Solid electrolytes and batteries

Abstract

This solid electrolyte contains: a binder polymer; a compound with high dielectric constant; a metal salt; and lithium bis(oxalato)borate.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte and a battery.

Background Art

[0002] Unlike liquid electrolytes, solid electrolytes are electrolyte membranes that are free from the risk of liquid leakage, lightweight, and flexible. Therefore, solid electrolytes are expected to be applied to secondary batteries and the like using lithium ions and the like. As typical solid electrolytes, polyether-based electrolytes, polycarbonate-based electrolytes, and the like have been extensively studied. Further, for example, Patent Document 1 proposes a solid electrolyte containing a copolymer containing both an ether structural unit and a carbonate structural unit and a metal salt.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the solid electrolyte described in Patent Document 1, a certain degree of high ionic conductivity can be achieved. However, further improvement in ionic conductivity is required. And it has been studied to improve the ionic conductivity by adding a high dielectric constant compound to the binder polymer and the metal salt. However, when this high dielectric constant compound is added, there is a problem that the oxidation initiation potential decreases in the voltage stability evaluation, leading to a decrease in oxidation resistance.

[0005] An object of the present invention is to provide a solid electrolyte and a battery having high ionic conductivity and sufficient oxidation resistance.

Means for Solving the Problems

[0006] According to one aspect of the present invention, a solid electrolyte is provided comprising a binder polymer, a high dielectric constant compound, a metal salt, and lithium bisoxalate borate.

[0007] In a solid electrolyte according to one aspect of the present invention, it is preferable that the relative permittivity of the high dielectric constant compound at a frequency of 1 kHz is 30 or more.

[0008] In a solid electrolyte according to one aspect of the present invention, the high dielectric constant compound is preferably at least one selected from the group consisting of cyclic carbonate compounds, linear carbonate compounds, cyclic carboxylic acid ester compounds, linear carboxylic acid ester compounds, cyclic ether compounds, linear ether compounds, phosphate ester compounds, nitrile compounds, amide compounds, sulfone compounds, and sulfolane compounds.

[0009] In a solid electrolyte according to one aspect of the present invention, the high dielectric constant compound is preferably at least one selected from the group consisting of cyclic carbonate compounds and nitrile compounds.

[0010] In a solid electrolyte according to one aspect of the present invention, it is preferable that the metal salt is an alkali metal salt.

[0011] In a solid electrolyte according to one aspect of the present invention, the alkali metal salt is preferably a lithium salt.

[0012] In a solid electrolyte according to one aspect of the present invention, it is preferable that the content of lithium bisoxalate borate is 0.1% by mass or more and 5% by mass or less based on the total amount of the solid electrolyte.

[0013] In a solid electrolyte according to one aspect of the present invention, it is preferable that the content of lithium bisoxalate borate is 0.5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the high dielectric constant compound.

[0014] In one aspect of the present invention, it is preferable that the solid electrolyte preparation solution containing the binder polymer or the raw material for the binder polymer, the high dielectric constant compound, the metal salt, and the lithium bisoxalate borate is cast.

[0015] According to one aspect of the present invention, a battery comprising a solid electrolyte according to the said aspect of the present invention is provided.

[0016] According to one aspect of the present invention, a solid electrolyte and a battery having high ionic conductivity and sufficient oxidation resistance can be provided. [Modes for carrying out the invention]

[0017] [Solid electrolyte] The present invention will be described below with reference to embodiments. The present invention is not limited to the content of these embodiments. The solid electrolyte according to this embodiment includes a binder polymer described below, a high dielectric constant compound described below, a metal salt described below, and lithium bisoxalate borate. In the solid electrolyte according to this embodiment, by using a high dielectric constant compound and lithium bisoxalate borate in combination, it is possible to achieve both ionic conductivity and oxidation resistance. The inventors surmise the reason for this as follows. Adding a high dielectric constant compound to a binder polymer and a metal salt can improve ionic conductivity, but simultaneously reduce oxidation resistance. However, by using this high dielectric constant compound in combination with lithium bisoxalate borate (hereinafter also referred to as "LiBOB"), it is possible to improve ionic conductivity while maintaining oxidation resistance. Furthermore, while LiBOB generally has poor dissociation properties and is difficult to dissolve in polymer electrolytes, using a high dielectric constant compound in combination with LiBOB can promote the dissociation of LiBOB, allowing it to dissolve in solid electrolytes. Thus, the inventors surmise that this embodiment makes it possible to achieve both high ionic conductivity and oxidation resistance.

[0018] (Binder polymer) The binder polymer according to this embodiment can be any of those conventionally used in polymer electrolytes without particular limitation. Examples of such binder polymers include ester-based polymers, carbonate-based polymers, vinylidene fluoride-based polymers, acrylonitrile-based polymers, styrene-based polymers, (meth)acrylate-based polymers, urethane acrylate-based polymers, (meth)acrylamide-based polymers, N-vinylamide-based polymers, alkyl vinyl ether-based polymers, ether-based polymers, and siloxane-based polymers. These binder polymers may be homopolymers or copolymers. Further, these binder polymers may be used individually or in combination of two or more kinds. Among these binder polymers, at least one selected from the group consisting of carbonate-based polymers and (meth)acrylate-based polymers is preferable from the viewpoints of ionic conductivity and oxidation resistance.

[0019] Examples of the carbonate-based polymer include those containing a structural unit represented by the following general formula (1) (hereinafter sometimes referred to as a carbonate unit) and a structural unit represented by the following general formula (2) (hereinafter sometimes referred to as an ether unit). With such a copolymer, it is possible to achieve both ionic conductivity and cation transference number.

[0020]

Chemical formula

[0021] In general formula (1), m is 2 or 3, and R 1 is independently a hydrogen atom or a methyl group. Also, a plurality of R 1 may be the same as or different from each other. In this embodiment, from the viewpoints of ease of synthesis and improvement of ionic conductivity, m is preferably 2. Also, from the viewpoints of ease of synthesis and improvement of ionic conductivity, R 1 is preferably a hydrogen atom.

[0022] [ka]

[0023] In general formula (2), n is 2 or 3, and R 2 Each of these is independently either a hydrogen atom or a methyl group. Also, multiple R 2 They may be the same or different from one another. In this embodiment, from the viewpoint of ease of synthesis and improvement of ionic conductivity, n is preferably 2. Also, from the viewpoint of ease of synthesis and improvement of ionic conductivity, R 2 It is preferable that it is a hydrogen atom.

[0024] When the molecular weight of the binder polymer is expressed as weight-average molecular weight (Mw), it is preferably 5,000 to 5,000,000, and more preferably 10,000 to 1,000,000, based on standard polystyrene measured by gel permeation chromatography (GPC). Furthermore, when expressed in terms of number-average molecular weight (Mn), it is preferable that it be between 3,000 and 3,000,000, and more preferably between 5,000 and 500,000. Furthermore, the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) is preferably 1 or more and 10 or less, and more preferably 1.1 or more and 5 or less.

[0025] The binder polymer content is preferably 5% by mass or more and 60% by mass or less, and more preferably 10% by mass or more and 50% by mass or less, based on the total amount of the solid electrolyte. Within the above range of binder polymer content, a film-like solid electrolyte can be produced.

[0026] (High dielectric constant compounds) The high dielectric constant compound according to this embodiment is a compound having a high dielectric constant. The relative dielectric constant of this high dielectric constant compound at a frequency of 1 kHz is preferably 30 or higher, and more preferably 35 or higher. The high dielectric constant compound is preferably liquid at 25°C. Furthermore, from the viewpoint of retaining the compound in the solid electrolyte, the boiling point of the high dielectric constant compound is preferably 80°C or higher, more preferably 100°C or higher, and particularly preferably 120°C.

[0027] Examples of high dielectric constant compounds include cyclic carbonate compounds, linear carbonate compounds, cyclic carboxylic acid ester compounds, linear carboxylic acid ester compounds, cyclic ether compounds, linear ether compounds, phosphate ester compounds, nitrile compounds, amide compounds, sulfone compounds, and sulfolane compounds. These high dielectric constant compounds may be used individually or in combination of two or more. Among these high dielectric constant compounds, at least one selected from the group consisting of cyclic carbonate compounds and nitrile compounds is preferred from the viewpoint of having a high dielectric constant.

[0028] Examples of cyclic carbonate compounds include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, and 2,3-pentylene carbonate. Examples of chain-like carbonate compounds include methyl ethyl carbonate (MEC), diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate.

[0029] Examples of cyclic carboxylic acid ester compounds include α-acetolactone and ε-caprolactone. Examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.

[0030] Examples of cyclic ether compounds include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane and 1,4-dioxane, 4-methyldioxolane, 3,5-dimethylisoxazole, 2,5-dimethylfuran, furan, 2-methylfuran, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of chain-like ether compounds include dimethyl ether, diethyl ether, dibutyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and triethylene glycol diethyl ether.

[0031] Examples of phosphate ester compounds include trimethyl phosphate, triethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, tripropyl phosphate, tributyl phosphate, tri(trifluoromethyl) phosphate, tri(trichloromethyl) phosphate, tri(trifluoroethyl) phosphate, tri(triperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphosphoran-2-one, 2-trifluoroethoxy-1,3,2-dioxaphosphoran-2-one, and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one.

[0032] Examples of nitrile compounds include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitride, cyclohexanecarbonitride, acrylonitrile, methacrylonitrile, crotononitrile, malononitrile, succinonitrile, glutalonitrile, adiponitrile, pimeronitrile, cyclohexanetricarbonitride, triscyanoethylamine, triscyanoethoxypropane, tricyanoethylene, pentanetricarbonitride, propanetricarbonitride, and heptanetricarbonitride.

[0033] Examples of amide compounds include N,N-dimethylformamide (DMF). Examples of sulfone compounds include dimethyl sulfone and diethyl sulfone. Examples of sulfolane compounds include sulfolanes.

[0034] The content of the high dielectric constant compound is preferably 10% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 50% by mass or less, based on the total amount of the solid electrolyte. Within the above range of the content of the high dielectric constant compound, a film-like solid electrolyte can be produced.

[0035] (Metal salts) The metal salt according to this embodiment is not particularly limited, but for example, at least one of the alkali metal salts can be used. Examples of alkali metal salts include lithium salts, sodium salts, and potassium salts.

[0036] In this embodiment, the metal salt is more preferably a lithium salt. In the solid electrolyte, the metal salt can exist as a cation such as an alkali metal and as a counterion of said cation. If the metal salt is a lithium salt, the energy density will be higher. Examples of lithium salts include LiClO4, LiBF4, LiI, LiPF6, LiCF3SO3, LiCF3COO, LiNO3, LiAsF6, LiSbF6, LiAlCl4, LiCl, LiBr, LiB(C2H5)4, LiCH3SO3, LiC4F9SO3, Li(CF3SO2)2N, Li(C2F5SO2)N, and Li(FSO2)2N. Among these, from the viewpoint of ionic conductivity, it is more preferable to include at least one of Li(CF3SO2)2N (lithium bis(trifluoromethanesulfonyl)imide: LiTFSI) and Li(FSO2)2N (lithium bis(fluorosulfonyl)imide: LiFSI). Multiple types of metal salts may be included in the solid electrolyte.

[0037] The metal salt content is preferably 10% to 70% by mass, and more preferably 20% to 60% by mass, based on the total amount of the solid electrolyte. If the metal salt content is above the lower limit, the ionic conductivity can be improved. On the other hand, if the metal salt content is below the upper limit, the salt can be sufficiently dissolved, thus suppressing salt precipitation.

[0038] (Lithium bisoxalate borate) In this embodiment, by using the aforementioned high dielectric constant compound and lithium bisoxalate borate in combination, it is possible to improve ionic conductivity while maintaining oxidation resistance.

[0039] The lithium bisoxalate borate content is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.2% by mass or more and 3% by mass or less, based on the total volume of the electrolyte preparation solution.

[0040] The lithium bisoxalate borate content is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.2% by mass or more and 3% by mass or less, based on the total amount of the solid electrolyte. If the lithium bisoxalate borate content is above the lower limit, oxidation resistance can be improved. On the other hand, if the lithium bisoxalate borate content is below the upper limit, the salt can be sufficiently dissolved, and thus salt precipitation can be suppressed. Furthermore, from a similar viewpoint, the content of lithium bisoxalate borate per 100 parts by mass of the high dielectric constant compound is preferably 0.5 parts by mass or more and 50 parts by mass or less, and more preferably 1 part by mass or more and 30 parts by mass or less.

[0041] The solid electrolyte according to this embodiment may contain components other than the binder polymer, high dielectric constant compound, metal salt, and lithium bisoxalate borate according to this embodiment, as long as the objectives of the present invention are not impaired.

[0042] For example, the solid electrolyte according to this embodiment may contain fillers or other additives. Examples of fillers include talc, kaolin, clay, calcium silicate, alumina, zirconia, zinc oxide, antimony oxide, indium oxide, tin oxide, titanium oxide, iron oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, silica, calcium carbonate, potassium titanate, barium titanate, mica, montmorillonite, and glass fibers. Among these, it is preferable to include at least one of alumina, zirconia, magnesium oxide, and barium titanate.

[0043] The method for producing the solid electrolyte according to this embodiment is not particularly limited. For example, a binder polymer may be obtained by polymerizing monomers and then incorporating a metal salt, or a binder polymer may be formed by polymerizing monomers (raw material monomers for the binder polymer) in the presence of a metal salt. In the former method, for example, a high dielectric constant compound, a metal salt, lithium bisoxalate borate, and a solvent as needed are added to the binder polymer according to this embodiment and dissolved. Then, the solution is cast onto the surface of a support to form a coating film and dried to obtain the solid electrolyte. In the latter method, for example, a photoinitiator, a high dielectric constant compound, a metal salt, lithium bisoxalate borate, and a solvent as needed are added to the raw material monomers for the binder polymer according to this embodiment and dissolved. Then, the raw material monomers are polymerized by ultraviolet irradiation to form a binder polymer, thereby obtaining the solid electrolyte.

[0044] The form or configuration of the solid electrolyte according to this embodiment is not particularly limited. For example, it may be a membrane-like solid electrolyte membrane. The solid electrolyte membrane is preferably self-supporting. A self-supporting solid electrolyte membrane is easy to handle. A self-supporting membrane is a membrane that can be peeled from the support while maintaining its shape and can be handled. A solid electrolyte membrane can be manufactured as follows. For example, an electrolyte preparation solution containing a high dielectric constant compound, a metal salt, and lithium bisoxalate borate, and optionally a solvent, is prepared using the binder polymer according to this embodiment. This electrolyte preparation solution is then cast onto the surface of a support to form a coating film, and the solution in the coating film is dried to obtain a film-like solid electrolyte membrane. In this case, if it is necessary to peel the solid electrolyte membrane from the support, it is preferable that the surface of the support is treated with a peeling treatment.

[0045] [battery] The battery according to this embodiment includes a solid electrolyte according to this embodiment. In this embodiment, it is preferable to include the solid electrolyte according to this embodiment as a constituent material of the electrolyte layer of the battery. The battery consists of an anode, a cathode, and an electrolyte layer disposed between the anode and the cathode. With such a configuration, a battery with excellent characteristics can be obtained. Furthermore, the battery is preferably a secondary battery, and more preferably a lithium-ion secondary battery. Alternatively, an electrolyte preparation solution containing a high dielectric constant compound, a metal salt, and lithium bisoxalate borate, as well as a solvent as needed, may be cast onto the electrode to form a solid electrolyte film directly on the electrode. The various components of the lithium-ion secondary battery according to this embodiment are not particularly limited, but for example, materials commonly used in batteries can be used. Furthermore, the solid electrolyte according to this embodiment has ionic conductivity even without containing a solvent. Therefore, if the battery according to this embodiment is made to contain the solid electrolyte according to this embodiment but without a solvent, it can be used safely without leakage.

[0046] Furthermore, the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. [Examples]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The measurements or evaluations in the following examples and comparative examples were performed by the methods described below.

[0048] [Ionic conductivity measurement] The obtained solid electrolyte membrane was cut into a 6 mm diameter circle and sandwiched between two stainless steel plates as electrodes. The impedance between the stainless steel plates was measured. For the measurement, the AC impedance method was used, which involves applying AC (applied voltage of 10 mV) between the electrodes to measure the resistance component. The ionic conductivity was calculated from the real impedance intercept of the resulting Cole-Cole plot. A potentiostat / galvanostat (SP-150, BioLogic) was used for the measurement. The ionic conductivity (σ) was determined by the following formula (F1). σ = L / (R×S) ···(F1) In equation (F3), σ is ionic conductivity (unit: S / cm), R is resistance (unit: Ω), and S is the cross-sectional area of ​​the solid electrolyte membrane at the time of measurement (unit: cm²). 2 ), L indicates the distance between electrodes (unit: cm). The measurement temperatures were 25°C and 60°C. Ionic conductivity (σ) was calculated from the complex impedance measurement results.

[0049] [Voltage Stability Evaluation] The voltage stability (oxidation initiation potential) of a solid electrolyte was evaluated using the Linear Sweep Voltammetry (LSV) method. A BioLogic VMP3 was used for the measurements. A coin cell was fabricated by contacting one side of the solid electrolyte membrane of the sample with a lithium metal electrode and the other side with a SUS substrate, and measurements were taken under the following conditions. Voltage range: 3~6V Scanning speed: 1 mV / s Temperature: 25℃

[0050] [Example 1] (Synthesis of polymerization catalysts) 1.33 g of potassium hexacyanocobalt(III) (K3[Co(CN)6], manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 20 mL of deionized water and added dropwise over 45 minutes to a 50°C ZnCl2 solution (11.42 g of ZnCl2 dissolved in a mixed solution of 60 mL of deionized water and 30 mL of t-butyl alcohol) that had been vigorously stirred. The mixture was then vigorously stirred for 60 minutes. The resulting white suspension was centrifuged at 5,000 rpm to isolate the white solid. The isolated white solid was resuspended in a solution of t-butyl alcohol and deionized water (volume ratio: t-butyl alcohol:deionized water = 5:5) with vigorous stirring for 30 minutes. Subsequently, the amount of t-butyl alcohol relative to water was gradually increased (volume ratio: t-butyl alcohol:deionized water changed from 6:4 to 7:3, 8:2, and 9:1), and isolation by centrifugation and resuspension were repeated several times. Finally, the white solid was resuspended in t-butyl alcohol and isolated by centrifugation. The DMC catalyst:Zn3(Co[CN]6)2 was then obtained by drying at 50°C under vacuum until a constant weight was reached.

[0051] (Synthesis of ethylene oxide-ethylene carbonate copolymer) 5 mg of DMC catalyst was weighed out for 5 mL of monomer and stirred in a pressure vessel. All of these operations were performed under an argon atmosphere inside the pressure vessel. Subsequently, the pressure vessel was purged with CO2, and then CO2 was introduced into the pressure vessel using a liquid transfer pump to bring the pressure inside the pressure vessel to 4.1 MPa, and the polymerization reaction was carried out at 60°C for 16 hours. After the reaction was complete, chloroform was added to the contents of the pressure vessel to prepare a chloroform solution, and 4M hydrochloric acid was added and the mixture was washed several times. Next, the organic layer was concentrated using a rotary evaporator, and the concentrated solution was added dropwise to stirred methanol to precipitate the product. Subsequently, the product was dried under reduced pressure using a diaphragm pump in a desiccator, and then vacuum dried at 60°C to obtain ethylene oxide-ethylene carbonate copolymer (poly(EC / EO)).

[0052] (Fabrication of solid electrolyte membranes) Ethylene oxide-ethylene carbonate copolymer was used as the binder polymer, LiFSI as the metal salt, glutaronitrile (relative permittivity of 37 at a frequency of 1 kHz) as the high dielectric constant compound, and LiBOB were weighed in a mass ratio of 35:30:35:2. These were dissolved in a solvent (dimethyl carbonate) and thoroughly stirred to obtain an electrolyte preparation solution. The electrolyte preparation solution was then cast onto a fluororesin mold, dried at 60°C for 6 hours under a dry nitrogen atmosphere, and then dried again at 60°C for 24 hours under reduced pressure to remove the dimethyl carbonate and obtain a solid electrolyte film.

[0053] [Comparative Example 1] A solid electrolyte membrane was obtained in the same manner as in Example 1, except that LiBOB was not added when preparing the electrolyte solution.

[0054] [Example 2] A solid electrolyte membrane was obtained in the same manner as in Example 1, except that polycarbonate (PEC, trade name "QPAC-25", manufactured by EMPOWERMATERIALS) was weighed as the binder polymer, LiFSI as the metal salt, glutaronitrile as the high dielectric constant compound, and LiBOB were weighed in a mass ratio of 35:30:35:2.

[0055] [Comparative Example 2] A solid electrolyte membrane was obtained in the same manner as in Example 2, except that LiBOB was not added when preparing the electrolyte solution.

[0056] [Example 3] (Monomer synthesis) Lithium bromide (LiBr) was used after vacuum drying anhydrous LiBr (manufactured by Kanto Chemical Co., Ltd.) at 120°C for 3 hours before use. Carbon dioxide was used by filling a gas collection balloon with liquefied carbon dioxide (99.995% purity) at atmospheric pressure. In a 300 mL three-necked flask, LiBr (434 mg, 5.0 mmol), 4-hydroxybutyl acrylate glycidyl ether (4HBAGE, 20.02 g, 100 mmol, manufactured by Mitsubishi Chemical Corporation), and N,N-dimethylformamide (DMF, 60 mL) were added. A 5 L gas collection balloon filled with carbon dioxide was connected, and the pressure was reduced to replace the inside of the reaction vessel with carbon dioxide. The mixture was heated at 100°C for 16 hours under a carbon dioxide atmosphere. After cooling to room temperature, the reaction solution was poured in pure water, the organic matter was extracted with toluene, the resulting organic layer was washed five times with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure to obtain the crude product of monomer A. The crude product was purified by silica gel column chromatography (eluent hexane / ethyl acetate = 2 / 1), and monomer A was isolated in 88% yield.

[0057] [ka]

[0058] (Fabrication of solid electrolyte membranes) Monomer A, a photoinitiator (Darocur 1173, manufactured by BASF), LiFSI as a metal salt, propylene carbonate (relative permittivity of 64 at a frequency of 1 kHz) as a high dielectric constant compound, and LiBOB were weighed in a mass ratio of 24:1:50:25:0.5 and thoroughly stirred to obtain an electrolyte preparation solution. This electrolyte preparation solution was cast onto a support substrate and irradiated with UV under a nitrogen atmosphere to polymerize monomer A, thereby obtaining a solid electrolyte film containing polymer A (acrylate-based polymer) as described below.

[0059] [ka]

[0060] [Comparative Example 3] A solid electrolyte membrane was obtained in the same manner as in Example 3, except that LiBOB was not added when preparing the electrolyte solution.

[0061] [Evaluation of solid electrolytes] The solid electrolyte membranes obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to ionic conductivity measurements and voltage stability evaluations. The results are shown in Table 1. Table 1 also shows the type of binder polymer and the presence or absence of LiBOB in Examples 1-3 and Comparative Examples 1-3.

[0062] [Table 2]

[0063] As is clear from the results shown in Table 1, the solid electrolyte membranes obtained in Examples 1-3, which used LiBOB, had a higher oxidation initiation potential and improved oxidation resistance compared to the solid electrolyte membranes obtained in Comparative Examples 1-3, which did not use LiBOB. Furthermore, the solid electrolyte membranes obtained in Examples 1-3 were found to have high ionic conductivity. From this, it was confirmed that the solid electrolyte of the present invention has high ionic conductivity and sufficient oxidation resistance.

Claims

1. Binder polymer and High dielectric constant compounds, Metal salts and A solid electrolyte comprising lithium bisoxalate borate, The binder polymer is at least one selected from the group consisting of carbonate polymers and (meth)acrylate polymers. The high dielectric constant compound is at least one selected from the group consisting of cyclic carbonate compounds and nitrile compounds. The content of the high dielectric constant compound is 10% by mass or more and 60% by mass or less based on the total amount of the solid electrolyte. The content of the lithium bisoxalate borate is 0.5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the high dielectric constant compound. solid electrolyte.

2. In the solid electrolyte according to claim 1, The relative permittivity of the high dielectric constant compound at a frequency of 1 kHz is 30 or more. solid electrolyte.

3. In the solid electrolyte according to claim 1 or claim 2, The aforementioned metal salt is an alkali metal salt. solid electrolyte.

4. In the solid electrolyte according to claim 3, The alkali metal salt is a lithium salt. solid electrolyte.

5. In the solid electrolyte according to any one of claims 1 to 4, The content of the lithium bisoxalate borate is 0.1% by mass or more and 5% by mass or less based on the total amount of the solid electrolyte. solid electrolyte.

6. In the solid electrolyte according to any one of claims 1 to 5, An electrolyte preparation solution containing the binder polymer or the raw material for the binder polymer, the high dielectric constant compound, the metal salt, and the lithium bisoxalate borate is cast. solid electrolyte.

7. A solid electrolyte comprising the solid electrolyte according to any one of claims 1 to 6, battery.

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