Electrolyte and Energy Storage Device

Abstract

Provided is a feature that can improve ion conductivity. An electrolyte is characterized by containing inorganic composite particles in which are composited: a compound having one or more functional groups selected from (meth)acryloxy groups, Si(OR)3 groups (where R is a hydrogen atom or a C1-3 alkyl group), and Al(OR)2 groups (where R is a hydrogen atom or a C1-3 alkyl group), and also having a betaine structure; and inorganic particles.

Description

[Technical Field]

[0001] The present invention relates to an electrolyte and an electricity storage device. [Background technology]

[0002] For example, electricity storage devices such as lithium ion secondary batteries are power devices with high energy density, and have therefore been widely used in recent years as power sources for terminals such as notebook computers and mobile phones (for example, Patent Document 1).In order to improve the ionic conductivity of these electricity storage devices, Patent Document 1 uses an electrolyte containing inorganic particles such as aluminum oxide or silicon oxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6562184 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the electrolyte described in Patent Document 1 does not have sufficient ionic conductivity and there is room for improvement, so there has been a demand for the development of other methods for improving ionic conductivity. [Means for solving the problem]

[0005] The present invention has been made to solve the above-mentioned problems, and can be realized in the following forms.

[0006] (1) According to one aspect of the present invention, For power storage devicesAn electrolyte is provided, which is characterized by containing inorganic composite particles in which inorganic particles are composited with a compound having one or more functional groups selected from a (meth)acryloxy group, a Si(OR)3 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and an Al(OR)2 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms) and a betaine structure.

[0007] The electrolyte of this form can improve ionic conductivity.

[0008] (2) The above For power storage devices In the electrolyte, the functional group may be one or more selected from a (meth)acryloxy group and a Si(OR) 3 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms).

[0009] According to this type of electrolyte, the ionic conductivity can be further improved.

[0010] (3) The above For power storage devices An electrolyte, wherein the betaine structure is SO3 - , PO3H - , and COO - and a quaternary ammonium cation.

[0011] According to this type of electrolyte, the ionic conductivity can be further improved.

[0012] (4) The above For power storage devices In the electrolyte, the content of the compound may be 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the content of the inorganic particles.

[0013] According to this type of electrolyte, the ionic conductivity can be further improved.

[0014] (5) The above For power storage devices An electrolyte, wherein the inorganic particles have a BET specific surface area of ​​1.0 m 2 / g or more.

[0015] According to this type of electrolyte, the ionic conductivity can be further improved.

[0016] (6) The above For power storage devices The electrolyte may contain the inorganic composite particles in an amount of 1 part by mass or more and 50 parts by mass or less relative to 100 parts by mass of the electrolyte.

[0017] According to this type of electrolyte, the ionic conductivity can be further improved.

[0018] The present invention can be realized in various forms, for example, in the form of an electricity storage device including an electrolyte. DETAILED DESCRIPTION OF THE INVENTION

[0019] A. Embodiment A1. Electrolyte An electrolyte according to one embodiment of the present invention is characterized by comprising inorganic composite particles in which inorganic particles are composited with a compound having one or more functional groups selected from a (meth)acryloxy group, a Si(OR) group (where R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and an Al(OR) group (where R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms) and a betaine structure. In this specification, the term "composite" refers to a state in which the particles are bound to each other by, for example, ionic bonds, covalent bonds, hydrogen bonds, van der Waals forces, or the like. The electrolyte of this embodiment can improve ionic conductivity, although the mechanism is unclear.

[0020] In this specification, "one or more functional groups selected from a (meth)acryloxy group, a Si(OR)3 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and an Al(OR)2 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms)" is also simply referred to as "functional group".

[0021] In this specification, "a compound having one or more functional groups selected from a (meth)acryloxy group, a Si(OR)3 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and an Al(OR)2 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms) and a betaine structure" is also simply referred to as "betaine." In this specification, the term "betaine structure" refers to a structure in which a positive charge and a negative charge are present in the same molecule at positions that are not adjacent to each other, and no dissociable hydrogen is bonded to the positively charged atom.

[0022] The betaine of the present embodiment is not particularly limited, but is represented by the following general formula. YAN + R 1 R 2 -BZ - Y represents a (meth)acryloxy group, a Si(OR)3 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), or an Al(OR)2 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms). Z - is SO3 - , PO3H - , or COO - A and B each independently represent an alkylene group having 1 to 6 carbon atoms. It is preferable that A and B each independently represent an alkylene group having 2 to 4 carbon atoms. R 1 and R 2 R each independently represents an alkyl group having 1 to 6 carbon atoms. 1 and R 2 is preferably an alkyl group having 2 to 4 carbon atoms.

[0023] The betaine of the present embodiment is not particularly limited, and examples thereof include N,N-dimethyl-(trihydroxysilyl)propyl-N-sulfopropyl-ammonium, inner salt (hereinafter also referred to as "compound A"), [2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium hydroxide, inner salt (hereinafter also referred to as "compound B"), 1-propanaminium,N,N-dimethyl-N-(3-phosphonopropyl)-3-(trimethoxysilyl)-, inner salt (hereinafter also referred to as "compound C"), 1-propanaminium,3-carboxy-N,N-dimethyl-N-[3-(trimethoxysilyl)propyl]-, inner salt (hereinafter also referred to as "compound D"), and 1-propanaminium,N,N-dimethyl-N-(3-boronopropyl)-3-(trimethoxysilyl)-, inner salt.

[0024] Among the above betaines, from the viewpoint of improving ionic conductivity, it is preferable to use one or more selected from N,N-dimethyl-(trihydroxysilyl)propyl-N-sulfopropyl-ammonium, inner salt (compound A), [2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium hydroxide, inner salt (compound B), 1-propanaminium,N,N-dimethyl-N-(3-phosphonopropyl)-3-(trimethoxysilyl)-, inner salt (compound C), and 1-propanaminium,3-carboxy-N,N-dimethyl-N-[3-(trimethoxysilyl)propyl]-, inner salt (compound D), and it is more preferable to use N,N-dimethyl-(trihydroxysilyl)propyl-N-sulfopropyl-ammonium, inner salt (compound A). As the betaine of this embodiment, from the viewpoint of improving ionic conductivity, it is preferable to have at least one of a sulfo group and a carboxy group, and a quaternary ammonium cation.

[0025] The functional group possessed by the betaine of this embodiment is not particularly limited, and examples thereof include a (meth)acryloxy group, a Si(OR)3 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and an Al(OR)2 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms). Among these functional groups, from the viewpoint of improving ionic conductivity, one or more selected from the (meth)acryloxy group and the Si(OR)3 group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms) are preferred. Note that the (meth)acryloxy group includes a methacryloxy group and an acryloxy group.

[0026] The inorganic particles to be composited with the betaine of this embodiment are not particularly limited, and examples thereof include inorganic oxide particles, which include, but are not limited to, inorganic oxides containing, as constituent elements, Li, Mg, Al, Si, Ca, Ti, Zr, La, Na, K, Ba, Sr, V, Nb, B, Ge, etc.

[0027] More specifically, examples of inorganic particles to be combined with betaine in this embodiment include Al2O3 (alumina), Li 1+x+y Ti 2-x Al x P 3-y SiyO 12 (0 <x<2,0<y<3))(LATP)、Li7La3Zr2O 12 (LLZ), La 2 / 3-x Li 3x TiO3(LLT), Li 1.5 Al 0.5 Ge 1.5 Examples include (PO4)3(LAGP), SiO2, TiO2, ZnO, AlOOH, ZrO2, BaTiO3, zeolite, etc. Zeolite is not particularly limited, but examples include those with the following structure. (M I ,M II1 / 2 ) m (Al m Si n O 2(m+n) )·xH2O In the formula, n and m satisfy n≧m>0, and x satisfies x≧0. I Li + , Na + , K. + and M II Ca 2+ , Mg 2+ , Ba 2+ and other divalent metal ions.

[0028] The BET specific surface area of ​​the inorganic particles is 1.0 m from the viewpoint of improving ionic conductivity. 2 / g or more, and 2.0m 2 / g or more is more preferable, and 3.0m2 On the other hand, the BET specific surface area of ​​the inorganic particles is preferably 800 m / g or more. 2 / g or more is preferable, and 400m 2 / g or less is more preferable, and 100m 2 / g or less is more preferable. In this specification, the BET specific surface area indicates a value measured in accordance with JIS Z 8830:2013.

[0029] The content ratio of the betaine in this embodiment to the inorganic particles to be composited is not particularly limited, but for example, the content of betaine is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the inorganic particles, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

[0030] The content of the inorganic composite particles of the present embodiment is not particularly limited, but is, for example, preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of the electrolyte.

[0031] The electrolyte may contain a polymer. The polymer is not particularly limited, but a suitable compound can be selected depending on, for example, the composition of the electrolyte according to the present disclosure or the type of application (electrochemical device). Examples of the polymer include acrylate-based compounds and oxetane-based compounds.

[0032] The acrylate compound is not particularly limited, but examples thereof include tetrafunctional polyether acrylate, difunctional polyether acrylate, other AO-added acrylate, polyethylene glycol diacrylate, and the like.

[0033] The oxetane compound is not particularly limited, but examples thereof include methyl methacrylate-oxetanyl methacrylate copolymer, etc. These polymers may be used alone or in combination of two or more.

[0034] Polymers other than those mentioned above are not particularly limited, but examples thereof include polyurethane, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide, polyamide, silicone (polysiloxane), styrene-butadiene rubber (SBR), polyacrylic acid, etc. These polymers may be used alone or in combination of two or more.

[0035] The electrolyte of this embodiment may be, for example, an ionic liquid containing a bis(fluorosulfonyl)imide anion (FSI anion) as an anion component. Here, an ionic liquid is characterized by being liquid at room temperature (25°C), non-volatile, and having a relatively high decomposition temperature. By using an ionic liquid as the electrolyte solution constituting the electrolyte, the electrolyte has superior heat resistance and safety compared to when a typical flammable organic solvent (e.g., cyclic carbonate, chain carbonate, etc.) is used. Furthermore, by doing so, a battery with high performance, high energy density, and high voltage can be obtained, even during high-rate charge / discharge. The method for preparing the FSI anion is not particularly limited, but examples include a method of reacting fluorosulfonic acid with urea. Impurities can be identified by analysis using a plasma emission spectrometer (ICP).

[0036] The anion component contained in the ionic liquid may contain anions other than the FSI anion. Examples of anions other than the FSI anion include BF4 - , PF6 - , SbF6 - , NO3 - , CF3SO3 - , (CF3SO2)2N - (hereinafter referred to as "TFSI"), (C2F5SO2)2N - , (CF3SO2)3C- , CF3CO2 - , C3F7CO2 - , CH3CO2 - , (CN)2N - In addition, two or more of the above-mentioned anions may be contained as anions other than the FSI anion.

[0037] In the ionic liquid, the cation to be combined with the above-mentioned FSI anion is not particularly limited, but it is preferable to use a cation that forms an ionic liquid with a melting point of 50°C or less. By doing so, it is possible to suppress an increase in the viscosity of the non-aqueous electrolyte and to suppress a decrease in discharge capacity. Note that the non-aqueous electrolyte refers to a solution in which a lithium salt is dissolved as an electrolyte in a solvent for transferring lithium ions.

[0038] As the above-mentioned cation, for example, a compound containing an element such as N, P, S, O, C, or Si, and having a chain structure or a cyclic structure such as a five-membered ring or a six-membered ring as a skeleton, is used.

[0039] Examples of cyclic structures such as 5-membered rings and 6-membered rings include heterocyclic structures such as a furan ring, thiophene ring, pyrrole ring, pyridine ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, furazan ring, imidazole ring, pyrazole ring, pyrazine ring, pyrimidine ring, pyridazine ring, pyrrolidine ring, piperidine ring, benzofuran ring, isobenzofuran ring, indole ring, isoindole ring, indolizine ring, and carbazole ring.

[0040] Among these cations, nitrogen-containing chain or cyclic compounds are particularly preferred because they are industrially inexpensive and chemically and electrochemically stable.

[0041] Examples of cations containing a nitrogen element include alkylammonium such as triethylammonium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-methyl-1-propyl-pyrrolidinium, and methylpropylpiperidinium.

[0042] The lithium salt dissolved in the ionic liquid as a supporting electrolyte for the non-aqueous electrolyte can be any lithium salt generally used as an electrolyte for a non-aqueous electrolyte, without any particular limitation. Examples of such lithium salts include LiPF, LiBF, LiClO, LiAsF, LiCF, SO, LiC(CF, SO), LiN(CF, SO) (LiTFSI), LiN(FSO) (LiFSI), and LiBCO. Two or more of these lithium salts may be mixed and used. LiFSI and LiTFSI are preferred as the lithium salt.

[0043] Such a lithium salt is preferably contained in the ionic liquid at a concentration of, for example, 0.1 mol / kg or more and 3.0 mol / kg or less, more preferably 0.3 mol / kg or more and 2.0 mol / kg or less, and even more preferably 0.5 mol / kg or more and 1.5 mol / kg or less.

[0044] A2. Energy storage device In another embodiment, an electricity storage device including the electrolyte described above is provided. The electricity storage device of this embodiment further includes a positive electrode and a negative electrode. The electricity storage device is not particularly limited, and examples thereof include a lithium ion secondary battery, an electric double layer capacitor, and a lithium ion capacitor. In the following, a lithium ion secondary battery will be used as an example of an electricity storage device.

[0045] The positive electrode and negative electrode of this embodiment each include an electrode active material, a conductive agent, a current collector, and a binder.

[0046] The positive electrode active material used in the positive electrode of this embodiment is not particularly limited as long as it is capable of inserting and extracting lithium ions. Examples of the positive electrode active material include metal oxides, composite oxides of lithium and transition metals, metal chalcogenides, and conductive polymer compounds. Examples of metal oxides include CuO, Cu2O, MnO2, MoO3, VO5, CrO3, MoO3, Fe2O3, Ni2O3, and CoO3. Examples of metal chalcogenides include TiS2, MoS2, and NbSe3. Examples of conductive polymer compounds include polyacene, polyparaphenylene, polypyrrole, and polyaniline.

[0047] As the positive electrode active material, a composite oxide of lithium and a transition metal is preferred because it is easy to obtain a high voltage. Examples of the composite oxide of lithium and a transition metal include LiCoO2, LiMnO2, LiMn2O4, LiNiO2, LiFePO4, and LiNi x Co (1-x) O2, LiMn a Ni b Co c (a+b+c=1), etc. Also, a composite oxide of lithium and a transition metal doped with a small amount of elements such as fluorine, boron, aluminum, chromium, zirconium, molybdenum, iron, etc., or a lithium composite oxide particle surface treated with carbon, MgO, Al2O3, SiO2, etc. may be used as the positive electrode active material. Also, two or more of the above may be used in combination as the positive electrode active material. The amount of the positive electrode active material is not particularly limited, but for example, 3 mg / cm2 per unit area of ​​the current collector. 2 More than 10mg / cm 2 The following may also be used.

[0048] The negative electrode active material used in the negative electrode of this embodiment is not particularly limited as long as it is capable of inserting and extracting metallic lithium or lithium ions. Examples of the negative electrode active material include carbon materials, metal materials, lithium transition metal nitrides, crystalline metal oxides, amorphous metal oxides, silicon compounds, conductive polymers, etc. Examples of the carbon material include natural graphite, artificial graphite, non-graphitizable carbon, and easily graphitizable carbon. Examples of the metal material include metallic lithium, alloys, and tin compounds. Specific examples of the negative electrode active material include Li4Ti5O 12 , NiSi5C6, etc. Two or more of the above-mentioned materials may be used in combination as the negative electrode active material. The amount of the negative electrode active material is not particularly limited, but for example, it may be 1 mg / cm2 per unit area of ​​the current collector. 2 More than 5mg / cm 2 The following may also be used.

[0049] The conductive agent used in the positive electrode and negative electrode of this embodiment is not particularly limited, but examples thereof include carbon black such as acetylene black and ketjen black. Furthermore, instead of carbon black, conductive materials such as natural graphite (e.g., scaly graphite, flake graphite, and clayey graphite), artificial graphite, carbon whiskers, carbon fibers, metal (e.g., copper, nickel, aluminum, silver, and gold) powder, metal fibers, and conductive ceramic materials may also be used as the conductive agent. Furthermore, two or more of the above-mentioned conductive materials may be used in combination. The amount of the conductive agent added is not particularly limited, but is preferably 1% by mass to 30% by mass, and more preferably 2% by mass to 20% by mass, of the amount of the positive electrode active material or the negative electrode active material.

[0050] The current collector used in the positive electrode of this embodiment is not particularly limited, and examples thereof include aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymers, conductive glass, etc. Furthermore, for the purpose of improving adhesion, conductivity, and oxidation resistance, a material in which the surface of aluminum, copper, or the like is treated with carbon, nickel, titanium, silver, or the like may be used as the positive electrode current collector.

[0051] The current collector used in the negative electrode of this embodiment is not particularly limited, and examples thereof include copper, stainless steel, nickel, aluminum, titanium, baked carbon, conductive polymers, conductive glass, Al-Cd alloys, etc. Furthermore, for the purpose of improving adhesion, conductivity, and oxidation resistance, a material in which the surface of copper or the like is treated with carbon, nickel, titanium, silver, etc. may be used as the negative electrode current collector.

[0052] The surface of the current collector used for the positive electrode or negative electrode may be oxidized. The current collector may be in the form of a foil, film, sheet, or net. The current collector may be punched or expanded, or may be a molded body such as a lath, porous body, or foam. The thickness of the current collector is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less.

[0053] The binder of this embodiment is not particularly limited, and may be, for example, polyvinylidene fluoride (PVDF). Furthermore, instead of PVDF, for example, PVDF copolymer resin, fluororesin, styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), styrene-acrylonitrile copolymer, etc. may be used as the binder. For example, PVDF copolymer resin may be a copolymer resin of PVDF with hexafluoropropylene (HFP), perfluoromethyl vinyl ether (PFMV), or tetrafluoroethylene (TFE). For example, polytetrafluoroethylene (PTFE), fluororubber, etc. may be used as the fluororesin. For example, polysaccharides such as carboxymethyl cellulose (CMC), and thermoplastic resins such as polyimide resins may be used as other binders. Furthermore, two or more of the above binders may be used in combination. The amount of binder added is not particularly limited, but is preferably 1% by mass to 30% by mass, more preferably 2% by mass to 20% by mass, based on the amount of the positive electrode active material or the negative electrode active material.

[0054] The manufacturing method of the electrode of this embodiment is not particularly limited. As a manufacturing method of the electrode, for example, after preparing a slurry-like electrode material by mixing an electrode active material, a conductive material, a binder, etc. in a dispersion medium, the electrode material is applied to a current collector, and then the dispersion medium is volatilized.

[0055] In order to make the above-mentioned electrode material into a slurry state, a viscosity modifier may be used. The viscosity modifier is not particularly limited, but for example, a water-soluble polymer can be used. Examples of the viscosity modifier include celluloses such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose; polycarboxylic acid-based compounds such as polyacrylic acid and sodium polyacrylate; compounds having a vinyl pyrrolidone structure such as polyvinyl pyrrolidone; polyacrylamide, polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum, agar, starch, etc. Further, as the viscosity modifier, two or more of the above may be used in combination. Carboxymethyl cellulose is preferable as the viscosity modifier.

[0056] The lithium-ion secondary battery of this embodiment may further include an insulating layer. As the insulating layer, for example, it can be formed by applying an inorganic solid electrolyte on the positive electrode or the negative electrode. The inorganic solid electrolyte is not particularly limited, but for example, Li 1.5 Al 0.5 Ge 1.5 (PO4)3 (LAGP), La 2 / 3-x Li 3x TiO3 (LLT), LICGC (registered trademark), Li 1+x+y Ti 2-x Al x P 3-y SiyO 12 (0 < x < 2, 0 < y < 3)) (LATP), etc.

[0057] The separator is a member provided between the positive electrode and the negative electrode to separate the positive electrode and the negative electrode. The separator of this embodiment is made of glass fiber. The porosity of the glass fiber of this embodiment may be 70% or more.

[0058] The lithium ion secondary battery of this embodiment can be formed into any shape, such as a cylindrical shape, a coin shape, a rectangular shape, or any other shape. The basic configuration of the battery is the same regardless of the shape, and the design can be modified depending on the purpose. For example, in the cylindrical shape, a negative electrode formed by applying a negative electrode active material to a negative electrode current collector and a positive electrode formed by applying a positive electrode active material to a positive electrode current collector are wound together with a separator interposed between them, and the resulting wound body is housed in a battery can, and a non-aqueous electrolyte is poured into the battery can with insulating plates placed above and below it, and the battery can is sealed. In addition, when applied to a coin-type lithium ion secondary battery, a disc-shaped negative electrode, a separator, a disc-shaped positive electrode, and a stainless steel plate are stacked and housed in a coin-type battery can, and a non-aqueous electrolyte is poured into the battery can and sealed.

[0059] B. Experiment The present invention will be described in more detail below with reference to examples, but is not limited to the following examples. In the examples, unless otherwise specified, "%" means "% by mass" and "ratio" means "mass ratio."

[0060] B1. Experiment 1 <Example 1-1> (Preparation of Electrolyte Solution) The following work was carried out in a dry air atmosphere with a dew point of -50 ° C or less. An electrolyte solution was prepared by mixing 20.1 parts by mass of tetrafunctional polyether acrylate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name: Elexel TA-210), which is a polymer electrolyte and matrix material, 46.9 parts by mass of 1-ethyl-3-methyl-imidazolium bis(fluorosulfonyl)imide (EMIm-FSI), which is an ionic liquid electrolyte solvent (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name: Elexel IL-110), 12.5 parts by mass of lithium bis(fluorosulfonyl)imide (LiFSI), which is a lithium salt, 0.5 parts by mass of 2,2'-Azobis(2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., product name: V-65), which is an azo initiator, and 20 parts by mass of 1,2-Dimethoxyethane (DME), which is a dilution solvent.

[0061] (Preparation of inorganic composite particles) A 0.33% by mass solution of N,N-dimethyl-(trihydroxysilyl)propyl-N-sulfopropyl-ammonium, inner salt (compound A) was dissolved in an aqueous solution containing alumina (particle size 0.5 μm, BET specific surface area 5.9 m). 2 / g) were mixed so that the ratio of compound A to alumina was 1 / 100. The mixture was then stirred at room temperature (25°C) for 12 hours to composite the alumina and compound A, and the aqueous solution and alumina were then filtered to obtain inorganic composite particles. The chemical formula (1) of compound A is shown below.

[0062] [ka]

[0063] (Preparation of electrolyte) The electrolyte solution and inorganic composite particles were mixed so that the mass of the electrolyte solution excluding the dilution solvent / the mass of the inorganic composite particles was 98 / 2, and then the inorganic composite particles were dispersed in the solution using a planetary stirring device to prepare the electrolyte solution.

[0064] The prepared electrolyte solution was applied to a 20 μm-thick SUS foil using an applicator and then vacuum-dried at 25°C for 2 hours. The polyether acrylate was then polymerized by vacuum heating at 80°C for 12 hours to obtain an electrolyte coating film with the composition ratio shown in Table 1 below. In the tables, the betaine of this embodiment and the betaine substitute of this embodiment are collectively referred to as the "composite." The lithium salt concentration (mol / kg) refers to the lithium salt content (mol) relative to the total content (kg) of the ionic liquid and polymer. In the tables, the "polymer + electrolyte ratio" refers to the sum (%) of the polymer and electrolyte relative to the total electrolyte. In the tables, the "inorganic particle + composite ratio" refers to the sum (%) of the inorganic particles and composite relative to the total electrolyte.

[0065] The obtained electrolyte membrane according to Example 1-1 was punched out to a diameter of 16φ, and then AC impedance measurement was carried out, and the ionic conductivity was calculated by the method described below.

[0066] <Examples 1-2 to 1-4> An electrolyte membrane was produced in the same manner as in Example 1-1, except that the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 1 below.

[0067] <Examples 1-5 to 1-6> An electrolyte membrane was produced in the same manner as in Example 1-1, except that inorganic composite particles prepared using [2-(Methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium hydroxide, inner salt (Compound B) were used instead of Compound A in the electrolyte membrane of Example 1-1, and the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 1. Here, the chemical formula (2) of Compound B is shown below.

[0068] [ka]

[0069] <Examples 1-7 to 1-8> An electrolyte membrane was prepared in the same manner as in Example 1-1, except that inorganic composite particles prepared using 1-Propanaminium,N,N-dimethyl-N-(3-phosphonopropyl)-3-(trimethoxysilyl)-, inner salt (Compound C) were used instead of Compound A, and the ratio of the mass of the electrolyte solution excluding the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 1. Here, the chemical formula (3) of Compound C is shown below.

[0070] [ka]

[0071] <Examples 1-9 to 1-10> An electrolyte membrane was prepared in the same manner as in Example 1-1, except that inorganic composite particles prepared using 1-Propanaminium,3-carboxy-N,N-dimethyl-N-[3-(trimethoxysilyl)propyl]-, inner salt (Compound D) were used instead of Compound A, and the ratio of the mass of the electrolyte solution excluding the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 1. Here, the chemical formula (4) of Compound D is shown below.

[0072] [ka]

[0073] <Comparative Example 1-1> An electrolyte membrane was prepared in the same manner as in Example 1-1, except that alumina was used instead of the inorganic composite particles prepared using compound A in the electrolyte membrane of Example 1-1, and the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of alumina was changed to the ratio shown in Table 1.

[0074] <Comparative Example 1-2> An electrolyte membrane was prepared in the same manner as in Example 1-1, except that inorganic composite particles prepared using 1-Alkylaminium, N-(carboxymethyl)-N,N-dimethyl-, inner salt (Compound E) were used instead of Compound A in the electrolyte membrane of Example 1-1, and the ratio of the mass of the electrolyte solution excluding the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 1. Here, the chemical formula (5) of Compound E is shown below. Note that while Compound E has a betaine structure, it does not have any functional groups other than the betaine structure.

[0075] [ka] (wherein R represents an alkyl group having 12 to 16 carbon atoms)

[0076] <Comparative Example 1-3> An electrolyte membrane was produced in the same manner as in Example 1-1, except that inorganic composite particles prepared using Trimethyl[3-(trimethoxysilyl)propyl]ammonium Chloride (Compound F) were used instead of Compound A in the electrolyte membrane of Example 1-1, and the ratio of the mass of the electrolyte solution excluding the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 1. Here, the chemical formula (6) of Compound F is shown below. Note that Compound F does not have a betaine structure.

[0077] [ka]

[0078] <Method for measuring ionic conductivity> The thickness (membrane thickness) and cross-sectional area of ​​the electrolyte membrane obtained in each example or comparative example were measured. The obtained electrolyte was placed in a two-electrode cell, and then electrochemical impedance (EIS) was measured using an impedance analyzer (product name: SP-150) manufactured by Bio-Logic SAS at 25°C and a frequency of 1 MHz to 0.1 Hz to obtain the bulk resistance value of the electrolyte. The obtained resistance value and the following formula were used to obtain the ionic conductivity (σ) of the electrolyte membrane. σ = l / (s R) (where l represents the thickness of the electrolyte membrane (cm), and s represents the cross-sectional area (cm 2 ) and R represents the bulk resistance (Ω).

[0079] The results obtained are shown in Table 1 below.

[0080] [Table 1]

[0081] The following was found from Table 1. That is, it was found that the examples including inorganic composite particles in which a compound having a betaine structure and a functional group is composited with inorganic particles have higher ionic conductivity than the comparative examples in which this is not the case.

[0082] On the other hand, Comparative Example 1-1 used only inorganic particles instead of inorganic composite particles, and therefore had lower ionic conductivity than the Examples. Comparative Example 1-2 used inorganic composite particles using a compound having a betaine structure but no functional group, and therefore had lower ionic conductivity than the Examples. Furthermore, Comparative Example 1-3 used inorganic composite particles using a compound not having a betaine structure, and therefore had lower ionic conductivity than the Examples.

[0083] B2. Experiment 2 <Examples 2-1 to 2-4> An electrolyte membrane was prepared in the same manner as in Example 1-1, except that in the electrolyte membrane of Example 1-1, (i) the lithium salt concentration and (ii) the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of the inorganic composite particles were changed to the ratios shown in Table 2 below.

[0084] <Comparative Example 2-1> An electrolyte membrane was produced in the same manner as in Example 1-1, except that (i) alumina was used instead of inorganic composite particles using compound A, and (ii) the lithium salt concentration and (iii) the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of alumina were changed to the ratios shown in Table 2.

[0085] The results obtained are shown in Table 2 below.

[0086] [Table 2]

[0087] The following was found from Table 2. That is, by comparing Examples 2-1 to 2-4 with Comparative Example 2-1, it was found that even when the lithium salt concentration was different from that in Experiment 1, Examples including inorganic composite particles in which a compound having a betaine structure and a functional group is composited with inorganic particles had higher ionic conductivity than Comparative Examples that did not.

[0088] B3. Experiment 3 <Examples 3-1 and 3-2> An electrolyte membrane was produced in the same manner as in Example 1-1, except that in the electrolyte membrane of Example 1-1, 1-methyl-1-propyl-pyrrolidinium bis(fluorosulfonyl)imide (MPPy-FSI) (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Elexel IL-120) was used as the electrolyte solution instead of EMIm-FSI, and the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 3 below.

[0089] (Comparative Example 3-1) An electrolyte membrane was produced in the same manner as in Example 1-1, except that alumina was used instead of the inorganic composite particles, MPPy-FSI was used instead of EMIm-FSI as the electrolyte solution, and the mass ratio of the electrolyte solution excluding the dilution solvent to the alumina mass was changed to the ratio shown in Table 3.

[0090] The results obtained are shown in Table 3 below.

[0091] [Table 3]

[0092] The following was found from Table 3. That is, by comparing Examples 3-1 and 3-2 with Comparative Example 3-1, it was found that even when an electrolyte solution different from that used in Experiment 1 was used, Examples including inorganic composite particles in which a compound having a betaine structure and a functional group is composited with inorganic particles had higher ionic conductivity than Comparative Examples that did not.

[0093] B4. Experiment 4 <Examples 4-1 and 4-2> An electrolyte membrane was produced in the same manner as in Example 1-1, except that in the electrolyte membrane of Example 1-1, Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was used instead of LiFSI as the lithium salt, and the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 4 below.

[0094] <Comparative Example 4-1> An electrolyte membrane was produced in the same manner as in Example 1-1, except that in the electrolyte membrane of Example 1-1, alumina was used instead of the inorganic composite particles, LiTFSI was used instead of LiFSI as the lithium salt, and the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of alumina was changed to the ratio shown in Table 4.

[0095] The results obtained are shown in Table 4 below.

[0096] [Table 4]

[0097] The following was found from Table 4. That is, by comparing Examples 4-1 and 4-2 with Comparative Example 4-1, it was found that even when a lithium salt different from that used in Experiment 1 was used, Examples including inorganic composite particles in which a compound having a betaine structure and a functional group is composited with inorganic particles had higher ionic conductivity than Comparative Examples that did not.

[0098] B5. Experiment 5 <Examples 5-1 and 5-2> An electrolyte membrane was produced in the same manner as in Example 1-1, except that in the electrolyte membrane of Example 1-1, lithium tetrafluoroborate (LiBF) was used instead of LiFSI as the lithium salt, and the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of the inorganic composite particles was changed to the ratio shown in Table 5 below.

[0099] <Comparative Example 5-1> An electrolyte membrane was produced in the same manner as in Example 1-1, except that in the electrolyte membrane of Example 1-1, alumina was used instead of the inorganic composite particles, LiBF was used instead of LiFSI as the lithium salt, and the mass ratio of the electrolyte solution other than the dilution solvent to the alumina mass was changed to the ratio shown in Table 5.

[0100] The results obtained are shown in Table 5 below.

[0101] [Table 5]

[0102] The following was found from Table 5. That is, by comparing Examples 5-1 and 5-2 with Comparative Example 5-1, it was found that even when a lithium salt different from that used in Experiment 1 was used, Examples including inorganic composite particles in which a compound having a betaine structure and a functional group is composited with inorganic particles had higher ionic conductivity than Comparative Examples that did not.

[0103] B6. Experiment 6 <Examples 6-1 and 6-2> An electrolyte membrane was produced in the same manner as in Example 1-1, except that in the electrolyte membrane of Example 1-1, ethylene carbonate (EC) / propylene carbonate (PC) = 1 / 1 was used instead of EMIm-FSI as the electrolyte solution, lithium hexafluorophosphate (LiPF6) was used instead of LiFSI as the lithium salt, and the ratio of the mass of the electrolyte solution other than the dilution solvent / the mass of the inorganic composite particles was changed to the ratio shown in Table 6 below.

[0104] <Comparative Example 6-1> An electrolyte membrane was produced in the same manner as in Example 1-1, except that alumina was used instead of the inorganic composite particles, EC / PC=1 / 1 was used instead of EMIm-FSI as the electrolyte solution, LiPF6 was used instead of LiFSI as the lithium salt, and the ratio of the mass of the electrolyte solution other than the dilution solvent to the mass of alumina was changed to the ratio shown in Table 6.

[0105] The results obtained are shown in Table 6 below.

[0106] [Table 6]

[0107] The following was found from Table 6. That is, by comparing Examples 6-1 and 6-2 with Comparative Example 6-1, it was found that even when a lithium salt and an electrolyte solution different from those in Experiment 1 were used, Examples including inorganic composite particles in which a compound having a betaine structure and a functional group is composited with inorganic particles have higher ionic conductivity than Comparative Examples that do not.

[0108] B7. Experiment 7 <Example 7-1> (Preparation of inorganic composite particles) Inorganic composite particles were obtained in the same manner as in Example 1-1.

[0109] (Preparation of composite electrolyte) A composite electrolyte solution was prepared by mixing 34.5 parts by mass of a 10% by mass polyurethane / N-methylpyrrolidone (NMP) solution with a carbonate skeleton and a molecular weight of approximately 60,000, which serves as the matrix material, 20.3 parts by mass of EMImFSI (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Elexel IL-110), which serves as the electrolyte solvent, and 3.8 parts by mass of LiFSI, which serves as a lithium salt, and then dispersing 41.4 parts by mass of inorganic composite particles into the solution using a planetary stirrer.

[0110] The prepared composite electrolyte solution was applied to a 20 μm-thick SUS foil using an applicator, and then dried at 80° C. for 6 hours. Thereafter, the foil was heated in a vacuum at 80° C. for 10 hours to obtain a composite electrolyte coating film having the composition shown in Table 7 below.

[0111] The composite electrolyte membrane obtained in Example 7-1 was punched out to a diameter of 16φ, and then AC impedance measurement was carried out to calculate the ionic conductivity.

[0112] <Example 7-2> A composite electrolyte membrane was produced in the same manner as in Example 7-1, except that the ratio of the electrolyte solution mass / inorganic composite particle mass in the composite electrolyte membrane of Example 7-1 was changed to the ratio shown in Table 7.

[0113] <Comparative Examples 7-1 to 7-2> In the composite electrolyte membrane of Example 7-1, a composite electrolyte membrane was prepared in the same manner as in Example 7-1, except that alumina was used instead of the inorganic composite particles and the ratio of the electrolyte solution mass to the alumina mass was changed to the ratio shown in Table 7.

[0114] The results obtained are shown in Table 7 below.

[0115] [Table 7]

[0116] It was found from Table 7 that, by comparing Examples 7-1 to 7-2 with Comparative Examples 7-1 to 7-2, even when polymers different from those in Experiment 1 were used, Examples containing inorganic composite particles in which a compound having a betaine structure and one or more functional groups other than the betaine structure and inorganic particles were combined had higher ionic conductivity than Comparative Examples that did not.

[0117] B8. Experiment 8 <Example 8-1> (Preparation of inorganic composite particles) To an aqueous solution in which 0.33% by mass of the above compound A was dissolved, Li 1+x+y Ti 2-x Al x P 3-y SiyO 12 (0 < x < 2, 0 < y < 3)) (LATP) was mixed so that the ratio of compound A to LATP was 1 / 100. Then, after compounding the inorganic particles and compound A by stirring at room temperature (25°C) for 12 hours, the aqueous solution and the inorganic particles were filtered off to obtain inorganic composite particles.

[0118] (Preparation of electrolyte powder) 2.5 parts by mass of matrix material Polyvinylidene DiFluoride (PVDF) (molecular weight approximately 300,000), 6.3 parts by mass of electrolyte solvent EMImFSI (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name: Elexel IL-110), 1.2 parts by mass of lithium salt LiFSI, and 50 parts by mass of dilution solvent DME were mixed, and then the inorganic composite particles were dispersed in the solution using a planetary stirrer to prepare an electrolyte solution. The dilution solvent was then dried under reduced pressure to obtain electrolyte powder.

[0119] (Preparation of electrolyte pellets) Approximately 0.3 g of the prepared electrolyte powder was placed in a cylindrical mold with a diameter of 12 mm and then subjected to a pressure of 200 kgf / cm 2 By uniaxially pressing the mixture at a pressure of 1000 kJ / cm for 30 seconds, electrolyte pellets having the composition ratio shown in Table 8 below were prepared.

[0120] The thickness of the obtained electrolyte pellet was measured, and then AC impedance measurement was carried out to calculate the ionic conductivity.

[0121] <Example 8-2> In the electrolyte pellets of Example 8-1, Li7La3Zr2O was used as the inorganic particles instead of LATP. 12 Electrolyte pellets were prepared in the same manner as in Example 8-1, except that (LLZ) was used.

[0122] <Example 8-3> An electrolyte pellet was produced in the same manner as in Example 8-1, except that La-Li-Ti perovskite oxide (LLT) was used as the inorganic particles instead of LATP in the electrolyte pellet of Example 8-1.

[0123] <Example 8-4> In the electrolyte pellet of Example 8-1, Li was used as the inorganic particles instead of LATP. 1.5 Al 0.5 Ge 1.5Electrolyte pellets were prepared in the same manner as in Example 8-1, except that (PO4)3(LAGP) was used.

[0124] <Comparative Examples 8-1 to 8-2> Electrolyte pellets were prepared in the same manner as in Example 8-1, except that LATP was used instead of the inorganic composite particles and the ratio of the mass of the electrolyte solution excluding the dilution solvent to the mass of LATP was changed to the ratio shown in Table 8.

[0125] The results obtained are shown in Table 8 below.

[0126] [Table 8]

[0127] The following was found from Table 8. That is, by comparing Examples 8-1 to 8-4 with Comparative Examples 8-1 to 8-2, it was found that even when inorganic particles different from those used in Experiment 1 were used, Examples including inorganic composite particles in which a compound having a betaine structure and a functional group is composited with inorganic particles had higher ionic conductivity than Comparative Examples that did not.

[0128] The present invention is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments and examples corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Industrial Applicability]

[0129] The electrolyte of this embodiment has high ionic conductivity, and therefore, an electricity storage device including the electrolyte of this embodiment can be suitably used as a power source for mobile devices, and is also useful for, for example, wearable devices, power tools, electric bicycles, electric wheelchairs, robots, electric vehicles, emergency power sources, and large-capacity stationary power sources.

Claims

1. (Meth)acryloxy group, Si(OR) ３ group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), Al(OR) ２ group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and a compound having a betaine structure, and inorganic particles, and an inorganic composite particle in which the inorganic particles are combined, and an electrolyte for a power storage device.

2. The electrolyte according to Claim 1, The functional group is one or more selected from (meth)acryloxy group and Si(OR) ３ ３ group (R is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), and the electrolyte for a power storage device is characterized by this.

3. The electrolyte according to Claim 1 or Claim 2, The betaine structure is SO ３ － , PO ３ H － , and COO － selected from one or more of them, and a quaternary ammonium cation, and is characterized by being an electrolyte for a power storage device.

4. The electrolyte according to any one of Claims 1 to 3, wherein the content of the compound is 0.1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the content of the inorganic particles, and which is an electrolyte for a power storage device.

5. The electrolyte according to any one of Claims 1 to 4, The BET specific surface area of the inorganic particles is 1.0 m ２ / g or more, and the electrolyte for a power storage device is characterized by this.

6. The electrolyte according to any one of Claims 1 to 5, wherein the content of the inorganic composite particles is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the electrolyte, and which is an electrolyte for a power storage device.

7. A power storage device comprising the electrolyte for a power storage device according to any one of Claims 1 to 6.

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