Diphosphorus pentasulfide composition, raw material composition for sulfide-based inorganic solid electrolyte material, and method for producing sulfide-based inorganic solid electrolyte material

Abstract

To provide a novel diphosphorus pentasulfide composition that is useful for the production of sulfide-based inorganic solid electrolyte material.SOLUTION: The diphosphorus pentasulfide composition of the present embodiment has a crystallinity degree calculated from a spectrum obtained by X-ray diffraction using CuKα ray as a radiation source, of 40% or more and 80% or less, and has an endothermic peak observed in a temperature region of 280°C or higher and 300°C or lower in a DSC curve of the diphosphorus pentasulfide composition obtained by measurement using a differential scanning calorimeter under the conditions of a starting temperature of 25°C, a measurement temperature range of 30 to 350°C, a temperature increasing rate of 5°C / min, and an argon atmosphere of 100 ml / min, and the amount of heat of fusion for the endothermic peak is 60 J / g or more and 100 J / g or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a diphosphorus pentasulfide composition, a raw material composition for a sulfide-based inorganic solid electrolyte material, a method for producing a sulfide-based inorganic solid electrolyte material, a sulfide-based inorganic solid electrolyte material, a solid electrolyte, a solid electrolyte membrane, and an all-solid-state lithium ion battery. [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 calculated from a spectrum obtained by X-ray diffraction measurement using CuKα radiation. The phosphorus pentasulfide composition having a crystallinity of 30% or more is characterized by the presence of low-boiling phosphorus sulfide compounds (PS, PS, and SO) in the phosphorus pentasulfide composition. 10 It is described that the crystallinity can be improved by vacuum heating or the like to reduce the amount of fluorine-containing compounds (e.g., fluorine-containing compounds) and improve the 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] Although sulfide-based inorganic solid electrolyte materials have excellent electrochemical stability and lithium ion conductivity, their lithium ion conductivity is inferior to that of electrolyte solutions. For these reasons, further improvements in the performance of sulfide-based inorganic solid electrolyte materials used in lithium-ion batteries are required, and there is also a need for diphosphorus pentasulfide compositions that are useful for producing sulfide-based inorganic solid electrolyte materials.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel diphosphorus pentasulfide composition that is useful for producing a sulfide-based inorganic solid electrolyte material. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to provide a phosphorus pentasulfide composition useful for producing a sulfide-based inorganic solid electrolyte material. As a result, the present inventors have focused on the degree of crystallinity and the heat of fusion, and have arrived at the present invention.

[0010] That is, according to the present invention, 1. A diphosphorus pentasulfide composition comprising: The crystallinity calculated from a spectrum obtained by X-ray diffraction using CuKα radiation as a radiation source is 40% or more and 80% or less, The present invention provides a diphosphorus pentasulfide composition having a heat of fusion of 60 J / g or more and 100 J / g or less, as measured using a differential scanning calorimeter under the following conditions: a starting 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 / min.

[0011] Further, according to the present invention, There is provided a raw material composition for a sulfide-based inorganic solid electrolyte material, which comprises the above diphosphorus pentasulfide composition and lithium sulfide.

[0012] Further, according to the present invention, There is provided a sulfide-based inorganic solid electrolyte material comprising a mechanically treated product of the above phosphorus pentasulfide composition and lithium sulfide.

[0013] Further, according to the present invention, There is provided a method for producing a sulfide-based inorganic solid electrolyte material, which includes a step of mechanically treating the raw material composition for the sulfide-based inorganic solid electrolyte material.

[0014] Further, according to the present invention, A solid electrolyte containing the sulfide-based inorganic solid electrolyte material is provided.

[0015] Further, according to the present invention, A solid electrolyte membrane containing the above solid electrolyte as a main component is provided.

[0016] Further, according to the present invention, An all-solid-state lithium ion battery including a positive electrode including a positive electrode active material layer, an electrolyte layer, and a negative electrode including a negative electrode active material layer, There is provided an all-solid-state lithium ion battery in which at least one of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer contains the sulfide-based inorganic solid electrolyte material. [Effects of the Invention]

[0017] According to the present invention, a novel diphosphorus pentasulfide composition useful for producing a sulfide-based inorganic solid electrolyte material can be provided. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view showing an example of the structure of a lithium-ion battery according to an embodiment of the present invention. [Figure 2]FIG. 1 shows X-ray diffraction spectra of the diphosphorus pentasulfide compositions obtained in the examples and comparative examples. [Figure 3] FIG. 1 is a diagram showing an X-ray diffraction spectrum for explaining a method (peak separation method) for calculating the crystallinity of a diphosphorus pentasulfide composition according to an embodiment of the present invention. [Figure 4] FIG. 10 is a diagram for explaining a baseline used when calculating the calorific value of an endothermic peak. [Figure 5] FIG. 1 shows DSC curves on the high temperature side of the diphosphorus pentasulfide compositions obtained in Examples and Comparative Examples. [Figure 6] FIG. 1 shows DSC curves at low temperatures for the diphosphorus pentasulfide compositions obtained in the Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are given the same reference numerals and their explanations will be omitted as appropriate. The drawings are schematic diagrams and do not correspond to the actual dimensional ratios. Numerical ranges "A to B" represent A or more and B or less unless otherwise specified.

[0020] [Phosphorus pentasulfide composition] First, the diphosphorus pentasulfide composition according to this embodiment will be described. The present embodiment is a diphosphorus pentasulfide composition having a crystallinity of 40% or more and 80% or less as calculated from a spectrum obtained by X-ray diffraction using CuKα radiation as a radiation source, and in a DSC curve of the diphosphorus pentasulfide composition obtained by measurement with a differential scanning calorimeter, an endothermic peak is observed in a temperature range of 280°C or more and 300°C or less, and the heat of fusion of the endothermic peak is 60 J / g or more and 100 J / g or less.

[0021] In order for the diphosphorus pentasulfide composition according to this embodiment to have the above-described crystallinity and heat of fusion, (i) Heating temperature of the starting phosphorus pentasulfide composition (ii) Heating time of the starting phosphorus pentasulfide composition (iii) Atmosphere during heating of raw material diphosphorus pentasulfide composition It is preferable to appropriately select the above three points. Preferred aspects of the heating temperature, heating time, and atmosphere in the heating step will be described later in the section [Method for producing diphosphorus pentasulfide composition], but for (i), a temperature of 130°C or higher and lower than the melting point of the starting diphosphorus pentasulfide composition is preferred, for (ii), a time of 0.5 hours to 24 hours is preferred, and for (iii), an inert gas atmosphere is preferred.

[0022] The diphosphorus pentasulfide composition of this embodiment has a crystallinity of 40% or more and 80% or less, as calculated from a spectrum obtained by X-ray diffraction using CuKα radiation as a radiation source. The lower limit of the crystallinity is 40% or more, preferably 45% or more, more preferably 50% or more, and particularly preferably 55% or more. The upper limit of the crystallinity is 80% or less, preferably 76% or less, more preferably 73% or less, and particularly preferably 70% or less.

[0023] The diphosphorus pentasulfide composition according to this embodiment has a crystallinity of at least the above lower limit, which allows the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material to be improved. The reason for this is not entirely clear, but it is thought that the diphosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.). The degree of crystallinity calculated from a spectrum obtained by X-ray diffraction using CuKα radiation as a radiation source is considered to represent an index of the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) in the diphosphorus pentasulfide composition. A higher degree of crystallinity is considered to indicate that the low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) have crystallized into diphosphorus pentasulfide. In other words, the higher the degree of crystallinity of the diphosphorus pentasulfide composition calculated from the X-ray diffraction spectrum, the higher the crystallinity of diphosphorus pentasulfide and the lower the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.). For the above reasons, the phosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling-point phosphorus sulfide compounds, and therefore, when the phosphorus pentasulfide composition according to this embodiment is used, the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material can be improved, which is thought to be useful for producing a sulfide-based inorganic solid electrolyte material.

[0024] Furthermore, since the diphosphorus pentasulfide composition according to this embodiment has a crystallinity of not more than the upper limit, the recovery rate of the diphosphorus pentasulfide composition can be made more favorable while favorably maintaining the lithium ion conductivity. The reason for this is not entirely clear, but it is thought that treatment that excessively increases the crystallinity causes the evaporation of not only low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) but also the target diphosphorus pentasulfide, resulting in a decrease in the recovery rate. Therefore, by setting the upper limit of the degree of crystallinity of the diphosphorus pentasulfide composition according to this embodiment to the above upper limit or less, excessive crystallization treatment can be prevented, and both a high recovery rate and lithium ion conductivity of the sulfide-based inorganic solid electrolyte material obtained using the diphosphorus pentasulfide composition can be achieved, and therefore the diphosphorus pentasulfide composition according to this embodiment is considered to be useful for producing a sulfide-based inorganic solid electrolyte material.

[0025] Here, a method for calculating the crystallinity of the diphosphorus pentasulfide composition will be described with reference to Fig. 4. Fig. 4 is a diagram showing an X-ray diffraction spectrum for illustrating a method for calculating the crystallinity of the diphosphorus pentasulfide composition according to this embodiment (peak separation method). First, in X-ray diffraction using CuKα radiation as the radiation source, the diffraction curve corresponding to crystalline materials has a sharp peak, while the diffraction curve corresponding to amorphous materials has a broad halo due to scattering. Therefore, the proportion of crystalline materials relative to the total of crystalline and amorphous materials can be calculated as the degree of crystallinity. In this embodiment, the peak separation method is used to calculate the degree of crystallinity. The profile fitting method is used to separate the peaks of the X-ray diffraction pattern (also called the scattering curve) into a crystalline diffraction curve and an amorphous halo, without taking into account the effects of incoherent scattering and lattice disorder. The analysis software provided with the X-ray diffractometer can be used for profile fitting. The specific procedure for calculating the crystallinity is as follows (see Figure 4; 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 (1) 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 (1) 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.

[0026] Furthermore, in the diphosphorus pentasulfide composition of this embodiment, an endothermic peak is observed in a temperature range of 280°C or higher and 300°C or lower in a DSC curve of the diphosphorus pentasulfide composition obtained by measurement with a differential scanning calorimeter, and the heat of fusion of the endothermic peak is 60 J / g or higher and 100 J / g or lower, with the lower limit of the heat of fusion of the endothermic peak being preferably 62 J / g or higher, more preferably 65 J / g or higher. The upper limit of the heat of fusion of the endothermic peak is preferably 97 J / g or less, more preferably 95 J / g or less, and even more preferably 90 J / g or less. Here, the endothermic peak observed in the temperature range of 280°C or higher and 300°C or lower is the melting point of diphosphorus pentasulfide (P2S5).

[0027] In the diphosphorus pentasulfide composition according to this embodiment, an endothermic peak is observed in a temperature range of 280°C or higher and 300°C or lower in a DSC curve, and the heat of fusion of the endothermic peak is equal to or higher than the lower limit, thereby enabling the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material to be improved. The reason for this is not entirely clear, but it is thought that the diphosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.). The heat of fusion of the endothermic peak measured by the above method is considered to represent an index of the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) in the diphosphorus pentasulfide composition. If this crystallinity is high, it is considered that the low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) have crystallized into diphosphorus pentasulfide. In other words, it is considered that the higher the crystallinity of the diphosphorus pentasulfide composition calculated from the X-ray diffraction spectrum, the higher the crystallinity of diphosphorus pentasulfide and the smaller the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.). For the above reasons, the phosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling-point phosphorus sulfide compounds, and therefore, when the phosphorus pentasulfide composition according to this embodiment is used, the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material can be improved, which is thought to be useful for producing a sulfide-based inorganic solid electrolyte material.

[0028] Furthermore, since the diphosphorus pentasulfide composition according to this embodiment has a heat of fusion that is equal to or less than the upper limit, the recovery rate of the diphosphorus pentasulfide composition can be made more favorable while favorably maintaining the lithium ion conductivity. The reason for this is not entirely clear, but it is thought that excessive crystallinity treatment results in evaporation of not only low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.), but also the target diphosphorus pentasulfide, resulting in a decrease in recovery rate. Therefore, by setting the upper limit of the degree of crystallinity of the diphosphorus pentasulfide composition according to this embodiment to the above upper limit or less, excessive crystallization treatment can be prevented, and both a high recovery rate and lithium ion conductivity of the sulfide-based inorganic solid electrolyte material obtained using the diphosphorus pentasulfide composition can be achieved, and therefore the diphosphorus pentasulfide composition according to this embodiment is considered to be useful for producing a sulfide-based inorganic solid electrolyte material.

[0029] The DSC curve can be measured, for example, by the following method. First, 20-25 mg of the diphosphorus pentasulfide composition is weighed into an aluminum pan in an argon atmosphere, 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 following conditions: starting temperature 25°C, measurement temperature range 30-350°C, heating rate 5°C / min, and argon atmosphere 100 ml / min. The differential scanning calorimeter is not particularly limited, but for example, a DSC6300 manufactured by Seiko Instruments Inc. can be used. When the phosphorus pentasulfide composition contains a solvent, it is preferable to dry and remove the solvent from the phosphorus pentasulfide composition before measurement. From the DSC curve thus obtained, it is possible to observe whether or not an endothermic peak is present in the temperature range of 280°C or higher and 300°C or lower. The heat of fusion of the endothermic peak is calculated by determining the area enclosed by the endothermic curve including the endothermic peak and the baseline. Because the heat capacity inherent to a substance differs before and after the thermal change, the baselines before and after the endothermic peak are not linear. Therefore, in this embodiment, the baseline at the endothermic peak is defined as the line connecting points R and S shown in Figure 4. Point R is the intersection point between a line that passes through intersection point P between the baseline before the endothermic peak and the tangent to the endothermic peak and is parallel to the Y-axis, and the melting endothermic curve. Point S is the intersection point between a line that passes through intersection point Q between the baseline after the endothermic peak and the tangent to the endothermic peak and is parallel to the Y-axis, and the melting endothermic curve. Furthermore, in the diphosphorus pentasulfide composition according to this embodiment, there is usually one endothermic peak observed in the temperature range of 280°C or higher and 300°C or lower.

[0030] In order to further improve the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material, the diphosphorus pentasulfide composition according to this embodiment preferably does not exhibit an exothermic peak in the temperature range of at least 120°C to 140°C in the DSC curve, and more preferably does not exhibit an exothermic peak in the temperature range of at least 30°C to 280°C in the DSC curve. In this embodiment, "no peak is observed in the DSC curve" means that no peak with a calorific value of 0.3 J / g or more, preferably 0.1 J / g or more is observed. In this embodiment, the calorific value of the exothermic peak and the baseline at the exothermic peak can be defined in the same manner as the calorific value of the endothermic peak and the baseline at the endothermic peak described above.

[0031] 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, components contained in addition to phosphorus pentasulfide (P2S5) include P4S9, P4S7, and P4S3. In this case, the lower limit of the diphosphorus pentasulfide content in the diphosphorus pentasulfide composition according to this embodiment is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, when the total content of P2S5, P4S9, P4S7, and P4S3 in the phosphorus sulfide composition is taken as 100% by mass. By ensuring that the lower limit of the diphosphorus pentasulfide content is equal to or greater than the above lower limit, the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material can be further improved. The upper limit of the diphosphorus pentasulfide content in the diphosphorus pentasulfide composition according to this embodiment is not particularly limited, but is, for example, 100% by mass or less. The content of diphosphorus pentasulfide contained in the diphosphorus pentasulfide composition is, for example, 31 It can be calculated from P-NMR spectrum.

[0032] 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 tube in a glove box purged with N2 gas, and the tube is rotated at a magic angle (54.7 degrees) relative to the external magnetic field (Magic Angle Spinning: MAS), and measurements are 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 31 Regarding the peaks detected in the P-NMR spectrum, please refer to Reference 1 "Hellmut Eckert, Cheryl S. Liang and Galen D. Stucky: 31P 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 peak assignments below, and the integral value of each peak was calculated. The integral value of the peak derived from each component is proportional to the number of moles of phosphorus contained. Therefore, the content ratio can be calculated from the obtained integral value and the molecular weight of each component. The chemical shifts of P2S5 are 40-52 ppm, those of P4S9 are 52-70 ppm, those of P4S7 are 80-90 ppm, 90-100 ppm, and 110-115 ppm, and those of P4S3 are 80-90 ppm and 90-100 ppm.

[0033] In the diphosphorus pentasulfide composition according to this embodiment, 31 When measuring the P-NMR spectrum, it is preferable that no peak is observed in the range of 52 ppm to 70 ppm. In other words, it is preferable that no peak of P4S9 is 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.

[0034] In the diphosphorus pentasulfide composition according to this embodiment, 31 When 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.

[0035] The phosphorus pentasulfide composition according to this embodiment is preferably in a powder form. Since the production of a sulfide-based inorganic solid electrolyte material, which will be described later, is generally carried out by a dry method, if the phosphorus pentasulfide composition according to this embodiment is in a powder form, the production of the sulfide-based inorganic solid electrolyte material becomes easier.

[0036] The diphosphorus pentasulfide composition according to this embodiment has a median diameter d at a cumulative frequency of 50% in a volume-based cumulative frequency distribution curve measured using a laser diffraction / scattering particle size distribution analyzer. 50 However, it is preferably 1 μm or more and 150 μm or less, more preferably 3 μm or more and 100 μm or less, and further preferably 5 μm or more and 75 μm or less. Median diameter d of phosphorus pentasulfide composition 50 By setting the value of the total weight of the sulfide-based inorganic solid electrolyte material to within the above range, the handling property during production of the sulfide-based inorganic solid electrolyte material is improved, and the reaction efficiency during production of the sulfide-based inorganic solid electrolyte material is improved, thereby making it possible to improve the production efficiency of the sulfide-based inorganic solid electrolyte material.

[0037] [Method of producing diphosphorus pentasulfide composition] Next, a method for producing the diphosphorus pentasulfide composition according to this embodiment will be described. The method for producing the diphosphorus pentasulfide composition according to this embodiment differs from conventional methods for producing diphosphorus pentasulfide compositions. That is, the high-crystallinity diphosphorus pentasulfide composition according to this embodiment can only be obtained by employing a manufacturing technique that involves heat-treating the starting diphosphorus pentasulfide composition to reduce the amount of low-boiling-point phosphorus sulfide compounds (e.g., P4S3 and P4S7) in the starting diphosphorus pentasulfide composition. However, the method for producing the diphosphorus pentasulfide composition according to this embodiment can employ, for example, various specific production conditions, provided that the above-mentioned ingenious manufacturing techniques are adopted.

[0038] The method for producing a phosphorus pentasulfide composition according to this embodiment includes a heating step of heat-treating a raw material phosphorus pentasulfide composition at a temperature of 130°C or higher but lower than the melting point of the raw material phosphorus pentasulfide composition, thereby obtaining a high-crystallinity phosphorus pentasulfide composition having a higher degree of crystallinity than the raw material phosphorus pentasulfide composition. By adopting the above-described configuration, the method for producing a diphosphorus pentasulfide composition according to this embodiment involves heating the raw material diphosphorus pentasulfide composition at a temperature below the melting point thereof, thereby minimizing evaporation of diphosphorus pentasulfide contained in the diphosphorus pentasulfide composition and effectively removing only low-boiling-point phosphorus sulfide compounds (PS3, PS7, etc.).

[0039] The method for producing the diphosphorus pentasulfide composition according to this embodiment will be described in more detail below.

[0040] (Heating process) In the method for producing a phosphorus pentasulfide composition according to this embodiment, the starting phosphorus pentasulfide composition is heat-treated to reduce the amount of low-boiling phosphorus sulfide compounds (e.g., P4S3, P4S7) in the starting phosphorus pentasulfide composition, thereby improving the crystallinity of the starting phosphorus pentasulfide composition. This allows for the production of a high-crystallinity phosphorus pentasulfide composition having a higher degree of crystallinity than the starting phosphorus pentasulfide composition according to this embodiment. Here, when the starting phosphorus pentasulfide composition is heated, the component that does not evaporate and accumulates at the bottom of the container is typically the high-crystallinity phosphorus pentasulfide composition according to this embodiment.

[0041] Here, the lower limit of the heating temperature in the heating step is preferably 130° C. or higher, more preferably 150° C. or higher, and even more preferably 180° C. or higher. By setting the heating temperature to the above lower limit or higher, the crystallinity of the high-crystallinity diphosphorus pentasulfide composition can be made more suitable. The upper limit of the heating temperature in the heating step is preferably below the melting point of the starting diphosphorus pentasulfide composition, more preferably 250° C. or lower, and even more preferably 220° C. or lower. By setting the heating temperature to the upper limit or lower, the recovery rate of the high-crystallinity diphosphorus pentasulfide composition can be made more favorable. The melting point of the starting diphosphorus pentasulfide composition can be confirmed by the DSC curve described below.

[0042] In the method for producing the diphosphorus pentasulfide composition according to this embodiment, a diphosphorus pentasulfide composition having both a high degree of crystallinity and a high recovery rate can be obtained by heat-treating the raw material diphosphorus pentasulfide composition within a temperature range not lower than the above-mentioned lower limit and not higher than the above-mentioned upper limit. The reason for this is not entirely clear, but it is thought that the method for producing a diphosphorus pentasulfide composition according to this embodiment involves heating the raw material diphosphorus pentasulfide composition to a temperature below the melting point, temporarily destabilizing its structure and facilitating the transformation of diphosphorus pentasulfide from a glassy state into a more stable crystalline state, and also removing only low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.), thereby minimizing the evaporation of diphosphorus 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.

[0043] 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. The recovery rate refers to the ratio of the mass of the high-crystallinity diphosphorus pentasulfide composition after heating to the mass of the raw material diphosphorus pentasulfide composition, and can be calculated using the following formula (1). Recovery rate (%) = (M A / M B )×100 (1) M A : Mass (g) of highly crystalline phosphorus pentasulfide composition M B : Mass (g) of raw material diphosphorus pentasulfide composition

[0044] In the method for producing a diphosphorus pentasulfide composition according to this embodiment, the lower limit of the heating time for the starting diphosphorus pentasulfide composition in the heating step is preferably 0.5 hours or more, more preferably 3 hours or more, even more preferably 5 hours or more, and particularly preferably 6 hours or more. By setting the heating time to the above lower limit or more, the crystallinity of the high-crystallinity diphosphorus pentasulfide composition can be made more suitable. The upper limit of the heating time is preferably 24 hours or less, more preferably 12 hours or less, even more preferably 10 hours or less, and particularly preferably 8 hours or less. By keeping the heating time at or below the upper limit, the recovery rate of the high-crystallinity diphosphorus pentasulfide composition can be made more favorable.

[0045] In the method for producing a diphosphorus pentasulfide composition according to this embodiment, the heating temperature and heating time can be appropriately determined depending on the processing amount of the raw material diphosphorus pentasulfide composition, the desired recovery rate and physical properties of the high-crystallinity diphosphorus pentasulfide composition to be produced, etc. Among these, from the viewpoint of a balance between the recovery rate and the crystallinity of the high-crystallinity diphosphorus pentasulfide composition, it is preferable that the heating temperature be 180°C or higher and 220°C or lower and the heating time be 6 hours or higher and 8 hours or lower.

[0046] In the method for producing a diphosphorus pentasulfide composition according to this embodiment, the heating step is preferably carried out under an inert gas atmosphere or a vacuum atmosphere, and more preferably under an inert gas atmosphere. By adopting this configuration, it is possible to prevent reaction with components in the air or moisture, and to prevent the generation of impurities in the diphosphorus pentasulfide composition. In particular, carrying out the heating step under an inert gas atmosphere is preferred from the viewpoint of easily maintaining the atmosphere in the heating device. Note that a vacuum atmosphere refers to a pressure in the heating device of -0.01 MPa or less.

[0047] Examples of inert gases used in the heating step include argon gas, helium gas, and nitrogen gas. Among these, argon gas is particularly preferred. These inert gases are preferably as pure as possible to prevent impurities from being mixed into the product, and their dew point is preferably −70° C. or lower, and particularly preferably −80° C. or lower, to avoid contact with moisture. The method for introducing the inert gas into the mixed system is not particularly limited as long as the mixed system is filled with an inert gas atmosphere, and examples include a method of purging the inert gas and a method of continuously introducing a constant amount of inert gas.

[0048] [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.

[0049] 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.

[0050] 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. The upper limit of the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited, but is, for example, 3.0 × 10 -3 S cm -1 is less than 2.8 x 10 -3 S cm -1 is less than or equal to 2.5 x 10 -3 S cm -1 The following is the result.

[0051] The sulfide-based inorganic solid electrolyte material according to this embodiment may be in the form of particles, for example. The particulate sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited, but may be a particle having a median diameter d at a cumulative frequency of 50% in a volume-based cumulative frequency distribution curve measured using a laser diffraction / scattering particle size distribution measuring device. 50 However, it is preferably 1 μm or more and 100 μm or less, more preferably 3 μm or more and 80 μm or less, and further preferably 5 μm or more and 60 μm or less. Median diameter d of sulfide-based inorganic solid electrolyte material 50By setting the value of the total mass of the polymer in the above range, it is possible to maintain good handling properties and further improve the lithium ion conductivity.

[0052] 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.

[0053] 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.

[0054] [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.

[0055] (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 when mixing the raw materials, such as the stirring speed, treatment time, temperature, reaction pressure, and gravitational acceleration applied to the mixture, can be appropriately determined depending on the amount of the mixture to be treated.

[0056] 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.

[0057] 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 the present embodiment is not particularly limited, and may be commercially available lithium nitride (e.g., LiN, etc.), or may be lithium nitride obtained by reacting metallic lithium (e.g., Li foil) with nitrogen gas. From the viewpoint of obtaining a high-purity solid electrolyte material and suppressing side reactions, it is preferable to use lithium nitride with few impurities.

[0058] (Step (B) of obtaining a glassy sulfide-based inorganic solid electrolyte material) Next, the raw material composition of the sulfide-based inorganic solid electrolyte material is mechanically treated to vitrify the raw materials, the diphosphorus pentasulfide composition and lithium sulfide, while causing a chemical reaction, thereby obtaining a sulfide-based inorganic solid electrolyte material in a glassy state.

[0059] Here, mechanical treatment is a method of vitrifying a target composition by mechanically colliding two or more inorganic compounds to cause a chemical reaction, such as mechanochemical treatment, etc. Here, mechanochemical treatment is a method of vitrifying a target composition by applying mechanical energy such as shear force or collision force to the target composition. In addition, in the step (B), the mechanochemical treatment is preferably a dry mechanochemical treatment, from the viewpoint of easily realizing an environment in which moisture and oxygen are removed to a high level. By using the mechanochemical treatment, the raw materials can be mixed while being pulverized into fine particles, thereby increasing the contact area between the raw materials, thereby accelerating the reaction between the raw materials, and thereby enabling the sulfide-based inorganic solid electrolyte material according to this embodiment to be obtained more efficiently.

[0060] 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.

[0061] 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.

[0062] 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 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.

[0063] (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.

[0064] 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.

[0065] Furthermore, the sulfide-based inorganic solid electrolyte material in a glassy state is preferably heated, for example, in an inert gas atmosphere, which can prevent deterioration (for example, oxidation) of the sulfide-based inorganic solid electrolyte material. Examples of inert gases used when heating a sulfide-based inorganic solid electrolyte material in a glassy state include argon gas, helium gas, and nitrogen gas. These inert gases are preferably as pure as possible to prevent impurities from being mixed into the product, and their dew points are preferably −70° C. or lower, and particularly preferably −80° C. or lower, to avoid contact with moisture. The method for introducing the inert gas into the mixture system is not particularly limited as long as the mixture system is filled with an inert gas atmosphere, and examples include a method of purging the inert gas and a method of continuously introducing a constant amount of inert gas.

[0066] (Process (D) of crushing, classifying, or granulating) In the method for producing a sulfide-based inorganic solid electrolyte material according to this embodiment, the obtained sulfide-based inorganic solid electrolyte material may further be subjected to a process of pulverization, classification, or granulation, if necessary. For example, a sulfide-based inorganic solid electrolyte material having a desired median size can be obtained by pulverizing the material to fine particles and then adjusting the median size by classification or granulation. The pulverization method is not particularly limited, and known pulverization methods such as a mixer, airflow pulverization, mortar, rotary mill, and coffee mill can be used. The classification method is also not particularly limited, and known methods such as sieving can be used. The pulverization or classification is preferably carried out in an inert gas atmosphere or a vacuum atmosphere, since this can prevent contact with moisture in the air.

[0067] In order to obtain the sulfide-based inorganic solid electrolyte material according to this embodiment, it is important to appropriately adjust each of the above steps. However, the method for producing the sulfide-based inorganic solid electrolyte material according to this embodiment is not limited to the above method, and the sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained by appropriately adjusting various conditions.

[0068] [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.

[0069] 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.

[0070] Examples of sulfide-based inorganic solid electrolyte materials different from the sulfide-based inorganic solid electrolyte material according to the present embodiment include a LiS-P2S5 material, a LiS-SiS2 material, a LiS-GeS2 material, a LiS-Al2S3 material, a LiS-SiS2-Li3PO4 material, a LiS-P2S5-GeS2 material, a LiS-Li2O-P2S5-SiS2 material, a LiS-GeS2-P2S5-SiS2 material, a LiS-SnS2-P2S5-SiS2 material, a LiS-P2S5-Li3N material, and LiS 2+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 with each other by mechanical treatment in an inorganic composition containing them. Here, in the present embodiment, lithium sulfide includes polysulfide lithium.

[0071] Examples of the oxide-based inorganic solid electrolyte material include NASICON types such as LiTi2(PO4)3, LiZr2(PO4)3, LiGe2(PO4)3, and 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 inorganic solid electrolyte materials.

[0072] 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.

[0073] [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 contains a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to the present embodiment described above.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] The content of the sulfide-based inorganic solid electrolyte material according to the present embodiment in the solid electrolyte membrane according to the present embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, even 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 entire solid electrolyte membrane is taken as 100% by mass. This improves contact between solid electrolytes and reduces the interfacial contact resistance of the solid electrolyte membrane. As a result, the lithium ion conductivity of the solid electrolyte membrane can be further improved. Furthermore, by using such a solid electrolyte membrane with excellent lithium ion conductivity, the battery characteristics of the resulting 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 in the solid electrolyte membrane according to this embodiment is not particularly limited, but is, for example, 100 mass % or less.

[0078] The planar shape of the solid electrolyte membrane is not particularly limited and can be appropriately selected in accordance with the shapes of the electrodes and current collectors, but can be, for example, rectangular.

[0079] 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 mass%, more preferably 0.1 mass% or less, even more preferably 0.05 mass% or less, and even more preferably 0.01 mass% or less, when the entire solid electrolyte membrane is taken as 100 mass%. It is even more preferable that the solid electrolyte membrane according to this embodiment does not substantially contain a binder resin, and most preferably does not contain a binder resin. This improves contact between solid electrolytes and reduces the interfacial contact resistance of the solid electrolyte membrane. As a result, the lithium ion conductivity of the solid electrolyte membrane can be further improved. Furthermore, by using such a solid electrolyte membrane with excellent lithium ion conductivity, the battery characteristics of the resulting 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."

[0080] 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.

[0081] 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.

[0082] 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.

[0083] [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.

[0084] 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.

[0085] (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.

[0086] 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 materials can be used. For example, lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), solid solution oxide (LiMnO-LiMO (M=Co, Ni, etc.)), lithium manganese nickel oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Examples of the cathode active materials that can be used include composite oxides such as lithium phosphate oxide (LiFePO4), olivine-type lithium phosphate oxide (LiFePO4), and conductive polymers such as polyaniline and polypyrrole; sulfide-based cathode active materials such as LiS, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, Li-VS compounds, and Li-Fe-S compounds; and sulfur-based active materials such as sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, and mixed powders of sulfur and carbon. These cathode active materials may be used alone or in combination of two or more. Among these, sulfide-based positive electrode active materials are preferred from the viewpoint of having a higher discharge capacity density and superior cycle characteristics, and one or more selected from Li-Mo-S compounds, Li-Ti-S compounds, and Li-VS compounds are more preferred.

[0087] Here, the Li-Mo-S compound contains Li, Mo, and S as constituent elements, and can usually be obtained by mechanically treating an inorganic composition containing the raw materials molybdenum sulfide and lithium sulfide to cause a chemical reaction between them. Li-Ti-S compounds contain Li, Ti, and S as constituent elements, and are typically obtained by mechanically treating inorganic compositions containing titanium sulfide and lithium sulfide as raw materials to cause a chemical reaction between them. Li-VS compounds contain the constituent elements Li, V, and S, and are typically obtained by mechanically treating the raw materials, vanadium sulfide and an inorganic composition containing lithium sulfide, to cause a chemical reaction between them.

[0088] The positive electrode active material layer 101 is not particularly limited, and may contain, as a component other than the positive electrode active material, one or more materials selected from, for example, a binder resin, a thickener, a conductive additive, a solid electrolyte material, etc. Each material will be described below.

[0089] The positive electrode active material layer 101 may contain a binder resin that functions to bind the positive electrode active materials together and between the positive electrode active material and the current collector 105 . The binder resin according to the present embodiment is not particularly limited as long as it is a typical binder resin that can be used in lithium ion batteries, and examples thereof include polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, polyimide, etc. These binders may be used alone or in combination of two or more.

[0090] The positive electrode active material layer 101 may contain a thickener to ensure the fluidity of the slurry suitable for application. The thickener is not particularly limited as long as it is a typical thickener that can be used in lithium-ion batteries, and examples thereof include cellulose-based polymers such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose, as well as ammonium salts and alkali metal salts thereof, and water-soluble polymers such as polycarboxylic acids, polyethylene oxide, polyvinylpyrrolidone, polyacrylates, and polyvinyl alcohol. These thickeners may be used alone or in combination.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] (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.

[0095] The negative electrode active material layer 103 contains a negative electrode active material. The negative electrode active material is not particularly limited as long as it is a common negative electrode active material that can be used in the negative electrode of a lithium ion battery, and examples thereof include carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; metal-based materials mainly composed of lithium, lithium alloys, tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, and aluminum alloys; conductive polymers such as polyacene, polyacetylene, and polypyrrole; and lithium titanium composite oxides (e.g., Li4Ti5O12). These negative electrode active materials may be used alone or in combination of two or more.

[0096] The negative electrode active material layer 103 is not particularly limited, but may contain, as a component other than the negative electrode active material, one or more materials selected from, for example, a binder resin, a thickener, a conductive additive, a solid electrolyte material, etc. These materials are not particularly limited, but may include, for example, the same materials as those used for the positive electrode 110 described above. The blending ratio of the various materials in the negative electrode active material layer 103 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.

[0097] (electrolyte layer) Next, a description will be given of the electrolyte layer 120. The electrolyte layer 120 is a layer formed between the positive electrode active material layer 101 and the negative electrode active material layer 103. The electrolyte layer 120 may be a separator impregnated with a non-aqueous electrolyte solution or a solid electrolyte layer containing a solid electrolyte.

[0098] The separator according to this embodiment is not particularly limited as long as it electrically insulates the positive electrode 110 from the negative electrode 130 and allows lithium ions to pass through, but for example, a porous membrane can be used.

[0099] 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 preferred, and specific examples include a porous polyethylene film, a porous polypropylene film, etc.

[0100] The non-aqueous electrolyte solution is a solution in which an electrolyte is dissolved in a solvent. Any known lithium salt can be used as the electrolyte, and it can be selected depending on 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 carboxylates of lower fatty acids, etc.

[0101] The solvent for dissolving the electrolyte is not particularly limited as long as it is a solvent that is commonly used as a liquid for dissolving electrolytes, and examples thereof include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; Examples of suitable organic solvents include sulfoxides such as dimethyl sulfoxide, oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane, nitrogen-containing compounds such as acetonitrile, nitromethane, formamide, and dimethylformamide, organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate, phosphate triesters and diglymes, triglymes, sulfolanes such as sulfolane and methylsulfolane, oxazolidinones such as 3-methyl-2-oxazolidinone, and sultones such as 1,3-propane sultone, 1,4-butane sultone, and naphthasultone. These may be used alone or in combination of two or more.

[0102] 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 preferable that the solid electrolyte contains 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 insulating properties are obtained, but is preferably, for example, 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 a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to this embodiment.

[0103] The solid electrolyte layer according to this embodiment may also contain a binder resin. By including a binder resin, a flexible solid electrolyte layer can be obtained. Examples of binder resins 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 to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm.

[0104] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted. The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0105] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0106] [1] Manufacturing of P2S5 Example 1 As the raw material diphosphorus pentasulfide composition, diphosphorus pentasulfide manufactured by Perimeter Solutions (product name: Normal / S, melting point: 289.9°C, crystallinity: 31%) 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 a powdered high-crystallinity diphosphorus pentasulfide composition 1. The resulting high-crystallinity diphosphorus pentasulfide composition 1 was then evaluated. The results are shown in Table 1.

[0107] <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 set 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 a powdered high-crystallinity diphosphorus pentasulfide composition 2. The resulting high-crystallinity diphosphorus pentasulfide composition 2 was then evaluated. The results are shown in Table 1.

[0108] <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. 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.). 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 a powdered diphosphorus pentasulfide composition 3. The obtained diphosphorus pentasulfide composition 3 was subjected to various evaluations. The results are shown in Table 1.

[0109] <Comparative Example 2> Powdered diphosphorus pentasulfide manufactured by LIAONING RUIXING CHEMICAL GROUP (product name: SUPERIOR GRADE Powder, melting point: 287.6°C, crystallinity: 16.6%) was used as is as diphosphorus pentasulfide composition 4. Diphosphorus pentasulfide composition 4 was evaluated in various ways. The results are shown in Table 1.

[0110] The raw material diphosphorus pentasulfide compositions used in the examples and comparative examples, manufactured by LIAONING RUIXING CHEMICAL GROUP, are commercially available as high purity grades.

[0111] [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%)) (the operation of mixing for 10 seconds and leaving for 10 seconds was repeated 10 times (cumulative mixing time: 100 seconds)), thereby preparing a raw material composition of a sulfide-based inorganic solid electrolyte material (hereinafter referred to as the "raw material composition").

[0112] Next, the raw material composition and 500 g of ZrO2 balls with a diameter of 10 mm were placed in an alumina pot (internal volume: 400 mL) in a glove box, and the pot was sealed. The alumina pot was then removed from the glove box, attached to a ball mill placed in an atmosphere of dry air introduced through a membrane air dryer, and subjected to mechanochemical treatment at 120 rpm for 500 hours to vitrify the raw material composition. Every 48 hours of mixing, 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 dry air atmosphere. Next, an 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. The obtained sulfide-based inorganic solid electrolyte material was evaluated. The results are shown in Table 1.

[0113] [3]Measurement method In the following examples and comparative examples, the measurement methods performed on the phosphorus pentasulfide composition and the sulfide-based inorganic solid electrolyte material will be described.

[0114] (crystallinity) First, an X-ray diffraction analysis was performed using an X-ray diffractometer (Rigaku Corporation, RINT2000) under the following conditions: voltage 40 kV, current 40 mA, divergence slit 1°, divergence slit vertical limit 10 mm, scattering slit 1°, receiving slit 0.3 mm, measurement start angle 3°, and measurement end angle 90°. The X-ray diffraction spectra of the high-crystallinity phosphorus pentasulfide compositions obtained in the examples and the comparative examples were obtained. CuKα radiation was used as the radiation source. The sample holder was a glass sample plate (Cat. No. 9200, sample area 20 mm × 20 mm, depth 0.5 mm). Next, the crystallinity Xc of the high-crystallinity diphosphorus pentasulfide compositions obtained in the examples and the diphosphorus pentasulfide compositions obtained in the comparative examples was calculated from the obtained X-ray diffraction spectra using the following peak separation method. First, the X-ray diffraction pattern was separated into crystalline diffraction curves and amorphous halos using a profile fitting technique, without considering the effects of incoherent scattering and lattice disorder, etc. Profile fitting was performed using the analysis software provided with the X-ray diffractometer (Rigaku Corporation, product name: Integrated Powder X-ray Analysis Software PDXL Applied Analysis (Crystallinity)). 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 was drawn connecting the X-ray intensities from the low angle side to the high angle side, and the area under the line was taken as the background. (2) Halo separation The amorphous halo pattern was estimated and the halo was isolated from the background-subtracted scattering curve. (3) Separation of crystalline diffraction curves The crystalline diffraction curve was separated in the same manner as in (2) above. (4) Calculation of crystallinity The crystallinity Xc was 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)

[0115] (Heat of fusion, melting point) The heat of fusion of the highly crystalline phosphorus pentasulfide compositions obtained in the Examples and the phosphorus pentasulfide compositions obtained in the Comparative Examples 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.

[0116] (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. In this case, the chemical shift of P2S5 was set to 40 to 52 ppm, that of P4S9 to 52 to 70 ppm, that of P4S7 to 80 to 90 ppm, 90 to 100 ppm, and 110 to 115 ppm, and that of P4S3 to 80 to 90 ppm and 90 to 100 ppm. 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.

[0117] (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 of the phosphorus pentasulfide compositions at 50% cumulative frequency on a volume-based cumulative frequency distribution curve was 50 asked for.

[0118] (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. Lithium ion conductivity was measured using a potentiostat / galvanostat SP-300 manufactured by Biologic Corp. The sample size was 9.5 mm in diameter and 1.2 to 2.0 mm in thickness, and 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 a Li foil electrode. Here, as the sample for measuring lithium ion conductivity, a sulfide-based inorganic solid electrolyte material was prepared by the above procedure using the high-crystallinity diphosphorus pentasulfide compositions obtained in the examples and the diphosphorus pentasulfide compositions obtained in the comparative examples, and 150 mg of the resulting powder was pressed using a press at 270 MPa for 10 minutes to obtain a plate-shaped sulfide-based inorganic solid electrolyte material having a diameter of 9.5 mm and a thickness of 1.2 to 2.0 mm.

[0119] (Measurement of maximum oxidative decomposition current) Using the high-crystallinity phosphorus pentasulfide compositions obtained in the Examples and the Comparative Examples, sulfide-based inorganic solid electrolyte materials were prepared according to the procedure described above. Using a press, 120 to 150 mg of the resulting 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. Next, a Li foil was pressed onto one side of the resulting pellet as a reference electrode and counter electrode at 18 MPa for 10 minutes, and a SUS314 foil was attached to the other side as a working electrode. 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 to 5 V, and a voltage sweep rate of 5 mV / sec.

[0120] (recovery rate) The recovery rate was calculated from the following formula (1) using the mass of the high-crystallinity diphosphorus pentasulfide composition obtained in the example and the diphosphorus pentasulfide composition obtained in the comparative example, and the mass of the raw material diphosphorus pentasulfide composition. Recovery rate (%) = (M A / M B )×100 (1) M A : Mass (g) of highly crystalline phosphorus pentasulfide composition M B : Mass (g) of raw material diphosphorus pentasulfide composition

[0121] [Table 1]

[0122] The diphosphorus pentasulfide compositions of the examples achieved both high recovery rates and high lithium ion conductivity, and were useful for producing sulfide-based inorganic solid electrolyte materials. 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]

[0123] 100 Lithium-ion batteries 101 Cathode active material layer 103 Negative electrode active material layer 105 Current collector 110 Positive electrode 120 Electrolyte layer 130 negative electrode

Claims

1. 1. A diphosphorus pentasulfide composition comprising: The crystallinity calculated from a spectrum obtained by X-ray diffraction using CuKα radiation as a radiation source is 40% or more and 80% or less, an endothermic peak is observed in a temperature range of 280°C or higher and 300°C or lower in a DSC curve of the diphosphorus pentasulfide composition measured using a differential scanning calorimeter under 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 / min; A diphosphorus pentasulfide composition, wherein the heat of fusion of the endothermic peak is 60 J / g or more and 100 J / g or less.

2. 2. The diphosphorus pentasulfide composition of claim 1, The diphosphorus pentasulfide composition has a diphosphorus pentasulfide content of 70 mass% or more.

3. 3. The diphosphorus pentasulfide composition according to claim 1 or 2, A phosphorus pentasulfide composition in powder form.

4. The diphosphorus pentasulfide composition according to any one of claims 1 to 3, The median diameter d when the cumulative frequency is 50% in the volume-based cumulative frequency distribution curve measured using a laser diffraction / scattering particle size distribution analyzer ５０ A diphosphorus pentasulfide composition having a particle size of 1 μm or more and 150 μm or less.

5. A raw material composition for a sulfide-based inorganic solid electrolyte material, comprising the diphosphorus pentasulfide composition according to any one of claims 1 to 4 and lithium sulfide.

6. A method for producing a sulfide-based inorganic solid electrolyte material, comprising a step of mechanically treating the raw material composition for the sulfide-based inorganic solid electrolyte material according to claim 5.

Images