Method for producing sulfide-based inorganic solid electrolyte material

Abstract

To provide a method for producing a diphosphorus pentasulfide composition that achieves both high crystallinity degree and high recovery rate.SOLUTION: Provided is a method for producing diphosphorus pentasulfide composition that comprises a heating step of treating a raw material diphosphorus pentasulfide composition at a temperature of 130°C or higher and lower than the melting point of the raw material diphosphorus pentasulfide composition, and that yields a high-crystallinity degree diphosphorus pentasulfide composition having higher crystallinity degree than the raw material diphosphorus pentasulfide composition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing a diphosphorus pentasulfide composition, and more specifically to a method for producing a diphosphorus pentasulfide composition that is preferably used for a sulfide-based inorganic solid electrolyte. [Background technology]

[0002] Lithium-ion batteries are commonly used as power sources for small portable devices such as mobile phones and laptops, and recently have begun to be used as power sources for electric vehicles and power storage devices in addition to small portable devices.

[0003] Currently available lithium-ion batteries use electrolytes containing flammable organic solvents. On the other hand, lithium-ion batteries that use a solid electrolyte to create an all-solid-state battery (hereinafter referred to as all-solid-state lithium-ion batteries) do not use flammable organic solvents within the battery, which allows for simplified safety devices and is thought to be superior in terms of manufacturing cost and productivity.

[0004] Known examples of solid electrolyte materials used in such solid electrolytes include sulfide-based inorganic solid electrolyte materials, and a method for producing the sulfide-based inorganic solid electrolyte material is known in which a diphosphorus pentasulfide composition containing diphosphorus pentasulfide (P2S5) as a main component is treated with a material such as lithium sulfide.

[0005] Patent Document 1 (JP 2020-61304 A) describes a phosphorus pentasulfide composition having a crystallinity of 30% or more as calculated from a spectrum obtained by X-ray diffraction measurement using CuKα radiation. It also describes that a phosphorus pentasulfide composition having a crystallinity of 30% or more can be obtained by vacuum heating or the like to reduce the amount of low-boiling phosphorus sulfide compounds (such as P4S3 and P4S7) in the phosphorus pentasulfide composition and improve crystallinity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-61304 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the production method of the above invention is adopted, the heating temperature is high, so that the recovery rate of the diphosphorus pentasulfide composition after production relative to the raw material diphosphorus pentasulfide composition is low, resulting in a problem of high production costs.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a diphosphorus pentasulfide composition that can produce a diphosphorus pentasulfide composition having a high degree of crystallinity and that has a high recovery rate relative to the starting diphosphorus pentasulfide composition. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to provide a method for producing a diphosphorus pentasulfide composition that achieves both a high degree of crystallinity and a high recovery rate. As a result, they have discovered that, in a heating step for crystallizing the diphosphorus pentasulfide composition, annealing the starting diphosphorus pentasulfide composition at a low temperature equal to or lower than its melting point makes it possible to achieve both a high degree of crystallinity and a high recovery rate for the resulting diphosphorus pentasulfide composition, thereby completing the present invention.

[0010] That is, according to the present invention, a heating step of treating a raw material diphosphorus pentasulfide composition at a temperature of 130°C or higher and lower than the melting point of the raw material diphosphorus pentasulfide composition; A method for producing a phosphorus pentasulfide composition is provided, which produces a high-crystallinity phosphorus pentasulfide composition having a higher crystallinity than the starting phosphorus pentasulfide composition. [Effects of the Invention]

[0011] According to the present invention, a method for producing a diphosphorus pentasulfide composition that achieves both a high degree of crystallinity and a high recovery rate can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by common reference numerals, and the description will be omitted as appropriate. Also, the drawings are schematic views and do not match the actual dimensional ratios. The numerical range "A to B" represents A or more and B or less unless otherwise specified.

[0014] [Method for Producing Phosphorus Pentasulfide Composition] First, the method for producing a phosphorus pentasulfide composition according to the present embodiment will be described. The manufacturing method of the phosphorus pentasulfide composition according to this embodiment is different from the conventional manufacturing method of the phosphorus pentasulfide composition. That is, the highly crystallized phosphorus pentasulfide composition according to this embodiment can be obtained for the first time by adopting a manufacturing method device such as a process of reducing the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) in the raw material phosphorus pentasulfide composition by performing a heat treatment on the raw material phosphorus pentasulfide composition. However, the manufacturing method of the phosphorus pentasulfide composition according to this embodiment can adopt various specific manufacturing conditions on the premise of adopting the above-mentioned manufacturing method device.

[0015] The manufacturing method of the phosphorus pentasulfide composition according to this embodiment includes a heating step of heat-treating the raw material phosphorus pentasulfide composition at a temperature of 130°C or higher and lower than the melting point of the raw material phosphorus pentasulfide composition, and obtaining a highly crystallized phosphorus pentasulfide composition having a higher crystallinity than the raw material phosphorus pentasulfide composition. By adopting the above configuration, the manufacturing method of the phosphorus pentasulfide composition according to this embodiment performs heating at a temperature lower than the melting point of the raw material phosphorus pentasulfide composition, so that the evaporation of phosphorus pentasulfide contained in the phosphorus pentasulfide composition can be minimized, and only low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) can be effectively removed.

[0016] Hereinafter, the manufacturing method of the phosphorus pentasulfide composition according to this embodiment will be described more specifically.

[0017] (Heating Step) In the manufacturing method of the phosphorus pentasulfide composition according to this embodiment, by heat-treating the raw material phosphorus pentasulfide composition, the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) in the raw material phosphorus pentasulfide composition is reduced, and the crystallinity of the raw material phosphorus pentasulfide composition is improved. Thereby, a highly crystallized phosphorus pentasulfide composition having a higher crystallinity than the raw material phosphorus pentasulfide composition according to this embodiment can be obtained. Here, when the raw material phosphorus pentasulfide composition is heated, the components that accumulate at the bottom of the container without evaporating are usually the highly crystallized phosphorus pentasulfide composition according to this embodiment.

[0018] Here, as the lower limit value of the heating temperature in the above heating step, it is preferable to perform heat treatment at 130°C or higher, more preferably 150°C or higher, and even more preferably 180°C or higher. By setting the heating temperature to be equal to or higher than the above lower limit value, the crystallinity of the high-crystallinity phosphorus pentasulfide composition can be made more suitable. Further, as the upper limit value of the heating temperature in the above heating step, it is preferable to perform heat treatment at a temperature lower than the melting point of the above raw material phosphorus pentasulfide composition, more preferably 250°C or lower, and even more preferably 220°C or lower. By setting the heating temperature to be equal to or lower than the above upper limit value, the recovery rate of the high-crystallinity phosphorus pentasulfide composition can be made more suitable. Note that the melting point of the above raw material phosphorus pentasulfide composition can be confirmed by a DSC curve described later.

[0019] The method for producing a phosphorus pentasulfide composition according to the present embodiment can obtain a phosphorus pentasulfide composition that achieves both high crystallinity and high recovery rate by heat-treating the raw material phosphorus pentasulfide composition in a temperature range of equal to or higher than the above lower limit value and equal to or lower than the above upper limit value. The reason for this is not necessarily clear, but in the method for producing a phosphorus pentasulfide composition according to the present embodiment, the raw material phosphorus pentasulfide composition is heated to a temperature lower than its melting point to temporarily destabilize its structure, making it easier for glassy phosphorus pentasulfide to change to a more stable crystalline state, and only low-boiling phosphorus sulfide compounds (such as P4S3, P4S7, etc.) are removed, which is considered to be able to minimize the evaporation of phosphorus pentasulfide. Currently, it is believed that the degree of crystallinity of a phosphorus pentasulfide composition calculated from an X-ray diffraction spectrum is closely related to the lithium ion conductivity of a sulfide-based inorganic solid electrolyte material obtained from the phosphorus pentasulfide. Furthermore, it is believed that the higher the degree of crystallinity of the phosphorus pentasulfide composition calculated from the X-ray diffraction spectrum, the higher the crystallinity of the phosphorus pentasulfide and the lower the amount of low-boiling-point phosphorus sulfide compounds (e.g., P4S3, P4S7). Therefore, vacuum heating treatments have been used to remove low-boiling-point phosphorus sulfide compounds (e.g., P4S3, P4S7). However, because heating was performed at temperatures above the melting point of the phosphorus pentasulfide composition (e.g., 300°C), some of the phosphorus pentasulfide contained in the phosphorus pentasulfide composition was evaporated, presumably resulting in a low recovery rate. On the other hand, in the method for producing a diphosphorus pentasulfide composition according to this embodiment, the starting material diphosphorus pentasulfide composition is heated to a temperature below the melting point, which minimizes evaporation of diphosphorus pentasulfide contained in the diphosphorus pentasulfide composition and makes it possible to effectively remove only low-boiling point phosphorus sulfide compounds (PS3, PS7, etc.). For the reasons described above, the method for producing a diphosphorus pentasulfide composition according to this embodiment effectively removes low-boiling point phosphorus sulfide compounds, and therefore, it is believed that the use of the method for producing a diphosphorus pentasulfide composition according to this embodiment can achieve both a high degree of crystallinity and a high recovery rate.

[0020] In the method for producing a phosphorus pentasulfide composition according to this embodiment, the upper limit of the recovery rate of the high-crystallinity phosphorus pentasulfide composition is preferably 90% or more, more preferably 91% or more, and even more preferably 92% or more. By ensuring that the recovery rate is equal to or greater than the lower limit, the production efficiency of the high-crystallinity phosphorus pentasulfide composition can be improved. The lower limit of the recovery rate is not particularly limited, but is preferably 99% or less, more preferably 98% or less, and even more preferably 97% or less. By keeping the recovery rate at or below the upper limit, the amount of low-boiling phosphorus sulfide compounds (such as P4S3 and P4S7) in the starting diphosphorus pentasulfide composition can be reduced. Note that the recovery rate refers to the ratio of the mass of the highly crystallized phosphorus pentasulfide composition after heating to the mass of the raw material phosphorus pentasulfide composition, and can be calculated from the following formula (1). Recovery rate (%) = (M A / M B ) × 100 (1) M A : Mass of the highly crystallized phosphorus pentasulfide composition (g) M B : Mass of the raw material phosphorus pentasulfide composition (g)

[0021] In the method for producing a phosphorus pentasulfide composition according to this embodiment, the lower limit of the heating time of the raw material phosphorus pentasulfide composition in the heating step is preferably 0.5 hours or more, more preferably 3 hours or more, still more preferably 5 hours or more, and particularly preferably 6 hours or more. When the heating time is at least the above lower limit, the crystallinity of the highly crystallized phosphorus pentasulfide composition can be made more suitable. Also, the upper limit of the heating time is preferably 24 hours or less, more preferably 12 hours or less, still more preferably 10 hours or less, and particularly preferably 8 hours or less. When the heating time is at most the above upper limit, the recovery rate of the highly crystallized phosphorus pentasulfide composition can be made more suitable.

[0022] Note that in the method for producing a phosphorus pentasulfide composition according to this embodiment, the heating temperature and the heating time can be appropriately determined according to the throughput of the raw material phosphorus pentasulfide composition, the required recovery rate for the highly crystallized phosphorus pentasulfide composition to be produced, physical properties, etc. Among them, from the viewpoint of the balance between the recovery rate and the crystallinity of the highly crystallized phosphorus pentasulfide composition, it is preferable that the heating temperature is 180°C or higher and 220°C or lower and the heating time is 6 hours or more and 8 hours or less.

[0023] In the method for producing a phosphorus pentasulfide composition according to this embodiment, it is preferable to perform the heating step under an inert gas atmosphere or a vacuum atmosphere, and more preferably under an inert gas atmosphere. By adopting the above configuration, it is possible to prevent reaction with each component or moisture in the air and to prevent the generation of impurities in the phosphorus pentasulfide composition. In particular, performing the heating step under an inert gas atmosphere is preferable from the viewpoint of easy maintenance of the atmosphere in the heating device. Note that the vacuum atmosphere means that the pressure in the heating device is -0.01 MPa or less.

[0024] Examples of the inert gas in the heating step include argon gas, helium gas, nitrogen gas, etc. Among these, argon gas is particularly preferable. These inert gases are preferably of higher purity in order to prevent contamination of impurities into the product, and preferably have a dew point of -70°C or lower, and particularly preferably -80°C or lower, in order to avoid contact with moisture. The method for introducing the inert gas into the mixing system is not particularly limited as long as the inside of the mixing system is filled with an inert gas atmosphere, and examples include a method of purging with an inert gas and a method of continuously introducing a certain amount of inert gas.

[0025] (Preparation Step) In the method for producing a phosphorus pentasulfide composition according to this embodiment, a preparation step of preparing a raw material phosphorus pentasulfide composition may be included before the heating step. The raw material phosphorus pentasulfide composition used as the raw material is not particularly limited, and commercially available phosphorus pentasulfide (P2S5) may be used as it is, or a raw material phosphorus pentasulfide composition obtained by using a generally known method for producing phosphorus pentasulfide may be used.

[0026] [Phosphorus Pentasulfide Composition] Next, a highly crystallized phosphorus pentasulfide composition (hereinafter also referred to as a phosphorus pentasulfide composition) obtained by the method for producing a phosphorus pentasulfide composition according to this embodiment will be described.

[0027] For the diphosphorus pentasulfide composition according to this embodiment, the lower limit value of the crystallinity calculated from the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source is preferably 40% or more, more preferably 45% or more, still more preferably 50% or more, and particularly preferably 55% or more. Furthermore, the upper limit value of the crystallinity is preferably 80% or less, more preferably 76% or less, still more preferably 73% or less, and particularly preferably 70% or less.

[0028] Since the crystallinity of the diphosphorus pentasulfide composition according to this embodiment is equal to or higher than the lower limit value, the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material produced using the obtained diphosphorus pentasulfide composition can be improved. In addition, since the crystallinity of the diphosphorus pentasulfide composition according to this embodiment is equal to or lower than the upper limit value, while preferably maintaining the lithium ion conductivity, the recovery rate of the diphosphorus pentasulfide composition can be made more suitable.

[0029] Here, the method for calculating the crystallinity of the diphosphorus pentasulfide composition will be described with reference to FIG. 3. FIG. 3 is a diagram showing an X-ray diffraction spectrum for explaining the method for calculating the crystallinity (peak separation method) of the diphosphorus pentasulfide composition according to this embodiment. First, in X-ray diffraction using CuKα rays as the radiation source, the diffraction curve corresponding to the crystalline material becomes a sharp peak, and the diffraction curve corresponding to the amorphous material becomes a broad halo due to scattering. Therefore, the ratio of the crystalline material to the total of the crystalline and amorphous materials can be calculated as the crystallinity. In this embodiment, the peak separation method is used as the method for calculating the crystallinity. Without considering the effects of incoherent scattering and lattice disorder, etc., the X-ray diffraction pattern (also called the scattering curve) is separated into a crystalline diffraction curve and an amorphous halo using a profile fitting technique. The analysis software attached to the X-ray diffractometer can be used for profile fitting. The specific procedure for calculating the crystallinity is as follows (see Figure 3; Rigaku Corporation, X-ray Diffraction Handbook, February 21, 2000, 3rd edition, p. 83, Figure 3.6.2). (1) Background separation A straight line is drawn connecting the X-ray intensities from the low angle side to the high angle side, and the area under the line is taken as the background. (2) Halo separation The amorphous halo pattern is estimated and the halo is isolated from the background-subtracted scattering curve. (3) Separation of crystalline diffraction curves The crystalline diffraction curve is separated in the same manner as in (2) above. (4) Calculation of crystallinity The degree of crystallinity is calculated from the following formula (2) using the area under the curve (integrated intensity) of the diffraction curve of the amorphous component (amorphous halo) and the diffraction curve of the crystalline component (crystalline diffraction curve) separated from the scattering curve. Xc={Ic / (Ic+Ia)}×100 (2) Ic: Area under the diffraction curve of the crystalline component (crystalline diffraction curve) (integrated intensity) Ia: Area under the diffraction curve of the amorphous component (amorphous halo) (integrated intensity) When the phosphorus pentasulfide composition contains a solvent, it is preferable to dry and remove the solvent from the phosphorus pentasulfide composition before measurement.

[0030] That is, by adjusting the crystallinity of the diphosphorus pentasulfide composition according to this embodiment, calculated from the X-ray diffraction spectrum, to be equal to or greater than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, a balance can be achieved between the recovery rate of the diphosphorus pentasulfide composition and the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material produced using the diphosphorus pentasulfide composition.

[0031] In this embodiment, a phosphorus pentasulfide composition in which the crystallinity calculated from the X-ray diffraction spectrum is equal to or higher than the lower limit value and equal to or lower than the upper limit value can be obtained, for example, by subjecting the raw material phosphorus pentasulfide composition to a heat treatment or performing a treatment to reduce the amount of low-boiling phosphorus sulfide compounds (such as P4S3 and P4S7) in the phosphorus pentasulfide composition.

[0032] For the phosphorus pentasulfide composition according to this embodiment, in the DSC curve of the phosphorus pentasulfide composition obtained by measurement using a differential scanning calorimeter, an endothermic peak is observed in the temperature range of 280°C or higher and 300°C or lower, and the heat of fusion of the endothermic peak is 60 J / g or higher, preferably 65 J / g or higher, more preferably 70 J / g or higher. The upper limit of the heat of fusion of the endothermic peak is preferably 120 J / g or lower, more preferably 110 J / g or lower, and even more preferably 100 J / g or lower. Here, the endothermic peak observed in the temperature range of 280°C or higher and 300°C or lower is the melting point of phosphorus pentasulfide (P2S5).

[0033] Note that the DSC curve can be measured, for example, by the following method. First, in an argon atmosphere, 20 to 25 mg of the phosphorus pentasulfide composition is weighed into an aluminum pan, and then covered with an aluminum lid and sealed with a sample sealer. The reference aluminum container is left empty. Differential scanning calorimetry is performed using a differential scanning calorimeter under the conditions of an initial temperature of 25°C, a measurement temperature range of 30 to 350°C, a heating rate of 5°C / min, and an argon atmosphere of 100 ml per minute. The differential scanning calorimeter is not particularly limited, and for example, DSC6300 manufactured by Seiko Instruments Inc. can be used. When the phosphorus pentasulfide composition contains a solvent, it is preferably measured after drying and removing the solvent from the phosphorus pentasulfide composition. From the DSC curve thus obtained, the presence or absence of an endothermic peak can be observed in the temperature range of 280°C or higher and 300°C or lower. Here, the heat of fusion of the endothermic peak is calculated by obtaining the area enclosed by the endothermic curve including the endothermic peak and the baseline. Since the specific heat capacity of a substance is different before and after a thermal change, the baseline before and after the endothermic peak does not form a straight line. Therefore, in the present embodiment, the baseline at the endothermic peak is defined as the line connecting point R and point S shown in FIG. 4. Point R is the intersection of the line parallel to the Y-axis passing through the intersection point P of the baseline before the endothermic peak and the tangent line of the endothermic peak, and the endothermic curve. Point S is the intersection of the line parallel to the Y-axis passing through the intersection point Q of the baseline after the endothermic peak and the tangent line of the endothermic peak, and the endothermic curve. Further, in the phosphorus pentasulfide composition according to the present embodiment, the endothermic peak observed in the temperature range of 280°C or higher and 300°C or lower is usually one.

[0034] In the phosphorus pentasulfide composition according to the present embodiment, an endothermic peak is observed in the temperature range of 280°C or higher and 300°C or lower in the DSC curve. By having the heat of fusion of the endothermic peak be equal to or higher than the lower limit value, the lithium ion conductivity of the obtained sulfide-based inorganic solid electrolyte material can be improved. The reason for this is not necessarily clear, but in the phosphorus pentasulfide composition according to the present embodiment, since the heating temperature is low, i.e., below the melting point, the structure of the raw material phosphorus pentasulfide composition is temporarily destabilized, making it easier for glassy phosphorus pentasulfide to change to a more stable crystalline state. Moreover, it is considered that by removing only low-boiling phosphorus sulfide compounds (such as P4S3, P4S7, etc.), the content of low-boiling phosphorus sulfide compounds (such as P4S3, P4S7, etc.) can be reduced, and higher-purity phosphorus pentasulfide can be obtained. Therefore, it is considered that the heat of fusion of the endothermic peak measured by the above method represents an index of the amount of low-boiling phosphorus sulfide compounds (such as P4S3, P4S7, etc.) in the phosphorus pentasulfide composition. That is, the higher the heat of fusion of the endothermic peak, the higher the crystallinity of phosphorus pentasulfide and the lower the amount of low-boiling phosphorus sulfide compounds (such as P4S3, P4S7, etc.). For the above reasons, since the amount of low-boiling phosphorus sulfide compounds in the phosphorus pentasulfide composition according to this embodiment is small, it is considered that when the phosphorus pentasulfide composition according to this embodiment is used, the lithium ion conductivity of the obtained sulfide-based inorganic solid electrolyte material can be improved. In this embodiment, for example, in the phosphorus pentasulfide composition in which an endothermic peak is observed in the temperature range of 280°C or higher and 300°C or lower in the DSC curve as shown in FIG. 4, and the heat of fusion of the endothermic peak is equal to or higher than the lower limit value, for example, by performing a heat treatment on the raw material phosphorus pentasulfide composition, it is possible to obtain it by performing a treatment such as reducing the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) in the phosphorus pentasulfide composition.

[0035] From the point that the lithium ion conductivity of the obtained sulfide-based inorganic solid electrolyte material can be further improved, it is preferable that no exothermic peak is observed in the DSC curve in at least the temperature range of 120°C or higher and 140°C or lower, and it is more preferable that no exothermic peak is observed in the DSC curve in at least the temperature range of 30°C or higher and 280°C or lower for the phosphorus pentasulfide composition according to this embodiment. In this embodiment, that no exothermic peak is observed in the DSC curve means that no peak with a heat quantity of 0.3 J / g or more, preferably 0.1 J / g or more is observed. Also, in this embodiment, the heat quantity of the exothermic peak and the baseline at the exothermic peak can be defined in the same manner as the heat quantity of the endothermic peak and the baseline at the endothermic peak described above. In this embodiment, the phosphorus pentasulfide composition in which no exothermic peak is observed in the DSC curve in the above temperature range can be obtained, for example, by performing a heat treatment on the raw material phosphorus pentasulfide composition and performing a treatment such as reducing the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) in the phosphorus pentasulfide composition.

[0036] The phosphorus pentasulfide composition according to this embodiment contains phosphorus pentasulfide (P2S5) as a main component. In the phosphorus pentasulfide composition according to this embodiment, examples of the components contained in addition to phosphorus pentasulfide (P2S5) include P4S9, P4S7, P4S3, and the like. At this time, when the total content of P2S5, P4S9, P4S7, and P4S3 in the phosphorus sulfide composition is 100% by mass, the lower limit of the content of phosphorus pentasulfide contained in the phosphorus pentasulfide composition according to this embodiment is preferably 70% by mass or more, more preferably 75% by mass or more, and still more preferably 80% by mass or more. By the lower limit of the content of phosphorus pentasulfide being the above lower limit or more, the lithium ion conductivity of the obtained sulfide-based inorganic solid electrolyte material can be further improved. The upper limit of the content of phosphorus pentasulfide contained in the phosphorus pentasulfide composition according to this embodiment is not particularly limited, but is, for example, 100% by mass or less. The content of phosphorus pentasulfide contained in the phosphorus pentasulfide composition can be calculated, for example, by a solid 31 P-NMR spectrum.

[0037] Solid 31 The P-NMR spectrum can be measured, for example, by the following method. First, a test sample is filled into a 3.2 mm diameter measurement sample tube in a glove box purged with N2 gas, and rotated (Magic Angle Spining: MAS) in a state inclined at a magic angle (54.7 degrees) with respect to the external magnetic field, and measurement is performed under the following conditions. Apparatus: JNM-ECA-600 manufactured by JEOL RESONANCE Co., Ltd. Observation frequency: 242.95 MHz Pulse width: 90° pulse Pulse waiting time: 2800 seconds Number of integrations: 64 times Measurement mode: Single pulse method MAS speed: 12 kHz Standard substance: (NH4)2HPO4·1.33 ppm Of the test sample 31Regarding the peaks detected in the ³¹P-NMR spectrum, refer to Reference 1 "Hellmut Eckert, Cheryl S. Liang and Galen D. Stucky : 31 ³¹P magic angle spinning NMR of crystalline phosphorous sulfides. Correlation of 31 ³¹P chemical shielding tensors with local environments, J. Phys. Chem, 1989, 93, 452―457", and perform waveform separation using a Gaussian function based on the following peak assignments to calculate the integral value of each peak. The integral value of the peak derived from each component is proportional to the molar number of phosphorus contained. Therefore, the content ratio can be calculated from the obtained integral value and the molecular weight of each component. The chemical shift of P₂S₅ is 40 - 52 ppm, the chemical shift of P₄S₉ is 52 - 70 ppm, the chemical shift of P₄S₇ is 80 - 90 ppm, 90 - 100 ppm, 110 - 115 ppm, and the chemical shift of P₄S₃ is 80 - 90 ppm, 90 - 100 ppm.

[0038] In the phosphorus pentasulfide composition according to this embodiment, when the solid 31 ³¹P-NMR spectrum is measured, it is preferable that no peak is observed in the range of 52 ppm or more and 70 ppm or less. That is, it is preferable that the peak of P₄S₉ is not observed. Thereby, the ratio of phosphorus pentasulfide in the phosphorus pentasulfide composition can be increased, and the lithium ion conductivity of the obtained sulfide-based inorganic solid electrolyte material can be further improved.

[0039] In the phosphorus pentasulfide composition according to this embodiment, the solid 31When measuring the P-NMR spectrum, it is preferable that no peaks are observed in the range of 80 ppm to 90 ppm. That is, it is preferable that no peaks of P4S7 and P4S3 are observed. This allows the proportion of diphosphorus pentasulfide in the diphosphorus pentasulfide composition to be increased, and the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material to be further improved.

[0040] The phosphorus pentasulfide composition according to this embodiment may be in the form of a powder, for example. Since the production of a sulfide-based inorganic solid electrolyte material, which will be described later, is generally carried out by a dry process, if the phosphorus pentasulfide composition according to this embodiment is in the form of a powder, the production of the sulfide-based inorganic solid electrolyte material becomes easier.

[0041] [Sulfide-based inorganic solid electrolyte material] The sulfide-based inorganic solid electrolyte material according to this embodiment will be described below. The sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained by using, as a raw material, a raw material composition for a sulfide-based inorganic solid electrolyte material containing the diphosphorus pentasulfide composition according to this embodiment and lithium sulfide. That is, the sulfide-based inorganic solid electrolyte material according to this embodiment preferably includes a mechanically treated product of a raw material composition for a sulfide-based inorganic solid electrolyte material containing the diphosphorus pentasulfide composition according to this embodiment and lithium sulfide.

[0042] The sulfide-based inorganic solid electrolyte material according to this embodiment preferably contains Li, P, and S as constituent elements from the viewpoint of further improving electrochemical stability, stability in moisture and air, ease of handling, and the like. Furthermore, from the viewpoint of further improving lithium ion conductivity, electrochemical stability, stability in moisture and air, ease of handling, and the like, the sulfide-based inorganic solid electrolyte material according to this embodiment has a molar ratio Li / P of the Li content to the P content in the sulfide-based inorganic solid electrolyte material of preferably 1.0 or more and 5.0 or less, more preferably 2.0 or more and 4.0 or less, even more preferably 2.5 or more and 3.8 or less, even more preferably 2.8 or more and 3.6 or less, even more preferably 3.0 or more and 3.5 or less, even more preferably 3.1 or more and 3.4 or less, and particularly preferably 3.1 or more and 3.3 or less. The molar ratio S / P of the S content to the P content is preferably 2.0 or more and 6.0 or less, more preferably 3.0 or more and 5.0 or less, even more preferably 3.5 or more and 4.5 or less, even more preferably 3.8 or more and 4.2 or less, even more preferably 3.9 or more and 4.1 or less, and particularly preferably 4.0. Here, the contents of Li, P, and S in the sulfide-based inorganic solid electrolyte material according to this embodiment can be determined by, for example, ICP emission spectroscopy or X-ray analysis.

[0043] In the sulfide-based inorganic solid electrolyte material according to this embodiment, the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material measured by an AC impedance method under the measurement conditions of 27.0°C, an applied voltage of 10 mV, and a measurement frequency range of 0.1 Hz to 7 MHz is preferably 1.0 × 10 -3 S cm -1 More preferably, 1.1 × 10 -3 S cm -1 More preferably, 1.3 × 10 -3 S cm -1 More preferably, 1.5 × 10 -3 S cm -1 That's all. When the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material according to the present embodiment is equal to or greater than the above lower limit, a lithium ion battery with even better battery characteristics can be obtained. Furthermore, by using such a sulfide-based inorganic solid electrolyte material, a lithium ion battery with even better input / output characteristics can be obtained.

[0044] The sulfide-based inorganic solid electrolyte material according to this embodiment may be in the form of particles, for example. The size of the particulate sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited, but the median diameter d 50 The lower limit of the median diameter d of the sulfide-based inorganic solid electrolyte material is preferably 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more. 50 By making the value of the thickness of the sheet equal to or greater than the lower limit, good handling properties can be maintained. In addition, the above median diameter d 50 The upper limit is preferably 150 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less. Median diameter d of sulfide-based inorganic solid electrolyte material 50 By making the value of the upper limit or less, the lithium ion conductivity can be further improved.

[0045] The sulfide-based inorganic solid electrolyte material according to this embodiment preferably has excellent electrochemical stability. Here, electrochemical stability refers to, for example, the property of being resistant to oxidation and reduction over a wide voltage range. More specifically, in the sulfide-based inorganic solid electrolyte material according to this embodiment, the maximum value of the oxidative decomposition current of the sulfide-based inorganic solid electrolyte material measured under conditions of a temperature of 25°C, a sweep voltage range of 0 to 5 V, and a voltage sweep rate of 5 mV / sec is preferably 0.50 μA or less, more preferably 0.20 μA or less, even more preferably 0.10 μA or less, even more preferably 0.05 μA or less, and particularly preferably 0.03 μA or less. It is preferable that the maximum value of the oxidative decomposition current of the sulfide-based inorganic solid electrolyte material is equal to or less than the above upper limit, since this makes it possible to suppress the oxidative decomposition of the sulfide-based inorganic solid electrolyte material in the lithium ion battery. The lower limit of the maximum value of the oxidative decomposition current of the sulfide-based inorganic solid electrolyte material is not particularly limited, but is, for example, 0.0001 μA or more.

[0046] The sulfide-based inorganic solid electrolyte material according to this embodiment can be used in any application requiring lithium ion conductivity. In particular, the sulfide-based inorganic solid electrolyte material according to this embodiment is preferably used in lithium ion batteries. More specifically, it is used in the positive electrode active material layer, negative electrode active material layer, electrolyte layer, etc. of lithium ion batteries. Furthermore, the sulfide-based inorganic solid electrolyte material according to this embodiment is preferably used in the positive electrode active material layer, negative electrode active material layer, solid electrolyte layer, etc. that constitute all-solid-state lithium ion batteries, and is particularly preferably used in the solid electrolyte layer that constitutes all-solid-state lithium ion batteries. An example of an all-solid-state lithium ion battery using the sulfide-based inorganic solid electrolyte material according to this embodiment is one in which a positive electrode, a solid electrolyte layer, and a negative electrode are stacked in this order.

[0047] [Method for producing sulfide-based inorganic solid electrolyte material] Next, a method for producing the sulfide-based inorganic solid electrolyte material according to this embodiment will be described. The method for producing the sulfide-based inorganic solid electrolyte material according to this embodiment preferably includes, for example, a step of mechanically treating a raw material composition for the sulfide-based inorganic solid electrolyte material containing the diphosphorus pentasulfide composition according to this embodiment and lithium sulfide. More specifically, the sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained, for example, by a production method including the following steps (A) and (B): Furthermore, the production method for the sulfide-based inorganic solid electrolyte material according to this embodiment may further include the following steps (C) and (D) as necessary. Step (A): A step of preparing a raw material composition for a sulfide-based inorganic solid electrolyte material containing the diphosphorus pentasulfide composition according to this embodiment and lithium sulfide. Step (B): A step of mechanically treating the raw material composition of the sulfide-based inorganic solid electrolyte material to chemically react and vitrify the raw materials, the diphosphorus pentasulfide composition and lithium sulfide, to obtain a glassy sulfide-based inorganic solid electrolyte material. Step (C) Heating the obtained glassy sulfide-based inorganic solid electrolyte material to crystallize at least a portion of it. Step (D): A step of pulverizing, classifying, or granulating the obtained sulfide-based inorganic solid electrolyte material.

[0048] (Step (A) of Preparing a Raw Material Composition of a Sulfide-Based Inorganic Solid Electrolyte Material) First, a raw material composition for a sulfide-based inorganic solid electrolyte material is prepared, which contains the diphosphorus pentasulfide composition according to the present embodiment as raw materials, lithium sulfide, and, if necessary, lithium nitride. The mixing ratio of each raw material in the raw material composition is adjusted so that the resulting sulfide-based inorganic solid electrolyte material has a desired composition ratio. The method for mixing the raw materials is not particularly limited as long as it can mix the raw materials uniformly. For example, mixing can be performed using a ball mill, bead mill, vibration mill, impact crusher, mixer (pug mixer, ribbon mixer, tumbler mixer, drum mixer, V-type mixer, etc.), kneader, twin-shaft kneader, air flow crusher, crusher, rotary blade crusher, etc. The mixing conditions, such as the stirring speed, processing time, temperature, reaction pressure, and gravitational acceleration applied to the mixture when mixing the raw materials, can be appropriately determined depending on the amount of the mixture to be processed.

[0049] The lithium sulfide used as a raw material is not particularly limited, and commercially available lithium sulfide may be used, or lithium sulfide obtained by, for example, reacting lithium hydroxide with hydrogen sulfide may be used. From the viewpoint of obtaining a high-purity sulfide-based inorganic solid electrolyte material and from the viewpoint of suppressing side reactions, it is preferable to use lithium sulfide with few impurities. In this embodiment, lithium sulfide also includes lithium polysulfide.

[0050] Lithium nitride may be used as the raw material. Here, the nitrogen in lithium nitride is discharged into the system as N2, so by using lithium nitride as the raw inorganic compound, it is possible to increase only the Li composition in a sulfide-based inorganic solid electrolyte material that contains Li, P, and S as constituent elements. The lithium nitride according to this embodiment is not particularly limited, and commercially available lithium nitride (for example, Li3N, etc.) may be used, or for example, lithium nitride obtained by the reaction of metallic lithium (for example, Li foil) and nitrogen gas may be used. From the viewpoints of obtaining a high-purity solid electrolyte material and suppressing side reactions, it is preferable to use lithium nitride with few impurities.

[0051] (Step (B) of obtaining a glassy sulfide-based inorganic solid electrolyte material) Subsequently, by mechanically treating the raw material composition of the sulfide-based inorganic solid electrolyte material, phosphorus pentasulfide composition and lithium sulfide as raw materials are vitrified while undergoing a chemical reaction to obtain a glassy sulfide-based inorganic solid electrolyte material.

[0052] Here, the mechanical treatment can be one that can be vitrified while undergoing a chemical reaction by mechanically colliding two or more inorganic compounds, and examples thereof include mechanochemical treatment. Here, the mechanochemical treatment is a method of vitrifying while applying mechanical energy such as shear force or collision force to the target composition. Also, in step (B), from the viewpoint of easily realizing an environment with a high level of removal of moisture and oxygen, the mechanochemical treatment is preferably a dry mechanochemical treatment. When using mechanochemical treatment, each raw material can be mixed while being pulverized into fine particles, so that the contact area of each raw material can be increased. Thereby, the reaction of each raw material can be promoted, and thus the sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained more efficiently.

[0053] Mechanochemical processing is a method of vitrifying a mixture by applying mechanical energy such as shear, impact, or centrifugal force. Examples of equipment for vitrification by mechanochemical processing (hereinafter referred to as vitrification equipment) include grinding and dispersing machines such as ball mills, bead mills, vibration mills, turbo mills, mechanofusion machines, disk mills, and roll mills; rotary and impact crushing machines that combine rotation (shear stress) and impact (compression stress), such as jackhammers, vibration drills, and impact drivers; high-pressure gliding rolls; and vertical mills such as roller-type vertical mills and ball-type vertical mills. Among these, ball mills and bead mills are preferred, with ball mills being particularly preferred, due to their ability to efficiently generate extremely high impact energy. Furthermore, from the viewpoint of excellent continuous productivity, preferred are roll mills; rotary / impact crushing devices consisting of a mechanism combining rotation (shear stress) and impact (compression stress), such as those typified by rock drills, vibration drills, and impact drivers; high-pressure gliding rolls; and vertical mills such as roller-type vertical mills and ball-type vertical mills.

[0054] The mixing conditions, such as the rotation speed, treatment time, temperature, reaction pressure, and gravitational acceleration applied to the raw inorganic composition when mechanically treating the raw material composition of a sulfide-based inorganic solid electrolyte material, can be appropriately determined depending on the type and treatment amount of the raw inorganic composition. Generally, the faster the rotation speed, the faster the glass production rate, and the longer the treatment time, the higher the conversion rate to glass. Generally, when X-ray diffraction analysis is performed using CuKα radiation as a radiation source, if the diffraction peaks derived from the raw materials disappear or decrease, it can be determined that the raw material composition of the sulfide-based inorganic solid electrolyte material has been vitrified and the desired sulfide-based inorganic solid electrolyte material has been obtained.

[0055] In the step (B), the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material is preferably 1.0 × 10 measured by an AC impedance method under the measurement conditions of 27.0°C, an applied voltage of 10 mV, and a measurement frequency range of 0.1 Hz to 7 MHz. -4 S cm -1 More preferably, 2.0 × 10-4 S cm -1 More preferably, 3.0 × 10 -4 S cm -1 More preferably, 4.0 × 10 -4 S cm -1 It is preferable to carry out the vitrification treatment until the temperature reaches or exceeds this level, thereby obtaining a sulfide-based inorganic solid electrolyte material with even better lithium ion conductivity.

[0056] (Step (C) of crystallizing at least a part of the sulfide-based inorganic solid electrolyte material) Next, the obtained sulfide-based inorganic solid electrolyte material in a glassy state is heated to crystallize at least a portion of the sulfide-based inorganic solid electrolyte material, thereby producing a sulfide-based inorganic solid electrolyte material in a glass-ceramic state (also called crystallized glass). In this way, a sulfide-based inorganic solid electrolyte material with even better lithium ion conductivity can be obtained. That is, the sulfide-based inorganic solid electrolyte material according to this embodiment is preferably in a glass ceramic state (crystallized glass state) because it has excellent lithium ion conductivity.

[0057] The temperature at which the sulfide-based inorganic solid electrolyte material in a glassy state is heated is preferably within the range of 220°C or higher and 500°C or lower, and more preferably within the range of 250°C or higher and 350°C or lower. The heating time for the sulfide-based inorganic solid electrolyte material in a glassy state is not particularly limited as long as it is a time that allows the sulfide-based inorganic solid electrolyte material in the desired glass-ceramic state to be obtained, but is, for example, in the range of 0.5 hours to 24 hours, preferably 1 hour to 3 hours. The heating method is not particularly limited, but examples thereof include a method using a firing furnace. Note that the conditions for such heating, such as temperature and time, can be appropriately adjusted to optimize the properties of the sulfide-based inorganic solid electrolyte material according to this embodiment.

[0058] In addition, heating of the glassy sulfide-based inorganic solid electrolyte material is preferably performed, for example, in an inert gas atmosphere. This can prevent deterioration (e.g., oxidation) of the sulfide-based inorganic solid electrolyte material. Examples of the inert gas when heating the glassy sulfide-based inorganic solid electrolyte material include argon gas, helium gas, nitrogen gas, etc. These inert gases are preferably of higher purity in order to prevent contamination of impurities into the product, and preferably have a dew point of -70°C or lower, particularly preferably -80°C or lower, in order to avoid contact with moisture. The method of introducing the inert gas into the mixed system is not particularly limited as long as the inside of the mixed system is filled with an inert gas atmosphere, and examples include a method of purging with an inert gas and a method of continuously introducing a certain amount of inert gas.

[0059] (Step (D) of pulverizing, classifying, or granulating) In the method for producing a sulfide-based inorganic solid electrolyte material according to the present embodiment, if necessary, a step of pulverizing, classifying, or granulating the obtained sulfide-based inorganic solid electrolyte material may be further performed. For example, by pulverizing to form fine particles and then adjusting the median diameter by a classification operation or a granulation operation, a sulfide-based inorganic solid electrolyte material having a desired median diameter can be obtained. The pulverization method is not particularly limited, and known pulverization methods such as a mixer, jet milling, a mortar, a rotary mill, and a coffee mill can be used. Also, the classification method is not particularly limited, and known methods such as sieves can be used. These pulverization or classification operations are preferably performed in an inert gas atmosphere or a vacuum atmosphere from the viewpoint of preventing contact with moisture in the air.

[0060] In order to obtain the sulfide-based inorganic solid electrolyte material according to the present embodiment, it is important to appropriately adjust each of the above steps. However, the method for producing a sulfide-based inorganic solid electrolyte material according to the present embodiment is not limited to the above method, and by appropriately adjusting various conditions, the sulfide-based inorganic solid electrolyte material according to the present embodiment can be obtained.

[0061] [Solid electrolyte] Next, the solid electrolyte according to this embodiment will be described. The solid electrolyte according to this embodiment includes the sulfide-based inorganic solid electrolyte material according to this embodiment. The solid electrolyte according to the present embodiment is not particularly limited, but may contain, as a component other than the sulfide-based inorganic solid electrolyte material according to the present embodiment, for example, a solid electrolyte material of a type different from the sulfide-based inorganic solid electrolyte material according to the present embodiment described above, within a range that does not impair the object of the present invention.

[0062] The solid electrolyte according to this embodiment may contain a solid electrolyte material of a different type from the sulfide-based inorganic solid electrolyte material according to this embodiment. The solid electrolyte material of a different type from the sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited as long as it has ion conductivity and insulating properties, but materials generally used in lithium ion batteries can be used. Examples of such materials include inorganic solid electrolyte materials such as sulfide-based inorganic solid electrolyte materials of a different type from the sulfide-based inorganic solid electrolyte material according to this embodiment, oxide-based inorganic solid electrolyte materials, and other lithium-based inorganic solid electrolyte materials; and organic solid electrolyte materials such as polymer electrolytes.

[0063] Examples of sulfide-based inorganic solid electrolyte materials different from the sulfide-based inorganic solid electrolyte material according to the present embodiment include Li2S-P2S5 material, Li2S-SiS2 material, Li2S-GeS2 material, Li2S-Al2S3 material, Li2S-SiS2-Li3PO4 material, Li2S-P2S5-GeS2 material, Li2S-Li2O-P2S5-SiS2 material, Li2S-GeS2-P2S5-SiS2 material, Li2S-SnS2-P2S5-SiS2 material, Li2S-P2S5-Li3N material, Li2S2+X-P4S3 material, Li2S-P2S5-P4S3 material, etc. These may be used alone or in combination of two or more. Among these, the Li2S-P2S5 material is preferred because it has excellent lithium ion conductivity and stability that does not cause decomposition or the like in a wide voltage range. Here, for example, the Li2S-P2S5 material means a solid electrolyte material obtained by chemically reacting at least Li2S (lithium sulfide) and P2S5 in an inorganic composition by mechanical treatment. Here, in the present embodiment, the lithium sulfide includes polysulfide lithium.

[0064] Examples of the oxide-based inorganic solid electrolyte material include NASICON types such as LiTi2(PO4)3, LiZr2(PO4)3, and LiGe2(PO4)3, perovskite types such as (La 0.5+x Li 0.5-3x )TiO3, Li2O-P2O5 materials, Li2O-P2O5-Li3N materials, and the like. Examples of other lithium-based inorganic solid electrolyte materials include LiPON, LiNbO3, LiTaO3, Li3PO4, LiPO 4-x N x (where x is 0 < x ≤ 1), LiN, LiI, LISICON, and the like. Furthermore, glass ceramics obtained by precipitating crystals of these inorganic solid electrolytes can also be used as the inorganic solid electrolyte material.

[0065] Examples of the organic solid electrolyte material include polymer electrolytes such as dry polymer electrolytes and gel electrolytes. As the polymer electrolyte, those generally used in lithium ion batteries can be used.

[0066] [Solid electrolyte membrane] Next, the solid electrolyte membrane according to the present embodiment will be described. The solid electrolyte membrane according to the present embodiment mainly includes a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to the present embodiment described above.

[0067] The solid electrolyte membrane according to this embodiment is used, for example, as a solid electrolyte layer constituting an all-solid-state lithium ion battery. An example of an all-solid-state lithium ion battery using the solid electrolyte membrane according to this embodiment is one in which a positive electrode, a solid electrolyte layer, and a negative electrode are stacked in this order, where the solid electrolyte layer is made of the solid electrolyte membrane.

[0068] The average thickness of the solid electrolyte membrane according to this embodiment is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 200 μm or less, and even more preferably 20 μm or more and 100 μm or less. When the average thickness of the solid electrolyte membrane is equal to or greater than the lower limit, chipping of the solid electrolyte and cracking of the surface of the solid electrolyte membrane can be further suppressed. Furthermore, when the average thickness of the solid electrolyte membrane is equal to or less than the upper limit, the impedance of the solid electrolyte membrane can be further reduced. As a result, the battery characteristics of the obtained all-solid-state lithium ion battery can be further improved.

[0069] The solid electrolyte membrane according to this embodiment is preferably a pressure-molded body of particulate solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to this embodiment described above. That is, it is preferable to pressurize the particulate solid electrolyte to form a solid electrolyte membrane having a certain strength due to the anchor effect between the solid electrolyte materials. By forming the solid electrolyte into a pressure-molded body, the solid electrolyte molecules bond together, further increasing the strength of the resulting solid electrolyte membrane, thereby further suppressing chipping of the solid electrolyte and cracks on the surface of the solid electrolyte membrane.

[0070] In the solid electrolyte membrane according to this embodiment, the content of the sulfide-based inorganic solid electrolyte material according to this embodiment described above is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, when the whole solid electrolyte membrane is 100% by mass. Thereby, the contact property between solid electrolytes is improved, and the interfacial contact resistance of the solid electrolyte membrane can be reduced. As a result, the lithium ion conductivity of the solid electrolyte membrane can be further improved. And by using such a solid electrolyte membrane excellent in lithium ion conductivity, the battery characteristics of the obtained all-solid-state lithium ion battery can be further improved. The upper limit of the content of the sulfide-based inorganic solid electrolyte material according to this embodiment described above in the solid electrolyte membrane according to this embodiment is not particularly limited, but is, for example, 100% by mass or less.

[0071] The planar shape of the solid electrolyte membrane is not particularly limited and can be appropriately selected according to the shapes of the electrodes and current collectors. For example, it can be rectangular.

[0072] Further, the solid electrolyte membrane according to this embodiment may contain a binder resin, but the content of the binder resin is preferably less than 0.5% by mass, more preferably 0.1% by mass or less, still more preferably 0.05% by mass or less, and even more preferably 0.01% by mass or less when the whole solid electrolyte membrane is 100% by mass. Further, it is even more preferable that the solid electrolyte membrane according to this embodiment substantially does not contain a binder resin, and most preferably does not contain a binder resin. Thereby, the contact property between solid electrolytes is improved, and the interfacial contact resistance of the solid electrolyte membrane can be reduced. As a result, the lithium ion conductivity of the solid electrolyte membrane can be further improved. And by using such a solid electrolyte membrane excellent in lithium ion conductivity, the battery characteristics of the obtained all-solid-state lithium ion battery can be improved. The phrase "substantially free of binder resin" means that the binder resin may be contained to an extent that does not impair the effects of the present embodiment. In addition, when an adhesive resin layer is provided between the solid electrolyte layer and the positive electrode or the negative electrode, the adhesive resin originating from the adhesive resin layer present in the vicinity of the interface between the solid electrolyte layer and the adhesive resin layer is excluded from the "binder resin in the solid electrolyte membrane."

[0073] The binder resin is a binder generally used in lithium-ion batteries to bind inorganic solid electrolyte materials together, and examples of such binders include polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, and polyimide.

[0074] The solid electrolyte membrane according to this embodiment can be obtained, for example, by depositing particulate solid electrolyte in the form of a film on the cavity surface of a mold or on the surface of a substrate, and then pressurizing the solid electrolyte deposited in the form of a film. The method for pressurizing the solid electrolyte is not particularly limited. For example, when a particulate solid electrolyte is deposited on the cavity surface of a mold, pressing using a mold and a stamping die can be used. When a particulate solid electrolyte is deposited on the surface of a substrate, pressing using a mold and a stamping die, roll pressing, flat plate pressing, or the like can be used. The pressure applied to the solid electrolyte is, for example, 10 MPa or more and 500 MPa or less.

[0075] If necessary, the inorganic solid electrolyte deposited in the form of a film may be heated while being pressurized. Heating and pressurizing causes fusion and bonding of the solid electrolytes, further increasing the strength of the resulting solid electrolyte film. As a result, chipping of the solid electrolyte and the occurrence of cracks on the surface of the solid electrolyte film can be further suppressed. The temperature to which the solid electrolyte is heated is, for example, 40°C or higher and 500°C or lower.

[0076] [Lithium-ion battery] FIG. 1 is a cross-sectional view showing an example of the structure of a lithium-ion battery 100 according to an embodiment of the present invention. The lithium-ion battery 100 according to this embodiment includes, for example, a positive electrode 110 including a positive electrode active material layer 101, an electrolyte layer 120, and a negative electrode 130 including a negative electrode active material layer 103. At least one of the positive electrode active material layer 101, the negative electrode active material layer 103, and the electrolyte layer 120 contains the sulfide-based inorganic solid electrolyte material according to this embodiment. It is preferable that all of the positive electrode active material layer 101, the negative electrode active material layer 103, and the electrolyte layer 120 contain the sulfide-based inorganic solid electrolyte material according to this embodiment. In this embodiment, unless otherwise specified, the layer including the positive electrode active material is referred to as the positive electrode active material layer 101. The positive electrode 110 may further include a current collector 105 in addition to the positive electrode active material layer 101, as necessary, or may not include the current collector 105. In this embodiment, unless otherwise specified, the layer including the negative electrode active material is referred to as the negative electrode active material layer 103. The negative electrode 130 may further include a current collector 105 in addition to the negative electrode active material layer 103, as necessary, or may not include the current collector 105. The shape of the lithium ion battery 100 according to this embodiment is not particularly limited, and may be a cylindrical shape, a coin shape, a square shape, a film shape, or any other shape.

[0077] The lithium-ion battery 100 according to this embodiment is manufactured according to a generally known method, for example, by forming a stack of the positive electrode 110, the electrolyte layer 120, and the negative electrode 130 into a cylindrical, coin-shaped, rectangular, film-shaped, or other arbitrary shape, and then sealing in a nonaqueous electrolyte solution as necessary.

[0078] (positive electrode) The positive electrode 110 is not particularly limited, and any electrode commonly used in lithium-ion batteries can be used. The positive electrode 110 is not particularly limited, and can be manufactured according to a commonly known method. For example, the positive electrode 110 can be obtained by forming a positive electrode active material layer 101 containing a positive electrode active material on the surface of a current collector 105 such as aluminum foil. The thickness and density of the positive electrode active material layer 101 are not particularly limited as they are determined appropriately depending on the intended use of the battery, and can be set in accordance with generally known information.

[0079] The positive electrode active material layer 101 contains a positive electrode active material. The positive electrode active material is not particularly limited, and generally known ones can be used. For example, composite oxides such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxides (Li2MnO3-LiMO2 (M = Co, Ni, etc.)), lithium-manganese-nickel oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), olivine-type lithium phosphate (LiFePO4), etc.; conductive polymers such as polyaniline and polypyrrole; sulfide-based positive electrode active materials such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, Li-V-S compounds, Li-Fe-S compounds; materials using sulfur as an active material such as acetylene black impregnated with sulfur, porous carbon impregnated with sulfur, and mixed powder of sulfur and carbon; etc. can be used. These positive electrode active materials may be used alone or in combination of two or more. Among these, sulfide-based positive electrode active materials are preferable from the viewpoints of having a higher discharge capacity density and being more excellent in cycle characteristics, and one or more selected from Li-Mo-S compounds, Li-Ti-S compounds, and Li-V-S compounds are more preferable.

[0080] Here, the Li-Mo-S compound contains Li, Mo, and S as constituent elements, and can usually be obtained by chemically reacting an inorganic composition containing molybdenum sulfide and lithium sulfide, which are raw materials, with each other by mechanical treatment. In addition, the Li-Ti-S compound contains Li, Ti, and S as constituent elements, and can usually be obtained by chemically reacting an inorganic composition containing titanium sulfide and lithium sulfide, which are raw materials, with each other by mechanical treatment. The Li-V-S compound contains Li, V, and S as constituent elements, and can usually be obtained by chemically reacting an inorganic composition containing vanadium sulfide and lithium sulfide, which are raw materials, with each other by mechanical treatment.

[0081] The positive electrode active material layer 101 is not particularly limited, but as components other than the above positive electrode active material, for example, it may contain one or more materials selected from a binder resin, a thickener, a conductive aid, a solid electrolyte material, and the like. Each material will be described below.

[0082] The positive electrode active material layer 101 may contain a binder resin that serves to bind the positive electrode active materials to each other and the positive electrode active material and the current collector 105. The binder resin according to this embodiment is not particularly limited as long as it is a normal binder resin that can be used in a lithium ion battery. For example, polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, polyimide, etc. may be mentioned. These binders may be used alone or in combination of two or more.

[0083] The positive electrode active material layer 101 may contain a thickener from the viewpoint of ensuring the fluidity of the slurry suitable for coating. The thickener is not particularly limited as long as it is a normal thickener that can be used in a lithium ion battery. For example, cellulose-based polymers such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose and their ammonium salts and alkali metal salts, polycarboxylic acids, polyethylene oxide, polyvinyl pyrrolidone, polyacrylate, water-soluble polymers such as polyvinyl alcohol, etc. may be mentioned. These thickeners may be used alone or in combination of two or more.

[0084] The positive electrode active material layer 101 may contain a conductive additive from the viewpoint of improving the conductivity of the positive electrode 110. The conductive additive is not particularly limited as long as it is a common conductive additive that can be used in lithium ion batteries, and examples thereof include carbon black such as acetylene black and Ketjen black, and carbon materials such as vapor-grown carbon fiber.

[0085] The positive electrode according to this embodiment may contain a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to this embodiment, or may contain a solid electrolyte containing a solid electrolyte material of a type different from the sulfide-based inorganic solid electrolyte material according to this embodiment. The solid electrolyte material of a type different from the sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited as long as it has ion conductivity and insulating properties, but materials generally used in lithium ion batteries can be used. Examples of such materials include inorganic solid electrolyte materials such as sulfide-based inorganic solid electrolyte materials, oxide-based inorganic solid electrolyte materials, and other lithium-based inorganic solid electrolyte materials; and organic solid electrolyte materials such as polymer electrolytes. More specifically, the inorganic solid electrolyte materials listed in the description of the solid electrolyte according to this embodiment can be used.

[0086] The blending ratio of the various materials in the positive electrode active material layer 101 is not particularly limited and can be determined appropriately depending on the intended use of the battery, and can be set in accordance with generally known information.

[0087] (Negative electrode) The anode 130 is not particularly limited, and any anode commonly used in lithium-ion batteries can be used. The anode 130 is not particularly limited, and can be manufactured according to a commonly known method. For example, the anode 130 can be obtained by forming an anode active material layer 103 containing an anode active material on the surface of a current collector 105 made of copper or the like. The thickness and density of the negative electrode active material layer 103 are not particularly limited as they are determined appropriately depending on the intended use of the battery, and can be set in accordance with generally known information.

[0088] The negative electrode active material layer 103 contains a negative electrode active material. The above-mentioned negative electrode active material is not particularly limited as long as it is a normal negative electrode active material that can be used for the negative electrode of a lithium-ion battery. For example, carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; lithium, lithium alloy, tin, tin alloy, silicon, silicon alloy, gallium, gallium alloy, indium, indium alloy, aluminum, aluminum alloy, etc. based metal-based materials; conductive polymers such as polyacene, polyacetylene, and polypyrrole; lithium titanium composite oxide (for example, Li4Ti5O 12 ) etc. can be mentioned. These negative electrode active materials may be used alone or in combination of two or more.

[0089] The negative electrode active material layer 103 is not particularly limited, but as components other than the above-mentioned negative electrode active material, for example, it may contain one or more materials selected from a binder resin, a thickener, a conductive aid, a solid electrolyte material, etc. These materials are not particularly limited, but for example, the same materials as those used for the above-mentioned positive electrode 110 can be mentioned. The blending ratio of various materials in the negative electrode active material layer 103 is not particularly limited because it is appropriately determined according to the use purpose of the battery, etc., and can be set according to generally known information.

[0090] The negative electrode according to this embodiment may contain a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to this embodiment, or may contain a solid electrolyte containing a solid electrolyte material of a type different from the sulfide-based inorganic solid electrolyte material according to this embodiment. The solid electrolyte material of a type different from the sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited as long as it has ion conductivity and insulation, but generally those used for lithium-ion batteries can be used. For example, inorganic solid electrolyte materials such as sulfide-based inorganic solid electrolyte materials, oxide-based inorganic solid electrolyte materials, and other lithium-based inorganic solid electrolyte materials; organic solid electrolyte materials such as polymer electrolytes can be mentioned. More specifically, the inorganic solid electrolyte materials mentioned in the description of the solid electrolyte according to this embodiment can be used.

[0091] (Electrolyte layer) Next, the electrolyte layer 120 will be described. The electrolyte layer 120 is a layer formed between the positive electrode active material layer 101 and the negative electrode active material layer 103. Examples of the electrolyte layer 120 include a separator impregnated with a non-aqueous electrolyte solution and a solid electrolyte layer containing a solid electrolyte.

[0092] The separator according to this embodiment is not particularly limited as long as it electrically insulates the positive electrode 110 and the negative electrode 130 and has a function of permeating lithium ions. For example, a porous membrane can be used.

[0093] As the porous membrane, a microporous polymer film is preferably used, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester, etc. In particular, a porous polyolefin film is preferable, and specifically, a porous polyethylene film, a porous polypropylene film, etc. can be mentioned.

[0094] The non-aqueous electrolyte solution is a solution in which an electrolyte is dissolved in a solvent. As the above electrolyte, any known lithium salt can be used and can be selected according to the type of active material. For example, LiClO4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 , LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiCF3SO3, LiC4F9SO3, Li(CF3SO2)2N, lithium lower fatty acid carboxylate, etc. can be mentioned.

[0095] The solvent for dissolving the above electrolyte is not particularly limited as long as it is a liquid commonly used for dissolving electrolytes, such as carbonates like ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), vinylene carbonate (VC), etc.; lactones like γ-butyrolactone, γ-valerolactone, etc.; ethers like trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, etc.; sulfoxides like dimethyl sulfoxide, etc.; oxolanes like 1,3-dioxolane, 4-methyl-1,3-dioxolane, etc.; nitrogen-containing compounds like acetonitrile, nitromethane, formamide, dimethylformamide, etc.; organic acid esters like methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.; triphosphate esters and diglymes; triglymes; sulfolanes like sulfolane, methyl sulfolane, etc.; oxazolidinones like 3-methyl-2-oxazolidinone, etc.; sultones like 1,3-propane sultone, 1,4-butane sultone, naphthalene sultone, etc. These may be used alone or in combination of two or more.

[0096] The solid electrolyte layer according to this embodiment is a layer formed between the positive electrode active material layer 101 and the negative electrode active material layer 103, and is a layer formed of a solid electrolyte containing a solid electrolyte material. The solid electrolyte contained in the solid electrolyte layer is not particularly limited as long as it has lithium ion conductivity, but in this embodiment, it is preferably a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to this embodiment. The content of the solid electrolyte in the solid electrolyte layer according to this embodiment is not particularly limited as long as the desired insulation can be obtained. For example, it is preferably in the range of 10% by volume or more and 100% by volume or less, and more preferably in the range of 50% by volume or more and 100% by volume or less. In particular, in this embodiment, it is preferable that the solid electrolyte layer is composed only of the solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to this embodiment.

[0097] In addition, the solid electrolyte layer according to this embodiment may contain a binder resin. By containing the binder resin, a flexible solid electrolyte layer can be obtained. Examples of the binder resin include fluorine-containing binders such as polytetrafluoroethylene and polyvinylidene fluoride. The thickness of the solid electrolyte layer is preferably in the range of 0.1 μm or more and 1000 μm or less, and more preferably in the range of 0.1 μm or more and 300 μm or less.

[0098] The embodiments of the present invention have been described above, but these are examples of the present invention, and various configurations other than the above can also be adopted. It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention.

Examples

[0099] Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0100] [1] Production of P2S5 <Example 1> As the raw material phosphorus pentasulfide composition, phosphorus pentasulfide manufactured by Perimeter Solutions (product name: Normal / S, melting point: 289.9 °C, crystallinity: 31%) was used. Next, the raw material diphosphorus pentasulfide composition was placed in a quartz container and set in a vacuum heating device (manufactured by Furukawa Co., Ltd.). Next, after repeating vacuum gas replacement three times, the container was heated at 200°C for 7 hours under a 10 ml / min flow of Ar gas. Next, the components that had accumulated at the bottom of the quartz container were collected and ground in an agate mortar for 5 minutes to obtain high-crystallinity diphosphorus pentasulfide composition 1. The obtained high-crystallinity diphosphorus pentasulfide composition 1 was subjected to various evaluations. The results are shown in Table 1.

[0101] <Example 2> As the raw material diphosphorus pentasulfide composition, diphosphorus pentasulfide manufactured by LIAONING RUIXING CHEMICAL GROUP (product name: SUPERIOR GRADE Powder, melting point: 287.6°C, crystallinity: 16.6%) was used. The raw material diphosphorus pentasulfide composition was then placed in a quartz container and placed in a vacuum heating device (manufactured by Furukawa Co., Ltd.). Vacuum and gas replacement were then repeated three times, followed by heating at 200°C for 7 hours under a 10 ml / min flow of Ar gas. The components that had accumulated at the bottom of the quartz container were then collected and ground in an agate mortar for 5 minutes to obtain high-crystallinity diphosphorus pentasulfide composition 2. The resulting high-crystallinity diphosphorus pentasulfide composition 2 was then evaluated. The results are shown in Table 1.

[0102] <Comparative Example 1> As the raw material diphosphorus pentasulfide composition, diphosphorus pentasulfide manufactured by LIAONING RUIXING CHEMICAL GROUP (product name: SUPERIOR GRADE Powder, melting point: 287.6°C, crystallinity: 16.6%) was used. The starting phosphorus pentasulfide composition was then placed in a quartz container and placed in a vacuum heating device (manufactured by Furukawa Co., Ltd.). It was then vacuum heated at 300°C for 2 hours under a reduced pressure of -0.094 MPa. The components that had accumulated at the bottom of the quartz container were then collected and ground in an agate mortar for 5 minutes to obtain phosphorus pentasulfide composition 3. The resulting phosphorus pentasulfide composition 3 was then evaluated. The results are shown in Table 1.

[0103] <Comparative Example 2> Diphosphorus pentasulfide Composition 4 was prepared as is from diphosphorus pentasulfide manufactured by LIAONING RUIXING CHEMICAL GROUP (product name: SUPERIOR GRADE Powder, melting point: 287.6°C, crystallinity: 16.6%). Various evaluations were performed on diphosphorus pentasulfide Composition 4. The results are shown in Table 1.

[0104] The diphosphorus pentasulfide compositions used in the examples and comparative examples, manufactured by LIAONING RUIXING CHEMICAL GROUP, are commercially available as high purity grades. Also,

[0105] [2] Manufacturing of sulfide-based inorganic solid electrolyte materials A sulfide-based inorganic solid electrolyte material was prepared by the following procedure. The raw materials used were Li2S powder (manufactured by Furukawa Co., Ltd., purity 99.9%), Li3N powder (manufactured by Furukawa Co., Ltd.), and P2S5 powder. As the P2S5 powder, the highly crystalline diphosphorus pentasulfide composition obtained in the example and the diphosphorus pentasulfide composition obtained in the comparative example were used, respectively. First, a rotary blade grinder and an alumina pot (internal volume 400 mL) were placed inside the glove box. Next, high-purity dry argon gas (H2O < 1 ppm, O2 < 1 ppm) obtained through a gas purification system was injected into the glove box and vacuum degassed three times. Next, in a glove box, a rotary blade mill (rotation speed: 18,000 rpm) was used to mix a total of 5 g of LiS powder, P2S5 powder, and Li3N powder (Li2S:P2S5:Li3N = 71.1:23.7:5.3 (mol%)) (10 cycles of mixing for 10 seconds and leaving for 10 seconds (cumulative mixing time: 100 seconds)), to prepare a raw material inorganic composition.

[0106] Next, the raw inorganic composition and 500 g of ZrO2 balls having a diameter of 10 mm were placed in an alumina pot (internal volume: 400 mL) in a glove box, and the pot was sealed. Next, an alumina pot was taken out from the glove box and attached to a ball mill machine installed in an atmosphere of dried dry air introduced through a membrane air dryer. Mechanochemical treatment was performed at 120 rpm for 500 hours to vitrify the raw material inorganic composition. Every time mixing was carried out for 48 hours, the powder adhering to the inner wall of the pot was scraped off in the glove box, and after sealing, milling was continued in a dried air atmosphere. Next, the alumina pot was placed in the glove box, and the obtained powder was transferred from the alumina pot to a carbon crucible, and annealed at 290 °C for 2 hours in a heating furnace installed in the glove box. Each evaluation was performed on the obtained sulfide-based inorganic solid electrolyte material. The obtained results are shown in Table 1.

[0107] [3] Measurement method In the following examples and comparative examples, the measurement methods performed on the diphosphorus pentasulfide composition and the sulfide-based inorganic solid electrolyte material will be described.

[0108] (Crystallinity) First, using an X-ray diffractometer (manufactured by Rigaku Corporation, RINT2000), under the conditions of a voltage of 40 kV, a current of 40 mA, a divergence slit of 1°, a vertical limit of the divergence slit of 10 mm, a scattering slit of 1°, a receiving slit of 0.3 mm, a measurement start angle of 3°, and a measurement end angle of 90°, the X-ray diffraction spectra of the highly crystalline diphosphorus pentasulfide composition obtained in the examples and the diphosphorus pentasulfide composition obtained in the comparative examples were respectively obtained by X-ray diffraction analysis. Note that CuKα rays were used as the radiation source. Also, the sample holder was a glass sample plate (CatNo.9200, sample part 20 mm × 20 mm, depth 0.5 mm). Next, using the following peak separation method, the crystallinity Xc of the diphosphorus pentasulfide compositions obtained in the examples and the comparative examples was calculated from the obtained X-ray diffraction spectra. First, without considering the effects of non-interference scattering, lattice disorder, etc., the X-ray diffraction pattern was separated into a crystalline diffraction curve and an amorphous halo by using the profile fitting method. For profile fitting, the analysis software attached to the X-ray diffractometer (manufactured by Rigaku Corporation, product name: Integrated Powder X-ray Analysis Software PDXL Application Analysis (Crystallinity)) was used. The specific procedure for calculating the crystallinity is as follows (see Figure 3; cited from Rigaku Corporation, X-ray Diffraction Handbook, February 21, 2000, Third Edition, P83, Figure 3.6.2). (1) Separation of background The X-ray intensities from the low-angle side to the high-angle side were connected by a straight line, and the area under the straight line was taken as the background. (2) Separation of halo The halo pattern due to the amorphous phase was estimated, and the halo was separated from the scattering curve after subtracting the background. (3) Separation of crystalline diffraction curve The crystalline diffraction curve was separated in the same manner as in (2) above. (4) Calculation of crystallinity Using the areas under the curves (integrated intensities) of the diffraction curve of the amorphous component (amorphous halo) and the diffraction curve of the crystalline component (crystalline diffraction curve) separated from the scattering curve, the crystallinity Xc was calculated from the following formula (2). Xc = {Ic / (Ic + Ia)} × 100 (2) Ic: Area under the curve (integrated intensity) of the diffraction curve of the crystalline component (crystalline diffraction curve) Ia: Area under the curve (integrated intensity) of the diffraction curve of the amorphous component (amorphous halo)

[0109] (Heat of fusion · Melting point) For the high-crystallinity diphosphorus pentasulfide composition obtained in the examples and the diphosphorus pentasulfide composition obtained in the comparative examples, the heat of fusion was measured using a differential scanning calorimeter. In an argon atmosphere, 20-25 mg of the diphosphorus pentasulfide composition was weighed into an aluminum pan, which was then covered with an aluminum lid and sealed with a sample sealer. The reference aluminum container was left empty. Differential scanning calorimetry was performed using a differential scanning calorimeter under the following conditions: starting temperature 25°C, measurement temperature range 30-350°C, heating rate 5°C / min, and argon atmosphere 100 ml / min. A DSC6300 (manufactured by Seiko Instruments Inc.) was used as the differential scanning calorimeter. In all of the examples and comparative examples, an endothermic peak was observed in the temperature range of 280°C to 300°C in the obtained DSC curve. The heat of fusion was calculated by determining the area enclosed by the base line and the endothermic curve of fusion containing an endothermic peak in the temperature range of 280°C to 300°C in the DSC curve thus obtained. The peak top of the endothermic peak in the temperature range of 280° C. to 300° C. was measured as the melting point.

[0110] (Phosphorus pentasulfide content) The high-crystallinity phosphorus pentasulfide compositions obtained in the examples and the phosphorus pentasulfide compositions obtained in the comparative examples were subjected to solid 31 The content of diphosphorus pentasulfide was measured using P-NMR spectrum. First, a test sample was filled into a 3.2 mm diameter measurement tube in a glove box purged with N2 gas, and the tube was rotated at a magic angle (54.7 degrees) relative to the external magnetic field (Magic Angle Spinning: MAS). Measurements were performed under the following conditions: Equipment: JEOL RESONANCE JNM-ECA-600 Observation frequency: 242.95MHz Pulse width: 90° pulse Pulse waiting time: 2800 seconds Accumulation count: 64 times Measurement mode: Single pulse method MAS speed: 12kHz Standard substance: (NH4)2HPO4·1.33ppm Test sample 31Regarding the peaks detected in the P-NMR spectrum, please refer to Reference 1 "Hellmut Eckert, Cheryl S. Liang and Galen D. Stucky: 31 P magic angle spinning NMR of crystalline phosphorous sulfides. Correlation of 31 P chemical shielding tensors with local environments, J. Phys. Chem, 1989, 93, 452-457, waveform separation was performed using a Gaussian function based on the following peak assignments, and the integral value of each peak was calculated. At this time, P2S5(P4S 10 The chemical shifts of P4S1, P4S2, P4S3, and P4S4 were set to 40-52 ppm, 52-70 ppm, 80-90 ppm, 90-100 ppm, and 110-115 ppm, respectively. The ratio of the integral value of the peak present at 40 to 52 ppm to the total integral value of each peak was calculated, and this ratio was taken as the content of diphosphorus pentasulfide.

[0111] (median diameter d 50 ) The particle size distribution of the phosphorus pentasulfide compositions obtained in the examples and the comparative examples was measured by a laser diffraction scattering method using a laser diffraction scattering particle size distribution analyzer (Malvern Instruments, Mastersizer 3000). From the measurement results, the median diameter d 50 asked for.

[0112] (Lithium ion conductivity) Using the high-crystallinity phosphorus pentasulfide compositions obtained in the Examples and the phosphorus pentasulfide compositions obtained in the Comparative Examples, sulfide-based inorganic solid electrolyte materials were produced according to the above procedure, and the lithium ion conductivity of the resulting powders was measured by the AC impedance method. The measurement of lithium ion conductivity was carried out using a potentiostat / galvanostat SP-300 manufactured by BioLogic. The sample size was 9.5 mm in diameter and 1.2 - 2.0 mm in thickness. The measurement conditions were an applied voltage of 10 mV, a measurement temperature of 27.0 °C, a measurement frequency range of 0.1 Hz to 7 MHz, and the electrodes were Li foils. Here, as samples for measuring lithium ion conductivity, a highly crystallized phosphorus pentasulfide composition obtained in the examples and a phosphorus pentasulfide composition obtained in the comparative examples were used to prepare a sulfide-based inorganic solid electrolyte material by the previous procedure. For 150 mg of the powder obtained therein, a plate-shaped sulfide-based inorganic solid electrolyte material with a diameter of 9.5 mm and a thickness of 1.2 - 2.0 mm obtained by pressing at 270 MPa for 10 minutes using a pressing device was used.

[0113] (Measurement of the maximum value of the oxidative decomposition current) A sulfide-based inorganic solid electrolyte material was prepared by the previous procedure using a highly crystallized phosphorus pentasulfide composition obtained in the examples and a phosphorus pentasulfide composition obtained in the comparative examples. Using a pressing device, 120 - 150 mg of the obtained powder was pressed at 270 MPa for 10 minutes to obtain a plate-shaped sulfide-based inorganic solid electrolyte material (pellet) with a diameter of 9.5 mm and a thickness of 1.3 mm. Then, a Li foil was press-bonded as a reference electrode / counter electrode to one surface of the obtained pellet under the conditions of 18 MPa for 10 minutes, and a SUS314 foil was adhered as a working electrode to the other surface. Next, using a potentiostat / galvanostat SP-300 manufactured by BioLogic, the maximum value of the oxidative decomposition current of the sulfide-based inorganic solid electrolyte material was determined under the conditions of a temperature of 25 °C, a sweep voltage range of 0 - 5 V, and a voltage sweep rate of 5 mV / second.

[0114] (Recovery rate) Using the masses of the highly crystallized phosphorus pentasulfide composition obtained in the examples and the phosphorus pentasulfide composition obtained in the comparative examples, and the mass of the raw material phosphorus pentasulfide composition, the recovery rate was calculated from the following formula (1). Recovery rate (%) = (M A / M B ) × 100 (1) M A : Mass (g) of the highly crystallized phosphorus pentasulfide composition M B : Mass (g) of raw material diphosphorus pentasulfide composition

[0115] [Table 1]

[0116] The method for producing the diphosphorus pentasulfide composition of the example achieved both a high degree of crystallinity and a high recovery rate. FIG. 2 shows the X-ray diffraction spectra of the phosphorus pentasulfide compositions obtained by the methods for producing phosphorus pentasulfide compositions of the Examples and Comparative Examples. FIG. 5 shows the DSC curve on the high temperature side, and FIG. 6 shows the DSC curve on the low temperature side. [Explanation of symbols]

[0117] 100 Lithium-ion batteries 101 Positive electrode active material layer 103 Negative electrode active material layer 105 Current collector 110 Positive electrode 120 Electrolyte layer 130 negative electrode

Claims

1. A method for producing a phosphorus pentasulfide composition, comprising a heating step of heat-treating a raw material phosphorus pentasulfide composition at a temperature of 130°C or higher and lower than the melting point of the raw material phosphorus pentasulfide composition, to obtain a high-crystallinity phosphorus pentasulfide composition having a higher crystallinity than the raw material phosphorus pentasulfide composition; a step of obtaining the high-crystallinity phosphorus pentasulfide composition by the method for producing a phosphorus pentasulfide composition; a step of preparing a raw material composition of a sulfide-based inorganic solid electrolyte material containing the high-crystallinity phosphorus pentasulfide composition and lithium sulfide; a step of vitrifying the raw material composition of the sulfide-based inorganic solid electrolyte material by mechanical treatment while chemically reacting the high-crystallinity phosphorus pentasulfide composition and the lithium sulfide as raw materials to obtain a glassy sulfide-based inorganic solid electrolyte material; A method for producing a sulfide-based inorganic solid electrolyte material, comprising the above steps.

2. The method for producing a sulfide-based inorganic solid electrolyte material according to Claim 1, wherein the crystallinity of the high-crystallinity phosphorus pentasulfide composition calculated from a spectrum obtained by X-ray diffraction using CuKα rays as a radiation source is 40% or more and 80% or less.

3. The method for producing a sulfide-based inorganic solid electrolyte material according to Claim 1 or 2, wherein the recovery rate of the high-crystallinity phosphorus pentasulfide composition in the step of obtaining the high-crystallinity phosphorus pentasulfide composition is 90% or more and 99% or less.

4. The method for producing a sulfide-based inorganic solid electrolyte material according to any one of Claims 1 to 3, wherein the heating time in the heating step is 0.5 hours or more and 24 hours or less.

5. The method for producing a sulfide-based inorganic solid electrolyte material according to any one of Claims 1 to 4, wherein the heating temperature in the heating step is 180°C or higher and 220°C or lower, and the heating time is 6 hours or more and 8 hours or less.

6. The method for producing a sulfide-based inorganic solid electrolyte material according to any one of Claims 1 to 5, wherein the heating step is performed in an inert gas atmosphere or a vacuum atmosphere.

7. The method for producing a sulfide-based inorganic solid electrolyte material according to Claim 6, wherein the heating step is performed in an inert gas atmosphere, and the inert gas in the inert gas atmosphere is argon gas.

Images