Electrolyte for non-aqueous sodium-ion battery, non-aqueous sodium-ion battery, and method for manufacturing same

Abstract

Provided are: an electrolyte for a non-aqueous sodium-ion battery, the electrolyte comprising (I) a fluorosulfate, (II) a Bronsted acid, (III) a sodium salt, and (IV) a non-aqueous organic solvent, wherein the content of (II) is 0.8-600 ppm by mass with respect to the total amount of the electrolyte for a non-aqueous sodium-ion battery; a non-aqueous sodium-ion battery using said electrolyte for a non-aqueous sodium-ion battery; and a method for manufacturing said non-aqueous sodium-ion battery.

Description

Electrolyte for non-aqueous sodium ion batteries, non-aqueous sodium ion battery, and method for manufacturing the same.

[0001] This disclosure relates to an electrolyte for non-aqueous sodium-ion batteries, a non-aqueous sodium-ion battery using the same, and a method for manufacturing the same.

[0002] In recent years, lithium-ion batteries have attracted attention as energy storage systems for small, high-energy-density applications such as information-related equipment and communication devices, i.e., personal computers, video cameras, digital still cameras, and mobile phones, as well as for large, power applications such as auxiliary power supplies for electric vehicles, hybrid vehicles, and fuel cell vehicles, and for power storage. On the other hand, lithium prices have soared, and the less expensive sodium-ion batteries are attracting attention as the next-generation secondary battery (Patent Document 1).

[0003] In non-aqueous sodium-ion batteries, various non-aqueous electrolyte additives have been investigated to improve performance such as cycle endurance, storage endurance, and input / output characteristics. Patent Document 1 shows that using a cyclic sulfate ester as an additive in a non-aqueous electrolyte containing an electrolyte such as sodium fluorosulfonate exhibits an effect of suppressing resistance increase.

[0004] Japanese Patent Application Publication No. 2019-46614

[0005] While non-aqueous sodium-ion batteries are already beginning to be put into practical use, challenges remain, such as durability during high-temperature storage (suppression of gas generation during high-temperature storage) and improvement of initial input / output characteristics when used in low-temperature environments. Furthermore, achieving a balance between these performance aspects is generally difficult. For example, improving durability by forming a film on the negative electrode using a non-aqueous electrolyte additive can lead to a decrease in input / output characteristics because the film becomes a resistive component.

[0006] Therefore, the object of this disclosure is to provide an electrolyte for non-aqueous sodium-ion batteries that exhibits excellent initial low-temperature power output characteristics and excellent suppression of gas generation during high-temperature storage when used in non-aqueous sodium-ion batteries, a non-aqueous sodium-ion battery using the same, and a method for manufacturing the same.

[0007] As a result of intensive studies in view of such problems, the inventors of the present invention have found that by containing fluorosulfate and a predetermined amount of Bronsted acid, a non-aqueous electrolyte excellent in both initial low-temperature output characteristics and suppression of gas generation amount during high-temperature storage can be obtained when used in a non-aqueous sodium ion battery.

[0008] That is, the present disclosure includes the following embodiments.

[0009] [1] An electrolyte for a non-aqueous sodium ion battery, comprising (I) fluorosulfate, (II) Bronsted acid, (III) sodium salt, and (IV) non-aqueous organic solvent, wherein the content of the component (II) is 0.8 mass ppm to 600 mass ppm with respect to the total amount of the electrolyte for a non-aqueous sodium ion battery.

[0010] [2] The electrolyte for a non-aqueous sodium ion battery according to [1], wherein the content of the component (II) is 3.0 mass ppm to 300 mass ppm with respect to the total amount of the electrolyte for a non-aqueous sodium ion battery. [3] The component (II) is at least one selected from the group consisting of HF, H ２ SO ４ , HSO ３ F, NaHSO ４ , and HPO ２ F ２ ; the electrolyte for a non-aqueous sodium ion battery according to [1] or [2]. [4] The electrolyte for a non-aqueous sodium ion battery according to any one of [1] to [3], wherein the content of the component (I) is 0.008 mass% to 7.5 mass% with respect to the total amount of the electrolyte for a non-aqueous sodium ion battery.

[0011] [5] The electrolyte for a non-aqueous sodium ion battery according to any one of [1] to [4], wherein the counter cation of the component (I) is lithium ion, sodium ion, potassium ion, tetraalkylammonium ion, tetraalkylphosphonium ion or ammonium ion having a spiro skeleton. [6] The component (III) is NaPF ６ , NaBF ４ , NaSbF ６ , NaAsF ６ , NaClO ４ , NaN(SO２ F) ２ NaAlO ２ NaAlCl ４ An electrolyte for a non-aqueous sodium ion battery according to any one of the items [1] to [5], wherein at least one selected from the group consisting of NaCl and NaI. [7] An electrolyte for a non-aqueous sodium ion battery according to any one of the items [1] to [6], wherein the concentration of (III) is 0.3 mol / L to 5.0 mol / L with respect to the total amount of the electrolyte for a non-aqueous sodium ion battery.

[0012] [8] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [7], wherein (IV) comprises at least one selected from the group consisting of cyclic esters, linear esters, cyclic ethers, linear ethers, sulfone compounds, sulfoxide compounds, nitrile compounds, and ionic liquids. [9] The electrolyte for a non-aqueous sodium-ion battery according to [8], wherein the cyclic ester comprises a cyclic carbonate.

[10] The electrolyte for a non-aqueous sodium-ion battery according to [9], wherein the cyclic carbonate comprises at least one selected from the group consisting of ethylene carbonate and propylene carbonate.

[0013]

[11] The electrolyte for a non-aqueous sodium-ion battery according to [8], wherein the chain-like ester comprises a chain-like carbonate.

[12] The electrolyte for a non-aqueous sodium-ion battery according to

[11] , wherein the chain-like carbonate comprises at least one selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0014]

[13] The electrolyte for a non-aqueous sodium-ion battery according to [8], wherein the cyclic ether comprises at least one selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, and trioxane.

[14] The electrolyte for a non-aqueous sodium-ion battery according to [8], wherein the chain ether comprises at least one selected from the group consisting of diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, 1,2-dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0015]

[15] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [7], wherein (IV) comprises at least one selected from the group consisting of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, tetrahydrofuran, 1,2-dimethoxyethane, acetonitrile, and propionitrile.

[0016]

[16] Furthermore, cyclohexylbenzene, cyclohexylfluorobenzene, biphenyl, 2-fluorobiphenyl, tert-butylbenzene, tert-amylbenzene, 2-fluorotoluene, fluorobenzene, difluoroanisole, vinylene carbonate, oligomers of vinylene carbonate (number average molecular weight in polystyrene terms of 170 to 5000), vinylethylene carbonate, divinylethylene carbonate, fluoroethylene carbonate, ethynylethylene carbonate, trans-difluoroethylene carbonate, methylpropargyl carbonate, ethylpropargyl carbonate, dipropargyl carbonate, dimethylvinylene carbonate, dimethyldicarbonate, bis(1,1,1,3,3,3-hexafluoro-1-propyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 1,6-diisocyanatohexa N, maleic anhydride, succinic anhydride, 1,4-dioxan-2,6-dione, glutaric anhydride, methanedisulfonic anhydride, 1,2-ethanedisulfonic anhydride, methanesulfonic anhydride, 2-sulfobenzoic anhydride, 1,3-propanedisulfonic anhydride, 1,3-propanesultone, 1,3-propensultone, 1,4-butanesultone, 2,4-butanesultone, 1,3,2-dioxathiolan-2,2-dioxide, 4-pro Pyr-1,3,2-dioxathiolan-2,2-dioxide, 1,3-dithiolan-1,1,3,3-tetraoxide, 1,3-dithian-1,1,3,3-tetraoxide, 1,2-oxathiolan-5-one-2,2-dioxide, methylene methane disulfate, dimethyl methane disulfate, trimethylene methane disulfate, methyl methanesulfonate, methanesulfonyl fluoride, ethensulfonyl fluoride, N,N'-Carbonylbis(N-methylsulfamoylfluoride), difluoro(picolinato)borate, phenyl difluorophosphate, trippropargyl phosphate, tetrafluoro(picolinato)phosphate, (ethoxy)pentafluorocyclotriphosphazene, succinonitrile, methyldifluorovinylsilane, methylfluorodivinylsilane, dimethyldivinylsilane, trivinylmethylsilane, trivinylfluorosilane, tetravinylsilane, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, 1,3-dimethyl-1,3-divinyl-1,3-di(1,1,1,3,3,3-Hexafluoroisopropyl)disiloxane, trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, monomethyl sulfate, monoethyl sulfate, bis(trifluoromethanesulfonyl)imide, bis(pentafluoroethanesulfonyl)imide, (trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide, (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide, (trifluoromethanesulfonyl)(fluorosulfonyl)imide, (pentafluoroethanesulfonyl)(fluorosulfonyl)imide, (difluorophosphoryl)(fluorosulfonyl)imide, (difluorophosphoryl)(trifluoromethanesulfonyl)imide, bis(difluorophosphoryl)imide, (fluorosulfonyl)(carbonyl) An electrolyte for a non-aqueous sodium-ion battery according to any one of the following: lithium ximide ximethanesulfonate, (fluorosulfonyl)(carbonyldi(2-propenyl)phosphoryl)imide salt, (carbonyldi(propargyl)phosphoryl)imide salt, monofluorophosphate, difluorophosphate, tetrafluoro(malonato) phosphate, tris(oxalato) phosphate, difluorobis(oxalato) phosphate, tetrafluorooxalato phosphate, bis(oxalato) borate, difluorooxalatoborate, difluoro(malonato) borate, tris(trifluoromethanesulfonyl)methide salt, tris(fluorosulfonyl)methide salt, acrylate, methacrylate, nitrate, nitrite, hexafluoroisopropanol, and trifluoroethanol.

[0017]

[17] The electrolyte for a non-aqueous sodium ion battery according to any one of [1] to

[16] , further comprising a difluorophosphate ester represented by the following general formula (1A).

[0018]

[0019] In general formula (1A), R is a hydrocarbon group having 1 to 15 carbon atoms, and any hydrogen atom of the hydrocarbon group may be substituted with a halogen atom.

[0020]

[18] A non-aqueous sodium-ion battery comprising at least a positive electrode, a negative electrode, and an electrolyte for a non-aqueous sodium-ion battery as described in any one of [1] to

[17] .

[19] A method for manufacturing a non-aqueous sodium-ion battery, comprising the step of injecting the electrolyte for a non-aqueous sodium-ion battery as described in any one of [1] to

[17] .

[0021] This disclosure provides an electrolyte for non-aqueous sodium-ion batteries that exhibits excellent initial low-temperature power output characteristics and excellent suppression of gas generation during high-temperature storage when used in non-aqueous sodium-ion batteries, a non-aqueous sodium-ion battery using the same, and a method for manufacturing the same.

[0022] In this specification, "~" is used to mean that the numbers before and after it are included as the lower and upper limits, respectively.

[0023] The following is a detailed description of this disclosure, but the description of the constituent elements described below is an example of an embodiment of this disclosure and is not limited to these specific contents.

[0024] [1. Electrolyte for Non-Aqueous Sodium Ion Battery] The electrolyte for a non-aqueous sodium ion battery according to the embodiment of the present disclosure comprises (I) a fluorosulfate, (II) a Brønsted acid, (III) a sodium salt, and (IV) a non-aqueous organic solvent, wherein the content of (II) is 0.8 ppm by mass to 600 ppm by mass with respect to the total amount of the electrolyte for the non-aqueous sodium ion battery.

[0025] The electrolyte for non-aqueous sodium-ion batteries according to this embodiment, with the above configuration, exhibits excellent initial low-temperature power output characteristics and excellent suppression of gas generation during high-temperature storage when used in a non-aqueous sodium-ion battery. Although the details of this mechanism are not clear, the inventors speculate as follows: The fluorosulfate contained in the electrolyte for non-aqueous sodium-ion batteries according to this embodiment forms a film with low resistance to sodium ion movement by adsorption or decomposition on the electrode surface. This reaction is thought to proceed in concert with the decomposition reaction of the solvent on the electrode surface. However, when Brønsted acid is present at a specific concentration, it is thought to catalytically reinforce or accelerate the film formation reaction of the fluorosulfate, forming a film richer in fluorosulfate, thereby simultaneously achieving improved initial low-temperature power output and improved gas characteristics during high-temperature storage tests.

[0026] The components of the electrolyte for the non-aqueous sodium-ion battery according to this embodiment will be described in detail below.

[0027] <(I) Fluorosulfates> The (I) fluorosulfates (also referred to as "(I)") contained in the electrolyte for non-aqueous sodium-ion batteries of this disclosure will be described below. Fluorosulfates are SO ３ F － It is an ionic salt having an anion represented by and a countercation. As for the countercation of the fluorosulfate, there are no particular restrictions on its type as long as it does not impair the performance of the electrolyte for the non-aqueous sodium ion battery and the non-aqueous sodium ion battery according to this embodiment, and various types can be selected.

[0028] Specific examples of countercations include metal cations such as lithium ions, sodium ions, potassium ions, rubidium ions, cesium ions, magnesium ions, calcium ions, barium ions, silver ions, copper ions, and iron ions, as well as onium cations such as tetraalkylammonium ions, tetraalkylphosphonium ions, imidazolium ions, and ammonium ions having a spiro skeleton. However, from the viewpoint of assisting ion conduction in non-aqueous sodium-ion batteries, lithium ions, sodium ions, potassium ions, tetraalkylammonium ions, tetraalkylphosphonium ions, or ammonium ions having a spiro skeleton are preferred, and lithium ions, sodium ions, tetraalkylammonium ions, or ammonium ions having a spiro skeleton are more preferred. The number of carbon atoms in the alkyl group of the tetraalkylammonium ion is preferably 1 to 6, and the number of carbon atoms in the alkyl group of the tetraalkylphosphonium ion is preferably 1 to 6. The four alkyl groups in the tetraalkylammonium ion may be the same or different from each other, and the four alkyl groups in the tetraalkylphosphonium ion may be the same or different from each other. As for the ammonium ion having a spiro skeleton, for example, 5-azoniaspiron[4.4]nonane is preferred.

[0029] Fluorosulfates are not particularly limited, but include NaSO ３ F, LiSO ３ F, TEMASO ３ F, SBPSO ３ F or TEASO ３ F is preferred, NaSO ３ F, LiSO ３ F, or TEASO ３ F is particularly preferred. Here, TEA represents tetraethylammonium, TEMA represents triethylmethylammonium, and SBP represents 5-azoniaspirononane.

[0030] The fluorosulfate content is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.008% by mass or more, more preferably 0.08% by mass or more, and even more preferably 0.8% by mass or more, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. Furthermore, although the fluorosulfate content is not particularly limited, it is preferably 11.5% by mass or less, more preferably 10.5% by mass or less, even more preferably 7.5% by mass or less, and particularly preferably 5.5% by mass or less, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. If it is 0.001% by mass or more, the initial low-temperature output characteristics can be improved and the amount of gas generated during high-temperature storage can be suppressed. Also, if it is 11.5% by mass or less, the film formed on the electrode will not become too thick, and this will not easily lead to an increase in resistance. One type of fluorosulfate may be used alone, or two or more types may be mixed in any combination and ratio according to the application. In one embodiment, the content of the fluorosulfate is preferably 0.008% to 11.5% by mass, more preferably 0.008% to 10.5% by mass, even more preferably 0.008% to 7.5% by mass, and particularly preferably 0.8% to 5.5% by mass, based on the total amount of electrolyte for the non-aqueous sodium-ion battery.

[0031] <(II) Brønsted Acids> The (II) Brønsted acids (also referred to as "(II)") contained in the electrolyte for non-aqueous sodium ion batteries of this disclosure will be described. The Brønsted acids are not particularly limited and specifically include HF, H ２ SO ４ HSO ３ F, NaHSO ４ HPO ２ F ２ These include, among others, HF, H ２ SO ４ HSO ３ F, and NaHSO ４ It is preferable that it be at least one selected from the group consisting of the following.

[0032] The Brønsted acid content is 0.8 ppm to 600 ppm by mass relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. Below 0.8 ppm by mass, it is difficult to obtain the effect of improving initial low-temperature power characteristics and suppressing gas generation during high-temperature storage by adding Brønsted acid. Above 600 ppm by mass, the reaction with the positive electrode active material surface (a reaction that irreversibly changes the positive electrode active material), which is a synergistic reaction between the film formation reaction and the positive electrode active material, becomes apparent, increasing the positive electrode resistance. In this case as well, it is difficult to obtain the effect of improving initial low-temperature power characteristics and suppressing gas generation during high-temperature storage.

[0033] The Brønsted acid content is 0.8 ppm by mass or more, preferably 1.0 ppm by mass or more, more preferably 3.0 ppm by mass or more, even more preferably 7.5 ppm by mass or more, and particularly preferably 12 ppm by mass or more, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. Furthermore, the Brønsted acid content is 600 ppm by mass or less, preferably 550 ppm by mass or less, more preferably 300 ppm by mass or less, even more preferably 150 ppm by mass or less, and particularly preferably 75 ppm by mass or less, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. The Brønsted acid content is preferably 1.0 ppm to 550 ppm by mass, and more preferably 3.0 ppm to 300 ppm by mass, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. Brønsted acid may be used alone, or two or more types may be mixed in any combination and ratio. Furthermore, when using two or more types, it is preferable that their combined concentrations fall within the range described above.

[0034] The concentration of Brønsted acid in the electrolyte for non-aqueous sodium-ion batteries can be determined using neutralization titration, for example, as follows:

[0035] After drying at 150°C for more than 24 hours, a 300 mL fluororesin beaker was cooled to around room temperature (25°C) under a dry nitrogen atmosphere with a dew point of -70°C or lower. 100 mL of acetone (Wako Pure Chemical Industries, ultra-dehydrated) and a few drops of bromophenol blue ethanol solution (Wako Pure Chemical Industries) were added to the beaker. 50.0 g of non-aqueous sodium ion battery electrolyte was then added, and neutralization titration was performed with a 0.002 N or 0.1 N triethylamine / acetone solution while stirring. (Using Wako Pure Chemical Industries' ultra-dehydrated acetone and Wako Pure Chemical Industries' special grade triethylamine, dehydrated to a moisture content of 100 ppm or less.) The endpoint was defined as the point when the color of the solution changed from yellow to purple. Let A be the volume of the triethylamine / acetone solution used (L), B be the concentration of the triethylamine / acetone solution used (N), and C be the molecular weight of Brønsted acid (g / mol). The concentration of Brønsted acid in the sample is calculated using the following formula: Brønsted acid concentration [mass ppm] = A × B × C × 1000 / 50.0 × 1000

[0036] If multiple types of Brønsted acids are present, after performing the neutralization titration described above, the amount of counteranions of the Brønsted acids is quantified by ion chromatography (DIONEX Corporation, ICS-6000 (column: Ion Pac AS20)), and the free acid concentration of each is calculated using the formula described above to determine the Brønsted acid concentration in the sample.

[0037] <(III) Sodium Salt> The (III) sodium salt (also referred to as "(III)") contained in the electrolyte for non-aqueous sodium-ion batteries of this disclosure will be described. The type of sodium salt of the solute is not particularly limited, and any sodium salt (excluding (I) and (II) above) can be used. Specifically, the sodium salt is NaPF ６ NaBF ４ NaSbF ６ NaAsF ６ NaClO ４ NaN(SO ２ F) ２ NaAlO ２ NaAlCl ４At least one selected from the group consisting of NaCl and NaI can be preferably listed.

[0038] In particular, considering the energy density, output characteristics, and lifespan of non-aqueous sodium ion batteries, NaPF ６ NaBF ４ and NaN(SO ２ F) ２ At least one selected from the group consisting of is preferable.

[0039] The concentration of sodium salt in the electrolyte for the non-aqueous sodium-ion battery according to this embodiment is not particularly limited, but is preferably 0.05 mol / L or more, more preferably 0.3 mol / L or more, even more preferably 0.8 mol / L or more, and also preferably 5.0 mol / L or less, more preferably 2.0 mol / L or less, and even more preferably 1.5 mol / L or less, relative to the total amount of the electrolyte for the non-aqueous sodium-ion battery. Setting the concentration to 0.05 mol / L or more makes it easier to suppress the decrease in the cycle characteristics of the non-aqueous sodium-ion battery due to a decrease in ionic conductivity. On the other hand, setting the concentration to 5.0 mol / L or less makes it easier to suppress the increase in viscosity of the electrolyte for the non-aqueous sodium-ion battery and the resulting decrease in battery characteristics due to a decrease in ionic conductivity. Component (III) may be used alone, or two or more may be mixed in any combination and ratio according to the application. In one embodiment, the concentration of component (III) is preferably 0.3 mol / L to 5.0 mol / L, more preferably 0.4 mol / L to 3.0 mol / L, even more preferably 0.5 mol / L to 2.0 mol / L, and particularly preferably 0.8 mol / L to 1.5 mol / L, relative to the total amount of electrolyte for the non-aqueous sodium ion battery. When two or more types of (III) are used, it is preferable that their total concentration is within the above range.

[0040] Although the (III) sodium salt may overlap with component (II), if the content is above a predetermined amount (the concentration of (III) sodium salt in the electrolyte for non-aqueous sodium ion batteries is 0.3 mol / L or more relative to the total amount of the electrolyte for non-aqueous sodium ion batteries), it will function as the main electrolyte ((III) sodium salt).

[0041] The temperature at which (III) is dissolved in (IV) a non-aqueous organic solvent is not particularly limited, but may be -20 to 80°C or 0 to 60°C.

[0042] <(IV) Non-Aqueous Organic Solvents> The (IV) non-aqueous organic solvent (also referred to as "(IV)") contained in the electrolyte for non-aqueous sodium-ion batteries of this disclosure will be described below. The type of (IV) non-aqueous organic solvent is not particularly limited, and any non-aqueous organic solvent can be used. Such non-aqueous organic solvents preferably contain at least one selected from the group consisting of cyclic esters, linear esters, cyclic ethers, linear ethers, sulfone compounds, sulfoxide compounds, amide compounds, nitrile compounds, and ionic liquids, and more preferably contain at least one selected from the group consisting of cyclic esters, linear esters, cyclic ethers, linear ethers, sulfone compounds, sulfoxide compounds, nitrile compounds, and ionic liquids. Note that cyclic carbonates are a sub-concept of cyclic esters, and linear carbonates are a sub-concept of linear esters. Specific examples of (IV) non-aqueous organic solvents include the following non-aqueous organic solvents. Examples of cyclic esters include cyclic carbonates such as propylene carbonate (hereinafter sometimes referred to as "PC"), ethylene carbonate (hereinafter sometimes referred to as "EC"), and butylene carbonate, as well as γ-butyrolactone and γ-valerolactone.Chain-like esters include diethyl carbonate (hereinafter sometimes referred to as "DEC"), dimethyl carbonate (hereinafter sometimes referred to as "DMC"), ethyl methyl carbonate (hereinafter sometimes referred to as "EMC"), methyl propyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, 2,2,2-trifluoroethyl ethyl carbonate, 2,2,2-trifluoroethyl propyl carbonate, 1,1,1,3,3,3-hexafluoro-1-propyl methyl carbonate, 1, Examples of cyclic ethers include linear carbonates such as 1,1,3,3,3-hexafluoro-1-propylethyl carbonate and 1,1,1,3,3,3-hexafluoro-1-propylpropyl carbonate, as well as methyl acetate (hereinafter sometimes referred to as "MA"), ethyl acetate (hereinafter sometimes referred to as "EA"), methyl propionate (hereinafter sometimes referred to as "MP"), ethyl propionate (hereinafter sometimes referred to as "EP"), propyl propionate (hereinafter sometimes referred to as "PP"), methyl 2-fluoropropionate, and ethyl 2-fluoropropionate. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, and trioxane. Examples of linear ethers include diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, 1,2-dimethoxyethane (hereinafter sometimes referred to as "DME"), diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Other examples include sulfone compounds and sulfoxide compounds such as dimethyl sulfoxide and sulfolane, nitrile compounds such as N,N-dimethylformamide, acetonitrile (hereinafter sometimes referred to as "AN"), and propionitrile. Ionic liquids can also be mentioned.

[0043] The cyclic ester may contain a cyclic carbonate, and the cyclic carbonate may contain at least one selected from the group consisting of ethylene carbonate and propylene carbonate.

[0044] The linear ester may contain a linear carbonate, and the linear carbonate may contain at least one selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0045] The cyclic ether may include at least one selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, and trioxane.

[0046] The chain-like ether may include at least one selected from the group consisting of diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, 1,2-dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0047] The electrolyte for non-aqueous sodium-ion batteries of this disclosure may use one compound alone as (IV), or two or more compounds may be mixed in any combination and ratio according to the application. Among these, it is particularly preferable to include at least one selected from the group consisting of PC, EC, DEC, DMC, and EMC, from the viewpoint of electrochemical stability with respect to oxidation and reduction and chemical stability related to heat and reaction with the solute. In another preferred embodiment, the electrolyte for non-aqueous sodium-ion batteries of this disclosure is preferably (IV) to include at least one selected from the group consisting of MA, EA, MP, EP, PP, tetrahydrofuran, DME, AN, and propionitrile, from the viewpoint of excellent initial low-temperature power characteristics. (IV) is preferably at least one selected from the group consisting of MA, EA, MP, EP, PP, tetrahydrofuran, DME, AN, and propionitrile.

[0048] Furthermore, it is preferable to include, for example, one or more cyclic carbonates with high dielectric constants and one or more chain carbonates or chain esters with low liquid viscosity as the non-aqueous organic solvent, because this increases the ionic conductivity of the electrolyte. Specifically, the following combinations are more preferable. (1) Combination of EC and EMC, (2) Combination of EC and DEC, (3) Combination of EC, DMC and EMC, (4) Combination of EC, DEC and EMC, (5) Combination of EC, EMC and EP, (6) Combination of PC and DEC, (7) Combination of PC and EMC, (8) Combination of PC and EP, (9) Combination of PC, DMC and EMC, (10) Combination of PC, DEC and EMC, (11) Combination of PC, DEC and EP, (12) Combination of PC, EC and EMC, (13) Combination of PC, EC, DMC and EMC, (14) Combination of PC, EC, DEC and EMC, (15) Combination of PC, EC, EMC and EP

[0049] The concentration of the non-aqueous organic solvent in this disclosure is not particularly limited as long as it functions as a non-aqueous organic solvent, but it may be, for example, 40 to 99% by mass, preferably 50 to 95% by mass, and particularly preferably 70 to 93% by mass, based on the total amount (100% by mass) of the electrolyte for the non-aqueous sodium-ion battery.

[0050] The content of cyclic carbonate is not particularly limited and is arbitrary as long as it does not significantly impair the effects of this disclosure. However, when using one type alone, the content may be 3% by volume or more, and more preferably 5% by volume or more, in 100% by volume of non-aqueous organic solvent. By setting it within this range, a decrease in electrical conductivity due to a decrease in the dielectric constant of the electrolyte for non-aqueous sodium-ion batteries can be avoided, and it is easier to achieve good high-current discharge characteristics, stability to the negative electrode, and cycle characteristics of the non-aqueous sodium-ion battery. Alternatively, it may be 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting it within this range, the viscosity of the electrolyte for non-aqueous sodium-ion batteries can be set within an appropriate range, a decrease in ionic conductivity can be suppressed, and consequently it is easier to achieve good load characteristics of the non-aqueous sodium-ion battery.

[0051] Furthermore, cyclic carbonates can be used in any combination of two or more types. One preferred combination is ethylene carbonate and propylene carbonate. In this case, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99:1 to 40:60, and particularly preferably 95:5 to 50:50. Moreover, the amount of propylene carbonate in the total non-aqueous organic solvent is not particularly limited and is arbitrary as long as it does not significantly impair the effects of this disclosure, but it may be 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, also 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less. Including propylene carbonate within this range is preferable because, for example, when combining ethylene carbonate with dialkyl carbonates, the low-temperature characteristics are further improved while maintaining the characteristics of the combination of ethylene carbonate and dialkyl carbonates.

[0052] The chain-like ester may be used alone, or two or more may be used in any combination and ratio. The content of the chain-like ester is not particularly limited, but may be 15% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, or 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less, based on 100% by volume of the non-aqueous organic solvent. By setting the content of the chain-like ester within the above range, the viscosity of the electrolyte for non-aqueous sodium-ion batteries can be set to an appropriate range, the decrease in ionic conductivity can be suppressed, and consequently, the input / output characteristics and charge / discharge rate characteristics of the non-aqueous sodium-ion battery can be set to a favorable range. Furthermore, a decrease in electrical conductivity due to a decrease in the dielectric constant of the electrolyte for non-aqueous sodium-ion batteries can be avoided, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous sodium-ion battery can be set to a favorable range. In addition, by combining a specific chain-like ester with ethylene carbonate in a specific content, the battery performance can be significantly improved.

[0053] For example, when dimethyl carbonate, ethyl methyl carbonate, or a mixture of dimethyl carbonate and ethyl methyl carbonate is selected as a specific chain ester, the content of ethylene carbonate is not particularly limited and is arbitrary as long as it does not significantly impair the effects of this disclosure, but it may be 5% by volume or more, preferably 10% by volume or more, and may also be 45% by volume or less, and preferably 40% by volume or less. The content of dimethyl carbonate may be 20% by volume or more, preferably 30% by volume or more, and may also be 50% by volume or less, and preferably 45% by volume or less. The content of ethyl methyl carbonate may be 20% by volume or more, preferably 30% by volume or more, and may also be 50% by volume or less, and preferably 45% by volume or less. By setting the content within the above ranges, the low-temperature deposition temperature of the electrolyte is reduced, while the viscosity of the electrolyte for non-aqueous sodium ion batteries is also reduced, improving ionic conductivity and making it easier to obtain high input and output even at low temperatures.

[0054] The content of the linear ether is not particularly limited and is arbitrary as long as it does not significantly impair the effects of this disclosure. However, it may be 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more, or 40% by volume or less, preferably 30% by volume or less, and more preferably 25% by volume or less, per 100% by volume of non-aqueous organic solvent. If the content of the linear ether is within the above range, it is easy to ensure the effect of improved ionic conductivity due to improved sodium ion dissociation of the linear ether and reduced viscosity. In addition, since the oxidative decomposition of the linear ether can be suppressed to a certain amount or less, it is easier to set the input / output characteristics and charge / discharge rate characteristics within an appropriate range.

[0055] The content of the sulfone compound is not particularly limited and is arbitrary as long as it does not significantly impair the effects of this disclosure. However, it may be 0.3% by volume or more, preferably 0.5% by volume or more, more preferably 1% by volume or more, or 40% by volume or less, preferably 35% by volume or less, and more preferably 30% by volume or less, based on 100% by volume of the non-aqueous organic solvent. If the content of the sulfone compound is within the above range, it is easier to obtain effects that improve durability such as cycle characteristics and storage characteristics, and it is also possible to set the viscosity of the electrolyte for the non-aqueous sodium-ion battery within an appropriate range, avoid a decrease in electrical conductivity, and make it easier to set the input / output characteristics and charge / discharge rate characteristics of the non-aqueous sodium-ion battery within an appropriate range.

[0056] The content of at least one selected from the group consisting of MA, EA, MP, EP, PP, tetrahydrofuran, DME, AN, and propionitrile is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present disclosure. It may be 1% by volume or more, preferably 3% by volume or more, more preferably 5% by volume or more, 80% by volume or less, preferably 70% by volume or less, and more preferably 60% by volume or less, in 100% by volume of the nonaqueous organic solvent. By setting the content within the above range, it is possible to avoid a decrease in durability such as cycle characteristics and storage characteristics, while also lowering the viscosity of the electrolyte for nonaqueous sodium-ion batteries to improve ionic conductivity and make it easier to obtain high input / output at low temperatures.

[0057] <Regarding other components that may be included> The electrolyte for non-aqueous sodium-ion batteries of this disclosure is composed of the above components as basic components, but the electrolyte for non-aqueous sodium-ion batteries of this disclosure may contain the components described below (hereinafter also referred to as "other components that may be included" or "other components") in any combination and ratio, as long as the gist of this disclosure is not impaired. As other components, for example, other additives that are commonly used in this art may be added in any ratio.

[0058] Other components include aromatic compounds such as cyclohexylbenzene, cyclohexylfluorobenzene, biphenyl, 2-fluorobiphenyl, tert-butylbenzene, tert-amylbenzene, 2-fluorotoluene, fluorobenzene, and difluoroanisole. Carbonate compounds such as vinylene carbonate (hereinafter sometimes referred to as "VC"), vinylene carbonate oligomers (number average molecular weight in polystyrene terms of 170 to 5000), vinylethylene carbonate, divinylethylene carbonate, fluoroethylene carbonate (hereinafter sometimes referred to as "FEC"), ethynylethylene carbonate, trans-difluoroethylene carbonate, methylpropargyl carbonate, ethylpropargyl carbonate, dipropargyl carbonate, dimethylvinylene carbonate, dimethyl dicarbonate, bis(1,1,1,3,3,3-hexafluoro-1-propyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, and isocyanate compounds such as 1,6-diisocyanatohexane. Organic acid anhydrides such as maleic anhydride, succinic anhydride, 1,4-dioxan-2,6-dione, glutaric acid anhydride, methanedisulfonic acid anhydride, 1,2-ethanedisulfonic acid anhydride, methanesulfonic acid anhydride, 2-sulfobenzoic acid anhydride, 1,3-propanedisulfonic acid anhydride, Sulfonic acid ester compounds and sulfonyl compounds such as 1,3-propanesultone, 1,3-propensultone, 1,4-butanesultone, 2,4-butanesultone, 1,3,2-dioxathiolan-2,2-dioxide, 4-propyl-1,3,2-dioxathiolan-2,2-dioxide, 1,3-dithiolan-1,1,3,3-tetraoxide, 1,3-dithian-1,1,3,3-tetraoxide, 1,2-oxathiolan-5-one-2,2-dioxide, methylene methane disulfonate, dimethyl methane disulfonate, trimethylene methane disulfonate, methyl methanesulfonate, methanesulfonyl fluoride, ethensulfonyl fluoride, N,N'-carbonylbis(N-methylsulfamoyl fluoride), borate ester compounds such as difluoro(picolinato)borate,Phosphate ester compounds such as phenyl difluorophosphate, trippropargyl phosphate, and tetrafluoro(picolinato) phosphate; phosphazene compounds such as (ethoxy)pentafluorocyclotriphosphazene; nitrile compounds such as succinonitrile; silane compounds such as methyldifluorovinylsilane, methylfluorodivinylsilane, dimethyldivinylsilane, trivinylmethylsilane, trivinylfluorosilane, tetravinylsilane, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate; siloxane compounds such as 1,3-dimethyl-1,3-divinyl-1,3-di(1,1,1,3,3,3-hexafluoroisopropyl)disiloxane; sulfonates such as trifluoromethanesulfonate, pentafluoroethanesulfonate, and nonafluorobutanesulfonate (preferably trifluoromethanesulfonate); monoalkyl sulfates such as monomethyl sulfate and monoethyl sulfate. Bis(trifluoromethanesulfonyl)imide salt, bis(pentafluoroethanesulfonyl)imide salt, (trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide salt, (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide salt, (trifluoromethanesulfonyl)(fluorosulfonyl)imide salt, (pentafluoroethanesulfonyl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(trifluoromethanesulfonyl)imide salt, bis(difluorophosphoryl)imide salt, (fluorosulfonyl)(cal Imide salts such as lithium vonyloxymethanesulfonate imide salt, (fluorosulfonyl)(carbonyldi(2-propenyl)phosphoryl)imide salt, (carbonyldi(propargyl)phosphoryl)imide salt (preferably bis(trifluoromethanesulfonyl)imide salt, (trifluoromethanesulfonyl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(trifluoromethanesulfonyl)imide salt, bis(difluorophosphoryl)imide salt), or imide compounds in which a hydrogen atom is bonded to a nitrogen atom instead of a cation in the above imide salts,Examples include phosphates such as monofluorophosphates, difluorophosphates, tetrafluoro(malonato)phosphates, tris(oxalato)phosphates, difluorobis(oxalato)phosphates, and tetrafluorooxalatophosphates; borates such as bis(oxalato)borates, difluorooxalatoborates, and difluoro(malonato)borates; methide salts such as tris(trifluoromethanesulfonyl)methide salts and tris(fluorosulfonyl)methide salts; carboxylates such as acrylates and methacrylates; inorganic salts such as nitrates and nitrites; and fluorine-containing alcohols such as hexafluoroisopropanol and trifluoroethanol. The cations in the above salts may be alkali metal ions, alkaline earth metal ions, or quaternary ammonium compounds.

[0059] Furthermore, the electrolyte for non-aqueous sodium-ion batteries of this disclosure may further contain the following compounds in order to improve the cycle capacity retention rate and gas generation during cycle testing.

[0060]

[0061] The electrolyte for non-aqueous sodium-ion batteries of this disclosure further includes cyclohexylbenzene, cyclohexylfluorobenzene, biphenyl, 2-fluorobiphenyl, tert-butylbenzene, tert-amylbenzene, 2-fluorotoluene, fluorobenzene, difluoroanisole, vinylene carbonate, oligomers of vinylene carbonate (number average molecular weight in polystyrene terms of 170 to 5000), vinylethylene carbonate, divinylethylene carbonate, fluoroethylene carbonate, ethynylethylene carbonate, trans-difluoroethylene carbonate, methylpropargyl carbonate, ethylpropargyl carbonate, dipropargyl carbonate, dimethylvinylene carbonate, dimethyldicarbonate, bis(1,1,1,3,3,3-hexafluoro-1-propyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 1,6 - Diisocyanatohexane, maleic anhydride, succinic anhydride, 1,4-dioxane-2,6-dione, glutaric anhydride, methanedisulfonic anhydride, 1,2-ethanedisulfonic anhydride, methanesulfonic anhydride, 2-sulfobenzoic anhydride, 1,3-propanedisulfonic anhydride, 1,3-propanesultone, 1,3-propensultone, 1,4-butanesultone, 2,4-butanesultone, 1,3,2-dioxathiolan-2,2-dioxy D, 4-propyl-1,3,2-dioxathiolan-2,2-dioxide, 1,3-dithiolan-1,1,3,3-tetraoxide, 1,3-dithian-1,1,3,3-tetraoxide, 1,2-oxathiolan-5-one-2,2-dioxide, methylene methane disulfate, dimethyl methane disulfate, trimethylene methane disulfate, methyl methanesulfonate, methanesulfonyl fluoride, ethenesulfonyl fluoride, N,N'-Carbonylbis(N-methylsulfamoylfluoride), difluoro(picolinato)borate, phenyl difluorophosphate, trippropargyl phosphate, tetrafluoro(picolinato)phosphate, (ethoxy)pentafluorocyclotriphosphazene, succinonitrile, methyldifluorovinylsilane, methylfluorodivinylsilane, dimethyldivinylsilane, trivinylmethylsilane, trivinylfluorosilane, tetravinylsilane, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, 1,3-di Methyl-1,3-divinyl-1,3-di(1,1,1,3,3,3-hexafluoroisopropyl)disiloxane, trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, monomethyl sulfate, monoethyl sulfate, bis(trifluoromethanesulfonyl)imide, bis(pentafluoroethanesulfonyl)imide, (trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide, (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide, (trifluorometh (Fluorosulfonyl) (fluorosulfonyl)imide salt, (pentafluoroethanesulfonyl) (fluorosulfonyl)imide salt, (difluorophosphoryl) (fluorosulfonyl)imide salt, (difluorophosphoryl) (trifluoromethanesulfonyl)imide salt, bis(difluorophosphoryl)imide salt, (fluorosulfonyl) (carbonyloxymethanesulfonate lithium)imide, (fluorosulfonyl) (carbonyldi(2-propenyl)phosphoryl)imide salt, (carbonyldi(propargyl)phosphoryl)imide salt, monofluorophosphate, dif It is preferable to contain at least one selected from the group consisting of ruorophosphate, tetrafluoro(malonato)phosphate, tris(oxalato)phosphate, difluorobis(oxalato)phosphate, tetrafluorooxalatophosphate, bis(oxalato)borate, difluorooxalatoborate, difluoro(malonato)borate, tris(trifluoromethanesulfonyl)methide, tris(fluorosulfonyl)methide, acrylate, methacrylate, nitrate, nitrite, hexafluoroisopropanol, and trifluoroethanol.

[0062] Furthermore, the electrolyte for non-aqueous sodium-ion batteries of this disclosure preferably further contains a difluorophosphate ester represented by the following general formula (1A).

[0063]

[0064] In general formula (1A), R is a hydrocarbon group having 1 to 15 carbon atoms, and any hydrogen atom of the hydrocarbon group may be substituted with a halogen atom.

[0065] The hydrocarbon group having 1 to 15 carbon atoms represented by R may be linear, branched, or cyclic, and may have multiple bonds. It may also be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. Specifically, examples include alkyl groups having 1 to 15 carbon atoms, alkenyl groups having 2 to 15 carbon atoms, alkynyl groups having 2 to 15 carbon atoms, cycloalkyl groups having 3 to 15 carbon atoms, aryl groups having 6 to 15 carbon atoms, and aralkyl groups having 7 to 15 carbon atoms, with alkyl groups having 1 to 15 carbon atoms or aryl groups having 6 to 15 carbon atoms being preferred.

[0066] Examples of C1-C15 alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl, and n-dodecyl groups, with C1-C10 alkyl groups being preferred, and methyl, ethyl, n-propyl, or i-propyl groups being preferred. Examples of C6-C15 aryl groups include phenyl, naphthyl, and anthryl groups, with phenyl groups being preferred.

[0067] Furthermore, any hydrogen atom in the hydrocarbon group represented by R may be substituted with a halogen atom. Examples of halogen atoms include fluorine, chlorine, bromine, or iodine atoms, with fluorine being preferred.

[0068] R is preferably an unsubstituted C1-C15 alkyl group or an unsubstituted C6-C15 aryl group, and more preferably an unsubstituted C1-C10 alkyl group or an unsubstituted phenyl group.

[0069] The following are specific examples of difluorophosphate esters represented by general formula (1A), but this disclosure is not limited to these.

[0070]

[0071] The inclusion of the above-mentioned difluorophosphate ester in the electrolyte for non-aqueous sodium-ion batteries of this disclosure is preferable because it is excellent in suppressing gas generation during high-temperature storage.

[0072] The content of difluorophosphate ester is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. Furthermore, although the content of difluorophosphate ester is not particularly limited, it is preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. If it is 0.001% by mass or more, the amount of gas generated during high-temperature storage can be suppressed. Also, if it is 7% by mass or less, the film formed on the electrode will not become too thick, and this will not lead to an increase in resistance. Difluorophosphate ester may be used alone, or two or more types may be mixed in any combination and ratio according to the application. In one embodiment, the content of difluorophosphate ester is preferably 0.001% to 7% by mass, more preferably 0.01% to 5% by mass, and even more preferably 0.1% to 3% by mass, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries.

[0073] By including the above-mentioned other components in the electrolyte for non-aqueous sodium-ion batteries of this disclosure, at least one of the following effects may be enhanced: overcharge prevention effect, negative electrode film formation effect, and positive electrode protection effect.

[0074] Furthermore, it is possible to use electrolytes for non-aqueous sodium-ion batteries by pseudo-solidifying them with gelling agents or crosslinking polymers. Examples of such polymers include polymers having polyethylene oxide as the main chain or side chains, homopolymers or copolymers of polyvinylidene fluoride, methacrylate polymers, and polyacrylonitrile.

[0075] If the electrolyte for non-aqueous sodium-ion batteries of this disclosure contains other components, the content of these other components may be 0.01% by mass or more and 10% by mass or less based on the total amount of the electrolyte for non-aqueous sodium-ion batteries. Of the above other components, the content of fluoroethylene carbonate may be 0.01% by mass or more and 55% by mass or less based on the total amount of the electrolyte for non-aqueous sodium-ion batteries.

[0076] Furthermore, the content of bis(trifluoromethanesulfonyl)imide salts, trifluoromethanesulfonates, and nonafluorobutanesulfonates relative to the total amount of electrolyte for non-aqueous sodium ion batteries may be 0.01% by mass or more and 20% by mass or less.

[0077] Furthermore, the content of bis(1,1,1,3,3,3-hexafluoro-1-propyl) carbonate and bis(2,2,2-trifluoroethyl) carbonate relative to the total amount of electrolyte for non-aqueous sodium-ion batteries may be 0.1% by mass or more and 70% by mass or less.

[0078] Furthermore, if the other components mentioned above are ionic salts, it is more preferable that their cations be sodium ions.

[0079] The electrolyte for non-aqueous sodium-ion batteries of this disclosure may use a total of four or more alkali metal salts by using multiple types of the above (III) sodium salt and salt compounds of the above other components, depending on the required characteristics. Alternatively, the total of the above alkali metal salts may be five or more.

[0080] The electrolyte for non-aqueous sodium-ion batteries of this disclosure is suitably used in non-aqueous sodium-ion batteries (preferably non-aqueous sodium-ion secondary batteries).

[0081] [2. Non-aqueous sodium-ion battery] The non-aqueous sodium-ion battery of this disclosure comprises at least a positive electrode, a negative electrode, and the electrolyte for the non-aqueous sodium-ion battery of this disclosure described above. It may also include a separator, an outer casing, etc. Alternatively, a solid electrolyte may be used as a medium for impregnating the electrolyte for the non-aqueous sodium-ion battery instead of a separator. Preferably, the non-aqueous sodium-ion battery of this disclosure comprises at least a positive electrode, a negative electrode, a separator, and the electrolyte for the non-aqueous sodium-ion battery of this disclosure. Preferably, the non-aqueous sodium-ion battery of this disclosure is a non-aqueous sodium-ion secondary battery.

[0082] [Negative electrode] The negative electrode is not particularly limited, but a material that allows sodium ions to be reversibly inserted into and removed from may be used.

[0083] [Negative Electrode Active Material] As the negative electrode active material constituting the negative electrode, sodium metal, alloys of sodium metal and other metals such as tin, intermetallic compounds of sodium metal and other metals, various carbon materials including hard carbon, metal oxides such as titanium oxide, metal nitrides, tin (elemental), tin compounds, activated carbon, conductive polymers, etc. may also be used. In addition to these, phosphorus (elemental) such as red phosphorus and black phosphorus, phosphorus compounds such as Co-P, Cu-P, Sn-P, Ge-P, and Mo-P, antimony (elemental), antimony compounds such as Sb / C and Bi-Sb, etc. may also be used. These negative electrode active materials may be used individually or in combination of two or more types.

[0084] [Negative Electrode Current Collector] The negative electrode has a negative electrode current collector. For example, copper, stainless steel, nickel, titanium, or alloys thereof can be used as the negative electrode current collector. In addition, aluminum or its alloys can be used in sodium-ion batteries.

[0085] [Negative Electrode Active Material Layer] The negative electrode is formed by creating a negative electrode active material layer on at least one surface of the negative electrode current collector. The negative electrode active material layer is composed of, for example, the aforementioned negative electrode active material, a binder, and a conductive agent as needed. Examples of binders include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, styrene-butadiene rubber (hereinafter also referred to as "SBR"), carboxymethylcellulose, methylcellulose, cellulose phthalate acetate, hydroxypropylmethylcellulose, polyvinyl alcohol, and polyimide. Examples of conductive agents include acetylene black, Ketjen black, furnace black, carbon fiber, graphite, fluorinated graphite, and other carbon materials.

[0086] [Positive electrode] The positive electrode is not particularly limited, but a material that allows sodium ions to be reversibly inserted into and removed may be used.

[0087] [Positive electrode active material] As a positive electrode material (positive electrode active material), NaCrO ２ NaFe ０．５ Co ０．５ O ２ NaFe ０．４ Mn ０．３ Ni ０．３ O ２ NaFe １／３ Mn １／３ Ni １／３ O ２ NaNi ０．５ Ti ０．３ Mn ０．２ O ２ NaNi １／３ Ti １／３ Mn １／３ O ２ NaNi ０．３３ Ti ０．３３ Mn ０．１６ Mg ０．１７ O ２ Na ２／３ Ni １／３ Ti １／６ Mn １／２ O ２ Na ２／３ Ni １／３ Mn ２／３ O２ Sodium-containing transition metal composite oxides such as, those in which transition metals such as Co, Mn, Ni, etc. of these sodium-containing transition metal composite oxides are mixed in plural, those in which a part of the transition metals of these sodium-containing transition metal composite oxides are replaced with metals other than other transition metals, NaFePO ４ , NaVPO ４ F, Na ３ V ２ (PO ４ ) ３ , Na ２ Fe ２ (SO ４ ) ３ and other polyanion-type compounds, sodium salts of Prussian blue analogs represented by the composition formula Na β M ００２ γ [Fe(CN ６ ) δ (M ００２ = Cr, Mn, Fe, Co, Ni, Cu or Zn, 0 ≦ β ≦ 2, 0.5 ≦ γ ≦ 1.5, 0.5 ≦ δ ≦ 1.5), TiO ２ , V ２ O ５ , MoO ３ and other oxides, TiS ２ , FeS, MoS ２ and other sulfides, or conductive polymers such as polyacetylene, polyphenylene, polyaniline, and polypyrrole, activated carbon, polymers that generate radicals, carbon materials, etc. may also be used.

[0088] [Positive electrode current collector] The positive electrode has a positive electrode current collector. As the positive electrode current collector, for example, aluminum, stainless steel, nickel, titanium, or alloys thereof can be used.

[0089] [Positive Electrode Active Material Layer] The positive electrode is formed by creating a positive electrode active material layer on at least one surface of the positive electrode current collector. The positive electrode active material layer is composed of, for example, the positive electrode active material described above, a binder, and a conductive agent as needed. The binder is the same as described in [Negative Electrode Active Material Layer]. As the conductive agent, carbon materials such as acetylene black, Ketjen black, furnace black, carbon fiber, graphite (granular graphite or flake graphite), and fluorinated graphite can be used. In the positive electrode, it is preferable to use acetylene black or Ketjen black with low crystallinity.

[0090] [Method for manufacturing electrodes (positive and negative electrodes)] Electrodes can be obtained, for example, by dispersing and kneading an active material, a binder, and optionally a conductive agent in predetermined proportions in a solvent such as N-methyl-2-pyrrolidone (hereinafter sometimes referred to as "NMP") or water, applying the resulting paste to a current collector, and drying it to form an active material layer. It is preferable to compress the obtained electrodes using a method such as a roll press to adjust them to an electrode of appropriate density.

[0091] [Separator] The non-aqueous sodium-ion battery of this disclosure may be equipped with a separator. As a separator to prevent contact between the positive electrode and the negative electrode, for example, nonwoven fabrics or porous sheets made of polyolefins such as polypropylene and polyethylene, cellulose, paper, glass fiber, etc. are used. These films are preferably microporous so that the electrolyte can permeate and ions can easily pass through. As a polyolefin separator, for example, a microporous polymer film such as a porous polyolefin film is used, which electrically insulates the positive electrode and the negative electrode and allows sodium ions to pass through. Specific examples of porous polyolefin films include, for example, a porous polyethylene film alone, or a porous polyethylene film and a porous polypropylene film layered together to form a multilayer film. Also, a composite film of a porous polyethylene film and a polypropylene film is used. The electrolyte for the non-aqueous sodium-ion battery of this disclosure may be impregnated into the above separator and held therein. There are no particular restrictions on the impregnation method, and it may be carried out by known methods. Specifically, impregnation can be achieved by pouring electrolyte into a battery that consists of a positive electrode, a separator, and a negative electrode.

[0092] [Outer casing] Suitable outer casings for the non-aqueous sodium-ion battery of this disclosure include, for example, coin-type, cylindrical, or rectangular metal cans, as well as laminated outer casings. Suitable metal can materials include, for example, nickel-plated steel, stainless steel, nickel-plated stainless steel, aluminum or its alloys, nickel, titanium, etc. Suitable laminated outer casings include, for example, aluminum laminate film, SUS laminate film, silica-coated polypropylene, polyethylene laminate film, etc.

[0093] The configuration of the non-aqueous sodium-ion battery according to this embodiment is not particularly limited, but for example, it can be configured such that electrode elements with a positive electrode and a negative electrode arranged opposite each other, and an electrolyte for the non-aqueous sodium-ion battery are enclosed in an outer casing. The shape of the non-aqueous sodium-ion battery is not particularly limited, but an electrochemical device in the shape of a coin, cylinder, prismatic, or aluminum laminate sheet can be assembled from the above elements.

[0094] [3. Method for Manufacturing a Non-Aqueous Sodium Ion Battery] The method for manufacturing a non-aqueous sodium ion battery according to this disclosure comprises a step of injecting the electrolyte for the non-aqueous sodium ion battery according to this disclosure. There are no particular restrictions on the method of injection, and conventional methods can be used. For example, vacuum injection is one example.

[0095] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to such examples.

[0096] The sodium fluorosulfate and sodium tetrafluorooxalatophosphate used in the examples and comparative examples were synthesized as follows.

[0097] (Synthesis of sodium fluorosulfate) -35°C, N ２ In ethyl methyl carbonate (hereinafter abbreviated as EMC) solvent (100 mL) in which NaF (7.0 g, 167 mmol) is dispersed under atmospheric conditions, SO4 is added. ３ (6.5 g, 81 mmol) was added and stirred for 1 hour. The reaction mixture was filtered, and the filtrate was concentrated to dryness to obtain NaSO4. ３ We obtained F (8.4 g) (yield 85%). １９ F NMR (CD) ３ NC)σ36.9ppm

[0098] (Synthesis of sodium tetrafluorooxalatophosphate) 25°C, N ２ NaPF under atmospheric conditions ６ (8.5 g, 51 mmol) was dissolved in 100 mL of EMC, oxalic acid (4.7 g, 52 mmol) was added, and then SiCl ４(4.4 g, 25 mmol) was added dropwise over 60 minutes, and the mixture was stirred for 1 hour. The reaction mixture was filtered, and SOCl was added to the filtrate. ２ 0.9 g of was added and stirred at 40°C for 3 hours. The reaction mixture was cooled to 25°C, filtered, and the filtrate was concentrated to dryness to obtain sodium tetrafluorooxalatophosphate (8.9 g) (yield 80%). １９ F NMR (CD) ３ NC) σ -58.0ppm, -60.0ppm, -74.2ppm, -76.2ppm

[0099] [Preparation of Electrolyte for Non-Aqueous Sodium Ion Battery] (Preparation of Non-Aqueous Electrolyte 1-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, ethylene carbonate (hereinafter abbreviated as EC), dimethyl carbonate (hereinafter abbreviated as DMC), and EMC were used as non-aqueous organic solvents (also simply called non-aqueous solvents) and mixed in a volume ratio of EC:DMC:EMC = 3:3:4. Then, NaPF was used as the main electrolyte. ６ The substance was added and dissolved in the non-aqueous electrolyte to a concentration of 1.0 mol / L. Non-aqueous electrolyte 1-1 was prepared by adding and dissolving 1.4 ppm by mass of HF as Brønsted acid and 1.0% by mass of sodium fluorosulfate as fluorosulfate salt.

[0100] Non-aqueous electrolytes 1-2 to 1-8, 2-1 to 2-7, and comparative non-aqueous electrolytes 0-1 to 0-4, 1-1 to 1-9, and 2-1 to 2-7, as described in Tables 1 to 8, were prepared in the same manner as non-aqueous electrolyte 1-1, except that the solubility amounts of Brønsted acid and fluorosulfate were set to the concentrations described in Tables 1 to 8.

[0101] (Preparation of non-aqueous electrolyte 3-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC, DMC, and EMC were used as non-aqueous solvents and mixed in a volume ratio of EC:DMC:EMC = 3:3:4. Then, NaPF was used as the main electrolyte. ６ H was added and dissolved in the non-aqueous electrolyte solution to a concentration of 1.0 mol / L. ２ SO ４Non-aqueous electrolyte 3-1 was prepared by adding sodium fluorosulfate as a fluorosulfate to a concentration of 1.0% by mass to the mixture to a concentration of 1.2 ppm by mass and dissolving it.

[0102] For the non-aqueous electrolytes 3-2 to 3-12 and comparative non-aqueous electrolytes 0-5 to 0-6 and 3-1 to 3-12 listed in Table 9, the Brønsted acid is HSO4. ３ The solution was prepared in the same manner as non-aqueous electrolyte 3-1, except that F was used and the concentrations of Brønsted acid and fluorosulfate were set to those listed in Table 9.

[0103] (Preparation of non-aqueous electrolyte 4-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC and EMC were used as non-aqueous solvents and mixed in a volume ratio of EC:EMC = 3:7. Then, NaPF was used as the main electrolyte. ６ The substance was added and dissolved in the non-aqueous electrolyte so that its content was 1.0 mol / L. Non-aqueous electrolyte 4-1 was prepared by adding and dissolving HF as Brønsted acid at 25.1 ppm by mass, sodium fluorosulfate as fluorosulfate at 1.0% by mass, and fluoroethylene carbonate (hereinafter abbreviated as FEC) as other components at 0.5% by mass.

[0104] Non-aqueous electrolytes 4-0, 4-2 to 4-4, and comparative non-aqueous electrolyte 0-7, as described in Table 10, were prepared in the same manner as non-aqueous electrolyte 4-1, except that they used chloroethylene carbonate (hereinafter abbreviated as CEC), vinylene carbonate (hereinafter abbreviated as VC), and 1,3,2-dioxathione 2,2-dioxide (hereinafter abbreviated as DTD) as other components, and the solubility of other components, Brønsted acid, and fluorosulfate was set to the concentrations shown in Table 10.

[0105] (Preparation of non-aqueous electrolyte 5-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC, EMC, and diethyl carbonate (hereinafter abbreviated as DEC) were used as non-aqueous solvents and mixed in a volume ratio of EC:EMC:DEC = 3:4:3. Then, NaPF was added as the main electrolyte. ６ and NaN(SO ２ F) ２(Hereinafter referred to as NaFSI) was added to the non-aqueous electrolyte at a concentration of 0.5 mol / L each (total 1 mol / L) and dissolved. Non-aqueous electrolyte 5-1 was prepared by adding and dissolving 25.2 ppm by mass of HF as Brønsted acid, 1.0% by mass of sodium fluorosulfate as a fluorosulfate, and 0.5% by mass of sodium difluorobisoxalatophosphate (hereinafter abbreviated as NaDFBOP) as other components.

[0106] Non-aqueous electrolytes 5-0, 5-2 to 5-4, and comparative non-aqueous electrolyte 0-8, as described in Table 11, were prepared in the same manner as non-aqueous electrolyte 5-1, except that they use sodium difluorophosphate (hereinafter abbreviated as NaDFP), sodium tetrafluorooxalatophosphate (hereinafter abbreviated as NaTFOP), and sodium difluorooxalatoborate (hereinafter abbreviated as NaDFOB) as other components, and the concentrations of other components, Brønsted acid, and fluorosulfate are as shown in Table 11.

[0107] (Preparation of non-aqueous electrolyte 6-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC, EMC, and methyl acetate (hereinafter abbreviated as MA) were used as non-aqueous solvents and mixed in a volume ratio of EC:EMC:MA = 3:5:2. Then, NaPF was used as the main electrolyte. ６ The substance was added and dissolved in the non-aqueous electrolyte to a concentration of 1.0 mol / L. Non-aqueous electrolyte 6-1 was prepared by adding and dissolving HF as Brønsted acid to a concentration of 24.9 ppm by mass and sodium fluorosulfate as a fluorosulfate to a concentration of 1.0% by mass.

[0108] Non-aqueous electrolytes 6-2 to 6-6, as described in Table 12, were prepared in the same manner as non-aqueous electrolyte 6-1, except that the type and content ratio of the non-aqueous solvent were changed as described in Table 12, and the concentrations of Brønsted acid and fluorosulfate were set to those described in Table 12.

[0109] (Preparation of non-aqueous electrolyte 7-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC, EMC, and methyl propionate (hereinafter abbreviated as MP) were used as non-aqueous solvents and mixed in a volume ratio of EC:EMC:MP = 3:5:2. Then, NaPF was used as the main electrolyte. ６ and NaN(SO ２ F) ２ (Hereinafter referred to as NaFSI) was added to the non-aqueous electrolyte and dissolved so that the content of each was 0.5 mol / L (total 1 mol / L). Non-aqueous electrolyte 7-1 was prepared by adding and dissolving HF as Brønsted acid at a concentration of 25.4 ppm by mass and sodium fluorosulfate as a fluorosulfate at a concentration of 1.0% by mass.

[0110] Non-aqueous electrolytes 7-2 to 7-5, as described in Table 13, were prepared in the same manner as non-aqueous electrolyte 7-1, except that the type and content ratio of the non-aqueous solvent were changed as described in Table 13, and the concentrations of Brønsted acid and fluorosulfate were set to those described in Table 13.

[0111] (Preparation of non-aqueous electrolyte 8-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC, EMC, and acetonitrile (hereinafter abbreviated as AN) were used as non-aqueous solvents and mixed in a volume ratio of EC:EMC:AN = 3:5:2. Then, NaPF was used as the main electrolyte. ６ The substance was added and dissolved in the non-aqueous electrolyte to a concentration of 1.0 mol / L. Non-aqueous electrolyte 8-1 was prepared by adding and dissolving HF as Brønsted acid to a concentration of 24.7 ppm by mass and sodium fluorosulfate as a fluorosulfate to a concentration of 1.0% by mass.

[0112] Non-aqueous electrolytes 8-2, comparative non-aqueous electrolytes 0-9 to 0-10, and 8-1, as described in Table 14, were prepared in the same manner as non-aqueous electrolyte 8-1, except that the type and content ratio of the non-aqueous solvent were changed as described in Table 14, and the solubility of Brønsted acid and fluorosulfate was set to the concentrations described in Table 14.

[0113] (Preparation of non-aqueous electrolyte 9-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC, PC, and EMC were used as non-aqueous solvents and mixed in a volume ratio of EC:PC:EMC = 2:2:6. Then, NaPF was used as the main electrolyte. ６ The Brønsted acid was added and dissolved in the non-aqueous electrolyte to a concentration of 1.0 mol / L. NaHSO4 was used as the Brønsted acid. ４ Non-aqueous electrolyte 9-1 was prepared by adding sodium fluorosulfate as a fluorosulfate to a concentration of 1.0% by mass to the mixture to a concentration of 33.5 ppm by mass and dissolving it.

[0114] The comparative non-aqueous electrolytes 0-11 to 0-12 and 9-1 listed in Table 15 were prepared in the same manner as non-aqueous electrolyte 9-1, except that the solubility of Brønsted acid and fluorosulfate was set to the concentrations listed in Table 15.

[0115] (Preparation of non-aqueous electrolyte 10-1) Under a nitrogen atmosphere with a dew point of -60°C or lower, EC, PC, and EMC were used as non-aqueous solvents and mixed in a volume ratio of EC:PC:EMC = 2:2:6. Then, NaPF was used as the main electrolyte. ６ The Brønsted acid was added and dissolved in the non-aqueous electrolyte to a concentration of 1.0 mol / L. NaHSO4 was used as the Brønsted acid. ４ To achieve a concentration of 32.9 ppm by mass, sodium fluorosulfate is added as a fluorosulfate salt to a concentration of 1.0% by mass, and other components include POF ２ OCH ３ Non-aqueous electrolyte 10-1 was prepared by adding 0.5% by mass of and dissolving it.

[0116] Non-aqueous electrolytes 10-2 to 10-4, as described in Table 16, were prepared in the same manner as non-aqueous electrolyte 10-1, except that the type and content ratio of the non-aqueous solvent were changed as described in Table 16, the compounds listed in Table 16 were used as other components, and the concentrations of the other components, Brønsted acid, and fluorosulfate were set to those listed in Table 16.

[0117] The concentration of Brønsted acid in the electrolyte for non-aqueous sodium-ion batteries was measured and calculated using neutralization titration as follows, and is shown in each table.

[0118] (Measurement of Brønsted acid concentration in non-aqueous electrolyte) After drying at 150°C for more than 24 hours, a 300 mL fluororesin beaker was cooled to around room temperature (25°C) under a dry nitrogen atmosphere with a dew point of -70°C or lower. 100 mL of acetone (Wako Pure Chemical Industries, ultra-dehydrated product) and a few drops of bromophenol blue ethanol solution (Wako Pure Chemical Industries, Ltd.) were added to the beaker. 50.0 g of the above-mentioned non-aqueous electrolyte was added, and neutralization titration was performed with a 0.002 N or 0.1 N triethylamine / acetone solution while stirring. (Wako Pure Chemical Industries, ultra-dehydrated product acetone and Wako Pure Chemical Industries, special grade triethylamine, dehydrated to a moisture content of 100 ppm by mass or less were used.) The endpoint was defined as the point at which the color of the solution changed from yellow to purple. The volume of the triethylamine / acetone solution used was A ([L]), the concentration of the triethylamine / acetone solution used was B ([N]), and the molecular weight of Brønsted acid was C ([g / mol]). The concentration of Brønsted acid in the sample was calculated using the following formula: Brønsted acid concentration [mass ppm] = A × B × C × 1000 / 50.0 × 1000

[0119] [Fabrication of Non-Aqueous Sodium Ion Battery] (Fabrication of NFM111 Positive Electrode) Na[Ni １／３ Fe １／３ Mn １／３ ]O ２ A cathode composite paste was prepared by mixing 92.0% by mass of powder with 3.8% by mass of acetylene black as a conductive material, 0.2% by mass of carbon nanotubes (hereinafter also referred to as "CNT"), and 4.0% by mass of polyvinylidene fluoride (hereinafter also referred to as "PVDF") as a binder, and then adding NMP. This paste was applied to both sides of aluminum foil (A1085), dried and pressurized, and then punched out to a 4cm x 5cm rectangle to obtain a test NFM111 cathode.

[0120] (Preparation of hard carbon anode) 94% by mass of hard carbon powder was mixed with 2% by mass of acetylene black, 1% by mass of carbon nanofiber (Showa Denko, VGCF), 2% by mass of styrene-butadiene rubber (hereinafter also referred to as "SBR"), and 1% by mass of carboxymethylcellulose sodium (hereinafter also referred to as "CMC"). Water was then added to prepare an anode composite paste. This paste was applied to aluminum foil (A1085), dried, and pressurized, and then punched out to 4.5 cm x 5.5 cm to obtain a test hard carbon anode.

[0121] (Fabrication of a non-aqueous sodium-ion battery) Under an argon atmosphere with a dew point of -50°C or lower, terminals were welded to the NFM111 positive electrode as described above. Then, one polyethylene separator (5 cm x 6 cm) was placed on each side of the positive electrode. On the outside of these, one hard carbon negative electrode, with terminals welded to it in advance, was placed so that the separators were sandwiched between the positive and negative electrodes, with the negative electrode active material surface facing the positive electrode active material surface. This assembly was placed in an aluminum laminate bag with an opening on one side, and after vacuum injection of the non-aqueous electrolyte, the opening was sealed with heat to fabricate an aluminum laminate type non-aqueous sodium-ion battery (hereinafter also simply referred to as a "cell").

[0122] [Examples 1-1 to 1-8, Comparative Examples 0-1 to 0-2, 1-1 to 1-10] Non-aqueous sodium ion batteries prepared using the non-aqueous electrolytes listed in Table 1 were subjected to initial power output tests and high-temperature storage characteristic tests, and the initial power output characteristics at -20°C and the gas generation amount at 70°C storage were evaluated. The evaluation results are shown in Table 1. The evaluation results for the Examples and Comparative Examples in Table 1 are relative values ​​with the evaluation result of Comparative Example 0-1 set to 100%. Note that a larger value for "initial power output characteristics at -20°C" is desirable, and a smaller value for "gas generation amount at 70°C storage" is desirable.

[0123] [Evaluation Conditions] <Initial Charge / Discharge> The cells prepared as described above were left to stand for 6 hours in a 25°C environment (impregnation time: 6 hours), and then conditioning was performed in a 25°C environment under the following conditions. Specifically, for the initial charge / discharge, the cells were charged with a constant current and voltage at a maximum charge voltage of 3.1V and a rate of 0.1C (6mA), and then left to stand for 24 hours in a 50°C environment. After that, the cells were charged with a constant current and voltage at a maximum charge voltage of 4.0V and a rate of 0.1C (6mA) in a 25°C environment, discharged at a constant current and a rate of 0.2C until the discharge termination voltage reached 1.5V, and then charged with a constant current and voltage at a maximum charge voltage of 4.0V and a rate of 0.2C, and discharged at a constant current and a rate of 0.2C until the discharge termination voltage reached 1.5V. This charge / discharge cycle was repeated three times.

[0124] <Initial Output Test> The cells that underwent the above conditioning were charged at a constant current and voltage at a maximum charge voltage of 4.0V and a rate of 0.1C in a 25°C environment, and then discharged at a constant current and a rate of 0.1C until the discharge termination voltage was 1.5V. After that, they were charged at a constant current and voltage at a maximum charge voltage of 4.0V and a rate of 0.1C, and then discharged at a constant current and a rate of 3.0C until the discharge termination voltage was 1.5V in a -20°C environment. The "initial -20°C output characteristics" were calculated using the following formula: Initial -20°C output characteristics (%) = (discharge capacity at -20°C and a rate of 3C / discharge capacity at 25°C and a rate of 0.1C) × 100 In the example table, the relative values ​​are shown with the above initial -20°C output characteristics of the comparative example set to 100.

[0125] <High Temperature (70°C) Storage Characteristics Test> The cells that underwent the above conditioning were charged at a constant current and constant voltage at a maximum charge voltage of 4.0V and a rate of 0.2C in a 25°C environment, and then stored in a 70°C environment for 10 days. After the above storage test, the cells were discharged at a constant current of 0.2C to a discharge termination voltage of 1.5V in a 25°C environment. Before and after the high temperature storage test, the volume of the cells was measured using the Archimedes method with silicone oil (Shin-Etsu Chemical Co., Ltd., Silicone Oil KF54), and the gas generation amount V (unit: cm) for the 70°C storage test was measured. ３ The gas generation amount V was calculated as follows: (Gas generation amount V = Volume of the cell after high-temperature storage characteristics evaluation V2 - Volume of the cell before high-temperature storage characteristics evaluation V1). Based on this gas generation amount V, the "gas generation amount for 70°C storage test" was evaluated.

[0126]

[0127] From the evaluation results in Table 1, it was found that by including both (I) and a predetermined amount of (II) in the non-aqueous electrolyte (for example, Example 1-1), the initial low-temperature power characteristics and the effect of suppressing gas generation during high-temperature storage were further improved compared to simply adding together the effects of the addition when only (I) was included (Comparative Example 0-2) and the addition when only (II) was included (Comparative Example 1-1).

[0128] [Examples 2-1 to 2-7, Comparative Examples 0-3 to 0-4, 2-1 to 2-7] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Tables 2 to 8 were subjected to initial power output tests and high-temperature storage characteristic tests. The initial power output characteristics at -20°C and the gas generation amount during storage at 70°C were evaluated in the same manner. The evaluation results are shown in Tables 2 to 8. The evaluation results for the examples and comparative examples in Tables 2 to 8 are relative values ​​with the evaluation result of Comparative Example 0-3 set to 100%.

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136] The evaluation results in Tables 2 to 8 also show that by including both (I) and a predetermined amount of (II) in the non-aqueous electrolyte (for example, Example 2-1), the initial low-temperature power characteristics and the gas generation suppression effect during high-temperature storage are further improved compared to simply adding together the effects of the addition when only (I) is included (Comparative Example 2-1) and the addition when only (II) is included (Comparative Example 0-4).

[0137] [Examples 3-1 to 3-12, Comparative Examples 0-5 to 0-6, 3-1 to 3-12] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Table 9 were subjected to initial power output tests and high-temperature storage characteristic tests. The initial power output characteristics at -20°C and the gas generation amount during 70°C storage tests were evaluated in the same manner. The evaluation results are shown in Table 9. The evaluation results for the Examples and Comparative Examples in Table 9 are relative values ​​with the evaluation results for Comparative Example 0-5 set to 100%.

[0138]

[0139] The evaluation results in Table 9 show that a similar trend was observed even when acids other than HF were used as proton-generating acids.

[0140] [Examples 4-0 to 4-4, Comparative Example 0-7] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Table 10 were subjected to initial power output tests and high-temperature storage characteristics tests, and the initial power output characteristics at -20°C and the gas generation amount during 70°C storage tests were evaluated in the same manner. The evaluation results are shown in Table 10. The evaluation results for the examples and comparative examples in Table 10 are relative values ​​with the evaluation results for Comparative Example 0-7 set to 100%.

[0141]

[0142] The evaluation results in Table 10 show that including other components in the non-aqueous electrolyte further improves the initial low-temperature power characteristics and the gas generation suppression effect during high-temperature storage.

[0143] [Examples 5-0 to 5-4, Comparative Example 0-8] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Table 11 were subjected to initial power output tests and high-temperature storage characteristics tests, and the initial power output characteristics at -20°C and the gas generation amount during storage at 70°C were evaluated in the same manner. The evaluation results are shown in Table 11. The evaluation results for the examples and comparative examples in Table 11 are relative values ​​with the evaluation results for Comparative Example 0-8 set to 100%.

[0144]

[0145] From the evaluation results in Table 11, it was found that even when using multiple types of (III) sodium salts, including other components in the non-aqueous electrolyte further improves the initial low-temperature power characteristics and the effect of suppressing gas generation during high-temperature storage.

[0146] [Examples 6-1 to 6-6, Comparative Example 0-1] Non-aqueous sodium ion batteries prepared using the non-aqueous electrolytes listed in Table 12 were subjected to initial power output tests and high-temperature storage characteristics tests. The initial power output characteristics at -20°C and the gas generation amount during storage at 70°C were evaluated in the same manner. The evaluation results are shown in Table 12. The evaluation results for the examples and comparative examples in Table 12 are relative values ​​with the evaluation result of Comparative Example 0-1 set to 100%.

[0147]

[0148] The evaluation results in Table 12 show that the initial low-temperature power characteristics are further improved when the non-aqueous solvent in the non-aqueous electrolyte contains MA, EA, DME, etc.

[0149] [Examples 7-1 to 7-5, Comparative Example 0-8] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Table 13 were subjected to initial power output tests and high-temperature storage characteristics tests. The initial power output characteristics at -20°C and the gas generation amount during storage at 70°C were evaluated in the same manner. The evaluation results are shown in Table 13. The evaluation results for the examples and comparative examples in Table 13 are relative values ​​with the evaluation results for Comparative Example 0-8 set to 100%.

[0150]

[0151] From the evaluation results in Table 13, it was found that when using multiple types of (III) sodium salts, the inclusion of MP, EP, etc., in the non-aqueous electrolyte further improves the initial low-temperature power characteristics and the gas generation suppression effect during high-temperature storage.

[0152] [Examples 8-1 to 8-2, Comparative Examples 0-9 to 0-10, 8-1] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Table 14 were subjected to initial power output tests and high-temperature storage characteristic tests, and the initial power output characteristics at -20°C and the gas generation amount during 70°C storage tests were evaluated in the same manner. The evaluation results are shown in Table 14. The evaluation results for the examples and comparative examples in Table 14 are relative values ​​with the evaluation results of Comparative Example 0-9 set to 100%.

[0153]

[0154] The evaluation results in Table 14 show that even when the non-aqueous solvent in the non-aqueous electrolyte contains AN, etc., the initial low-temperature power characteristics and the effect of suppressing gas generation during high-temperature storage are improved.

[0155] [Example 9-1, Comparative Examples 0-11 to 0-12, 9-1] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Table 15 were subjected to initial power output tests and high-temperature storage characteristics tests. The initial power output characteristics at -20°C and the gas generation amount during storage at 70°C were evaluated in the same manner. The evaluation results are shown in Table 15. The evaluation results for the Examples and Comparative Examples in Table 15 are relative values ​​with the evaluation results for Comparative Example 0-11 set to 100%.

[0156]

[0157] From the evaluation results in Table 15, NaHSO4 is used as the Brønsted acid. ４ It was found that even when using acids other than HF, the initial low-temperature power output characteristics and the effect of suppressing gas generation during high-temperature storage were improved.

[0158] [Examples 10-1 to 10-4, Comparative Examples 0-11] Non-aqueous sodium-ion batteries prepared using the non-aqueous electrolytes listed in Table 16 were subjected to initial power output tests and high-temperature storage characteristics tests. The initial power output characteristics at -20°C and the gas generation amount during storage at 70°C were evaluated in the same manner. The evaluation results are shown in Table 16. The evaluation results for the Examples and Comparative Examples in Table 16 are relative values ​​with the evaluation results for Comparative Examples 0-11 set to 100%.

[0159]

[0160] From the evaluation results in Table 16, POF is included as another component in the non-aqueous electrolyte. ２ OCH ３ , POF ２ OC ２ H ５ It was found that including these ingredients further improves the initial low-temperature power output characteristics and the gas generation suppression effect during high-temperature storage.

[0161] According to this disclosure, it is possible to provide an electrolyte for non-aqueous sodium-ion batteries that exhibits excellent initial low-temperature power output characteristics and excellent suppression of gas generation during high-temperature storage when used in non-aqueous sodium-ion batteries, a non-aqueous sodium-ion battery using the same, and a method for manufacturing the same.

[0162] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2024-231781, filed on 27 December 2024, the contents of which are incorporated herein by reference.

Claims

1. An electrolyte for a non-aqueous sodium-ion battery comprising (I) a fluorosulfate, (II) a Brønsted acid, (III) a sodium salt, and (IV) a non-aqueous organic solvent, wherein the content of (II) is 0.8 ppm by mass to 600 ppm by mass relative to the total amount of the electrolyte for a non-aqueous sodium-ion battery.

2. The electrolyte for a non-aqueous sodium ion battery according to claim 1, wherein the content of (II) is 3.0 ppm by mass to 300 ppm by mass relative to the total amount of the electrolyte for a non-aqueous sodium ion battery.

3. The above (II) is HF, H ２ SO ４ HSO ３ F, NaHSO ４ , and HPO ２ F ２ The electrolyte for a non-aqueous sodium-ion battery according to claim 1, which is at least one selected from the group consisting of the following.

4. The electrolyte for a non-aqueous sodium ion battery according to claim 1, wherein the content of (I) is 0.008% by mass to 7.5% by mass relative to the total amount of the electrolyte for a non-aqueous sodium ion battery.

5. The electrolyte for a non-aqueous sodium-ion battery according to claim 1, wherein the countercation of (I) is a lithium ion, a sodium ion, a potassium ion, a tetraalkylammonium ion, a tetraalkylphosphonium ion, or an ammonium ion having a spiro skeleton.

6. The (III) is at least one selected from the group consisting of NaPF ６ , NaBF ４ , NaSbF ６ , NaAsF ６ , NaClO ４ , NaN(SO ２ F) ２ , NaAlO ２ , NaAlCl ４ , NaCl and NaI, and is the electrolyte for a non-aqueous sodium ion battery according to claim 1.

7. The electrolyte for a non-aqueous sodium-ion battery according to claim 1, wherein the concentration of (III) is 0.3 mol / L to 5.0 mol / L relative to the total amount of electrolyte for a non-aqueous sodium-ion battery.

8. The electrolyte for a non-aqueous sodium ion battery according to claim 1, wherein (IV) comprises at least one selected from the group consisting of cyclic esters, linear esters, cyclic ethers, linear ethers, sulfone compounds, sulfoxide compounds, nitrile compounds, and ionic liquids.

9. The electrolyte for a non-aqueous sodium-ion battery according to claim 8, wherein the cyclic ester comprises a cyclic carbonate.

10. The electrolyte for a non-aqueous sodium-ion battery according to claim 9, wherein the cyclic carbonate comprises at least one selected from the group consisting of ethylene carbonate and propylene carbonate.

11. The electrolyte for a non-aqueous sodium-ion battery according to claim 8, wherein the chain-like ester comprises a chain-like carbonate.

12. The electrolyte for a non-aqueous sodium-ion battery according to claim 11, wherein the chain-like carbonate comprises at least one selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and methyl propyl carbonate.

13. The electrolyte for a non-aqueous sodium-ion battery according to claim 8, wherein the cyclic ether comprises at least one selected from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, furan, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, and trioxane.

14. The electrolyte for a non-aqueous sodium-ion battery according to claim 8, wherein the chain ether comprises at least one selected from the group consisting of diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, 1,2-dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

15. The electrolyte for a non-aqueous sodium-ion battery according to claim 1, wherein (IV) comprises at least one selected from the group consisting of methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, tetrahydrofuran, 1,2-dimethoxyethane, acetonitrile, and propionitrile.

16. Furthermore, cyclohexylbenzene, cyclohexylfluorobenzene, biphenyl, 2-fluorobiphenyl, tert-butylbenzene, tert-amylbenzene, 2-fluorotoluene, fluorobenzene, difluoroanisole, vinylene carbonate, vinylene carbonate oligomers (number average molecular weight in polystyrene terms of 170-5000), vinylethylene carbonate, divinylethylene carbonate, fluoroethylene carbonate, ethynylethylene carbonate, trans-difluoroethylene carbonate, methylpropargyl carbonate, ethylpropargyl carbonate, dipropargyl carbonate, dimethylvinylene carbonate, dimethyl dicarbonate, bis(1,1,1,3,3,3-hexafluoro-1-propyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 1,6-diisocyanatohexa N, maleic anhydride, succinic anhydride, 1,4-dioxan-2,6-dione, glutaric anhydride, methanedisulfonic anhydride, 1,2-ethanedisulfonic anhydride, methanesulfonic anhydride, 2-sulfobenzoic anhydride, 1,3-propanedisulfonic anhydride, 1,3-propanesultone, 1,3-propensultone, 1,4-butanesultone, 2,4-butanesultone, 1,3,2-dioxathiolan-2,2-dioxide, 4-pro Pyr-1,3,2-dioxathiolan-2,2-dioxide, 1,3-dithiolan-1,1,3,3-tetraoxide, 1,3-dithian-1,1,3,3-tetraoxide, 1,2-oxathiolan-5-one-2,2-dioxide, methylene methane disulfate, dimethyl methane disulfate, trimethylene methane disulfate, methyl methanesulfonate, methanesulfonyl fluoride, ethensulfonyl fluoride, N,N'-Carbonylbis(N-methylsulfamoylfluoride), difluoro(picolinato)borate, phenyl difluorophosphate, trippropargyl phosphate, tetrafluoro(picolinato)phosphate, (ethoxy)pentafluorocyclotriphosphazene, succinonitrile, methyldifluorovinylsilane, methylfluorodivinylsilane, dimethyldivinylsilane, trivinylmethylsilane, trivinylfluorosilane, tetravinylsilane, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate, 1,3-dimethyl-1,3-divinyl-1,3-di(1,1,1,3,3,3-Hexafluoroisopropyl)disiloxane, trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, monomethyl sulfate, monoethyl sulfate, bis(trifluoromethanesulfonyl)imide, bis(pentafluoroethanesulfonyl)imide, (trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide, (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide, (trifluoromethanesulfonyl)(fluorosulfonyl)imide, (pentafluoroethanesulfonyl)(fluorosulfonyl)imide, (difluorophosphoryl)(fluorosulfonyl)imide, (difluorophosphoryl)(trifluoromethanesulfonyl)imide, bis(difluorophosphoryl)imide, (fluorosulfonyl) The electrolyte for a non-aqueous sodium-ion battery according to claim 1, comprising at least one selected from the group consisting of lithium carbonyloxymethanesulfonate, (fluorosulfonyl)(carbonyldi(2-propenyl)phosphoryl)imide salt, (carbonyldi(propargyl)phosphoryl)imide salt, monofluorophosphate, difluorophosphate, tetrafluoro(malonato)phosphate, tris(oxalato)phosphate, difluorobis(oxalato)phosphate, tetrafluorooxalatophosphate, bis(oxalato)borate, difluorooxalatoborate, difluoro(malonato)borate, tris(trifluoromethanesulfonyl)methide salt, tris(fluorosulfonyl)methide salt, acrylate, methacrylate, nitrate, nitrite, hexafluoroisopropanol, and trifluoroethanol.

17. The electrolyte for a non-aqueous sodium-ion battery according to claim 1, further comprising a difluorophosphate ester represented by the following general formula (1A). In general formula (1A), R is a hydrocarbon group having 1 to 15 carbon atoms, and any hydrogen atom of the hydrocarbon group may be substituted with a halogen atom.

18. A non-aqueous sodium-ion battery comprising at least a positive electrode, a negative electrode, and an electrolyte for a non-aqueous sodium-ion battery according to any one of claims 1 to 17.

19. A method for manufacturing a non-aqueous sodium ion battery, comprising the step of injecting the electrolyte for a non-aqueous sodium ion battery described in any one of claims 1 to 17.

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