Flame-retardant non-aqueous electrolyte and secondary batteries using it

Abstract

This invention provides a flame-retardant non-aqueous electrolyte exhibiting good flame retardancy, as well as excellent cycle characteristics and electrical resistance characteristics, and a secondary battery using the same. The flame-retardant non-aqueous electrolyte of this invention comprises at least a non-aqueous solvent and an electrolyte dissolved in the aforementioned non-aqueous solvent. The aforementioned non-aqueous solvent comprises at least one phosphate ester represented by the following chemical formulas (1) to (3), and the aforementioned electrolyte comprises at least one difluorophosphate and nitrate. The content of the aforementioned phosphate ester is 20% by mass or more relative to the total mass of the aforementioned flame-retardant non-aqueous electrolyte. (In the formulas, X1 to X3 each independently represent hydrocarbon groups with 1 to 20 carbon atoms, and Y1 and Y2 each independently represent halogen atoms).

Description

Flame-retardant non-aqueous electrolyte and secondary batteries using it This invention relates to a flame-retardant non-aqueous electrolyte that exhibits excellent cycle characteristics even after repeated charge-discharge cycles over a long period of time, and to a secondary battery using the same. Traditional lithium-ion rechargeable batteries use flammable electrolytes. Therefore, the charging state is essentially an unstable state where energy is trapped in a flammable electrolyte. Consequently, in the event of an internal electrical short circuit or other abnormality, it could lead to fires. For this reason, in traditional lithium-ion rechargeable batteries, it was necessary to ensure safety while simultaneously increasing energy density. Here, based on the viewpoint of preventing fires caused by lithium-ion secondary batteries, consideration is given to endowing battery materials, especially electrolytes, with flame-retardant and self-extinguishing properties. For example, Patent Documents 1-3 disclose the use of trialkyl phosphate esters as solvents in electrolytes, or their addition to conventional electrolytes. While the safety of secondary batteries can be improved by endowing the electrolyte with flame-retardant properties, the type and amount of trialkyl phosphate esters used do not necessarily result in satisfactory battery characteristics such as coulombic efficiency. One reason for the deterioration of secondary battery performance is that the electrolyte used is exposed to a strong electrochemical redox environment, which causes the phosphate ester to deteriorate. Therefore, in addition to phosphate esters, other compounds are also used to form a stable film on the electrode surface, thereby inhibiting electrolyte deterioration. For example, in Patent Document 4, in addition to phosphate esters, carboxylic acid esters are added to the electrolyte. Patent Documents 5 and 6 add carbonates with unsaturated bonds to the electrolyte, Patent Document 7 adds haloalkoxybenzenes to the electrolyte, Patent Document 8 adds cyclic phosphate esters to the electrolyte, and Patent Document 9 adds haloalkyl phosphate esters to the electrolyte. However, if the electrolyte disclosed in these patent documents is used, another problem arises: the resistance increases during charging and discharging because a stable film forms on the electrode surface. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 4-184870 [Patent Document 2] Japanese Patent Application Publication No. 7-114940 [Patent Document 3] Japanese Patent Application Publication No. 2001-307768 [Patent Document 4] Japanese Patent Application Publication No. 8-88023 [Patent Document 5] Japanese Patent Application Publication No. 11-260401 [Patent Document 6] Japanese Patent Application Publication No. 2002-203597 [Patent Document 7] Japanese Patent Application Publication No. 11-40193 [Patent Document 8] Japanese Patent Application Publication No. 2002-184459 [Patent Document 9] Japanese Patent Application Publication No. 2007-141760 [The problem the invention aims to solve] This invention was made in view of the aforementioned problems, and its object is to provide a flame-retardant non-aqueous electrolyte exhibiting good flame retardancy, as well as excellent cycle characteristics and electrical resistance characteristics, and a secondary battery using the same. [Means for solving the problems] The present invention was made by discovering that when using at least one of difluorophosphate and nitrate as an electrolyte and using a specific phosphate ester as a non-aqueous solvent, the difluorophosphate and nitrate are dissolved in the specific phosphate ester at a high concentration, and when the solution is used as an electrolyte, it exhibits good flame retardancy and excellent cycle and resistance characteristics. That is, in order to solve the aforementioned problems, the flame-retardant non-aqueous electrolyte of the present invention is characterized by comprising at least a non-aqueous solvent and an electrolyte dissolved in the aforementioned non-aqueous solvent. The aforementioned non-aqueous solvent comprises at least one of the following phosphate esters represented by the following chemical formulas (1) to (3). The aforementioned electrolyte comprises at least one of the following: difluorophosphate and nitrate. The content of the aforementioned phosphate ester is 20% by mass or more relative to the total mass of the aforementioned flame-retardant non-aqueous electrolyte. (where X) 1 ~X 3 Each of the following can be independently represented as a hydrocarbon group having 1 to 20 carbon atoms; a silyl group having 1 to 20 carbon atoms; a hydrocarbon group having 1 to 20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond; or a silyl group having 1 to 20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond, or X 1 ~X 3 The aforementioned hydrocarbon group having 1 to 20 carbon atoms; the aforementioned silyl group having 1 to 20 carbon atoms; the aforementioned hydrocarbon group having 1 to 20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond; or any of the aforementioned silyl groups having 1 to 20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond, and any combination thereof is bonded together to form a cyclic structure, Y 1 and Y 2 Each halogen atom is represented independently. In the aforementioned composition, preferably, the mole fraction of at least one of the aforementioned difluorophosphate and nitrate is 0.1 or more relative to the total number of moles of the aforementioned electrolyte. In the aforementioned composition, preferably at least one of the aforementioned difluorophosphate and the aforementioned nitrate is an alkali metal salt. Furthermore, in the aforementioned configuration, preferably at least one of the aforementioned difluorophosphate and nitrate is a lithium salt. In the aforementioned composition, the preferred phosphate esters are trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, diethyl monofluorophosphate, diethyl monochlorophosphate, ethyl difluorophosphate, ethyl dichlorophosphate, and diethyl phosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester. In the aforementioned configuration, the electrolyte is preferably composed of BF. 4 - PF 6 - N(CF) 3SO 2) 2 - orN(SO 2F) 2 - At least one of the other electrolytes that are anions. In the aforementioned composition, the aforementioned non-aqueous solvent is preferably selected from at least one of the group consisting of cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, lactone compounds, chain esters, nitrile compounds, amide compounds, uranium compounds, and uranium compounds. In the aforementioned composition, the non-aqueous solvent preferably includes at least one of propyl carbonate, ethyl carbonate, γ-butyrolactone, dimethyl sulfoxide, and tetraethylene glycol dimethyl ether. To address the aforementioned issues, the secondary battery of the present invention is characterized by comprising at least a flame-retardant non-aqueous electrolyte, a positive electrode, and a negative electrode. [Effects of the Invention] According to the present invention, by using at least one of the phosphate esters represented by the aforementioned chemical formulas (1) to (3) as a non-aqueous solvent, the flame retardancy of the flame-retardant electrolyte can be improved. Furthermore, by using at least one of the difluorophosphate and nitrate dissolved in the aforementioned non-aqueous solvent containing the phosphate ester as an electrolyte, the increase in resistance in the electrodes (positive and negative electrodes) after repeated charge and discharge can be suppressed, and a good capacity retention rate can be maintained even after repeated charge and discharge in long-term cycling, thus providing a flame-retardant non-aqueous electrolyte with excellent cycling characteristics and a secondary battery using it. Although the mechanism by which cycling and resistivity characteristics are improved is not yet clear, it is believed that the formation of a good film on the electrode (electrode active material layer) by at least one of the difluorophosphates and nitrates contained in the electrolyte prevents the electrolyte from being exposed to a strong electrochemical redox environment. This is thought to inhibit the degradation of phosphate esters in the electrolyte, thereby suppressing or improving the decrease in cycling and resistivity characteristics. (Flame-retardant non-aqueous electrolyte) The flame-retardant non-aqueous electrolyte of this embodiment (hereinafter also referred to as "non-aqueous electrolyte") contains at least a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent, and can be appropriately used as an electrolyte for secondary batteries such as lithium-ion secondary batteries. As a non-aqueous solvent, it uses at least one of the phosphate esters (hereinafter collectively referred to as "phosphate esters") represented by chemical formulas (1) to (3) described below. As an electrolyte, it uses at least one of the difluorophosphate and nitrate. During initial charging, an irreversible reaction occurs at the interface between the electrode and the non-aqueous electrolyte, resulting in the decomposition of the non-aqueous electrolyte. The types of additives added as needed, the properties of the film formed under charging and discharging conditions (such as thermal stability, ionic conductivity, morphology, and density), and the non-aqueous solvent and electrolyte in the electrode active material are considered to vary considerably. In this embodiment, by using phosphate esters as the non-aqueous solvent and at least one of difluorophosphate and nitrate as the electrolyte, an effective film can be formed on the electrode (electrode active material layer). Due to the properties of this film, it is believed that the cycle characteristics and resistance characteristics of the secondary battery can be improved. Furthermore, by using phosphate esters as the non-aqueous solvent, sufficient flame retardancy can be imparted to the non-aqueous electrolyte. <Non-aqueous solvent> [Phosphate ester] The non-aqueous solvent as described above includes at least one of the phosphate esters represented by the following chemical formulas (1) to (3). In chemical formulas (1) to (3), X 1 ~X 3 Each of the following can be independently represented: a hydrocarbon group; a silyl group; a hydrocarbon group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "hydrocarbon group having a halogen atom, etc."); or a silyl group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "silyl group having a halogen atom, etc."). Or X 1 ~X 3 The term refers to any of the following: a hydrocarbon group having 1 to 20 carbon atoms; a silyl group having 1 to 20 carbon atoms; a hydrocarbon group having 1 to 20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond; or a silyl group having 1 to 20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond, and any combination thereof is bonded together to form a cyclic structure. The aforementioned X 1 ~X 3The hydrocarbon group has 1 to 20 carbon atoms, preferably 1 to 10, and even more preferably 1 to 4. Furthermore, when a range of carbon atoms is expressed in this specification, the range means all integer carbon atoms contained within that range. Therefore, for example, a hydrocarbon group with "carbon atoms 1 to 3" refers to all hydrocarbon groups with 1, 2, and 3 carbon atoms. The aforementioned X 1 ~X 3 The silane has 1 to 20 carbon atoms, preferably 1 to 10, and even more preferably 1 to 4. The aforementioned X 1 ~X 3 A hydrocarbon group containing halogen atoms refers to a functional group in which some or all of the hydrogen atoms in the hydrocarbon group are replaced by halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms. Among the aforementioned hydrocarbon groups containing halogen atoms with 1 to 20 carbon atoms, hydrocarbon groups with halogen atoms with 1 to 10 carbon atoms are preferred, and hydrocarbon groups with halogen atoms with 1 to 4 carbon atoms are even more preferred. The aforementioned X 1 ~X 3 A hydrocarbon group containing heteroatoms refers to a functional group in which some or all of the hydrogen and carbon atoms are replaced by heteroatoms. The aforementioned heteroatoms represent atoms such as oxygen, nitrogen, and sulfur. Among hydrocarbon groups containing heteroatoms with 1 to 20 carbon atoms, hydrocarbon groups containing heteroatoms with 1 to 10 carbon atoms are preferred, and hydrocarbon groups containing heteroatoms with 1 to 4 carbon atoms are even more preferred. The aforementioned X 1 ~X 3 The term "hydrocarbon group with unsaturated bonds" refers to a hydrocarbon group having, for example, a double or triple bond between carbon atoms. The number of unsaturated bonds is preferably in the range of 1 to 10, more preferably in the range of 1 to 5, and particularly preferably in the range of 1 to 3. The aforementioned X 1 ~X 3 A silyl group having halogen atoms refers to a functional group in which some or all of the hydrogen atoms are replaced by halogen atoms. Examples of halogen atoms are fluorine, chlorine, bromine, and iodine atoms. Among the aforementioned silyl groups having halogen atoms with 1 to 20 carbon atoms, silyl groups having halogen atoms with 1 to 10 carbon atoms are preferred, and silyl groups having halogen atoms with 1 to 4 carbon atoms are even more preferred. The aforementioned X 1 ~X 3A heteroatom-containing silane refers to a functional group in which some or all of the hydrogen and carbon atoms are substituted with heteroatoms. The aforementioned heteroatoms represent atoms such as oxygen, nitrogen, and sulfur. Among heteroatom-containing silanes with 1 to 20 carbon atoms, it is more preferably a heteroatom-containing silane with 1 to 10 carbon atoms, and even more preferably a heteroatom-containing silane with 1 to 4 carbon atoms. The aforementioned X 1 ~X 3 The term "silyl group with unsaturated bonds" refers to silyl groups, for example, those with double or triple bonds between carbon atoms. The number of unsaturated bonds is preferably in the range of 1 to 10, more preferably in the range of 1 to 5, and particularly preferably in the range of 1 to 3. The aforementioned hydrocarbon groups and hydrocarbon groups having halogen atoms are not particularly limited, but examples include chain alkyl groups such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, hexyl, heptyl, and octyl; cyclic alkyl groups such as cyclopentyl and cyclohexyl; 2-iodoethyl, 2-bromoethyl, 2-chloroethyl, 2-fluoroethyl, 1,2-diiodoethyl, 1,2-dibromoethyl, 1,2-dichloroethyl, 1,2-difluoroethyl, 2,2-diiodoethyl, 2,2-dibromoethyl, 2,2- Chain-like halogenated alkyl groups such as dichloroethyl, 2,2-difluoroethyl, 2,2,2-tribromoethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, and hexafluoro-2-propyl; cyclic halogenated alkyl groups such as 2-iodocyclohexyl, 2-bromocyclohexyl, 2-chlorocyclohexyl, and 2-fluorocyclohexyl; chain-like alkenyl groups such as 2-propenyl, isopropenyl, 2-butenyl, and 3-butenyl; cyclic alkenyl groups such as 2-cyclopentenyl, 2-cyclohexenyl, and 3-cyclohexenyl; 2 -Protynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl and 4-pentynyl, etc., chain-like ynyl groups; aryl groups such as phenyl; alkoxyphenyl groups such as 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl and 4-phenoxyphenyl, etc.; 2-iodophenyl, 2-bromophenyl, 2-chlorophenyl, 2-fluorophenyl, 3-iodophenyl, 3-bromophenyl, 3-chlorophenyl, 3-fluorophenyl, 4-iodophenyl, 4- Halogenated phenyl groups such as bromophenyl, 4-chlorophenyl, 4-fluorophenyl, 3,5-diiodophenyl, 3,5-dibromophenyl, 3,5-dichlorophenyl and 3,5-difluorophenyl; naphthyl groups such as 1-naphthyl, 2-naphthyl and 3-amino-2-naphthyl; 2-methoxyethyl, 2-(2-methoxyethoxy)ethyl, 2-(2-(2-methoxyethoxy)ethoxy)ethyl and 2-(2-(2-(2-methoxyethoxy)ethoxy)ethyl)ethyl, etc. In chemical formulas (2) and (3), Y 1 and Y 2Each halogen atom is represented independently. Examples of halogen atoms include those of fluorine, chlorine, bromine, and iodine. Phosphate esters represented by chemical formula (1) include, for example, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triphenyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, dipropyl methyl phosphate, propyl dimethyl phosphate, methyl butyl phosphate, dibutyl phosphate, methyl dibutyl phosphate, pentyl dimethyl phosphate, dipentyl methyl phosphate, dimethyl hexyl phosphate, methyl dihexyl phosphate, methyl diheptyl phosphate, and dimethyl heptayl phosphate. Diethyl phosphate dipropyl, diethyl phosphate propyl, diethyl phosphate butyl, dibutyl phosphate ethyl, diethyl phosphate dipentyl, diethyl phosphate pentyl, diethyl phosphate dihexyl, diethyl phosphate hexyl, ethyl phosphate hexyl, diethyl phosphate hexyl, diethyl phosphate hexyl, diethyl phosphate dipropyl, dibutyl phosphate propyl, dibutyl phosphate dipentyl, dibutyl phosphate pentyl, dibutyl phosphate dihexyl, dibutyl phosphate diheptyl, dibutyl phosphate hexyl phosphate pentyl, dihexyl phosphate pentyl, phosphorus Heptahydrate pentyl phosphate, diheptyl phosphate pentyl phosphate, diheptyl phosphate hexyl phosphate, heptahydrate dihexyl phosphate, ethyl phosphate methyl propyl phosphate, ethyl phosphate methyl butyl ester, ethyl phosphate methyl pentyl ester, ethyl phosphate hexyl ester methyl ester, ethyl phosphate heptahydrate methyl ester, tri(2,2,2-trifluoroethyl) phosphate, (2,2,2-trichloroethyl) phosphate, tri(2,2,2-tribromoethyl) phosphate, tri(2,2,2-triiodoethyl) phosphate, tri(1,1,1,3,3,3) phosphate (-Hexafluoroisopropyl) phosphate, tris(1,1,1,3,3,3-hexachloroisopropyl) phosphate, tris(1,1,1,3,3,3-hexabromoisopropyl) phosphate, tris(1,1,1,3,3,3-hexaiodoisopropyl) phosphate, diethyl phosphate (2,2,2-trifluoroethyl) phosphate, ethyl phosphate (2,2,2-trifluoroethyl) phosphate, diethyl phosphate (1,1,1,3,3,3-hexafluoroisopropyl) phosphate, bis(1,1,1,3,3,3-hexafluoroisopropyl) phosphate, bis(1,1,1,3,3,3,3-hexafluoroisopropyl) phosphate3-Hexafluoroisopropyl) ethyl phosphate, tris(2-methoxyethyl) phosphate, tris(2-(2-methoxyethoxy)ethyl) phosphate, phosphoric acid, tris(2-(2-(2-methoxyethoxy)ethyl) phosphate, tris(2-(2-(2-(2-methoxyethoxy)ethoxy)ethyl) phosphate, diethyl phosphate (2-methoxyethyl) ester, diethyl phosphate (2-(2-methoxyethoxy)ethyl) ester, diethyl phosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, diethyl phosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, diethyl phosphate (2-(2-(2-methoxyethoxy)ethoxy) ethyl) ester, diethyl phosphate (2-(2-(2-(2-methoxyethoxy)ethoxy) ethyl) ester Ethyl phosphate esters include bis(2-methoxyethyl) phosphate, bis(2-(2-methoxyethoxy)ethyl) phosphate, bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl) phosphate, bis(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) phosphate, tri(trimethylsilyl) phosphate, tri(trimethylbutyl) phosphate, tri(triphenylsilyl) phosphate, tri(dimethylphenylsilyl) phosphate, and tri(dimethylvinylsilyl) phosphate. These phosphate esters can be used alone or in combination with two or more. Furthermore, among the phosphate esters represented by the exemplified chemical formula (1), from the viewpoint of easy availability, trimethyl phosphate, triethyl phosphate, triisopropyl phosphate and tributyl phosphate are preferred, more preferably trimethyl phosphate, triethyl phosphate and tributyl phosphate, even more preferably triethyl phosphate and trimethyl phosphate, and especially preferably triethyl phosphate. Phosphate esters represented by chemical formula (2), specifically examples include dimethyl monofluorophosphate, diethyl monofluorophosphate, dipropyl monofluorophosphate, diisopropyl monofluorophosphate, dibutyl monofluorophosphate, dipentyl monofluorophosphate, diheptyl monofluorophosphate, bis(2,2,2-trifluoroethyl) monofluorophosphate, bis(1,1,1,3,3,3-hexafluoroisopropyl) monofluorophosphate, bis(2-methoxyethyl) monofluorophosphate, bis(2-(2-methoxyethoxy)ethyl) monofluorophosphate, and bis(2-(2-(2-methoxyethoxy)ethyl) monofluorophosphate. (2-(2-(2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, dimethyl monochlorophosphate, diethyl monochlorophosphate, dipropyl monochlorophosphate, diisopropyl monochlorophosphate, dibutyl monochlorophosphate, dipentyl monochlorophosphate, diheptyl monochlorophosphate, bis(2,2,2-trifluoroethyl) monochlorophosphate, bis(1,1,1,3,3,3-hexafluoroisopropyl) monochlorophosphate, bis(2-methoxyethyl) monochlorophosphate, bis(2-(2-methoxyethoxy)ethyl) monochlorophosphate Ester, bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl) monochlorophosphate, bis(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) monochlorophosphate, dimethyl monobromophosphate, diethyl monobromophosphate, dipropyl monobromophosphate, diisopropyl monobromophosphate, dibutyl monobromophosphate, dipentyl monobromophosphate, diheptyl monobromophosphate, bis(2,2,2-trifluoroethyl) monobromophosphate, bis(1,1,1,3,3,3-hexafluoroisopropyl) monobromophosphate, bis(2-methoxyethyl) monobromophosphate ) ester, bis(2-(2-methoxyethoxy)ethyl) monobromophosphate, bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl) monobromophosphate, bis(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) monobromophosphate, dimethyl monoiodophosphate, diethyl monoiodophosphate, dipropyl monoiodophosphate, diisopropyl monoiodophosphate, dibutyl monoiodophosphate, dipentyl monoiodophosphate, diheptyl monoiodophosphate, bis(2,2,2-trifluoroethyl) monoiodophosphate, bis(1,1,1,3,3,3-Hexafluoroisopropyl) ester, monoiodophosphate bis(2-methoxyethyl) ester, monoiodophosphate bis(2-(2-methoxyethoxy)ethyl) ester, monoiodophosphate bis(2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, monoiodophosphate bis(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) ester, monofluorophosphate bis(trimethylsilyl) ester, monochlorophosphate bis(trimethylsilyl) ester, monobromophosphate bis(trimethylsilyl) ester, iodophosphate bis(trimethylsilyl) ester, monofluorophosphate bis(triethylsilyl) ester Phosphate esters include bis(triethylsilyl) monochlorophosphate, bis(triethylsilyl) monobromophosphate, bis(triethylsilyl) monoiodophosphate, bis(dimethylphenylsilyl) monofluorophosphate, bis(dimethylphenylsilyl) monochlorophosphate, bis(dimethylphenylsilyl) monobromophosphate, bis(dimethylphenylsilyl) monoiodophosphate, bis(dimethylvinylsilyl) monofluorophosphate, bis(dimethylvinylsilyl) monochlorophosphate, bis(dimethylvinylsilyl) monobromophosphate, and bis(dimethylvinylsilyl) monoiodophosphate. These phosphate esters can be used alone or in combination with two or more. Furthermore, among the phosphate esters represented by the exemplified chemical formula (2), based on the viewpoints of ease of acquisition and electrochemical stability, dimethyl monochlorophosphate, diethyl monochlorophosphate, dimethyl monofluorophosphate, and diethyl monofluorophosphate are preferred, and dimethyl monofluorophosphate and diethyl monofluorophosphate are even more preferred. Phosphate esters represented by chemical formula (3) include, for example, methyl difluorophosphate, ethyl difluorophosphate, propyl difluorophosphate, isopropyl difluorophosphate, butyl difluorophosphate, pentyl difluorophosphate, hexyl difluorophosphate, heptyl difluorophosphate, (2,2,2-trifluoroethyl) difluorophosphate, (1,1,1,3,3,3-hexafluoroisopropyl) difluorophosphate, (2-methoxyethyl) difluorophosphate, (2-(2-methoxyethoxy)ethyl) difluorophosphate, (2-(2-(2-methoxyethoxy)ethoxy)ethyl) difluorophosphate, (2-(2-(2-methoxyethoxy)ethoxy)ethyl) difluorophosphate, and methyl difluorophosphate. Ester, ethyl dichlorophosphate, propyl dichlorophosphate, isopropyl dichlorophosphate, butyl dichlorophosphate, pentyl dichlorophosphate, hexyl dichlorophosphate, heptyl dichlorophosphate, (2,2,2-trifluoroethyl) dichlorophosphate, (1,1,1,3,3,3-hexafluoroisopropyl) dichlorophosphate, (2-methoxyethyl) dichlorophosphate, (2-(2-methoxyethoxy)ethyl) dichlorophosphate, (2-(2-(2-methoxyethoxy)ethoxy)ethyl) dichlorophosphate, (2-(2-(2-methoxyethoxy)ethoxy)ethyl) dichlorophosphate, methyl dibromophosphate, ethyl dibromophosphate, propyl dibromophosphate, isopropyl dibromophosphate, dibromophosphate Butyl phosphate, pentyl dibromophosphate, hexyl dibromophosphate, heptyl dibromophosphate, (2,2,2-trifluoroethyl) dibromophosphate, (1,1,1,3,3,3-hexafluoroisopropyl) dibromophosphate, (2-methoxyethyl) dibromophosphate, (2-(2-methoxyethoxy)ethyl) dibromophosphate, (2-(2-(2-methoxyethoxy)ethoxy)ethyl) dibromophosphate, (2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) dibromophosphate, methyl diiodophosphate, ethyl diiodophosphate, propyl diiodophosphate, isopropyl diiodophosphate, butyl diiodophosphate, pentyl diiodophosphate, hexyl diiodophosphate, heptyl diiodophosphate, heptyl diiodophosphate Diiodophosphate (2,2,2-trifluoroethyl) ester, diiodophosphate (1,1,1,3,3,3-hexafluoroisopropyl) ester, diiodophosphate (2-methoxyethyl) ester, diiodophosphate (2-(2-methoxyethoxy)ethyl) ester, diiodophosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, diiodophosphate (2-(2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, methyl chlorofluorophosphate, ethyl chlorofluorophosphate, propyl chlorofluorophosphate, isopropyl chlorofluorophosphate, pentyl chlorofluorophosphate, hexyl chlorofluorophosphate, heptyl chlorofluorophosphate, 2,2,2-trifluoroethyl) ester, chlorofluorophosphate (1,1,1,3,3,3-hexafluoroisopropyl) ester3-Hexafluoroisopropyl) ester, chlorofluorophosphate (2-methoxyethyl) ester, chlorofluorophosphate (2-(2-methoxyethoxy)ethyl) ester, chlorofluorophosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, chlorofluorophosphate (2-(2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) ester, methyl bromochlorophosphate, ethyl bromofluorophosphate, propyl bromofluorophosphate, isopropyl bromofluorophosphate, pentyl bromofluorophosphate, hexyl bromofluorophosphate, heptyl bromofluorophosphate, (2,2,2-trifluoroethyl) ester, bromofluorophosphate (1,1,1,3,3, 3-Hexafluoroisopropyl) ester, bromofluorophosphate (2-methoxyethyl) ester, bromofluorophosphate (2-(2-methoxyethoxy)ethyl) ester, bromofluorophosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, bromofluorophosphate (2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) ester, methyl fluoroiodide phosphate, ethyl fluoroiodide, propyl fluoroiodide phosphate, isopropyl fluoroiodide phosphate, pentyl fluoroiodide phosphate, hexyl fluoroiodide phosphate, heptyl fluoroiodide phosphate, 2,2,2-trifluoroethyl fluoroiodide phosphate, 1,1,1,3,3, 3-Hexafluoroisopropyl) ester, fluoroiodide phosphate (2-methoxyethyl) ester, chlorofluorophosphate (2-(2-methoxyethoxy)ethyl) ester, fluoroiodide phosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, fluoroiodide phosphate (2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) ester, bromochlorophosphate methyl ester, bromochlorophosphate ethyl ester, bromochlorophosphate propyl ester, bromochlorophosphate isopropyl ester, bromochlorophosphate pentyl ester, bromochlorophosphate hexyl ester, bromochlorophosphate heptyl ester, bromochlorophosphate (2,2,2-trifluoroethyl) ester, bromochlorophosphate (1,1,1,3,3, 3-Hexafluoroisopropyl) ester, bromochlorophosphate (2-methoxyethyl) ester, bromochlorophosphate (2-(2-methoxyethoxy)ethyl) ester, bromochlorophosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, bromochlorophosphate (2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl) ester, chloroiodine phosphate methyl ester, chloroiodine phosphate ethyl ester, chloroiodine phosphate propyl ester, chloroiodine isopropyl ester, chloroiodine phosphate pentyl ester, chloroiodine phosphate hexyl ester, chloroiodine phosphate heptyl ester, chloroiodine phosphate (2,2,2-trifluoroethyl) ester, chloroiodine phosphate (1,1,1,3,3,3-Hexafluoroisopropyl) ester, chloroiodine phosphate (2-methoxyethyl) ester, chlorofluorophosphate (2-(2-methoxyethoxy)ethyl) ester, chloroiodine phosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester, chloroiodine phosphate (2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl ester, trimethyl difluorophosphate, trimethyl dichlorophosphate, trimethyl dibromophosphate, trimethyl diiodophosphate, triethyl difluorophosphate, triethyl dichlorophosphate, triethyl dibromophosphate, triethyl diiodophosphate, triethyl diiodophosphate Dimethyl phenyl silicate difluorophosphate, dimethyl phenyl silicate dichlorophosphate, dimethyl phenyl silicate dibromophosphate, dimethyl phenyl silicate diiodophosphate, dimethyl vinyl silicate difluorophosphate, dimethyl vinyl silicate dichlorophosphate, dimethyl vinyl silicate dibromophosphate, dimethyl vinyl silicate diiodophosphate, trimethyl fluorochlorophosphate, trimethyl fluorobromophosphate, trimethyl fluoroiodophosphate, triethyl fluorochlorophosphate, triethyl fluorobromophosphate, triethyl fluoroiodophosphate, etc. These phosphate esters can be used alone or in combination with two or more. Furthermore, among the phosphate esters represented by the exemplified chemical formula (3), based on the viewpoints of ease of acquisition and electrochemical stability, methyl dichlorophosphate, ethyl dichlorophosphate, methyl difluorophosphate, and diethyl difluorophosphate are preferred, and methyl difluorophosphate and diethyl difluorophosphate are even more preferred. The aforementioned phosphate ester content, relative to the total mass of the non-aqueous electrolyte, is 20% by mass or more, preferably 20% by mass or more and 95% by mass or less, more preferably 30% by mass or more and 80% by mass or less, and even more preferably 40% by mass or more and 70% by mass or less. By setting the phosphate ester content within these ranges, good flame retardancy can be imparted to the non-aqueous electrolyte. [Other Non-Aqueous Solvents] Besides phosphate esters, other non-aqueous solvents may also be included. There are no particular limitations on other non-aqueous solvents; examples include cyclic carbonates, linear carbonates, cyclic ethers, linear ethers, lactones, linear esters, nitriles, amides, sulfonates, and sulfenes. These other non-aqueous solvents may be used alone or in combination with two or more. Furthermore, among these other non-aqueous solvents, carbonates are preferred from the viewpoint that they can generally be used as non-aqueous solvents for secondary batteries. The aforementioned cyclic carbonates are not particularly limited, and examples include, for instance, ethyl carbonate, propyl carbonate, and butyl carbonate. These cyclic carbonates may be used alone or in combination of two or more. The aforementioned chain carbonates are not particularly limited, and examples include dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate. These chain carbonates may be used alone or in combination of two or more. The aforementioned cyclic ethers are not particularly limited, and examples include tetrahydrofuran, 2-methyltetrahydrofuran, etc. These cyclic ethers can be used alone or in combination of two or more. The aforementioned chain ethers are not particularly limited, and examples include, for instance, dimethoxyethane, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. These chain ethers can be used alone or in combination of two or more. The aforementioned lactone compounds are not particularly limited, and examples include, for instance, γ-butyrolactone. The aforementioned chain esters are not particularly limited, and examples include methyl propionate, methyl acetate, ethyl acetate, methyl formate, etc. These chain esters can be used alone or in combination of two or more. The aforementioned nitrile compounds are not particularly limited, and examples include, for instance, acetonitrile. The aforementioned acetamide compounds are not particularly limited, and examples include, for instance, dimethylformamide. The aforementioned ion compounds are not particularly limited, and examples include cyclobutane and methylcyclobutane. These ion compounds may be used alone or in combination of two or more. Furthermore, among other non-aqueous solvents, those in which at least a portion of the hydrogen atoms of the hydrocarbon group contained in the molecule are replaced by fluorine atoms are preferred. Among the other non-aqueous solvents exemplified, propyl carbonate, ethyl carbonate, γ-butyrolactone, dimethyl sulfoxide, and tetraethylene glycol dimethyl ether are preferred, based on their ease of acquisition and to improve the performance of the secondary battery. Furthermore, based on the viewpoint of improving the charging efficiency of the secondary battery, cyclic carbonates such as ethyl carbonate and propyl carbonate, and chain carbonates such as dimethyl carbonate and methyl ethyl carbonate are preferred. <Electrolytes> [Difluorophosphates and nitrates] Electrolytes include at least one of difluorophosphates and nitrates as described above. Preferred difluorophosphates and nitrates are those exhibiting solubility for phosphate esters. Here, "solubility" in this specification means, for example, that more than 0.05 g of difluorophosphate and / or nitrate dissolves in 100 g of a non-aqueous solvent at 25°C. From the perspective of solubility in non-aqueous solvents and the characteristics of secondary batteries, difluorophosphates and nitrates, which are alkali metal ions, are preferred as cations. Examples of alkali metal ions include lithium ions, sodium ions, potassium ions, rubidium ions, and cesium ions. Among these alkali metal ions, lithium ions, sodium ions, and potassium ions are preferred from the perspective of the characteristics of secondary batteries and resource availability. The concentration of the electrolyte relative to the aforementioned non-aqueous solvent is preferably in the range of 0.1M to 4M, more preferably in the range of 0.2M to 1.5M, and even more preferably in the range of 0.5M to 1.2M. By setting the electrolyte concentration to 0.1M or higher, insufficient conductivity of the non-aqueous electrolyte can be prevented, thus preventing a decrease in resistivity. On the other hand, by setting the electrolyte concentration to 4M or lower, the viscosity of the non-aqueous electrolyte can be prevented from increasing due to the electrolyte reaching saturation solubility in the non-aqueous solvent, thus preventing a decrease in the treatment properties of the non-aqueous electrolyte and the resistivity characteristics of the secondary battery. The mole fraction of difluorophosphate and / or nitrate relative to the total mole count of the electrolyte is preferably 0.1 or higher, more preferably 0.1 or higher and 1.0 or lower, even more preferably 0.2 or higher and 0.8 or lower, and particularly preferably 0.3 or higher and 0.5 or lower. By setting the mole fraction of difluorophosphate and / or nitrate to 0.1 or higher, the cycle characteristics and resistance characteristics of the secondary battery can be further improved. [Other Electrolytes] As mentioned above, other electrolytes besides difluorophosphate and nitrate may be used in combination. There are no particular limitations on what constitutes other electrolytes; examples include those containing PF... 6 - CF 3SO 3 - C 2F 5SO 3 - C 3F 7SO 3 - C 4F 9SO 3 - 、N(SO 2F) 2 - N(CF) 3SO 2) 2 - 、N(C 2F 5SO 2) 2 - N(CF) 3SO 2)(CF 3CO) - N(CF) 3SO 2)(C 2F 5SO 2) - or C(CF) 3SO 2) 3 - Anions such as boron chelates, phosphorus chelates, Lewis acid chelates, and phosphate salts can be used. These other electrolytes can be used alone or in combination of two or more. Further details about these other electrolytes will be provided later. The mole fraction of the other electrolytes relative to the total mole count of the electrolytes is preferably in the range of 0.1 to 0.9, more preferably 0.2 to 0.8, and even more preferably 0.3 to 0.5. By setting these ranges, the cycle characteristics and resistance characteristics of the secondary battery can be further improved. 1. Boron zirconia salts The aforementioned boron zirconia salts are specifically represented by the following chemical formula (4). In the aforementioned chemical formula (4), M n+ It indicates that it is selected from any one of the groups consisting of alkali metal ions, alkaline earth metal ions, aluminum ions, transition metal ions, and onium ions. The aforementioned alkali metal ions in chemical formula (4) are not particularly limited, and examples include lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, etc. One of these may be used alone, or two or more may be used together. Examples of alkaline earth metal ions mentioned above in chemical formula (4) include magnesium ions, calcium ions, strontium ions, and barium ions. One of these ions may be used alone, or two or more may be used together. The transition metal ions mentioned above in chemical formula (4) are not particularly limited, and examples include manganese ions, cobalt ions, nickel ions, chromium ions, copper ions, silver ions, molybdenum ions, tungsten ions, vanadium ions, etc. One of these may be used alone, or two or more may be used together. As an example of the onium ion mentioned above in chemical formula (4), ammonium ion (NH4+) can be cited. 4 + (i) First-order ammonium ions, second-order ammonium ions, third-order ammonium ions, fourth-order ammonium ions, fourth-order phosphonium ions, strontium ions, etc. The aforementioned first-order ammonium ions are not particularly limited, and examples include methylammonium ions, ethylammonium ions, propylammonium ions, isopropylammonium ions, etc. One of these may be used alone, or two or more may be used in combination. The aforementioned secondary ammonium ions are not specifically limited, but can include, for example, dimethylammonium ion, diethylammonium ion, dipropylammonium ion, dibutylammonium ion, ethylmethylammonium ion, methylpropylammonium ion, methylbutylammonium ion, propylbutylammonium ion, diisopropylammonium ion, etc. One of these can be used alone, or two or more can be used in combination. The aforementioned third-order ammonium ions are not specifically limited, and examples include, for instance, trimethylammonium ion, triethylammonium ion, tripropylammonium ion, tributylammonium ion, ethyldimethylammonium ion, diethylmethylammonium ion, triisopropylammonium ion, dimethylisopropylammonium ion, diethylisopropylammonium ion, dimethylpropylammonium ion, butyldimethylammonium ion, 1-methylpyrrolidone ion, 1-ethylpyrrolidone ion, 1-propylpyrrolidone ion, 1-butylpropylpyrrolidone ion, 1-methylimidazolium ion, 1-ethylimidazolium ion, 1-propylimidazolium ion, 1-butylimidazolium ion, pyrazoleon ion, 1-methylpyrazoleon ion, 1-ethylpyrazoleon ion, 1-propylpyrazoleon ion, 1-butylpyrazoleon ion, pyridineon ion, etc. One of these can be used alone, or two or more can be used in combination. There are no particular limitations on which quaternary ammonium ions can be included as the aforementioned quaternary ammonium ions. Examples include aliphatic quaternary ammonium ions, imidazolium ions, pyridinium ions, pyrazolium ions, and darazine ions. One of these ions may be used alone, or two or more may be used in combination. Furthermore, the aforementioned aliphatic quaternary ammonium compounds are not specifically limited, and examples include tetraethylammonium, tetrapropylammonium, tetraisopropylammonium, trimethylethylammonium, dimethyldiethylammonium, methyltriethylammonium, trimethylpropylammonium, trimethylisopropylammonium, tetrabutylammonium, trimethylbutylammonium, trimethylpentylammonium, trimethylhexylammonium, 1-ethyl-1-methylpyrrolidone, 1-butyl-1-methylpyrrolidone, 1-ethyl-1-methylpiperidone, 1-butyl-1-methylpiperidone, etc. One of these compounds may be used alone, or two or more may be used in combination. The aforementioned imidazolonium derivatives are not particularly limited, and examples include, for instance, 1,3-dimethyl-imidazolonium, 1-ethyl-3-methylimidazolonium, 1-n-propyl-3-methylimidazolonium, 1-n-butyl-3-methylimidazolonium, and 1-n-hexyl-3-methylimidazolonium. One of these derivatives may be used alone, or two or more may be used in combination. The aforementioned pyridinium class is not particularly limited, and examples include, for instance, 1-methylpyridinium, 1-ethylpyridinium, and 1-n-propylpyridinium. One of these may be used alone, or two or more may be used in combination. The aforementioned pyrazolium derivatives are not specifically limited, but examples include 1,2-dimethylpyrazolium, 1-methyl-2-ethylpyrazolium, 1-propyl-2-methylpyrazolium, 1-methyl-2-butylpyrazolium, 1-methylpyrazolium, 3-methylpyrazolium, 4-methylpyrazolium, 4-iodopyrazolium, 4-bromopyrazolium, 4-iodo-3-methylpyrazolium, 4-bromo-3-methylpyrazolium, and 3-trifluoromethylpyrazolium. One of these derivatives may be used alone, or two or more may be used in combination. The aforementioned darazinene class is not specifically limited, but examples include, for instance, 1-methyldarazinene, 1-ethyldarazinene, 1-propyldarazinene, 1-butyldarazinene, 3-methyldarazinene, 4-methyldarazinene, 3-methoxydarazinene, 3,6-dichlorodarazinene, 3,6-dichloro-4-methyldarazinene, 3-chloro-6-methyldarazinene, and 3-chloro-6-methoxydarazinene. One of these can be used alone, or two or more can be used in combination. There are no particular limitations on the quaternary phosphonium that can be used as the aforementioned quaternary phosphonium ion; examples include, for instance, benzyltriphenylphosphonium, tetraethylphosphonium, tetraphenylphosphonium, etc. One of these may be used alone, or two or more may be used in combination. There are no particular limitations on the strontium that can be used as the aforementioned strontium ion; examples include trimethylstrontium, triphenylstrontium, triethylstrontium, etc. One of these may be used alone, or two or more may be used in combination. As mentioned above, M n+ Among the examples listed, lithium ions, sodium ions, potassium ions, magnesium ions, calcium ions, tetraalkylammonium ions, alkylimidazolium ions, alkylpyrroleium ions, and alkylpyridinium ions are preferred based on ease of acquisition. L in the aforementioned chemical formula (4) 1 ~L 4 Each can be an independent combination of one or two of any chosen elements, representing the formation of a cyclic structure such as -OOC-COO-, -OOC-O-, -OOC-α-COO-, -O-α-O-, or -OOC-α-O-. α represents a hydrocarbon group with 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5; or a hydrocarbon group with 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5, and possessing heteroatoms, unsaturated bonds, or a cyclic structure. L 1 ~L 4 When a ring structure of -OOC-α-COO-, -O-α-O-, or -OOC-α-O- is present, each α may be different. Here, heteroatoms refer to oxygen, nitrogen, or sulfur atoms. As not specifically limited to the aforementioned α, examples include linear alkyl groups such as methylene, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl; halogenated linear alkyl groups such as iodomethylene, diiodomethylene, bromomethylene, dibromomethylene, fluoromethylene, difluoromethylene, iodoethyl, 1,1-diiodoethyl, 1,2-diiodoethyl, triiodoethyl, tetraiodoethyl, chloroethyl, 1,1-dichloroethyl, 1,2-dichloroethyl, trichloroethyl, tetrachloroethyl, fluoroethyl, 1,1-difluoroethyl, 1,2-difluoroethyl, trifluoroethyl, and tetrafluoroethyl; cyclic hydrocarbon groups such as cyclohexyl, phenyl, benzyl, naphthyl, anthracene, naphthyl, and pentaphenyl; and those partially or wholly substituted with halogens. Furthermore, when the aforementioned α is 1,2-epoxyphenyl, -O-α-O- represents a phthalate group, and -O-α-COO- represents a salicylate group. And in the aforementioned chemical formula (4), L 1 ~L 4 Each of the following is an alkyl group having a halogen atom and 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5: an alkoxy group having 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5: an alkyl group having at least any one of a halogen atom, a heteroatom, an unsaturated bond, or a cyclic structure; or an alkoxy group having at least any one of a halogen atom, a heteroatom, an unsaturated bond, or a cyclic structure, within the range of 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5: an alkoxy group having at least any one of a halogen atom, a heteroatom, an unsaturated bond, or a cyclic structure. Here, the aforementioned halogen atom refers to a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. And the term heteroatom refers to an oxygen atom, a nitrogen atom, or a sulfur atom. The aforementioned L 1 ~L 4Specific examples include chain alkyl groups such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, hexyl, heptyl, and octyl; cyclic alkyl groups such as cyclopentyl and cyclohexyl; iodomethyl, bromomethyl, chloromethyl, fluoromethyl, diiodomethyl, dibromomethyl, dichloromethyl, difluoromethyl, triiodomethyl, tribromomethyl, trichloromethyl, trifluoromethyl, 2-iodoethyl, 2-bromoethyl, 2-chloroethyl, 2-fluoroethyl, 1,2-diiodoethyl, 1,2-dibromoethyl, 1,2-dichloroethyl, 1,2-difluoroethyl, 2,2-diiodoethyl, 2,2-dibromoethyl, 2,2-dichloroethyl, 2,2-difluoroethyl, 2,2,2-tribromoethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, 1,1,1,3,3, Chain-like haloalkyl groups such as 3-hexafluoro-2-propyl; cyclic haloalkyl groups such as 2-iodocyclohexyl, 2-bromocyclohexyl, 2-chlorocyclohexyl, and 2-fluorocyclohexyl; chain-like alkenyl groups such as 2-propenyl, isopropenyl, 2-butenyl, and 3-butenyl; cyclic alkenyl groups such as 2-cyclopentenyl, 2-cyclohexenyl, and 3-cyclohexenyl; chain-like alkynyl groups such as 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl; aryl groups such as phenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl, and 4-phenoxyphenyl; 2-iodophenyl, 2-bromophenyl, 2-chlorophenyl, 2-fluorophenyl, 3-iodophenyl, 3-bromophenyl, 3-chlorophenyl, and 3- Halogenated phenyl groups including fluorophenyl, 4-iodophenyl, 4-bromophenyl, 4-chlorophenyl, 4-fluorophenyl, 3,5-diiodophenyl, 3,5-dibromophenyl, 3,5-dichlorophenyl, and 3,5-difluorophenyl; chain alkoxy groups including methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy; cyclic alkoxy groups including cyclopentoxy and cyclohexoxy; 2-iodoethoxy, 2-bromoethoxy, 2-chloroethoxy, 2-fluoroethoxy, 1,2-diiodoethoxy, 1,2-dibromoethoxy, 1,2-dichloroethoxy, 1,2-difluoroethoxy, 2,2-diiodoethoxy, 2,2-dibromoethoxy, 2,2-dichloroethoxy, 2,2-difluoroethoxy, 2,2,2-tribromoethoxy, and 2,2,2-trichloroethoxy. Chain-like halogenated alkyl groups such as 2,2,2-trifluoroethoxy and 1,1,1,3,3,3-hexafluoro-2-propoxy; cyclic halogenated alkyl groups such as 2-iodocyclohexyloxy, 2-bromocyclohexyloxy, 2-chlorocyclohexyloxy, and 2-fluorocyclohexyloxy; chain-like alkenylalkoxy groups such as 2-propynoxy, isopropynoxy, 2-butenoxy, and 3-butenoxy; cyclic alkenylalkoxy groups such as 2-cyclopentenoxy, 2-cyclohexenoxy, and 3-cyclohexenoxy; chain-like alkynylalkoxy groups such as 2-propynoxy, 1-butynoxy, 2-butynoxy, 3-butynoxy, 1-pentynoxy, 2-pentynoxy, 3-pentynoxy, and 4-pentynoxy; and aryloxy groups such as phenoxy, 3-methylphenoxy, 4-methylphenoxy, and 3,5-dimethylphenoxy.Halogenated phenoxy groups including 2-iodophenoxy, 2-bromophenoxy, 2-chlorophenoxy, 2-fluorophenoxy, 3-iodophenoxy, 3-bromophenoxy, 3-chlorophenoxy, 3-fluorophenoxy, 4-iodophenoxy, 4-bromophenoxy, 4-chlorophenoxy, 4-fluorophenoxy, 3,5-diiodophenoxy, 3,5-dibromophenoxy, 3,5-dichlorophenoxy, and 3,5-difluorophenoxy. The aforementioned L 1 ~L 4 They are independent of each other and can be of the same kind or different kinds. Moreover, the functional base groups exemplified above are merely examples and are not limited to this. Furthermore, in the aforementioned chemical formula (4), the aforementioned n represents the valence number. For example, when the aforementioned M is a monovalent cation, n=1; when it is a divalent cation, n=2; and when it is a trivalent cation, n=3. Specific examples of boron complex salts represented by the aforementioned chemical formula (4) include, for example, bis(oxalate) borate, bis(malonate) borate, bis(salicylate) borate, bis[1,2'-phthalate(2)-O,O'] borate, oxalate malonate borate, oxalate salicylate borate, oxalate [1,2'-phthalate(2)-O,O'] borate, diiodooxalate borate, dibromooxalate borate, dichlorooxalate borate, difluorooxalate borate, iodochlorooxalate borate, iodobromooxalate borate, iodofluorooxalate borate, bromochlorooxalate borate, bromofluorooxalate borate, chlorofluorooxalate borate, diiodomalonate borate, dibromomalonate borate, dichloromalonate borate, difluoromalonate borate, diiodomalonate borate, dichloromalonate borate, di ...chloromalonate borate, diiodomalonate borate, dichloromalonate borate, dichloromalonate borate, diiodomalonate borate, dichloromalonate borate, diiodomalonate borate, dichloromalonate borate, dichloromalonate borate, diiodomalonate borate, dichloromalonate borate, dichloromalonate borate, dichloromalonate borate, dichloromalonate borate, dichloromalonate borate, dichloromalonate borate, dichloromalonate bor Iodine chloromalonic acid borate, iodobromomalonic acid borate, iodofluoromalonic acid borate, bromochloromalonic acid borate, bromofluoromalonic acid borate, chlorofluoromalonic acid borate, diiodosalicylic acid borate, dibromosalicylic acid borate, dichlorosalicylic acid borate, difluorosalicylic acid borate, iodochlorosalicylic acid borate, iodobromosalicylic acid borate, iodofluorosalicylic acid borate, bromochlorosalicylic acid borate, bromofluorosalicylic acid borate, chlorofluorosalicylic acid borate, diiodo[1,2'-phthalate(2)-O,O']borate, dibromo[1,2'-phthalate(2)-O,O']borate, dichloro[1,2'-phthalate(2)-O,O']borate, difluoro[1, 2'-Phenylbenzene(2)-O,O']borate, Iodochloro[1,2'-Phenylbenzene(2)-O,O']borate, Iodobromo[1,2'-Phenylbenzene(2)-O,O']borate, Iodofluoro[1,2'-Phenylbenzene(2)-O,O']borate, Bromochloro[1,2'-Phenylbenzene(2)-O,O']borate, Bromofluoro[1,2'-Phenylbenzene(2)-O,O']borate, Chlorofluoro[1,2'-Phenylbenzene(2)-O,O']borate, Tetraiodoborate, Tetrabromoborate, Tetrachloroborate, Tetrafluoroborate, Iodotribromoborate, Iodotrichloroborate, Iodotrifluoroborate, Diiododibromoborate, Diiodo Dichloroborate, diiododifluoroborate, triiodobromoborate, triiodochloroborate, triiodofluoroborate, bromotrichloroborate, bromotrifluoroborate, dibromodichloroborate, dibromodifluoroborate, tribromochloroborate, tribromofluoroborate, chlorotrifluoroborate, dichlorodifluoroborate, iodobromochlorofluoroborate, tetramethylborate, tetraethylborate, tetraphenylborate, tetramethoxyborate, tetraethoxyborate, tetraphenoxyborate, ethyldimethylphenylborate, butylethylmethylphenylborate, ethoxydimethoxyphenoxyborate, dimethyloxalate borate, dimethylmalonic acid borate, dimethyl salicylate borate, dimethyl[1,2'-phenylenediate (2)-O,[O'] borates, including ethylmethyloxalate borate, phenylmethyloxalate borate, iodomethyloxalate borate, bromomethyloxalate borate, chloromethyloxalate borate, fluoromethyloxalate borate, iodoethyloxalate borate, bromoethyloxalate borate, chloroethyloxalate borate, fluoroethyloxalate borate, ethoxymethoxyoxalate borate, iodomethoxyoxalate borate, bromomethoxyoxalate borate, chloromethoxyoxalate borate, or fluoromethoxyoxalate borate, all of which possess a boron complex anion. Among the exemplified boron chelates, based on the viewpoint of ease of acquisition, it is preferable to be a boron chelate containing a boron chelate anion, such as bis(oxalate)borate, bis(salicylate)borate, or bis[1,2'-phthalate(2)-O,O']borate. Furthermore, the specific example of the boron zeolite represented by the aforementioned chemical formula (4) is merely illustrative and is not limited to this embodiment. 2. Phosphorus zirconia salts The aforementioned phosphorus zirconia salts are specifically represented by the following chemical formula (5). M in the aforementioned chemical formula (5) n+ The valence n is the same as that described in the aforementioned chemical formula (4). Therefore, its detailed description is omitted. L in the aforementioned chemical formula (5) 5 ~L 10 Each is independent, and any combination of at least one of them can be chosen to represent the formation of a cyclic structure of -OOC-COO-, -OOC-O-, -OOC-β-COO-, -O-β-O-, or -OOC-β-O-. In this case, β refers to a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5; or a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 10, more preferably 1 to 5, and having heteroatoms, unsaturated bonds, or a cyclic structure. The aforementioned L 5 ~L 10 When a ring structure of -OOC-β-COO-, -O-β-O-, or -OOC-β-O- is present in two or more groups, each β group may be different. Here, heteroatoms refer to oxygen, nitrogen, or sulfur atoms. As not specifically limited as mentioned above, examples of linear alkyl groups include methylene, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl; halogenated linear alkyl groups including iodomethylene, diiodomethylene, bromomethylene, dibromomethylene, fluoromethylene, difluoromethylene, iodoethyl, 1,1-diiodoethyl, 1,2-diiodoethyl, triiodoethyl, tetraiodoethyl, chloroethyl, 1,1-dichloroethyl, 1,2-dichloroethyl, trichloroethyl, tetrachloroethyl, fluoroethyl, 1,1-difluoroethyl, 1,2-difluoroethyl, trifluoroethyl, and tetrafluoroethyl; cyclic hydrocarbon groups such as cyclohexyl, phenyl, benzyl, naphthyl, anthracene, naphthyl, and pentaphenyl; and those partially or wholly substituted with halogens. Furthermore, when the aforementioned β is 1,2-epoxyphenyl, -O-β-O- represents a phthalate ester group, and -O-β-COO- represents a salicylate ester group. Furthermore, L in the aforementioned chemical formula (5) 5 ~L 10 Each of the following can be independently represented: halogen atom; alkyl group; alkoxy group; alkathio group; alkyl group having at least one of a halogen atom, heteroatom, or unsaturated bond (hereinafter referred to as "alkyl group having a halogen atom, etc."); alkoxy group having at least one of a halogen atom, heteroatom, or unsaturated bond (hereinafter referred to as "alkoxy group having a halogen atom, etc."); or alkathio group having at least one of a halogen atom, heteroatom, or unsaturated bond (hereinafter referred to as "alkathio group having a halogen atom, etc."). The number of carbon atoms in the aforementioned alkyl group, alkoxy group, alkathio group, alkyl group having a halogen atom, alkoxy group having a halogen atom, and alkathio group having a halogen atom is in the range of 1 to 20, preferably 1 to 10, more preferably 1 to 4. The number of unsaturated bonds is preferably in the range of 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3. The aforementioned halogen atoms and heteroatoms are the same as those described in the aforementioned chemical formula (4). Furthermore, in alkyl groups having halogen atoms, alkoxy groups having halogen atoms, and alkylthio groups having halogen atoms, the aforementioned halogen atoms and heteroatoms are part or all of the hydrogen in these functional groups and may be substituted by any one of the halogen atoms and / or heteroatoms. The aforementioned L 5 ~L 10Specific examples include chain alkyl groups such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, hexyl, heptyl, and octyl; cyclic alkyl groups such as cyclopentyl and cyclohexyl; iodomethyl, bromomethyl, chloromethyl, fluoromethyl, diiodomethyl, dibromomethyl, dichloromethyl, difluoromethyl, triiodomethyl, tribromomethyl, trichloromethyl, trifluoromethyl, 2-iodoethyl, 2-bromoethyl, 2-chloroethyl, 2-fluoroethyl, 1,2-diiodoethyl, 1,2-dibromoethyl, 1,2-dichloroethyl, 1,2-difluoroethyl, 2,2-diiodoethyl, 2,2-dibromoethyl, 2,2-dichloroethyl, 2,2-difluoroethyl, 2,2,2-tribromoethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, and hexafluoro-2 Chain-like halogenated alkyl groups such as propyl; cyclic halogenated alkyl groups such as 2-iodocyclohexyl, 2-bromocyclohexyl, 2-chlorocyclohexyl, and 2-fluorocyclohexyl; chain-like alkenyl groups such as 2-propenyl, isopropenyl, 2-butenyl, and 3-butenyl; cyclic alkenyl groups such as 2-cyclopentenyl, 2-cyclohexenyl, and 3-cyclohexenyl; chain-like alkynes such as 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl; aryl groups such as phenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl, and 4-phenoxyphenyl; 2-iodophenyl, 2-bromophenyl, 2-chlorophenyl, 2-fluorophenyl, 3-iodophenyl, 3-bromophenyl, 3-chlorophenyl, and 3-fluorophenyl. Halogenated phenyl groups including phenyl, 4-iodophenyl, 4-bromophenyl, 4-chlorophenyl, 4-fluorophenyl, 3,5-diiodophenyl, 3,5-dibromophenyl, 3,5-dichlorophenyl, 3,5-difluorophenyl, etc.; chain alkoxy groups including methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, etc.; cyclic alkoxy groups including cyclopentoxy, cyclohexoxy, etc.; 2-iodoethoxy, 2-bromoethoxy, 2-chloroethoxy, 2-fluoroethoxy, 1,2-diiodoethoxy, 1,2-dibromoethoxy, 1,2-dichloroethoxy, 1,2-difluoroethoxy, 2,2-diiodoethoxy, 2,2-dibromoethoxy, 2,2-dichloroethoxy, 2,2-difluoroethoxy, 2,2,2-tribromoethoxy, 2,2,2-trichloroethoxy Chain-like halogenated alkoxy groups such as ethoxy, 2,2,2-trifluoroethoxy, and hexafluoro-2-propoxy; cyclic halogenated alkoxy groups such as 2-iodocyclohexyloxy, 2-bromocyclohexyloxy, 2-chlorocyclohexyloxy, and 2-fluorocyclohexyloxy; chain-like alkenylalkoxy groups such as 2-propenoxy, isopropenoxy, 2-butenoxy, and 3-butenoxy; cyclic alkenylalkoxy groups such as 2-cyclopentenoxy, 2-cyclohexenoxy, and 3-cyclohexenoxy; chain-like alkynylalkoxy groups such as 2-propynoxy, 1-butynoxy, 2-butynoxy, 3-butynoxy, 1-pentynoxy, 2-pentynoxy, 3-pentynoxy, and 4-pentynoxy; and aryloxy groups such as phenoxy, 3-methylphenoxy, 4-methylphenoxy, and 3,5-dimethylphenoxy.Halogenated phenoxy groups including 2-iodophenoxy, 2-bromophenoxy, 2-chlorophenoxy, 2-fluorophenoxy, 3-iodophenoxy, 3-bromophenoxy, 3-chlorophenoxy, 3-fluorophenoxy, 4-iodophenoxy, 4-bromophenoxy, 4-chlorophenoxy, 4-fluorophenoxy, 3,5-diiodophenoxy, 3,5-dibromophenoxy, 3,5-dichlorophenoxy, and 3,5-difluorophenoxy; alkylthio groups including methylthio, ethylthio, propylthio, butylthio, isopropylthio, pentylthio, and hexylthio. Furthermore, examples of phosphorus compounds represented by the aforementioned chemical formula (5) include readily available lithium difluorobis(oxalato) phosphate, sodium difluorobis(oxalato) phosphate, lithium tetrafluorobis(oxalato) phosphate, and sodium tetrafluorobis(oxalato) phosphate. 3. Lewis acid fused salts: The Lewis acid fused anion in the aforementioned Lewis acid fused salts is composed of an inorganic or organic anion and BF. 3. PF 5. AlF It is formed from third-degree Lewis acid. The aforementioned inorganic anions are not specifically limited, but can be exemplified by, for example, carbonate anion, sulfate anion, fluorosulfate anion, chlorosulfate anion, bromosulfate anion, iodosulfate anion, phosphate anion, monofluorophosphate anion, monochlorophosphate anion, monobromophosphate anion, monoiodophosphate anion, difluorophosphate anion, dichlorophosphate anion, dibromophosphate anion, diiodophosphate anion, etc. The aforementioned organic anions are not particularly limited, and examples include organic carboxylic acid anions, organic sulfonic acid anions, and organic phosphoric acid anions. Furthermore, organic carboxylic acid anions are not particularly limited, and examples include formic acid anions, acetate anions, propionic acid anions, butyric acid anions, valeric acid anions, trifluoroacetic acid anions, pentafluoropropionic acid anions, heptafluorobutyric acid anions, and nonafluorovaleric acid anions. Also, organic sulfonic acid anions are not particularly limited, and examples include methanesulfonic acid anions, ethanesulfonic acid anions, propanesulfonic acid, butanesulfonic acid anions, trifluoromethanesulfonic acid anions, pentafluoroethanesulfonic acid anions, heptafluoropropanesulfonic acid anions, and nonafluorobutanesulfonic acid anions. Organic phosphoric acid anions are not particularly limited, and examples include octyl phosphate anions, dodecyl phosphate anions, octadecyl phosphate anions, phenyl phosphate anions, and nonylphenyl phosphate anions. Lewis acids that form Lewis acid schistosides are not particularly limited, and can be exemplified by those represented by the following chemical formulas (6) to (8). In the aforementioned chemical formula (6), A 1 ~A 3Each of the following can be independently represented: a hydrogen atom; a halogen atom; an alkyl group; an alkoxy group; an alkyl group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkyl group having a halogen atom, etc."); an alkoxy group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkoxy group having a halogen atom, etc."); or an alkoxy group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkoxy group having a halogen atom, etc."). The aforementioned alkyl group, alkoxy group, alkoxy group, alkyl group having a halogen atom, alkoxy group having a halogen atom, and alkoxy group having a halogen atom, etc., have a carbon number in the range of 1 to 20, preferably 1 to 10, more preferably 1 to 4. Furthermore, the number of unsaturated bonds is preferably in the range of 1 to 10, more preferably in the range of 1 to 5, and particularly preferably in the range of 1 to 3. The aforementioned A 1 ~A 3More specifically, examples include chain alkyl groups such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, hexyl, heptyl, and octyl; cyclic alkyl groups such as cyclopentyl and cyclohexyl; iodomethyl, bromomethyl, chloromethyl, fluoromethyl, diiodomethyl, dibromomethyl, dichloromethyl, difluoromethyl, triiodomethyl, tribromomethyl, trichloromethyl, trifluoromethyl, 2-iodoethyl, 2-bromoethyl, 2-chloroethyl, 2-fluoroethyl, 1,2-diiodoethyl, 1,2-dibromoethyl, 1,2-dichloroethyl, 1,2-difluoroethyl, 2,2-diiodoethyl, 2,2-dibromoethyl, 2,2-dichloroethyl, 2,2-difluoroethyl, 2,2,2-tribromoethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, and hexafluoro-2 Chain-like halogenated alkyl groups such as propyl; cyclic halogenated alkyl groups such as 2-iodocyclohexyl, 2-bromocyclohexyl, 2-chlorocyclohexyl, and 2-fluorocyclohexyl; chain-like alkenyl groups such as 2-propenyl, isopropenyl, 2-butenyl, and 3-butenyl; cyclic alkenyl groups such as 2-cyclopentenyl, 2-cyclohexenyl, and 3-cyclohexenyl; chain-like alkynes such as 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl; aryl groups such as phenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl, and 4-phenoxyphenyl; 2-iodophenyl, 2-bromophenyl, 2-chlorophenyl, 2-fluorophenyl, 3-iodophenyl, 3-bromophenyl, 3-chlorophenyl, and 3-fluorophenyl. Halogenated phenyl groups including phenyl, 4-iodophenyl, 4-bromophenyl, 4-chlorophenyl, 4-fluorophenyl, 3,5-diiodophenyl, 3,5-dibromophenyl, 3,5-dichlorophenyl, 3,5-difluorophenyl, etc.; chain alkoxy groups including methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, etc.; cyclic alkoxy groups including cyclopentoxy, cyclohexoxy, etc.; 2-iodoethoxy, 2-bromoethoxy, 2-chloroethoxy, 2-fluoroethoxy, 1,2-diiodoethoxy, 1,2-dibromoethoxy, 1,2-dichloroethoxy, 1,2-difluoroethoxy, 2,2-diiodoethoxy, 2,2-dibromoethoxy, 2,2-dichloroethoxy, 2,2-difluoroethoxy, 2,2,2-tribromoethoxy, 2,2,2-trichloroethoxy Chain-like halogenated alkoxy groups such as ethoxy, 2,2,2-trifluoroethoxy, and hexafluoro-2-propoxy; cyclic halogenated alkoxy groups such as 2-iodocyclohexyloxy, 2-bromocyclohexyloxy, 2-chlorocyclohexyloxy, and 2-fluorocyclohexyloxy; chain-like alkenylalkoxy groups such as 2-propynoxy, isopropynoxy, 2-butenoxy, and 3-butenoxy; cyclic alkenylalkoxy groups such as 2-cyclopentenoxy, 2-cyclohexenoxy, and 3-cyclohexenoxy; chain-like alkynylalkoxy groups such as 2-propynoxy, 1-butynoxy, 2-butynoxy, 3-butynoxy, 1-pentynoxy, 2-pentynoxy, 3-pentynoxy, and 4-pentynoxy; and aryloxy groups such as phenoxy, 3-methylphenoxy, 4-methylphenoxy, and 3,5-dimethylphenoxy.Halogenated phenoxy groups including 2-iodophenoxy, 2-bromophenoxy, 2-chlorophenoxy, 2-fluorophenoxy, 3-iodophenoxy, 3-bromophenoxy, 3-chlorophenoxy, 3-fluorophenoxy, 4-iodophenoxy, 4-bromophenoxy, 4-chlorophenoxy, 4-fluorophenoxy, 3,5-diiodophenoxy, 3,5-dibromophenoxy, 3,5-dichlorophenoxy, and 3,5-difluorophenoxy; alkylthio groups including methylthio, ethylthio, propylthio, butylthio, isopropylthio, pentylthio, and hexylthio. In the aforementioned chemical formula (7), the aforementioned A 4 ~A 8 Each of the following can be independently represented: a hydrogen atom; a halogen atom; an alkyl group; an alkoxy group; an alkyl group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkyl group having a halogen atom, etc."); an alkoxy group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkoxy group having a halogen atom, etc."); or an alkoxy group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkoxy group having a halogen atom, etc."). The aforementioned alkyl group, alkoxy group, alkoxy group, alkyl group having a halogen atom, alkoxy group having a halogen atom, and alkoxy group having a halogen atom, etc., have a carbon number in the range of 1 to 20, preferably 1 to 10, more preferably 1 to 4. Furthermore, the number of unsaturated bonds is preferably in the range of 1 to 10, more preferably in the range of 1 to 5, and particularly preferably in the range of 1 to 3. The aforementioned A 4 ~A 8Unrestricted, specific examples include chain alkyl groups such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, hexyl, heptyl, octyl, etc.; cyclic alkyl groups such as cyclopentyl, cyclohexyl, etc.; iodomethyl, bromomethyl, chloromethyl, fluoromethyl, diiodomethyl, dibromomethyl, dichloromethyl, difluoromethyl, triiodomethyl, tribromomethyl, trichloromethyl, trifluoromethyl, 2-iodoethyl, 2-bromoethyl, 2-chloroethyl, 2-fluoroethyl, 1,2-diiodoethyl, 1,2-dibromoethyl, 1,2-dichloroethyl, 1,2-difluoroethyl, 2,2-diiodoethyl, 2,2-dibromoethyl, 2,2-dichloroethyl, 2,2-difluoroethyl, 2,2,2-tribromoethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, hexafluoro Chain-like haloalkyl groups such as 2-propyl; cyclic haloalkyl groups such as 2-iodocyclohexyl, 2-bromocyclohexyl, 2-chlorocyclohexyl, and 2-fluorocyclohexyl; chain-like alkenyl groups such as 2-propenyl, isopropenyl, 2-butenyl, and 3-butenyl; cyclic alkenyl groups such as 2-cyclopentenyl, 2-cyclohexenyl, and 3-cyclohexenyl; chain-like alkynes such as 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl; aryl groups such as phenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl, and 4-phenoxyphenyl; 2-iodophenyl, 2-bromophenyl, 2-chlorophenyl, 2-fluorophenyl, 3-iodophenyl, 3-bromophenyl, 3-chlorophenyl, and 3- Halogenated phenyl groups including fluorophenyl, 4-iodophenyl, 4-bromophenyl, 4-chlorophenyl, 4-fluorophenyl, 3,5-diiodophenyl, 3,5-dibromophenyl, 3,5-dichlorophenyl, and 3,5-difluorophenyl; chain alkoxy groups including methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy; cyclic alkoxy groups including cyclopentoxy and cyclohexoxy; 2-iodoethoxy, 2-bromoethoxy, 2-chloroethoxy, 2-fluoroethoxy, 1,2-diiodoethoxy, 1,2-dibromoethoxy, 1,2-dichloroethoxy, 1,2-difluoroethoxy, 2,2-diiodoethoxy, 2,2-dibromoethoxy, 2,2-dichloroethoxy, 2,2-difluoroethoxy, 2,2,2-tribromoethoxy, and 2,2,2-trichloroethoxy. Chain-like halogenated alkoxy groups such as ethoxy, 2,2,2-trifluoroethoxy, and hexafluoro-2-propoxy; cyclic halogenated alkoxy groups such as 2-iodocyclohexyloxy, 2-bromocyclohexyloxy, 2-chlorocyclohexyloxy, and 2-fluorocyclohexyloxy; chain-like alkenylalkoxy groups such as 2-propynoxy, isopropynoxy, 2-butenoxy, and 3-butenoxy; cyclic alkenylalkoxy groups such as 2-cyclopentenoxy, 2-cyclohexenoxy, and 3-cyclohexenoxy; chain-like alkynylalkoxy groups such as 2-propynoxy, 1-butynoxy, 2-butynoxy, 3-butynoxy, 1-pentynoxy, 2-pentynoxy, 3-pentynoxy, and 4-pentynoxy; and aryloxy groups such as phenoxy, 3-methylphenoxy, 4-methylphenoxy, and 3,5-dimethylphenoxy.Halogenated phenoxy groups including 2-iodophenoxy, 2-bromophenoxy, 2-chlorophenoxy, 2-fluorophenoxy, 3-iodophenoxy, 3-bromophenoxy, 3-chlorophenoxy, 3-fluorophenoxy, 4-iodophenoxy, 4-bromophenoxy, 4-chlorophenoxy, 4-fluorophenoxy, 3,5-diiodophenoxy, 3,5-dibromophenoxy, 3,5-dichlorophenoxy, and 3,5-difluorophenoxy; alkylthio groups including methylthio, ethylthio, propylthio, butylthio, isopropylthio, pentylthio, and hexylthio. In the aforementioned chemical formula (8), the aforementioned A 9 ~A 11 Each of the following can be independently represented: a hydrogen atom; a halogen atom; an alkyl group; an alkoxy group; an alkyl group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkyl group having a halogen atom, etc."); an alkoxy group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkoxy group having a halogen atom, etc."); or an alkoxy group having at least one of a halogen atom, a heteroatom, or an unsaturated bond (hereinafter referred to as "alkoxy group having a halogen atom, etc."). The aforementioned alkyl group, alkoxy group, alkoxy group, alkyl group having a halogen atom, alkoxy group having a halogen atom, and alkoxy group having a halogen atom, etc., have a carbon number in the range of 1 to 20, preferably 1 to 10, more preferably 1 to 4. Furthermore, the number of unsaturated bonds is preferably in the range of 1 to 10, more preferably in the range of 1 to 5, and particularly preferably in the range of 1 to 3. The aforementioned A 9 ~A 11Unrestricted, specific examples include chain alkyl groups such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, hexyl, heptyl, octyl, etc.; cyclic alkyl groups such as cyclopentyl, cyclohexyl, etc.; iodomethyl, bromomethyl, chloromethyl, fluoromethyl, diiodomethyl, dibromomethyl, dichloromethyl, difluoromethyl, triiodomethyl, tribromomethyl, trichloromethyl, trifluoromethyl, 2-iodoethyl, 2-bromoethyl, 2-chloroethyl, 2-fluoroethyl, 1,2-diiodoethyl, 1,2-dibromoethyl, 1,2-dichloroethyl, 1,2-difluoroethyl, 2,2-diiodoethyl, 2,2-dibromoethyl, 2,2-dichloroethyl, 2,2-difluoroethyl, 2,2,2-tribromoethyl, 2,2,2-trichloroethyl, 2,2,2-trifluoroethyl, hexafluoro Chain-like haloalkyl groups such as 2-propyl; cyclic haloalkyl groups such as 2-iodocyclohexyl, 2-bromocyclohexyl, 2-chlorocyclohexyl, and 2-fluorocyclohexyl; chain-like alkenyl groups such as 2-propenyl, isopropenyl, 2-butenyl, and 3-butenyl; cyclic alkenyl groups such as 2-cyclopentenyl, 2-cyclohexenyl, and 3-cyclohexenyl; chain-like alkynes such as 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl; aryl groups such as phenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl, and 4-phenoxyphenyl; 2-iodophenyl, 2-bromophenyl, 2-chlorophenyl, 2-fluorophenyl, 3-iodophenyl, 3-bromophenyl, 3-chlorophenyl, and 3- Halogenated phenyl groups including fluorophenyl, 4-iodophenyl, 4-bromophenyl, 4-chlorophenyl, 4-fluorophenyl, 3,5-diiodophenyl, 3,5-dibromophenyl, 3,5-dichlorophenyl, and 3,5-difluorophenyl; chain alkoxy groups including methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy; cyclic alkoxy groups including cyclopentoxy and cyclohexoxy; 2-iodoethoxy, 2-bromoethoxy, 2-chloroethoxy, 2-fluoroethoxy, 1,2-diiodoethoxy, 1,2-dibromoethoxy, 1,2-dichloroethoxy, 1,2-difluoroethoxy, 2,2-diiodoethoxy, 2,2-dibromoethoxy, 2,2-dichloroethoxy, 2,2-difluoroethoxy, 2,2,2-tribromoethoxy, and 2,2,2-trichloroethoxy. Chain-like halogenated alkoxy groups such as ethoxy, 2,2,2-trifluoroethoxy, and hexafluoro-2-propoxy; cyclic halogenated alkoxy groups such as 2-iodocyclohexyloxy, 2-bromocyclohexyloxy, 2-chlorocyclohexyloxy, and 2-fluorocyclohexyloxy; chain-like alkenylalkoxy groups such as 2-propynoxy, isopropynoxy, 2-butenoxy, and 3-butenoxy; cyclic alkenylalkoxy groups such as 2-cyclopentenoxy, 2-cyclohexenoxy, and 3-cyclohexenoxy; chain-like alkynylalkoxy groups such as 2-propynoxy, 1-butynoxy, 2-butynoxy, 3-butynoxy, 1-pentynoxy, 2-pentynoxy, 3-pentynoxy, and 4-pentynoxy; and aryloxy groups such as phenoxy, 3-methylphenoxy, 4-methylphenoxy, and 3,5-dimethylphenoxy.Halogenated phenoxy groups including 2-iodophenoxy, 2-bromophenoxy, 2-chlorophenoxy, 2-fluorophenoxy, 3-iodophenoxy, 3-bromophenoxy, 3-chlorophenoxy, 3-fluorophenoxy, 4-iodophenoxy, 4-bromophenoxy, 4-chlorophenoxy, 4-fluorophenoxy, 3,5-diiodophenoxy, 3,5-dibromophenoxy, 3,5-dichlorophenoxy, and 3,5-difluorophenoxy; alkylthio groups including methylthio, ethylthio, propylthio, butylthio, isopropylthio, pentylthio, and hexylthio. As a specific example of zeaxanthin represented by chemical formulas (6) to (8), BF is an example. 3. PF 5. AlF 3. AlCl 3. Furthermore, among Lewis acids represented by chemical formulas (6) to (8), those containing halogens in their chemical structure are preferred, based on the viewpoint that they exhibit stronger Lewis acidity. A specific example of such a Lewis acid is, for instance, BF₂. 3. PF 5. AlCl 3rd grade. As a cation in Lewis acid fused salts, similar to the aforementioned boron fused salts, it is selected from any one of the groups consisting of alkali metal ions, alkaline earth metal ions, aluminum ions, transition metal ions, and onium ions. Therefore, its detailed description is omitted. 4. Phosphate salts The aforementioned phosphate salts are specifically represented by the following chemical formula (9). The Mn+ and valence n in the aforementioned chemical formula (9) are the same as those in the aforementioned chemical formula (4). Therefore, its detailed description is omitted. In the aforementioned chemical formula (9), R 1 and R 2 Each can independently represent a hydrocarbon group having 1 to 20 carbon atoms; or a hydrocarbon group having 1 to 20 carbon atoms and possessing at least one of a halogen atom, a heteroatom, or an unsaturated bond. Alternatively, R 1 With R 2 It refers to any hydrocarbon group having 1 to 20 carbon atoms, or any hydrocarbon group having 1 to 20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond, which can bond together to form a ring structure. Examples of hydrocarbon groups or hydrocarbon groups containing halogen atoms include chain alkyl groups such as methyl, ethyl, propyl, butyl, isopropyl, pentyl, hexyl, heptyl, and octyl; cyclic alkyl groups such as cyclopentyl and cyclohexyl; chain halogenated alkyl groups such as 2-iodoethyl, 2-bromoethyl, 2-chloroethyl, 2-fluoroethyl, 1,2-diiodoethyl, 1,2-dibromoethyl, 1,2-dichloroethyl, 1,2-difluoroethyl, 2,2-diiodoethyl, 2,2-dibromoethyl, 2,2-dichloroethyl, 2,2-difluoroethyl, 2,2,2-tribromoethyl, 2,2,2-trichloroethyl, and hexafluoro-2-propyl; cyclic halogenated alkyl groups such as 2-iodocyclohexyl, 2-bromocyclohexyl, 2-chlorocyclohexyl, and 2-fluorocyclohexyl; and 2-propenyl, isopropenyl, 2-butenyl, and 3- Chain alkenyl groups such as butenyl; cyclic alkenyl groups such as 2-cyclopentenyl, 2-cyclohexenyl, and 3-cyclohexenyl; chain alkynes such as 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, and 4-pentynyl; aryl groups such as phenyl, 3-methoxyphenyl, 4-methoxyphenyl, 3,5-dimethoxyphenyl, and 4-phenoxyphenyl; 2-iodine Halogenated phenyl groups, including phenyl, 2-bromophenyl, 2-chlorophenyl, 2-fluorophenyl, 3-iodophenyl, 3-bromophenyl, 3-chlorophenyl, 3-fluorophenyl, 4-iodophenyl, 4-bromophenyl, 4-chlorophenyl, 4-fluorophenyl, 3,5-diiodophenyl, 3,5-dibromophenyl, 3,5-dichlorophenyl, 3,5-difluorophenyl, etc.; naphthyl groups, including 1-phenyl, 2-naphthyl, 3-amino-2-naphthyl, etc. Furthermore, the aforementioned halogen atom refers to an atom of fluorine, chlorine, bromine, or iodine, and some or all of the hydrogen atoms in the aforementioned hydrocarbon group may be replaced by any of these halogen atoms. Also, heteroatoms refer to atoms of oxygen, nitrogen, or sulfur, etc. In addition, the number of unsaturated bonds is preferably in the range of 1 to 10, more preferably in the range of 1 to 5, and particularly preferably in the range of 1 to 3. In addition, the aforementioned R 1 With R 2The aforementioned hydrocarbon groups or hydrocarbon groups having halogen atoms, etc., can bond together to form a ring structure. At this point, specific examples of the aforementioned hydrocarbon groups or hydrocarbon groups containing halogen atoms include, for example, straight-chain alkyl groups such as methylene, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl; halogen-containing straight-chain alkyl groups such as iodomethylene, diiodomethylene, bromomethylene, dibromomethylene, fluoromethylene, difluoromethylene, iodoethyl, 1,1-diiodoethyl, 1,2-diiodoethyl, triiodoethyl, tetraiodoethyl, chloroethyl, 1,1-dichloroethyl, 1,2-dichloroethyl, trichloroethyl, tetrachloroethyl, fluoroethyl, 1,1-difluoroethyl, 1,2-difluoroethyl, trifluoroethyl, and tetrafluoroethyl; cyclic hydrocarbon groups such as cyclohexyl, phenyl, benzyl, naphthyl, anthracene, naphthyl, and pentaphenyl; and those partially or wholly substituted with halogens. The aforementioned R 1 With R 2 The functional groups exemplified above may be the same or different from each other. Moreover, the functional groups exemplified above are merely illustrative and are not limited to them. Specific examples of anions in phosphate salts represented by the aforementioned chemical formula (9) include dimethyl phosphate anion, diethyl phosphate anion, dipropyl phosphate anion, bis(2,2,2-trifluoroethyl) phosphate anion, bis(1,1,1,3,3,3-hexafluoroisopropyl) phosphate anion, etc. Among other electrolytes such as boron chelate salts exemplified above, those with BF4 are preferred based on ease of acquisition. 4 - PF 6 - N(CF) 3SO 2) 2 - orN(SO 2F) 2 - Of which the cation is preferred, the one with BF is even better. 4 - PF 6 - orN(SO 2F) 2 - The cation is preferred. Furthermore, from the viewpoint of improving battery characteristics, it is preferable to have a power factor (PF). 6 - orN(SO 2F) 2 - Those containing cations. <Additives> In addition to the aqueous solvent and electrolyte, the non-aqueous electrolyte of this embodiment may also contain additives. There are no particular limitations on the additives, but examples include at least one compound selected from the group consisting of borate esters, acid anhydrides, cyclic carbonates having unsaturated bonds, cyclic carbonates having halogen atoms, cyclic sulfonates, amines having acetylacetic groups, and phosphorus compounds. 1. The borate esters used in this embodiment are not particularly limited in type, and various types can be selected to avoid impairing the characteristics of the non-aqueous electrolyte and the secondary battery using it. Specific examples include, for instance, trimethyl borate, triethyl borate, triisopropyl borate, tributyl borate, tripentyl borate, trihexyl borate, triheptyl borate, triphenyl borate, tri(2,2,2-iodoethyl) borate, tri(2,2,2-tribromoethyl) borate, tri(2,2,2-trichloroethyl) borate, tri(2,2,2-trifluoroethyl) borate, tri(4-iodophenyl) borate, tri(4-bromophenyl) borate, tri(4-chlorophenyl) borate, tri(4-fluorophenyl) borate, diethyl methyl borate, and dimethyl ethyl borate. 2. As for the aforementioned acid anhydride, there is no particular limitation on its type, as long as it does not impair the characteristics of the non-aqueous electrolyte of this embodiment and the secondary battery using it, and various types can be selected. Specific examples include linear carboxylic anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride, heptanoic anhydride, octanoic anhydride, nonanoic anhydride, decanoic anhydride, eicosanoic anhydride, docosanoic anhydride, benzoic anhydride, 4-methoxybenzoic anhydride, diphenylacetic anhydride, crotonic anhydride, cyclohexanecarboxylic anhydride, trans-oleic anhydride, isobutyric anhydride, isovaleric anhydride, lauric anhydride, linoleic anhydride, myristic anhydride, angelic anhydride, dichlorofluoroacetic anhydride, trichloroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, and 4-trifluoromethylbenzoic anhydride; phthalic anhydride, 3-acetylamine phthalic anhydride, 4,4'-carbonyl phthalic anhydride, 4,4'-biphthalic anhydride, 3-iodophthalic anhydride, and 3-bromophthalic anhydride. Dicarboxylic anhydride, 3-chlorophthalic anhydride, 3-fluorophthalic anhydride, 4-iodophthalic anhydride, 4-bromophthalic anhydride, 4-chlorophthalic anhydride, 4-fluorophthalic anhydride, 4,5-diiodophthalic anhydride, 4,5-dibromophthalic anhydride, 4,5-dichlorophthalic anhydride, 4,5-difluorophthalic anhydride, 4,4'-sulfonyldiphthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, exo-3,6-epoxyhexahydrophthalic anhydride, exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, tetraiodophthalic anhydride, tetrachlorophthalic anhydride, tetrafluorophthalic acid Anhydride, 4-tert-butylphthalic anhydride, 4-ethynylphthalic anhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, succinic anhydride, (R)-(+)-2-acetoxysuccinic anhydride, (S)-(-)-2-acetoxysuccinic anhydride, 2-buten-1-ylsuccinic anhydride, butylsuccinic anhydride, decylsuccinic anhydride, 2,3-dimethylsuccinic anhydride, 2-dodecen-1-ylsuccinic anhydride, dodecylsuccinic anhydride, octadecenylsuccinic anhydride, (2,7-octadien-1-yl)succinic anhydride, n-octylsuccinic anhydride, hexadecylsuccinic anhydride, maleic anhydride, 2,3-bis(2,4,5-trimethyl-3-ethynyl)maleic anhydride, 2-( -2-Carboxyethyl)-3-methyl-maleic anhydride, 2,3-dimethylmaleic anhydride, 2,3-diphenylmaleic anhydride, phenylmaleic anhydride, 4-pentene-1,2-dicarboxylic anhydride, 2,3-anthracene dicarboxylic anhydride, bicyclo[2,2,2]oct-5-ene-2,3-dicarboxylic anhydride, 4-bromo-1,8-naphthalene dicarboxylic anhydride, (±)-trans-1,2-cyclohexane dicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, 2,5-dibromo-3,4-thiophene dicarboxylic anhydride, 5,6-dihydro-1,4-dithia-2,3-dicarboxylic anhydride, 2,2'-biphenyl dicarboxylic anhydride, 4-methylcyclohexane-1,2-dicarboxylic anhydride, 3-methyl-4-cyclohexene-1,2-Dicarboxylic anhydride, 4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride, 2,3-naphthalenedicarboxylic anhydride, 3,4-thiophenedicarboxylic anhydride, 1,8-naphthalenedicarboxylic anhydride, 5-borneonene-2,3-dicarboxylic anhydride, 1,2-cyclopropanedicarboxylic anhydride, glutaric anhydride, 3,3-pentamethyleneglutaric anhydride, 2,2-dimethylglutaric anhydride, 3,3-dimethylglutaric anhydride, 3-methylglutaric anhydride, 2-o-phenylene Dimethylimine phthalic anhydride, 3,3-tetramethylene glutaric anhydride, N-methyl-o-o-aminobenzoic anhydride, 4-iodo-o-aminobenzoic anhydride, 4-bromo-o-aminobenzoic anhydride, 4-chloro-o-aminobenzoic anhydride, 4-fluoro-o-aminobenzoic anhydride, 5-iodo-o-aminobenzoic anhydride, 5-bromo-o-aminobenzoic anhydride, 5-chloro-o-aminobenzoic anhydride, 5-fluoro-o-aminobenzoic anhydride, itaconic anhydride, caronic anhydride Cyclic carboxylic anhydrides such as anhydride, citric acid anhydride, diethanolic anhydride, 1,2-naphthalenedicarboxylic anhydride, pyromellitic anhydride, hexachloronorbornene dicarboxylic anhydride, and 2,2,3,3,4,4-hexafluoroglutaric anhydride; linear sulfonic anhydrides such as trifluoromethanesulfonic anhydride and p-toluenesulfonic anhydride; cyclic sulfonic anhydrides such as 2-sulfobenzoic anhydride, tetraiodo-O-sulfobenzoic anhydride, tetrabromo-O-sulfobenzoic anhydride, tetrachloro-O-sulfobenzoic anhydride, and tetrafluoro-O-sulfobenzoic anhydride; and linear sulfonic anhydrides such as diphenylphosphine. Cyclic phosphonic anhydrides such as hypophosphite anhydride and 1-propanephosphonic anhydride, as well as 3,4-diiodophenylboronic anhydride, 3,4-dibromophenylboronic anhydride, 3,4-dichlorophenylboronic anhydride, 3,4-difluorophenylboronic anhydride, 4-iodophenyl anhydride, 4-bromophenylboronic anhydride, 4-chlorophenylboronic anhydride, 4-fluorophenylboronic anhydride, meta-triphenylboronic anhydride, 3,4,5-triiodophenylboronic anhydride, 3,4,5-tribromophenylboronic anhydride, 3,4,5-trichlorophenylboronic anhydride, and 3,4,5-trifluorophenylboronic anhydride, are included in this embodiment. Among these anhydrides, those with a cyclic structure are preferred in this embodiment, and those with intramolecular unsaturated bonds are even more preferred. Furthermore, based on the viewpoint of ease of acquisition and based on the viewpoint of cyclic structure and intramolecular unsaturated bonds, maleic anhydride is particularly preferred. 3. Cyclic carbonates with unsaturated bonds: As for the aforementioned cyclic carbonates with unsaturated bonds, there is no particular limitation on the type, and various types can be selected, as long as it does not impair the specific characteristics of the non-aqueous electrolyte of this embodiment and the secondary battery using it. The number of unsaturated bonds is preferably 1 to 10, more preferably 1 to 5, and particularly preferably 1 to 3. Examples of cyclic carbonates containing unsaturated bonds include, for instance, vinylene carbonate, iodinated vinylene carbonate, bromine vinylene carbonate, chlorovinyl vinylene carbonate, fluorovinylene carbonate, 1,2-diiodovinylene carbonate, 1,2-dibromovinylene carbonate, 1,2-dichlorovinylene carbonate, 1,2-difluorovinylene carbonate, methylvinylene carbonate, iodovinylene carbonate, brominevinylene carbonate, chloromethylvinylene carbonate, fluoromethylvinylene carbonate, dichloromethylvinylene carbonate, dibromomethylvinylene carbonate, dichloromethylvinylene carbonate, difluoromethylvinylene carbonate, triiodovinylene carbonate, tribromomethylvinylene carbonate, trichloromethylvinylene carbonate, trifluoromethylvinylene carbonate, ethylvinylene carbonate, propylvinylene carbonate, butylvinylene carbonate, dimethylvinylene carbonate, diethylvinylene carbonate, dipropylvinylene carbonate, and vinylethylene carbonate. Furthermore, based on the viewpoint of ease of acquisition, ethylene carbonate is preferred as the aforementioned cyclic carbonate with unsaturated bonds. 4. Cyclic carbonates containing halogen atoms: As for the aforementioned cyclic carbonates containing halogen atoms, there are no particular limitations on their type, and various types can be selected, provided that they do not impair the characteristics of the non-aqueous electrolyte of this embodiment and the secondary battery using it. Here, halogen atoms refer to fluorine, chlorine, bromine, or iodine atoms. Specific examples of cyclic carbonates containing halogen atoms include, for example, ethyl iodoethylene carbonate, ethyl bromoethylene carbonate, ethyl chloroethylene carbonate, ethyl fluoroethylene carbonate, 1,2-diiodoethylene carbonate, 1,2-dibromoethylene carbonate, 1,2-dichloroethylene carbonate, and 1,2-difluoroethylene carbonate. Furthermore, for ease of acquisition, ethyl chloroethylene carbonate and ethyl fluoroethylene carbonate are preferred among the aforementioned cyclic carbonates containing unsaturated bonds. 5. As for the aforementioned cyclic sulfonate, the type is not particularly limited, and various types can be selected, as long as they do not impair the characteristics of the non-aqueous electrolyte of this embodiment and the secondary battery using it. Specific examples of cyclic sulfonates include, for instance, 1,3-propanesulfonolactone, 2,4-butanesulfonolactone, 1,4-butanesulfonolactone, and ethyl sulfate. Furthermore, from the viewpoint of ease of acquisition, 1,3-propanesulfonolactone and ethyl sulfate are preferred as the aforementioned cyclic sulfonate. 6. Amines containing acetyl groups: As with the aforementioned amines containing acetyl groups, the types are not particularly limited, and various types can be selected, provided that the characteristics of the non-aqueous electrolyte and the secondary battery using it are not impaired. Specific examples of amines containing acetyl groups include, for example, N,N-dimethylacetylamine, N,N-diethylacetylamine, N,N-dipropylacetylamine, N,N-dibutylacetylamine, N,N-ethylmethylacetylamine, N,N-methylpropylacetylamine, and N,N-butylmethylacetylamine. However, these specific examples are merely illustrative, and this embodiment is not limited to them. 7. The phosphorus compound used is not particularly limited to any of the aforementioned phosphorus compounds, as long as it does not impair the characteristics of the non-aqueous electrolyte of this embodiment and the secondary battery using it. Examples include phosphine compounds and phosphonic acids. Specific examples of phosphine compounds include trimethylphosphine, triethylphosphine, triisopropylphosphine, and triphenylphosphine. Specific examples of phosphonic acids include dimethyl phosphite, diethyl phosphite, dibutyl phosphite, diphenyl phosphite, and bis(2,2,2-trifluoroethyl) phosphite. The additive content relative to the total mass of the non-aqueous electrolyte is preferably in the range of 0.05% to 50% by mass, more preferably in the range of 0.1% to 30% by mass, and particularly preferably in the range of 0.5% to 20% by mass. By setting the aforementioned content to 0.05% by mass or more, the additive effect can be achieved, resulting in a more stable film on the electrode surface. On the other hand, by setting the aforementioned addition amount to 20% by mass or less, excessive reduction in the solubility of the electrolyte in the non-aqueous electrolyte in the non-aqueous solvent can be suppressed. <Manufacturing of Non-Aqueous Electrolyte> The non-aqueous electrolyte of this embodiment can be manufactured, for example, by adding a specific amount of difluorophosphate and / or nitrate to a non-aqueous solvent containing at least one of the phosphate esters represented by chemical formulas (1) to (3). In this case, it is undesirable for the difluorophosphate and nitrate to become supersaturated and precipitate insoluble components. Furthermore, it is preferable to use a solvent with as few impurities as possible, such as a pre-purified non-aqueous solvent, difluorophosphate, and nitrate, without reducing manufacturing efficiency. When both difluorophosphate and nitrate are used as electrolytes, the order in which they are added to the non-aqueous solvent is not particularly limited and is arbitrary. Furthermore, when the non-aqueous electrolyte contains additives, the order in which the additives are added is not particularly limited and is arbitrary. <Other> Other conventional additives may also be added to the non-aqueous electrolyte of this embodiment. In this case, the content of other additives can be set appropriately as necessary. (Non-aqueous secondary battery) Next, the non-aqueous secondary battery of this embodiment (hereinafter referred to as "secondary battery") will be described below based on FIG1. ​​FIG1 is a schematic cross-sectional view of the secondary battery of this embodiment. The secondary battery of this embodiment can be applied to lithium-ion secondary batteries, sodium-ion secondary batteries, potassium-ion secondary batteries, magnesium-ion secondary batteries, calcium-ion secondary batteries, etc. As shown in Figure 1, the secondary battery has an internal space formed by a positive electrode can 4 and a negative electrode can 5, which houses a laminated body consisting of a positive electrode 1, a separator 3, a negative electrode 2, and a spacer 7, sequentially stacked from the positive electrode can 4. A spring 8 is inserted between the negative electrode can 5 and the spacer 7 to moderately press and fix the positive electrode 1 and the negative electrode 2 together. A non-aqueous electrolyte is impregnated between the positive electrode 1, the separator 3, and the negative electrode 2. With a gasket 6 separating the positive electrode can 4 and the negative electrode can 5, the two are clamped together, keeping the aforementioned laminated body in a sealed state. The material used as the positive electrode active material layer in positive electrode 1 is not particularly limited. Examples include transition metal compounds with a lithium-ion diffuseable structure, or oxides of transition metal compounds and lithium. A specific example is LiCoO. 2; LiNiO 2; LiMn 2O 4; Li 2MnO 3 and LiMeO 2 (Me represents any metallic element such as Mn, Co, or Ni) solid solution; LiFePO4 4; LiCoPO 4; LiMnPO4 4; Li 2FePO 4F; LiNi x Co y Mn z O 2(0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1); LiNi x Co y Al z O 2(0≦x≦1, 0≦y≦1, 0≦z≦1, x+y+z=1); LiFeF 3; TiO 2. V 2O 5. MoO Oxides of grade 3; TiS 2. Sulfides such as FeS; sulfur; conductive polymers such as polyacetylene, poly(p-phenylene), polyaniline, and polypyrrole; activated carbon; polymers that generate free radicals; carbon materials, etc. The positive electrode 1 can be obtained by pressing the aforementioned positive electrode active material together with a conventional conductive additive or binder, or by mixing the positive electrode active material together with a conventional conductive additive or binder in an organic solvent such as pyrrolidone, forming a paste, coating it onto a current collector such as aluminum foil, and then drying it. The material used as the negative electrode active material layer in the aforementioned negative electrode 2 is not particularly limited as long as it can absorb (deposit) and release (dissolve) metal ions. Examples include metal composite oxides, lithium metal, lithium alloys, sodium metal, sodium alloys, potassium metal, potassium alloys, magnesium, magnesium alloys, calcium metal, calcium alloys, aluminum, aluminum alloys, silicon, silicon-based alloys, tin-based alloys, metal oxides, conductive polymers such as polyacetylene, Li-Co-Ni materials, and carbon materials. Furthermore, when using alkali metals or alkaline earth metals at the negative electrode, metal ions corresponding to the type of secondary battery are dissolved in the electrolyte beforehand as an electrolyte. The metal deposited to the current collector during charging can also be used as the active material of the negative electrode. In this case, only a current collector is needed on the negative electrode side, which has the advantage of simplifying the battery structure. The aforementioned metal composite oxides are not specifically limited, for example, Li x Fe 2O 3(0≦x≦1), Li x WO 2(0≦x≦1), Sn x Me 1 1-x Me 2 y O z (Me 1 =Mn, Fe, Pb, Ge, Me 2 =Al, B, P, Si, elements in groups 1-3 of the periodic table, halogens, 0 < x ≦ 1, 1 ≦ y ≦ 3, 1 ≦ z ≦ 8, etc. The aforementioned metal oxides are not specifically limited, but examples include SnO and SnO2. 2. SiO 2 (0 < x < 2), PbO, PbO 2. Pb 2O 3. Pb 3O 4. Sb 2O 3. Sb 2O 4. Sb 2O 5. GeO, GeO 2. Bi 2O 3. Bi 2O 4. Bi 2O Level 5. The aforementioned carbon materials are not particularly limited, and examples include natural graphite, artificial graphite, borosilicate graphite, fluorinated graphite, carbon microspheres, pitch-based carbon fiber graphitization, carbon nanotubes, hard carbon, fullerene, graphene, etc. The negative electrode 2 can be made of the aforementioned electrode material in foil or powder form. In the case of powder form, it can be obtained by pressing and molding it together with conventional conductive additives or binders, or by mixing it together with conventional conductive additives or binders in an organic solvent such as pyrrolidone to form a paste, which is then coated onto a current collector such as copper foil and dried. In this embodiment of the lithium-ion secondary battery, a separator 3 is typically inserted between the positive electrode 1 and the negative electrode 2 to prevent short circuits. The material or shape of the separator 3 is not particularly limited, but it is preferably made of a material that allows the aforementioned non-aqueous electrolyte to pass through, is an insulator, and is chemically stable. Examples include microporous films, sheets, nonwoven fabrics, glass-coated surfaces, and glass fiber nonwoven fabrics made of various polymer materials. Specific examples of polymer materials include polyolefin polymers such as nylon (registered trademark), nitrocellulose, polyacrylonitrile, polyvinylidene fluoride, polyethylene, and polypropylene. From the viewpoint of electrochemical and chemical stability, polyolefin polymers are preferred. The optimal operating voltage of the lithium-ion secondary battery in this embodiment varies depending on the combination of the positive electrode 1 and the negative electrode 2, and it can generally be used in the range of 2.4 to 4.6V. The shape of the lithium-ion secondary battery in this embodiment is not particularly limited. In addition to the coin-shaped battery shown in Figure 1, other examples include cylindrical, square, and laminated types. The secondary battery of this embodiment possesses sufficient flame retardancy and exhibits excellent cycle and resistance characteristics. The non-aqueous electrolyte of this embodiment can be suitably used, for example, in lithium-ion secondary batteries. However, the lithium-ion secondary battery shown in Figure 1 is merely an illustrative example of one embodiment of the secondary battery of the present invention, and the secondary battery of the present invention is not limited thereto. [Example] The preferred embodiments of the present invention will be described in detail below. However, unless otherwise specifically stated, the scope of the present invention is not limited to the materials and dosages described in these embodiments. (Example 1) <Preparation of Non-Aqueous Electrolyte> In an argon-environment drying oven with a dew point below -70°C, ethyl carbonate (EC, manufactured by KISHIDA Chemical Co., Ltd., lithium battery grade) and triethyl phosphate (TEP, manufactured by Tokyo Chemical Co., Ltd.) were mixed to prepare a non-aqueous solvent. The mixing ratio of EC to TEP in the non-aqueous solvent was EC:TEP = 5:5 by volume. Secondly, in a non-aqueous solvent, LiPO4 is mixed as an electrolyte. 2F 2 and LiPF 6. At this time, LiPO 2F 2. The concentration is 0.5 moles / L, LiPF6 The concentration of 6 is 0.5 moles / L. This is used to prepare the non-aqueous electrolyte of this embodiment. (Example 2) In this embodiment, the mixing ratio of EC and TEP in the non-aqueous solvent is changed to EC:TEP = 7:3 by volume. Otherwise, the non-aqueous electrolyte of this embodiment is prepared in the same manner as in Example 1. (Example 3) In this example, only LiPO4 is used. 2F 2 was used as the electrolyte, and its concentration was changed to 1.0 moles / L. Otherwise, the non-aqueous electrolyte of this embodiment was prepared in the same manner as in Example 1. (Example 4) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. And only LiPO4 was used. 2F 2 was used as the electrolyte, and its concentration was changed to 1.0 moles / L. Otherwise, the non-aqueous electrolyte of this embodiment was prepared in the same manner as in Example 1. (Example 5) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. Otherwise, the non-aqueous electrolyte of this example was prepared in the same manner as in Example 1. (Example 6) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. Furthermore, the LiPO4 electrolyte was separately... 2F 2. The concentration was changed to 0.8 moles / L, and LiPF6 was used. The concentration was changed to 0.2 moles / L. Otherwise, the non-aqueous electrolyte of this example was prepared in the same manner as in Example 1. (Example 7) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. Furthermore, the LiPO4 electrolyte was separately... 2F 2. The concentration was changed to 0.2 moles / L, and the LiPF6 concentration was increased. The concentration was changed to 0.8 moles / L. Otherwise, the non-aqueous electrolyte of this example was prepared in the same manner as in Example 1. (Example 8) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. Furthermore, the LiPO4 electrolyte was separately... 2F 2. The concentration was changed to 0.1 moles / L, and LiPF6 was used. The concentration was changed to 0.9 moles / L. Otherwise, the non-aqueous electrolyte of this example was prepared in the same manner as in Example 1. (Example 9) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. LiPF6 was used as the electrolyte. 6 changed to LiTFSI(Li(CF) 3SO 2) 2N). In addition, the non-aqueous electrolyte of this embodiment was prepared in the same manner as in Example 1. (Example 10) In this example, a mixed solvent of ethyl carbonate and diethyl monofluorophosphate was used as the non-aqueous solvent, with the volume ratio of ethyl carbonate to diethyl monofluorophosphate changed to 2:8. Only LiPO4 was used. 2F 2 was used as the electrolyte, and its concentration was changed to 1.0 moles / L. Otherwise, the non-aqueous electrolyte of this embodiment was prepared in the same manner as in Example 1. (Example 11) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. And only LiNO3 was used. 3 was used as the electrolyte, and its concentration was set to 1.0 moles / L. Otherwise, the non-aqueous electrolyte of this embodiment was prepared in the same manner as in Example 1. (Example 12) In this example, a mixed solvent consisting of ethyl carbonate and diethyl phosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester was used as the non-aqueous solvent, and the volume ratio of ethyl carbonate to diethyl monofluorophosphate was changed to 2:8. Furthermore, only LiNO3 was used as the electrolyte. 3. The concentration was set to 1.0 moles / L. Otherwise, the non-aqueous electrolyte of this embodiment was prepared in the same manner as in Example 1. (Example 13) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to EC:TEP = 2:8 by volume. LiNO3 was used as the electrolyte. 3 and LiTFSI, with each concentration set at 0.5 moles / L. Otherwise, the non-aqueous electrolyte of this example was prepared in the same manner as in Example 1. (Example 14) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to a volume ratio of EC:TEP = 2:8. LiPO4 was used as the electrolyte. 2F 2 changed to LiNO 3. In addition, the non-aqueous electrolyte of this embodiment is prepared in the same manner as in Example 1. (Example 15) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to a volume ratio of EC:TEP = 2:8. LiPF6 was used as the electrolyte. 6 changed to LiNO 3. In addition, the non-aqueous electrolyte of this embodiment is prepared in the same manner as in Example 1. (Example 16) In this example, the mixing ratio of EC and TEP in the non-aqueous solvent was changed to a volume ratio of EC:TEP = 2:8. LiNO3 was used as the electrolyte. The concentration of LiPO3 was 0.33 moles / L. 2F 2. The concentration is 0.33 moles / L, LiPF6 The solution was mixed in a non-aqueous solvent at a concentration of 0.33 moles per liter. Otherwise, the non-aqueous electrolyte of this example was prepared in the same manner as in Example 1. (Example 17) In this example, a mixed solvent consisting of ethyl carbonate, triethyl phosphate, and diethyl monofluorophosphate was used as the non-aqueous solvent, and the volume ratio of ethyl carbonate to triethyl phosphate to diethyl monofluorophosphate was changed to 2:4:4. Furthermore, only LiPO4 was used as the electrolyte. 2F 2, and its concentration was changed to 1.0 moles / L. Apart from this, the non-aqueous electrolyte of this embodiment was prepared in the same manner as in Example 1. (Example 18) In this example, the non-aqueous solvent was changed to a solvent composed solely of trimethyl phosphate (TMP). Furthermore, LiNO3 was used as the electrolyte. 3. LiPO 2F 2 and LiPF 6. The concentrations of these substances are respectively LiNO 3 is 0.33 moles / liter, LiPO 2F 2 is 0.33 mol / L, LiPF6 6 is mixed in a non-aqueous solvent at a concentration of 0.33 moles / L. Otherwise, the non-aqueous electrolyte of this example is prepared in the same manner as in Example 1. (Example 19) In this example, a mixed solvent of propyl carbonate and triethyl phosphate was used as the non-aqueous solvent, with the volume ratio of propyl carbonate to triethyl phosphate changed to 2:8. Furthermore, LiNO3 was used as the electrolyte. 3. LiPO 2F 2 and LiPF 6. The concentrations of these substances are respectively LiNO 3 is 0.33 moles / liter, LiPO 2F 2 is 0.33 mol / L, LiPF6 6 is mixed in a non-aqueous solvent at a concentration of 0.33 moles / L. Otherwise, the non-aqueous electrolyte of this example is prepared in the same manner as in Example 1. (Example 20) In this example, a mixed solvent of γ-butyrolactone and triethyl phosphate was used as the non-aqueous solvent, with the volume ratio of γ-butyrolactone to triethyl phosphate changed to 5:5. Furthermore, LiNO3 was used as the electrolyte. 3. LiPO 2F 2 and LiPF 6. The concentrations of these substances are respectively LiNO 3 is 0.33 moles / liter, LiPO 2F 2 is 0.33 mol / L, LiPF6 6 is mixed in a non-aqueous solvent at a concentration of 0.33 moles / L. Otherwise, the non-aqueous electrolyte of this example is prepared in the same manner as in Example 1. (Example 21) In this example, a mixed solvent consisting of dimethyl sulfoxide (DMSO) and triethyl phosphate was used as the non-aqueous solvent, with the volume ratio of DMSO to triethyl phosphate changed to 2:8. Furthermore, LiNO3 was used as the electrolyte. 3. LiPO 2F 2 and LiPF 6. The concentrations of these substances are respectively LiNO 3 is 0.1 moles / liter, LiPO 2F 2 is 0.1 mol / L, LiPF6 6 is mixed in a non-aqueous solvent at a concentration of 0.8 moles / L. Otherwise, the non-aqueous electrolyte of this example is prepared in the same manner as in Example 1. (Comparative Example 1) In an argon-environment drying oven with a dew point below -70°C, ethyl carbonate (EC, manufactured by KISHIDA Chemical Co., Ltd., lithium battery grade) and dimethyl carbonate (DMC, manufactured by KISHIDA Chemical Co., Ltd.) were mixed to prepare a non-aqueous solvent. The mixing ratio of EC to DMC in the non-aqueous solvent was EC:DMC = 1:1 by volume. Secondly, LiPF6 will be used as an electrolyte. 6. Mixed in a non-aqueous solvent. At this point, LiPF6... The concentration was set to 1.0 moles / L. This was used to prepare the non-aqueous electrolyte for this comparative example. (Comparative Example 2) In this comparative example, the non-aqueous solvent was changed to EC solvent only. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Comparative Example 3) In this comparative example, a mixture of EC and TEP was used instead of a mixture of EC and DMC as the non-aqueous solvent. Furthermore, the mixing ratio of EC to TEP was set to EC:TEP = 9:1 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Comparative Example 4) In this comparative example, a mixture of EC and TEP was used as the non-aqueous solvent instead of the mixed solvent of EC and DMC. Furthermore, the mixing ratio of EC and TEP was set to EC:TEP = 8:2 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Comparative Example 5) In this comparative example, a mixture of EC and TEP was used as the non-aqueous solvent instead of the mixed solvent of EC and DMC. Furthermore, the mixing ratio of EC and TEP was set to EC:TEP = 7:3 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Comparative Example 6) In this comparative example, a mixture of EC and TEP was used as the non-aqueous solvent instead of the mixed solvent of EC and DMC. Furthermore, the mixing ratio of EC and TEP was set to EC:TEP = 5:5 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Comparative Example 7) In this comparative example, the mixing ratio of EC to TEP in the non-aqueous solvent was changed to EC:TEP = 9:1 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Example 1. (Comparative Example 8) In this comparative example, the mixing ratio of EC to TEP in the non-aqueous solvent was changed to EC:TEP = 8:2 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Example 1. (Comparative Example 9) In this comparative example, a mixture of EC and TEP was used as the non-aqueous solvent instead of the mixed solvent of EC and DMC. Furthermore, the mixing ratio of EC and TEP was set to EC:TEP = 2:8 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Comparative Example 10) In this comparative example, a mixture of EC and TEP was used as the non-aqueous solvent instead of the mixed solvent of EC and DMC. Furthermore, the mixing ratio of EC and TEP, by volume, was set as EC:TEP = 2:8. LiPF6 was used as the electrolyte. 6 was changed to LiTFSI. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Comparative Example 11) In this comparative example, a mixture of DMSO and TEP was used as the non-aqueous solvent instead of the mixed solvent of EC and DMC. Furthermore, the mixing ratio of DMSO to TEP was set to DMSO:TEP = 2:8 by volume. Otherwise, the non-aqueous electrolyte of this comparative example was prepared in the same manner as in Comparative Example 1. (Combustion Test of Non-Aqueous Electrolytes) First, glass filter paper (trade name: GC-50, manufactured by ADVANTECH Toyo Co., Ltd.) was soaked with the non-aqueous electrolytes of Examples 1, 2, 17, and Comparative Examples 1-8 to prepare test samples. Next, the flame of a gas torch was brought into contact with each test sample for 1 second, and the samples were observed to conduct a combustion test. The combustion test was performed twice. Furthermore, based on the results of the two combustion tests, the non-aqueous electrolyte was determined to be either flame-retardant or flammable. As a criterion, a result where the flame extinguished the instant the gas torch was removed was considered ○; a result where combustion continued after the flame was removed was considered ×; a result where the flame extinguished twice consecutively was considered flame-retardant; and other results were considered flammable. The results are shown in Table 4. As can be seen from Table 4, in Comparative Example 1, which used a mixed solvent of ethyl carbonate and dimethyl carbonate, and in Comparative Example 2, which used a solvent composed solely of ethyl carbonate, the non-aqueous electrolyte exhibited flammability. Therefore, it is presumed that when a mixed solvent composed of cyclic carbonates and chain carbonates, or a solvent composed solely of cyclic carbonates, is used as the non-aqueous solvent, the non-aqueous electrolyte exhibits flammability. Furthermore, in Comparative Examples 3, 4, 7, and 8, which used a mixed solvent composed of ethyl carbonate and triethyl phosphate, the non-aqueous electrolyte exhibited flammability. On the other hand, even when using a mixed solvent of ethyl carbonate and triethyl phosphate, the non-aqueous electrolyte can be made flame-retardant by setting the content of triethyl phosphate to 20% by mass or more relative to the total mass of the non-aqueous electrolyte. (Evaluation of Cyclic Characteristics) <Preparation of Coin Batteries> Using the non-aqueous electrolytes prepared in Examples 1-20 and Comparative Examples 5, 6, 9 and 10, coin-type lithium-ion secondary batteries (coin batteries) as shown in Figure 1 were prepared, and their electrochemical characteristics were evaluated. That is, the positive electrode system uses LiNi cut to a diameter of 11.3 mmφ. 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (manufactured by PIOTREK Co., Ltd.), the separator is made of glass filter paper (GC-50, manufactured by ADVANTECH Toyo Co., Ltd.). Furthermore, the negative electrode is made of lithium foil cut to a diameter of 13mmφ (manufactured by Honjo Metals Co., Ltd.). Then, the positive electrode, separator, and negative electrode are sequentially stacked to form a laminate, and after being impregnated with the non-aqueous electrolyte prepared in Examples 1-20 and Comparative Examples 5, 6, 9, and 10, respectively, the laminate is sealed to manufacture coin batteries. All assembly of the coin batteries is carried out in an argon glove box with a dew point below -70°C. <Cycle Characteristics and Resistance Characteristics of Coin Batteries> Each coin battery was manufactured and placed in a constant temperature bath at 25°C with an input current of 0.5 mA / cm. 2 Charge to the termination voltage of 4.3V, and maintain a constant potential of 4.3V until the charging current becomes 0.15mA / cm. 2 After that, the discharge current is 0.5mA / cm. 2Discharge to the termination voltage of 3.0V. Perform 100 charge-discharge cycles using the current-voltage constant method under these conditions. Compare and evaluate the discharge capacity and DC resistance after 100 cycles. The DC resistance is calculated by subtracting the voltage drop between the charging termination voltage and the voltage 3 seconds after the start of discharge, and dividing by the discharge current. Table 5 shows the ratio of discharge capacity to DC resistance for each embodiment and comparative example when Comparative Example 9 is set to 100. As can be seen from Table 5, the coin batteries using the non-aqueous electrolytes of the various embodiments containing phosphate esters that impart flame retardancy showed higher discharge capacity after 100 cycles and lower DC resistance compared to the comparative examples. This confirms the excellent practicality of the non-aqueous electrolytes of the various embodiments and the lithium-ion secondary batteries using them. (Evaluation of Coulombic Efficiency Characteristics) <Fabrication of Coin Cells> The non-aqueous electrolytes of Example 21 and Comparative Example 11 lacked oxidation resistance, making it difficult to use cathodes such as LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O In the case of electrodes subjected to high voltage, coin-type lithium-ion secondary batteries (coin batteries) as shown in Figure 1 were fabricated for these non-aqueous electrolytes as described below, and their electrochemical characteristics were evaluated. That is, the positive electrode uses copper foil (manufactured by NILACO Corporation) cut to a diameter of 11.3 mm, and the separator uses glass filter paper (GC-50, manufactured by ADNANTECH Toyo Corporation). The negative electrode uses lithium foil (manufactured by Honjo Metals Corporation) cut to a diameter of 13 mm. Furthermore, the positive electrode, separator, and negative electrode are sequentially laminated to form a laminate, which is then immersed in the non-aqueous electrolyte of Example 21 or Comparative Example 11, and the laminate is sealed to prepare coin batteries. The assembly of the coin batteries is carried out entirely in an argon glove box with a dew point below -70°C. <Coulomb Efficiency of Coin Cells> Each coin cell fabricated was placed in a constant temperature bath at 25°C with a charging current of 0.5 mA / cm². 2 After charging for 2 hours to allow lithium metal to deposit, discharge at a current of 0.5 mA / cm. 2 Discharge to a termination voltage of 1.0V to dissolve the metallic lithium. Perform 10 charge-discharge cycles using the current-voltage method under these conditions. Compare and evaluate the coulombic efficiency after 10 cycles. Table 6 shows the ratio of coulombic efficiency between Example 21 and Comparative Example 11. As can be seen from Table 6, LiPF6 is used as the electrolyte only. Comparative Example 11, using a non-aqueous electrolyte of type 6, showed a coulombic efficiency of 16% after 10 cycles. In contrast, the electrolyte containing LiNO3... 3 and LiPO 2F Example 21, using a non-aqueous electrolyte, showed a coulombic efficiency of 79%, demonstrating good charge-discharge efficiency (cycle characteristics) compared to Comparative Example 11. This confirms the excellent practicality of a non-aqueous electrolyte using a mixed solvent of DMSO and TEP, and the lithium-ion secondary battery using this non-aqueous electrolyte. 1: Positive electrode 2: Negative electrode 3: Insulator 4: Positive electrode container 5: Negative electrode container 6: Gasket 7: Spacer [Figure 1] is a schematic cross-sectional view showing a non-aqueous secondary battery according to one embodiment of the present invention. 1: Positive electrode 2: Negative electrode 3: Isolation sheet 4: Positive electrode container 5: Negative electrode container 6: Gasket 7: Spacer 8: Spring

Claims

1. A flame-retardant non-aqueous electrolyte comprising at least a non-aqueous solvent and an electrolyte dissolved in the aforementioned non-aqueous solvent, wherein the aforementioned non-aqueous solvent comprises at least one phosphate ester represented by the following chemical formulas (1) to (3), the aforementioned electrolyte comprises at least one difluorophosphate and nitrate, and other electrolytes besides the aforementioned difluorophosphate and nitrate, wherein the mole fraction of the aforementioned difluorophosphate and nitrate is 0.1 or more relative to the total mole count of the aforementioned electrolyte, and the content of the aforementioned phosphate ester is 20% by mass or more relative to the total mass of the aforementioned flame-retardant non-aqueous electrolyte. (In the formula, X1~X3 each independently represent a hydrocarbon group with 1~20 carbon atoms; a silane group with 1~20 carbon atoms; a hydrocarbon group with 1~20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond; or a silane group with 1~20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond; or X1~X3 are any of the aforementioned hydrocarbon groups with 1~20 carbon atoms; the aforementioned silane group with 1~20 carbon atoms; the aforementioned hydrocarbon group with 1~20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond; or the aforementioned silane group with 1~20 carbon atoms and having at least one of a halogen atom, a heteroatom, or an unsaturated bond, and any combination thereof is bonded together to form a cyclic structure, and Y1 and Y2 each independently represent a halogen atom).

2. The flame-retardant non-aqueous electrolyte of claim 1, wherein at least one of the aforementioned difluorophosphate and the aforementioned nitrate is an alkali metal salt.

3. The flame-retardant non-aqueous electrolyte of claim 2, wherein at least one of the aforementioned difluorophosphate and nitrate is a lithium salt.

4. The flame-retardant non-aqueous electrolyte as claimed in claim 1, wherein the aforementioned phosphate ester is trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, diethyl monofluorophosphate, diethyl monochlorophosphate, ethyl difluorophosphate, ethyl dichlorophosphate and diethyl phosphate (2-(2-(2-methoxyethoxy)ethoxy)ethyl) ester.

5. The flame-retardant non-aqueous electrolyte of claim 1, wherein the aforementioned electrolyte further comprises at least one other electrolyte having anions of BF4-, PF6-, N(CF3SO2)2- or N(SO2F)2-.

6. The flame-retardant non-aqueous electrolyte of claim 1, wherein the aforementioned non-aqueous solvent further comprises at least one selected from the group consisting of cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, lactones, chain esters, nitrile compounds, amides, uranium compounds, and uranium monoxides.

7. The flame-retardant non-aqueous electrolyte of claim 1, wherein the aforementioned non-aqueous solvent further comprises at least one of propyl carbonate, ethyl carbonate, γ-butyrolactone, dimethyl sulfoxide, and tetraethylene glycol dimethyl ether.

8. A secondary battery comprising at least a flame-retardant non-aqueous electrolyte as described in any one of claims 1 to 7, a positive electrode, and a negative electrode.

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