Solid electrolyte and method for producing the same

Abstract

To provide a solid electrolyte exhibiting high ion conductivity.SOLUTION: A solid electrolyte includes a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonic acid salt which may have a substituent. In Formula (1), M represents a p-valent metal ion. R's each independently represent a substituent. Q represents a number from 0 to 2, r represents a number from 6 to 12, s represents a number from 0 to (r?1), t represents 0 or 1, and u represents 0 or 1. M(2?u) / p[CqB(r?q?t)H(r?q?s+t+u)RS] (1)SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] An all-solid-state battery is configured, for example, with a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode. Compositions containing carborane compounds have been proposed as the solid electrolyte. For example, [HCB 11 H 11 [HCB9H9Li] and [HCB9H9Li] each have very low Li ion conductivity at room temperature when used alone, but when mixed together they are said to exhibit high conductivity even at room temperature (see, for example, Non-Patent Document 1). Also, a solid electrolyte containing a closoborate salt containing an alkali metal or alkaline earth metal and a conductivity-enhancing salt containing a specific anion has been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2021 / 0408587 [Non-patent literature]

[0004] [Non-Patent Document 1] Nature Communications volume 10, Article number: 1081 (2019) Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional materials have problems such as difficulty in synthesis, and alternative materials have been sought. Therefore, an object of one aspect of the present disclosure is to provide a solid electrolyte exhibiting high ionic conductivity and a method for producing the same. [Means for solving the problem]

[0006] The first aspect is a solid electrolyte containing a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonate which may have a substituent. M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s ] (1)

[0007] In the formula, M represents a p-valent metal ion. Each R independently represents a substituent. q represents a number from 0 to 2, r represents a number from 6 to 12, s represents a number from 0 to (r-1), t represents 0 or 1, and u represents 0 or 1.

[0008] A second aspect is a method for producing a solid electrolyte, comprising heat-treating a mixture containing a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonate which may have a substituent at a temperature of 60°C or higher and 300°C or lower to obtain a solid electrolyte.

[0009] M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s ] (1)

[0010] In the formula, M represents a p-valent metal ion. Each R independently represents a substituent. q represents a number from 0 to 2, r represents a number from 6 to 12, s represents a number from 0 to (r-1), t represents 0 or 1, and u represents 0 or 1. [Effects of the Invention]

[0011] According to one aspect of the present disclosure, a solid electrolyte exhibiting high ionic conductivity and a method for producing the same can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows examples of X-ray diffraction spectra of solid electrolyte materials according to examples and comparative examples. [Figure 2] 1 is a graph showing the ionic conductivity of lithium ions in solid electrolyte materials according to Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0013] In this specification, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, the content of each component in a composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. Furthermore, the upper and lower limits of the numerical ranges described in this specification can be arbitrarily selected and combined from the numerical values ​​exemplified as numerical ranges. Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are intended to exemplify solid electrolytes and methods for producing the same in order to embody the technical concept of the present invention, and the present invention is not limited to the solid electrolytes and methods for producing the same shown below.

[0014] solid electrolyte The solid electrolyte contains a boron compound having a composition represented by the following formula (1) and a hydrocarbon sulfonate which may have a substituent. In one embodiment, the solid electrolyte may be a metal ion conductor, preferably an alkali metal ion conductor or an alkaline earth metal ion conductor, and may be a solid electrolyte for metal ion batteries, preferably a solid electrolyte for alkali metal ion batteries.

[0015] M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s ] (1)

[0016] In the formula, M represents a p-valent metal ion. Each R independently represents a substituent. q represents a number from 0 to 2, r represents a number from 6 to 12, s represents a number from 0 to (r-1), t represents 0 or 1, and u represents 0 or 1.

[0017] A solid electrolyte containing a boron compound with a specific composition and a hydrocarbon sulfonate can exhibit high ionic conductivity. This can be explained, for example, as follows: It is predicted that ionic conduction in carborane-based solid electrolytes occurs through interstitial or quasi-lattice diffusion. Therefore, it is believed that adding a salt that easily releases cations increases the cation carrier concentration in the mixed system, making ionic conduction more likely. Here, if the added salt contains a sulfonate group, the sulfonate group is a conjugate base of a strong acid, and therefore it is believed that it can form a salt that easily releases cations. Therefore, it is predicted that combining a hydrocarbon sulfonate with a boron compound with a specific composition improves ionic conductivity.

[0018] The compounds represented by formula (1) are boron clusters formed by the polymerization of boron hydride (borane) or salts of its carbon-substituted derivatives, and the anion portion has a closed-shell hollow three-dimensional structure consisting of a polyhedron. Anions containing carbon in formula (1) are collectively called carborane anions.

[0019] In formula (1), metal elements forming p-valent metal ions represented by M include, for example, alkali metal elements such as lithium, sodium, and potassium; Group 2 metal elements such as calcium and magnesium; and Group 13 metal elements such as zinc and aluminum. p may be a number from 1 to 3, and preferably 1 or 2, or 1. In one embodiment, M may be an alkali metal ion, and preferably a lithium ion or a sodium ion.

[0020] In formula (1), examples of the substituent represented by R include a halogen atom. The halogen atom represented by R may include at least one selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The substituents represented by R may be the same or different from each other.

[0021] q represents a number from 0 to 2, and may preferably be 1 or 2, or 1. r represents a number from 6 to 12, and may preferably be 10 or 12, or 12. s represents a number from 0 to (r-1), and may preferably be 0 to 1, or 0. t represents 0 or 1, and may preferably be 0. u represents 0 or 1, and may preferably be 0.

[0022] In one embodiment, the combination of q, t, and u, (q,t,u), may be (0,0,0), (1,0,1), (2,0,1), (2,1,1), or (2,1,0). That is, the boron compound having the composition represented by formula (1) may be a compound represented by any of the following formulas (1a) to (1e).

[0023] M 2 / p [CB r H (r-s) R s ] (1a) M 1 / p [CB (r-1) H (r-s) R s ] (1b) M 1 / p [C2B (r-2) H (r-s-1) R s ] (1c) M 1 / p [C2B (r-3) H (r-s) R s ] (1d) M 2 / p [C2B (r-3) H (r-sー1) R s ] (1e)

[0024] The boron compound having the composition represented by formula (1) may be obtained by transfer or the like, or may be synthesized as a desired boron compound according to a known synthesis method.

[0025] The hydrocarbon sulfonate contained in the solid electrolyte is a metal salt of a hydrocarbon compound having a sulfonate group. The hydrocarbon compound constituting the hydrocarbon sulfonate may be an aromatic hydrocarbon compound or an aliphatic hydrocarbon compound. The aliphatic hydrocarbon compound may be a saturated aliphatic hydrocarbon compound or an unsaturated aliphatic hydrocarbon compound. The hydrocarbon compound may have at least one ring structure. The ring structure contained in the hydrocarbon compound may have, for example, 5 to 12 members, preferably 6 members. The number of ring structures contained in the hydrocarbon compound may be, for example, 1 to 6 members, preferably 1 to 3 members, or 2 members. When the hydrocarbon compound contains multiple ring structures, the hydrocarbon compound may have a fused ring structure or a bridged ring structure. The ring structure may be a monocyclic, bicyclic, tricyclic, or tetracyclic ring structure. In one embodiment, when the steric structure of the hydrocarbon compound is similar to that of carborane, it is believed that solid solution is easily achieved. As described in Non-Patent Document 1, the solid solution is expected to stabilize the high-temperature phase of carborane at room temperature, thereby improving ionic conductivity.

[0026] The hydrocarbon compound may have 1 to 30 carbon atoms, preferably 5 or more or 9 or more, and preferably 20 or less or 15 or less. In the hydrocarbon sulfonate salt, the number of sulfonate groups in the hydrocarbon compound may be 1 or more and 3 or less, preferably 2 or less.

[0027] When the hydrocarbon compound contains a ring structure, at least one of the carbon atoms forming the ring may be substituted with a heteroatom. Examples of the heteroatom include nitrogen, oxygen, sulfur, and phosphorus. When the hydrocarbon compound contains a heteroatom in the ring structure, the number of heteroatoms may be, for example, 1 or more and 5 or less.

[0028] The hydrocarbon compound constituting the hydrocarbon sulfonate may have a substituent other than a sulfonate group. Examples of the substituent in the hydrocarbon compound include a halogen atom, an alkyl group, an aryl group such as a phenyl group, an alkyloxy group, an alkylcarbonyl group, a substituted or unsubstituted amino group, an imino group, an N-oxide group, an N-hydroxy group, a nitro group, a nitroso group, a diazo group, an azide group, an oxo group, a cyano group, a phosphino group, an S-oxide group, and a thioxo group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The alkyl group or the alkyl group in the alkyloxy group may be linear, branched, or cyclic, or a combination thereof. The number of carbon atoms in the alkyl group may be, for example, 1 to 10.

[0029] Examples of the metal element contained in the metal ion constituting the hydrocarbon sulfonate include alkali metal elements such as lithium, sodium, potassium, etc., Group 2 metal elements such as calcium, magnesium, etc., and Group 13 metal elements such as zinc, aluminum, etc. In one embodiment, the metal ion constituting the hydrocarbon sulfonate may be an alkali metal ion, and may preferably be a lithium ion or a sodium ion.

[0030] The hydrocarbyl sulfonate may contain one or more asymmetric carbon atoms or asymmetric centers in its structure. The hydrocarbyl sulfonate may have two or more optical isomers, and the hydrocarbyl sulfonate includes each optical isomer and a mixture containing these optical isomers in any ratio.

[0031] Examples of hydrocarbon sulfonic acid compounds that constitute the hydrocarbon sulfonate salt contained in the solid electrolyte are listed below, but the present invention is not limited to these.

[0032] [ka]

[0033] The hydrocarbon sulfonate may be a compound obtained by transfer or the like, or may be a compound synthesized according to a known synthesis method.

[0034] The content of the hydrocarbon sulfonate in the solid electrolyte, expressed as a molar ratio to the total number of moles of the boron compound and the hydrocarbon sulfonate, may be, for example, 0.01 or more and 0.3 or less, preferably 0.05 or more or 0.1 or more, and preferably 0.2 or less or 0.15 or less.

[0035] The solid electrolyte may be a simple mixture of a boron compound and a hydrocarbon sulfonate, or may be a solid solution of at least a portion of the boron compound and the hydrocarbon sulfonate. That is, in one embodiment, the solid electrolyte may be a solid solution of a boron compound and a hydrocarbon sulfonate.

[0036] Whether or not the boron compound and the hydrocarbon sulfonate are in a solid solution can be determined by measuring the X-ray diffraction (XRD) spectrum of the solid electrolyte. Specifically, if a peak derived from the boron compound and a peak derived from the hydrocarbon sulfonate are observed independently in the XRD, it can be determined that they are not in a solid solution. Also, if at least one of the peaks derived from the boron compound and the hydrocarbon sulfonate is not observed, or if only a weak peak is observed compared to the mixing ratio, it can be determined that at least a part of the boron compound and the hydrocarbon sulfonate are in a solid solution. The XRD spectrum is measured using, for example, CuKα radiation (λ=0.154 nm). The XRD peak derived from the boron compound can be obtained, for example, by measuring the XRD spectrum of LiCB 11 H 12 When using LiTFS, peaks are observed at 2θ = 15° to 16.5° and 2θ = 17.5° to 19°. When using LiTFS, for example, peaks due to hydrocarbon sulfonates are observed at 2θ = 19° to 20°.

[0037] The solid electrolyte exhibits high ionic conductivity. For example, the ionic conductivity of the solid electrolyte is 1.0×10 as the ionic conductivity of lithium ions at 25° C.-5 S / cm or more, preferably 1.0×10 -4 It may be S / cm or more.

[0038] Method for producing solid electrolyte The method for producing a solid electrolyte includes heat-treating a mixture containing a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonate which may have a substituent at a temperature of 60°C or higher and 300°C or lower.

[0039] M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s ] (1)

[0040] In the formula, M represents a p-valent metal ion. Each R independently represents a substituent. q represents a number from 0 to 2, r represents a number from 6 to 12, s represents a number from 0 to (r-1), t represents 0 or 1, and u represents 0 or 1.

[0041] By heat-treating a mixture containing a boron compound and a hydrocarbon sulfonate at a predetermined temperature, at least a portion of the boron compound and the hydrocarbon sulfonate are dissolved in a solid solution, thereby enabling the efficient production of a solid electrolyte exhibiting high ionic conductivity.

[0042] The details of the boron compound and the hydrocarbon sulfonate are as described above. The mixture can be prepared by mixing the boron compound and the hydrocarbon sulfonate. The mixing method is not particularly limited. Examples of the mixing method include a ball mill, a bead mill, a vibration mill, a roll mill, and a planetary ball mill. The mixture may be a pulverized product of the boron compound and the hydrocarbon sulfonate. The mixing time may be, for example, 10 hours or more, and preferably 20 hours or more or 60 hours or less.

[0043] The content of the hydrocarbon sulfonate in the mixture may be, for example, 0.01 or more and 0.3 or less, preferably 0.05 or more or 0.1 or more, and preferably 0.2 or less or 0.15 or less, in terms of the molar ratio of the hydrocarbon sulfonate to the total molar amount of the boron compound and the hydrocarbon sulfonate.

[0044] The temperature for the heat treatment of the mixture may be, for example, 50° C. or more and 300° C. or less, and preferably 60° C. or more, 100° C. or more, or 150° C. or more, and may be 250° C. or less, or 200° C. or less. The time for the heat treatment may be, for example, 1 hour or more and 20 hours or less, and preferably 3 hours or more or 15 hours or less.

[0045] The heat treatment atmosphere may be an inert gas atmosphere containing, for example, a rare gas such as nitrogen or argon. The inert gas atmosphere may have an inert gas content of, for example, 90% by volume or more, preferably 95% by volume or more, or 98% by volume or more. The heat treatment may also be carried out under a flow of inert gas.

[0046] The pressure in the atmosphere for the heat treatment may be atmospheric pressure or may be reduced pressure. The reduced pressure may be, for example, less than 10 Pa, and preferably less than 10 -4 It may be less than Pa.

[0047] The heat-treated product obtained by heat-treating the mixture may be subjected to treatments such as pulverization, dispersion, washing, filtration, classification, etc., and may be subjected to at least pulverization and classification.

[0048] The invention according to the present disclosure may include, for example, the following aspects. [1] A solid electrolyte comprising a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonate which may have a substituent. M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s ] (1)

[0049] In the formula, M represents a p-valent metal ion. Each R independently represents a substituent. q represents a number from 0 to 2, r represents a number from 6 to 12, s represents a number from 0 to (r-1), t represents 0 or 1, and u represents 0 or 1. [2] The solid electrolyte according to [1], wherein the boron compound and the hydrocarbon sulfonate are in a solid solution.

[0050] [3] The solid electrolyte according to [1] or [2], wherein the hydrocarbon sulfonate contains a ring structure selected from the group consisting of a monocyclo ring, a bicyclo ring, a tricyclo ring, and a tetracyclo ring.

[0051] [4] The solid electrolyte according to any one of [1] to [3], wherein the molar ratio of the content of the hydrocarbyl sulfonate to the total content of the boron compound and the hydrocarbyl sulfonate is 0.01 or more and 0.3 or less.

[0052] [5] The solid electrolyte according to any one of [1] to [4], wherein in formula (1), the combination of q, t, and u, (q, t, u), is (0, 0, 0), (1, 0, 1), (2, 0, 1), (2, 1, 1), or (2, 1, 0).

[0053] [6] A method for producing a solid electrolyte, comprising heat-treating a mixture containing a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonate salt which may have a substituent at a temperature of 60°C or higher and 300°C or lower. M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s ] (1)

[0054] In the formula, M represents a p-valent metal ion. Each R independently represents a substituent. q represents a number from 0 to 2, r represents a number from 6 to 12, s represents a number from 0 to (r-1), t represents 0 or 1, and u represents 0 or 1.

[0055] [7] The method for producing a solid electrolyte according to [6], wherein the hydrocarbon sulfonate contains a ring structure selected from the group consisting of a monocyclo ring, a bicyclo ring, a tricyclo ring, and a tetracyclo ring.

[0056] [8] The method for producing a solid electrolyte according to [6] or [7], wherein the mixture has a molar ratio of the content of the hydrocarbon sulfonate to the total content of the boron compound and the hydrocarbon sulfonate of 0.01 or more and 0.3 or less.

[0057] [9] The method for producing a solid electrolyte according to any one of [6] to [8], wherein in formula (1), the combination of q, t, and u, (q, t, u), is (0, 0, 0), (1, 0, 1), (2, 0, 1), (2, 1, 1), or (2, 1, 0). [Example]

[0058] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0059] Reference example 1 LiCB 11 H 12 1 / 2H2O dehydration treatment Katchem LiCB 11 H 12 Anhydrous lithium carborane salt was obtained by heating 1 / 2H2O at 200°C for 12 hours in vacuum.

[0060] Example 1 Anhydrous LiCB obtained in Reference Example 1 11 H 12 and (+)-Lithium camphor-10-sulfonate (LiCSA) were weighed out at a molar ratio of 0.9:0.1. The weighed materials were ground and mixed using a planetary ball mill (Fristch PL-7) at 400 rpm for 20 hours to obtain a mixture. The obtained mixture was heated in a vacuum at 200°C for 12 hours to obtain the solid electrolyte material of Example 1.

[0061] Example 2 A solid electrolyte material of Example 2 was obtained in the same manner as in Example 1, except that lithium trifluoromethanesulfonate (LiTFS) was used instead of lithium (+)-camphor-10-sulfonate.

[0062] Example 3 A solid electrolyte material of Example 3 was obtained in the same manner as in Example 1, except that lithium pentafluorobenzenesulfonate (LiPFBSA) was used instead of lithium (+)-camphor-10-sulfonate.

[0063] Comparative Example 1 A solid electrolyte material of Comparative Example 1 was obtained in the same manner as in Example 1, except that lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was used instead of lithium (+)-camphor-10-sulfonate.

[0064] XRD measurement The solid electrolyte material obtained above was packed into an XRD glass folder and subjected to powder XRD measurement using an X-ray diffractometer (Miniflex 600, manufactured by Rigaku Co., Ltd.). Specifically, measurements were performed using CuKα radiation (λ = 0.154 nm) at a scan speed of 10° / min and a step width of 0.02° from 2θ = 10° to 30°. The results are shown in Figure 1.

[0065] The solid electrolyte material of Example 1 was prepared by the same method as the anhydrous lithium carborane salt obtained in Reference Example 1, using LiCB 11 H 12 Only the peaks derived from LiCSA were observed. 11 H 12 It is believed that LiTFSI is solid-dissolved in the solid electrolyte of Comparative Example 1. This is believed to have significantly improved the ionic conductivity compared to other Examples. For the solid electrolyte of Comparative Example 1, a peak derived from LiTFSI was observed near 2θ=20°, which suggests that LiTFSI exists while maintaining its structure. For Example 2, a peak derived from LiTFS was observed near 2θ=19°, and for Example 3, peaks derived from LiPFBSA were similarly observed near 2θ=17° and 22°.

[0066] Ionic conductivity measurement 80 mg of the solid electrolyte material obtained above was weighed out and pressed at 140 MPa to obtain a solid electrolyte layer sample.

[0067] The solid electrolyte layer sample obtained above was measured by the AC impedance method (measurement temperature: 25°C, applied voltage: 100 mV, measurement frequency range: 120 MHz to 20 Hz) using a high-frequency impedance measurement system (Keysight Impedance Analyzer E4990A). The ionic conductivity of lithium ions was calculated from the thickness of the solid electrolyte layer sample and the resistance value on the real axis of the Cole-Cole plot. The results are shown in Table 1 and Figure 2.

[0068] [Table 1]

[0069] The results of Examples 1 to 3 and Comparative Example 1 revealed that the addition of hydrocarbon sulfonate is necessary to improve ionic conductivity. Sulfonate is a salt of a strong acid, and the ionic bond with cations (e.g., hydrogen ions and lithium ions) is relatively weak, which facilitates the dissociation of cations. The dissociated cations are converted into carborane (Li + CB 11 H 12 - ) as a carrier ion, which is thought to improve ionic conductivity.

[0070] In particular, the camphor sulfonate used in Example 1 has a certain degree of stericity, which allows the formation of carborane anions (CB 11 H 12 - This solid solution phenomenon is thought to contribute to the further improvement of ionic conductivity compared to the other hydrocarbon sulfonates used in Examples 2 and 3.

Claims

1. A solid electrolyte comprising a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonate which may have a substituent. M （２－ｕ）／ｐ [C ｑ B （ｒ－ｑ－ｔ） H （ｒ－ｑ－ｓ＋ｔ＋ｕ） R ｓ ] (1) (In the formula, M represents a p-valent metal ion; each R independently represents a substituent; q represents a number from 0 to 2; r represents a number from 6 to 12; s represents a number from 0 to (r-1); t represents 0 or 1; and u represents 0 or 1.)

2. 2. The solid electrolyte according to claim 1, wherein the boron compound and the hydrocarbon sulfonate are in a solid solution state.

3. The solid electrolyte according to claim 1 or 2, wherein the hydrocarbon sulfonate contains any one of a monocyclo ring, a bicyclo ring, a tricyclo ring, and a tetracyclo ring.

4. 3. The solid electrolyte according to claim 1, wherein the molar ratio of the content of said hydrocarbyl sulfonate to the total content of said boron compound and said hydrocarbyl sulfonate is 0.01 or more and 0.3 or less.

5. 3. The solid electrolyte according to claim 1, wherein in formula (1), (q, t, u) which is a combination of q, t, and u is (0,0,0), (1,0,1), (2,0,1), (2,1,1) or (2,1,0).

6. A method for producing a solid electrolyte, comprising heat-treating a mixture containing a boron compound having a composition represented by formula (1) and a hydrocarbon sulfonate which may have a substituent at a temperature of 60°C or higher and 300°C or lower. M （２－ｕ）／ｐ [C ｑ B （ｒ－ｑ－ｔ） H （ｒ－ｑ－ｓ＋ｔ＋ｕ） R ｓ ] (1) (In the formula, M represents a p-valent metal ion; each R independently represents a substituent; q represents a number from 0 to 2; r represents a number from 6 to 12; s represents a number from 0 to (r-1); t represents 0 or 1; and u represents 0 or 1.)

7. The method for producing a solid electrolyte according to claim 6 , wherein the hydrocarbon sulfonate contains any one of a monocyclo ring, a bicyclo ring, a tricyclo ring, and a tetracyclo ring.

8. 7. The method for producing a solid electrolyte according to claim 6, wherein the mixture has a molar ratio of the content of the hydrocarbon sulfonate to the total content of the boron compound and the hydrocarbon sulfonate of 0.01 or more and 0.3 or less.

9. 7. The method for producing a solid electrolyte according to claim 6, wherein in formula (1), (q, t, u) which is a combination of q, t, and u is (0,0,0), (1,0,1), (2,0,1), (2,1,1) or (2,1,0).

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