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

Abstract

The present disclosure provides: an electrolyte for a non-aqueous sodium ion battery, the electrolyte including (I) a non-aqueous solvent, (II) sodium, and (III) fluorosulfate, the content of (III) being 0.05-10.00 wt% relative to the total amount of the electrolyte for the non-aqueous sodium ion battery, and the content of a chain carbonate relative to the total amount of (I) being 0-70 wt%; a non-aqueous sodium ion battery provided with at least a positive electrode, a negative electrode, and the electrolyte for the non-aqueous sodium ion battery; and a method for producing the non-aqueous sodium ion battery.

Description

[Technical Field]

[0001] One embodiment of this disclosure relates to an electrolyte for a non-aqueous sodium-ion battery, a non-aqueous sodium-ion battery using the same, and a method for manufacturing the same. [Background technology]

[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 general, non-aqueous sodium-ion batteries use a non-aqueous electrolyte, or a non-aqueous electrolyte that has been pseudo-solidified with a gelling agent, as the ion conductor. In this configuration, an aprotic solvent is used as the solvent, and a sodium salt is used as the solute.

[0004] Furthermore, various non-aqueous electrolyte additives have been investigated to improve the performance of non-aqueous sodium-ion batteries. Patent Document 1 shows that using fluoroethylene carbonate as an additive improves charge-discharge cycle characteristics. Patent Documents 2 and 3 show that using sulfonic acid ester compounds or cyclic sulfate esters as additives improves cycle characteristics and suppresses resistance increase.

[0005] On the other hand, regarding non-aqueous lithium-ion batteries, Patent Document 4 describes that adding fluorosulfates to the electrolyte of a non-aqueous lithium-ion battery improves high-temperature durability and output characteristics. [Prior art documents] [Patent Documents]

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] Although non-aqueous sodium ion batteries have already begun to be commercialized, for applications such as in automobiles that are used in high-temperature locations for a long time, for example, gas generation and cycle characteristics are not yet sufficient, and particularly, the amount of gas generation at temperatures of 60°C or higher is a major problem that needs to be improved. On the other hand, in Patent Document 4, no specific examination has been made on the effect of adding fluorosulfate in a sodium ion secondary battery, and its effect has not been clarified. Therefore, in the present disclosure, an electrolyte for a non-aqueous sodium ion battery that has an excellent gas generation suppression effect at a high temperature of 60°C or higher when used in a non-aqueous sodium ion battery, a non-aqueous sodium ion battery using the same, and a method for manufacturing the same are provided as problems.

Means for Solving the Problems

[0008] As a result of intensive studies in view of such problems, the inventors of the present invention have found that by containing a predetermined amount of fluorosulfate and limiting the content of chain carbonate in the non-aqueous solvent contained in the non-aqueous electrolyte to a predetermined amount or less, a gas generation suppression effect at a high temperature of 60°C or higher, which has not been confirmed in a lithium ion secondary battery, is exhibited in a sodium ion secondary battery.

[0009] That is, the present disclosure includes the following embodiments. <1> (I) Non-aqueous solvent, (II) sodium salt, and (III) Fluorosulfates Includes, The content of (III) above is 0.05% by mass to 10.00% by mass relative to the total amount of electrolyte for non-aqueous sodium ion batteries. The content of linear carbonate relative to the total amount of (I) is 0% by mass or more and less than 1% by mass. Electrolyte for non-aqueous sodium-ion batteries. <2> The content of (III) above is 0.15% by mass to 8.00% by mass relative to the total amount of electrolyte for non-aqueous sodium ion batteries. <1> The electrolyte for non-aqueous sodium ion batteries described above. <3> The countercation of (III) is a lithium ion, a sodium ion, a potassium ion, a tetraalkylammonium ion, a tetraalkylphosphonium ion, or an ammonium ion having a spiro skeleton. <1> or <2> The electrolyte for non-aqueous sodium ion batteries described above. <4> The above (I) includes at least one selected from the group consisting of cyclic esters, linear esters other than linear carbonates, cyclic ethers, and linear ethers. <1> ~ <3> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <5> The above (I) includes a cyclic ester, The cyclic ester is a cyclic carbonate. <4> The electrolyte for non-aqueous sodium ion batteries described above. <6> As (I) above, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, ethyl propionate, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether, <4> The electrolyte for non-aqueous sodium ion batteries described above. <7> The chain-like carbonate is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, methyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate, and ethyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate. <1> ~ <6> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <8> The above (II) is NaPF 6 NaBF 4 NaBF 2 (C 2 O 4 ), NaPF 4 (C 2 O 4 ), NaPF 2 (C 2 O 4 ) 2 NaSbF 6 NaAsF 6 NaPaul 4 , NaN(SO 2 F) 2 , NaN(SO 2 CF 3 ) 2 , NaN(SO 2 F)(SO 2 CF 3 ), NaN(C a F 2a+1 SO 2 )(C b F 2b+1 SO 2 (Here, a and b are integers satisfying 2 ≤ a ≤ 20 and 2 ≤ b ≤ 20.) NaSO 3 CF 3 , NaSO 3 C 4 F 9 NaN(POF 2 ) 2 NaN(POF 2 )(SO 2 F), NaPO 2 F 2 NaC(SO 2 CF 3 ) 3 naPF 3 (C 3 F 7 ) 3 NaB(CF 3 ) 4 NaBF 3 (C 2 F 5 ), NaAlO 2 , NaAlCl 4 At least one selected from the group consisting of NaCl and NaI, <1> ~ <7> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <9> As (II) above, NaPF 6 including, <1> ~ <8> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <10> At least a positive electrode and a negative electrode, <1> ~ <9> A non-aqueous sodium-ion battery comprising an electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <11> <1> ~ <9> A method for manufacturing a non-aqueous sodium ion battery, comprising the steps of preparing an electrolyte for a non-aqueous sodium ion battery as described in any one of the items, and filling an empty cell equipped with at least a positive electrode and a negative electrode with the electrolyte for a non-aqueous sodium ion battery. This disclosure is as described above. <1> ~ <11> The above describes the manner in which the above occurred, but other matters (for example, [1] to

[13] below) are also described below.

[0010] [1] (I) Non-aqueous solvent, (II) sodium salt, and (III) Fluorosulfates Includes, The content of (III) above is 0.05% by mass to 10.00% by mass relative to the total amount of electrolyte for non-aqueous sodium ion batteries. An electrolyte for non-aqueous sodium ion batteries, wherein the content of chain-like carbonate relative to the total amount of (I) is 0% to 70% by mass.

[0011] [2] The electrolyte for a non-aqueous sodium-ion battery according to [1], wherein the content of (III) is 0.15% by mass to 8.00% by mass with respect to the total amount of the electrolyte for a non-aqueous sodium-ion battery. [3] The electrolyte for a non-aqueous sodium ion battery according to [1] or [2], wherein the content of chain carbonate relative to the total amount of (I) is 0% to 65% by mass.

[0012] [4] The electrolyte for a non-aqueous sodium ion battery according to any one of [1] to [3], wherein the content of chain carbonate relative to the total amount of (I) is 0% to 62% by mass. [5] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [4], wherein the countercation of (III) is a lithium ion, a sodium ion, a potassium ion, a tetraalkylammonium ion, a tetraalkylphosphonium ion, or an ammonium ion having a spiro skeleton.

[0013] [6] The electrolyte for a non-aqueous sodium ion battery according to any one of [1] to [5], wherein (I) comprises at least one selected from the group consisting of cyclic esters, linear esters other than linear carbonates, cyclic ethers, and linear ethers. [7] The above (I) includes a cyclic ester, The electrolyte for a non-aqueous sodium-ion battery according to [6], wherein the cyclic ester is a cyclic carbonate.

[0014] [8] The electrolyte for a non-aqueous sodium-ion battery according to [6], wherein (I) comprises at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, ethyl propionate, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

[0015] [9] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [8], wherein the chain-like carbonate is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, methyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate.

[0016]

[10] The above (II) is NaPF6, NaBF4, NaBF2(C2O4), NaPF4(C2O4), NaPF2(C2O4)2, NaSbF6, NaAsF6, NaClO4, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2F)(SO2CF3), NaN(C a F 2a+1 SO2)(C b F 2b+1 An electrolyte for a non-aqueous sodium-ion battery as described in any one of [1] to [9], wherein at least one selected from the group consisting of SO2) (where a and b are integers satisfying 2 ≤ a ≤ 20 and 2 ≤ b ≤ 20), NaSO3CF3, NaSO3C4F9, NaN(POF2)2, NaN(POF2)(SO2F), NaPO2F2, NaC(SO2CF3)3, NaPF3(C3F7)3, NaB(CF3)4, NaBF3(C2F5), NaAlO2, NaAlCl4, NaCl, and NaI.

[0017]

[11] As (II) above, an electrolyte for a non-aqueous sodium ion battery according to any one of [1] to

[10] , comprising NaPF6.

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

[11] .

[13] The process of preparing an electrolyte for a non-aqueous sodium ion battery as described in any one of items [1] to

[11] , and A step of filling an empty cell, which is equipped with at least a positive electrode and a negative electrode, with the electrolyte for a non-aqueous sodium ion battery. A method for manufacturing a non-aqueous sodium-ion battery. [Effects of the Invention]

[0018] The embodiments of this disclosure provide an electrolyte for non-aqueous sodium-ion batteries that exhibits excellent gas generation suppression effects at high temperatures of 60°C or higher when used in non-aqueous sodium-ion batteries, a non-aqueous sodium-ion battery using the same, and a method for manufacturing the same. [Brief explanation of the drawing]

[0019] [Figure 1] This figure shows a plot of the amount of gas generated during high-temperature cycling against the chain carbonate content in (I) for the examples and comparative examples in Table 5. [Modes for carrying out the invention]

[0020] The embodiments of this disclosure will be described below. However, this disclosure can be implemented in various ways without departing from its gist, and is not to be construed as being limited to the embodiments and examples described below. Furthermore, any effects and benefits other than those brought about by the embodiments and examples described below, if they are clear from the description herein or easily predictable to a person skilled in the art, will naturally be considered to be brought about by this disclosure.

[0021] In this specification, "~" is used to mean that the numbers written before and after it include the lower and upper limits, respectively.

[0022] The electrolyte for a non-aqueous sodium ion battery according to one embodiment of the present disclosure is: (I) Non-aqueous solvent (hereinafter referred to as "component (I)" or simply "(I)") (II) Sodium salt (hereinafter referred to as "component (II)" or simply "(II)"), and (III) Contains fluorosulfates (hereinafter sometimes referred to as "component (III)" or simply "(III)") The content of (III) above is 0.05% by mass to 10.00% by mass relative to the total amount of electrolyte for non-aqueous sodium ion batteries. This is an electrolyte for non-aqueous sodium ion batteries, wherein the content of chain-like carbonate relative to the total amount of (I) is 0% to 70% by mass. Furthermore, if necessary, other commonly known additives can be used in combination.

[0023] The electrolyte for a non-aqueous sodium-ion battery according to this embodiment, with the above configuration, can significantly suppress gas generation at high temperatures of 60°C or higher. Although the details of this mechanism are not clear, it is presumed that by keeping the amount of chain carbonate relative to the total amount of non-aqueous solvent below a predetermined amount, the film formed on the electrode by the fluorosulfate anion in a predetermined amount of fluorosulfate and the solvent becomes optimal, thereby suppressing the decomposition of the solvent thereafter.

[0024] The components of the electrolyte for the non-aqueous sodium-ion battery according to this embodiment will be described in detail below.

[0025] [(I) Non-aqueous solvents] The content of linear carbonate relative to the total amount of non-aqueous solvent in the electrolyte for a non-aqueous sodium-ion battery according to this embodiment is 0% to 70% by mass (hereinafter sometimes referred to as "solvent composition conditions"). That is, the non-aqueous solvent may or may not contain linear carbonate, but if it does contain linear carbonate, the content is 70% by mass or less. As long as the above solvent composition conditions are met, the type of non-aqueous solvent is not particularly limited, and any non-aqueous solvent can be used. For example, cyclic esters, linear esters other than linear carbonates, cyclic ethers, linear ethers, or sulfur-containing non-aqueous solvents may be used. Examples of cyclic esters include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, as well as γ-butyrolactone and γ-valerolactone. Examples of linear esters other than linear carbonates include methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, and 1,3-dioxane. Examples of chain-like ethers include dimethoxyethane, diethoxyethane, diethyl ether, ethoxymethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether. Examples of sulfur-containing non-aqueous solvents include dimethyl sulfoxide and sulfolane. Furthermore, the non-aqueous solvent used in this embodiment may be used alone, or two or more may be mixed in any combination and ratio according to the application.

[0026] Furthermore, the non-aqueous solvent in the electrolyte for the non-aqueous sodium-ion battery according to this embodiment may contain a linear carbonate, provided that the above solvent composition conditions are met. Examples of linear carbonates include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, methyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate, and other linear carbonates such as ethyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate.

[0027] Furthermore, from the viewpoint of suppressing gas generation at high temperatures of 60°C or higher in non-aqueous sodium-ion batteries, the lower the amount of chain-like carbonate in the total amount of (I), the better. Specifically, 0% to 65% by mass is preferred, 0% to 62% by mass is even more preferred, 0% to 60% by mass is even more preferred, 0% to 55% by mass is even more preferred, 0% to 30% by mass is particularly preferred, and it is most preferable that it is substantially free of chain-like carbonate. "Substantially free of linear carbonates" means that the amount of linear carbonates in the total amount of (I) is less than 1% by mass.

[0028] As stated above, the non-aqueous solvent may or may not contain linear carbonates, but if it does contain linear carbonates, the content must be 70% by mass or less. In a preferred embodiment, when a chain-like carbonate is contained in the non-aqueous solvent, the content of the chain-like carbonate in the total amount of (I) is preferably more than 0% to 65% by mass, more preferably more than 0% to 62% by mass, even more preferably more than 0% to 60% by mass, even more preferably more than 0% to 55% by mass, and particularly preferably more than 0% to 30% by mass, based on the total amount of (I). In this case, the content of linear carbonate in the total amount of (I) is preferably more than 0% by mass, more preferably 3% by mass or more, and even more preferably 5% by mass or more.

[0029] In one preferred embodiment, the electrolyte for the non-aqueous sodium-ion battery includes, as the non-aqueous solvent, at least one selected from the group consisting of cyclic esters, linear esters other than linear carbonates, cyclic ethers, and linear ethers. In one preferred embodiment, the electrolyte for the non-aqueous sodium-ion battery contains a cyclic ester as the non-aqueous solvent, wherein the cyclic ester is a cyclic carbonate.

[0030] Further, the non-aqueous sodium ion battery electrolyte preferably contains, as (I), at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, ethyl propionate, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

[0031] As described above, (I) may or may not contain a chain carbonate. The chain carbonate is preferably at least one selected from dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, methyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate, and ethyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate.

[0032] [(II) Sodium salt] The type of the sodium salt as the solute is not particularly limited, and any sodium salt (excluding (III) fluorosulfate described below) can be used. Specific examples include NaPF6, NaBF4, NaBF2(C2O4), NaPF4(C2O4), NaPF2(C2O4)2, NaSbF6, NaAsF6, NaClO4, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2F)(SO2CF3), NaN(C a F 2a+1 SO2)(C b F 2b+1Examples of electrolyte sodium salts include those represented by at least one selected from the group consisting of SO2) (where a and b are integers satisfying 2 ≤ a ≤ 20 and 2 ≤ b ≤ 20), NaSO3CF3, NaSO3C4F9, NaN(POF2)2, NaN(POF2)(SO2F), NaPO2F2, NaC(SO2CF3)3, NaPF3(C3F7)3, NaB(CF3)4, NaBF3(C2F5), NaAlO2, NaAlCl4, NaCl, and NaI. These solutes may be used individually or mixed in any combination and ratio depending on the application. In particular, considering energy density, output characteristics, and lifespan as a battery, NaPF6, NaBF2(C2O4), NaPF4(C2O4), NaPF2(C2O4)2, NaN(SO2F)2, NaN(SO2CF3)2, NaN(SO2C2F5)2, NaN(POF2)2, NaN(POF2)(SO2F), and NaPO2F2 are preferred, and NaPF 6、 NaN(SO2F)2 is more preferred, and NaPF6 is even more preferred. In one preferred embodiment, the electrolyte for the non-aqueous sodium-ion battery contains NaPF6 as the (II) sodium salt.

[0033] The concentration of (II) in the electrolyte for the non-aqueous sodium-ion battery according to this embodiment is not particularly limited, but is preferably 0.3 mol / L or more, more preferably 0.4 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. Setting the electrolyte concentration to 0.3 mol / L or higher makes it easier to suppress the decrease in cycle characteristics of non-aqueous sodium-ion batteries due to a decrease in ionic conductivity. On the other hand, setting the concentration to 5.0 mol / L or lower makes it easier to suppress the increase in viscosity of the electrolyte for non-aqueous sodium-ion batteries and the resulting decrease in battery characteristics due to a decrease in ionic conductivity.

[0034] [(III) Fluorosulfates] The electrolyte for the non-aqueous sodium-ion battery according to this embodiment contains 0.05% to 10.00% by mass of fluorosulfate based on the total amount of electrolyte. If a saturation concentration of fluorosulfate exists within the above concentration range, it is preferable that the upper limit of that concentration range be set to the saturation concentration of fluorosulfate, from the viewpoint of suppressing the generation of excess insoluble components in the electrolyte. The above saturation concentration is at 25°C and 1 atm (=0.10132 MPa).

[0035] Note that fluorosulfates are SO3F - It is an ionic salt having an anion and a countercation represented by . As for the fluorosulfate countercation, there are no particular restrictions on the type, and various types can be selected, as long as they do 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.

[0036] Specific examples 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. In particular, 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.

[0037] 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. The ammonium ion having a spiro skeleton is preferably, for example, 5-azoniaspiron[4.4]nonane.

[0038] The fluorosulfate is not particularly limited, but NaSO3F, LiSO3F, TEMASO3F, SBPSO3F, or TEASO3F are preferred, and NaSO3F, LiSO3F, or TEASO3F are particularly preferred. Here, TEMA represents triethylmethylammonium, SBP represents 5-azoniaspirononane, and TEA represents tetraethylammonium.

[0039] The lower limit of the fluorosulfate content relative to the total amount of electrolyte for non-aqueous sodium-ion batteries is 0.05% by mass. From the viewpoint of suppressing gas generation at high temperatures of 60°C or higher, it is preferably 0.15% by mass or higher, more preferably 0.20% by mass or higher, even more preferably 0.25% by mass or higher, and particularly preferably 0.75% by mass or higher. The upper limit of the fluorosulfate content relative to the total amount of electrolyte for non-aqueous sodium-ion batteries is 10.00% by mass or less. From the viewpoint of suppressing gas generation at high temperatures of 60°C or higher, it is preferably 8.00% by mass or less, more preferably 7.00% by mass or less, even more preferably 6.50% by mass or less, and particularly preferably 5.50% by mass or less. If the content is 0.05% by mass or higher, gas generation in non-aqueous sodium-ion batteries at high temperatures of 60°C or higher can be suppressed. Furthermore, if the concentration is 10.00% by mass or less, the film formed on the electrodes will not become too thick, the decrease in ionic conductivity due to increased viscosity of the electrolyte can be suppressed, and corrosion of the battery's components (metal components) by fluorosulfates can be suppressed, making it less likely to lead to increased resistance or deterioration of the charge-discharge cycle. Furthermore, from the viewpoint of improving high-temperature cycle characteristics, the lower limit of the fluorosulfate content is preferably 0.17% by mass or more, more preferably 0.40% by mass or more, and even more preferably 0.90% by mass or more, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries.

[0040] Fluorosulfates may be used individually, or two or more may be mixed in any combination and ratio depending on the application. In one embodiment, the content of the fluorosulfate is preferably 0.15% to 8.00% by mass, more preferably 0.20% to 7.00% by mass, even more preferably 0.25% to 6.50% by mass, and particularly preferably 0.75% to 5.50% by mass, based on the total amount of electrolyte for the non-aqueous sodium-ion battery.

[0041] [Other additives] Without departing from the spirit of the present invention, the electrolyte for a non-aqueous sodium-ion battery according to this embodiment may contain other additives commonly used in electrolytes for non-aqueous sodium-ion batteries in any proportion. Specific examples include cyclohexylbenzene, biphenyl, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate, vinylene carbonate oligomers (number-average molecular weight of 170 to 5000; here, the number-average molecular weight is the number-average molecular weight on a standard polystyrene basis measured by gel permeation chromatography (GPC) with tetrahydrofuran (THF) as the solvent; the same applies hereinafter), vinylethylene carbonate, difluoroanisole, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynylethylene carbonate, trans-difluoroethylene carbonate, propanesalton, pro Examples of compounds that have overcharge prevention effects, negative electrode film formation effects, and positive electrode protection effects include pensaltone, dimethylvinylene carbonate, 1,3,2-dioxathiolane-2,2-dioxide, 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, methylene methane disulfonate, 1,2-ethane disulfonic anhydride, tris(trimethylsilyl)borate, succinonitrile, (ethoxy)pentafluorocyclotriphosphazene, methanesulfonyl fluoride, tetrafluoro(picolinato)phosphate, and 1,3-dimethyl-1,3-divinyl-1,3-di(1,1,1,3,3,3-hexafluoroisopropyl)disiloxane. Among them, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate, vinylene carbonate oligomers (number average molecular weight 170-5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynylethylene carbonate, trans-difluoroethylene carbonate, propanesalton, propensalton, 1,3,2-dioxathiolan-2,2-dioxide, 4-propyl-1,3,2-dioxathiolan-2,2-dioxide, methylenemethanedisulfonate, 1,2 - At least one compound selected from the group consisting of ethane disulfonic anhydride, tris(trimethylsilyl)borate, succinonitrile, (ethoxy)pentafluorocyclotriphosphazene, methanesulfonyl fluoride, tetrafluoro(picolinato)phosphate, and 1,3-dimethyl-1,3-divinyl-1,3-di(1,1,1,3,3,3-hexafluoroisopropyl)disiloxane is preferred, with vinylene carbonate, fluoroethylene carbonate, 1,3,2-dioxathiolan-2,2-dioxide, or tris(trimethylsilyl)borate being more preferred.

[0042] If the electrolyte for the non-aqueous sodium-ion battery according to this embodiment contains the above-mentioned other additives, the content is preferably 0.01% by mass or more and 10.00% by mass or less relative to the total amount of the electrolyte.

[0043] Furthermore, the above-mentioned sodium salts (sodium salts other than those used as solutes (excluding those corresponding to component (III) above)) can also be used as other additives. When the above sodium salt is used as another additive, the content of the other additive is preferably 0.20% by mass or more and 3.00% by mass or less relative to the total amount of electrolyte.

[0044] Furthermore, other additives may include gelling agents or crosslinking polymers. The electrolyte for non-aqueous sodium-ion batteries according to this embodiment can also be pseudo-solidified using gelling agents or crosslinking polymers, and the pseudo-solidified solution is suitable, for example, for sodium polymer batteries.

[0045] [Non-aqueous sodium ion battery] Next, the configuration of a non-aqueous sodium-ion battery according to one embodiment of the present invention will be described. The non-aqueous sodium-ion battery comprises at least a positive electrode, a negative electrode, and the electrolyte for the non-aqueous sodium-ion battery according to the present embodiment. The non-aqueous sodium-ion battery according to this embodiment is characterized by using the electrolyte for non-aqueous sodium-ion batteries according to this embodiment, and other components are those used in general non-aqueous sodium-ion batteries. Specifically, the other components include a positive electrode and a negative electrode capable of intercalating and releasing sodium, a current collector, a separator, an outer casing, etc.

[0046] [Positive electrode] The cathode material (cathode active material) is not particularly limited, but examples include NaCrO2, NaFe 0.5 Co 0.5 O2, NaFe 0.4 Mn 0.3 Ni 0.3 O2, NaNi 0.5 Ti 0.3 Mn 0.2 O2, NaNi 1 / 3 Ti 1 / 3 Mn 1 / 3 O2, NaNi 0.33 Ti 0.33 Mn 0.16 Mg 0.17 O2, Na 2 / 3 Ni 1 / 3 Ti 1 / 6 Mn 1 / 2 O2, Na 2 / 3 Ni 1 / 3 Mn 2 / 3Sodium-containing transition metal composite oxides such as O2, mixtures of multiple transition metals such as Co, Mn, and Ni in these sodium-containing transition metal composite oxides, and cases in which some of the transition metals in these sodium-containing transition metal composite oxides are substituted with other metals, polyanionic compounds such as NaFePO4, NaVPO4F, Na3V2(PO4)3, and Na2Fe2(SO4)3, and composition formula Na a M b [Fe(CN)6] c Sodium salts of Prussian blue analogs represented by (M = Cr, Mn, Fe, Co, Ni, Cu, or Zn, with 0 ≤ a ≤ 2, 0.5 ≤ b ≤ 1.5, 0.5 ≤ c ≤ 1.5), oxides such as TiO2, V2O5, and MoO3, sulfides such as TiS2 and FeS, or conductive polymers such as polyacetylene, poly(p-phenylene), polyaniline, and polypyrrole, activated carbon, radical-generating polymers, and carbon materials are used.

[0047] In the positive electrode, for example, a positive electrode active material layer is formed on at least one surface of the positive electrode current collector. The positive electrode active material layer is composed of, for example, the aforementioned positive electrode active material, a binder, and, if necessary, a conductive agent. Examples of binders include polytetrafluoroethylene, polyvinylidene fluoride, or styrene-butadiene rubber (SBR) resin. Examples of conductive agents include acetylene black, Ketjen black, carbon fiber, or carbon materials such as graphite (granular graphite or flake graphite), and it is preferable to use acetylene black or Ketjen black with low crystallinity.

[0048] [Negative electrode] The negative electrode material (negative electrode active material) is not particularly limited, but examples include sodium metal or materials capable of intercalating and deintercalating sodium ions. For example, sodium metal, alloys of sodium metal with other metals such as tin, intermetallic compounds, various carbon materials including hard carbon, metal oxides such as titanium oxide, metal nitrides, elemental tin, tin compounds, activated carbon, conductive polymers, etc. In addition to these, elemental phosphorus such as red phosphorus and black phosphorus, phosphorus compounds such as Co-P, Cu-P, Sn-P, Ge-P, and Mo-P, elemental antimony, antimony compounds such as Sb / C and Bi-Sb, etc. These negative electrode active materials may be used individually or in combination of two or more types.

[0049] In the negative electrode, for example, a negative electrode active material layer is formed 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, if necessary, a conductive agent. Examples of binders include polytetrafluoroethylene, polyvinylidene fluoride, or styrene-butadiene rubber (SBR) resin. Examples of conductive agents include acetylene black, Ketjen black, carbon fiber, or carbon materials such as graphite (granular graphite or flake graphite).

[0050] [Current collector] Copper, aluminum, stainless steel, nickel, titanium, or alloys thereof can be used for the positive and negative electrode current collectors. An active material layer is formed on at least one surface of the current collector.

[0051] [Separator] As separators to prevent contact between the positive and negative electrodes, nonwoven fabrics, porous sheets, or films made of polyolefins (e.g., polypropylene, polyethylene), paper, or glass fibers are used. These materials are preferably microporous so that the electrolyte can permeate and ions can easily pass through.

[0052] [Exterior] For the outer casing, for example, metal cans such as coin-shaped, cylindrical, or rectangular cans, or laminated outer casings can be used. Examples of metal can materials include nickel-plated steel sheets, stainless steel sheets, nickel-plated stainless steel sheets, aluminum or its alloys, nickel, titanium, etc. For the laminated outer casing, for example, aluminum laminate film, SUS laminate film, silica-coated laminate film made of polypropylene or polyethylene, etc. can be used.

[0053] 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 facing each other and a non-aqueous electrolyte are enclosed in an outer casing. Furthermore, the shape of the non-aqueous sodium-ion battery according to this embodiment is not particularly limited, but it can be coin-shaped, cylindrical, rectangular, or aluminum laminate sheet-shaped.

[0054] [Manufacturing method for non-aqueous sodium ion batteries] The present invention also relates to a method for manufacturing a non-aqueous sodium-ion battery. The aforementioned manufacturing method is The above-described step of preparing the electrolyte for a non-aqueous sodium ion battery according to this embodiment, A method for manufacturing a non-aqueous sodium ion battery, comprising the step of filling an empty cell, which is equipped with at least a positive electrode and a negative electrode, with the electrolyte for a non-aqueous sodium ion battery. [Examples]

[0055] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0056] [Electrolyte preparation] (Preparation of electrolyte solution No. 1-1) (I) Using propylene carbonate (also referred to as "PC") as a non-aqueous solvent, (II) NaPF6 as a sodium salt and (III) sodium fluorosulfate as a fluorosulfate were dissolved in the solvent in the amounts shown in Table 1 relative to the total volume of the electrolyte to prepare electrolyte No. 1-1. The above preparation was carried out while maintaining the liquid temperature in the range of 20 to 30°C.

[0057] [Table 1]

[0058] (Preparation of electrolytes No. 1-2 to 1-15) As shown in Table 1, various electrolytes were prepared in the same manner as electrolyte No. 1-1, except that the type and content of fluorosulfates were changed, diethylene glycol dimethyl ether (also referred to as "DG") was used as a non-aqueous solvent, and the content of NaPF6 was changed.

[0059] [Examples 1-1 to 1-10, Comparative Example 1-1] The electrolytes used for the test are those listed in Table 2, and the cathode material is NaNi 0.5 Ti 0.3 Mn 0.2 A test cell was fabricated using O2 and hard carbon (Carbotron P, manufactured by Kureha Corporation) as the anode material. High-temperature cycling tests were performed on the test cell, and the cycling characteristics and gas generation during the cycling test were evaluated. The evaluation results are shown in Table 2. The test cell was fabricated as follows.

[0060] The test positive electrode was prepared using the following procedure. NaNi as the positive electrode active material 0.5 Ti 0.3 Mn 0.2A slurry solution was prepared by mixing 90% by mass of O2, 5% by mass of acetylene black as a conductive agent, and 5% by mass of polyvinylidene fluoride (PVDF) as a binder. N-methylpyrrolidone was then added as a solvent in an amount of 50% by mass relative to the total mass of the positive electrode active material, conductive agent, and binder. This slurry solution was applied to an aluminum foil current collector, which served as the positive electrode current collector, and dried at 150°C for 12 hours to obtain a test positive electrode with a positive electrode active material layer formed on the current collector.

[0061] The test negative electrode was prepared using the following procedure. A slurry solution was prepared by mixing 90% by mass of hard carbon powder (Carbotron P, manufactured by Kureha Corporation) as the negative electrode active material with 10% by mass of polyvinylidene fluoride (PVDF) as a binder. N-methylpyrrolidone was then added as a solvent in an amount of 50% by mass relative to the total mass of the negative electrode active material and binder. This slurry solution was applied to an aluminum foil negative electrode current collector and dried at 150°C for 12 hours to obtain a test negative electrode with a negative electrode active material layer formed on the current collector.

[0062] A 50mAh test cell with an aluminum laminate casing was assembled by placing the test positive electrode and test negative electrode through a polyethylene separator soaked in test electrolyte.

[0063] [High-temperature cycle characteristics evaluation] For the test cell, at an ambient temperature of 25°C, with a maximum charge voltage of 4.1V and a minimum discharge voltage of 1.5V, the current density was measured using the constant current / constant voltage method at 0.32mA / cm². 2 After charging and discharging, a charge-discharge test was conducted at an ambient temperature of 60°C to evaluate the cycle characteristics. Charging was performed up to 4.1V, and discharging down to 1.5V, with a current density of 1.56mA / cm². 2The battery underwent repeated charge-discharge cycles. The degree of cell degradation was evaluated by the discharge capacity retention rate at 500 cycles in the charge-discharge test at an ambient temperature of 60°C. The "high-temperature cycle discharge capacity retention rate," expressed as the discharge capacity retention rate at 500 cycles, was calculated using the following formula. The discharge capacity at 1 cycle in the charge-discharge test at an ambient temperature of 60°C was used as the initial discharge capacity. High-temperature cycle retention rate (%) = (Discharge capacity at 500 cycles / Initial discharge capacity) × 100

[0064] [Gas generation amount evaluation] Before and after the high-temperature cycle characteristic evaluation described above, the cell volume 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) was measured. 3 The gas generation amount V was calculated as follows: (V = volume of the cell after high-temperature cycle characteristic evaluation V2 - volume of the cell before high-temperature cycle characteristic evaluation V1). Based on this gas generation amount V, the "gas generation amount during high-temperature cycling" was evaluated.

[0065] [Table 2]

[0066] In Table 2, the evaluation results for Examples 1-1 to 1-10 are relative values ​​with the evaluation result for Comparative Example 1-1 set to 100%. A higher value for "Discharge Capacity Maintenance Rate after High-Temperature Cycle" is desirable, while a lower value for "Gas Generation Amount during High-Temperature Cycle" is desirable.

[0067] From the evaluation results in Table 2, it was confirmed that the electrolyte of the example, which satisfies the solvent composition conditions described above (all test examples have a chain carbonate content of 0% by mass) and contains a predetermined amount of fluorosulfate, exhibits a greater effect in suppressing gas generation at high temperatures above 60°C compared to the electrolyte of Comparative Example 1-1 which does not contain fluorosulfate, and also shows superior high-temperature cycling characteristics. Furthermore, although the reason for its superior high-temperature cycling characteristics is not entirely clear, it is presumed that the film formed on the electrode by the fluorosulfate anion and the solvent is in an optimal state, and this electrode film remains stable even at high temperatures. This reduces the amount of Na ions taken up into the electrode film during charging and discharging, thus resulting in excellent high-temperature cycling characteristics. Furthermore, in Examples 1-2 to 1-8, it was confirmed that including a predetermined amount of fluorosulfate can further enhance the gas generation suppression effect and improve high-temperature cycle characteristics.

[0068] [Examples 1-11 to 1-13, Comparative Example 1-2] A test cell was prepared in the same manner as in Example 1-1, except that the electrolyte listed in Table 3 was used as the test electrolyte and NaCrO2 (positive electrode active material) was used as the positive electrode material. The cycle characteristics and gas generation amount during the cycle test were evaluated in the same manner as in Example 1-1, except that the upper limit charging voltage in the high-temperature cycle characteristic evaluation was changed to 3.3V. The evaluation results are shown in Table 3.

[0069] [Table 3]

[0070] In Table 3, the evaluation results for Examples 1-11 to 1-13 are relative values, with the evaluation result for Comparative Example 1-2 set to 100%.

[0071] From the evaluation results in Table 3, it was confirmed that, similar to the case where PC was used as the non-aqueous solvent, even when DG was used as the non-aqueous solvent (in all test examples, the content of linear carbonate was 0% by mass), the electrolyte of the example containing a predetermined amount of fluorosulfate was able to suppress gas generation at high temperatures of 60°C or higher compared to the electrolyte of Comparative Examples 1-2 which did not contain fluorosulfate, and furthermore, it exhibited superior high-temperature cycling characteristics. Furthermore, the evaluation results in Table 3 confirm that by including a predetermined amount of fluorosulfate, it is possible to achieve even better gas generation suppression and improved high-temperature cycle characteristics.

[0072] [Preparation of electrolyte containing chain-like carbonate solvent] (Preparation of electrolytes No. 2-1 to 2-6, No. 3-1 to 3-6, No. 4-1 to 4-6, No. 5-1 to 5-6, No. 6-1 to 6-6, No. 7-1 to 7-6, and No. 8-1 to 8-6) As shown in Table 4, various electrolytes were prepared by (I) using PC and dimethyl carbonate (also referred to as "DMC") as non-aqueous solvents in the mass ratios shown in Table 4, (II) NaPF6 as the sodium salt, and (III) sodium fluorosulfate as the fluorosulfate, in the amounts shown in Table 4 relative to the total volume of the electrolyte.

[0073] [Table 4]

[0074] [Examples 2-1 to 2-5, Comparative Example 2-1, Examples 3-1 to 3-5, Comparative Example 3-1, Examples 4-1 to 4-5, Comparative Example 4-1, Examples 5-1 to 5-5, Comparative Example 5-1, Examples 6-1 to 6-5, Comparative Example 6-1, Comparative Examples 7-1 to 7-6, and Comparative Examples 8-1 to 8-6] A test cell was prepared in the same manner as in Example 1-1, except that the electrolyte listed in Table 5 was used as the test electrolyte. The cycle characteristics and gas generation amount during the cycle test were evaluated in the same manner as in Example 1-1. The evaluation results are shown in Table 5.

[0075] [Table 5]

[0076] The evaluation results for the examples and comparative examples listed in Table 5 are relative values, with the evaluation result of Comparative Example 2-1 set to 100%.

[0077] From the evaluation results in Table 5, (I) even if the non-aqueous solvent contains a chain carbonate, as long as the above solvent composition conditions are met, the electrolyte of the example containing a predetermined amount of fluorosulfate can exhibit a gas generation suppression effect at high temperatures of 60°C or higher compared to the electrolyte of the comparative example that does not contain fluorosulfate in each solvent system, and furthermore, it has excellent high-temperature cycling characteristics. In Comparative Examples 7-1 to 7-6 (with a chain-like carbonate content of 80% by mass) and 8-1 to 8-6 (with a chain-like carbonate content of 100% by mass), which did not meet the solvent composition conditions, it was found that gas generation at high temperatures could not be suppressed regardless of the fluorosulfate content. Furthermore, the evaluation results in Table 5 confirmed that by including a predetermined amount of fluorosulfate, even better gas generation suppression and high-temperature cycle characteristics can be achieved.

[0078] [Dependence of gas generation on the amount of linear carbonate] Figure 1 shows a plot of the amount of gas generated during high-temperature cycling (relative value with Comparative Example 2-1 set to 100%) against the chain carbonate content in (I) for the examples and comparative examples listed in Table 5. From this plot, it was confirmed that the electrolyte satisfying the solvent composition conditions described above can significantly suppress the amount of gas generated at high temperatures of 60°C or higher. It was also confirmed that this trend can be maintained by including (III) fluorosulfate in the predetermined content range specified in this disclosure.

[0079] (Preparation of electrolyte solutions No. 9-1 to 9-6) As shown in Table 6, (I) a mixed solvent was used as a non-aqueous solvent, consisting of ethylene carbonate (hereinafter also referred to as "EC"), ethyl methyl carbonate (hereinafter also referred to as "EMC"), and diethyl carbonate (hereinafter also referred to as "DEC"), mixed in a mass ratio of EC:EMC:DEC = 40:30:30. (II) NaPF6 was used as the sodium salt, and (III) sodium fluorosulfate was used as the fluorosulfate, dissolved in the amounts shown in Table 6 relative to the total volume of the electrolyte. Various electrolytes were prepared by dissolving these in the amounts shown in Table 6. The above preparations were carried out while maintaining the liquid temperature in the range of 20 to 30°C.

[0080] [Table 6]

[0081] [Examples 9-1 to 9-5, Comparative Example 9-1] A test cell was prepared in the same manner as in Example 1-1, except that the electrolyte listed in Table 7 was used as the test electrolyte. The cycle characteristics and gas generation amount during the cycle test were evaluated in the same manner as in Example 1-1. The evaluation results are shown in Table 7.

[0082] [Table 7]

[0083] In Table 7, the evaluation results for Examples 9-1 to 9-5 are relative values ​​with the evaluation result for Comparative Example 9-1 set to 100%.

[0084] From the evaluation results in Table 7, it was confirmed that (I) even when the non-aqueous solvent contained asymmetric chain carbonates (in all test examples, the total content of chain carbonates was 60% by mass), the electrolyte of the example containing a predetermined amount of fluorosulfate was able to suppress gas generation at high temperatures of 60°C or higher compared to the electrolyte of Comparative Example 9-1 which did not contain fluorosulfate, and also exhibited superior high-temperature cycling characteristics. Furthermore, in Examples 9-2 to 9-5, it was confirmed that including a predetermined amount of fluorosulfate can further enhance the gas generation suppression effect and improve high-temperature cycle characteristics.

[0085] [Preparation of electrolyte containing other additives] (Preparation of electrolytes No. 10-1 to 10-8 and No. 11-1 to 11-8) (I) As a non-aqueous solvent, a mixed solvent was used, consisting of PC, EC, and EMC in a mass ratio of PC:EC:EMC = 30:20:50. (II) NaPF6 as a sodium salt, (III) sodium fluorosulfate as a fluorosulfate, and NaPF4(C2O4) as other additives were dissolved in the amounts shown in Table 8 relative to the total volume of the electrolyte to prepare electrolyte No. 10-1. The above preparation was carried out while maintaining the liquid temperature in the range of 20 to 30°C. Furthermore, the various electrolytes listed in Table 8 were prepared in the same manner as electrolyte No. 10-1, except that the types and amounts of other additives were changed to those listed in Table 8, and the amount of fluorosulfate was altered. The abbreviations in Table 8 are as follows: VC: Vinylen carbonate FEC: Fluoroethylene carbonate TMSB: Tris(trimethylsilyl)borate DTD: 1,3,2-dioxathiolan-2,2-dioxide

[0086] [Table 8]

[0087] [Examples 10-1 to 10-8, Comparative Examples 10-1 to 10-8] A test cell was prepared in the same manner as in Example 1-1, except that the electrolyte listed in Table 9 was used as the test electrolyte. The cycle characteristics and gas generation amount during the cycle test were evaluated in the same manner as in Example 1-1. The evaluation results are shown in Table 9.

[0088] [Table 9]

[0089] In Table 9, the evaluation results for Examples 10-1 to 10-8 are relative values, with the evaluation results for Comparative Examples 10-1 to 10-8 set to 100%.

[0090] From the evaluation results in Table 9, it was confirmed that even with electrolyte compositions containing other additives, the electrolytes of the examples that satisfy the above-mentioned solvent composition conditions (all test examples contain 50% by mass of linear carbonate) and contain a predetermined amount of fluorosulfate exhibit a greater effect in suppressing gas generation at high temperatures above 60°C compared to the electrolytes of the corresponding comparative examples that do not contain fluorosulfate, and also exhibit superior high-temperature cycling characteristics.

[0091] Table 10 also shows the evaluation results for Examples 10-1 to 10-8, expressed as relative values ​​with the evaluation results of Example 10-0 set to 100%, in which cells were prepared in the same manner as in Example 1-1 and the same performance evaluation was conducted, except that electrolyte No. 10-0 from Table 8 was used as the non-aqueous electrolyte.

[0092] [Table 10]

[0093] The evaluation results in Table 10 confirm that by further incorporating other additives into the electrolyte composition, the gas generation suppression effect and / or the high-temperature cycle characteristics improvement effect can be further enhanced. [Industrial applicability]

[0094] The embodiments of this disclosure provide an electrolyte for non-aqueous sodium-ion batteries that exhibits excellent gas generation suppression effects at high temperatures of 60°C or higher when used in non-aqueous sodium-ion batteries, a non-aqueous sodium-ion battery using the same, and a method for manufacturing the same.

[0095] Although this disclosure 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 this disclosure. This application is based on Japanese Patent Application No. 2021-082005 filed on May 13, 2021, the contents of which are incorporated herein by reference.

Claims

1. (I) Non-aqueous solvent, (II) Sodium salts, and (III) Fluorosulfates Includes, The content of (III) is 0.05% by mass to 10.00% by mass relative to the total amount of electrolyte for non-aqueous sodium ion batteries. The content of linear carbonate relative to the total amount of (I) is 0% by mass or more and less than 1% by mass. Electrolyte for non-aqueous sodium-ion batteries.

2. The electrolyte for a non-aqueous sodium-ion battery according to claim 1, wherein the content of (III) is 0.15% by mass to 8.00% by mass with respect to the total amount of the electrolyte for a non-aqueous sodium-ion battery.

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

4. The electrolyte for a non-aqueous sodium-ion battery according to claim 1, wherein (I) comprises at least one selected from the group consisting of cyclic esters, linear esters other than linear carbonates, cyclic ethers, and linear ethers.

5. The above (I) includes a cyclic ester, The electrolyte for a non-aqueous sodium-ion battery according to claim 4, wherein the cyclic ester is a cyclic carbonate.

6. The electrolyte for a non-aqueous sodium-ion battery according to claim 4, wherein (I) comprises at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, ethyl propionate, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

7. The electrolyte for a non-aqueous sodium-ion battery according to any one of claims 1 to 6, wherein the chain-like carbonate is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl-2,2,2-trifluoroethyl carbonate, ethyl-2,2,2-trifluoroethyl carbonate, methyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate, and ethyl-1,1,1,3,3,3-hexafluoroisopropyl carbonate.

8. where (II) is NaPF ６ , NaBF ４ , NaBF ２ (C ２ O ４ ), NaPF ４ (C ２ O ４ ), NaPF ２ (C ２ O ４ ) ２ , NaSbF ６ , NaAsF ６ , NaClO ４ , NaN(SO ２ F) ２ , NaN(SO ２ CF ３ ) ２ , NaN(SO ２ F)(SO ２ CF ３ ), NaN(C ａ F ２ａ＋１ SO ２ )(C ｂ F ２ｂ＋１ SO ２ ) (where a and b are integers satisfying 2 ≤ a ≤ 20 and 2 ≤ b ≤ 20.), NaSO ３ CF ３ , NaSO ３ C ４ F ９ , NaN(POF ２ ) ２ , NaN(POF ２ )(SO ２ F), NaPO ２ F ２ , NaC(SO ２ CF ３ ) ３ , NaPF ３ (C ３ F ７ ) ３ , NaB(CF ３ ) ４ , NaBF ３ (C ２ F ５ ), NaAlO ２ , NaAlCl ４ An electrolyte for a non-aqueous sodium ion battery according to any one of claims 1 to 6, wherein at least one selected from the group consisting of , NaCl, and NaI.

9. As (II) above, NaPF ６ An electrolyte for a non-aqueous sodium-ion battery according to any one of claims 1 to 6, comprising:

10. 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 6.

11. A method for manufacturing a non-aqueous sodium ion battery, comprising the steps of preparing an electrolyte for a non-aqueous sodium ion battery according to any one of claims 1 to 6, and filling an empty cell equipped with at least a positive electrode and a negative electrode with the electrolyte for a non-aqueous sodium ion battery.

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