Method for producing sulfide solid electrolyte, method for producing lithium ion secondary battery, and sulfide solid electrolyte

Abstract

The present invention relates to a method for producing a sulfide solid electrolyte, the method comprising, in order: heating starting materials, which respectively contain Li, P, and S, and a nitride that is represented by formula MαNβ so as to obtain a melt; and cooling the melt so as to precipitate a solid. The element represented by M is at least one element that is selected from the group consisting of group 2 to group 14 metal elements or metalloid elements in the periodic table, and α and β in the formula MαNβ respectively match the stoichiometric ratios of M and N in the nitride that is represented by the formula MαNβ.

Description

Sulfide solid electrolyte, method for manufacturing lithium ion secondary battery, and sulfide solid electrolyte

[0001] The present invention relates to a sulfide solid electrolyte, a method for producing a lithium ion secondary battery, and a sulfide solid electrolyte.

[0002] Lithium-ion secondary batteries are widely used in portable electronic devices such as mobile phones and laptop computers. While liquid electrolytes have traditionally been used in lithium-ion secondary batteries, solid-state lithium-ion secondary batteries, which use solid electrolytes as the electrolyte, have attracted attention due to their potential for improved safety, high-speed charging and discharging, and compact housings.

[0003] One example of a solid electrolyte used in all-solid-state lithium-ion secondary batteries is a sulfide solid electrolyte, which exhibits high lithium ion conductivity but is prone to generating hydrogen sulfide when in contact with water.

[0004] In response to this, Patent Document 1 discloses that the generation of hydrogen sulfide can be suppressed by using a crystalline material containing a predetermined proportion of N element. ２ S-25P ２ S ５ -yLi ３ A sulfide solid electrolyte, which is a crystalline material, is disclosed, having a composition represented by N(10≦y≦15, 67.5≦x+y≦85).

[0005] However, in order to obtain a sulfide solid electrolyte of the above composition, Li ３ When N is used, N is easily vaporized and discharged outside the system. ３ It is disclosed that a sulfide solid electrolyte in which the emission of N to the outside of the system is suppressed can be produced by reacting N with AlN to obtain a stable intermediate, mixing the intermediate with other raw materials, and then heating and firing the mixture.

[0006] Japanese Patent Application Publication No. 2018-041671 International Publication No. 2020 / 045634

[0007] However, Li ３Nitrogen is highly reactive and is classified as a dangerous substance that reacts with water to become flammable. Therefore, special care must be taken when handling it. ３ When N is used, if it is desired to suppress the volatilization of N, it is necessary to go through an intermediate as described in Patent Document 2, which increases the number of steps and reduces efficiency.

[0008] Therefore, the present invention uses Li as a N source. ３ An object of the present invention is to provide an efficient method for producing a sulfide solid electrolyte, which suppresses N volatilization without using N. Another object of the present invention is to provide a method for producing a lithium ion secondary battery using the sulfide solid electrolyte obtained by the above production method, and to provide a new sulfide solid electrolyte containing nitrogen as a constituent element.

[0009] Through investigations by the present inventors, it was found that the above-mentioned problems can be solved by employing a specific nitride as an N source and obtaining a sulfide solid electrolyte via melting raw materials, and this led to the completion of the present invention.

[0010] That is, the gist of the present invention is as follows: [1] A method for producing a sulfide solid electrolyte containing Li, P, M, S, and N, comprising: α N β and cooling the melt to precipitate a solid, wherein the element represented by M is at least one element selected from the group consisting of metal elements and semimetal elements of Groups 2 to 14 of the periodic table, and ... α N β In the formula M, α and β are α N β [2] The method for producing a sulfide solid electrolyte according to the above [1], wherein the sulfide solid electrolyte further contains Ha, and the raw materials further contain a raw material containing Ha, and the element represented by Ha is a halogen element. [3] The raw materials include Li, ２ S, P ２ S ５and at least one selected from the group consisting of LiCl, LiBr, and LiI. [4] The method for producing a sulfide solid electrolyte according to the above [2] or [3], wherein the Ha includes at least one of Br and I. [5] The method for producing a sulfide solid electrolyte according to any one of the above [1] to [4], wherein the element represented by M is at least one selected from the group consisting of Si, Al, and B. [6] The method for producing a sulfide solid electrolyte according to the above [1] to [4], wherein the element represented by the formula M α N β The nitride represented by Si ３ N ４ [7] The method for producing a sulfide solid electrolyte according to any one of [1] to [5], comprising: α N β The nitride represented by the formula has a specific surface area of ​​30 m ２[8] The method for producing a sulfide solid electrolyte according to any one of [1] to [6], wherein the sulfide solid electrolyte is a powder having a solubility of 1 / g or more. [9] The method for producing a sulfide solid electrolyte according to any one of [1] to [8], wherein the heat treatment is carried out in a gas atmosphere containing S.

[10] The method for producing a sulfide solid electrolyte according to any one of [1] to [9], wherein the heat treatment is carried out at a temperature of 650 to 850°C.

[11] The method for producing a sulfide solid electrolyte according to any one of [1] to

[10] , wherein the heat treatment is carried out for 10 to 600 minutes.

[12] The method for producing a sulfide solid electrolyte according to any one of [1] to

[11] , wherein the heat treatment is carried out in an atmosphere having a dew point of -20°C or lower.

[13] The method for producing a sulfide solid electrolyte according to any one of [1] to

[12] , wherein the heat treatment is carried out in an atmosphere having an oxygen concentration of 1,000 ppm by volume or less.

[14] The method for producing a sulfide solid electrolyte according to any one of [1] to

[13] , wherein the cooling is carried out at a cooling rate of 1,000 to 100,000°C / sec.

[15] The method for producing a sulfide solid electrolyte according to any one of [1] to

[14] , further comprising, after precipitating the solid, performing a post-heat treatment by heating.

[16] The method for producing a sulfide solid electrolyte according to

[15] , wherein the post-heat treatment is carried out at 150 to 400°C.

[17] The method for producing a sulfide solid electrolyte according to

[15] or

[16] , wherein the post-heat treatment is carried out in an atmosphere having a dew point of -20°C or less.

[18] The method for producing a sulfide solid electrolyte according to any one of

[15] to

[17] , wherein the post-heat treatment is carried out in an atmosphere having an oxygen concentration of 1000 volume ppm or less.

[19] The method for producing a sulfide solid electrolyte according to any one of [1] to

[18] , wherein the lithium ion conductivity at 25°C is 1 mS / cm or more.

[0011]

[20] A sulfide solid electrolyte containing Li, P, S, Si, and N as constituent elements, wherein, among the constituent elements, the sulfide solid electrolyte has a content ratio expressed as b / d, where the content ratio of P is 1, the content ratio of Si is b, and the content ratio of N is d, in atomic ratio, of the constituent elements, and the ratio is 0.5 to 1.

[21] The sulfide solid electrolyte according to

[20] , further containing Ha as a constituent element, wherein the element expressed as Ha is a halogen element.

[22] The sulfide solid electrolyte has a composition formula: Li ａ PSi ｂ S ｃ N ｄ Ha ｅ The sulfide solid electrolyte according to

[20] or

[21] , wherein the element represented by Ha is Br and I, and the sulfide solid electrolyte has a composition formula: Li ａ PSi ｂ S ｃ N ｄ Br ｅ１ I ｅ２ The sulfide solid electrolyte according to

[21] , which is represented by the following formula: 3.00≦a≦3.60, 0.07≦b≦0.35, 3.40≦c≦3.80, 0.09≦d≦0.47, 0.30≦e1≦0.34, and 0.19≦e2≦0.23.

[0012] According to the present invention, Li is used as a N source. ３ The desired sulfide solid electrolyte can be efficiently produced with a reduced number of steps without using N and while suppressing the volatilization of N. The obtained sulfide solid electrolyte can achieve high lithium ion conductivity and good water resistance due to the introduction of nitrogen element.

[0013] Fig. 1 is a flow diagram showing one aspect of a method for producing a sulfide solid electrolyte according to this embodiment. Fig. 2 is a flow diagram showing one aspect of a method for producing a sulfide solid electrolyte according to this embodiment. Fig. 3 is a flow diagram showing one aspect of a method for producing a sulfide solid electrolyte according to this embodiment. Fig. 4 is an XRD pattern of the solid obtained in Example 5. Fig. 5 is a DSC curve of the solids obtained in Examples 5 and 6.

[0014] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be implemented with any modifications within the scope of the present invention. The term "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0015] <<Method for Producing Sulfide Solid Electrolyte>> The production method according to this embodiment is a method for producing a sulfide solid electrolyte containing Li, P, M, S, and N, and includes the following steps in order, as shown in FIG. 1 : Step S1: Raw materials containing Li, P, and S, and a sulfide solid electrolyte of formula M α N β Step S2: A step of cooling the melt obtained in step S1 to precipitate a solid. Here, the element represented by M is at least one element selected from the group consisting of metal elements or metalloid elements of groups 2 to 14 of the periodic table. α N β where α and β are the formula M α N β This corresponds to the stoichiometric ratio of M and N in the nitride represented by the formula:

[0016] Step S1 may include the following steps S1a and S1b, as shown in FIG. 2: Step S1a: Adding raw materials including Li, P, and S, and a compound represented by the formula M α N β Step S1b: A step of heat-treating the raw material mixture obtained in step S1a to obtain a melt.

[0017] The obtained sulfide solid electrolyte may further contain Ha, and in this case, the raw materials in step S1 further contain Ha in addition to the raw materials containing Li, P, and S. Here, Ha refers to a halogen element, and examples thereof include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0018] As shown in FIG. 3, the manufacturing method according to this embodiment may further include the following step S3 after the step S2: Step S3: After precipitating the solid in step S2, further performing post-heat treatment by heating.

[0019] Each step will be explained in order.

[0020] <Step S1: Heat Treatment> In step S1 of this embodiment, raw materials containing Li, P, and S, and a compound represented by the formula M α N β This is a process of heat-treating a nitride represented by the formula (I) to obtain a melt. Furthermore, each raw material may further contain a raw material containing Ha from the viewpoint of improving lithium ion conductivity, etc. In this embodiment, each raw material containing Li, P, and S includes one or more raw materials containing one or more elements selected from the group consisting of Li, P, and S. Furthermore, a raw material containing Ha, etc. may further be included.

[0021] Formula M α N β In the nitride represented by the formula M, the element represented by M is at least one element selected from the group consisting of metal elements or metalloid elements of Groups 2 to 14 of the periodic table. α N β where α and β are the formula M α N β In addition, Ha is a halogen element, and examples thereof include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0022] Examples of raw materials containing lithium element (Li) include lithium sulfide (Li ２ S), lithium iodide (LiI), lithium carbonate (Li ２ CO ３), lithium sulfate (Li ２ SO ４ ), lithium oxide (Li ２ Examples of the raw material containing lithium element (Li) include lithium compounds such as lithium ion (LiO), lithium hydroxide (LiOH), and metallic lithium. One type of raw material containing lithium element (Li) may be used, or two or more types may be used in combination.

[0023] As the raw material containing lithium element (Li), lithium sulfide is preferably used from the viewpoint of obtaining a sulfide material. Furthermore, when the obtained sulfide solid electrolyte contains a halogen element (Ha), it is also preferable to use lithium halide (LiHa) as the raw material containing lithium element (Li). Lithium halide will be described later.

[0024] As the raw material containing phosphorus (P), a suitable combination of substances containing P, such as simple P or a compound containing P, can be used. The raw material containing phosphorus (P) may be used alone or in combination of two or more.

[0025] As a raw material containing phosphorus (P), diphosphorus pentasulfide (P ２ S ５ ), diphosphorus trisulfide (P ２ S ３ ) and other phosphorus sulfides, sodium phosphate (Na ３ P.O. ４ As the raw material containing elemental phosphorus (P), from the viewpoint of obtaining a sulfide material, it is preferable to use phosphorus sulfide, and it is more preferable to use diphosphorus pentasulfide.

[0026] As the raw material containing sulfur element (S), a substance containing S such as simple S or a compound containing S can be used in appropriate combination. The raw material containing sulfur element (S) may be used alone or in combination of two or more. As the raw material containing sulfur element (S), for example, diphosphorus pentasulfide (P ２ S ５ ), diphosphorus trisulfide (P ２ S ３ ) and other phosphorus sulfides, Li ２Examples of sulfur-containing compounds include alkali metal sulfides such as S, other sulfur compounds containing phosphorus, elemental sulfur, and compounds containing sulfur. ２ S, CS ２ , iron sulfide (FeS, Fe ２ S ３ , FeS ２ , Fe １－ｘ S, etc.), bismuth sulfide (Bi ２ S ３ ), copper sulfide (CuS, Cu ２ S, Cu １－ｘ S, etc.) ２ S is a compound that serves as both a raw material containing sulfur element (S) and a raw material containing lithium element (Li) as described above. ２ S ５ is a compound that serves as both a raw material containing sulfur element (S) and a raw material containing phosphorus element (P) as described above.

[0027] Examples of raw materials containing a halogen element (Ha) that can be used optionally include lithium halides (LiHa) such as lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), phosphorus halides, phosphoryl halides, sulfur halides, sodium halides, and boron halides. Among these, lithium halides are preferred from the viewpoint of preventing the inclusion of elements other than those constituting the target sulfide solid electrolyte. These compounds may be used alone or in combination of two or more. Furthermore, the halogen element may be introduced by hydrogen halide or halogen gas, and when Ha is Br or I, Br ２ Ya I ２ It may be introduced as

[0028] Ha preferably contains at least one of Br and I, and more preferably contains both.

[0029] Formula M α N βThe element represented by M in the nitride represented by the formula (hereinafter sometimes simply referred to as "nitride") is at least one selected from the group consisting of metal elements or metalloid elements of Groups 2 to 14 of the periodic table. The element represented by M is preferably at least one selected from the group consisting of metal elements or metalloid elements of Groups 3 to 14 of the periodic table, more preferably at least one selected from the group consisting of metal elements or metalloid elements of Groups 4 to 14 of the periodic table, and even more preferably at least one selected from the group consisting of metal elements or metalloid elements of Groups 13 to 14 of the periodic table. Among these, from the viewpoint of ease of material procurement, at least one selected from the group consisting of Si, Al, and B is even more preferable, and Si is particularly preferable.

[0030] Formula M α N β where α and β are values ​​that correspond to the stoichiometric ratio of M and N in the nitride. For example, if M is Si, the nitride is Si ３ N ４ where α is 3 and β is 4. When M is Al, the nitride is aluminum nitride, represented by AlN, where α is 1 and β is 1. When M is B, the nitride is boron nitride, represented by BN, where α is 1 and β is 1.

[0031] That is, the formula M α N β The nitride represented by the formula Si ３ N ４ At least one selected from the group consisting of AlN and BN is more preferred, and Si ３ N ４ is particularly preferred.

[0032] By using the nitrides together with the raw materials, it is possible to suppress the volatilization of nitrogen when heated to obtain a melt. ３ Since there is no need to go through an intermediate with N, a sulfide solid electrolyte can be obtained with a small number of steps. ３ Since there is no need to use highly reactive compounds such as N, it is also excellent in safety. However, Li ３ This does not exclude any embodiment using N.

[0033] Here, the conventional sulfide solid electrolyte containing N as a constituent element is Li ３ The reason why sulfide solid electrolytes react easily with water is that the P in the sulfide solid electrolyte ２ O ７ ４－ It is said that this is because S in the partial structure represented by the formula (I) exhibits high reactivity with water. On the other hand, it is thought that the reason why water resistance is improved by introducing N is that the S is crosslinked with N, resulting in a decrease in reactivity with water.

[0034] In order for the introduced nitrogen to function as described above, Li ３ Although it is believed that a highly reactive nitride such as N is necessary, N is easily evaporated due to its high reactivity. ３ An intermediate product obtained by reacting N with a highly stable nitride such as AlN is used.

[0035] In contrast, the present invention uses Li, which is highly reactive and difficult to handle. ３ The compound of the formula M, which has high chemical stability, is used instead of N. α N β On the other hand, in the case of a sulfide solid electrolyte obtained by firing a raw material mixture without going through a melting step, the effect of improving water resistance due to the introduction of N can be suitably obtained even when a nitride represented by the formula (I) is used. ３ Even if only the nitrides are used without using N, N is not introduced due to its high chemical stability.

[0036] Formula M α N β The specific surface area of ​​the nitride is 15 to 50 m ２ / g is preferred, and 25 to 40m ２ Here, from the viewpoint of preventing the nitride from remaining unmelted during heating, increasing reactivity, and obtaining a sulfide solid electrolyte of a desired composition, the specific surface area is 15 m ２ / g or more is preferable, and 25m ２ / g or more is more preferable, and 35m ２From the viewpoint of suppressing scattering of the raw material, the specific surface area is more preferably 50 m / g or more. ２ / g or less is preferable, and 40m ２ The specific surface area of ​​the nitride in this specification means the specific surface area determined by the nitrogen adsorption BET multipoint method.

[0037] The raw materials of the sulfide solid electrolyte in this embodiment are Li ２ S, P ２ S ５ and at least one selected from the group consisting of LiCl, LiBr and LiI, and Li ２ S, P ２ S ５ and more preferably contains at least one of LiBr and LiI.

[0038] In addition, the raw materials of the sulfide solid electrolyte in this embodiment are Li ２ S and P ２ S ５ and the nitride comprises Si ３ N ４ Each raw material preferably contains Li ２ S, P ２ S ５ and at least one of LiBr and LiI, and the nitride is Si ３ N ４ It is more preferred that the composition contains:

[0039] Each raw material in this embodiment may further contain a raw material containing an element other than the above-mentioned Li, P, S, and optionally Ha, within a range that does not impair the effects of the present invention. The above-mentioned other element may be an element represented by M, that is, a metal element or a metalloid element of Groups 2 to 14 of the periodic table.

[0040] Examples of other elements include tin (Sn), antimony (Sb), germanium (Ge), indium (In), copper (Cu), silicon (Si), aluminum (Al), boron (B), etc. Conventionally known raw materials containing these elements can be used.

[0041] The sulfide solid electrolyte obtained by the production method according to this embodiment is used in lithium ion secondary batteries, but when used in sodium ion secondary batteries or potassium ion secondary batteries, sodium (Na) or potassium (K) may be used instead of lithium (Li). In this case, a conventionally known raw material containing Na or K can be used.

[0042] When the raw materials and the nitride are heat-treated, as described above, the raw materials containing Li, P, and S, and the nitride of formula M α N β Alternatively, a step of mixing nitrides represented by the following formula (I) to obtain a raw material mixture may be carried out.

[0043] The raw materials and the nitride can be mixed by a conventionally known method, such as mixing in a mortar, mixing using media such as a planetary ball mill, or medialess mixing such as a pin mill, powder mixer, or airflow mixing. The raw materials may be made amorphous by the above-mentioned mixing.

[0044] When the raw materials and the nitride are not mixed in step S1a, the mixed raw materials and the nitride may be charged into the container sequentially or simultaneously.

[0045] The heat treatment in step S1 or S1b produces a melt. The specific method for producing the melt by heat treatment is not particularly limited. For example, the raw materials and nitrides, or a mixture of these raw materials, are placed in a heat-resistant container and heated in a heating furnace.

[0046] The heat-resistant container may be a heat-resistant container made of carbon, a heat-resistant container containing an oxide such as quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconia, or mullite, a heat-resistant container containing a nitride such as silicon nitride or boron nitride, or a heat-resistant container containing a carbide such as silicon carbide, etc. Furthermore, these heat-resistant containers may be formed in bulk from the above-mentioned materials, or may be containers on which a layer of carbon, oxide, nitride, carbide, or the like is formed, such as a carbon-coated quartz tube.

[0047] As the furnace body in the heating furnace used for the heat treatment, a conventionally known furnace having a heating section can be used as appropriate, and the material and size of the furnace body can also be selected arbitrarily.

[0048] The temperature of the heat treatment is not particularly limited as long as the raw materials and nitrides, or raw material mixture, are melted and a melt is obtained, but is preferably 600 ° C or higher, more preferably 600 to 1000 ° C, even more preferably 630 to 950 ° C, even more preferably 650 ° C or higher but less than 900 ° C, even more preferably 650 to 850 ° C, and particularly preferably 650 ° C or higher but less than 850 ° C. Here, from the viewpoint of obtaining a homogeneous melt without unmelted nitride, it is preferable that the melt consisting of components other than the nitride to be melted becomes liquid, and the temperature of the heat treatment is preferably 600 ° C or higher, more preferably 630 ° C or higher, and even more preferably 650 ° C or higher. In addition, from the viewpoint of suppressing deterioration and decomposition of the components in the melt, the temperature of heat melting is preferably 1000 ° C or lower, more preferably 950 ° C or lower, even more preferably less than 900 ° C, even more preferably 850 ° C or lower, and particularly preferably less than 850 ° C. The temperature of the heat treatment is the temperature of the molten material produced in the furnace, and can be adjusted by a heating unit provided in the furnace.

[0049] The heat treatment time is not particularly limited as long as the raw materials and nitride, or the raw material mixture, are melted, but is, for example, preferably 10 minutes to 10 hours (600 minutes), more preferably 30 minutes to 9.5 hours, even more preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. Here, from the viewpoint of smoothly progressing the reaction and obtaining a homogeneous melt without any unmelted nitride, the heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more, even more preferably 45 minutes or more, and particularly preferably 1 hour or more. Furthermore, from the viewpoint of suppressing deterioration or decomposition of components in the melt due to heating, the heat treatment time is preferably 10 hours or less, more preferably 9.5 hours or less, and even more preferably 9 hours or less.

[0050] The heat treatment is preferably performed in an inert atmosphere, such as a nitrogen gas atmosphere, an argon gas atmosphere, or a helium gas atmosphere.

[0051] The heat treatment may be performed in a gas atmosphere containing sulfur (S). Examples of the gas atmosphere containing sulfur (S) include a mixed gas atmosphere of a gas containing sulfur (S), such as sulfur gas, hydrogen sulfide gas, or sulfur dioxide gas, and an inert gas.

[0052] The dew point during the heat treatment is preferably −20° C. or lower in order to prevent side reactions between the melt and water vapor, oxygen, etc. The lower limit of the dew point is not particularly limited, but is usually about −80° C. The oxygen concentration during the heat treatment is preferably 1000 ppm by volume or lower.

[0053] The pressure during the heat treatment is not particularly limited as long as each raw material and nitride, or the raw material mixture, is melted, but for example, atmospheric pressure or slight pressure is preferred, and atmospheric pressure is more preferred.

[0054] The heat treatment is preferably carried out under one or more of the following conditions: an atmosphere containing S, a heating temperature of 600 to 1000°C, a heating time of 10 to 600 minutes, an atmosphere with a dew point of -20°C or less, and an atmosphere with an oxygen concentration of 1000 ppm by volume or less, more preferably under two or more conditions, even more preferably under three or more conditions, still more preferably under four or more conditions, and particularly preferably under all five conditions. It is also more preferable to carry out heating at 600 to 1000°C for 10 to 600 minutes.

[0055] In step S1 or step S1b, whether each raw material and nitride, or the raw material mixture, is completely melted can be confirmed by the absence of peaks derived from crystals in high-temperature X-ray diffraction measurement.

[0056] In step S1 or step S1b, a compound that will become a crystal nucleus may be contained in the melt in order to facilitate precipitation of a solid in the subsequent step S2. The method for containing the compound that will become a crystal nucleus in the melt is not particularly limited, but examples thereof include a method of adding the compound that will become a crystal nucleus to raw materials, and a method of directly adding the compound that will become a crystal nucleus to the melt that is being heat-treated.

[0057] Examples of compounds that can serve as crystal nuclei include oxides, oxynitrides, nitrides, carbides, other chalcogen compounds, and halides. Compounds that can serve as crystal nuclei are preferably compounds that have a certain degree of compatibility with the melt. Note that compounds that are completely incompatible with the melt cannot serve as crystal nuclei.

[0058] <Step S2: Cooling> In this embodiment, step S2 is a step of cooling the melt obtained in step S1 or step S1b to precipitate a solid. The solid obtained in step S2 may be used as the sulfide solid electrolyte, or a product that has undergone a post-heat treatment in the subsequent step S3 may be used as the sulfide solid electrolyte.

[0059] The solid precipitated by the cooling in step S2 may be a crystalline phase, an amorphous phase, or a phase containing both a crystalline phase and an amorphous phase. The phase state of the solid is determined by the ratio of each raw material and nitride added, i.e., the target composition, the cooling rate, etc.

[0060] The solid obtained by the manufacturing method according to this embodiment differs depending on the raw materials and nitrides, but it is preferable to use raw materials containing Li, P, S, and Ha, and a compound represented by the formula M α N β When a nitride represented by the formula: Li ａ’ PM ｂ’ S ｃ’ N ｄ’ Ha ｅ’ A solid represented by the formula (1) is obtained. Here, a' to e' respectively represent the content ratios (atomic ratios) of Li, M, S, N, and Ha based on the content ratio of P. Here, M may be one element or two or more elements. Furthermore, Ha is optional, and when Ha is contained, it may be one element or two or more elements.

[0061] In step S2, the molten material obtained in step S1 or S1b is discharged at any timing, for example, from a discharge port provided in the furnace body, and the process proceeds to a step of cooling and solidifying. A known method can be used to cool the molten material, and there is no particular limitation. For example, from the viewpoint of increasing the cooling rate, cooling using a twin roller, which is generally considered to have the fastest quenching rate, is preferred.

[0062] The cooling rate is preferably 1,000 to 100,000°C / sec. From the viewpoint of improving composition homogeneity and suppressing quality variations, the cooling rate is preferably 1,000°C / sec or more, more preferably 3,000°C / sec or more, and even more preferably 5,000°C / sec or more. The upper limit of the cooling rate is not particularly limited, but taking into account the cooling rate of a twin roller, which is generally said to have the fastest quenching rate, the upper limit is 1,000,000°C / sec or less. From the viewpoint of practical production, the cooling rate is more preferably 100,000°C / sec or less, even more preferably 80,000°C / sec or less, and even more preferably 50,000°C / sec or less.

[0063] The atmosphere during cooling is preferably a low moisture, inert atmosphere, similar to the heating treatment in step S1 or step S1b.

[0064] Furthermore, the cooling and solidification is preferably carried out under normal pressure. Here, "under normal pressure" means that the pressure is not controlled during cooling. Specifically, the pressure is about 0.8 to 1.2 atm.

[0065] <Step S3: Post-heat treatment> Step S3 in this embodiment is an optional step of performing post-heat treatment by heating again after the solid is precipitated in step S2. The post-heat treatment can improve the lithium ion conductivity of the resulting sulfide solid electrolyte.

[0066] The post-heat treatment in step S3 promotes crystallization if the solid obtained in step S2 contains an amorphous phase. The post-heat treatment may also rearrange ions within the crystalline structure to increase lithium ion conductivity.

[0067] That is, the post-heat treatment refers to at least one of a heat treatment for crystallizing the obtained solid and a heat treatment for rearranging ions in the crystal structure.

[0068] The temperature in the post-heat treatment is preferably 150 to 400° C., more preferably 150 to 350° C., and even more preferably 180 to 300° C. Here, from the viewpoint of suitably obtaining the effects of the post-heat treatment and from the viewpoint of shortening the time for the post-heat treatment, the temperature in the post-heat treatment is preferably 150° C. or higher, and more preferably 180° C. or higher. Furthermore, from the viewpoint of preventing unintended crystal precipitation, the temperature in the post-heat treatment is preferably 400° C. or lower, more preferably 350° C. or lower, and even more preferably 300° C. or lower.

[0069] The time for the post-heat treatment is preferably 10 minutes to 10 hours, more preferably 10 minutes to 5 hours, and even more preferably 10 minutes to 1 hour. The time for the post-heat treatment is preferably 10 minutes or more, and is preferably 10 hours or less, more preferably 5 hours or less, and even more preferably 1 hour or less.

[0070] The atmosphere for the post-heat treatment is preferably an inert atmosphere. Examples of the inert atmosphere include a nitrogen gas atmosphere, an argon gas atmosphere, and a helium gas atmosphere. The dew point during the post-heat treatment is preferably −20° C. or lower, and although there is no particular lower limit, it is usually about −80° C. The oxygen concentration during the post-heat treatment is preferably 1000 ppm by volume or lower.

[0071] The post-heat treatment is preferably carried out under one or more of the following conditions: a heating temperature of 150 to 400°C, a heating time of 10 minutes to 10 hours, in an atmosphere with a dew point of -20°C or lower, and in an atmosphere with an oxygen concentration of 1000 volume ppm or lower, more preferably under two or more of these conditions, even more preferably under three or more of these conditions, and particularly preferably under all four of these conditions. It is also more preferable to carry out heating at 150 to 400°C for 10 minutes to 10 hours.

[0072] <<Method for Manufacturing Lithium-Ion Secondary Battery>> The method for manufacturing a lithium-ion secondary battery according to this embodiment includes a step of interposing a sulfide solid electrolyte between a positive electrode and a negative electrode. The sulfide solid electrolyte may be one obtained by the method described in <<Method for Manufacturing Sulfide Solid Electrolyte>>. In particular, a sulfide solid electrolyte that has undergone the post-heat treatment of step S3 may be preferably used.

[0073] The positive electrode and the negative electrode each comprise an active material, a current collector, and optionally a conductive additive, a binder, etc., and may further comprise an electrode mixture containing a sulfide solid electrolyte in addition to these.

[0074] A conventionally known method can be used to interpose the sulfide solid electrolyte between the positive electrode and the negative electrode. For example, an additive such as a binder may be added to the sulfide solid electrolyte to form a sulfide solid electrolyte layer, which may then be interposed between the positive electrode and the negative electrode.

[0075] The binder may be a conventionally known material, such as butadiene rubber, acrylate butadiene rubber, styrene butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, etc. The content of the binder in the sulfide solid electrolyte layer is not particularly limited, and may be added within a conventionally known range.

[0076] <<Sulfide Solid Electrolyte>> The sulfide solid electrolyte according to this embodiment contains Li, P, S, M, and N as constituent elements. The constituent elements may further contain Ha, and may further contain other elements. Here, Ha refers to a halogen element, and examples thereof include fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0077] By producing the sulfide solid electrolyte by the method described in the above <<Production Method of Sulfide Solid Electrolyte>>, a sulfide solid electrolyte can be obtained in which the content ratio of M relative to the content ratio of N, among the constituent elements, is higher than conventional.

[0078] That is, the sulfide solid electrolyte according to this embodiment has the composition formula: Li ａ’ PM ｂ’ S ｃ’ N ｄ’ Ha ｅ’When expressed as M, the ratio of the content proportions represented by b' / d' is higher than that of conventionally known sulfide solid electrolytes. This ratio can be, for example, 0.5 or more, and may be 0.5 to 1. The ratio may be 0.5 or more, 0.6 or more, 0.7 or more, or 0.75 or more. The upper limit is not particularly limited, but may be, for example, 1 or less, 0.95 or less, 0.9 or less, 0.85 or less, or 0.8 or less. When there are two or more elements represented by M, the total content proportion thereof is taken as b'.

[0079] When producing the sulfide solid electrolyte according to this embodiment, α N β As a nitride represented by Si ３ N ４ When using the sulfide solid electrolyte, the resulting sulfide solid electrolyte has the composition formula: Li ａ PSi ｂ S ｃ N ｄ Ha ｅ where Ha is an arbitrary value.

[0080] In the above composition formula, the content ratio of P in atomic ratio among the constituent elements of the sulfide solid electrolyte is set to 1, the content ratio of Si is represented by b, and the content ratio of N is represented by d.

[0081] The ratio of the content proportions represented by b / d can be, for example, 0.5 to 1, and the ratio may be 0.6 to 0.95, or 0.65 to 0.9. Here, the ratio may be 0.5 or more, 0.6 or more, 0.65 or more, or 0.7 or more, or 1 or less, 0.95 or less, or 0.9 or less.

[0082] Composition formula: Li ａ PSi ｂ S ｃ N ｄ Ha ｅ From the viewpoint of increasing lithium ion conductivity, the sulfide solid electrolyte represented by the formula (I) preferably contains Ha, that is, the content ratio represented by e is greater than 0.

[0083] Ha is preferably at least one selected from the group consisting of Cl, Br and I, more preferably Br or I, and more preferably contains both Br and I.

[0084] Composition formula: Li ａ PSi ｂ S ｃ N ｄ Ha ｅThe content ratio of each constituent element in the sulfide solid electrolyte represented by the formula (1) is, for example, 2.00≦a≦4.50, 2.50≦a≦4.00, or 3.00≦a≦3.60 for Li. Here, a may be, for example, 2.00 or more, 2.50 or more, 3.00 or more, or 4.50 or less, 4.00 or less, or 3.60 or less. For Si, for example, b≦1.00, 0.05≦b≦0.50, 0.07≦b≦0.35, or 0.07≦b≦0.33. Here, b may be, for example, 0.01 or more, 0.05 or more, 0.07 or more, 1.00 or less, 0.50 or less, 0.35 or less, or 0.33 or less. Regarding S, for example, 3.00≦c≦4.20, 3.20≦c≦4.00, 3.40≦c≦3.80, or 3.40≦c≦3.60. Here, c is, for example, 3.00 or more, 3.20 or more, or 3.40 or more, or 4.20 or less, 4.00 or less, 3.80 or less, or 3.60 or less. Regarding N, for example, 0.01≦d≦1.33, 0.07≦d≦0.67, 0.09≦d≦0.47, or 0.10≦d≦0.45. Here, d is, for example, 0.01 or more, may be 0.07 or more, 0.09 or more, or 0.10 or more, and may be 1.33 or less, 0.67 or less, 0.47 or less, or 0.45 or less. Regarding Ha, for example, 0≦e≦0.60, 0<e≦0.58, 0.50≦e≦0.55, 0≦e≦0.53, or 0.50≦e≦0.53. Here, e is, for example, 0 or more, may be greater than 0, 0.50 or more, 0.60 or less, 0.58 or less, 0.55 or less, or 0.53 or less.

[0085] Also, the composition formula: Li ａ PSi ｂ S ｃ N ｄ Ha ｅThe combination of the content ratios of the constituent elements in the sulfide solid electrolyte represented by the formula (1) may satisfy, for example, 2.00≦a≦4.50, 0.01≦b≦1.00, 3.00≦c≦4.20, 0.01≦d≦1.33, and 0<e≦0.60, and may satisfy, for example, 2.50≦a≦4.00, 0.05≦b≦0.50, 3.20≦c≦4.00, 0.07≦d≦0.67, and , 0<e≦0.58, 3.00≦a≦3.60, 0.07≦b≦0.35, 3.40≦c≦3.80, 0.09≦d≦0.47, and 0.50≦e≦0.55, or 3.00≦a≦3.60, 0.07≦b≦0.33, 3.40≦c≦3.60, 0.10≦d≦0.45, and 0≦e≦0.53.

[0086] Composition formula: Li ａ PSi ｂ S ｃ N ｄ Ha ｅ In the sulfide solid electrolyte represented by the formula (I), when two or more elements are contained as Ha, the total content ratio of these elements is e. For example, when the elements represented by Ha are Br and I, the above composition formula is Li ａ PSi ｂ S ｃ N ｄ Br ｅ１ I ｅ２ Here, e1 indicating the content ratio of Br and e2 indicating the content ratio of I satisfy the relationship e1+e2=e.

[0087] Here, for Br, for example, 0<e1≦0.55, 0.20≦e1≦0.40, or 0.30≦e1≦0.34 may be satisfied. Here, e1 may be, for example, greater than 0, 0.20 or greater, 0.30 or greater, 0.55 or less, 0.40 or less, or 0.34 or less. For I, for example, 0<e2≦0.55, 0.10≦e2≦0.40, or 0.19≦e2≦0.23 may be satisfied. Here, e2 may be, for example, greater than 0, 0.10 or greater, 0.19 or greater, 0.55 or less, 0.40 or less, or 0.23 or less.

[0088] One embodiment of the combination of the above e1 and e2 with the content ratios of other constituent elements a, b, c, and d is the same as the combination of a, b, c, d, and e described above, in which e is replaced with e1 and e2. That is, for example, the following conditions are satisfied: 3.00≦a≦3.60, 0.07≦b≦0.35, 3.40≦c≦3.80, 0.09≦d≦0.47, 0.30≦e1≦0.34, and 0.19≦e2≦0.23.

[0089] The sulfide solid electrolyte according to this embodiment may be a crystalline phase, an amorphous phase, or may contain both a crystalline phase and an amorphous phase. The phase state is determined by the ratio of each raw material and nitride added, i.e., the composition of the sulfide solid electrolyte, the cooling rate, etc. Furthermore, the obtained solid may be subjected to post-heat treatment to convert part or all of the amorphous phase into a crystalline phase.

[0090] When the sulfide solid electrolyte according to this embodiment includes a crystalline phase, the crystal structure of the crystalline phase is not particularly limited, and examples thereof include an argyrodite type, an LPS type, an LGPS type, etc. Also, a Li-P-S-Ha-based crystallized glass type may be used.

[0091] The phase state and composition of the sulfide solid electrolyte can be identified by analyzing the elemental composition using various methods, such as crystal structure analysis by X-ray diffraction (XRD), ICP optical emission spectrometry, atomic absorption spectrometry, and ion chromatography. For example, P, S, and M can be measured by ICP optical emission spectrometry, Li by atomic absorption spectrometry, and Ha by ion chromatography. The N content can be determined by sealing a sample together with Cu in a Sn capsule under an Ar atmosphere and using an oxygen, nitrogen, and hydrogen analyzer (EMGA-930 manufactured by Horiba, Ltd.).

[0092] The sulfide solid electrolyte obtained by the production method according to this embodiment is used in lithium ion secondary batteries, but when used in sodium ion secondary batteries or potassium ion secondary batteries, sodium (Na) or potassium (K) may be used instead of lithium (Li). In this case, Na or K can be identified by, for example, atomic absorption spectrometry.

[0093] The secondary particle diameter of the sulfide solid electrolyte according to this embodiment is preferably small from the viewpoint of obtaining good ionic conductivity when used in a secondary battery. Specifically, the secondary particle diameter is preferably 10 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. The lower limit of the secondary particle diameter is not particularly limited, but is usually 0.1 μm or more. The secondary particle diameter can be measured using a microtrack device.

[0094] The lithium ion conductivity of the sulfide solid electrolyte according to this embodiment at 25° C. is 0.1×10 －３ S / cm or more is preferable, and 1×10 －３ S / cm or more is more preferable, and 2×10 －３ The upper limit of the lithium ion conductivity is not particularly limited, but it is usually 1×10 －１ The lithium ion conductivity is 0.05 S / cm or less. The lithium ion conductivity can be measured by an AC impedance method. Specifically, the lithium ion conductivity is a value measured using an AC impedance measuring device (for example, a potentiostat / galvanostat VSP manufactured by Bio-Logic Sciences Instruments) under the following conditions: a measurement frequency of 100 Hz to 1 MHz, a measurement voltage of 100 mV, and a measurement temperature of 25°C.

[0095] The sulfide solid electrolyte according to this embodiment is suitable for use in electrode mixtures and solid electrolyte layers used in secondary batteries, and is particularly suitable for all-solid-state secondary batteries, and more suitable for all-solid-state lithium-ion secondary batteries. That is, the electrode mixture is used in secondary batteries and contains the sulfide solid electrolyte and an active material. The solid electrolyte layer is used in secondary batteries and contains the sulfide solid electrolyte.

[0096] The electrode mixture, solid electrolyte layer, and all-solid-state lithium ion secondary battery may further contain other solid electrolytes in addition to the sulfide solid electrolyte according to this embodiment.

[0097] The active material contained in the electrode mixture may be a conventionally known material. The positive electrode active material is not particularly limited as long as it can reversibly absorb and release alkali metal ions, intercalate and deintercalate alkali metal ions, or dope and dedope counter anions of the alkali metal ions. Here, the alkali metal ion is preferably lithium ion. Specific examples of the positive electrode active material include lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel manganate, composite metal oxides, and polyanion olivine-type positive electrodes.

[0098] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release alkali metal ions, detach and insert (intercalate) alkali metal ions, or reversibly dope and dedope counter anions of the alkali metal ions. Here, the alkali metal ions are preferably lithium ions. Specific examples of the negative electrode active material include lithium metal, carbon-based materials such as graphite, hard carbon, and soft carbon, metals that can form alloys with lithium such as aluminum, silicon, and tin, amorphous oxides such as silicon oxide and tin oxide, and lithium titanate.

[0099] The solid electrolyte layer may contain the sulfide solid electrolyte according to the present embodiment, but may also contain other solid electrolytes and additives such as a binder. Conventionally known binders can be used, such as butadiene rubber, acrylate butadiene rubber, styrene butadiene rubber, polyvinylidene fluoride, and polytetrafluoroethylene. The binder content in the solid electrolyte layer may also be within a conventionally known range.

[0100] The all-solid-state secondary battery is not particularly limited as long as it includes a positive electrode and a negative electrode in addition to the sulfide solid electrolyte according to this embodiment. The positive electrode and the negative electrode may be an electrode mixture containing the sulfide solid electrolyte according to this embodiment. The positive electrode active material may be the same as the positive electrode active material described in the electrode mixture, and the positive electrode may further include a positive electrode current collector, a binder, a conductive additive, and the like, as necessary. The positive electrode current collector may be made of aluminum, an alloy thereof, a thin metal plate such as stainless steel, or the like.

[0101] The negative electrode active material can be the same as the negative electrode active material described in the electrode mixture, and the negative electrode may further contain, as necessary, a negative electrode current collector, a binder, a conductive additive, etc. The negative electrode current collector can be a thin metal plate such as copper or aluminum.

[0102] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. Examples 1, 2, 5, and 6 are working examples, and Examples 3 and 4 are comparative examples.

[0103] Example 1: Under a dry nitrogen gas atmosphere, each raw material and nitride were weighed and mixed in a mortar to obtain a raw material mixture. Specifically, the raw material mixture was composed of, in molar ratio, 56.8 mol% lithium sulfide powder (manufactured by Sigma, purity 99.98%) as a raw material containing Li and S, 19.2 mol% diphosphorus pentasulfide powder (manufactured by Sigma, purity 99%) as a raw material containing P and S, 12.0 mol% lithium bromide powder (manufactured by Sigma, purity 99.995%) as a raw material containing Li and Br, 8.0 mol% lithium iodide powder (manufactured by Tokyo Chemical Industry Co., Ltd., purity 99.9%, low moisture grade) as a raw material containing Li and I, and 10.0 mol% lithium iodide powder (manufactured by Tokyo Chemical Industry Co., Ltd., purity 99.9%, low moisture grade) as a raw material containing Li and I. α N β As a nitride represented by Si ３ N ４ (manufactured by Sigma, purity ≧98.5%, specific surface area 35 m ２ 4.0 mol % of sulfur dioxide (sulfur dioxide / g) and 4 wt % of elemental sulfur powder (Hosoi Chemical Co., Ltd., sulfur powder-16-60 Mesh) were used relative to the total weight of the raw materials and nitride.

[0104] The raw material mixture obtained above was placed in a heat-resistant container and melted at 750° C. for 1 hour in an atmosphere of a gas containing elemental sulfur, and then cooled to room temperature at 10,000° C. / sec to obtain a solid.

[0105] <<Example 2>> Formula M α N β As a nitride represented by Si ３ N ４ (manufactured by Sigma, purity ≧99.9% trace metals basis, specific surface area 11 m ２ A solid was obtained in the same manner as in Example 1 except that 1.0 mol % of PEG-14 / g was used.

[0106] Example 3 The raw material mixture obtained in the same manner as in Example 1 was further mixed using a planetary ball mill (LP-M2, manufactured by Ito Seisakusho Co., Ltd.) to obtain a powdery solid.

[0107] Example 4 The raw material mixture obtained in the same manner as in Example 2 was further mixed using a planetary ball mill (LP-M2, manufactured by Ito Seisakusho Co., Ltd.) to obtain a powdery solid.

[0108] Example 5 The solid obtained in Example 1 was further subjected to post-heat treatment at 220° C. for 10 minutes in a dry nitrogen gas atmosphere to obtain a solid.

[0109] Example 6 The solid obtained in Example 2 was further subjected to post-heat treatment at 195° C. for 10 minutes in a dry nitrogen gas atmosphere to obtain a solid.

[0110] Evaluation Reactivity and Composition The reactivity of the solids obtained in Examples 1 to 4 was evaluated by X-ray diffraction (XRD) measurement and visual observation. For XRD measurement, each solid was crushed in a mortar and passed through a 100 μm sieve to obtain a powder with a D50 of approximately 10 to 20 μm. Here, D50 refers to the volume-based median diameter. XRD measurement of the powders obtained above was performed using an X-ray diffractometer (Rigaku Corporation, SmartLab) in an environment not exposed to air under the following conditions: Radiation source: CuKα radiation (λ = 1.5418 Å), tube voltage: 45 kV, tube current: 200 mA, scan angle: 10 to 100°, scan rate: 5° / min, and step number: 0.01° / step.

[0111] The results are shown in the "Reactivity" section of Table 1, and the evaluation criteria are as follows: ∘: No peaks derived from the raw materials or nitrides are observed in the XRD pattern, the solid is uniform overall, and can be used as a sulfide solid electrolyte as is. Δ: Slight peaks derived from the raw materials or nitrides are observed in the XRD pattern, and slight black spots are visible in some parts of the solid, but these spots can be easily removed and the solid can be used as a sulfide solid electrolyte. ×: Peaks derived from the raw materials or nitrides are clearly observed in the XRD pattern, the solid is a mixture of multiple compounds, and a sulfide solid electrolyte containing N as a constituent element has not been synthesized.

[0112] The compositions of the solids in Examples 1 and 2 for which the reactivity was "○" or "△" were identified. Specifically, ICP optical emission spectrometry was performed for P, S, and Si, atomic absorption spectrometry for Li, ion chromatography for Ha, and measurement using an oxygen, nitrogen, and hydrogen analyzer for N were performed to determine the composition of each solid. For N, the solid was encapsulated together with Cu in a Sn capsule under an Ar atmosphere, and the content was determined using an oxygen, nitrogen, and hydrogen analyzer (EMGA-930 manufactured by Horiba, Ltd.). The results are shown in "Composition" in Table 1, and it was confirmed that the obtained solid was a homogeneous amorphous phase and functioned as a sulfide solid electrolyte. In Examples 3 and 4, a sulfide solid electrolyte containing N as a constituent element was not obtained, so the composition is indicated as "-".

[0113] On the other hand, the solid powders of Examples 3 and 4 were rated as "x" in terms of reactivity, but the XRD patterns showed that the Si ３ N ４ It was confirmed that the sulfide powder was unreacted or reacted only slightly, and the generation of hydrogen sulfide could not be suppressed.

[0114] XRD measurements were also performed on the solids of Examples 5 and 6 under the same conditions as above. As a result, it was confirmed that a portion of the amorphous phase in Examples 1 and 2 crystallized, and that each was a sulfide solid electrolyte in which an amorphous phase and a crystalline phase coexisted. The XRD pattern of Example 5 is shown in FIG. 4, and the peak near 2θ = 17° is a peak derived from the sample stage. The compositions of Examples 5 and 6 are shown in "Composition" in Table 1. Note that, since Examples 5 and 6 are obtained by post-heat treating Examples 1 and 2, respectively, the "Reactivity" in Table 1 is marked "-".

[0115] Thermal measurements were also carried out on 20 mg of the solids of Examples 5 and 6. Specifically, DSC measurements were carried out using a differential scanning calorimeter (DSC3300, manufactured by BRUKER AXS) at a temperature increase rate of 5°C / min from 100 to 300°C to obtain DSC curves. The obtained DSC curves are shown in Figure 5, and in both Examples 5 and 6, an exothermic peak due to the precipitation of crystals with high ionic conductivity was confirmed in the range of 180 to 220°C.

[0116] <Lithium Ion Conductivity> The solids (sulfide solid electrolytes) obtained in Examples 1, 2, 5, and 6 were pulverized in a mortar and passed through a 100 μm sieve to obtain powders with a D50 of approximately 10 to 20 μm. Here, D50 refers to the volume-based median diameter. The resulting powders were used as samples, and the lithium ion conductivity was measured using an AC impedance measuring device (Bio-Logic Sciences Instruments, potentiostat / galvanostat VSP). The measurement conditions were: measurement frequency: 100 Hz to 1 MHz, measurement voltage: 100 mV, and measurement temperature: 25°C. The results are shown in Table 1. Note that in Examples 3 and 4, measurements were not performed because sulfide solid electrolytes containing N as a constituent element were not obtained.

[0117] <Water resistance: H ２ Amount of S Generated> The solids (sulfide solid electrolytes) obtained in Examples 1, 2, 5, and 6 were crushed in a mortar and passed through a 100 μm sieve to obtain powders with a D50 of approximately 10 to 20 μm. 20 mg of the powder obtained above was weighed out as a sample, and nitrogen gas with a dew point of −20° C. was flowed through the sample at a flow rate of 0.5 L / min for 30 minutes. The amount of H ２The amount of generated sulfur was measured and normalized by dividing by the weight of the sample (20 mg). The results are shown in Table 1. Note that in Examples 3 and 4, no sulfide solid electrolyte containing N as a constituent element was obtained, and therefore no measurement was performed.

[0118]

[0119] From the above results, the manufacturing method according to this embodiment melts the raw material and nitride by heat treatment, and then cools and solidifies it to form stable Si nitride. ３ N ４ It was found that a sulfide solid electrolyte containing N as a constituent element can be obtained even when using a sulfide solid electrolyte containing N as a constituent element. The sulfide solid electrolyte according to this embodiment exhibits lithium ion conductivity equal to or higher than that of conventional sulfide solid electrolytes, and also achieves good water resistance due to the inclusion of N as a constituent element. Furthermore, the results of Examples 5 and 6 show that even after post-heat treatment, a higher lithium ion conductivity was achieved while maintaining good water resistance.

[0120] On the other hand, in the conventional manufacturing method, even if a mixture of raw materials and nitride raw materials is heated and sintered, stable Si nitride is not obtained. ３ N ４ did not react, and a sulfide solid electrolyte containing N as a constituent element was not obtained.

[0121] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2024-045554) filed on March 21, 2024, the contents of which are incorporated herein by reference.

Claims

1. A method for producing a sulfide solid electrolyte containing Li, P, M, S, and N, comprising: α N β and cooling the melt to precipitate a solid, wherein the element represented by M is at least one element selected from the group consisting of metal elements and semimetal elements of Groups 2 to 14 of the periodic table, and ... α N β In the formula M, α and β are α N β The method for producing a sulfide solid electrolyte having a stoichiometric ratio of M and N in a nitride represented by the formula:

2. The method for producing a sulfide solid electrolyte according to claim 1, wherein the sulfide solid electrolyte further contains Ha, the raw materials further contain a raw material containing Ha, and the element represented by Ha is a halogen element.

3. The above raw materials are Li ２ S, P ２ S ５ and at least one selected from the group consisting of LiCl, LiBr, and LiI.

4. The method for producing a sulfide solid electrolyte according to claim 2 or 3, wherein the Ha includes at least one of Br and I.

5. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the element represented by M is at least one selected from the group consisting of Si, Al, and B.

6. The above formula M α N β The nitride represented by Si ３ N ４ The method for producing a sulfide solid electrolyte according to claim 1 or 2, comprising:

7. The above formula M α N β The nitride represented by the formula has a specific surface area of ​​30 m ２ The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the sulfide solid electrolyte is a powder having a surface area of ​​1000 nm or more.

8. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heat treatment is carried out in a gas atmosphere containing S.

9. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heat treatment is carried out at a temperature of 600 to 1000°C.

10. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heat treatment is carried out at a temperature of 650 to 850°C.

11. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heat treatment is carried out for 10 to 600 minutes.

12. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heat treatment is carried out in an atmosphere with a dew point of −20° C. or lower.

13. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the heat treatment is carried out in an atmosphere having an oxygen concentration of 1000 ppm by volume or less.

14. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the cooling is carried out at a cooling rate of 1,000 to 100,000°C / sec.

15. The method for producing a sulfide solid electrolyte according to claim 1 or 2, further comprising, after precipitating the solid, carrying out a post-heat treatment by heating.

16. The method for producing a sulfide solid electrolyte according to claim 15, wherein the post-heat treatment is carried out at a temperature of 150 to 400°C.

17. The method for producing a sulfide solid electrolyte according to claim 15, wherein the post-heat treatment is carried out in an atmosphere with a dew point of −20° C. or lower.

18. The method for producing a sulfide solid electrolyte according to claim 15, wherein the post-heat treatment is carried out in an atmosphere having an oxygen concentration of 1000 ppm by volume or less.

19. A method for producing a sulfide solid electrolyte according to claim 1 or 2, in which the lithium ion conductivity at 25°C is 1 mS / cm or more.

20. A sulfide solid electrolyte containing Li, P, S, Si, and N as constituent elements, wherein, among the constituent elements, the atomic ratio of the P content is 1, the Si content is b, and the N content is d, and the ratio of the content ratios expressed as b / d is 0.5 to 1.

21. The sulfide solid electrolyte according to claim 20, wherein the sulfide solid electrolyte further contains Ha as a constituent element, and the element represented by Ha is a halogen element.

22. The sulfide solid electrolyte has the composition formula: Li ａ PSi ｂ S ｃ N ｄ Ha ｅ The sulfide solid electrolyte according to claim 20 or 21, which is represented by the following formula: 3.00≦a≦3.60, 0.07≦b≦0.33, 3.40≦c≦3.60, 0.10≦d≦0.45, and 0≦e≦0.53 are satisfied.

23. The element represented by Ha is Br and I, and the sulfide solid electrolyte has the composition formula: Li ａ PSi ｂ S ｃ N ｄ Br ｅ１ I ｅ２ The sulfide solid electrolyte according to claim 21, which is represented by the following formula: 3.00≦a≦3.60, 0.07≦b≦0.35, 3.40≦c≦3.80, 0.09≦d≦0.47, 0.30≦e1≦0.34, and 0.19≦e2≦0.23.

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