Solid electrolyte and method for producing the same

Abstract

This invention provides a solid electrolyte that exhibits high ionic conductivity. [Solution] A solid electrolyte comprising a first boron compound metal salt having the composition represented by formula (1) and a second boron compound metal salt having a boron-oxygen bond. In the formula, M represents a p-valent metal ion. 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. M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s (1)

Description

Technical Field

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

Background Art

[0002] All-solid-state batteries are configured to include, for example, a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode. A composition containing a carborane compound has been proposed as the solid electrolyte. For example, [HCB 11 H 11 Li] and [HCB9H9Li], which are each a type of carborane compound, have a very low Li ion conductivity at room temperature when used alone, but are said to exhibit high conductivity even at room temperature when mixed (see, for example, Non-Patent Document 1). In addition, a solid electrolyte containing a closoborate salt containing an alkali metal or an 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

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the materials of the prior art have problems such as difficulty in synthesis, and alternative materials have been demanded. Therefore, an aspect of the present disclosure aims to provide a solid electrolyte exhibiting high ionic conductivity and a method for manufacturing the same.

Means for Solving the Problem

[0006] A first aspect is a method for producing a solid electrolyte, which includes heat-treating a mixture containing a first boron compound metal salt having a composition represented by formula (1) and a second boron compound metal salt having a boron-oxygen bond at a temperature of 40°C or higher and 300°C or lower.

[0007] M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s (1)

[0008] 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.

[0009] A second aspect is a solid electrolyte containing a first boron compound metal salt having a composition represented by formula (1) and a second boron compound metal salt having a boron-oxygen bond.

[0010] M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s (1)

[0011] 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.

Advantages of the Invention

[0012] According to one aspect of the present disclosure, it is possible to provide a solid electrolyte exhibiting high ionic conductivity and a method for producing the same.

Brief Description of the Drawings

[0013] [Figure 1]This figure shows an example of the X-ray diffraction spectrum of the solid electrolyte material according to Example 1. [Figure 2] This figure shows an example of the X-ray diffraction spectrum of the solid electrolyte material according to Example 2. [Figure 3] This figure shows an example of the X-ray diffraction spectrum of the solid electrolyte material according to Example 3. [Figure 4] This figure shows an example of the X-ray diffraction spectrum of a solid electrolyte material related to Comparative Example 1. [Figure 5] This figure shows an example of the 11B nuclear magnetic resonance spectrum of the solid electrolyte material according to Example 1. [Figure 6] This figure shows an example of thermogravimetric-differential thermal analysis of a solid electrolyte material. [Modes for carrying out the invention]

[0014] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved. Furthermore, the content of each component in a composition refers to the total amount of multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component exist in the composition. In addition, the upper and lower limits of the numerical ranges described herein can be arbitrarily selected and combined from the numerical values ​​exemplified as numerical ranges. Embodiments of the present invention will now be described in detail. However, the embodiments shown below are illustrative examples of solid electrolytes and methods for producing the same 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.

[0015] solid electrolyte The solid electrolyte comprises a first boron compound metal salt having a composition represented by the following formula (1), and a second boron compound metal salt having a boron-oxygen bond.

[0016] M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s (1)

[0017] 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.

[0018] Solid electrolytes can exhibit high ionic conductivity by containing a first boron compound metal salt and a second boron compound metal salt having specific compositions. This can be explained, for example, as follows: Carborane compounds are known to undergo a change in crystal structure at a certain temperature, resulting in a structural phase transition from a low-temperature phase to a high-temperature phase, which dramatically increases their ionic conductivity. Since the elements forming the first and second boron compound metal salts are similar, their electronegativity is close, and it is presumed that solid solution occurs easily. It is thought that solid solution of the first and second boron compound metal salts, which are carborane compounds, enables a structural phase transition at a lower temperature, thereby improving ionic conductivity.

[0019] Compounds having the composition represented by formula (1) are boron clusters with a high amount of boron hydride (borane) or salts of their carbon-substituted derivatives, and the anionic portion has a closed-shell cavity three-dimensional structure consisting of polyhedra. In formula (1), anions containing carbon are collectively called carborane anions.

[0020] In formula (1), examples of metal elements that form a p-valent metal ion represented by M include 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, preferably 1 or 2, or 1. In one embodiment, M may be an alkali metal ion, preferably a lithium ion or a sodium ion.

[0021] Examples of substituents represented by R in formula (1) include halogen atoms. The halogen atom represented by R may include at least one selected from the group consisting of fluorine, chlorine, bromine, and iodine atoms. The substituents represented by R may be the same or may be different from each other.

[0022] q represents a number from 0 to 2, preferably 1 or 2, or may be 1. r represents a number from 6 to 12, preferably 10 or 12, or may be 12. s represents a number from 0 to (r-1), preferably 0 to 1, or may be 0. t represents 0 or 1, preferably 0. u represents 0 or 1, preferably 0.

[0023] 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, a boron compound having the composition represented by formula (1) may be a compound represented by any of the following formulas (1a) to (1e).

[0024] 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)

[0025] The first boron compound metal salt having the composition represented by formula (1) may be obtained by means of acquisition or other means, or it may be synthesized as a desired first boron compound metal salt according to known synthesis methods.

[0026] A second boron compound metal salt is a metal salt of a boron compound having a boron-oxygen bond. Examples of metal salts of boron compounds having a boron-oxygen bond include bis(oxalate)borate, borate, metaborate, polyborate, phenylborate, borosilicate, and borate. Here, polyborate includes, for example, tetraborate, triborate, and pentaborate. A second boron compound metal salt may contain at least one selected from the group consisting of bis(oxalate)borate, borate (orthoborate), metaborate, polyborate, phenylborate, borosilicate, and borate, and may contain at least one selected from the group consisting of bis(oxalate)borate, borate, and metaborate. A second boron compound metal salt may contain at least bis(oxalate)borate.

[0027] Examples of metal elements included in the metal ions constituting the second boron compound metal salt include 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. In one embodiment, the metal ions constituting the second boron compound metal salt may be alkali metal ions, preferably lithium ions or sodium ions.

[0028] Examples of metal salts of the second boron compound contained in solid electrolytes are given below, but the present invention is not limited to these. In the following, M is used as the metal ion. + The example given is a monovalent metal ion represented by , but the valency of metal ions is not limited to monovalent.

[0029] [ka]

[0030] The second boron compound metal salt may be obtained through acquisition or other means, or it may be synthesized according to known synthesis methods to obtain the desired compound.

[0031] The content of the second boron compound metal salt in the solid electrolyte may be, for example, 0.01 or more and 0.5 or less as a molar ratio to the total number of moles of the first boron compound metal salt and the second boron compound metal salt, preferably 0.05 or more, or 0.1 or more, and preferably 0.3 or less, 0.2 or less, or 0.15 or less.

[0032] The solid electrolyte may be a simple mixture of the first boron compound metal salt and the second boron compound metal salt, or at least a portion of the first boron compound metal salt and the second boron compound metal salt may be in solid solution. That is, in one embodiment, the solid electrolyte may be a solid solution of the first boron compound metal salt and the second boron compound metal salt.

[0033] Whether a solid solution exists between the first and second boron compound metal salts can be determined by measuring the X-ray diffraction (XRD) spectrum of the solid electrolyte. Specifically, if peaks originating from the first boron compound metal salt and peaks originating from the second boron compound metal salt are observed independently in the XRD spectrum, it can be determined that the solid solution does not exist. Furthermore, if at least one of the peaks originating from the first or second boron compound metal salt is not observed, or if only a weak peak is observed relative to the mixing ratio, it can be determined that at least a portion of the solid solution exists. The XRD spectrum is measured using, for example, CuKα rays (λ=0.154nm). Note that the XRD peak originating from the first boron compound metal salt is, for example, LiCB 11 H 12 When using this method, peaks are observed between 2θ=15° and 16.5° and between 2θ=17.5° and 19°. Furthermore, if peaks originating from the second boron compound metal salt are observed, they will appear at the same positions as the elemental second boron compound metal salt.

[0034] Solid electrolytes exhibit high ionic conductivity. The ionic conductivity of a solid electrolyte is, for example, 1.0 × 10⁻⁶, as the ionic conductivity of lithium ions at 80°C. -3 It may be S / cm or more, preferably 1.0 × 10 -2 It may be S / cm or higher.

[0035] Method for producing solid electrolytes A method for producing a solid electrolyte involves heat-treating a mixture containing a first boron compound metal salt having a composition represented by the following formula (1) and a second boron compound metal salt having a boron-oxygen bond at a temperature of 40°C to 300°C.

[0036] M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s (1)

[0037] 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.

[0038] By heat-treating a mixture containing a first boron compound metal salt and a second boron compound metal salt at a predetermined temperature, at least a portion of the first boron compound metal and the second boron compound metal salt become solidly dissolved, thereby efficiently producing a solid electrolyte exhibiting high ionic conductivity.

[0039] Details of the first boron compound metal salt and the second boron compound metal salt are as previously described. The mixture can be prepared by mixing the first boron compound metal salt and the second boron compound metal salt. The mixing method is not particularly limited. Examples of mixing methods include ball mills, bead mills, vibratory mills, roll mills, planetary ball mills, etc., and these may be carried out dry or wet. The mixture may be a pulverized product of the first boron compound metal salt and the second boron compound metal salt. The mixing time may be, for example, 10 hours or more, preferably 20 hours or more, or 60 hours or less. Alternatively, the first boron compound metal salt and the second boron compound metal salt may be dissolved in a solvent such as water or ethanol, and the solvent may be removed by evaporator, vacuum drying, etc., and a simple and homogeneous mixture may be obtained by drying.

[0040] The content of the second boron compound metal salt in the mixture may be, for example, 0.01 or more and 0.5 or less as the molar ratio of the second boron compound metal salt to the total molar amount of the first boron compound metal salt and the second boron compound metal salt, preferably 0.05 or more, or 0.1 or more, and preferably 0.3 or less, 0.2 or less, or 0.15 or less.

[0041] The heat treatment temperature of the mixture may be, for example, 40°C to 300°C, preferably 60°C to 100°C, 150°C to 150°C, 250°C to 250°C, or 200°C to 250°C. The heat treatment time may be, for example, 1 hour to 20 hours, preferably 3 hours to 15 hours.

[0042] The heat treatment atmosphere may be an inert gas atmosphere containing noble gases such as nitrogen or argon. The inert gas atmosphere may have an inert gas content of 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 the flow of inert gas. Heat treatment in an inert gas atmosphere is expected to prevent oxidation of the material by oxygen.

[0043] The pressure in the heat treatment atmosphere may be atmospheric pressure or reduced pressure. For example, the reduced pressure may be less than 10 Pa, preferably 10 Pa. -4 The pressure may be less than Pa. Heat treatment under reduced pressure is expected to prevent material degradation caused by side reactions, such as those caused by impurities like moisture.

[0044] The heat-treated product obtained by heat treatment of the mixture may be subjected to processes such as grinding, dispersion, washing, filtration, and classification, and at least grinding and classification may be performed.

[0045] The invention relating to this disclosure may encompass, for example, the following embodiments: [1] A method for producing a solid electrolyte, comprising heat-treating a mixture containing a first boron compound metal salt having a composition represented by formula (1) and a second boron compound metal salt having a boron-oxygen bond at a temperature of 40°C to 300°C. M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s (1)

[0046] 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.

[0047] [2] The method for producing a solid electrolyte according to [1], wherein the second boron compound metal salt comprises at least one selected from the group consisting of bis(oxalate)borate, borate, metaborate, polyborate, phenylborate, borosilicate, borate, and trimethylborate.

[0048] [3] The method for producing a solid electrolyte according to [1] or [2], wherein the molar ratio of the content of the second boron compound metal salt to the total content of the first boron compound metal salt and the second boron compound metal is 0.01 or more and 0.5 or less.

[0049] [4] A method for producing a solid electrolyte according to any one of [1] to [3], 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).

[0050] A solid electrolyte comprising a first boron compound metal salt having a composition represented by formula (1) and a second boron compound metal salt having a boron-oxygen bond. M (2-u) / p [C q B (r-q-t) H (r-q-s+t+u) R s (1)

[0051] 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.

[0052] [6] The solid electrolyte according to [5], wherein the first boron compound metal salt and the second boron compound metal salt are in solid solution.

[0053] [7] The solid electrolyte according to [5] or [6], wherein the second boron compound metal salt comprises at least one selected from the group consisting of bis(oxalate)borate, borate, metaborate, polyborate, phenylborate, borosilicate, borate, and trimethylborate.

[0054] [8] The solid electrolyte according to any one of [5] to [7], wherein the molar ratio of the content of the second boron compound metal salt to the total content of the first boron compound metal salt is 0.01 or more and 0.5 or less.

[0055] [9] The solid electrolyte according to any one of [5] 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). [Examples]

[0056] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0057] Reference example LiCB 11 H 12 • 1 / 2H2O dehydration process Carborane compound LiCB 11 H 12 1 / 2H2O (Katchem) 5.0 × 10 -4 By heating under reduced pressure below Pa at 200°C for 12 hours, a reference example solid electrolyte material in an anhydrous state was obtained.

[0058] Example 1 The anhydrous LiCB obtained above 11 H 12 And Li3BO3 (trilithium borate; manufactured by Toyoshima Seisakusho) in a molar ratio of 0.9:0.1 (LiCB 11 H 12 The material was weighed to the ratio Li3BO3. The weighed material was ground and mixed using a planetary ball mill (Fristch PL-7) at 400 rpm for 20 hours to obtain a mixture. The resulting mixture was 5.0 × 10 -4 The solid electrolyte material of Example 1 was obtained by heating at 200°C for 12 hours under reduced pressure of less than Pa.

[0059] Example 2 The solid electrolyte material of Example 2 was obtained in the same manner as in Example 1, except that LiBO2 (lithium metaborate; manufactured by Sigma-Aldrich) was used instead of Li3BO3.

[0060] Example 3 The solid electrolyte material of Example 3 was obtained in the same manner as in Example 1, except that LiBOB (lithium bisoxalate borate; manufactured by Sigma-Aldrich) was used instead of Li3BO3.

[0061] Comparative Example 1 A solid electrolyte material for Comparative Example 1 was obtained in the same manner as in Example 1, except that LiTFSI (lithium bis(trifluoromethanesulfonyl)imide; manufactured by Kishida Chemical Co., Ltd.) was used instead of Li3BO3.

[0062] Composition analysis The composition of each of the solid electrolyte materials obtained above was analyzed as follows.

[0063] Boron (B) analysis 50 mg to 100 mg of solid electrolyte material were accurately weighed and subjected to acid decomposition to obtain analytical samples. The mass ratio (mass%) of boron contained in the solid electrolyte material was determined using a high-frequency inductively coupled plasma (ICP) emission spectrometer. The results are shown in Table 1.

[0064] Lithium (Li) analysis 50 mg to 100 mg of solid electrolyte material were accurately weighed and subjected to acid decomposition to obtain analytical samples. The mass ratio (mass%) of lithium contained in the solid electrolyte material was determined using atomic absorption spectroscopy. The results are shown in Table 1.

[0065] Carbon (C) and hydrogen (H) analysis Approximately 1 mg of solid electrolyte material was precisely weighed using a microbalance. The weighed sample was then thermally decomposed at 1150°C using a CHN trace organic element analyzer. The resulting carbon dioxide and water were quantified, and the mass ratios (mass%) of carbon and hydrogen in the sample were determined. The results are shown in Table 1. The compositional formula obtained based on the compositional analysis is also shown in Table 1.

[0066] [Table 1]

[0067] Ionic conductivity measurement 80 mg of the solid electrolyte material obtained above was weighed and pressed at a pressure of 140 MPa to obtain solid electrolyte layer samples.

[0068] The solid electrolyte layer samples obtained above were measured using a high-frequency impedance measurement system (Keysight E4990A impedance analyzer) with the AC impedance method (measurement temperature: 80°C, applied voltage: 100mV, measurement frequency range: 120MHz to 20Hz). The ionic conductivity σ (S / cm) 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 2.

[0069] [Table 2]

[0070] LiCB 11 H 12 Compared to the reference example solid electrolyte material consisting only of [specific components], the solid electrolyte materials obtained in Examples 1 to 3 showed significantly improved ionic conductivity at 80°C. The solid electrolyte material of Comparative Example 1, which used LiTFSI as the added salt, showed a lower ionic conductivity than the reference example. Furthermore, when the ionic conductivity of each of the added salts, Li3BO3, LiBO2, LiBOB, and LiTFSI, was measured individually, they all showed ionic conductivity below the detection limit.

[0071] Thermogravimetric-differential thermal analysis (TG-DTA) measurement Thermogravimetric-differential thermal analysis was performed on the solid electrolyte materials obtained above under the following conditions. The results are shown in Figure 6. Analyzer: Rigaku TG-DTA8122 / Thermo plus EVO2 Measurement conditions: The temperature was increased to 300°C at a rate of 10°C / min under a flow of 100 mL / min of Ar gas.

[0072] LiCB 11 H 12 In the reference example solid electrolyte material consisting only of [material name], a downward DTA peak due to an endothermic reaction was observed around 120°C to 130°C. In contrast, it was confirmed that a similar DTA peak was observed around 95°C in the solid electrolyte materials of Examples 1 and 2. LiCB 11 H12 It is known that a structural phase transition from a low-temperature phase to a high-temperature phase occurs between 120°C and 130°C, resulting in a rapid increase in ionic conductivity. From these results, it is thought that the solid solution of the first boron compound metal salt and the second boron compound metal salt, which are carborane compounds, enables a structural phase transition at a lower temperature, leading to an improvement in ionic conductivity at 80°C.

[0073] X-ray diffraction (XRD) spectral measurement The solid electrolyte materials obtained above were packed into XRD glass folders, and powder XRD measurements were performed using an X-ray diffraction analyzer (Miniflex600, Rigaku). Specifically, measurements were performed using CuKα rays (λ=0.154nm) at 2θ=20° to 60° with a scan speed of 10° / min and a step width of 0.02°. The results for the solid electrolyte material of Example 1 are shown in Figure 1, the results for the solid electrolyte material of Example 2 are shown in Figure 2, the results for the solid electrolyte material of Example 3 are shown in Figure 3, and the results for the solid electrolyte material of Comparative Example 1 are shown in Figure 4. In each figure, LiCB 11 H 12 The XRD graphs for the individual components, the individual added salts, and the mixture are shown separately.

[0074] In Figure 1, the peak for the added Li3BO3 disappeared; in Figure 2, the peak for LiBO2 disappeared; and in Figure 3, the peak for LiBOB disappeared. This suggests that in the example, the added boron compound salt was a carborane compound (LiCB). 11 H 12 It is thought to be in solid solution in ). On the other hand, in the case of the solid electrolyte material of Comparative Example 1, it was observed that the peak derived from the added salt LiTFSI remained unchanged.

[0075] NMR measurement About solid electrolyte materials 11 1B-NMR measurements were performed. 11B-NMR measurements were performed using a nuclear magnetic resonance spectrometer (JNM-ECA500; manufactured by JEOL Ltd.). The measurement conditions were set to a resonance frequency of 192.43 MHz and a pulse width of 11.3 μs. The results for the solid electrolyte material of Example 1 are shown in Figure 5.

[0076] In Figure 5, LiCB is located at -7.967, -13.821, and -15.999 ppm. 11 H 12 A peak originating from the substance was observed, specifically a peak at +1.378 ppm originating from Li3BO3.

Claims

1. A method for producing a solid electrolyte, comprising heat-treating a mixture containing a first boron compound metal salt having a composition represented by formula (1) and a second boron compound metal salt having a boron-oxygen bond at a temperature of 40°C to 300°C. 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. R represents each substituent independently. 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 method for producing a solid electrolyte according to claim 1, wherein the second boron compound metal salt comprises at least one selected from the group consisting of bis(oxalic acid) borate, borate, metaborate, polyborate, phenylborate, borosilicate, and borate.

3. The method for producing a solid electrolyte according to claim 1 or 2, wherein the molar ratio of the content of the second boron compound metal salt to the total content of the first boron compound metal salt and the second boron compound metal is 0.01 or more and 0.5 or less.

4. A method for producing a solid electrolyte according to claim 1 or 2, 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).

5. A solid electrolyte comprising a first boron compound metal salt having a composition represented by formula (1) and a second boron compound metal salt having a boron-oxygen bond. 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. R represents each substituent independently. 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.)

6. The solid electrolyte according to claim 5, wherein the first boron compound metal salt and the second boron compound metal salt are in a solid solution.

7. The solid electrolyte according to claim 5 or 6, wherein the second boron compound metal salt comprises at least one selected from the group consisting of bis(oxalic acid) borate, borate, metaborate, polyborate, phenylborate, borosilicate, and borate.

8. The solid electrolyte according to claim 5 or 6, wherein the molar ratio of the content of the second boron compound metal salt to the total content of the first boron compound metal salt is 0.01 or more and 0.5 or less.

9. The solid electrolyte according to claim 5 or 6, 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).

Images