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

Abstract

Cycle characteristics of non-aqueous sodium-ion batteries at temperatures above 60°C, high-temperature cycle The amount of gas generated during the test (and its suppression effect) and the high-temperature storage characteristics are improved. Electrolyte for non-aqueous sodium ion batteries, non-aqueous sodium ion battery using the same, and This invention provides a method for manufacturing a non-aqueous sodium-ion battery. [Solution] (I) Fluorosulfate, (II) Chemicals represented by specific general formulas (1) to (9) Compound, vinylene carbonate, tris(trimethylsilyl)borate, and tristrimeth (III) sodium, selected from the group consisting of thylsilyl phosphates Electrolyte for non-aqueous sodium ion batteries containing salt and (IV) a non-aqueous solvent, non-aqueous sodium A method for manufacturing an ON battery and a 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 a non-aqueous sodium-ion battery. [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 non-aqueous sodium-ion batteries, it has been proposed to suppress degradation caused by the decomposition of the electrolyte on the surface of the active positive and negative electrodes using various additives. For example, Patent Document 2 discloses a non-aqueous electrolyte for sodium secondary batteries that improves charge-discharge cycle characteristics by containing compounds having a -(S=O)- bond, such as sulfonic acid ester compounds (e.g., methylenebis(benzenesulfonate, methylenebis(2-trifluoromethylbenzenesulfonate), methylbenzenesulfonate)) and sulfoxide compounds (e.g., dimethyl sulfoxide).

[0004] On the other hand, Patent Documents 3 and 4 describe 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]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2013-48077 [Patent Document 2] Japanese Patent Publication No. 2016-181467 [Patent Document 3] Japanese Patent Application Publication No. 2011-187440 [Patent Document 4] International Publication No. 2018 / 179884 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Although non-aqueous sodium-ion batteries are already beginning to be put into practical use, our research has shown that there is room for improvement in terms of cycle characteristics, gas generation (suppression effect) during high-temperature cycle testing, and high-temperature storage characteristics, especially for applications such as automobiles where batteries are used for long periods in high-temperature environments. Therefore, one of the embodiments of this disclosure aims to provide an electrolyte for a non-aqueous sodium-ion battery that can improve at least one of the following: the cycle characteristics of a non-aqueous sodium-ion battery at high temperatures of 60°C or higher, the amount of gas generated during high-temperature cycle testing (and its suppression effect), and the high-temperature storage characteristics; a non-aqueous sodium-ion battery using the same; and a method for manufacturing a non-aqueous sodium-ion battery. [Means for solving the problem]

[0007] In view of the above problems, the present inventors have conducted diligent studies and have found that an electrolyte for a non-aqueous sodium-ion battery can be obtained that improves at least one of the following characteristics of a non-aqueous sodium-ion battery: the cycle characteristics at high temperatures of 60°C or higher, the amount of gas generated during high-temperature cycle testing (and its suppression effect), and the high-temperature storage characteristics, by comprising (I) a fluorosulfate, (II) at least one compound selected from the group consisting of compounds represented by the following general formulas (1) to (9), vinylene carbonate, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate, (III) a sodium salt, and (IV) a non-aqueous solvent. This leads to the completion of this disclosure.

[0008] In other words, this disclosure includes the following embodiments. <1> (I) Fluorosulfates, (II) Compounds represented by the following general formula (5), (III) sodium salts, and (IV) Non-aqueous solvents An electrolyte for non-aqueous sodium ion batteries, comprising: The content x of (I) above is 0.001% by mass ≤ x ≤ 10.5% by mass relative to the total amount of electrolyte for non-aqueous sodium ion batteries. An electrolyte for a non-aqueous sodium-ion battery, wherein the content y of (II) above is 0.1% by mass ≤ y ≤ 6.0% by mass relative to the total amount of electrolyte for a non-aqueous sodium-ion battery. [ka] [In general formula (5), X 5 ~X 6 Each of these is independently a fluorine atom or CF3. Furthermore, general formula (5) contains at least one SF bond. In general formula (5), M 6 This is a sodium ion. <2> The content x of (I) above is 0.008% by mass ≤ x ≤ 7.5% 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 content y of (II) above is 0.1% by mass ≤ y ≤ 5.0% 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. <4> The non-aqueous solvent includes at least one selected from the group consisting of cyclic esters, linear esters, cyclic ethers, and linear ethers. <1> ~ <3> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <5> The aforementioned sodium salts are NaPF6, NaBF4, NaSbF6, NaAsF6, NaClO4, NaN(SO2CF3)2, NaN(C a F 2a+1 SO2)(Cb F 2b+1 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, NaC(SO2CF3)3, NaPF3(C3F7)3, NaB(CF3)4, NaBF3(C2F5), NaAlO2, NaAlCl4, NaCl, and NaI. <1> ~ <3> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <6> The concentration z in (III) above is 0.3 mol / L ≤ z ≤ 5.0 mol / L relative to the total amount of electrolyte for the non-aqueous sodium ion battery. <1> ~ <3> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <7> Furthermore, oligomers of cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate (number average molecular weight 170-5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynylethylene carbonate, trans-difluoroethylene carbonate, 1,3,2-dioxathiolan-2,2-dioxide, and 4-propyl-1,3,2-dioxathiolan-2,2-dioxide are also included. It contains at least one compound selected from the group consisting of thiolane-2,2-dioxide, methylene methane disulfonate, 1,2-ethane disulfonic anhydride, 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. <1> ~ <3> Electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <8> At least a positive electrode and a negative electrode, <1> ~ <3> A non-aqueous sodium-ion battery comprising an electrolyte for non-aqueous sodium-ion batteries as described in any one of the items. <9> <1> ~ <3> A step of preparing an electrolyte for a non-aqueous sodium ion battery as described in any one of the items, A method for manufacturing a non-aqueous sodium ion battery, comprising a step of filling an empty cell having at least a positive electrode and a negative electrode with the electrolyte for the non-aqueous sodium ion battery. This disclosure relates to the aspects according to <1> to <9> above, and hereinafter, other matters (for example, the following [1] to

[19] ) are also described.

[0009] [1] (I) Fluorosulfate (II) At least one selected from the group consisting of compounds represented by the following general formulas (1) to (9), vinylene carbonate, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate (III) Sodium salt, and (IV) An electrolyte for a non-aqueous sodium ion battery containing a non-aqueous solvent.

[0010]

Chemical formula

[0011] [In general formula (1), M represents a boron atom or a phosphorus atom, m is an integer of 1 to 3, n is an integer of 0 to 4, and p is 0 or 1. R 1 represents an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups may contain a substituent or a hetero atom in their structure). Also, when p is 1 and m is 2 or more, m R 1 may be bonded to each other. When p is 0, R 1 does not exist and it becomes a single bond. R 2 represents a halogen atom, and X 1 , X 2 each independently represents an oxygen atom or a sulfur atom, and X 3 represents a carbon atom or a sulfur atom. q is 1 when X 3 is a carbon atom, and q is 1 or 2 when X 3 is a sulfur atom. Aa+ represents an alkali metal cation, alkaline earth metal cation, or onium cation, and 'a' represents the valency of the cation. a to d are each independently either 1 or 2, and satisfy the condition a × b = c × d.

[0012] [ka]

[0013] [In general formulas (2) to (3), (6) and (7), R 3 ~R 12 Each of these is independently a fluorine atom, or an organic group selected from the group consisting of an alkoxy group having 1 to 10 carbon atoms, an alkenyloxy group having 2 to 10 carbon atoms, an alkynyloxy group having 2 to 10 carbon atoms, a cycloalkoxy group having 3 to 10 carbon atoms, a cycloalkenyloxy group having 3 to 10 carbon atoms, and an aryloxy group having 6 to 10 carbon atoms, and a fluorine atom, an oxygen atom, or an unsaturated bond may be present in the organic group. In general formula (4), X 4 This represents a fluorine atom. In general formulas (5) and (7), X 5 ~X 7 Each of these is independently a fluorine atom, or an organic group selected from the group consisting of a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, a C3-C10 cycloalkyl group, a C3-C10 cycloalkenyl group, a C6-C10 aryl group, a C1-C10 alkoxy group, a C2-C10 alkenyloxy group, a C2-C10 alkynyloxy group, a C3-C10 cycloalkoxy group, a C3-C10 cycloalkenyloxy group, and a C6-C10 aryloxy group, and a fluorine atom, an oxygen atom, or an unsaturated bond may be present in the organic group. Furthermore, each of the general formulas (2) to (7) contains at least one PF bond and / or SF bond. In general formulas (2) to (7), M 2 ~M 8These are, independently, a proton, a metal cation, or an onium cation.

[0014] [ka]

[0015] [In general formula (8), R 13 ~R 16 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms. 2 [This is an integer between 1 and 3.]

[0016] [ka]

[0017] [In general formula (9), R 17 ~R 22 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms. 3 [This is an integer between 0 and 2.]

[0018] [2] The electrolyte for a non-aqueous sodium-ion battery according to [1], wherein the content x of (I) is 0.008% by mass ≤ x ≤ 7.5% by mass relative 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 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.

[0019] [4] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [3], wherein the content y of (II) above is 0.1% by mass ≤ y ≤ 5.0% by mass relative to the total amount of the electrolyte for a non-aqueous sodium-ion battery.

[0020] [5] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [4], wherein the compound represented by the above general formula (1) is at least one selected from the group consisting of NaBF2(C2O4), NaPF4(C2O4), NaPF2(C2O4)2, and NaP(C2O4)3.

[0021] [6] The compound represented by the above general formula (2) is R 3 and R 4 However, each is independently a fluorine atom, a methoxy group, an ethoxy group, or a propargyloxy group. M 2 However, these are lithium ions, sodium ions, potassium ions, or tetraalkylammonium ions. An electrolyte for a non-aqueous sodium-ion battery, comprising at least one compound selected from the group consisting of compounds, as described in any one of items [1] to [5].

[0022] [7] The compound represented by the above general formula (3) is R 5 and R 6 However, each is independently a fluorine atom, a methoxy group, or an ethoxy group, M 3 However, these are lithium ions, sodium ions, potassium ions, or tetraalkylammonium ions. An electrolyte for a non-aqueous sodium-ion battery, comprising at least one compound selected from the group consisting of compounds, as described in any one of items [1] to [6].

[0023] [8] The compound represented by the above general formula (4) is M 4 and M 5 However, each is independently a lithium ion, a sodium ion, a potassium ion, or a tetraalkylammonium ion. An electrolyte for a non-aqueous sodium-ion battery, comprising at least one compound selected from the group consisting of compounds, as described in any one of items [1] to [7].

[0024] [9] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [8], wherein the compound represented by the above general formula (5) is at least one selected from the group consisting of LiN(SO2F)2, LiN(SO2F)(SO2CF3), NaN(SO2F)2, NaN(SO2F)(SO2CF3), KN(SO2F)2, and KN(SO2F)(SO2CF3).

[0025]

[10] The electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to [9], wherein the compound represented by the above general formula (6) is at least one selected from the group consisting of LiN(POF2)2, LiN(POF2)(PO(OCH3)2), NaN(POF2)2, NaN(POF2)(PO(OCH3)2), KN(POF2)2, and KN(POF2)(PO(OCH3)2).

[0026]

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

[10] , wherein the compound represented by the above general formula (7) is at least one selected from the group consisting of LiN(POF2)(SO2F), LiN(PO(OCH3)2)(SO2F), NaN(POF2)(SO2F), NaN(PO(OCH3)2)(SO2F), KN(POF2)(SO2F), and KN(PO(OCH3)2)(SO2F).

[0027]

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

[11] , wherein the compound represented by the above general formula (8) is at least one selected from the group consisting of 1,3-propensulone, 1,4-butensulone, and 2-methyl-1,3-propensulone.

[0028]

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

[12] , wherein the compound represented by the above general formula (9) is at least one selected from the group consisting of 1,3-propanesultone, 1,4-butanesultone, 1-methyl-1,3-propanesultone, and 3-methyl-1,3-propanesultone.

[0029]

[14] The electrolyte for a nonaqueous sodium-ion battery according to any one of [1] to

[13] , comprising at least one selected from the group consisting of cyclic esters, linear esters, cyclic ethers, and linear ethers as the nonaqueous solvent.

[0030]

[15] The aforementioned sodium salts are 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

[14] , 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.

[0031]

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

[15] , wherein the concentration z of (III) is 0.3 mol / L ≤ z ≤ 5.0 mol / L relative to the total amount of electrolyte for a non-aqueous sodium-ion battery.

[0032]

[17] Furthermore, oligomers of cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate (number average molecular weight 170-5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynylethylene carbonate, trans-difluoroethylene carbonate, 1,3,2-dioxathiolan-2,2-dioxide, 4-propyl-1,3,2-dioxathiolan-2,2-dioxide, methyl An electrolyte for a non-aqueous sodium-ion battery according to any one of [1] to

[16] , comprising at least one compound selected from the group consisting of methanedisulfonate, 1,2-ethanedisulfonic anhydride, 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.

[0033]

[18] 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

[17] .

[0034]

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

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

[0035] Embodiments of this disclosure provide an electrolyte for a non-aqueous sodium-ion battery that can improve at least one of the following: the cycle characteristics of a non-aqueous sodium-ion battery at high temperatures of 60°C or higher, the amount of gas generated during high-temperature cycle testing (and its suppression effect), and the high-temperature storage characteristics; a non-aqueous sodium-ion battery using the same; and a method for manufacturing a non-aqueous sodium-ion battery. [Brief explanation of the drawing]

[0036] [Figure 1] This figure shows the evaluation results for the discharge capacity retention rate after high-temperature cycling for Example 1-1, Comparative Example 1-0, and 1-1 to 1-2. [Figure 2] This figure shows the evaluation results for the amount of gas generated during high-temperature cycling in Example 1-1, Comparative Example 1-0, and 1-1 to 1-2. [Figure 3] This figure shows the evaluation results for the recovery discharge capacity retention rate after high-temperature storage in Example 1-1, Comparative Example 1-0, and 1-1 to 1-2. [Modes for carrying out the invention]

[0037] The embodiments of this disclosure will be described below. However, this disclosure can be implemented in various forms 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.

[0038] In this specification, "~" is used to mean that the numbers written before and after it include the lower and upper limits, respectively.

[0039] [1. Electrolyte for non-aqueous sodium-ion batteries] The electrolyte for a non-aqueous sodium ion battery according to one embodiment of the present disclosure is: (I) Fluorosulfates (hereinafter sometimes referred to as "Component (I)" or simply "(I)") (II) At least one compound selected from the group consisting of compounds represented by the following general formulas (1) to (9), vinylene carbonate, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate (hereinafter referred to as "component (II)" or simply "(II)"), (III) Sodium salt (hereinafter referred to as "component (III)" or simply "(III)"), and (IV) Contains a non-aqueous solvent (hereinafter sometimes referred to as "component (IV)" or simply "(IV)").

[0040] [ka]

[0041] [In general formula (1), M represents a boron atom or a phosphorus atom, m is an integer from 1 to 3, n is an integer from 0 to 4, and p is 0 or 1. R 1 R represents an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups may contain substituents or heteroatoms in their structure). Also, if p is 1 and m is 2 or more, then m R 1 Each of them may be connected to the others. Note that if p is 0, R 1 It does not exist and is a single bond. R 2 X represents a halogen atom. 1 , X 2 Each of these independently represents either an oxygen atom or a sulfur atom, and X 3 represents a carbon atom or a sulfur atom. q is X 3 If it is a carbon atom, it is 1, X 3 If it is a sulfur atom, the result is 1 or 2. A a+ represents an alkali metal cation, alkaline earth metal cation, or onium cation, and 'a' represents the valency of the cation. a to d are each independently either 1 or 2, and satisfy the condition a × b = c × d.

[0042] [ka]

[0043] [In general formulas (2) to (3), (6) and (7), R 3 ~R 12 Each of these is independently a fluorine atom, or an organic group selected from the group consisting of an alkoxy group having 1 to 10 carbon atoms, an alkenyloxy group having 2 to 10 carbon atoms, an alkynyloxy group having 2 to 10 carbon atoms, a cycloalkoxy group having 3 to 10 carbon atoms, a cycloalkenyloxy group having 3 to 10 carbon atoms, and an aryloxy group having 6 to 10 carbon atoms, and a fluorine atom, an oxygen atom, or an unsaturated bond may be present in the organic group. In general formula (4), X 4 This represents a fluorine atom. In general formulas (5) and (7), X 5 ~X 7 Each of these is independently a fluorine atom, or an organic group selected from the group consisting of a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, a C3-C10 cycloalkyl group, a C3-C10 cycloalkenyl group, a C6-C10 aryl group, a C1-C10 alkoxy group, a C2-C10 alkenyloxy group, a C2-C10 alkynyloxy group, a C3-C10 cycloalkoxy group, a C3-C10 cycloalkenyloxy group, and a C6-C10 aryloxy group, and a fluorine atom, an oxygen atom, or an unsaturated bond may be present in the organic group. Furthermore, each of the general formulas (2) to (7) contains at least one PF bond and / or SF bond. In general formulas (2) to (7), M 2 ~M 8 These are, independently, a proton, a metal cation, or an onium cation.

[0044] [ka]

[0045] [In general formula (8), R 13 ~R 16 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms. 2[This is an integer between 1 and 3.]

[0046] [ka]

[0047] [In general formula (9), R 17 ~R 22 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms. 3 [This is an integer between 0 and 2.] Furthermore, if necessary, other commonly known additives can be used in combination.

[0048] The electrolyte for non-aqueous sodium-ion batteries according to this embodiment, with the above configuration, can improve at least one of the following: cycle characteristics at high temperatures of 60°C or higher, gas generation (suppression effect) during high-temperature cycle testing, and high-temperature storage characteristics. Although the details of this mechanism are not clear, it is presumed that the inclusion of component (II) together with fluorosulfate allows for the formation of a good film on the electrode.

[0049] The components of the electrolyte for the non-aqueous sodium-ion battery according to this embodiment will be described in detail below.

[0050] [(I) Fluorosulfates] 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.

[0051] 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. 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. 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.

[0052] The fluorosulfate is not particularly limited, but NaSO3F, LiSO3F, TEMASO3F, SBPSO3F, or TEASO3F are preferred, and NaSO3F, LiSO3F, or TEASO3F are particularly preferred. Here, TEA represents tetraethylammonium, TEMA represents triethylmethylammonium, and SBP represents 5-azoniaspirononane.

[0053] The fluorosulfate content x 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 1.5% by mass or more, relative to the total amount of electrolyte for the non-aqueous sodium-ion battery. Furthermore, the fluorosulfate content is not particularly limited, but 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 the non-aqueous sodium-ion battery. If it is 0.001% by mass or more, at least one of the following can be improved: the cycle characteristics of the non-aqueous sodium-ion battery at high temperatures of 60°C or higher, the amount of gas generated during high-temperature cycle testing (suppression effect), and the high-temperature storage characteristics. Furthermore, if it is 11.5% by mass or less, the film formed on the electrodes does not become too thick, which is less likely to lead to an increase in resistance. 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 fluorosulfate content x is preferably 0.008% by mass ≤ x ≤ 11.5% by mass, more preferably 0.008% by mass ≤ x ≤ 10.5% by mass, even more preferably 0.008% by mass ≤ x ≤ 7.5% by mass, and particularly preferably 1.5% by mass ≤ x ≤ 5.5% by mass, relative to the total amount of electrolyte for the non-aqueous sodium-ion battery.

[0054] [(II) At least one compound selected from the group consisting of compounds represented by general formulas (1) to (9), vinylene carbonate, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphate] The following describes component (II). The compounds represented by general formulas (1) to (9) are shown below.

[0055] [ka]

[0056] [In general formula (1), M represents a boron atom or a phosphorus atom, m is an integer from 1 to 3, n is an integer from 0 to 4, and p is 0 or 1. R 1 R represents an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (these groups may contain substituents or heteroatoms in their structure). Also, if p is 1 and m is 2 or more, then m R 1 Each of them may be connected to the others. Note that if p is 0, R 1 It does not exist and is a single bond. R 2 X represents a halogen atom. 1 , X 2 Each of these independently represents either an oxygen atom or a sulfur atom, and X 3 represents a carbon atom or a sulfur atom. q is X 3 If it is a carbon atom, it is 1, X 3 If it is a sulfur atom, the result is 1 or 2. A a+ represents an alkali metal cation, alkaline earth metal cation, or onium cation, and 'a' represents the valency of the cation. a to d are each independently either 1 or 2, and satisfy the condition a × b = c × d.

[0057] [ka]

[0058] [In general formulas (2) to (3), (6) and (7), R 3 ~R 12 Each of these is independently a fluorine atom, or an organic group selected from the group consisting of an alkoxy group having 1 to 10 carbon atoms, an alkenyloxy group having 2 to 10 carbon atoms, an alkynyloxy group having 2 to 10 carbon atoms, a cycloalkoxy group having 3 to 10 carbon atoms, a cycloalkenyloxy group having 3 to 10 carbon atoms, and an aryloxy group having 6 to 10 carbon atoms, and a fluorine atom, an oxygen atom, or an unsaturated bond may be present in the organic group. In general formula (4), X 4 This represents a fluorine atom. In general formulas (5) and (7), X 5 ~X 7 Each of these is independently a fluorine atom, or an organic group selected from the group consisting of a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, a C3-C10 cycloalkyl group, a C3-C10 cycloalkenyl group, a C6-C10 aryl group, a C1-C10 alkoxy group, a C2-C10 alkenyloxy group, a C2-C10 alkynyloxy group, a C3-C10 cycloalkoxy group, a C3-C10 cycloalkenyloxy group, and a C6-C10 aryloxy group, and a fluorine atom, an oxygen atom, or an unsaturated bond may be present in the organic group. Furthermore, each of the general formulas (2) to (7) contains at least one PF bond and / or SF bond. In general formulas (2) to (7), M 2 ~M 8 These are, independently, a proton, a metal cation, or an onium cation.

[0059] [ka]

[0060] [In general formula (8), R 13 ~R 16 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms. 2 [This is an integer between 1 and 3.]

[0061] [ka]

[0062] [In general formula (9), R 17 ~R 22 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms.3 is an integer from 0 to 2.

[0063] R 1 When R represents an alkylene group having 1 to 10 carbon atoms, the alkylene group having 1 to 10 carbon atoms is not particularly limited, and may be linear or branched. An alkylene group having 1 to 6 carbon atoms is preferred, and an alkylene group having 1 to 2 carbon atoms is more preferred. R 1 When R represents a halogenated alkylene group having 1 to 10 carbon atoms, the halogenated alkylene group having 1 to 10 carbon atoms is not particularly limited, and may be linear or branched. A halogenated alkylene group having 1 to 6 carbon atoms is preferred, and a halogenated alkylene group having 1 to 2 carbon atoms is more preferred. The "halogenated alkylene group" is a group in which some or all of the hydrogen atoms of the alkylene group are substituted with halogen atoms. Examples of the halogen atom in the halogenated alkylene group having 1 to 10 carbon atoms include a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

[0064] R 1 When R represents an arylene group having 6 to 20 carbon atoms, the arylene group having 6 to 20 carbon atoms is not particularly limited, and may be monocyclic or polycyclic. An arylene group having 6 to 15 carbon atoms is preferred, and an arylene group having 6 to 10 carbon atoms is more preferred. R 1 When R represents a halogenated arylene group having 6 to 20 carbon atoms, the halogenated arylene group having 6 to 20 carbon atoms is not particularly limited, and may be monocyclic or polycyclic. A halogenated arylene group having 6 to 15 carbon atoms is preferred, and a halogenated arylene group having 6 to 10 carbon atoms is more preferred. The "halogenated arylene group" is a group in which some or all of the hydrogen atoms of the arylene group are substituted with halogen atoms. Examples of the halogen atom in the halogenated arylene group having 6 to 20 carbon atoms include a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. The above groups may contain substituents in their structures or may contain heteroatoms. That p is 0 is cited as a preferred embodiment.

[0065] R 2 Examples of the halogen atom of R include a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. A a+ When A represents an alkali metal cation, the alkali metal cation is not particularly limited, and examples thereof include a lithium ion, a sodium ion or a potassium ion. A a+ When A represents an alkaline earth metal cation, the alkaline earth metal cation is not particularly limited, and examples thereof include a magnesium ion or a calcium ion. A a+ When A represents an onium cation, the onium cation is not particularly limited, and examples thereof include a tetraalkylammonium ion, a tetraalkylphosphonium ion, an imidazolium ion, an ammonium ion having a spiro skeleton, etc. The number of carbon atoms of the alkyl group in the tetraalkylammonium ion is preferably 1 to 6, and the number of carbon atoms of the alkyl group in 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-azoniaspiro[4.4]nonane. a to d are each independently 1 or 2, and satisfy a×b = c×d. As a preferred embodiment, it is cited that a to d are 1.

[0066] R 3 ~R 12 When R~R each independently represent an alkoxy group having 1 to 10 carbon atoms as an organic group, the alkoxy group having 1 to 10 carbon atoms is not particularly limited, and may be linear or branched. As for the linear alkoxy group, an alkoxy group having 1 to 6 carbon atoms is preferred. An alkoxy group having 1 to 3 carbon atoms is more preferred. As for the branched alkoxy group, an alkoxy group having 3 to 10 carbon atoms is preferred, and an alkoxy group having 3 to 6 carbon atoms is more preferred.

[0067] R 3 ~R 12 However, when each independently represents an organic group having 2 to 10 carbon atoms, the alkenyloxy group having 2 to 10 carbon atoms is not particularly limited, but may be linear or branched, with alkenyloxy groups having 2 to 6 carbon atoms being preferred, and alkenyloxy groups having 2 to 3 carbon atoms being more preferred.

[0068] R 3 ~R 12 However, when each independently represents an alkynyloxy group having 2 to 10 carbon atoms as an organic group, the alkynyloxy group having 2 to 10 carbon atoms is not particularly limited, but may be linear or branched, with an alkynyloxy group having 2 to 6 carbon atoms being preferred, and an alkynyloxy group having 2 to 3 carbon atoms being more preferred.

[0069] R 3 ~R 12 However, when each independently represents a cycloalkoxy group having 3 to 10 carbon atoms as an organic group, the cycloalkoxy group having 3 to 10 carbon atoms is not particularly limited, but may be monocyclic or polycyclic, with a cycloalkoxy group having 3 to 8 carbon atoms being preferred, and a cycloalkoxy group having 3 to 6 carbon atoms being more preferred.

[0070] R 3 ~R 12 However, when each independently represents a cycloalkenyloxy group having 3 to 10 carbon atoms as an organic group, the cycloalkenyloxy group having 3 to 10 carbon atoms is not particularly limited, but may be monocyclic or polycyclic, with a cycloalkenyloxy group having 3 to 8 carbon atoms being preferred, and a cycloalkenyloxy group having 3 to 6 carbon atoms being more preferred.

[0071] R 3~R 12 However, when each group independently represents an aryloxy group with 6 to 10 carbon atoms as an organic group, the aryloxy group with 6 to 10 carbon atoms is not particularly limited, but can be monocyclic or polycyclic, and examples include phenyloxy group and naphthyloxy group.

[0072] In general formulas (2) to (3), (6) and (7), R 3 ~R 12 However, when each of these independently represents an organic group selected from the above group, fluorine atoms, oxygen atoms, and unsaturated bonds can also be present in the organic group. Furthermore, "when a fluorine atom is present in the organic group" specifically refers to cases where a hydrogen atom in the above-mentioned group is replaced by a fluorine atom. Furthermore, "cases where an oxygen atom is present in the organic group" specifically refers to groups in which an "-O-" (ether bond) is interposed between the carbon atoms of the above-mentioned group.

[0073] X 5 ~X 7 However, when each of these independently represents an alkyl group having 1 to 10 carbon atoms as an organic group, the alkyl group having 1 to 10 carbon atoms is not particularly limited, and may be linear or branched. As for the linear alkyl group, alkyl groups having 1 to 6 carbon atoms are preferred, and alkyl groups having 1 to 3 carbon atoms are more preferred. As for the branched alkyl group, alkyl groups having 3 to 10 carbon atoms are preferred, and alkyl groups having 3 to 6 carbon atoms are more preferred.

[0074] X 5 ~X 7 However, when each independently represents an alkenyl group having 2 to 10 carbon atoms as an organic group, the alkenyl group having 2 to 10 carbon atoms is not particularly limited, but may be linear or branched, with alkenyl groups having 2 to 6 carbon atoms being preferred, and alkenyl groups having 2 to 3 carbon atoms being more preferred.

[0075] X 5 ~X 7However, when each independently represents an alkynyl group having 2 to 10 carbon atoms as an organic group, the alkynyl group having 2 to 10 carbon atoms is not particularly limited, but may be linear or branched, with an alkynyl group having 2 to 6 carbon atoms being preferred, and an alkynyl group having 2 to 3 carbon atoms being more preferred.

[0076] X 5 ~X 7 However, when each group independently represents a cycloalkyl group having 3 to 10 carbon atoms as an organic group, the cycloalkyl group having 3 to 10 carbon atoms is not particularly limited, but may be monocyclic or polycyclic, with 3 to 8 carbon atoms being preferred, and 3 to 6 carbon atoms being more preferred.

[0077] X 5 ~X 7 However, when each independently represents a cycloalkenyl group having 3 to 10 carbon atoms as an organic group, the cycloalkenyl group having 3 to 10 carbon atoms is not particularly limited, but may be monocyclic or polycyclic, with a cycloalkenyl group having 3 to 8 carbon atoms being preferred, and a cycloalkenyl group having 3 to 6 carbon atoms being more preferred.

[0078] X 5 ~X 7 However, when each of these independently represents an aryl group having 6 to 10 carbon atoms as an organic group, the aryl group having 6 to 10 carbon atoms is not particularly limited, but can be monocyclic or polycyclic, and examples include phenyl groups and naphthyl groups.

[0079] X 5 ~X 7 However, when each independently represents an alkoxy group with 1 to 10 carbon atoms as an organic group, the above R is an example of an alkoxy group with 1 to 10 carbon atoms. 3 ~R 12 However, each of these can independently be described as being the same as the alkoxy groups having 1 to 10 carbon atoms when representing an alkoxy group having 1 to 10 carbon atoms as an organic group, and the preferred range is also the same.

[0080] X 5 ~X 7However, when each independently represents an alkenyloxy group with 2 to 10 carbon atoms as an organic group, the above R is used to represent an alkenyloxy group with 2 to 10 carbon atoms. 3 ~R 12 However, each can independently represent an alkenyloxy group having 2 to 10 carbon atoms as an organic group, and the same can be listed as an alkenyloxy group having 2 to 10 carbon atoms, and the preferred range is also the same.

[0081] X 5 ~X 7 However, when each independently represents an alkynyloxy group with 2 to 10 carbon atoms as an organic group, the above R is used to represent an alkynyloxy group with 2 to 10 carbon atoms. 3 ~R 12 However, independently of each other, we can list the same alkynyloxy groups with 2 to 10 carbon atoms as organic groups, and the preferred range is also the same.

[0082] X 5 ~X 7 However, when each independently represents a cycloalkoxy group with 3 to 10 carbon atoms as an organic group, the above R is used to represent a cycloalkoxy group with 3 to 10 carbon atoms. 3 ~R 12 However, independently of each other, we can list the same cycloalkoxy groups with 3 to 10 carbon atoms as those representing organic groups, and the preferred range is also the same.

[0083] X 5 ~X 7 However, when each independently represents a cycloalkenyloxy group with 3 to 10 carbon atoms as an organic group, the above R is used to represent a cycloalkenyloxy group with 3 to 10 carbon atoms. 3 ~R 12 However, independently of each other, examples can be given that are the same as cycloalkenyloxy groups having 3 to 10 carbon atoms as organic groups, and the preferred range is also the same.

[0084] X5 ~X 7 However, when each independently represents an aryloxy group with 6 to 10 carbon atoms as an organic group, the above R is used to represent an aryloxy group with 6 to 10 carbon atoms. 3 ~R 12 However, independently of each other, examples can be given that are the same as those of aryloxy groups having 6 to 10 carbon atoms when representing an aryloxy group having 6 to 10 carbon atoms as an organic group, and the preferred range is also the same.

[0085] In general formulas (5) and (7), X 5 ~X 7 However, when each of these independently represents an organic group selected from the above group, fluorine atoms, oxygen atoms, and unsaturated bonds can also be present in the organic group. Furthermore, "when a fluorine atom is present in the organic group" specifically refers to cases where a hydrogen atom in the above-mentioned group is replaced by a fluorine atom. Furthermore, "cases where an oxygen atom is present in the organic group" specifically refers to groups in which an "-O-" (ether bond) is interposed between the carbon atoms of the above-mentioned group.

[0086] M 2 ~M 8 These are, independently, a proton, a metal cation, or an onium cation. 2 ~M 8 These are, independently and typically, monovalent cations. M 2 ~M 8 However, when each term independently represents a metal cation, the metal cations are not particularly limited, but examples include alkali metal cations, such as lithium ions, sodium ions, or potassium ions. M 2 ~M 8 However, when each represents an onium cation independently, the onium cations are not particularly limited, but examples include tetraalkylammonium ions, tetraalkylphosphonium ions, imidazolium ions, and ammonium ions having a spiro skeleton. 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.

[0087] In general formula (8), R 13 ~R 16 However, when each of these independently represents an alkyl group having 1 to 10 carbon atoms, the alkyl group having 1 to 10 carbon atoms is not particularly limited, and may be linear or branched. As for the linear alkyl group, alkyl groups having 1 to 6 carbon atoms are preferred, and alkyl groups having 1 to 3 carbon atoms are more preferred. As for the branched alkyl group, alkyl groups having 3 to 10 carbon atoms are preferred, and alkyl groups having 3 to 6 carbon atoms are more preferred.

[0088] R 13 ~R 16 However, when each term independently represents a fluoroalkyl group having 1 to 10 carbon atoms, the fluoroalkyl group having 1 to 10 carbon atoms is not particularly limited and may be linear or branched. Note that a "fluoroalkyl group" is a group in which some or all of the hydrogen atoms of an alkyl group are replaced with fluorine atoms. As for the linear fluoroalkyl group, a fluoroalkyl group having 1 to 6 carbon atoms is preferred, and a fluoroalkyl group having 1 to 3 carbon atoms is more preferred. As the branched fluoroalkyl group, fluoroalkyl groups having 3 to 10 carbon atoms are preferred, and fluoroalkyl groups having 3 to 6 carbon atoms are more preferred. The alkyl groups having 1 to 10 carbon atoms and the fluoroalkyl groups having 1 to 10 carbon atoms may have substituents.

[0089] In general formula (9), R 17 ~R 22 However, when each independently represents an alkyl group having 1 to 10 carbon atoms, the alkyl group having 1 to 10 carbon atoms is as follows: 13 ~R 16 However, each can independently represent the same alkyl groups with 1 to 10 carbon atoms as those with 1 to 10 carbon atoms, and the preferred range is also the same.

[0090] R 17 ~R 22 However, when each independently represents a fluoroalkyl group having 1 to 10 carbon atoms, the above R is used to represent a fluoroalkyl group having 1 to 10 carbon atoms. 13 ~R 16 However, each can independently represent the same fluoroalkyl groups with 1 to 10 carbon atoms as those with 1 to 10 carbon atoms, and the preferred range is also the same.

[0091] It is preferable that the compound represented by the above general formula (1) is at least one selected from the group consisting of NaBF2(C2O4), NaPF4(C2O4), NaPF2(C2O4)2, and NaP(C2O4)3. The compound represented by the above general formula (2) is R 3 and R 4 However, each is independently a fluorine atom, a methoxy group, an ethoxy group, or a propargyloxy group. M 2 However, these are lithium ions, sodium ions, potassium ions, or tetraalkylammonium ions. Preferably, it is at least one selected from the group consisting of compounds.

[0092] The compound represented by the above general formula (3) is R 5 and R 6 However, each is independently a fluorine atom, a methoxy group, or an ethoxy group, M 3However, these are lithium ions, sodium ions, potassium ions, or tetraalkylammonium ions. Preferably, it is at least one selected from the group consisting of compounds.

[0093] The compound represented by the above general formula (4) is M 4 and M 5 However, each is independently a lithium ion, a sodium ion, a potassium ion, or a tetraalkylammonium ion. Preferably, it is at least one selected from the group consisting of compounds.

[0094] It is preferable that the compound represented by the above general formula (5) is at least one selected from the group consisting of LiN(SO2F)2, LiN(SO2F)(SO2CF3), NaN(SO2F)2, NaN(SO2F)(SO2CF3), KN(SO2F)2, and KN(SO2F)(SO2CF3). It is preferable that the compound represented by the above general formula (6) is at least one selected from the group consisting of LiN(POF2)2, LiN(POF2)(PO(OCH3)2), NaN(POF2)2, NaN(POF2)(PO(OCH3)2), KN(POF2)2, and KN(POF2)(PO(OCH3)2). It is preferable that the compound represented by the above general formula (7) is at least one selected from the group consisting of LiN(POF2)(SO2F), LiN(PO(OCH3)2)(SO2F), NaN(POF2)(SO2F), NaN(PO(OCH3)2)(SO2F), KN(POF2)(SO2F), and KN(PO(OCH3)2)(SO2F).

[0095] It is preferable that the compound represented by the above general formula (8) is at least one selected from the group consisting of 1,3-propensultone, 1,4-butensultone, and 2-methyl-1,3-propensultone. It is preferable that the compound represented by the above general formula (9) is at least one selected from the group consisting of 1,3-propanesultone, 1,4-butanesultone, 1-methyl-1,3-propanesultone, and 3-methyl-1,3-propanesultone.

[0096] The content y of component (II) is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, more preferably 0.1% 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, the content y of component (II) is not particularly limited, but is preferably 10.0% by mass or less, more preferably 8.0% by mass or less, even more preferably 5.0% by mass or less, even more preferably 3.5% by mass or less, and particularly preferably 2.5% by mass or less, relative to the total amount of electrolyte for non-aqueous sodium-ion batteries. If it is 0.01% by mass or more, at least one of the following can be improved: the cycle characteristics of the non-aqueous sodium-ion battery at high temperatures of 60°C or higher, the amount of gas generated during high-temperature cycle testing (suppression effect), and the high-temperature storage characteristics. Furthermore, if it is 10.0% by mass or less, the film formed on the electrodes does not become too thick, which is less likely to lead to an increase in resistance. Component (II) may be used alone, or two or more components may be mixed in any combination and ratio according to the application. In one embodiment, the content y of component (II) is preferably 0.01% by mass ≤ y ≤ 10.0% by mass, more preferably 0.03% by mass ≤ y ≤ 8.0% by mass, even more preferably 0.1% by mass ≤ y ≤ 5.0% by mass, even more preferably 0.1% by mass ≤ y ≤ 3.5% by mass, and particularly preferably 0.8% by mass ≤ y ≤ 2.5% by mass, relative to the total amount of electrolyte for the non-aqueous sodium-ion battery.

[0097] [(III) Sodium salt] The type of sodium salt used as the solute is not particularly limited, and any sodium salt (excluding the aforementioned fluorosulfate) 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), and NaN(C a F 2a+1 SO2)(C b F 2b+1 Examples 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 (III) sodium salt.

[0098] The concentration z of the 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 electrolyte concentration to 0.05 mol / L or higher makes it easier to suppress the decrease in cycle performance 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 performance due to a decrease in ionic conductivity. Component (III) may be used alone, or two or more components may be mixed in any combination and ratio according to the application. In one embodiment, the concentration z of component (III) is preferably 0.3 mol / L ≤ z ≤ 5.0 mol / L, more preferably 0.4 mol / L ≤ z ≤ 3.0 mol / L, even more preferably 0.5 mol / L ≤ z ≤ 2.0 mol / L, and particularly preferably 0.8 mol / L ≤ z ≤ 1.5 mol / L, relative to the total amount of electrolyte for the non-aqueous sodium ion battery.

[0099] Although some of the sodium salts (III) overlap with component (II), if the content is above a predetermined amount (the concentration of sodium salt (III) 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 acts as the main electrolyte (sodium salt (III)), and if it is below the predetermined amount, it acts as an additive (component (II)). Furthermore, component (II) is a different compound from the sodium salt (III) mentioned above. For example, if (III) the sodium salt is NaBF2(C2O4), then component (II) is a compound other than NaBF2(C2O4).

[0100] [(IV) Non-aqueous solvents] The type of non-aqueous solvent is not particularly limited, and any non-aqueous solvent can be used. Specific examples include the following non-aqueous solvents. Examples of cyclic esters include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate (excluding vinylene carbonate), as well as γ-butyrolactone and γ-valerolactone. Examples of linear esters include linear carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, as well as 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.

[0101] In one preferred embodiment, the electrolyte for the non-aqueous sodium-ion battery includes at least one selected from the group consisting of cyclic esters, linear esters, cyclic ethers, and linear ethers as the non-aqueous solvent. 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. In another preferred embodiment, the electrolyte for the non-aqueous sodium-ion battery also contains a linear ester as the non-aqueous solvent, wherein the linear ester is a linear carbonate.

[0102] Furthermore, the electrolyte for the non-aqueous sodium-ion battery more preferably contains, as the non-aqueous solvent, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl 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. These non-aqueous solvents may be used individually, or two or more may be mixed in any combination and ratio depending on the application.

[0103] [Other additives] Without departing from the gist of this disclosure, 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 oligomers of cyclohexylbenzene, biphenyl, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate (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, and trans-difluoroethylene carbonate. Examples of compounds that have overcharge prevention effects, negative electrode film formation effects, and positive electrode protection effects include dimethyl vinylene carbonate, 1,3,2-dioxathiolan-2,2-dioxide, 4-propyl-1,3,2-dioxathiolan-2,2-dioxide, methylene methane disulfonate, 1,2-ethane disulfonic anhydride, 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.

[0104] Among them, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate oligomers (number average molecular weight 170-5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynylethylene carbonate, trans-difluoroethylene carbonate, 1,3,2-dioxathiolan-2,2-dioxide, 4-propyl-1,3,2-dioxathiolan-2,2-dioxide, methylene methane disulfonate, At least one compound selected from the group consisting of 1,2-ethanedisulfonic anhydride, 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 vinylethylene carbonate, trans-difluoroethylene carbonate, or 1,2-ethanedisulfonic anhydride being more preferred.

[0105] In the case where the electrolyte for the non-aqueous sodium-ion battery according to this embodiment contains fluoroethylene carbonate, the amount should preferably not be too high from the viewpoint of gas generation, and fluoroethylene carbonate may be substantially absent. Substantially absent means "less than 0.001% by mass of the total amount of the electrolyte." A preferred embodiment is one in which the electrolyte for the non-aqueous sodium-ion battery according to this embodiment does not contain fluoroethylene carbonate.

[0106] When the electrolyte for the non-aqueous sodium-ion battery according to this embodiment contains 1,3,2-dioxathiolane-2,2-dioxide and / or 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, the amount contained is preferably not too high from the viewpoint of storage stability, and may be substantially absent. A preferred embodiment is one in which the electrolyte for the non-aqueous sodium-ion battery according to this embodiment does not contain 1,3,2-dioxathiolane-2,2-dioxide and / or 4-propyl-1,3,2-dioxathiolane-2,2-dioxide.

[0107] 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% by mass or less relative to the total amount of the electrolyte.

[0108] Furthermore, the above-mentioned sodium salts (sodium salts other than those used as solutes (excluding those corresponding to component (I) and component (II))) 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 0.3% by mass or more and 1.5% by mass or less relative to the total amount of electrolyte.

[0109] 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.

[0110] [2. Non-aqueous sodium-ion battery] Next, the configuration of a non-aqueous sodium-ion battery according to one embodiment of the present disclosure 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.

[0111] [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, Na 2 / 3 Ni 1 / 3 Ti 1 / 6 Mn 1 / 2 O2, Na 2 / 3 Ni 1 / 3 Mn 2 / 3 Sodium-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, those in which some of the transition metals are replaced with other metals, polyanionic compounds such as NaFePO4, NaVPO4F, Na3V2(PO4)3, and Na2Fe2(SO4)3, 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.

[0112] 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.

[0113] [Negative electrode] The negative electrode material (negative electrode active material) is not particularly limited, but examples include materials capable of intercalating and deintercalating sodium metal or 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.

[0114] 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).

[0115] [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.

[0116] [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.

[0117] [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.

[0118] 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.

[0119] [3. Method for manufacturing non-aqueous sodium-ion batteries] This disclosure also relates to a method for manufacturing non-aqueous sodium-ion batteries. The aforementioned manufacturing method is A step of preparing an electrolyte for a non-aqueous sodium-ion battery as disclosed herein, 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]

[0120] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to such examples.

[0121] [Preparation of electrolyte for non-aqueous sodium-ion batteries] (Preparation of electrolyte solution No. NaSO3F(2.0)-PF4(1.0)) (IV) As a non-aqueous solvent, a mixed solvent was used, which consisted of propylene carbonate (hereinafter also referred to as "PC"), ethylene carbonate (hereinafter also referred to as "EC"), and ethyl methyl carbonate (hereinafter also referred to as "EMC") mixed in a volume ratio of PC:EC:EMC = 30:20:50. In this solvent, (III) NaPF6 as the sodium salt, (I) sodium fluorosulfate (hereinafter also referred to as "NaSO3F") as the fluorosulfate, and (II) NaPF4 (C2O4) as (II) were dissolved to the concentrations shown in Table 1 to prepare electrolyte No. NaSO3F(2.0)-PF4(1.0). The above preparation was carried out while maintaining the liquid temperature in the range of 20 to 30°C.

[0122] In Tables 1, 16, 18, 20, and 22 below, the concentrations (mass%) of (I) fluorosulfates, component (II), and other additives represent the content (mass%) relative to the total amount of electrolyte for non-aqueous sodium ion batteries. In Tables 1, 16, 18, 20, and 22 below, the concentration (mol / L) for (III) sodium salt represents the concentration relative to the total amount of electrolyte for non-aqueous sodium ion batteries.

[0123] [Table 1]

[0124] (Preparation of electrolytes related to Table 1) Furthermore, the various electrolytes listed in Table 1 were prepared in the same manner as electrolyte No. NaSO3F(2.0)-PF4(1.0), except that the concentration of (I) and the type and concentration of (II) were changed to those listed in Table 1. The abbreviations in the table are as follows. PF4: NaPF4(C2O4) PF2: NaPF2(C2O4)2 BF2: NaBF2(C2O4) PO2F2: NaPO2F2 B-PO2F2: NaBF3(PO2F2) B2-PO3F: Na2(BF3)2(PO3F) FSI: NaN(SO2F)2 N(POF2)2: NaN(POF2)2 N(POF2)(SO2F): NaN(POF2)(SO2F) PRS: 1,3-Propensulton PS: 1,3-propanesultone VC: Vinylen carbonate TMSB: Tris(trimethylsilyl)borate TMSP: Tris(trimethylsilyl)phosphate

[0125] [Example 1-1, Comparative Examples 1-0 to 1-2] 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 cycle characteristics, gas generation during the high-temperature cycling test, and high-temperature storage characteristics were evaluated. The evaluation results are shown in Table 2. The test cell was fabricated as follows.

[0126] The test positive electrode was prepared using the following procedure. NaNi as the positive electrode active material 0.5 Ti 0.3 Mn 0.2 A 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.

[0127] 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.

[0128] 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.

[0129] [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. 2 The cells underwent repeated charge-discharge cycles. The degree of cell degradation was evaluated by the discharge capacity retention rate after 500 cycles in a charge-discharge test at an ambient temperature of 60°C. The "high-temperature cycle-retention rate," which is the discharge capacity retention rate after 500 cycles, was calculated using the following formula. The initial discharge capacity was defined as the discharge capacity after the first cycle of the charge-discharge test at an ambient temperature of 60°C. High-temperature cycle retention rate (%) = (Discharge capacity at 500 cycles / Initial discharge capacity) × 100

[0130] [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 = the volume V2 of the cell after the high-temperature cycle characteristic evaluation - the volume V1 of the cell before the high-temperature cycle characteristic evaluation) was determined. Based on this gas generation amount V, the "gas generation amount during high-temperature cycle" was evaluated.

[0131] [High-temperature storage characteristic evaluation] For the test cell, at an environmental temperature of 25°C, charging was performed by the constant current and constant voltage method up to a charging upper limit voltage of 4.1V with a current density of 0.32 mA / cm 2 After charging, discharging was performed at a constant current of 0.32 mA / cm 2 to 1.5V. The same charge and discharge were repeated 10 cycles. The discharge capacity of the 10th cycle was defined as the "initial discharge capacity". Then, at an environmental temperature of 25°C, charging was performed by the constant current and constant voltage method up to a charging upper limit voltage of 4.1V with a current density of 0.32 mA / cm 2 After charging, it was stored at 60°C for 4 weeks, and after cooling the battery to 25°C, discharging was performed at a constant current of 0.32 mA / cm 2 to 1.5V at an environmental temperature of 25°C. After charging by the constant current and constant voltage method up to a charging upper limit voltage of 4.1V with a current density of 0.32 mA / cm 2 After charging, discharging was performed at a constant current of 0.32 mA / cm 2 to 1.5V. The discharge capacity at this time was defined as the "recovery capacity". The "recovery discharge capacity maintenance rate after high-temperature storage" was obtained by the following formula. <Recovery discharge capacity maintenance rate after high-temperature storage> Recovery discharge capacity maintenance rate after high-temperature storage (%) = (Recovery capacity / Initial discharge capacity) × 100

[0132]

Table 2

[0133] The evaluation results of the examples and comparative examples in Table 2 are relative values with the evaluation result of Comparative Example 1-0 as 100%. The same applies to all subsequent tables. Note that for the "discharge capacity maintenance rate after high-temperature cycle", the larger the value, the more desirable; for the "recovery discharge capacity maintenance rate after high-temperature storage", the larger the value, the more desirable; and for the "gas generation amount during high-temperature cycle", the smaller the value, the more desirable.

[0134] From the evaluation results in Table 2, it was found that by including both (I) and (II) in the non-aqueous electrolyte (Example 1-1), the discharge capacity retention rate after high-temperature cycling was further improved compared to simply adding the effects of the addition when only (I) was included (Comparative Example 1-1) and the addition when only (II) was included (Comparative Example 1-2) (Figure 1). Furthermore, a similar trend of further improvement was observed in the suppression of gas generation during high-temperature cycling and in the maintenance rate of recovery discharge capacity after high-temperature storage (Figures 2 and 3). Although the mechanism by which the above-mentioned further improvement trend occurs is not clear, it is presumed that the inclusion of both (I) and (II) in the non-aqueous electrolyte formed a good coating on the electrode.

[0135] [Examples 1-2 to 1-14, Comparative Examples 1-3 to 1-15] Except for using the electrolytes listed in Tables 3 to 15 as the test electrolytes, test cells were prepared in the same manner as in Example 1-1, and performance evaluations were conducted. The evaluation results are shown in Tables 3 to 15.

[0136] [Table 3]

[0137] [Table 4]

[0138] [Table 5]

[0139] [Table 6]

[0140] [Table 7]

[0141]

Table 8

[0142]

Table 9

[0143]

Table 10

[0144]

Table 11

[0145]

Table 12

[0146]

Table 13

[0147]

Table 14

[0148]

Table 15

[0149] From the evaluation results of Tables 3 to 15, even when changing the type and concentration of (II), similar to Example 1-1, further improvement tendencies were confirmed for the discharge capacity retention rate after high-temperature cycling, the suppression effect of gas generation amount during high-temperature cycling, and the recovery discharge capacity retention rate after high-temperature storage.

[0150] Furthermore, regarding the discharge capacity retention rate after high-temperature cycling, it was found that the improvement effect was particularly large in Examples 1-1, 1-2, 1-3, and 1-12, which used the compound represented by general formula (1), vinylene carbonate, as (II).

[0151] Furthermore, regarding the effect of suppressing gas generation during high-temperature cycling, it was found that the improvement effect was particularly large in Examples 1-3, 1-4, 1-5, 1-6, and 1-12, which used the compound represented by general formula (1), the compound represented by general formula (2), the compound represented by general formula (3), the compound represented by general formula (4), and vinylene carbonate.

[0152] Furthermore, regarding the recovery discharge capacity retention rate after high-temperature storage, it was found that the improvement effect was particularly large in Examples 1-3, 1-4, 1-8, 1-9, 1-10, 1-11, and 1-12, which used the compound represented by general formula (1), the compound represented by general formula (2), the compound represented by general formula (6), the compound represented by general formula (7), the compound represented by general formula (8), the compound represented by general formula (9), and vinylene carbonate, as (II).

[0153] [Examples 2-1 to 2-8, Comparative Examples 2-1 to 2-10] The various electrolytes listed in Table 16 were prepared in the same manner as electrolyte No. NaSO3F(2.0)-PF4(1.0), except that the electrolyte composition was changed to the electrolyte composition listed in Table 16. A test cell was prepared in the same manner as in Example 1-1, except that the electrolyte listed in Table 17 was used as the test electrolyte, and performance evaluation was performed. The evaluation results are shown in Table 17.

[0154] [Table 16]

[0155] [Table 17]

[0156] From the evaluation results in Table 17, it was found that even when the concentration of (I) was changed in various ways, including both (I) and (II) in the non-aqueous electrolyte resulted in a greater improvement in at least one of the following compared to simply adding together the additive effect when only (I) was included (Comparative Examples 2-1 to 2-8) and the additive effect when only (II) was included (Comparative Example 2-9). This improvement was achieved by including both (I) and (II) together in the non-aqueous electrolyte. In particular, it can be seen that the improvement effect is significant when the concentration of (I) is between 0.1 and 7.0 mass%.

[0157] [Examples 3-1 to 3-6, Comparative Examples 3-1 to 3-6] The various electrolytes listed in Table 18 were prepared in the same manner as electrolyte No. NaSO3F(2.0)-PF4(1.0), except that the electrolyte composition was changed to the electrolyte composition listed in Table 18. A test cell was prepared and its performance evaluated in the same manner as in Example 1-1, except that the electrolyte listed in Table 19 was used as the test electrolyte. The evaluation results are shown in Table 19.

[0158] [Table 18]

[0159] [Table 19]

[0160] From the evaluation results in Table 19, it was found that even when the concentration of (II) was varied, including both (I) and (II) in the non-aqueous electrolyte resulted in a greater improvement in at least one of the following compared to simply adding together the additive effect when only (I) was included (Comparative Example 2-5) and the additive effect when only the corresponding (II) was included (Comparative Examples 3-1 to 3-6). This improvement was achieved by including both (I) and (II) together in the non-aqueous electrolyte. In particular, it was found that the improvement effect was significant when the concentration of (II) was between 0.1 and 5% by mass.

[0161] [Examples 4-1 to 4-6, Comparative Examples 4-1 to 4-6] The various electrolytes listed in Table 20 were prepared in the same manner as electrolyte No. NaSO3F(2.0)-PF4(1.0), except that the electrolyte composition was changed to the electrolyte composition listed in Table 20. A test cell was prepared in the same manner as in Example 1-1, except that the electrolyte listed in Table 21 was used as the test electrolyte, and performance evaluation was performed. The evaluation results are shown in Table 21. The abbreviations used in the table are as follows: FEC: Fluoroethylene carbonate DTD: 1,3,2-dioxathiolan-2,2-dioxide EPFP: (Ethoxy)pentafluorocyclotriphosphazene

[0162] [Table 20]

[0163] [Table 21]

[0164] As shown in Table 21, even when other additives were further included (Examples 4-1 to 4-3), a further improvement trend in the discharge capacity retention rate after high-temperature cycling was observed, similar to the case where other additives were not included (Examples 4-4, 4-5, and 4-6). Furthermore, the electrolyte in Example 4-2 (Comparative Examples 4-3 and 4-4) showed a tendency to have inferior storage stability compared to the electrolytes in the other examples of this disclosure. Specifically, after storage at 25°C for one month, the electrolyte had turned dark brown. Analysis by gas chromatography revealed that the DTD concentration in the electrolyte had decreased to 0.35% by mass.

[0165] [Example 5-1, Comparative Examples 5-1 to 5-2, Example 6-1, Comparative Examples 6-1 to 6-2] The various electrolytes listed in Table 22 were prepared in the same manner as electrolyte No. NaSO3F(2.0)-PF4(1.0), except that the electrolyte composition was changed to the electrolyte composition listed in Table 22. A test cell was prepared and its performance evaluated in the same manner as in Example 1-1, except that the electrolyte listed in Table 23 was used as the test electrolyte. The evaluation results are shown in Table 23.

[0166] [Table 22]

[0167] [Table 23]

[0168] The results in Table 23 show that even when the type of (I) is changed, including both (I) and (II) in the non-aqueous electrolyte further improves the discharge capacity retention rate after high-temperature cycling compared to simply adding up the effects of including only the corresponding (I) (Comparative Examples 5-1, 6-1) and the effects of including only (II) (Comparative Examples 5-2, 6-2). Furthermore, a similar trend of further improvement was observed in the suppression of gas generation during high-temperature cycling and in the maintenance rate of recovery discharge capacity after high-temperature storage. [Industrial applicability]

[0169] Embodiments of this disclosure provide an electrolyte for a non-aqueous sodium-ion battery that can improve at least one of the following: the cycle characteristics of a non-aqueous sodium-ion battery at high temperatures of 60°C or higher, the amount of gas generated during high-temperature cycle testing (and its suppression effect), and the high-temperature storage characteristics; a non-aqueous sodium-ion battery using the same; and a method for manufacturing a non-aqueous sodium-ion battery.

[0170] 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. 2021-082006 filed on May 13, 2021, the contents of which are incorporated herein by reference.

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