Method for producing sulfide solid electrolyte

Abstract

To provide a method for producing a sulfide solid electrolyte which is formed into fine particles, and in which generation of hydrogen sulfide when exposed to an atmosphere containing moisture is suppressed.SOLUTION: A method for producing a sulfide solid electrolyte having an LGPS type crystal phase which contains Li element, Sn element, P element and S element has: an amorphization step of making a raw material composition become amorphous to obtain an ion-conductive material; a first heating step of heating an ion-conductive material in inert gas airflow to obtain a sulfide solid electrolyte intermediate; a fine particles forming step of pulverizing the sulfide solid electrolyte intermediate into fine particle to obtain a fine particle intermediate; and a second heating step of heating the fine particle intermediate in the inert gas airflow at the temperature of 300°C or higher and 450°C or lower to obtain a sulfide solid electrolyte.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a sulfide solid electrolyte. [Background technology]

[0002] All-solid-state batteries are batteries that have a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and have the advantage of being easier to simplify safety devices compared to liquid-based batteries that use electrolytes containing flammable organic solvents. Sulfide solid electrolytes are known as solid electrolytes used in all-solid-state batteries.

[0003] For example, Patent Document 1 discloses a sulfide solid electrolyte containing an M1 element (e.g., Li), an M2 element (e.g., Ge and P), and an S element, which has a peak at a predetermined position in X-ray diffraction measurement. Patent Document 2 also discloses a sulfide solid electrolyte containing an M1 element (e.g., Li), an M2 element (e.g., Sn and P), and an S element, which has a peak at a predetermined position in X-ray diffraction measurement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5527673 [Patent Document 2] International Publication No. 2013 / 118722 Summary of the Invention [Problem to be solved by the invention]

[0005] Sulfide solid electrolytes used in batteries are required to exhibit high dispersibility within the electrode to reduce the resistance of the battery, and for this reason, they are microparticulated. However, when sulfide solid electrolytes are pulverized into microparticulates, their crystallinity decreases, which can lead to reduced water resistance. As a result, hydrogen sulfide (H2S) can be generated when exposed to a moist atmosphere.

[0006] The present disclosure has been made in view of the above-described circumstances, and aims to provide a method for producing a sulfide solid electrolyte that is microparticulated and that suppresses the generation of hydrogen sulfide (HS) when exposed to a moisture-containing atmosphere. [Means for solving the problem]

[0007] <1> A method for producing a sulfide solid electrolyte having an LGPS-type crystalline phase containing Li, Sn, P, and S elements, an amorphization step of amorphizing the raw material composition to obtain an ion-conductive material; a first heating step of heating the ion-conductive material in an inert gas flow to obtain a sulfide solid electrolyte intermediate; a microparticulation step of pulverizing the sulfide solid electrolyte intermediate to obtain a microparticle intermediate; a second heating step of heating the fine particle intermediate in an inert gas flow at a temperature of 300°C or higher and 450°C or lower to obtain a sulfide solid electrolyte; A method for producing a sulfide solid electrolyte comprising the steps of: <2> The raw material composition contains Li 4-x Sn 1-x P x S4 (0.55≦x≦0.76) <1> 10. A method for producing the sulfide solid electrolyte according to claim 9. <3> The sulfide solid electrolyte has an average particle size of 1.0 μm or less. <1> or <2> 10. A method for producing the sulfide solid electrolyte according to claim 9. <4> The sulfide solid electrolyte has a half-width of a peak at 2θ=26.70±0.50° in X-ray diffraction measurement of 0.73 or less. <1> ~ <3> 10. A method for producing the sulfide solid electrolyte according to claim 9. [Effects of the Invention]

[0008] According to the present disclosure, a method for producing a sulfide solid electrolyte that is microparticulated and suppresses the generation of hydrogen sulfide (H2S) when exposed to a moisture-containing atmosphere is provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a flow diagram illustrating a method for producing a sulfide solid electrolyte according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a perspective view illustrating an example of a crystal structure of a sulfide solid electrolyte material according to the present disclosure. [Figure 3] FIG. 1 is a schematic cross-sectional view illustrating a battery to which a sulfide solid electrolyte obtained by a manufacturing method according to an embodiment of the present disclosure can be applied. [Figure 4] 1 is a graph showing the results of X-ray diffraction measurement of sulfide solid electrolytes of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for producing the sulfide solid electrolyte of the present disclosure will be described in detail below.

[0011] <Method for producing sulfide solid electrolyte> 1 is a flow diagram illustrating a method for producing a sulfide solid electrolyte according to an embodiment of the present disclosure. As shown in FIG. 1, the method for producing a sulfide solid electrolyte includes the following steps to produce a sulfide solid electrolyte having an LGPS-type crystalline phase containing Li, Sn, P, and S. (1) Amorphization step of amorphizing the raw material composition to obtain an ion-conductive material (2) A first heating step in which an ion-conductive material is heated in an inert gas flow to obtain a sulfide solid electrolyte intermediate (hereinafter also simply referred to as "intermediate"). (3) A micronization step in which the intermediate is pulverized to obtain a micronized intermediate. (4) A second heating step in which the fine particle intermediate is heated in an inert gas flow at a temperature of 300°C to 450°C to obtain a sulfide solid electrolyte.

[0012] According to the method for producing a sulfide solid electrolyte according to an embodiment of the present disclosure, by going through the above steps, it is possible to obtain a sulfide solid electrolyte that is microparticulated and that suppresses the generation of hydrogen sulfide (HS) when exposed to a moisture-containing atmosphere. The reason for this effect is presumed to be as follows.

[0013] Sulfide solid electrolytes used in batteries are required to exhibit high dispersibility within the electrode to reduce the resistance of the battery. Therefore, to achieve high dispersibility, sulfide solid electrolytes are microparticulated. However, when the obtained sulfide solid electrolyte is further pulverized into microparticulates during the production process of sulfide solid electrolytes, the crystallinity of the sulfide solid electrolyte can be reduced. Sulfide solid electrolytes with reduced crystallinity have reduced water resistance and, for example, when exposed to a humid atmosphere, react with moisture to generate hydrogen sulfide (HS).

[0014] In contrast, the method for producing a sulfide solid electrolyte according to an embodiment of the present disclosure includes a second heating step of heating (firing) the sulfide solid electrolyte intermediate at a temperature in the range of 300°C to 450°C after the microparticulation step of pulverizing the sulfide solid electrolyte intermediate into microparticulates. Further heating at this temperature can improve the crystallinity of the microparticulated sulfide solid electrolyte and enhance its water resistance. As a result, it is believed that the generation of hydrogen sulfide (HS) can be suppressed even when the sulfide solid electrolyte is exposed to a moisture-containing atmosphere.

[0015] (0) Raw material composition In the method for producing a sulfide solid electrolyte, first, a raw material composition is prepared. The raw material composition contains Li, Sn, P, and S elements. The raw material composition is preferably a mixture containing a Li source, a Sn source, a P source, and an S source. Examples of the Li source include sulfides containing Li. Examples of sulfides containing Li include Li2S. Examples of the Sn source include simple Sn and sulfides containing Sn. Examples of sulfides containing Sn include SnS2. Examples of the P source include simple P and sulfides containing P. Examples of sulfides containing P include P2S5. Examples of the S source include simple S, sulfides containing Li, sulfides containing Sn, and sulfides containing P.

[0016] For example, a raw material composition can be prepared by mixing Li2S, SnS2, and P2S5. In order to prevent the raw material composition from being deteriorated by moisture in the air, it is preferable to prepare the raw material composition under an inert gas (e.g., Ar gas, He gas) atmosphere.

[0017] The raw material composition is Li 4-x Sn 1-x P x It is preferable that the composition be represented by S4 (0.55≦x≦0.76). From the viewpoint of forming a single composition, x is preferably in the range of 0.55 or more and 0.76 or less. Furthermore, the lower limit of x is more preferably 0.57 or more, even more preferably 0.59 or more, even more preferably 0.61 or more, and even more preferably 0.63 or more. The upper limit of x is more preferably 0.74 or less, even more preferably 0.72 or less.

[0018] (1) Amorphization process The amorphization step is a step of obtaining an ion-conductive material by amorphizing the raw material composition.

[0019] The method for amorphizing the raw material composition is not particularly limited, but examples thereof include mechanical milling and melt quenching. In mechanical milling, the raw material composition is pulverized while applying mechanical energy. Examples of mechanical milling include a ball mill, a vibration mill, a turbo mill, and a disk mill. The amorphization conditions are appropriately set so as to obtain the desired ion-conductive material.

[0020] When a planetary ball mill is used, the rotation speed of the table is, for example, preferably 200 rpm (revolutions per minute) to 600 rpm, more preferably 250 rpm to 350 rpm, and the treatment time in the planetary ball mill is, for example, preferably 1 hour to 100 hours, more preferably 5 hours to 70 hours. When using a vibration mill, the vibration amplitude is, for example, preferably 5 mm to 15 mm, more preferably 6 mm to 10 mm. The vibration frequency of the vibration mill is, for example, preferably 500 rpm to 2000 rpm, more preferably 1000 rpm to 1800 rpm. It is also preferable to use a vibrator (e.g., an alumina vibrator) for the vibration mill. The processing time in the vibration mill is, for example, preferably 1 hour to 100 hours, more preferably 5 hours to 70 hours.

[0021] In order to prevent the ion-conductive material from being deteriorated by moisture in the air, it is preferable to carry out the amorphization step in an inert gas (for example, Ar gas, He gas) atmosphere.

[0022] (2) First heating step The first heating step is a step of heating the ion-conductive material in an inert gas flow to obtain a sulfide solid electrolyte intermediate (intermediate). By heating the amorphous ion-conductive material, it is possible to improve the crystallinity.

[0023] Examples of inert gases include rare gases such as argon (Ar) and helium (He). The inert gas may contain other gases as long as the desired intermediate is obtained. The flow rate of the inert gas is not particularly limited and may be appropriately set so as to obtain the desired intermediate.

[0024] The heating conditions in the first heating step are also appropriately set so as to obtain a desired intermediate. The heating temperature is, for example, preferably 300°C or higher, more preferably 400°C or higher, and even more preferably 500°C or higher. On the other hand, the upper limit of the heating temperature is, for example, preferably 1000°C or lower, more preferably 700°C or lower, and even more preferably 600°C or lower. The heating time is suitably set so as to obtain a desired intermediate, and is, for example, preferably from 1 hour to 20 hours, more preferably from 2 hours to 10 hours, and even more preferably from 3 hours to 8 hours. It is preferable to raise the temperature to the above heating temperature over a long period of time, for example, preferably from 5 hours to 20 hours, more preferably from 7 hours to 15 hours. The heating device used for heating may be, for example, a gas flow furnace or a baking furnace.

[0025] (3) Micronization process The microparticulation step is a step of microparticulating a sulfide solid electrolyte intermediate (intermediate) to obtain a microparticle intermediate.

[0026] The method for microparticulating the intermediate is not particularly limited, and the same method as that used in the amorphization step can be used, such as mechanical milling and melt quenching. Examples of mechanical milling include ball mills, vibration mills, turbo mills, and disk mills. The microparticulation conditions are appropriately set so as to obtain the desired ion-conductive material.

[0027] When a planetary ball mill is used in the microparticulation step, the rotation speed of the table is, for example, preferably 50 rpm to 600 rpm, more preferably 100 rpm to 400 rpm, and the treatment time in the planetary ball mill is, for example, preferably 0.1 hours to 10 hours, more preferably 0.5 hours to 5 hours, and even more preferably 1 hour to 2 hours.

[0028] In order to prevent the intermediate from being deteriorated by moisture in the air, it is preferable to carry out the microparticulation step in an inert gas (for example, Ar gas, He gas) atmosphere.

[0029] (4) Second heating step The second heating step is a step of heating the fine particle intermediate in an inert gas flow at a temperature of 300°C to 450°C to obtain a sulfide solid electrolyte. By further heating the fine particle intermediate, it is possible to improve the crystallinity.

[0030] The inert gas may be the same as that used in the first heating step, and examples thereof include rare gases such as argon (Ar) and helium (He). The inert gas may contain other gases as long as the desired sulfide solid electrolyte is obtained. The flow rate of the inert gas is not particularly limited and may be appropriately set so as to obtain the desired sulfide solid electrolyte.

[0031] The heating temperature in the second heating step is 300°C or higher and 450°C or lower. If the heating temperature is lower than 300°C, the crystallinity of the sulfide solid electrolyte cannot be improved, and the generation of hydrogen sulfide (HS) cannot be suppressed when the resulting sulfide solid electrolyte is exposed to a moisture-containing atmosphere. If the heating temperature is higher than 450°C, the generation of hydrogen sulfide (HS) cannot be suppressed when the resulting sulfide solid electrolyte is exposed to a moisture-containing atmosphere. The heating temperature is preferably 320°C or higher and 430°C or lower, and more preferably 350°C or higher and 400°C or lower.

[0032] The heating time is appropriately set so as to obtain a desired sulfide solid electrolyte, and is, for example, preferably from 1 hour to 20 hours, more preferably from 2 hours to 10 hours, and even more preferably from 3 hours to 8 hours. It is preferable to raise the temperature to the above heating temperature over a long period of time, for example, preferably from 5 hours to 20 hours, more preferably from 7 hours to 15 hours. As the heating device used for heating, the devices listed in the section for the first heating step can be used in the same manner.

[0033] (5) Sulfide solid electrolyte The sulfide solid electrolyte obtained by the above-described manufacturing method has an LGPS-type crystalline phase containing elements Li, Sn, P, and S. This sulfide solid electrolyte is microparticulated, and when exposed to an atmosphere containing moisture, the generation of hydrogen sulfide (HS) is suppressed.

[0034] LGPS-type crystal phase peak The sulfide solid electrolyte having an LGPS-type crystalline phase obtained by the above-mentioned manufacturing method has a peak at 2θ=29.31°±0.50° in X-ray diffraction measurement using CuKα radiation, and does not have a peak at 2θ=27.33°±0.50° in X-ray diffraction measurement using CuKα radiation, or if it has a peak at 2θ=27.33°±0.50°, the diffraction intensity of the peak at 2θ=29.31°±0.50° is I A The diffraction intensity of the peak at 2θ=27.33°±0.50° is defined as I B When I B / I A It is preferable that the value of is less than 1.00. The peak near 2θ=29.31° is one of the peaks of a crystalline phase with high ionic conductivity, while the peak near 2θ=27.33° is one of the peaks of a crystalline phase with low ionic conductivity. From the viewpoint of ionic conductivity, I B / I A The value of is preferably small, more preferably 0.50 or less, 0.45 or less, 0.25 or less, 0.15 or less, or 0.07 or less. B / IA 0, that is, it is preferable that there is no peak near 2θ=27.33°.

[0035] The peak at 2θ=29.31° in sulfide solid electrolyte materials is an actual measured value, and the crystal lattice may change slightly depending on the material composition, etc., and the peak position may vary slightly from 2θ=29.31°. Therefore, the above peak is defined as a peak at a position of 29.31°±0.50°. Crystalline phases are generally considered to have peaks at 2θ=20.00°, 20.31°, 26.70°, and 29.31°. Note that these peak positions may also vary within a range of ±0.50°. X-ray diffraction measurements (XRD) of sulfide solid electrolytes are performed on powder samples under conditions of an inert atmosphere and CuKα radiation.

[0036] ·LGPS-type crystal phase structure The sulfide solid electrolyte having an LGPS-type crystal phase obtained by the above-described manufacturing method preferably mainly comprises a crystal structure in which an octahedron O composed of Li and S, a tetrahedron T1 composed of Sn or P and S, and a tetrahedron T2 composed of P and S, wherein the tetrahedron T1 and the octahedron O share edges, and the tetrahedron T2 and the octahedron O share vertices. Because the octahedron O, the tetrahedron T1, and the tetrahedron T2 have a predetermined crystal structure (three-dimensional structure), the sulfide solid electrolyte material exhibits good ionic conductivity. It is believed that high ionic conductivity is achieved by metal ions (e.g., Li ions) passing through the spaces in this crystal structure.

[0037] FIG. 2 is a perspective view illustrating an example of the crystal structure of a sulfide solid electrolyte material having an LGPS-type crystal phase. In the crystal structure shown in FIG. 2, the octahedron O has Li as the central element and six S atoms at the vertices of the octahedron, and is typically a LiS6 octahedron. The tetrahedron T1 has Sn or P as the central element and four S atoms at the vertices of the tetrahedron, and is typically both a SnS4 tetrahedron and a PS4 tetrahedron. The tetrahedron T2 has P as the central element and four S atoms at the vertices of the tetrahedron, and is typically a PS4 tetrahedron. Furthermore, the tetrahedron T1 and the octahedron O share an edge, and the tetrahedron T2 and the octahedron O share a vertex. The crystal structure of sulfide solid electrolyte materials is identified by X-ray structural analysis. The crystal system and crystal group are determined by direct methods based on the diffraction pattern obtained by XRD, and then the crystal structure is identified by real-space methods.

[0038] ·Particle size The obtained sulfide solid electrolyte preferably has an average particle size of 1.0 μm or less, more preferably 0.9 μm or less, and even more preferably 0.8 μm or less, while the lower limit of the average particle size is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more.

[0039] The average particle size of the sulfide solid electrolyte is the average primary particle size measured by the laser diffraction method. The specific measurement procedure is as follows. The average particle size is measured by laser diffraction using a Malvern Mastersizer 200 and calculated from the volume-based average particle size. Specifically, a Malvern Instruments Ltd. Mastersizer 2000 is used as the measurement device. 110 ml of dehydrated toluene (Fujifilm Wako Pure Chemical Industries, Ltd., product name: special grade) is placed in the device's dispersion tank, and 6 mass% of dehydrated tertiary butyl alcohol (Fujifilm Wako Pure Chemical Industries, Ltd., special grade) is added as a dispersant. After thoroughly mixing the mixture, a sulfide solid electrolyte is added and the particle size is measured.

[0040] Half width As an index of crystallinity in the sulfide solid electrolyte, the half-width of the peak at 2θ=26.70±0.50° measured by X-ray diffraction (XRD) is preferably 0.73 or less, more preferably 0.70 or less, more preferably 0.65 or less, and even more preferably 0.60 or less.

[0041] The half-width is calculated by performing structural analysis of the obtained sulfide solid electrolyte by X-ray diffraction (XRD) and calculating the half-width of the main peak (2θ=26.70±0.50°) by Gaussian fitting.

[0042] ·composition The obtained sulfide solid electrolyte is Li 4-x Sn 1-x P x It is preferable that the composition be represented by S4 (0.55≦x≦0.76). From the viewpoint of forming a single composition, x is preferably in the range of 0.55 or more and 0.76 or less. Furthermore, the lower limit of x is more preferably 0.57 or more, even more preferably 0.59 or more, even more preferably 0.61 or more, and even more preferably 0.63 or more. The upper limit of x is more preferably 0.74 or less, even more preferably 0.72 or less.

[0043] Ionic conductivity The obtained sulfide solid electrolyte preferably has high Li-ion conductivity. The ionic conductivity (25°C) of the sulfide solid electrolyte is, for example, preferably 1.00 mS / cm or more, more preferably 1.30 mS / cm or more, and even more preferably 1.50 mS / cm or more, from the viewpoint of improving charge / discharge performance when used in a battery.

[0044] ·Applications The obtained sulfide solid electrolyte can be used in any application requiring ionic conductivity, and is particularly suitable for use in batteries.

[0045] FIG. 3 is a schematic cross-sectional view illustrating a battery to which a sulfide solid electrolyte obtained by a manufacturing method according to an embodiment of the present disclosure (hereinafter also simply referred to as the "sulfide solid electrolyte of the present disclosure") can be applied. The battery 10 in FIG. 3 includes a positive electrode layer 1 containing a positive electrode active material, a negative electrode layer 2 containing a negative electrode active material, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, a negative electrode current collector 5 that collects current from the negative electrode layer 2, and an exterior body 6 that houses these components. In the present disclosure, the sulfide solid electrolyte of the present disclosure can be applied to at least one of the positive electrode layer 1, the negative electrode layer 2, and the electrolyte layer 3. [Example]

[0046] The present disclosure will be explained in more detail below with reference to examples.

[0047] [Example 1] The starting materials used were lithium sulfide (LiS, manufactured by Nippon Chemical Industry Co., Ltd.), diphosphorus pentasulfide (P2S5, manufactured by Aldrich), and tin sulfide (SnS2, manufactured by Kojundo Chemical Co., Ltd.). These powders were mixed in a glove box under an argon atmosphere. 4-x Sn 1-x P x The components were weighed so that x in S4 was 0.70, and mixed in an agate mortar to obtain a raw material composition.

[0048] Next, the obtained raw material composition and crushing balls (zirconia balls) were placed in a container (zirconia pot) in a glove box under an argon atmosphere, and the container was sealed. At this time, the volume of the crushing balls added was adjusted to about 1 / 6 of the volume of the container, and the mass of the added raw material composition was adjusted to about 1 / 50 of the mass of the crushing balls. This container was attached to a planetary ball mill (P7 manufactured by Fritsch), and mechanical milling was performed for 20 hours at a table rotation speed of 300 rpm (amorphization process). As a result, an ion-conductive material was obtained.

[0049] Next, the obtained ion-conductive material was placed on a graphite boat and heated in an Ar gas flow. The heating conditions were that the temperature was raised from room temperature to 570°C over a 10-hour period, and then the temperature was maintained at 570°C for 6 hours, followed by slow cooling to room temperature (first heating step). This resulted in a sulfide solid electrolyte intermediate.

[0050] Next, the sulfide solid electrolyte intermediate and crushing balls (zirconia balls) were placed in a container (zirconia pot) in a glove box under an argon atmosphere, and the container was sealed. At this time, the volume of the crushing balls added was adjusted to about 1 / 6 of the volume of the container, and the mass of the raw material composition added was adjusted to about 1 / 50 of the mass of the crushing balls. This container was attached to a planetary ball mill (P7 manufactured by Fritsch), and mechanical milling was performed for 1.5 hours at a table rotation speed of 250 rpm (microparticulation process). This resulted in a microparticle intermediate.

[0051] Next, the obtained fine particle intermediate was placed on a graphite boat and heated in an Ar gas flow. The heating conditions were that the temperature was raised from room temperature to 300°C in 2 hours, and the heating temperature was maintained at 300°C for 6 hours, and then the intermediate was gradually cooled to room temperature (second heating step). 4-x Sn 1-x P x A sulfide solid electrolyte having a composition represented by S4 where x=0.70 was obtained.

[0052] [Example 2] A sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the heating temperature in the second heating step was changed to the temperature shown in Table 1.

[0053] [Comparative Example 1] A sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the second heating step was not carried out and the particles at the time of carrying out the microparticulation step were used as the sulfide solid electrolyte.

[0054] [Comparative Examples 2 to 3] A sulfide solid electrolyte was obtained in the same manner as in Example 1, except that the heating temperature in the second heating step was changed to the temperature shown in Table 1.

[0055] -evaluation- (Measurement of H2S generation amount) Using the sulfide solid electrolytes obtained in the examples and comparative examples as samples, the amount of HS generated in an environment with a dew point of -30°C was measured. First, a 1-liter glass desiccator was placed in a dry-air glove box with a dew point of -30°C. 10 mg of sample was weighed and placed in an aluminum container, and the aluminum container containing the sample was then placed in the glass desiccator. With the fan running, the lid of the glass desiccator was closed, and the sample was exposed to the -30°C dew point environment for 5 hours. The amount of HS generated during this process was measured using a sensor (manufacturer: ToxiRAEPro, model number: 0-100 ppm, measurement mode: none), and the amount of HS generated per unit specific surface area (ppm) was calculated. The results are shown in Table 1.

[0056] (X-ray diffraction measurement) X-ray diffraction (XRD) measurements were performed on the sulfide solid electrolytes obtained in the examples and comparative examples. The XRD measurements were performed on powder samples in an inert atmosphere using CuKa radiation. The results are shown in Figure 4. Furthermore, the half-width of the main peak (2θ=26.70±0.50°) was calculated by Gaussian fitting. The results are shown in Table 1.

[0057] (Ionic conductivity measurement) 200 mg of the sulfide solid electrolyte obtained in the examples and comparative examples was weighed out and placed in a Macol cylinder. 2 The pellet was pressed at a pressure of 1000 kJ / cm. Both ends of the pellet were clamped with SUS pins and bolted to apply a confining pressure to the pellet. The ionic conductivity of the sample was calculated by the AC impedance method while the temperature was kept at 25°C. A Solartron 1260 was used for the measurement, with an applied voltage of 5 mV and a measurement frequency range of 0.01 MHz to 1 MHz. The results are shown in Table 1.

[0058] (Average particle size) The average particle size (average primary particle size) of the sulfide solid electrolytes obtained in the examples and comparative examples was measured by the method described above. The results are shown in Table 1.

[0059] [Table 1]

[0060] As shown in Table 1, in Examples 1 and 2, in which the second heating step was performed at a temperature of 300°C or higher and 450°C or lower, the half-width was in a low range of 0.73 or lower and the ionic conductivity was high, at 1.30 or higher, compared to Comparative Example 1, in which the second heating step was not performed, Comparative Example 2, in which the heating temperature in the second heating step was lower than 300°C, and Comparative Example 3, in which the heating temperature in the second heating step was higher than 450°C. Furthermore, the generation of hydrogen sulfide (HS) was suppressed in the Examples compared to the Comparative Examples. [Explanation of symbols]

[0061] 1 positive electrode layer, 2 negative electrode layer, 3 electrolyte layer, 4 positive electrode current collector, 5 negative electrode current collector, 6 exterior body, 10 battery

Claims

1. A method for producing a sulfide solid electrolyte having an LGPS-type crystalline phase containing Li, Sn, P, and S elements, an amorphization step of amorphizing the raw material composition to obtain an ion-conductive material; a first heating step of heating the ion-conductive material in an inert gas flow to obtain a sulfide solid electrolyte intermediate; a microparticulation step of pulverizing the sulfide solid electrolyte intermediate to obtain a microparticle intermediate; a second heating step of heating the fine particle intermediate at a temperature of 300°C or higher and 450°C or lower in an inert gas flow to obtain a sulfide solid electrolyte; A method for producing a sulfide solid electrolyte comprising the steps of:

2. The raw material composition comprises Li ４－ｘ Sn １－ｘ P ｘ S ４ The method for producing a sulfide solid electrolyte according to claim 1, having a composition represented by (0.55≦x≦0.76).

3. The method for producing a sulfide solid electrolyte according to claim 1 , wherein the sulfide solid electrolyte has an average particle size of 1.0 μm or less.

4. 2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the sulfide solid electrolyte has a half-width of a peak at 2θ=26.70±0.50° of 0.73 or less as measured by X-ray diffraction.

Images