Sulfide-based inorganic solid electrolyte material, method for manufacturing sulfide-based inorganic solid electrolyte material, solid electrolyte, solid electrolyte membrane, and all-solid-state lithium-ion battery

Abstract

This invention provides a novel phosphorus pentasulfide composition useful for the production of sulfide-based inorganic solid electrolyte materials. [Solution] The phosphorus pentasulfide composition of this embodiment has a crystallinity of 40% or more and 80% or less calculated from the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source. In the DSC curve of the phosphorus 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 heating rate of 5°C / min, and an argon flow rate of 100 ml / min, an endothermic peak is observed in the temperature range of 280°C to 300°C, and the heat of fusion of the endothermic peak is 60 J / g or more and 100 J / g or less.

Description

[Technical Field]

[0001] The present invention relates to a phosphorus 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 laptop computers. Recently, however, lithium-ion batteries are also beginning to be used as power sources for electric vehicles and energy storage, 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 replace the electrolyte with a solid electrolyte, making the battery entirely solid (hereinafter also called all-solid-state lithium-ion batteries), do not use flammable organic solvents inside the battery. This allows for simplification of safety devices and is considered to offer advantages in terms of manufacturing costs and productivity.

[0004] As solid electrolyte materials used in such solid electrolytes, sulfide-based inorganic solid electrolyte materials are known, for example. It is known that sulfide-based inorganic solid electrolyte materials can be obtained by treating a phosphorus pentasulfide composition, which mainly contains phosphorus pentasulfide (P2S5), with a material such as lithium sulfide.

[0005] Patent Document 1 (Japanese Patent Publication No. 2020-61304) describes a phosphorus pentasulfide composition having a crystallinity of 30% or more, calculated from a spectrum obtained by X-ray diffraction measurement using CuKα rays. Furthermore, the phosphorus pentasulfide composition having a crystallinity of 30% or more contains low-boiling point phosphorus sulfide compounds (P4S3, P6S5O) in the phosphorus pentasulfide composition. 10 It is stated that this can be obtained by reducing the amount of (etc.) and by vacuum heating or other methods to improve crystallinity. [Prior art documents]

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Although sulfide-based inorganic solid electrolyte materials are excellent in electrochemical stability and lithium ion conductivity, their lithium ion conductivity is inferior to that of electrolytic solutions. From the above, there is a demand for further performance improvement of sulfide-based inorganic solid electrolyte materials used in lithium ion batteries, and there is also a demand for a phosphorus pentasulfide composition useful for the production of sulfide-based inorganic solid electrolyte materials.

[0008] The present invention has been made in view of such circumstances, and an object thereof is to provide a novel phosphorus pentasulfide composition useful for the production of sulfide-based inorganic solid electrolyte materials.

Means for Solving the Problems

[0009] The present inventors have intensively studied to provide a phosphorus pentasulfide composition useful for the production of sulfide-based inorganic solid electrolyte materials. As a result, the present inventors focused on the crystallinity and the heat of fusion, and arrived at the present invention.

[0010] That is, according to the present invention, a phosphorus pentasulfide composition, the crystallinity calculated from the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source is 40% or more and 80% or less, a phosphorus pentasulfide composition is provided, wherein the heat of fusion measured using a differential scanning calorimeter under the conditions of an initial temperature of 25°C, a measurement temperature range of 30 to 350°C, a heating rate of 5°C / min, and an atmosphere of 100 ml / min of argon is 60 J / g or more and 100 J / g or less.

[0011] Furthermore, according to the present invention, A raw material composition for a sulfide-based inorganic solid electrolyte material is provided, comprising the above-mentioned phosphorus pentasulfide composition and lithium sulfide.

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

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

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

[0015] Furthermore, according to the present invention, A solid electrolyte membrane containing the above-mentioned solid electrolyte as its main component is provided.

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

[0017] According to the present invention, a novel phosphorus pentasulfide composition useful for the production of sulfide-based inorganic solid electrolyte materials can be provided. [Brief explanation of the drawing]

[0018] [Figure 1] This 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]This figure shows the X-ray diffraction spectra of the phosphorus pentasulfide compositions obtained in the examples and comparative examples. [Figure 3] This figure shows an X-ray diffraction spectrum illustrating a method (peak separation method) for calculating the degree of crystallinity of a phosphorus pentasulfide composition according to an embodiment of the present invention. [Figure 4] This diagram illustrates the baseline used when calculating the heat quantity of the endothermic peak. [Figure 5] This figure shows the high-temperature DSC curves of the phosphorus pentasulfide compositions obtained in the examples and comparative examples. [Figure 6] This figure shows the low-temperature DSC curves of the phosphorus pentasulfide compositions obtained in the examples and comparative examples. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted as appropriate. Also, the figures are schematic diagrams and do not correspond to the actual dimensional ratios. Unless otherwise specified, the numerical range "A~B" represents A or greater and B or less.

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

[0021] In order to obtain the phosphorus pentasulfide composition according to this embodiment having the above-mentioned degree of crystallinity and heat of fusion, (i) Heating temperature of the raw material phosphorus pentasulfide composition (ii) Heating time of the raw material phosphorus pentasulfide composition (iii) Atmosphere during the heating process of the raw material phosphorus pentasulfide composition It is preferable to appropriately select the above three points. The preferred heating temperature, heating time, and atmosphere during the heating process will be described later in the section on [Method for producing phosphorus pentasulfide composition], but (i) is preferably 130°C or higher and below the melting point of the raw material phosphorus pentasulfide composition, (ii) is preferably 0.5 hours or more and 24 hours or less, and (iii) is preferably under an inert gas atmosphere.

[0022] The phosphorus pentasulfide composition according to this embodiment has a crystallinity of 40% or more and 80% or less, calculated from the spectrum obtained by X-ray diffraction using CuKα rays 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. Furthermore, the upper limit of the degree of crystallinity is 80% or less, preferably 76% or less, more preferably 73% or less, and particularly preferably 70% or less.

[0023] The phosphorus pentasulfide composition according to this embodiment has a crystallinity equal to or greater than the above lower limit, which improves the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material. The reason for this is not entirely clear, but it is thought that the phosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling point phosphorus sulfide compounds (P4S3, P4S7, etc.). The degree of crystallinity calculated from the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source is thought to represent an indicator of the amount of low-boiling point phosphorus sulfide compounds (P4S3, P4S7, etc.) in the phosphorus pentasulfide composition. A higher degree of crystallinity suggests that the low-boiling point phosphorus sulfide compounds (P4S3, P4S7, etc.) have crystallized into phosphorus pentasulfide. In other words, 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 smaller the amount of low-boiling point phosphorus sulfide compounds (P4S3, P4S7, etc.). For the reasons stated above, the phosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling-point phosphorus sulfide compounds. Therefore, using the phosphorus pentasulfide composition according to this embodiment can improve the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material. For this reason, it is considered useful in the production of sulfide-based inorganic solid electrolyte materials.

[0024] Furthermore, the phosphorus pentasulfide composition according to this embodiment has a crystallinity below the above upper limit, which allows for a more favorable recovery rate of the phosphorus pentasulfide composition while maintaining the lithium ion conductivity. Although the reason for this is not entirely clear, it is thought that excessively increasing the degree of crystallinity through processing causes not only low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.) but also the target phosphorus pentasulfide to evaporate, thus reducing the recovery rate. Therefore, by setting the upper limit of the degree of crystallinity of the phosphorus pentasulfide composition according to this embodiment to be below the above upper limit, 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 phosphorus pentasulfide composition can be achieved. Thus, the phosphorus pentasulfide composition according to this embodiment is considered useful for the manufacture of sulfide-based inorganic solid electrolyte materials.

[0025] Here, the method for calculating the degree of crystallinity of the phosphorus pentasulfide composition described above will be explained with reference to Figure 4. Figure 4 is a diagram showing the X-ray diffraction spectrum for illustrating the method (peak separation method) for calculating the degree of crystallinity of the phosphorus pentasulfide composition according to this embodiment. First, in X-ray diffraction using CuKα rays as the source, the diffraction curve corresponding to crystalline material becomes a sharp peak, while the diffraction curve corresponding to amorphous material becomes a broad halo due to scattering. Therefore, the proportion of crystalline material to the total of crystalline and amorphous material can be calculated as the degree of crystallinity. In this embodiment, a peak separation method is used to calculate the degree of crystallinity. Without considering the effects of incoherent scattering or lattice disorder, the X-ray diffraction pattern (also called the scattering curve) is separated into crystalline diffraction curves and amorphous halos using a profile fitting technique. Analysis software attached to the X-ray diffractometer can be used for profile fitting. The specific procedure for calculating the degree of crystallinity is as follows (see Figure 4; quoted from 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 beneath this line is defined as the background. (2) Separation of the halo The halo pattern due to amorphous materials is estimated, and the halo is separated from the scattering curve after subtracting the background. (3) Separation of crystalline diffraction curves The crystalline diffraction curves are separated using the same method as in (2) above. (4) Calculation of crystallinity The degree of crystallinity is calculated using the area under the curves (integral intensity) of the diffraction curves of the amorphous component (amorphous halo) and the crystalline component (crystalline diffraction curve), which are separated from the scattering curve, from the following equation (1). Xc = {Ic / (Ic+Ia)} × 100 (1) Ic: Area under the curve (integral intensity) of the diffraction curve of the crystalline component (crystalline diffraction curve) Ia: Area under the diffraction curve of the amorphous component (amorphous halo) (integral intensity) Furthermore, if 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 DSC curve of the phosphorus pentasulfide composition according to this embodiment, obtained by measurement using a differential scanning calorimeter, an endothermic peak is observed in the temperature range of 280°C to 300°C, and the heat of fusion of the endothermic peak is 60 J / g to 100 J / g, but the lower limit of the heat of fusion of the endothermic peak is preferably 62 J / g or more, and more preferably 65 J / g or more. Furthermore, the upper limit of the heat of fusion amount for 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 between 280°C and 300°C is the melting point of phosphorus pentasulfide (P2S5).

[0027] In this embodiment, the phosphorus pentasulfide composition exhibits an endothermic peak in the temperature range of 280°C to 300°C in the DSC curve, and the amount of heat of fusion at the endothermic peak is greater than or equal to the lower limit, thereby improving the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material. The reason for this is not entirely clear, but it is thought that the phosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling point phosphorus sulfide compounds (P4S3, P4S7, etc.). The heat of fusion of the endothermic peak measured by the above method is considered to represent an indicator of the amount of low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.) in the phosphorus pentasulfide composition. A higher degree of crystallinity suggests that the low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.) have crystallized into phosphorus pentasulfide. In other words, 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 smaller the amount of low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.). For the reasons stated above, the phosphorus pentasulfide composition according to this embodiment contains a small amount of low-boiling-point phosphorus sulfide compounds. Therefore, using the phosphorus pentasulfide composition according to this embodiment can improve the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material. For this reason, it is considered useful in the production of sulfide-based inorganic solid electrolyte materials.

[0028] Furthermore, because the phosphorus pentasulfide composition according to this embodiment has a heat of fusion value below the above upper limit, the recovery rate of the phosphorus pentasulfide composition can be more favorably maintained while suitably maintaining the lithium ion conductivity. Although the reason for this is not entirely clear, it is thought that excessive crystallinity-increasing treatment causes not only low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.) but also the target phosphorus pentasulfide to evaporate, thus reducing the recovery rate. Therefore, by setting the upper limit of the degree of crystallinity of the phosphorus pentasulfide composition according to this embodiment to be below the above upper limit, 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 phosphorus pentasulfide composition can be achieved. Thus, the phosphorus pentasulfide composition according to this embodiment is considered useful for the manufacture of sulfide-based inorganic solid electrolyte materials.

[0029] The above DSC curve can be measured, for example, by the following method. First, weigh 20-25 mg of the phosphorus pentasulfide composition into an aluminum pan in an argon atmosphere, then cover with an aluminum lid and seal with a sample sealer. The reference aluminum container should be empty. Under the conditions of a starting temperature of 25°C, a measurement temperature range of 30-350°C, a heating rate of 5°C / min, and an argon atmosphere of 100 ml / min, differential scanning calorimetry is performed using a differential scanning calorimetry meter. The differential scanning calorimetry meter is not particularly limited, but for example, the DSC6300 manufactured by Seiko Instruments Corporation can be used. Furthermore, if 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 resulting DSC curve, it is possible to observe the presence or absence of an endothermic peak in the temperature range between 280°C and 300°C. Here, the heat of fusion at the endothermic peak is calculated by determining the area enclosed by the endothermic fusion curve containing the endothermic peak and the baseline. Since the intrinsic heat capacity of a material differs before and after the thermal change, the baselines before and after the endothermic peak are not straight lines. 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 of a line parallel to the Y-axis, passing through point P, the intersection of the baseline before the endothermic peak and the tangent to the endothermic peak, and the melting endothermic curve. Point S is the intersection of a line parallel to the Y-axis, passing through point Q, the intersection of the baseline after the endothermic peak and the tangent to the endothermic peak, and the melting endothermic curve. Furthermore, in the phosphorus pentasulfide composition according to this embodiment, there is usually only one endothermic peak observed in the temperature range of 280°C to 300°C.

[0030] The phosphorus pentasulfide composition according to this embodiment can further improve the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material. Therefore, it is preferable that no exothermic peak is observed in the DSC curve in the temperature range of at least 120°C to 140°C, and more preferably that no exothermic peak is observed in the DSC curve in the temperature range of at least 30°C to 280°C. In this embodiment, the absence of a peak in the DSC curve means that no peak is observed with a heat energy of 0.3 J / g or more, preferably 0.1 J / g or more. Furthermore, in this embodiment, the heat quantity of the exothermic peak and the baseline at the exothermic peak can be defined in the same manner as the heat quantity of the endothermic peak and the baseline at the endothermic peak described above.

[0031] The phosphorus pentasulfide composition according to this embodiment contains phosphorus pentasulfide (P2S5) as the main component. In addition to phosphorus pentasulfide (P2S5), other components included in the phosphorus pentasulfide composition according to this embodiment include P4S9, P4S7, and P4S3. In this case, the lower limit of the phosphorus pentasulfide content in the phosphorus 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 having a lower limit of phosphorus pentasulfide content 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 phosphorus pentasulfide content in the phosphorus pentasulfide composition according to this embodiment is not particularly limited, but for example, it is 100% by mass or less. The amount of phosphorus pentasulfide contained in the phosphorus pentasulfide composition is, for example, in solid form. 31 It can be calculated using P-NMR spectroscopy.

[0032] solid 31 P-NMR spectra can be measured, for example, by the following method. First, the test sample is filled into a 3.2 mm diameter measuring sample 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: JNM-ECA-600 manufactured by JEOL RESONANCE Co., Ltd. Observation frequency: 242.95MHz Pulse width: 90° pulse Pulse waiting time: 2800 seconds Total number of times: 64 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, see Reference 1 "Hellmut Eckert, Cheryl S. Liang and Galen D. Stucky: 31P magic angle spinning NMR of crystalline phosphorous sulfides. Correlation of 31 Referring to "P chemical shielding tensors with local environments, J. Phys. Chem, 1989, 93, 452–457," waveform separation using a Gaussian function was performed based on the peak assignments described below, and the integral value of each peak was calculated. The integral value of the peak originating from each component is proportional to the number of moles of phosphorus contained. Therefore, the content ratio can be calculated from the obtained integral values ​​and the molecular weight of each component. The chemical shifts for P2S5 are 40-52 ppm, P4S9 are 52-70 ppm, P4S7 are 80-90 ppm, 90-100 ppm, and 110-115 ppm, and P4S3 are 80-90 ppm and 90-100 ppm.

[0033] In the phosphorus pentasulfide composition according to this embodiment, solid 31 When measuring the P-NMR spectrum, it is preferable that no peaks are observed in the range of 52 ppm to 70 ppm. In other words, it is preferable that no P4S9 peaks are observed. This allows for an increase in the proportion of phosphorus pentasulfide in the phosphorus pentasulfide composition, and further improves the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material.

[0034] In the phosphorus pentasulfide composition according to this embodiment, solid 31 When measuring the P-NMR spectrum, it is preferable that no peaks are observed in the range of 80 ppm to 90 ppm. In other words, it is preferable that the peaks of P4S7 and P4S3 are not observed. This allows for an increase in the proportion of phosphorus pentasulfide in the phosphorus pentasulfide composition, and further improves the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material.

[0035] As the property of the phosphorus pentasulfide composition according to this embodiment, it is preferably in a powder form. Since the production of the sulfide-based inorganic solid electrolyte material described later is generally carried out dry, if the property of 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 phosphorus pentasulfide composition according to this embodiment has a median diameter d when the cumulative frequency is 50% in the volume-based cumulative frequency distribution curve measured using a laser diffraction scattering type particle size distribution measuring device. 50 is preferably 1 μm or more and 150 μm or less, more preferably 3 μm or more and 100 μm or less, and even more preferably 5 μm or more and 75 μm or less. The median diameter d of the phosphorus pentasulfide composition. 50 By setting the median diameter d within the above range, the handling property during the production of the sulfide-based inorganic solid electrolyte material is improved, the reaction efficiency during the production of the sulfide-based inorganic solid electrolyte material is enhanced, and the production efficiency of the sulfide-based inorganic solid electrolyte material can be improved.

[0037] [Manufacturing method of phosphorus pentasulfide composition] Next, the manufacturing method of the phosphorus pentasulfide composition according to this embodiment will be described. The manufacturing method of the phosphorus pentasulfide composition according to this embodiment is different from the conventional manufacturing method of the phosphorus pentasulfide composition. That is, the highly crystallized phosphorus pentasulfide composition according to this embodiment can be obtained for the first time by adopting a manufacturing technique such as a process of reducing the amount of low-boiling phosphorus sulfide compounds (P4S3, P4S7, etc.) in the raw material phosphorus pentasulfide composition by performing a heat treatment on the raw material phosphorus pentasulfide composition. However, the manufacturing method of the phosphorus pentasulfide composition according to this embodiment can adopt various specific manufacturing conditions on the premise of adopting the above manufacturing technique.

[0038] The method for producing the phosphorus pentasulfide composition according to this embodiment includes a heating step of heat-treating the raw material phosphorus pentasulfide composition at a temperature of 130°C or higher and below the melting point of the raw material phosphorus pentasulfide composition, thereby obtaining a highly crystallinity phosphorus pentasulfide composition with a higher degree of crystallinity than the raw material phosphorus pentasulfide composition. The method for producing the phosphorus pentasulfide composition according to this embodiment employs the above configuration, which involves heating the raw material phosphorus pentasulfide composition to a temperature below its melting point. This minimizes the evaporation of phosphorus pentasulfide contained in the phosphorus pentasulfide composition, and effectively removes only low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.).

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

[0040] (Heating process) In the method for producing the phosphorus pentasulfide composition according to this embodiment, the amount of low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.) in the raw material phosphorus pentasulfide composition is reduced by heat treatment, thereby improving the crystallinity of the raw material phosphorus pentasulfide composition. As a result, a high-crystallinity phosphorus pentasulfide composition with a higher degree of crystallinity than the raw material phosphorus pentasulfide composition according to this embodiment can be obtained. Here, when the raw material phosphorus pentasulfide composition is heated, the components that do not evaporate and accumulate at the bottom of the container are usually the high-crystallinity phosphorus pentasulfide composition according to this embodiment.

[0041] Here, the lower limit of the heating temperature in the above 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 above the above lower limit, the crystallinity of the high-crystallinity phosphorus pentasulfide composition can be made more favorable. Furthermore, the upper limit of the heating temperature in the above heating process is preferably below the melting point of the raw material phosphorus pentasulfide composition, more preferably 250°C or lower, and even more preferably 220°C or lower. By setting the heating temperature to or below the above upper limit, the recovery rate of the highly crystallinity phosphorus pentasulfide composition can be more favorably improved. The melting point of the above-mentioned phosphorus pentasulfide composition can be determined by the DSC curve described later.

[0042] The method for producing the phosphorus pentasulfide composition according to this embodiment involves heat-treating the raw material phosphorus pentasulfide composition within a temperature range above the lower limit and below the upper limit, thereby obtaining a phosphorus pentasulfide composition that achieves both high crystallinity and high recovery rate. Although the reason for this is not entirely clear, it is thought that in the method for producing the phosphorus pentasulfide composition according to this embodiment, the raw material phosphorus pentasulfide composition is heated to a temperature below its melting point to temporarily destabilize its structure, making it easier to change the glassy phosphorus pentasulfide into a more stable crystalline state, and that only low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.) are removed, thereby minimizing the evaporation of phosphorus pentasulfide. Currently, it is believed that the degree of crystallinity of a phosphorus pentasulfide composition calculated from X-ray diffraction spectra is closely related to the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material obtained from said phosphorus pentasulfide. Furthermore, it is believed that the higher the degree of crystallinity of the phosphorus pentasulfide composition calculated from X-ray diffraction spectra, the higher the crystallinity of the phosphorus pentasulfide and the smaller the amount of low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.). For this reason, vacuum heating treatments have been performed to remove low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.). 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 composition also evaporated, which is thought to have reduced the recovery rate. On the other hand, in the method for producing the phosphorus pentasulfide composition according to this embodiment, the raw material phosphorus pentasulfide composition is heated to a temperature below its melting point, thereby minimizing the evaporation of phosphorus pentasulfide contained in the phosphorus pentasulfide composition and effectively removing only low-boiling-point phosphorus sulfide compounds (P4S3, P4S7, etc.). For the reasons stated above, since the method for producing the phosphorus pentasulfide composition according to this embodiment effectively removes low-boiling-point phosphorus sulfide compounds, it is considered that using the method for producing the phosphorus pentasulfide composition according to this embodiment can achieve both high crystallinity and high recovery rate.

[0043] In the method for producing the 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 having the recovery rate equal to or greater than the lower limit, the production efficiency of the high-crystallinity phosphorus pentasulfide composition can be improved. Furthermore, 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 below the upper limit, the amount of low-boiling point phosphorus sulfide compounds (P4S3, P4S7, etc.) in the raw material phosphorus pentasulfide composition can be reduced. The recovery rate refers to the ratio of the mass of the high-crystallinity phosphorus pentasulfide composition after heating to the mass of the raw material phosphorus pentasulfide composition, and can be calculated using the following formula (1). Recovery rate (%) = (M A / M B ) × 100 (1) M A : Mass (g) of the highly crystallinity phosphorus pentasulfide composition M B : Mass (g) of the raw material phosphorus pentasulfide composition

[0044] In the method for producing the phosphorus pentasulfide composition according to this embodiment, the lower limit of the heating time for the raw material phosphorus 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 heating for a time equal to or greater than the lower limit, the crystallinity of the high-crystallinity phosphorus pentasulfide composition can be made more favorable. Furthermore, 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 below the upper limit, the recovery rate of the highly crystallinity phosphorus pentasulfide composition can be more favorably improved.

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

[0046] In the method for producing the phosphorus 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 the above configuration, it is possible to prevent reactions with various components or moisture in the air, and to prevent the generation of impurities in the phosphorus pentasulfide composition. In particular, carrying out the heating step under an inert gas atmosphere is preferable 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 process described above include argon gas, helium gas, and nitrogen gas. Among these, argon gas is particularly preferred. These inert gases are preferably of high purity to prevent contamination of 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 of introducing the inert gas into the mixing system is not particularly limited as long as the mixing system is filled with an inert gas atmosphere, but examples include purging the inert gas and 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 using a raw material composition for a sulfide-based inorganic solid electrolyte material that includes the phosphorus 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 the raw material composition for a sulfide-based inorganic solid electrolyte material that includes the phosphorus pentasulfide composition according to this embodiment and lithium sulfide.

[0049] In this embodiment, the sulfide-based inorganic solid electrolyte material preferably contains Li, P, and S as constituent elements, from the viewpoint of further improving electrochemical stability, stability in moisture and air, and handling ease. Furthermore, in order to further improve lithium ion conductivity, electrochemical stability, stability in moisture and air, and handling properties, the sulfide-based inorganic solid electrolyte material according to this embodiment has a molar ratio Li / P of the content of Li to the content of P in the sulfide-based inorganic solid electrolyte material which is preferably 1.0 to 5.0, more preferably 2.0 to 4.0, even more preferably 2.5 to 3.8, even more preferably 2.8 to 3.6, even more preferably 3.0 to 3.5, even more preferably 3.1 to 3.4, and particularly preferably 3.1 to 3.3. The molar ratio S / P of the content of S to the content of P is preferably 2.0 to 6.0, more preferably 3.0 to 5.0, even more preferably 3.5 to 4.5, even more preferably 3.8 to 4.2, even more preferably 3.9 to 4.1, and particularly preferably 4.0. Here, the content of Li, P, and S in the sulfide-based inorganic solid electrolyte material according to this embodiment can be determined, for example, by 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 AC impedance under measurement conditions of 27.0°C, applied voltage of 10mV, and measurement frequency range of 0.1Hz to 7MHz is preferably 1.0 × 10⁻¹⁰. -3 S·cm -1 The above is a comfortable 1.1 × 10 -3 S·cm -1 More preferably 1.3 × 10 -3 S·cm -1 In particular, 1.5 × 10 -3 S·cm -1 That's all. If the lithium-ion conductivity of the sulfide-based inorganic solid electrolyte material according to this embodiment is above the above lower limit, a lithium-ion battery with even better battery characteristics can be obtained. Furthermore, using such a sulfide-based inorganic solid electrolyte material can yield a lithium-ion battery with even better input / output characteristics. 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 for example, 3.0 × 10 -3 S·cm -1 The following is true: 2.8 × 10 -3 S·cm -1 The following is true: 2.5 × 10 -3 S·cm -1 The following applies:

[0051] Examples of the shape of the sulfide-based inorganic solid electrolyte material according to this embodiment include particulate form. The particulate sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited, but 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 However, it is preferably 1 μm to 100 μm, more preferably 3 μm to 80 μm, and even more preferably 5 μm to 60 μm. Median diameter d of sulfide-based inorganic solid electrolyte materials 50By keeping the above range, good handling performance can be maintained while further improving lithium-ion conductivity.

[0052] The sulfide-based inorganic solid electrolyte material according to this embodiment preferably exhibits excellent electrochemical stability. Here, electrochemical stability refers, for example, to 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 the conditions of a temperature of 25°C, a sweep voltage range of 0 to 5V, and a voltage sweep rate of 5mV / second is preferably 0.50μA or less, more preferably 0.20μA or less, even more preferably 0.10μA or less, even more preferably 0.05μA or less, and particularly preferably 0.03μA or less. It is preferable that the maximum value of the oxidative decomposition current of the sulfide-based inorganic solid electrolyte material is less than or equal to the above upper limit, because this can 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 sulfide-based inorganic solid electrolyte materials is not particularly limited, but for example, it is 0.0001 μA or higher.

[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., in lithium-ion batteries. Furthermore, the sulfide-based inorganic solid electrolyte material according to this embodiment is suitably 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 suitably 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 the positive electrode, the solid electrolyte layer, and the negative electrode are stacked in this order.

[0054] [Method for producing sulfide-based inorganic solid electrolyte materials] Next, a method for producing a 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 a step of mechanically treating a raw material composition for the sulfide-based inorganic solid electrolyte material, which includes, for example, the phosphorus 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 manufacturing method including the following steps (A) and (B). The manufacturing method for the sulfide-based inorganic solid electrolyte material according to this embodiment may further include the following steps (C) and (D) as needed. Step (A): A step of preparing a raw material composition for a sulfide-based inorganic solid electrolyte material, which includes the phosphorus pentasulfide composition according to this embodiment and lithium sulfide. Step (B): A step in which the raw material composition of a sulfide-based inorganic solid electrolyte material is mechanically treated to vitrify the raw materials, phosphorus pentasulfide composition and lithium sulfide, while chemically reacting them, thereby obtaining a sulfide-based inorganic solid electrolyte material in a glassy state. Step (C) A step of heating the obtained glassy sulfide-based inorganic solid electrolyte material to crystallize at least a portion of it. Step (D): A step of crushing, classifying, or granulating the obtained sulfide-based inorganic solid electrolyte material.

[0055] (Step (A) of preparing the raw material composition for sulfide-based inorganic solid electrolyte material) First, a raw material composition for a sulfide-based inorganic solid electrolyte material is prepared, which includes the phosphorus pentasulfide composition according to this embodiment, lithium sulfide, and optionally lithium nitride. Here, 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 the desired composition ratio. The method of mixing the raw materials is not particularly limited as long as it is a method that can uniformly mix the raw materials, but for example, mixing can be done using a ball mill, bead mill, vibratory mill, impact grinding device, mixer (pug mixer, ribbon mixer, tumbler mixer, drum mixer, V-type mixer, etc.), kneader, twin-screw kneader, air jet grinder, crusher, rotary blade grinder, etc. The mixing conditions, such as the stirring speed, processing time, temperature, reaction pressure, and gravitational acceleration applied to the mixture, can be appropriately determined depending on the volume of the mixture being processed.

[0056] The lithium sulfide used as a raw material is not particularly limited; commercially available lithium sulfide may be used, or lithium sulfide obtained by the reaction of lithium hydroxide and hydrogen sulfide may be used, for example. From the viewpoint of obtaining a high-purity sulfide-based inorganic solid electrolyte material and suppressing side reactions, it is preferable to use lithium sulfide with few impurities. In this embodiment, lithium sulfide also includes polysulfide.

[0057] Lithium nitride may be used as a raw material. Here, since the nitrogen in lithium nitride is discharged into the system as N2, by using lithium nitride as the inorganic compound raw material, 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 used in this embodiment is not particularly limited, and commercially available lithium nitride (e.g., Li3N, etc.) may be used, or lithium nitride obtained by the reaction of metallic lithium (e.g., Li foil) with nitrogen gas may be used. 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) to obtain a sulfide-based inorganic solid electrolyte material in a glassy state) Next, the raw material composition for the sulfide-based inorganic solid electrolyte material is mechanically treated to vitrify the raw materials, phosphorus pentasulfide composition and lithium sulfide, through a chemical reaction, thereby obtaining a sulfide-based inorganic solid electrolyte material in a glassy state.

[0059] Here, mechanical treatment refers to a method that can vitrify a material while causing a chemical reaction by mechanically colliding two or more inorganic compounds, such as mechanochemical treatment. Mechanochemical treatment is a method of vitrifying a target composition while applying mechanical energy such as shear force or impact force. Furthermore, in process (B), the mechanochemical treatment is preferably a dry mechanochemical treatment, from the viewpoint of easily achieving an environment in which moisture and oxygen are removed at a high level. By using mechanochemical processing, each raw material can be mixed while being pulverized into fine particles, thereby increasing the contact area between each raw material. This promotes the reaction of each raw material, and thus the sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained more efficiently.

[0060] Here, mechanochemical treatment is a method of vitrification in which mechanical energy such as shear force, impact force, or centrifugal force is applied to the material to be mixed. Examples of equipment for performing vitrification by mechanochemical treatment (hereinafter referred to as vitrification equipment) include crushing and dispersing machines such as ball mills, bead mills, vibratory mills, turbo mills, mechanofusions, disc mills, and roll mills; rotary and impact crushing devices consisting of a mechanism that combines rotation (shear stress) and impact (compressive stress), such as rock drills, rotary 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, and ball mills are particularly preferred, from the viewpoint of being able to efficiently generate very high impact energy. Furthermore, from the standpoint of excellent continuous productivity, roll mills; rotary and impact grinding devices consisting of a mechanism that combines rotation (shear stress) and impact (compressive stress), such as rock drills, rotary hammers, and impact drivers; high-pressure gliding rolls; and vertical mills such as roller-type vertical mills and ball-type vertical mills are preferred.

[0061] The mixing conditions, such as rotation speed, processing time, temperature, reaction pressure, and gravitational acceleration applied to the raw material inorganic electrolyte composition during mechanical processing, can be appropriately determined depending on the type and amount of the raw material inorganic composition. Generally, the faster the rotation speed, the faster the glass formation rate, and the longer the processing time, the higher the conversion rate to glass. Normally, when X-ray diffraction analysis is performed using CuKα rays as the radiation source, if the diffraction peak originating from the raw materials disappears or decreases, 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] Here, in step (B), the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material is preferably 1.0 × 10⁻¹⁰ -4 S·cm -1 The above is more 2.0 × 10-4 S·cm- 1 More preferably 3.0 × 10 -4 S·cm -1 It is preferable to perform the vitrification treatment until the above is achieved. This makes it possible to obtain a sulfide-based inorganic solid electrolyte material with even better lithium ion conductivity.

[0063] (Step (C) of crystallizing at least a portion of the sulfide-based inorganic solid electrolyte material) Next, the obtained glassy sulfide-based inorganic solid electrolyte material is heated to crystallize at least a portion of it, thereby producing a glass-ceramic sulfide-based inorganic solid electrolyte material (also called crystallized glass). This process makes it possible to obtain a sulfide-based inorganic solid electrolyte material with even better lithium-ion conductivity. In other words, 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 glassy sulfide-based inorganic solid electrolyte material is heated is preferably in the range of 220°C to 500°C, and more preferably in the range of 250°C to 350°C. The heating time for the glassy sulfide-based inorganic solid electrolyte material is not particularly limited as long as it is sufficient to obtain the desired glass-ceramic sulfide-based inorganic solid electrolyte material, but is, for example, within the range of 0.5 hours to 24 hours, and preferably 1 hour to 3 hours. The heating method is not particularly limited, but for example, a method using a firing furnace can be cited. The temperature, time, and other conditions during such heating can be appropriately adjusted to optimize the properties of the sulfide-based inorganic solid electrolyte material according to this embodiment.

[0065] Furthermore, heating of the glassy sulfide-based inorganic solid electrolyte material is preferably carried out under an inert gas atmosphere, for example. This prevents deterioration (e.g., oxidation) of the sulfide-based inorganic solid electrolyte material. Examples of inert gases used when heating glassy sulfide-based inorganic solid electrolyte materials include argon gas, helium gas, and nitrogen gas. These inert gases are preferably of high purity to prevent contamination of 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 of introducing the inert gas into the mixing system is not particularly limited as long as the mixing system is filled with an inert gas atmosphere, but examples include purging the inert gas and continuously introducing a constant amount of inert gas.

[0066] (Process of crushing, classifying, or granulating (D)) 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 be further subjected to steps of pulverization, classification, or granulation, if necessary. For example, by pulverizing to produce fine particles and then adjusting the median diameter by classification or granulation, a sulfide-based inorganic solid electrolyte material having a desired median diameter can be obtained. The pulverization method is not particularly limited, and known pulverization methods such as mixers, air jet milling, mortars, rotary mills, and coffee mills can be used. Similarly, the classification method is not particularly limited, and known methods such as sieving can be used. These grinding or classification processes are preferably carried out under an inert gas atmosphere or a vacuum atmosphere, as this prevents contact with moisture in the air.

[0067] 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 method described above, 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. Furthermore, the solid electrolyte according to this embodiment is not particularly limited, but as a component other than the sulfide-based inorganic solid electrolyte material according to this embodiment, it may include, for example, a different type of solid electrolyte material from the sulfide-based inorganic solid electrolyte material according to this embodiment, as long as it does not impair the objectives of the present invention.

[0069] The solid electrolyte according to this embodiment may include a solid electrolyte material of a different type from the sulfide-based inorganic solid electrolyte material according to this embodiment described above. 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 ionic conductivity and insulating properties, but those commonly used in lithium-ion batteries can be used. For example, examples 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 materials according to this embodiment described above include Li2S-P2S5 material, Li2S-SiS2 material, Li2S-GeS2 material, Li2S-Al2S3 material, Li2S-SiS2-Li3PO4 material, Li2S-P2S5-GeS2 material, Li2S-Li2O-P2S5-SiS2 material, Li2S-GeS2-P2S5-SiS2 material, Li2S-SnS2-P2S5-SiS2 material, Li2S-P2S5-Li3N material, and Li2S 2+X Examples include P4S3 materials and Li2S-P2S5-P4S3 materials. These may be used individually or in combination of two or more types. Among these, the Li2S-P2S5 material is preferred because it has excellent lithium ion conductivity and stability that does not cause decomposition or the like in a wide voltage range. Here, for example, the Li2S-P2S5 material means a solid electrolyte material obtained by chemically reacting at least Li2S (lithium sulfide) and P2S5 in an inorganic composition with each other by mechanical treatment. 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, and LiGe2(PO4)3, perovskite types such as (La 0.5+x Li 0.5-3x )TiO3, Li2O-P2O5 materials, Li2O-P2O5-Li3N materials, and the like. Examples of other lithium-based inorganic solid electrolyte materials include LiPON, LiNbO3, LiTaO3, Li3PO4, LiPO 4-x N x (where x is 0 < x ≤ 1), LiN, LiI, LISICON, and the like. Furthermore, glass ceramics obtained by precipitating crystals of these inorganic solid electrolytes can also be used as 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 includes 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 can be used, for example, in a solid electrolyte layer that constitutes 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 the positive electrode, the solid electrolyte layer, and the negative electrode are stacked in this order. In this case, the solid electrolyte layer is composed of a solid electrolyte membrane.

[0075] The average thickness of the solid electrolyte membrane according to this embodiment is preferably 5 μm to 500 μm, more preferably 10 μm to 200 μm, and even more preferably 20 μm to 100 μm. When the average thickness of the solid electrolyte membrane is above the lower limit, the loss of solid electrolyte and the occurrence of cracks on the surface of the solid electrolyte membrane can be further suppressed. Furthermore, when the average thickness of the solid electrolyte membrane is below the upper limit, the impedance of the solid electrolyte membrane can be further reduced. As a result, the battery characteristics of the resulting all-solid-state lithium-ion battery can be further improved.

[0076] The solid electrolyte membrane according to this embodiment is preferably a pressurized 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 anchoring effect between the solid electrolyte materials. By using a pressure-molded structure, bonding occurs between the solid electrolytes, further increasing the strength of the resulting solid electrolyte membrane. As a result, the loss of solid electrolytes and the occurrence of cracks on the surface of the solid electrolyte membrane can be further suppressed.

[0077] The content of the sulfide-based inorganic solid electrolyte material described above in the solid electrolyte membrane according to this 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 total solid electrolyte membrane is considered to be 100% by mass. This improves the 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 a solid electrolyte membrane with such 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 for example, it is 100% by mass or less.

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

[0079] Furthermore, the solid electrolyte membrane according to this embodiment may contain a binder resin, but the binder resin content is preferably less than 0.5% by mass, more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, and even more preferably 0.01% by mass or less, when the total mass of the solid electrolyte membrane is considered to be 100% by mass. Moreover, it is even more preferable that the solid electrolyte membrane according to this embodiment is substantially free of binder resin, and most preferably is free of binder resin. This improves the 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. 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. Furthermore, "substantially free of binder resin" means that it may contain binder resin to an extent that does not impair the effects of this embodiment. Also, when an adhesive resin layer is provided between the solid electrolyte layer and the positive or negative electrode, the adhesive resin originating from the adhesive resin layer that is present near the interface between the solid electrolyte layer and the adhesive resin layer is excluded from "binder resin in the solid electrolyte membrane".

[0080] The above-mentioned binder resin refers to a binder commonly used in lithium-ion batteries to bond inorganic solid electrolyte materials together. Examples include polyvinyl alcohol, polyacrylic acid, carboxymethylcellulose, 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 a film-like manner on the cavity surface of a mold or on the surface of a substrate, and then pressurizing the solid electrolyte deposited in a film-like manner. The method for pressurizing the solid electrolyte is not particularly limited. For example, if particulate solid electrolyte is deposited on the cavity surface of a mold, pressing with a mold and a press die can be used. If particulate solid electrolyte is deposited on the surface of a substrate, pressing with a mold and a press die, a roll press, a flat plate press, etc., can be used. The pressure applied to pressurize the solid electrolyte is, for example, between 10 MPa and 500 MPa.

[0082] Furthermore, if necessary, the inorganic solid electrolyte deposited in a film may be pressurized and heated. Heating and pressurizing will cause fusion and bonding between the solid electrolytes, further increasing the strength of the resulting solid electrolyte film. As a result, the loss of solid electrolytes and the occurrence of cracks on the surface of the solid electrolyte film can be further suppressed. The temperature at which the solid electrolyte is heated is, for example, between 40°C and 500°C.

[0083] [Lithium-ion battery] Figure 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 comprises, 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. Preferably, 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 containing the positive electrode active material is referred to as the positive electrode active material layer 101. The positive electrode 110 may optionally include a current collector 105 in addition to the positive electrode active material layer 101, or it may not include the current collector 105. In this embodiment, unless otherwise specified, the layer containing the negative electrode active material is referred to as the negative electrode active material layer 103. The negative electrode 130 may, if necessary, further include a current collector 105 in addition to the negative electrode active material layer 103, or it 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 cylindrical, coin-shaped, prismatic, film-shaped, or any other shape.

[0084] The lithium-ion battery 100 according to this embodiment is manufactured according to generally known methods. For example, the positive electrode 110, the electrolyte layer 120, and the negative electrode 130 are stacked and formed into a cylindrical, coin-shaped, prismatic, film-shaped, or any other arbitrary shape, and a non-aqueous electrolyte is sealed inside as needed.

[0085] (positive electrode) The positive electrode 110 is not particularly limited, and one commonly used in lithium-ion batteries can be used. The positive electrode 110 is not particularly limited, but can be manufactured according to generally known methods. For example, it 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 determined appropriately according to the intended use of the battery and are not particularly limited; they can be set in accordance with generally known information.

[0086] The positive electrode active material layer 101 contains the 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 (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxide (Li2MnO3-LiMO2 (M=Co, Ni, etc.)), lithium-manganese-nickel oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Composite oxides such as O2, olivine-type lithium phosphate oxide (LiFePO4); conductive polymers such as polyaniline and polypyrrole; sulfide-based positive electrode active materials such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, Li-VS compounds, and Li-Fe-S compounds; materials using sulfur as an active material, such as sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, and mixed powders of sulfur and carbon; etc. These positive electrode active materials may be used individually or in combination of two or more. Among these, sulfide-based cathode 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 chemically reacting inorganic compositions containing molybdenum sulfide and lithium sulfide, which are the raw materials, with each other through mechanical treatment. Furthermore, Li-Ti-S compounds contain Li, Ti, and S as constituent elements, and can usually be obtained by chemically reacting inorganic compositions containing titanium sulfide and lithium sulfide, which are the raw materials, with each other through mechanical processing. Li-VS compounds contain Li, V, and S as constituent elements and can usually be obtained by chemically reacting inorganic compositions containing vanadium sulfide and lithium sulfide, which are the raw materials, through mechanical treatment.

[0088] The positive electrode active material layer 101 is not particularly limited, but may include one or more materials selected from, for example, binder resins, thickeners, conductive additives, and solid electrolyte materials, as components other than the positive electrode active material. Each of these materials will be described below.

[0089] The positive electrode active material layer 101 may also contain a binder resin that serves to bond the positive electrode active materials together and to the current collector 105. The binder resin according to this embodiment is not particularly limited as long as it is a conventional binder resin that can be used in lithium-ion batteries, but examples include polyvinyl alcohol, polyacrylic acid, carboxymethylcellulose, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, and polyimide. These binders may be used individually or in combination of two or more.

[0090] The positive electrode active material layer 101 may contain a thickening agent to ensure the fluidity of the slurry suitable for coating. The thickening agent is not particularly limited as long as it is a conventional thickening agent usable in lithium-ion batteries, but examples include cellulosic polymers such as carboxymethylcellulose, methylcellulose, and hydroxypropylcellulose, and their ammonium salts and alkali metal salts, water-soluble polymers such as polycarboxylic acids, polyethylene oxide, polyvinylpyrrolidone, polyacrylates, and polyvinyl alcohol. These thickening agents may be used individually or in combination of two or more.

[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 conventional conductive additive that can be used in lithium-ion batteries, but examples include carbon black such as acetylene black and kechen black, and carbon materials such as vapor-processed carbon fibers.

[0092] The positive electrode according to this embodiment may contain a solid electrolyte comprising the sulfide-based inorganic solid electrolyte material according to this embodiment described above, or it may contain a solid electrolyte comprising a different type of solid electrolyte material than the sulfide-based inorganic solid electrolyte material according to this embodiment. The different type of solid electrolyte material according to this embodiment is not particularly limited as long as it has ionic conductivity and insulating properties, but those commonly used in lithium-ion batteries can be used. For example, inorganic solid electrolyte materials such as sulfide-based inorganic solid electrolyte materials, oxide-based inorganic solid electrolyte materials, and other lithium-based inorganic solid electrolyte materials; and organic solid electrolyte materials such as polymer electrolytes can be used. More specifically, the inorganic solid electrolyte materials mentioned in the description of the solid electrolyte according to this embodiment can be used.

[0093] The mixing ratio of the various materials in the positive electrode active material layer 101 is determined appropriately according to the intended use of the battery and is not particularly limited; it can be set in accordance with generally known information.

[0094] (Negative electrode) The negative electrode 130 is not particularly limited, and one commonly used in lithium-ion batteries can be used. The negative electrode 130 is not particularly limited, but can be manufactured according to generally known methods. For example, it can be obtained by forming a negative electrode active material layer 103 containing a negative electrode 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 determined appropriately according to the intended use of the battery and are not particularly limited; they can be set in accordance with generally known information.

[0095] The negative electrode active material layer 103 contains the negative electrode active material. The above-mentioned negative electrode active material is not particularly limited as long as it is a normal negative electrode active material that can be used as the negative electrode of a lithium-ion battery, but examples include carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; metallic 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 oxide (e.g., Li4Ti5O12). These negative electrode active materials may be used individually or in combination of two or more.

[0096] The negative electrode active material layer 103 is not particularly limited, but may include one or more materials selected from, for example, binder resins, thickeners, conductive additives, and solid electrolyte materials, as components other than the negative electrode active material. These materials are not particularly limited, but examples include those similar to the materials used for the positive electrode 110 described above. The mixing ratio of the various materials in the negative electrode active material layer 103 is determined appropriately according to the intended use of the battery and is not particularly limited; it can be set in accordance with generally known information.

[0097] (electrolyte layer) Next, the electrolyte layer 120 will be described. The electrolyte layer 120 is a layer formed between the positive electrode active material layer 101 and the negative electrode active material layer 103. The electrolyte layer 120 may be a separator impregnated with a non-aqueous electrolyte, 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 and the negative electrode 130 and has the function of permeating lithium ions, but for example, a porous film can be used.

[0099] Microporous polymer films are preferably used as porous membranes, and examples of materials include polyolefins, polyimides, polyvinylidene fluoride, and polyesters. In particular, porous polyolefin films are preferred, specifically porous polyethylene films and porous polypropylene films.

[0100] The non-aqueous electrolyte mentioned above is a solution in which an electrolyte is dissolved in a solvent. Any known lithium salt can be used as the electrolyte, and the appropriate one should be selected according to the type of active material. For example, LiClO4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 Examples include LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiCF3SO3, LiC4F9SO3, Li(CF3SO2)2N, and lithium lower fatty acid carboxylates.

[0101] The solvent used to dissolve the above electrolyte is not particularly limited as long as it is a liquid commonly used to dissolve electrolytes, and includes 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; and ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples 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; triglimes; sulfolanes such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; and sultones such as 1,3-propanesultone, 1,4-butanesultone, and naphthalsultone. These may be used individually 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 a sulfide-based inorganic solid electrolyte material according to this embodiment. The content of the solid electrolyte in the solid electrolyte layer according to this embodiment is not particularly limited as long as the desired insulation properties can be obtained, but it is preferably in the range of 10% by volume or more and 100% by volume or less, and more preferably in the range of 50% by volume or more and 100% by volume or less. In particular, in this embodiment, it is preferable that the solid electrolyte layer is composed only of a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to this embodiment.

[0103] Furthermore, the solid electrolyte layer according to this embodiment may 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, for example, in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm.

[0104] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. It should be noted that the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. [Examples]

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

[0106] [1] Manufacturing of P2S5 <Example 1> As the raw material phosphorus pentasulfide composition, phosphorus pentasulfide manufactured by Perimeter Solutions (product name: Normal / S, melting point: 289.9°C, crystallinity: 31%) was used. Next, the raw material phosphorus pentasulfide composition was placed in a quartz container and set in a vacuum heating device (manufactured by Furukawa Machinery & Metal Co., Ltd.). Then, after repeating vacuum gas exchange three times, it was heated at 200°C for 7 hours under aeration of 10 ml / min of Ar gas. Next, the components accumulated at the bottom of the quartz container were collected and ground in an agate mortar for 5 minutes to obtain powdered high-crystallinity phosphorus pentasulfide composition 1. Various evaluations were performed on the obtained high-crystallinity phosphorus pentasulfide composition 1. The results are shown in Table 1.

[0107] <Example 2> As the raw material phosphorus pentasulfide composition, phosphorus pentasulfide (product name: SUPERIOR GRADE Powder, melting point: 287.6°C, crystallinity: 16.6%) manufactured by LIAONING RUIXING CHEMICAL GROUP was used. Next, the raw material phosphorus pentasulfide composition was placed in a quartz container and set in a vacuum heating device (manufactured by Furukawa Machinery & Metal Co., Ltd.). Then, after repeating vacuum gas exchange three times, it was heated at 200°C for 7 hours under aeration of 10 ml / min of Ar gas. Next, the components accumulated at the bottom of the quartz container were collected and ground in an agate mortar for 5 minutes to obtain a powdered high-crystallinity phosphorus pentasulfide composition 2. Various evaluations were performed on the obtained high-crystallinity phosphorus pentasulfide composition 2. The results are shown in Table 1.

[0108] <Comparative Example 1> As the raw material phosphorus pentasulfide composition, phosphorus pentasulfide (product name: SUPERIOR GRADE Powder, melting point: 287.6°C, crystallinity: 16.6%) manufactured by LIAONING RUIXING CHEMICAL GROUP was used. Next, the raw material phosphorus pentasulfide composition was placed in a quartz container and set in a vacuum heating device (manufactured by Furukawa Machinery & Metal Co., Ltd.). Then, it was vacuum heated at 300°C for 2 hours under a reduced pressure of -0.094 MPa. Next, the components accumulated at the bottom of the quartz container were collected and ground in an agate mortar for 5 minutes to obtain powdered phosphorus pentasulfide composition 3. Various evaluations were performed on the obtained phosphorus pentasulfide composition 3. The results are shown in Table 1.

[0109] <Comparative Example 2> For phosphorus pentasulfide composition 4, powdered phosphorus pentasulfide (product name: SUPERIOR GRADE Powder, melting point: 287.6°C, crystallinity: 16.6%) manufactured by LIAONING RUIXING CHEMICAL GROUP was used as is. Various evaluations were performed on phosphorus pentasulfide composition 4. The results are shown in Table 1.

[0110] The phosphorus pentasulfide compositions used in the examples and comparative examples here, manufactured by LIAONING RUIXING CHEMICAL GROUP, are all sold as high-purity grades.

[0111] [2] Manufacturing of sulfide-based inorganic solid electrolyte materials Sulfide-based inorganic solid electrolyte materials were prepared using the following procedure. The raw materials used were Li2S powder (manufactured by Furukawa Machinery & Metal Co., Ltd., 99.9% purity), Li3N powder (manufactured by Furukawa Machinery & Metal Co., Ltd.), and P2S5 powder. For the P2S5 powder, the highly crystalline phosphorus pentasulfide composition obtained in the examples and the phosphorus pentasulfide composition obtained in the comparative examples were used, respectively. First, a rotary blade type pulverizer and an alumina pot (internal volume 400 mL) were placed inside a glove box. Then, high-purity dry argon gas (H2O < 1 ppm, O2 < 1 ppm) obtained through a gas purification device was injected into the glove box, and vacuum degassing was performed three times. Next, in a glove box, a rotary blade type pulverizer (rotation speed 18,000 rpm) was used to mix a total of 5 g of Li2S powder, P2S5 powder, and Li3N powder (Li2S:P2S5:Li3N = 71.1:23.7:5.3 (mol%)) (the process of mixing for 10 seconds and letting it stand for 10 seconds was repeated 10 times (cumulative mixing time: 100 seconds)) to prepare a raw material composition for a sulfide-based inorganic solid electrolyte material (hereinafter referred to as "raw material composition").

[0112] Next, the raw material composition and 500g of 10mm diameter ZrO2 balls were placed inside an alumina pot (internal volume 400mL) in the glove box, and the pot was sealed. Next, the alumina pot was removed from the glove box and attached to a ball mill machine set up in a dry air atmosphere introduced through a membrane air dryer. The alumina pot was then subjected to mechanochemical treatment at 120 rpm for 500 hours to vitrify the raw material composition. After 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 inside the glove box, and the resulting powder was transferred from the alumina pot to a carbon crucible. The powder was then annealed at 290°C for 2 hours in a heating furnace installed inside the glove box. The obtained sulfide-based inorganic solid electrolyte materials were evaluated in various ways. The results are shown in Table 1.

[0113] [3]Measurement method The following examples and comparative examples describe the measurement methods performed on phosphorus pentasulfide compositions and sulfide-based inorganic solid electrolyte materials.

[0114] (Degree of crystallinity) First, using an X-ray diffractometer (Rigaku Corporation, RINT2000), the X-ray diffraction spectra of the highly crystallinity phosphorus pentasulfide composition obtained in the example and the phosphorus pentasulfide composition obtained in the comparative example were determined by X-ray diffraction analysis under the following conditions: voltage 40kV, current 40mA, divergence slit 1°, divergence slit vertical limit 10mm, scattering slit 1°, light-receiving slit 0.3mm, measurement start angle 3°, and measurement end angle 90°. CuKα radiation was used as the radiation source. The sample holder was a glass sample plate (Cat No. 9200, sample area 20mm x 20mm, depth 0.5mm). Next, the degree of crystallinity Xc of the highly crystallinity phosphorus pentasulfide composition obtained in the example and the phosphorus pentasulfide composition obtained in the comparative example was calculated from the obtained X-ray diffraction spectra using the following peak separation method. First, without considering the effects of incoherent scattering or lattice disorder, the X-ray diffraction pattern was separated into crystalline diffraction curves and amorphous halos using a profile fitting technique. For profile fitting, the analysis software included with the X-ray diffractometer (Rigaku Corporation, product name: Integrated Powder X-ray Analysis Software PDXL Applied Analysis (Crystallization)) was used. The specific procedure for calculating the degree of crystallinity is as follows (see Figure 3; quoted from Rigaku Co., Ltd., X-ray Diffraction Handbook, February 21, 2000, 3rd edition, p. 83, Figure 3.6.2). (1) Background separation The X-ray intensities from the low-angle to the high-angle side were connected by a straight line, and the area under the line was defined as the background. (2) Separation of the halo The halo pattern due to amorphous materials was estimated, and the halo was separated from the scattering curve after subtracting the background. (3) Separation of crystalline diffraction curves The crystalline diffraction curves were separated using the same method as in (2) above. (4) Calculation of crystallinity The degree of crystallinity Xc was calculated from equation (2) below using the area under the curves (integral intensity) of the diffraction curves of the amorphous component (amorphous halo) and the crystalline component (crystalline diffraction curve), which were separated from the scattering curve. Xc = {Ic / (Ic+Ia)} × 100 (2) Ic: Area under the curve (integral intensity) of the diffraction curve of the crystalline component (crystalline diffraction curve) Ia: Area under the diffraction curve of the amorphous component (amorphous halo) (integral intensity)

[0115] (Heat of fusion, melting point) The heat of fusion was measured using a differential scanning calorimeter for the highly crystallinity phosphorus pentasulfide compositions obtained in the examples and the phosphorus pentasulfide compositions obtained in the comparative examples. Under an argon atmosphere, 20-25 mg of the phosphorus pentasulfide composition was weighed into an aluminum pan, 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 flow rate 100 ml / min. A DSC6300 (Seiko Instruments Corporation) differential scanning calorimeter was used. In all examples and comparative examples, an endothermic peak was observed in the temperature range between 280°C and 300°C in the obtained DSC curves. The amount of heat of fusion was calculated by determining the area enclosed by the endothermic fusion curve, which includes an endothermic peak in the temperature range of 280°C to 300°C, and the baseline in the resulting DSC curve. Furthermore, 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) Regarding the highly crystallinity phosphorus pentasulfide composition obtained in the examples and the phosphorus pentasulfide composition obtained in the comparative examples, the solid 31 The phosphorus pentasulfide content was measured using P-NMR spectroscopy. First, the test sample was filled into a 3.2 mm diameter sample tube inside a glove box purged with N2 gas. The tube was then rotated at a magic angle (54.7 degrees) relative to the external magnetic field (Magic Angle Spinning: MAS), and measurements were performed under the following conditions. Equipment: JNM-ECA-600 manufactured by JEOL RESONANCE Co., Ltd. Observation frequency: 242.95MHz Pulse width: 90° pulse Pulse waiting time: 2800 seconds Total number of times: 64 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, see Reference 1 "Hellmut Eckert, Cheryl S. Liang and Galen D. Stucky: 31 P magic angle spinning NMR of crystalline phosphorous sulfides. Correlation of 31 Referring to "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 described below, and the integral value of each peak was calculated. At this time, the chemical shifts of P2S5 were set to 40-52 ppm, P4S9 to 52-70 ppm, P4S7 to 80-90 ppm, 90-100 ppm, and 110-115 ppm, and P4S3 to 80-90 ppm and 90-100 ppm. The ratio of the integral value of the peaks present at 40-52 ppm to the sum of the integral values ​​of all peaks was calculated, and this ratio was defined as the phosphorus pentasulfide content.

[0117] (median diameter d) 50 ) Using a laser diffraction scattering particle size distribution analyzer (Malvern, Mastersizer 3000), the particle size distribution of the highly crystallinity phosphorus pentasulfide composition obtained in the examples and the phosphorus pentasulfide composition obtained in the comparative example was measured by laser diffraction scattering. From the measurement results, the median diameter d at which the cumulative frequency in the volume-based cumulative frequency distribution curve reaches 50% was determined for the phosphorus pentasulfide composition. 50 They sought it.

[0118] (Lithium-ion conductivity) Using the highly crystallinity phosphorus pentasulfide composition obtained in the examples and the phosphorus pentasulfide composition obtained in the comparative examples, sulfide-based inorganic solid electrolyte materials were prepared using the procedure described above, and the lithium ion conductivity of the obtained powders was measured by the AC impedance method. Lithium ion conductivity was measured using a Biologic SP-300 potentiostat / galvanostat. The sample size was 9.5 mm in diameter and 1.2-2.0 mm in thickness. The measurement conditions were: applied voltage of 10 mV, measurement temperature of 27.0 °C, measurement frequency range of 0.1 Hz to 7 MHz, and lithium foil electrodes. Here, as samples for lithium ion conductivity measurement, sulfide-based inorganic solid electrolyte materials were prepared using the procedure described above, employing the highly crystallinity phosphorus pentasulfide composition obtained in the Examples and the phosphorus pentasulfide composition obtained in the Comparative Example. A plate-shaped sulfide-based inorganic solid electrolyte material with a diameter of 9.5 mm and a thickness of 1.2 to 2.0 mm was obtained by pressing 150 mg of the resulting powder at 270 MPa for 10 minutes using a press device.

[0119] (Measurement of the maximum value of the oxidative decomposition current) Using the highly crystallinity phosphorus pentasulfide composition obtained in the examples and the phosphorus pentasulfide composition obtained in the comparative examples, sulfide-based inorganic solid electrolyte materials were prepared using the procedure described above. Using a press, 120-150 mg of the obtained powder was pressed at 270 MPa for 10 minutes to obtain plate-shaped sulfide-based inorganic solid electrolyte materials (pellets) with a diameter of 9.5 mm and a thickness of 1.3 mm. Next, Li foil was pressed onto one side of the obtained pellet as a reference electrode and counter electrode at 18 MPa for 10 minutes, and SUS314 foil was tightly attached to the other side as a working electrode. Next, using a Biologic SP-300 potentiostat / galvanostat, the maximum value of the oxidative decomposition current of a sulfide-based inorganic solid electrolyte material was determined under the conditions of a temperature of 25°C, a sweep voltage range of 0-5V, and a voltage sweep speed of 5mV / sec.

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

[0121] [Table 1]

[0122] The phosphorus pentasulfide composition of the example achieved both high recovery rate and high lithium ion conductivity, making it useful for the production of sulfide-based inorganic solid electrolyte materials. Here, Figure 2 shows the X-ray diffraction spectra of the phosphorus pentasulfide compositions obtained by the production methods of the phosphorus pentasulfide compositions of the examples and comparative examples. Furthermore, Figure 5 shows the DSC curve for high temperatures, and Figure 6 shows the DSC curve for low temperatures. [Explanation of symbols]

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

Claims

1. A phosphorus pentasulfide composition, The degree of crystallinity calculated from the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source is between 40% and 80%. Under conditions of 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 flow rate of 100 ml / min, the DSC curve of the phosphorus pentasulfide composition obtained by measurement using a differential scanning calorimeter showed an endothermic peak in the temperature range of 280°C to 300°C. A phosphorus pentasulfide composition wherein the heat of fusion of the endothermic peak is 60 J / g or more and 100 J / g or less.

2. A phosphorus pentasulfide composition according to claim 1, A phosphorus pentasulfide composition in which the phosphorus pentasulfide content is 70% by mass or more.

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

4. A phosphorus pentasulfide composition according to any one of claims 1 to 3, In a volume-based cumulative frequency distribution curve measured using a laser diffraction scattering particle size distribution analyzer, the median diameter d is the value at which the cumulative frequency reaches 50%. ５０ A phosphorus 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 phosphorus pentasulfide composition according to any one of claims 1 to 4 and lithium sulfide.

6. A sulfide-based inorganic solid electrolyte material comprising a mechanically treated product of the phosphorus pentasulfide composition according to any one of claims 1 to 4 and lithium sulfide.

7. A sulfide-based inorganic solid electrolyte material according to claim 6, The lithium-ion conductivity measured by the AC impedance method under measurement conditions of 27.0°C, applied voltage of 10 mV, and measurement frequency range of 0.1 Hz to 7 MHz was 1.0 × 10⁻⁶. －３ S.cm －１ The above describes sulfide-based inorganic solid electrolyte materials.

8. A sulfide-based inorganic solid electrolyte material according to claim 6 or 7, A sulfide-based inorganic solid electrolyte material in which the maximum value of the oxidative decomposition current of the sulfide-based inorganic solid electrolyte material measured under the conditions of a temperature of 25°C, a sweep voltage range of 0 to 5V, and a voltage sweep speed of 5mV / second is 0.50μA or less.

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

10. A solid electrolyte comprising a sulfide-based inorganic solid electrolyte material according to any one of claims 6 to 8.

11. A solid electrolyte membrane containing the solid electrolyte described in claim 10 as a main component.

12. A solid-state lithium-ion battery comprising a positive electrode containing a positive electrode active material layer, an electrolyte layer, and a negative electrode containing a negative electrode active material layer, 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 comprises a sulfide-based inorganic solid electrolyte material according to any one of claims 6 to 8.

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