Sulfide solid electrolyte and method for producing same

Abstract

An object of the present invention is to provide a sulfide solid electrolyte having a reduced specific surface area, an electrode mixture, a slurry, and a solid-state battery using the sulfide solid electrolyte, and a method for producing the sulfide solid electrolyte. [Solution] The present invention provides a sulfide solid electrolyte containing lithium (Li), phosphorus (P), and sulfur (S), which contains a crystalline phase having peaks at 2θ=23.2°±1.00° and 2θ=29.2°±0.500° in an X-ray diffraction pattern measured using CuKα1 radiation.

Description

[Technical Field]

[0001] The present invention relates to a sulfide solid electrolyte, an electrode mixture, a slurry, and a battery using the sulfide solid electrolyte, and a method for producing the sulfide solid electrolyte. [Background technology]

[0002] Solid-state batteries do not use flammable organic solvents, which allows for simplified safety devices, and are superior in manufacturing cost and productivity. They also have the advantage of being able to be stacked in series within the cell to achieve high voltage. The sulfide solid electrolyte used in solid-state batteries prevents the movement of ions other than lithium ions, which is expected to lead to improved safety and durability, such as preventing side reactions caused by the movement of anions.

[0003] Known sulfide solid electrolytes include those containing a crystalline phase having an argyrodite-type crystal structure (see, for example, Patent Documents 1 to 5).

[0004] Furthermore, a method for producing a sulfide solid electrolyte is known in which a raw material containing lithium (Li), sulfur (S), and phosphorus (P) as constituent elements is heat-treated to obtain a sulfide solid electrolyte having an argyrodite-type crystal structure, the sulfide solid electrolyte is pulverized to obtain a sulfide solid electrolyte precursor, and the sulfide solid electrolyte precursor is heat-treated at a temperature at which grain growth does not occur (Patent Document 6).

[0005] Patent Document 6 describes a method for producing a powder with an average particle size D 50 It is described that a sulfide solid electrolyte having a particle size of 2.1 μm to 4.5 μm was obtained. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-250580 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-024874 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-033732 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-044249 [Patent Document 5] Japanese Patent Application Laid-Open No. 2012-043646 [Patent Document 6] Japanese Patent Application Publication No. 2019-036536 Summary of the Invention [Problem to be solved by the invention]

[0007] In an all-solid-state battery, to obtain good battery characteristics, it is preferable that the sulfide solid electrolyte be uniformly distributed inside the positive and negative electrodes. To achieve such a uniform distribution of the sulfide solid electrolyte, it is preferable to reduce the particle size of the sulfide solid electrolyte. The particle size of the sulfide solid electrolyte can be reduced by pulverizing the sulfide solid electrolyte. However, pulverization generates fine particles and irregularly shaped particles, which increases the specific surface area of ​​the sulfide solid electrolyte and increases the viscosity of the slurry containing the sulfide solid electrolyte. As a result, a large amount of solvent is required to adjust the viscosity of the slurry, which increases costs and reduces battery productivity. Therefore, it is necessary to reduce the specific surface area of ​​the sulfide solid electrolyte.

[0008] Furthermore, when sulfide solid electrolytes react with moisture in the air, they generate toxic hydrogen sulfide gas and their ionic conductivity decreases due to decomposition. This increases the cost of maintaining a low-moisture environment during battery production and reduces battery productivity. If a solid electrolyte has a small specific surface area, the area that reacts with moisture in the air can be reduced, thereby suppressing the progress of the reaction. Therefore, from these perspectives as well, it is necessary to reduce the specific surface area of ​​sulfide solid electrolytes.

[0009] Therefore, an object of the present invention is to provide a sulfide solid electrolyte having a reduced specific surface area, an electrode mixture, a slurry, and a solid-state battery using the sulfide solid electrolyte, and a method for producing the sulfide solid electrolyte. [Means for solving the problem]

[0010] The present inventors used a sulfide solid electrolyte material containing phosphorus (Li), phosphorus (P), and sulfur (S) as an intermediate and heat-treated the intermediate under specified conditions. As a result, they discovered that the specific surface area of ​​the resulting sulfide solid electrolyte was reduced. Furthermore, the present inventors further investigated the resulting sulfide solid electrolyte and found that a crystalline phase having peaks at 2θ = 23.2° ± 1.00° and 2θ = 29.2° ± 0.500° in the X-ray diffraction pattern measured using CuKα1 radiation was formed in the sulfide solid electrolyte. It is presumed that the crystalline phase having peaks at 2θ = 23.2° ± 1.00° and 2θ = 29.2° ± 0.500° in the X-ray diffraction pattern measured using CuKα1 radiation is formed due to a reaction of fine particles contained in the intermediate when the intermediate is heat-treated. The present invention was completed based on these findings and includes the following inventions.

[0011] [1] Contains the elements lithium (Li), phosphorus (P) and sulfur (S), A sulfide solid electrolyte having peaks at 2θ=23.2°±1.0° and 2θ=29.2°±0.5° in an X-ray diffraction pattern measured using CuKα1 radiation. [2] An electrode mixture comprising the sulfide solid electrolyte according to [1] above and an active material. [3] A slurry containing the sulfide solid electrolyte according to [1] above and a dispersion medium. [4] A battery comprising: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein the solid electrolyte layer contains the sulfide solid electrolyte according to [1] above. [5] The following process: (1) preparing a sulfide solid electrolyte material containing lithium (Li), phosphorus (P), and sulfur (S) as an intermediate; and (2) heat-treating the intermediate to obtain the sulfide solid electrolyte described in [1] above; A method for producing a sulfide solid electrolyte, comprising: [Effects of the Invention]

[0012] The present invention provides a sulfide solid electrolyte having a reduced specific surface area, an electrode mixture, a slurry, and a solid-state battery using the sulfide solid electrolyte, and a method for producing the sulfide solid electrolyte. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a process diagram showing an example of the method for producing a sulfide solid electrolyte of the present invention. [Figure 2] FIG. 2 is a process diagram showing an example of step (1) in the method for producing a sulfide solid electrolyte of the present invention. [Figure 3] FIG. 3 is a process diagram showing an example of step (2) in the method for producing a sulfide solid electrolyte of the present invention. [Figure 4] FIG. 4 is a diagram showing the X-ray diffraction patterns of the sulfide solid electrolytes produced in Comparative Example 1 and Examples 1 to 5. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Terminology> The terms used in this specification will be explained below. The following explanations of terms apply throughout this specification unless otherwise specified.

[0015] <Powder> Powder is an aggregate of particles.

[0016] <D 10 , D 50 and D 95 > For a certain powder, the D 10 , D50 and D 95 are, respectively, the particle diameters at which the cumulative volume is 10%, 50%, and 95% in the volume-based particle size distribution of the powder measured by the laser diffraction scattering method, and the unit is μm. D 10 , D 50 and D 95 The measurement of and D is performed, for example, according to the conditions described in the examples. Note that Ds 50 is generally called the median diameter.

[0017] <BET Specific Surface Area> Regarding a certain powder, the BET specific surface area of the powder is the specific surface area of the powder measured by the gas adsorption method using nitrogen gas, and the unit is m 2 / g. The measurement of the BET specific surface area is performed, for example, according to the conditions described in the examples.

[0018] <True Density> Regarding a certain powder, the true density of the powder is the density of the powder measured by the pycnometer method, and the unit is g / cm 3 . The measurement of the true density is performed, for example, according to the conditions described in the examples.

[0019] <CS Value> Regarding a certain powder, the CS value of the powder is the surface area per unit volume of the powder when the shape of the particles constituting the powder is assumed to be spherical, and the unit is m 2 / cm 3 . The CS value of the powder is based on the volume-based particle size distribution of the powder measured by the laser diffraction scattering method, and is obtained from the following formula: CS value (m 2 / cm 3 ) = 6 / MA. Note that MA is the area average particle diameter (μm), and is obtained from the following formula: MA (μm) = ΣVi / Σ(Vi / di) [where Vi is the frequency and di is the median value of the particle size range]. The measurement of the CS value is performed, for example, according to the conditions described in the examples. s

[0020] <(A × B) / C> Regarding a certain powder, the following formula: (A×B) / C [In the formula, A is the BET specific surface area (m 2 / g), and B is the true density of the powder (g / cm 3 ), and C is the CS value (m 2 / cm 3 ) is the CS value (m 2 / cm 3 ) to true density (g / cm 3 ) to calculate the surface area (m 2 / g) and the specific surface area (m 2 / g) In other words, the closer the value obtained by the above formula is to 1.0, the closer the shape of the particles that make up the powder is to being spherical.

[0021] ≪Sulfide solid electrolyte≫ The sulfide solid electrolyte of the present invention contains lithium (Li), phosphorus (P), and sulfur (S).

[0022] The contents of lithium (Li), phosphorus (P) and sulfur (S) in the sulfide solid electrolyte of the present invention can be adjusted as appropriate.

[0023] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the content of lithium (Li) element is preferably 41 mol% or more and 50 mol% or less, more preferably 41 mol% or more and 48 mol% or less, even more preferably 42 mol% or more and 47 mol% or less, and even more preferably 43 mol% or more and 45 mol% or less, based on the total molar amount of the constituent elements of the sulfide solid electrolyte of the present invention.

[0024] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the content of phosphorus (P) element is preferably 7.0 mol % or more and 20 mol % or less, more preferably 7.2 mol % or more and 18 mol % or less, even more preferably 7.5 mol % or more and 16 mol % or less, and even more preferably 7.7 mol % or more and 12 mol % or less, based on the total molar amount of the constituent elements of the sulfide solid electrolyte of the present invention.

[0025] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the content of sulfur (S) element is preferably 31 mol% or more and 43 mol% or less, more preferably 32 mol% or more and 42 mol% or less, even more preferably 33 mol% or more and 40 mol% or less, and still more preferably 34 mol% or more and 38 mol% or less, based on the total molar amount of the constituent elements of the sulfide solid electrolyte of the present invention.

[0026] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the ratio of the lithium (Li) element content to the phosphorus (P) element content (lithium (Li) element content / phosphorus (P) element content) is preferably 4.8 or more and 7.0 or less, more preferably 5.0 or more and 6.4 or less, and even more preferably 5.2 or more and 5.8 or less, in molar ratio.

[0027] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the ratio of the sulfur (S) element content to the phosphorus (P) element content (sulfur (S) element content / phosphorus (P) element content) is preferably 3.6 or more and 6.0 or less, more preferably 4.0 or more and 5.0 or less, and even more preferably 4.2 or more and 4.6 or less, in terms of molar ratio.

[0028] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the sulfide solid electrolyte of the present invention preferably further contains at least one halogen (X) element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), and more preferably further contains at least one halogen (X) element selected from chlorine (Cl) and bromine (Br).

[0029] The content of the halogen (X) element can be adjusted appropriately.

[0030] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the content of the halogen (X) element is preferably 3.7 mol% or more and 19 mol% or less, more preferably 4.0 mol% or more and 17 mol% or less, even more preferably 8.0 mol% or more and 15 mol% or less, and even more preferably 10 mol% or more and 14 mol% or less, based on the total molar amount of the constituent elements of the sulfide solid electrolyte of the present invention. When the sulfide solid electrolyte of the present invention contains two or more halogen (X) elements, the "content of the halogen (X) element" means the total content of the two or more halogen (X) elements.

[0031] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, the ratio of the halogen (X) element content to the phosphorus (P) element content (halogen (X) element content / phosphorus (P) element content) is preferably 0.50 or more and 2.1 or less, more preferably 0.80 or more and 2.0 or less, and even more preferably 1.2 or more and 1.8 or less, in terms of molar ratio.

[0032] The sulfide solid electrolyte of the present invention may contain one or more elements other than lithium (Li), phosphorus (P), sulfur (S), and halogens (X) (hereinafter referred to as "other elements"). Examples of other elements include silicon (Si), germanium (Ge), tin (Sn), lead (Pb), boron (B), aluminum (Al), gallium (Ga), arsenic (As), antimony (Sb), and bismuth (Bi).

[0033] The total molar amount of the constituent elements of the sulfide solid electrolyte of the present invention and the molar amount of each element can be measured by dissolving the sulfide solid electrolyte of the present invention by alkali fusion or the like and measuring the amount of elements in a solution using a known method such as inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0034] The sulfide solid electrolyte of the present invention has peaks at 2θ=23.2°±1.0° and 2θ=29.2°±0.50° in an X-ray diffraction pattern measured using CuKα1 radiation. When the peaks are due to a certain crystalline phase, the crystalline phase is considered to be a crystalline phase having a crystalline structure belonging to the space group Pmna (hereinafter, sometimes simply referred to as the "Pmna phase" or "first crystalline phase").

[0035] The lower limit of the content of the first crystalline phase is not particularly limited. The content of the first crystalline phase may be, for example, 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more, relative to all crystalline phases constituting the sulfide solid electrolyte of the present invention. The upper limit of the content of the first crystalline phase is also not particularly limited. The content of the first crystalline phase may be, for example, 20% by mass or less, 5% by mass or less, or 3% by mass or less, relative to all crystalline phases constituting the sulfide solid electrolyte of the present invention. The proportion of the crystalline phase can be confirmed, for example, by XRD measurement.

[0036] The presence of peaks at the predetermined positions of the sulfide solid electrolyte of the present invention can be confirmed by an X-ray diffraction pattern measured using CuKα radiation. As CuKα radiation, for example, CuKα1 radiation can be used.

[0037] In the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, in addition to the positions of 2θ=23.2°±1.0° and 2θ=29.2°±0.50°, the peaks at 2θ=19.5°±1.0° and 2θ=30.5°±0.50° may be present. The peaks appearing at 2θ=19.5°±1.0° and 2θ=30.5°±0.50° are derived from the first crystalline phase, as are the peaks appearing at 2θ=23.2°±1.0° and 2θ=29.2°±0.50°.

[0038] The position of the peak derived from the first crystalline phase is expressed as the median ±1.0° or the median ±0.50°, but is preferably expressed as the median ±0.50°, and more preferably as the median ±0.30°.

[0039] Hereinafter, in the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, the peaks at 2θ = 19.5 ± 1.0 °, 23.2 ± 1.0 °, 29.2 ± 0.50 °, and 30.5 ± 0.50 ° derived from the first crystalline phase will be referred to as "peak P1", "peak P2", "peak P3", and "peak P4", respectively.

[0040] The presence or absence of peaks in each range in the X-ray diffraction pattern can be determined, for example, as follows. The average intensity of 10 points from +0.7° toward the high-angle side of the expected peak position and the average intensity of 10 points from -0.7° toward the low-angle side of the expected peak position are defined as backgrounds. Here, the former is defined as background 1, and the latter is defined as background 2. Intensity 1 obtained by subtracting background 1 from the measurement data and intensity 2 obtained by subtracting background 2 are calculated. Of the two obtained intensities, the position where at least one intensity has a maximum of 40 counts or more is defined as a peak, and the intensity at that position is defined as the peak intensity of the respective peak. However, the measurement conditions are selected so that the maximum peak intensity is 10,000 counts or more. It was confirmed that the sulfide solid electrolytes obtained in Examples 1 to 5 described below all had peaks at 2θ = 23.2° ± 1.0° and 2θ = 29.2° ± 0.5°.

[0041] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, in the X-ray diffraction pattern measured using CuKα1 line, the sulfide solid electrolyte of the present invention preferably has peaks at positions of 2θ = 15.34° ± 1.0° and 2θ = 25.19° ± 1.0°. The peak is derived from a crystal phase having an argyrodite-type crystal structure (hereinafter, may be simply referred to as "argyrodite-type crystal phase" or "second crystal phase"). That is, from the viewpoint of improving the lithium ion conductivity, the sulfide solid electrolyte of the present invention preferably contains an argyrodite-type crystal phase. The argyrodite-type crystal structure is a crystal structure possessed by a group of compounds derived from a mineral represented by the chemical formula: Ag8GeS6. The argyrodite-type crystal structure is preferably cubic system.

[0042] When the sulfide solid electrolyte of the present invention contains a first crystal phase and a second crystal phase, the sulfide solid electrolyte of the present invention may be composed of the first crystal phase and the second crystal phase, or may be composed of the first crystal phase, the second crystal phase, and one or more other phases. The other phase may be a crystal phase or an amorphous phase. Examples of the other phase include a Li2S phase, a LiCl phase, a LiBr phase, LiBr x Cl 1-x (0 < x < 1), a Li3PS4 phase, and the like.

[0043] The content ratio of the second crystal phase may be, for example, 10% by mass or more, 20% by mass or more, or 50% by mass or more with respect to all crystal phases constituting the sulfide solid electrolyte of the present invention. Among them, it is preferable that the sulfide solid electrolyte of the present invention contains the second crystal phase as a main phase. Here, the "main phase" refers to the phase having the largest ratio with respect to the total amount of all crystal phases constituting the sulfide solid electrolyte of the present invention. When the second crystal phase is the main phase, the content ratio of the second crystal phase is preferably, for example, 60% by mass or more with respect to all crystal phases constituting the sulfide solid electrolyte of the present invention, and more preferably 70% by mass or more, 80% by mass or more, 90% by mass or more. The ratio of the crystal phase can be confirmed by, for example, XRD measurement.

[0044] In one embodiment, the second crystalline phase has the following formula (I): Li a PS b X c (I) It has a composition represented by the formula:

[0045] X is at least one halogen element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Iodine (I) tends to reduce lithium ion conductivity, and fluorine (F) is difficult to incorporate into the crystal structure. Therefore, X is preferably at least one halogen element selected from chlorine (Cl) and bromine (Br).

[0046] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, a is preferably 3.0 or more and 6.5 or less, more preferably 3.5 or more and 6.3 or less, and even more preferably 4.0 or more and 6.0 or less. When a has the above-mentioned lower limit, a decrease in the amount of Li in the crystal structure can be suppressed, and a decrease in lithium ion conductivity can be suppressed. On the other hand, when a has the above-mentioned upper limit, a decrease in vacancies at Li sites can be suppressed, and a decrease in lithium ion conductivity can be suppressed.

[0047] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, b is preferably 3.5 or more and 5.5 or less, more preferably 4.0 or more and 5.3 or less, and even more preferably 4.2 or more and 5.0 or less.

[0048] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, c is preferably 0.50 or more and 3.0 or less, more preferably 0.70 or more and 2.5 or less, and even more preferably 1.0 or more and 1.8 or less.

[0049] In another embodiment, the second crystalline phase has the following formula (II): Li 7-d PS 6-d X d(II) The composition represented by formula (II) is the stoichiometric composition of a crystalline phase having an argyrodite-type crystal structure.

[0050] In formula (II), X has the same meaning as in formula (I).

[0051] From the viewpoint of improving the lithium ion conductivity of the sulfide solid electrolyte of the present invention, d is preferably 0.40 or more and 2.2 or less, more preferably 0.80 or more and 2.0 or less, and even more preferably 1.2 or more and 1.8 or less.

[0052] In formula (I) or (II), a part of P may be substituted with one or more elements selected from silicon (Si), germanium (Ge), tin (Sn), lead (Pb), boron (B), aluminum (Al), gallium (Ga), arsenic (As), antimony (Sb), and bismuth (Bi). In this case, formula (I) is Li a (P 1-y M y )S b X c and formula (II) is Li 7-d (P 1-y M y )S 6-d X d where M is one or more elements selected from silicon (Si), germanium (Ge), tin (Sn), lead (Pb), boron (B), aluminum (Al), gallium (Ga), arsenic (As), antimony (Sb), and bismuth (Bi). y is preferably 0.010 or more and 0.70 or less, more preferably 0.020 or more and 0.40 or less, and even more preferably 0.050 or more and 0.20 or less.

[0053] The presence of the second crystalline phase in the sulfide solid electrolyte of the present invention can be confirmed by an X-ray diffraction pattern measured using CuKα radiation. As CuKα radiation, for example, CuKα1 radiation can be used.

[0054] In the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, in addition to the positions at 2θ = 15.34° ± 1.0° and 2θ = 25.19° ± 1.0°, a second crystal is present at one or more positions selected from 2θ = 17.74° ± 1.0°, 29.62° ± 1.0°, 30.97° ± 1.0°, 44.37° ± 1.0°, 47.22° ± 1.0°, and 51.70° ± 1.0°. It is more preferable that peaks derived from the second crystalline phase are present, and even more preferable that peaks derived from the second crystalline phase are present at all positions of 2θ=17.74°±1.0°, 29.62°±1.0°, 30.97°±1.0°, 44.37°±1.0°, 47.22°±1.0°, and 51.70°±1.0°, in addition to the positions of 2θ=15.34°±1.0° and 2θ=25.19°±1.0°. Note that the positions of the peaks derived from the second crystalline phase are expressed as a median ±1.0°, but are preferably expressed as a median ±0.50°, and more preferably as a median ±0.30°.

[0055] In the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, the peak having the maximum intensity among the peaks derived from the second crystalline phase is usually a peak present at 2θ=29.62°±1.0°. Hereinafter, the peak derived from the second crystalline phase present at 2θ=29.62°±1.0° will be referred to as "Peak P A " Sometimes it is said that

[0056] When the sulfide solid electrolyte of the present invention contains a first crystalline phase and a second crystalline phase, in the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, A The percentage of the intensity of peak P1 relative to the intensity of peak P1 (peak P1 intensity / peak P A The ratio (the strength of the tensile strength of the tensile strength × 100) is preferably 0.010% or more and 40% or less, more preferably 0.030% or more and 30% or less, and even more preferably 0.070% or more and 20% or less. When the ratio is within the above-mentioned range, the effects of the present invention become more pronounced.

[0057] When the sulfide solid electrolyte of the present invention contains a first crystalline phase and a second crystalline phase, in the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, A The percentage of the intensity of peak P2 relative to the intensity of peak P (intensity of peak P2 / peak P A The ratio (the intensity of the tensile strength of the tensile strength × 100) is preferably 0.010% or more and 40% or less, more preferably 0.050% or more and 30% or less, and even more preferably 0.10% or more and 20% or less. When the ratio is within the above-mentioned range, the effects of the present invention become more pronounced.

[0058] When the sulfide solid electrolyte of the present invention contains a first crystalline phase and a second crystalline phase, in the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, A The percentage of the intensity of peak P3 relative to the intensity of peak P (Intensity of peak P3 / Intensity of peak P A The ratio (the intensity of the saturation energy of the saturation energy × 100) is preferably 0.010% or more and 99% or less, more preferably 0.10% or more and 97% or less, and even more preferably 1.0% or more and 95% or less. When the ratio is within the above-mentioned range, the effects of the present invention become more pronounced.

[0059] Peak P A The peak intensities of P1 and P2 are calculated as follows: A line connecting the average intensity between 2θ = 26.5° and 26.9° and the average intensity between 2θ = 37.5° and 37.9° is used as the background, and the background is subtracted from the measurement data of each peak. A The peak intensity of P3 is calculated. A peak usually has a maximum, and the maximum value is the peak intensity.

[0060] Typically, the peak intensities of the low-intensity peaks P1 and P2 are determined as follows: The average intensity of 10 points from each assumed peak position +0.7° to the high-angle side is taken as the background, and the background is subtracted from the measurement data. The position where the intensity has a maximum of 40 counts or more is defined as a peak, and the intensity at that position is taken as the peak intensity of each peak. However, measurement conditions are selected so that the maximum peak intensity is 10,000 counts or more.

[0061] In the X-ray diffraction pattern of the sulfide solid electrolyte of the present invention measured using CuKα1 radiation, even if the peak derived from the first crystalline phase overlaps with other peaks and peak resolution is difficult, the position of the peak derived from the first crystalline phase can be determined by, for example, the integrated X-ray analysis software PDXL2 (manufactured by Rigaku Corporation) and the first-order differential value or intensity.

[0062] The method using the integrated X-ray analysis software PDXL2 is carried out as follows: First, select automatic from data processing and perform calculation and confirmation. Next, use the background editing menu in PDXL2 to edit the curve so that the background of the measured data is sufficiently extrapolated. Next, perform optimization, and determine the peak position from the obtained results in a state where the background and peak of the measured data and calculated values ​​can be sufficiently extrapolated.

[0063] The first derivative method is performed as follows: A seven-point weighted moving average is taken of the measurement data using a calculation program such as Excel, and a further seven-point weighted moving average is taken of the resulting calculation results to obtain I average (x). The difference between adjacent data points in the obtained I average (x) is taken as the first derivative, and the position where it switches from positive to negative and becomes zero, or the position where the first derivative is minimal near the expected peak, is taken as the peak position. I average(x)={I(x-3)+I(x-2)+I(x-1)+I(x)+I(x+1)+I(x+2)+I(x+3)} / 7

[0064] The sulfide solid electrolyte of the present invention is preferably in the form of a powder.

[0065] The particle size (D 10 , D 50 or D 95 ) is comparable to or significantly larger than the particle size of the sulfide solid electrolyte not containing the first crystalline phase, the specific surface area (BET specific surface area) of the sulfide solid electrolyte of the present invention can be significantly smaller than the specific surface area (BET specific surface area) of the sulfide solid electrolyte not containing the first crystalline phase.

[0066] The BET specific surface area of ​​the sulfide solid electrolyte of the present invention is preferably 4.0 m 2 / g or more 10m 2 / g or less, more preferably 5.0m 2 / g or more 9.0m 2 / g or less, and even more preferably 6.0m 2 / g or more 8.0m 2 / g or less.

[0067] To obtain good battery characteristics, it is preferable that the sulfide solid electrolyte be uniformly distributed within the positive and negative electrodes. To achieve such a uniform distribution, it is preferable to reduce the particle size of the sulfide solid electrolyte. The particle size of the sulfide solid electrolyte can be reduced by pulverizing the sulfide solid electrolyte. However, pulverization can result in irregularly shaped particles or secondary particles formed by agglomeration of fine particles produced during pulverization, which can increase the specific surface area of ​​the sulfide solid electrolyte. As the specific surface area of ​​the sulfide solid electrolyte increases, the amount of solvent adsorbed on the particle surface tends to increase. Therefore, as the specific surface area of ​​the sulfide solid electrolyte increases, the viscosity of the slurry containing the sulfide solid electrolyte increases. However, if the viscosity of the slurry increases, it is necessary to adjust the viscosity using a large amount of solvent. However, an increase in the amount of solvent used is one of the causes of increased costs and reduced battery productivity. Furthermore, when the sulfide solid electrolyte reacts with moisture in the atmosphere, it generates toxic hydrogen sulfide gas and decomposes, resulting in a decrease in ionic conductivity. As the specific surface area increases, the reaction area between the sulfide solid electrolyte and moisture in the atmosphere increases, leading to an increase in the amount of hydrogen sulfide gas generated and a decrease in ionic conductivity. This increases the cost of maintaining a low-moisture environment during battery production and reduces battery productivity. In view of the above, it is preferable to make the shape of the sulfide solid electrolyte as close to a perfect sphere as possible in order to suppress an increase in the specific surface area of ​​the sulfide solid electrolyte.

[0068] D of the sulfide solid electrolyte of the present invention 10 is not particularly limited, but from the viewpoint of uniformly distributing the sulfide solid electrolyte inside the positive and negative electrodes and obtaining good battery characteristics, it is preferably 0.20 μm or more and 20 μm or less, more preferably 0.30 μm or more and 10 μm or less, and even more preferably 0.45 μm or more and 5.0 μm or less.

[0069] D of the sulfide solid electrolyte of the present invention 50is not particularly limited, but from the viewpoint of uniformly distributing the sulfide solid electrolyte inside the positive and negative electrodes and obtaining good battery characteristics, it is preferably 0.10 μm or more and 100 μm or less, more preferably 0.50 μm or more and 50 μm or less, and even more preferably 1.0 μm or more and 10 μm or less.

[0070] D of the sulfide solid electrolyte of the present invention 95 is not particularly limited, but from the viewpoint of uniformly distributing the sulfide solid electrolyte inside the positive and negative electrodes and obtaining good battery characteristics, it is preferably 0.10 μm or more and 500 μm or less, more preferably 1.0 μm or more and 300 μm or less, and even more preferably 2.0 μm or more and 150 μm or less.

[0071] The value of (A×B) / C of the sulfide solid electrolyte of the present invention is not particularly limited, but from the viewpoint of making the effects of the present invention more remarkable, it is preferably 25 or less, more preferably 20 or less, and even more preferably 18 or less.

[0072] The true density of the sulfide solid electrolyte of the present invention is not particularly limited, but from the viewpoint of making the effects of the present invention more remarkable, it is preferably 1.0 g / cm 3 More than 4.0g / cm 3 or less, more preferably 1.2 g / cm 3 More than 3.0g / cm 3 More preferably, 1.6 g / cm or less 3 More than 2.5g / cm 3 The following is the result.

[0073] The CS value of the sulfide solid electrolyte of the present invention is not particularly limited, but from the viewpoint of making the effects of the present invention more remarkable, it is preferably 0.10 m 2 / cm 3 More than 20m 2 / cm 3 Less than 0.30m, more preferably 2 / cm 3 More than 10m 2 / cm 3 Less than or equal to 0.50 m, and even more preferably 2 / cm 3Over 8.0m 2 / cm 3 The following is the result.

[0074] ≪Electrode composite material≫ The electrode mixture of the present invention contains the sulfide solid electrolyte of the present invention and an active material.

[0075] In one embodiment, the electrode mixture of the present invention may be a negative electrode mixture or a positive electrode mixture. The negative electrode mixture contains at least a negative electrode active material, and the positive electrode mixture contains at least a positive electrode active material. The electrode mixture may contain a solid electrolyte, a conductive additive, and a binder as necessary.

[0076] Examples of the negative electrode active material include carbon materials and metal materials, and one of these may be used alone or two or more may be used in combination. As the carbon material and the metal material, materials commonly used as negative electrode active materials may be used as appropriate, and therefore, a description thereof will be omitted here. The negative electrode active material preferably has electron conductivity.

[0077] The positive electrode active material is a material capable of inserting and extracting lithium ions and can be appropriately selected from known positive electrode active materials. Examples of the positive electrode active material include metal oxides and sulfides. Examples of the metal oxide include transition metal oxides.

[0078] Other explanations regarding the electrode mixture can be the same as those for a general electrode mixture, and therefore will not be repeated here.

[0079] <Slurry> The slurry of the present invention contains the sulfide solid electrolyte of the present invention and a dispersion medium.

[0080] The content of the sulfide solid electrolyte of the present invention in the slurry of the present invention can be adjusted appropriately depending on the application of the slurry of the present invention. The slurry of the present invention has various viscosities depending on the content of the sulfide solid electrolyte of the present invention, and takes various forms such as ink and paste depending on the viscosity. The content of the sulfide solid electrolyte of the present invention in the slurry of the present invention is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 80% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less, based on the total mass of the slurry of the present invention.

[0081] The dispersion medium contained in the slurry of the present invention is not particularly limited as long as it is a liquid capable of dispersing the sulfide solid electrolyte of the present invention. Examples of the dispersion medium include water and organic solvents. The dispersion medium may be a single solvent or a mixture of two or more solvents.

[0082] ≪Battery≫ The battery of the present invention is a battery including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, and the solid electrolyte layer contains the sulfide solid electrolyte of the present invention. Note that the positive electrode layer, the negative electrode layer, and the solid electrolyte layer can be the same as those of a general battery, and therefore description thereof will be omitted here.

[0083] The battery of the present invention is preferably a solid-state battery, and more preferably a lithium solid-state battery. The lithium solid-state battery may be a primary battery or a secondary battery, but is preferably a lithium secondary battery. The solid-state battery includes not only a solid-state battery that does not contain any liquid or gel substance as an electrolyte, but also an embodiment that contains, for example, 50% by mass or less, 30% by mass or less, or 10% by mass or less of a liquid or gel substance as an electrolyte. Examples of the shape of the solid-state battery include a laminate type, a cylindrical type, and a prismatic type.

[0084] <Method for producing sulfide solid electrolyte> The method for producing a sulfide solid electrolyte of the present invention will be described below. As shown in FIG. 1 , the method for producing a sulfide solid electrolyte of the present invention comprises the following steps: (1) preparing a sulfide solid electrolyte material containing lithium (Li), phosphorus (P), and sulfur (S) as an intermediate; and (2) A step of heat-treating the intermediate prepared in step (1) to obtain the sulfide solid electrolyte of the present invention.

[0085] The intermediate prepared in step (1) is a precursor of the sulfide solid electrolyte of the present invention. In the present invention, the sulfide solid electrolyte of the present invention can be obtained by subjecting the intermediate obtained in step (1) to a heat treatment in step (2). That is, in the present invention, the sulfide solid electrolyte of the present invention having a peak due to the first crystalline phase is obtained by the heat treatment performed in step (2). Therefore, the intermediate is a material that does not have a peak due to the first crystalline phase. Note that "not having a peak" means that the criteria for the presence of a peak described in the above section "Sulfide Solid Electrolyte" are not met.

[0086] The composition of the intermediate can be adjusted appropriately taking into consideration the composition of the sulfide solid electrolyte of the present invention. The composition of the intermediate is usually the same as the composition of the sulfide solid electrolyte of the present invention. The intermediate preferably has a peak due to the second crystalline phase. The composition of the second crystalline phase contained in the intermediate can be adjusted appropriately taking into consideration the composition of the second crystalline phase contained in the sulfide solid electrolyte of the present invention. The composition of the second crystalline phase contained in the intermediate is usually the same as the composition of the second crystalline phase contained in the sulfide solid electrolyte of the present invention.

[0087] The intermediate may be composed of a second crystalline phase, or may be composed of the second crystalline phase and one or more other phases. The other phases are the same as those described in the above section "Sulfide Solid Electrolyte," and therefore will not be described here.

[0088] The content ratio of the second crystalline phase in the intermediate is the same as the content ratio of the second crystalline phase in the sulfide solid electrolyte of the present invention described above in the section <<Sulfide Solid Electrolyte>>, and therefore description thereof will be omitted here.

[0089] Intermediate D 10 is not particularly limited, but in step (2), the desired D 10 From the viewpoint of efficiently obtaining a sulfide solid electrolyte having the above formula, the particle size is preferably 0.10 μm or more and 1.0 μm or less, more preferably 0.20 μm or more and 0.80 μm or less, and even more preferably 0.30 μm or more and 0.60 μm or less.

[0090] Intermediate D 50 is not particularly limited, but from the viewpoint of efficiently obtaining a desired sulfide solid electrolyte in step (2), it is preferably 0.10 μm or more and 2.0 μm or less, more preferably 0.20 μm or more and 1.8 μm or less, even more preferably 0.30 μm or more and 1.4 μm or less, and even more preferably 0.40 μm or more and 1.0 μm or less.

[0091] Intermediate D 95 is not particularly limited, but from the viewpoint of efficiently obtaining the desired sulfide solid electrolyte in step (2), it is preferably 0.50 μm or more and 5.0 μm or less, more preferably 0.60 μm or more and 4.5 μm or less, and even more preferably 0.70 μm or more and 4.0 μm or less.

[0092] The value of (A×B) / C of the intermediate is not particularly limited, but from the viewpoint of efficiently obtaining the desired sulfide solid electrolyte in step (2), it may be more than 2.5 and not more than 5.0, 2.6 or more and not more than 5.0, 2.7 or more and not more than 4.5, or 2.8 or more and not more than 4.0.

[0093] The BET specific surface area of ​​the intermediate is not particularly limited, but is preferably 3.0 m from the viewpoint of efficiently obtaining the desired sulfide solid electrolyte in step (2). 2 / g or more 25m 2 / g or less, more preferably 5.0m 2 / g or more 20m 2 / g or less, and even more preferably 7.0m 2 / g or more 17m 2 / g or less.

[0094] The true density of the intermediate is not particularly limited, but is preferably 1.5 g / cm from the viewpoint of efficiently obtaining the desired sulfide solid electrolyte in step (2). 3 More than 5.0g / cm 3 or less, more preferably 1.7 g / cm 3 More than 4.5g / cm 3 More preferably, 1.9 g / cm or less 3 More than 4.0g / cm 3 The following is the result.

[0095] The CS value of the intermediate is not particularly limited, but is preferably 1.0 m from the viewpoint of efficiently obtaining the desired sulfide solid electrolyte in step (2). 2 / cm 3 More than 25m 2 / cm 3 Less than 2.0m, more preferably 2 / cm 3 More than 20m 2 / cm 3 Less than 3.0 m, and even more preferably 2 / cm 3 More than 15m 2 / cm 3 The following is the result.

[0096] In the present invention, it is preferable to heat-treat a raw material powder containing lithium (Li), phosphorus (P), and sulfur (S) to obtain a heat-treated body, pulverize the heat-treated body, and prepare the pulverized body as an intermediate, as shown in Fig. 2. This allows efficient preparation of a first raw material powder having desired properties.

[0097] The raw material powder is a raw material for the intermediate and is usually in powder form. The composition of the raw material powder can be adjusted appropriately taking into account the composition of the intermediate. The composition of the raw material powder is usually the same as the composition of the intermediate. The raw material powder does not have a peak due to either the first crystal phase or the second crystal phase. Furthermore, depending on the composition of the raw material powder, a heat-treated body having a peak due to the second crystal phase can be obtained by heat-treating the raw material powder.

[0098] The raw material powder can be, for example, a mixed powder containing one or more compounds containing lithium (Li), one or more compounds containing phosphorus (P), one or more compounds containing sulfur (S), and optionally one or more compounds containing halogen (X). When a compound containing lithium (Li), phosphorus (P), or halogen (X) contains sulfur (S), the compound also falls under the category of a compound containing sulfur (S). Therefore, the compound containing lithium (Li), phosphorus (P), or halogen (X) may be the same as the compound containing sulfur (S).

[0099] The compound containing lithium (Li), phosphorus (P), sulfur (S), and halogen (X) may be the same as a known compound generally used as a raw material for sulfide solid electrolytes, and therefore description thereof will be omitted here.

[0100] The raw material powder can be prepared by mixing powders of one or more compounds containing lithium (Li), one or more compounds containing phosphorus (P), one or more compounds containing sulfur (S), and optionally one or more compounds containing halogen (X). Mixing can be performed using, for example, a mortar, a ball mill, a vibration mill, a tumbling mill, a bead mill, a kneader, or the like. The raw material powder may contain reaction products produced by the mixing process. Mixing is preferably performed with a force sufficient to maintain the crystallinity of the raw material powder.

[0101] The raw material powder is, for example, a mixed powder containing Li2S powder, P2S5 powder, and LiCl powder and / or LiBr powder.

[0102] The heat treatment of the raw material powder in step (1) is preferably carried out under conditions that produce a sulfide solid electrolyte containing a second crystal phase. The heat treatment temperature is preferably 300°C to 550°C, more preferably 350°C to 500°C, even more preferably 400°C to 520°C, and even more preferably 450°C to 480°C. The heat treatment time can be adjusted appropriately depending on the composition of the raw material powder, the heat treatment temperature, and the like. The heat treatment time is preferably 1 hour to 10 hours, more preferably 2 hours to 8 hours, and even more preferably 3 hours to 6 hours. The heat treatment may be carried out in an inert gas atmosphere such as nitrogen or argon, but is preferably carried out in a hydrogen sulfide gas atmosphere.

[0103] The heat-treated body (sintered body) obtained by heat-treating the raw material powder is pulverized so as to obtain a pulverized body having the desired properties. This allows for the production of an intermediate body having the desired properties. 10 , D 50 and D 95 The preferred ranges of the intermediate D 10 , D 50 and D 95 The preferred range is the same as that of the above.

[0104] The heat-treated body (sintered body) obtained by heat-treating the raw material powder can be pulverized by a dry method or a wet method using, for example, a jet mill, a ball mill, a bead mill, etc. When pulverization is performed by a wet method, it is preferable to use a hydrocarbon solvent as the solvent.

[0105] After pulverization, classification may be carried out using a sieve with a predetermined mesh size. The pulverization conditions (e.g., the rotation speed of the pulverizer, the number of pulverization steps, the pulverization time, the energy applied to the heat-treated body, etc.) and the mesh size of the sieve used for classification can be appropriately adjusted depending on the particle size of the pulverized body to be obtained.

[0106] The heat treatment of the intermediate body prepared in step (1) is carried out at a temperature at which grain growth occurs. Therefore, the grain size of the heat-treated body obtained by the heat treatment of the intermediate body is larger than that of the intermediate body. For example, D10 is the intermediate D 10 It may be 1 to 20 times, 1.05 to 15 times, or 1.1 to 10 times. 50 For example, intermediate D 50 It may be 1.1 times or more and 200 times or less, 1.2 times or more and 100 times or less, or 1.3 times or more and 50 times or less. 95 For example, intermediate D 95 It may be 1.2 times or more and 200 times or less, 1.4 times or more and 150 times or less, or 2 times or more and 100 times or less.

[0107] By heat treating the intermediate prepared in step (1), strain inside the solid electrolyte particles contained in the intermediate is alleviated, crystallinity is increased, and sintering of the fine particles generated in the pulverization step is promoted.

[0108] The heat treatment of the intermediate prepared in step (1) is carried out under conditions that produce a sulfide solid electrolyte containing a first crystal phase. The heat treatment temperature is preferably 200°C to 500°C, more preferably 200°C to 450°C, even more preferably 220°C to 420°C, and even more preferably 240°C to 400°C. The heat treatment time of the intermediate can be adjusted appropriately depending on the composition of the intermediate, the heat treatment temperature, etc., but from the viewpoint of obtaining a sulfide solid electrolyte having a small specific surface area in step (2), it is preferably 0.5 hours to 5 hours, more preferably 1.5 hours to 4 hours, and even more preferably 2 hours to 3 hours. The heat treatment may be carried out in a hydrogen sulfide stream, but from the viewpoint of efficiently obtaining a sulfide solid electrolyte containing a first crystal phase (preferably a sulfide solid electrolyte containing both the first and second crystal phases) in step (2), it is preferably carried out in an inert gas atmosphere such as nitrogen or argon.

[0109] The heat-treated body (sintered body) obtained by heat-treating the intermediate may be pulverized as needed, for example, as shown in Fig. 3. The heat-treated body (sintered body) obtained by heat-treating the intermediate may be pulverized by a dry or wet method using, for example, a jet mill, a ball mill, a bead mill, or the like.

[0110] After pulverization, classification may be carried out using a sieve with a predetermined mesh size. The pulverization conditions (e.g., the rotation speed of the pulverizer, the number of pulverization steps, the pulverization time, the energy applied to the heat-treated body, etc.) and the mesh size of the sieve used for classification can be appropriately adjusted depending on the particle size of the pulverized body to be obtained. [Example]

[0111] In each example, the properties of the solid electrolyte were evaluated using the following methods.

[0112] <Composition> The sulfide solid electrolyte samples obtained in each example were completely dissolved, and the elemental composition of the samples was analyzed by ICP emission spectrometry.

[0113] <Crystal phase> The crystalline phase of the sulfide solid electrolyte sample was analyzed by X-ray diffraction (XRD, Cu source) to obtain an X-ray diffraction pattern. X-ray diffraction was performed using an XRD device "Smart Lab" manufactured by Rigaku Corporation under the following conditions: scanning axis: 2θ / θ, scanning range: 10 to 140°, step width: 0.01°, and scanning speed: 1° / min. Note that under these conditions, the maximum peak intensity was 10,000 counts or more. In Examples 1 to 3, X-ray diffraction was performed in a cell not exposed to the atmosphere.

[0114] <D 10 , D 50 and D 95 > The measurement of the particle size distribution of the sulfide solid electrolyte by the laser diffraction scattering method was carried out according to the following procedure. Using an automatic sample feeder for a laser diffraction particle size distribution measuring device ("Microtorac SDC" manufactured by Nikkiso Co., Ltd.), the flow rate of the measurement sample containing the sulfide solid electrolyte was set to 50%, and ultrasonic waves of 30 W were irradiated to the measurement sample containing the sulfide solid electrolyte for 60 seconds. Then, the particle size distribution was measured using a laser diffraction particle size distribution measuring machine "MT3000II" manufactured by Nikkiso Co., Ltd., and from the chart of the volume-based particle size distribution obtained, the particle diameters at which the cumulative volume was 10% by volume, 50% by volume, and 95% by volume were determined, and were designated as D 10 、D 50 及びD 95 respectively. In the measurement of D 10 、D 50 及びD 95 ,the organic solvent was passed through a 60 μm filter, the solvent refractive index was set to 1.50, the particle permeability condition was set to transmission, the particle refractive index was 1.59, the shape was set to non-spherical, the measurement range was 0.133 μm to 704.0 μm, the measurement time was 10 seconds, the measurement was performed twice, and the average value of the obtained measurement values was designated as D 10 、D 50 及びD 95 respectively.

[0115] The measurement sample containing the sulfide solid electrolyte was prepared as follows. First, 0.3 g of the sulfide solid electrolyte and 5.7 g of the dispersant-containing liquid (mass ratio of toluene:dispersant (SN Dispersant 9228 manufactured by San Nopco Ltd.) = 19:1) were manually mixed to prepare a slurry containing the sulfide solid electrolyte. Next, 6 ml of the slurry containing the sulfide solid electrolyte was added to an organic solvent (toluene) to prepare a measurement sample containing the sulfide solid electrolyte. In the measurement sample containing the sulfide solid electrolyte, the sulfide solid electrolyte is dispersed without aggregation. As long as the sulfide solid electrolyte can be dispersed without aggregation in the measurement sample containing the sulfide solid electrolyte, the type and amount of the dispersant can be appropriately changed.

[0116] <BET specific surface area> The BET specific surface area was calculated by the following method. Using a specific surface area measuring device "BELSORP-miniII" manufactured by MicrotracBEL Co., Ltd., the adsorption / desorption isotherm was measured by the constant volume gas adsorption method, and the BET specific surface area was calculated by the multi-point method. The pretreatment was carried out at 120 °C for 30 minutes or more under a reduced pressure environment. He was used as the purge gas and N2 was used as the adsorbate.

[0117] <True density> Using a true density evaluation device "BELPycno" manufactured by MicrotracBEL Co., Ltd., the true density was calculated by the gas displacement method. The pretreatment was carried out 5 times by purging. For the measurement, an alumina 10 cm 3 cell was used, and the sample was filled up to about 70% of the cell.

[0118] <CS value> D 10 、D 50 and D 95 In the same manner as the measurement of D

[0119] <Comparative Example 1> The composition is Li 5.4 PS 4.4 Cl 0.8 Br 0.8 and the total amount is 5 g. Lithium sulfide powder, phosphorus pentasulfide powder, lithium chloride powder and lithium bromide powder were weighed respectively, and pulverized and mixed with a ball mill for 15 hours to obtain raw material powder. The characteristics (D 50 and D 95 ) of the obtained raw material powder were evaluated. The D 50 and D 95 of the raw material powder were 4.58 μm and 16.55 μm respectively. The D 50 and D 95The measurement was carried out in the same manner as above, except that a measurement sample containing raw material powder was used. The measurement sample containing raw material powder was prepared as follows. The raw material powder was pulverized and mixed in toluene using a ball mill for 15 hours to obtain a raw material slurry. Next, a few drops of a dispersant (SN Dispersant 9228 manufactured by San Nopco Ltd.) were added to an organic solvent (toluene), and then a few drops of the slurry containing the raw material powder were added to prepare a measurement sample containing raw material powder.

[0120] The obtained raw material powder was packed into a carbon container and then heat-treated in a tubular electric furnace at 300°C for 4 hours with a temperature increase / decrease rate of 200°C / hour while hydrogen sulfide gas was circulated at 1.0 L / min, followed by heat-treatment at 500°C for 4 hours.

[0121] The obtained heat-treated body (sintered body) was pulverized to obtain a pulverized body (sulfide solid electrolyte of Comparative Example 1). The pulverization was carried out in two stages using a planetary ball mill (manufactured by Fritsch). The first stage of pulverization was carried out using a planetary ball mill (manufactured by Fritsch). The capacity was 80 cm 3 5 g of the sulfide solid electrolyte (heat-treated body), 10 g of dehydrated heptane, and 90 g of 5 mm ZrO2 balls were placed in a zirconia container and pulverized for 3 hours at a rotation speed of 100 rpm. The resulting slurry was dried in vacuum to obtain the first-stage pulverized body. The obtained first-stage pulverized body was used to perform the second-stage pulverization. In the second-stage pulverization, a 80 cm3 container was used. 3 2 g of the sulfide solid electrolyte (first-stage crushed body), 0.06 g of a dispersant (butyl acetate), 10 g of ultra-dehydrated toluene, and 90 g of 0.8 mm ZrO2 balls were placed in a zirconia container and crushed at 100 rpm for 1 hour. The resulting slurry was subjected to ball separation and solid-liquid separation, vacuum dried at 80°C, and then sized through a sieve with 53 μm openings to obtain the sulfide solid electrolyte of Comparative Example 1.

[0122] All of the weighing, mixing, setting in the electric furnace, removing from the electric furnace, pulverizing and sieving operations were carried out in a glove box filled with sufficiently dried Ar gas (dew point -60°C or lower).

[0123] The evaluation results of the obtained sulfide solid electrolyte are shown in Table 1A and FIG.

[0124] As shown in FIG. 4, the sulfide solid electrolyte had a peak derived from the second crystalline phase but no peak derived from the first crystalline phase in the X-ray diffraction pattern measured using CuKα1 radiation.

[0125] Example 1 The sulfide solid electrolyte of Comparative Example 1 was used as a raw material for the sulfide solid electrolyte of Example 1. The sulfide solid electrolyte of Comparative Example 1 was heat-treated at 270°C for 2 hours in an environment where argon gas was flowed at a flow rate of 1 L / min, to obtain a heat-treated body (the sulfide solid electrolyte of Example 1).

[0126] The evaluation results of the obtained sulfide solid electrolyte are shown in Table 1A and FIG.

[0127] As shown in FIG. 4, the sulfide solid electrolyte had peaks derived from the first crystalline phase and the second crystalline phase.

[0128] <Example 2> The same operations as in Example 1 were carried out, except that the heat treatment temperature for the solid electrolyte was changed to 300° C. The evaluation results are shown in Table 1A and FIG.

[0129] As shown in FIG. 4, the sulfide solid electrolyte had peaks derived from the first crystalline phase and the second crystalline phase.

[0130] Example 3 The same operations as in Example 1 were carried out, except that the heat treatment temperature for the sulfide solid electrolyte was changed to 350° C. The evaluation results are shown in Table 1B and FIG.

[0131] As shown in FIG. 4, the sulfide solid electrolyte had peaks derived from the first crystalline phase and the second crystalline phase.

[0132] Example 4 Capacity 80cm 32 g of the sulfide solid electrolyte obtained in Example 3, 0.06 g of a dispersant (butyl acetate), 10 g of ultra-dehydrated toluene, and 90 g of 0.8 mm ZrO2 balls were placed in a zirconia container and pulverized at 100 rpm for 10 minutes. The resulting slurry was subjected to ball separation and solid-liquid separation, vacuum dried at 80°C, and then sieved through a sieve with 53 μm openings to obtain the sulfide solid electrolyte of Example 4. The evaluation results are shown in Table 1B and FIG. 4.

[0133] As shown in FIG. 4, the sulfide solid electrolyte had peaks derived from the first crystalline phase and the second crystalline phase.

[0134] <Example 5> The same operations as in Comparative Example 1 were carried out, except that the raw material powder was heat-treated in an H2S atmosphere at 300°C for 8 hours and the heat-treated body was not subjected to the second stage of pulverization. The evaluation results are shown in Table 1B and Figure 4.

[0135] As shown in FIG. 4, the sulfide solid electrolyte had peaks derived from the first crystalline phase and the second crystalline phase.

[0136] [Table 1A]

[0137] [Table 1B]

[0138] As shown in Table 1, in Examples 1 to 5, a sulfide solid electrolyte containing Li, P, and S, which had a peak due to the first crystalline phase in the X-ray diffraction pattern, was obtained.

[0139] In the X-ray diffraction pattern shown in FIG. 4, the peaks at 2θ=19.5±1.00°, 23.2±1.00°, and 29.2±0.500°, which are derived from the first crystalline phase, are referred to as "Peak P1," "Peak P2," and "Peak P3," respectively, and the peak at 2θ=29.62°±1.00°, which is the peak with the greatest intensity among the peaks derived from the second crystalline phase, is referred to as "Peak P2." A ", the peak P A The percentage of the intensity of peak P1 relative to the intensity of peak P1 (peak P1 intensity / peak P A intensity × 100), peak P A The percentage of the intensity of peak P2 relative to the intensity of peak P (intensity of peak P2 / peak P A intensity × 100), and peak P A The percentage of the intensity of peak P3 relative to the intensity of peak P (Intensity of peak P3 / Intensity of peak P A The strength of the sample (strength of sample × 100) was as shown in Tables 2 to 4.

[0140] [Table 2]

[0141] [Table 3]

[0142] [Table 4]

Claims

1. containing lithium (Li), phosphorus (P), and sulfur (S) elements; A sulfide solid electrolyte, having peaks at 2θ = 23.2° ± 1.0° and 2θ = 29.2° ± 0.5° in an X-ray diffraction pattern measured using CuKα1 radiation, the peaks being attributable to a crystalline phase having a crystalline structure belonging to the space group Pmna.

2. 2. The sulfide solid electrolyte according to claim 1, wherein the X-ray diffraction pattern measured using CuKα1 radiation has peaks at 2θ = 19.5 ° ± 1.0 ° and 2θ = 30.5 ° ± 0.5 ° at positions attributable to a crystalline phase having a crystalline structure belonging to the space group Pmna.

3. 3. The sulfide solid electrolyte according to claim 1, wherein the X-ray diffraction pattern measured using CuKα1 radiation has peaks at 2θ = 15.34° ± 1.00° and 2θ = 25.19° ± 1.00°, which are attributable to a crystalline phase having an argyrodite-type crystal structure.

4. 3 m ２ / g or more 11m ２ The sulfide solid electrolyte according to any one of claims 1 to 3, having a BET specific surface area of ​​0.1g or less.

5. The following formula: Li ａ PS ｂ X ｃ [In the formula, X is at least one halogen element, a is 3.0 or more and 6.5 or less, b is 3.5 or more and 5.5 or less, and c is 0.50 or more and 3.0 or less.] The sulfide solid electrolyte according to any one of claims 1 to 4, having a composition represented by the formula:

6. The sulfide solid electrolyte according to claim 5, wherein the halogen (X) element is at least one of a chlorine (Cl) element and a bromine (Br) element.

7. An electrode mixture comprising the sulfide solid electrolyte according to any one of claims 1 to 6 and an active material.

8. A slurry comprising the sulfide solid electrolyte according to any one of claims 1 to 6 and a dispersion medium.

9. a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer; A battery, wherein the solid electrolyte layer comprises the sulfide solid electrolyte according to any one of claims 1 to 6.

10. The following steps: (1) preparing a sulfide solid electrolyte material containing lithium (Li), phosphorus (P), and sulfur (S) as an intermediate; and (2) A step of heat-treating the intermediate to obtain the sulfide solid electrolyte according to any one of claims 1 to 6. A method for producing a sulfide solid electrolyte, comprising:

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