3LiBH4-LiI), as needed. 12

[0073] The all-solid-state battery is manufactured by molding and stacking the layers described above, but the molding method and the stacking method of each layer are not particularly limited.

[0074] ​For example, there are a method in which a slurry prepared by dispersing a solid electrolyte and / or an electrode active material in a solvent is coated by a doctor blade or spin coating, etc., and then calendered to form a film; a vapor phase method in which film formation and lamination are performed by a vacuum evaporation method, an ion plating method, a sputtering method, a laser ablation method, etc.; a press molding method in which a powder is molded by hot press or cold press without heating, and the molded body is laminated; and the like.

[0075] Since the Sn-containing sulfide solid electrolyte of the embodiment of the present application is relatively soft, it is particularly preferable to produce a full solid-state battery by molding and laminating each layer by a press molding method. As the press molding method, there are a hot press method with heating and a cold press method without heating, and the cold press method can also be sufficient for molding.

[0076] Example The embodiment of the present application will be described in more detail below by way of examples, but the gist of the present application is not limited only to this.

[0077] <Li 3.27 Sn 0.27 P 0.73 Synthesis of S4 (Example 1) Li2S (manufactured by Sigma Aldrich, purity 99.8%), P2S5 (manufactured by Sigma Aldrich, purity 99%), and SnS2 (manufactured by Takasago Pure Chemical Industries, Ltd., purity 99.9%) were used as raw materials. In a glove box under an argon atmosphere, 0.5 g of the raw materials were weighed out in a stoichiometric ratio, and mixed in a maroon mortar for 15 minutes. 1.0 g of the obtained powder and 15 Φ10 mm zirconia balls ("YTZ" manufactured by Nikkato Co., Ltd.) were put into a 45 mL zirconia crucible, and sealed. The zirconia crucible was fixed to a planetary ball mill device (P7 manufactured by FRITSCH Japan), and subjected to mechanical grinding treatment at a rotation speed of 600 rpm for 10 hours (gravity value: 27.5 G). After the mechanical grinding treatment, the zirconia balls were separated from the powder with a mesh size of 2 mm stainless steel sieve to obtain a solid electrolyte powder. This series of operations were performed in a glove box under an argon atmosphere. 3.27 Sn 0.27 P 0.73 The above raw materials were weighed out in a stoichiometric ratio of S4, and mixed in a maroon mortar for 15 minutes. 1.0 g of the obtained powder and 15 Φ10 mm zirconia balls ("YTZ" manufactured by Nikkato Co., Ltd.) were put into a 45 mL zirconia crucible, and sealed. The zirconia crucible was fixed to a planetary ball mill device (P7 manufactured by FRITSCH Japan), and subjected to mechanical grinding treatment at a rotation speed of 600 rpm for 10 hours (gravity value: 27.5 G). After the mechanical grinding treatment, the zirconia balls were separated from the powder with a mesh size of 2 mm stainless steel sieve to obtain a solid electrolyte powder. This series of operations were performed in a glove box under an argon atmosphere.

[0078] Note that the gravity value was calculated according to the following formula.

[0079] Gravity value (G) = 1118 x revolution radius (m) x rotation speed (rpm) 2 x 10 -6 wherein the revolution radius refers to the distance from the end of the base of the planetary ball mill to the center of the fixed position of the zirconia crucible. A device having a revolution radius of 0.0682 m was used in the example.

[0080] (Example 2) The same procedure as in Example 1 was carried out except that the mechanical grinding treatment was performed at a rotation speed of 800 rpm for 10 hours, to produce a solid electrolyte powder (gravitational value: 48.8 G) (Example 3) Li2S (manufactured by Sigma-Aldrich Corporation, purity 99.8%), P2S5 (manufactured by Sigma-Aldrich Corporation, purity 99%) and SnS2 (manufactured by Takasago Pure Chemical Industries, Ltd., purity 99.9%) were used as raw materials. In a glove box under an argon atmosphere, 0.5 g of the above raw materials were weighed out in a stoichiometric ratio of Li 3.27 Sn 0.27 P 0.73 The raw materials were mixed in a marvered mortar for 15 minutes. 1.0 g of the obtained powder, 15 zirconia balls (manufactured by Nikkato Co., Ltd., "YTZ") of Φ 10 mm and 8 mL of heptane (manufactured by Wako Pure Chemical Industries, Ltd., super-dehydrated grade) were put into a 45 mL zirconia crucible, which was sealed. The zirconia crucible was fixed to a planetary ball mill device (P-7 manufactured by FRITSCH Japan), and a mechanical grinding treatment was performed at a rotation speed of 600 rpm for 10 hours (gravitational value: 27.5 G). After the mechanical grinding treatment, the zirconia balls were separated from the slurry with a stainless steel sieve having a mesh size of 2 mm. The obtained slurry was subjected to removal of the solvent under a reduced pressure at a temperature of 60°C. Then, vacuum drying was performed at a temperature of 150°C for 1 hour, to thereby obtain a solid electrolyte powder. The entire series of operations were performed in a glove box under an argon atmosphere.

[0081] (Reference Example 1) Li2S (manufactured by Sigma-Aldrich Corporation, purity 99.8%), P2S5 (manufactured by Sigma-Aldrich Corporation, purity 99%) and SnS2 (manufactured by Takasago Pure Chemical Industries, Ltd., purity 99.9%) were used as raw materials. In a glove box under an argon atmosphere, 0.5 g of the above raw materials were weighed out in a stoichiometric ratio of Li 3.27 Sn 0.27 P 0.73The raw materials were weighed in stoichiometric ratios for S4, and mixed in a agate mortar for 15 minutes. 1.0 g of the resulting powder and 15 zirconia balls (Φ10 mm, "YTZ" manufactured by Nikkato Co., Ltd.) were put into a zirconia crucible of 45 mL, and sealed. The zirconia crucible was fixed to a planetary ball mill device (P-7 manufactured by FRITSCH Japan Co., Ltd.), and subjected to a mechanical grinding treatment at a rotation speed of 800 rpm for 10 hours. After the mechanical grinding treatment, the zirconia balls were separated from the powder with a stainless steel sieve of 2 mm mesh. The resulting powder was subjected to a firing treatment at a temperature of 472°C for 8 hours under an argon atmosphere, to obtain a solid electrolyte powder. The series of operations were performed in a glove box under an argon atmosphere.

[0082] <Measurement of lithium ion conductivity> The solid electrolyte powders obtained in Examples 1 to 3 were used for uniaxial molding (480 MPa) to obtain a disc having a thickness of about 1 mm and a diameter of 10 mm. An alternating current impedance measurement was performed at room temperature (25°C) by a four-terminal method using a full solid-state battery evaluation unit (manufactured by Hohsen Corporation) to calculate the lithium ion conductivity ("SI1260 IMPEDANCE / GAIN-PHASE ANALYZER" manufactured by Solartron).

[0083] Specifically, the lithium ion conductivity was measured after the sample was left in a thermostat set to 25°C for 30 minutes. The measurement frequency range was set to 0.1 Hz to 1 MHz, and the amplitude was set to 50 mV. The results are shown in Table 1.

[0084] [Table 1] <X-ray diffraction measurement> An X-ray diffraction measurement was performed on the solid electrolyte powders obtained in Examples 1 to 3 and Reference Example 1 at room temperature (25°C) under an argon atmosphere ("X' Pert3 Powder" manufactured by PANalytical, CuKα: λ = 1.5405 Å). The results of the X-ray diffraction measurement are shown in Figure 3 .

[0085] Furthermore, based on the results of the X-ray diffraction measurement shown in Figure 3 , the half-value width of the peak at 2θ = 19.83° ± 0.50° and the half-value width of the peak at 2θ = 29.07° ± 0.50° were calculated. The calculation method is shown below.

[0086] The diffraction data obtained by the above X-ray diffraction measurement were introduced into the crystal structure analysis software SmartLab studio II, and background fitting and peak fitting were performed. The profile fitting selected a segmented pseudo-Voigt function, and the half-peak width of each peak was automatically calculated.

[0087] As a result, unlike the peaks of Reference Example 1 which had undergone a heating process after the mechanical grinding treatment, the X-ray diffraction peaks of Examples 1 to 3 had a wider peak width.

[0088] <raman spectrum measurement> (1) Sample preparation A sample for Raman spectrum measurement was prepared using the solid electrolyte powders obtained in Examples 1 to 3 and Reference Example 1 and a closed container having a quartz glass (Φ60 mm, thickness 1 mm) as an optical window on the top. After the solid electrolyte powder was attached to the quartz glass in an argon atmosphere glove box, the container was sealed and taken out of the glove box, and Raman spectrum measurement was performed.

[0089] (2) Measurement conditions Measurement was performed using a laser Raman spectrophotometer NRS-5100 (manufactured by Japan Spectroscopic Co., Ltd.) under conditions of an excitation wavelength of 532.15 nm and an exposure time of 10 seconds to 15 seconds (Example 1: 10 seconds; Example 2: 12 seconds; Example 3: 15 seconds; Reference Example 1: 15 seconds).

[0090] The results of the Raman spectrum measurement are shown in Figure 4 .

[0091] As a result, according to the method of the examples, a Sn-containing sulfide solid electrolyte having excellent ionic conductivity can be obtained without a heating process after the mechanical grinding treatment.

[0092] The above describes several embodiments of the present application, but these embodiments are merely illustrative and are not intended to limit the scope of the present application. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made within the scope of the gist of the present application. These embodiments and their modifications are not only included in the scope and gist of the present application, but also included in the scope equivalent to the application recited in the scope of claim.

[0093] Explanation of symbols 1: positive electrode layer 2: solid electrolyte layer 3: negative electrode layer 10: all-solid-state battery

Claims

1. A method for producing a Sn-containing sulfide solid electrolyte, characterized in that: include: A step of preparing a raw material mixture containing Li, Sn, P, and S elements; and The raw material mixture is subjected to mechanical grinding to obtain a Sn-containing sulfide solid electrolyte. No heating treatment was performed after the mechanical grinding treatment.

2. The method according to claim 1, wherein: The Sn-containing sulfide solid electrolyte has a -4 S / cm or higher lithium ion conductivity.

3. The method according to claim 1 or 2, characterized in that: The Sn-containing sulfide solid electrolyte has a crystalline phase with an orthorhombic structure.

4. The method according to any one of claims 1 to 3, characterized in that: The Sn-containing sulfide solid electrolyte has diffraction peaks at least at 2θ=14.08°±0.50°, 17.10°±0.50°, 17.89°±0.50°, 19.83°±0.50°, 25.66°±0.50°, 26.58°±0.50° and 29.07°±0.50° in X-ray diffraction (CuKα:λ=1.5405Å).

5. The method according to any one of claims 1 to 4, characterized in that: The Sn-containing sulfide solid electrolyte has a Raman spectrum of at least 415±10 cm -1 and 340±10cm -1 There is a peak.

6. The manufacturing method according to any one of claims 1 to 5, characterized in that: The Sn-containing sulfide solid electrolyte contains the following crystal structure as a main body, The crystal structure has an octahedron O composed of Li elements and S elements, a tetrahedron T1 composed of one or more elements selected from P and Sn and S elements, and a tetrahedron T2 composed of P elements and S elements. The tetrahedron T1 shares edges with the octahedron O, and the tetrahedron T2 shares vertices with the above-mentioned octahedron O.

7. The method according to any one of claims 1 to 6, characterized in that: The mechanical grinding is dry mechanical grinding.

8. The method according to any one of claims 1 to 7, characterized in that: The mechanical grinding is wet mechanical grinding.

9. The method according to claim 8, characterized in that: The wet mechanical grinding is performed in the presence of a hydrocarbon solvent.

10. The method according to claim 9, characterized in that: The hydrocarbon solvent is selected from heptane, hexane, toluene and xylene.

11. The method according to any one of claims 1 to 10, characterized in that: The mechanical grinding process is carried out using a planetary ball mill under conditions where the gravity value is above 27.5G, and the gravity value is calculated according to the following formula: Gravity (G) = 1118 × orbital radius (m) × rotation speed (rpm) 2 ×10 -6 .

12. A Sn-containing sulfide solid electrolyte, characterized in that: A crystalline phase containing Li, Sn, P and S elements and having an orthorhombic structure has peaks at at least 2θ=14.08°±0.50°, 17.10°±0.50°, 17.89°±0.50°, 19.83°±0.50°, 25.66°±0.50°, 26.58°±0.50° and 29.07°±0.50° in X-ray diffraction (CuKα:λ=1.5405Å).

13. The Sn-containing sulfide solid electrolyte according to claim 12, characterized in that: In X-ray diffraction (CuKα:λ=1.5405Å) of the Sn-containing sulfide solid electrolyte, the half-peak width of the peak at 2θ=19.83°±0.50° is 0.80-1.70°, and the half-peak width of the peak at 2θ=29.07°±0.50° is 0.70-1.40°.

14. The Sn-containing sulfide solid electrolyte according to claim 12 or 13, characterized in that: The Sn-containing sulfide solid electrolyte has a ﹣4 S / cm or higher lithium ion conductivity.

15. The Sn-containing sulfide solid electrolyte according to any one of claims 12 to 14, characterized in that: The Sn-containing sulfide solid electrolyte has a Raman spectrum of at least 415±10 cm ﹣1 and 340±10cm ﹣1 There is a peak.

16. The Sn-containing sulfide solid electrolyte according to any one of claims 12 to 15, characterized in that: The Sn-containing sulfide solid electrolyte contains the following crystal structure as a main body, wherein the 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 and Sn and S element, and a tetrahedron T2 composed of P element and S element, and the tetrahedron T1 shares edges with the octahedron O, and the tetrahedron T2 shares vertices with the above-mentioned octahedron O.

17. An all-solid-state battery, characterized in that: A Sn-containing sulfide solid electrolyte according to any one of claims 12 to 16.

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