Nonaqueous solvent solution and method for producing nonaqueous electrolyte solution

Abstract

Provided is a nonaqueous solvent solution containing a nonaqueous solvent, a difluorobis(oxalato)phosphate, and a tris(oxalato)phosphate, wherein: the concentration of the difluorobis(oxalato)phosphate in the nonaqueous solvent solution is 10-50 mass%; and the ratio of the difluorobis(oxalato)phosphate and the tris(oxalato)phosphate is 0.001 mol or more of the tris(oxalato)phosphate to 1 mol of the difluorobis(oxalato)phosphate. Further provided is a method for producing a nonaqueous electrolyte that involves adding the nonaqueous solvent solution to a reference nonaqueous electrolyte containing a solute and a nonaqueous electrolyte solvent.

Description

Method for producing non-aqueous solvent solution and non-aqueous electrolyte solution

[0001] The present disclosure relates to a method for producing a non-aqueous solvent solution and a non-aqueous electrolyte solution.

[0002] Difluorobis(oxalato)phosphate is used as an additive for nonaqueous electrolyte batteries, etc. Example 7 of Patent Document 1 describes that an electrolyte solution of any concentration can be prepared using a difluorobis(oxalato)phosphate solution. Example 8 of Patent Document 2 describes an ethyl methyl carbonate solution containing 37% by mass of lithium difluorobis(oxalato)phosphate and 2% by mass of lithium tetrafluoro(oxalato)phosphate. Patent Document 2 also describes that a lithium difluorobis(oxalato)phosphate solution can be used as an additive effective for improving the performance of nonaqueous electrolyte batteries. Thus, when preparing a nonaqueous electrolyte containing difluorobis(oxalato)phosphate, the difluorobis(oxalato)phosphate may be added in the form of a nonaqueous solvent solution of difluorobis(oxalato)phosphate at a predetermined concentration (hereinafter, sometimes referred to as a "concentrated solution of difluorobis(oxalato)phosphate" or simply as a "concentrated solution").

[0003] Japanese Patent Application Publication No. 2014-005269 Japanese Patent Application Publication No. 2010-143835

[0004] However, the inventors of the present invention have found through their investigations that difluorobis(oxalato)phosphate is unstable in water, and that when water is mixed into a concentrated solution of difluorobis(oxalato)phosphate, the concentration of the difluorobis(oxalato)phosphate decreases, which is a problem.

[0005] An object of the present disclosure is to provide a concentrated solution of difluorobis(oxalato)phosphate that exhibits excellent stability even when water is mixed in. Another object of the present disclosure is to provide a method for producing a nonaqueous electrolyte solution using the concentrated solution of difluorobis(oxalato)phosphate.

[0006] As a result of extensive research into solving these problems, the present inventors have found that by adding a specific amount or more of tris(oxalato)phosphate, it is possible to provide a concentrated solution of difluorobis(oxalato)phosphate that is excellent in stability even when water is mixed in. Specifically, the above problem can be solved by the following configuration.

[0007] [1] A non-aqueous solvent solution comprising a non-aqueous solvent, a difluorobis(oxalato)phosphate, and a tris(oxalato)phosphate, wherein the concentration of the difluorobis(oxalato)phosphate in the non-aqueous solvent solution is 10 to 50 mass %, and the ratio of the difluorobis(oxalato)phosphate to the tris(oxalato)phosphate is 0.001 mole or more per mole of the difluorobis(oxalato)phosphate. [2] The non-aqueous solvent solution according to [1], further comprising a tetrafluorooxalatophosphate. [3] The non-aqueous solvent solution according to [2], wherein the ratio of the difluorobis(oxalato)phosphate to the tetrafluorooxalatophosphate is 0.010 to 0.25 moles per mole of the difluorobis(oxalato)phosphate. [4] The nonaqueous solvent solution according to any one of [1] to [3], further comprising a difluorophosphate. [5] The nonaqueous solvent solution according to [4], wherein the ratio of the difluorobis(oxalato)phosphate to the difluorophosphate is 0.001 to 0.05 mol per 1 mol of the difluorobis(oxalato)phosphate. [6] The nonaqueous solvent solution according to [4], further comprising a tetrafluorooxalatophosphate, wherein the ratio of the difluorobis(oxalato)phosphate to the tetrafluorooxalatophosphate and the difluorophosphate is 0.010 to 0.25 mol and 0.001 to 0.05 mol per 1 mol of the difluorobis(oxalato)phosphate. [7] The nonaqueous solvent solution according to [1], wherein the ratio of the difluorobis(oxalato)phosphate to the tris(oxalato)phosphate is 1 mole of the difluorobis(oxalato)phosphate to 0.03 moles or less of the tris(oxalato)phosphate. [8] The nonaqueous solvent solution according to [1], wherein the nonaqueous solvent contains at least one of a cyclic ester and a chain ester. [9] The nonaqueous solvent solution according to [8], wherein the content of the chain ester is 50 to 100% by volume relative to the total amount of the nonaqueous solvent.

[10] The nonaqueous solvent solution according to [8], wherein the cyclic ester is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, and γ-butyrolactone, and the chain ester is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate.

[11] A method for producing a nonaqueous electrolyte, comprising adding the nonaqueous solvent solution according to any one of [1] to

[10] to a reference nonaqueous electrolyte containing a solute and a solvent for the nonaqueous electrolyte.

[12] The method for producing a nonaqueous electrolyte according to

[11] , wherein the reference nonaqueous electrolyte contains other additives.

[13] The method for producing a nonaqueous electrolyte according to

[11] , further comprising a step of adding other additives.

[14] A method for producing a non-aqueous electrolyte solution, comprising mixing the non-aqueous solvent solution according to any one of [1] to

[10] , a solute, and a solvent for the non-aqueous electrolyte solution.

[15] The method for producing a non-aqueous electrolyte solution according to

[14] , further comprising a step of adding other additives.

[16] The other additives are selected from the group consisting of difluoro(oxalato)borate, bis(oxalato)borate, fluorosulfonate, bis(trifluoromethanesulfonyl)imide salt, bis(fluorosulfonyl)imide salt, (trifluoromethanesulfonyl)(fluorosulfonyl)imide salt, bis(difluorophosphoryl)imide salt, (difluorophosphoryl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(trifluoromethanesulfonyl)imide salt, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate, vinylene carbonate oligomer (number average molecular weight of 170 to 5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynyl ethylene carbonate, methyl ...

[14] The method for producing a non-aqueous electrolyte solution according to

[13] , wherein the non-aqueous electrolyte is at least one selected from the group consisting of ethylene carbonate, trans-difluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane-2,2-dioxide, 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, methylenemethane disulfonate, 1,2-ethanedisulfonic anhydride, tris(trimethylsilyl)borate, succinonitrile, adiponitrile, (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.

[17] The other additives are selected from the group consisting of difluoro(oxalato)borate, bis(oxalato)borate, fluorosulfonate, bis(trifluoromethanesulfonyl)imide salt, bis(fluorosulfonyl)imide salt, (trifluoromethanesulfonyl)(fluorosulfonyl)imide salt, bis(difluorophosphoryl)imide salt, (difluorophosphoryl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(trifluoromethanesulfonyl)imide salt, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate, vinylene carbonate oligomer (number average molecular weight of 170 to 5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynyl ethylene carbonate, methyl ...

[16] The method for producing a non-aqueous electrolyte solution according to

[15] , wherein the non-aqueous electrolyte is at least one selected from the group consisting of ethylene carbonate, trans-difluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane-2,2-dioxide, 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, methylenemethane disulfonate, 1,2-ethanedisulfonic anhydride, tris(trimethylsilyl)borate, succinonitrile, adiponitrile, (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.

[0008] According to the present disclosure, it is possible to provide a concentrated solution of difluorobis(oxalato)phosphate that exhibits excellent stability of the difluorobis(oxalato)phosphate even when water is mixed in. Furthermore, according to the present disclosure, it is possible to provide a method for producing a nonaqueous electrolyte solution using the concentrated solution of difluorobis(oxalato)phosphate.

[0009] In this specification, the word "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0010] The present disclosure will be described in detail below, but the following description of the constituent elements is an example of an embodiment of the present disclosure, and the present disclosure is not limited to these specific contents.

[0011] [Non-aqueous solvent solution] The non-aqueous solvent solution of the present disclosure is a non-aqueous solvent solution comprising: a non-aqueous solvent; a difluorobis(oxalato)phosphate; and a tris(oxalato)phosphate, wherein the concentration of the difluorobis(oxalato)phosphate in the non-aqueous solvent solution is 10 to 50 mass %, and the ratio of the difluorobis(oxalato)phosphate to the tris(oxalato)phosphate is 0.001 mole or more per mole of the difluorobis(oxalato)phosphate.

[0012] The non-aqueous solvent solution of the present disclosure has a difluorobis(oxalato)phosphate concentration of 10 to 50% by mass and is a concentrated solution. The difluorobis(oxalato)phosphate concentration of the non-aqueous solvent solution of the present disclosure may be 15 to 40% by mass.

[0013] Examples of difluorobis(oxalato)phosphates include lithium difluorobis(oxalato)phosphate and sodium difluorobis(oxalato)phosphate.

[0014] Examples of tris(oxalato)phosphates include lithium tris(oxalato)phosphate and sodium tris(oxalato)phosphate.

[0015] The ratio of difluorobis(oxalato)phosphate to tris(oxalato)phosphate is 0.001 mol or more, or may be 0.002 mol or more, or 0.004 mol or more, or 0.005 mol or more, of tris(oxalato)phosphate per 1 mol of difluorobis(oxalato)phosphate. Furthermore, the ratio of tris(oxalato)phosphate per 1 mol of difluorobis(oxalato)phosphate may be 0.30 mol or less, or may be 0.15 mol or less, or may be 0.07 mol or less, or may be 0.03 mol or less. When the ratio of tris(oxalato)phosphate per 1 mol of difluorobis(oxalato)phosphate is 0.03 mol or less, a nonaqueous electrolyte solution is prepared using the nonaqueous solvent solution, and the resulting nonaqueous electrolyte is used in a nonaqueous electrolyte battery, gas generation in the battery is unlikely to occur.

[0016] The nonaqueous solvent solution of the present disclosure may further contain a tetrafluorooxalatophosphate. Examples of the tetrafluorooxalatophosphate include lithium tetrafluorooxalatophosphate and sodium tetrafluorooxalatophosphate. The ratio of difluorobis(oxalato)phosphate to tetrafluorooxalatophosphate may be 0.010 to 0.30 mol, or may be 0.010 to 0.25 mol, of tetrafluorooxalatophosphate per 1 mol of difluorobis(oxalato)phosphate.

[0017] The nonaqueous solvent solution of the present disclosure may further contain a difluorophosphate. Examples of difluorophosphates include lithium difluorophosphate and sodium difluorophosphate. The ratio of difluorobis(oxalato)phosphate to difluorophosphate may be 0.001 to 0.05 moles of difluorophosphate per 1 mole of difluorobis(oxalato)phosphate.

[0018] The non-aqueous solvent solution of the present disclosure contains a tetrafluorooxalatophosphate and a difluorophosphate, and the ratio of difluorobis(oxalato)phosphate to tetrafluorooxalatophosphate to difluorophosphate may be 0.010 to 0.25 mol of tetrafluorooxalatophosphate and 0.001 to 0.05 mol of difluorophosphate per 1 mol of difluorobis(oxalato)phosphate.

[0019] (Non-aqueous Solvent) The non-aqueous solvent contained in the non-aqueous solvent solution of the present disclosure is not particularly limited, and any non-aqueous organic solvent can be used. Specific examples of the non-aqueous organic solvent include cyclic carbonates that are also cyclic esters, such as propylene carbonate (hereinafter sometimes referred to as "PC"), ethylene carbonate (hereinafter sometimes referred to as "EC"), and butylene carbonate; chain carbonates that are also chain esters, such as diethyl carbonate (hereinafter sometimes referred to as "DEC"), dimethyl carbonate (hereinafter sometimes referred to as "DMC"), and ethyl methyl carbonate (hereinafter sometimes referred to as "EMC"); cyclic esters such as γ-butyrolactone and γ-valerolactone; chain esters such as methyl acetate, methyl propionate, and ethyl propionate (hereinafter sometimes referred to as "EP"); cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, and dioxane; chain ethers such as dimethoxyethane and diethyl ether; sulfone compounds such as dimethyl sulfoxide and sulfolane; and sulfoxide compounds. The nonaqueous organic solvent may be used alone or in any combination and ratio of two or more depending on the application. Among these, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propionate, and ethyl propionate are particularly preferred from the viewpoints of electrochemical stability against oxidation-reduction, thermal stability, and chemical stability in the reaction with the difluorobis(oxalato)phosphate and tris(oxalato)phosphate (and tetrafluorooxalatophosphate and difluorophosphate that may further be contained).

[0020] The nonaqueous organic solvent may be, for example, a single solvent such as EMC, or a combination of one or more cyclic carbonates with high dielectric constants and one or more chain carbonates or chain esters with low liquid viscosity. Specifically, the following combinations may be used: (1) Combination of EC and EMC, (2) Combination of EC and DEC, (3) Combination of EC, DMC and EMC, (4) Combination of EC, DEC and EMC, (5) Combination of EC, EMC and EP, (6) Combination of PC and DEC, (7) Combination of PC and EMC, (8) Combination of PC and EP, (9) Combination of PC, DMC and EMC, (10) Combination of PC, DEC and EMC, (11) Combination of PC, DEC and EP, (12) Combination of PC, EC and EMC, (13) Combination of PC, EC, DMC and EMC, (14) Combination of PC, EC, DEC and EMC, (15) Combination of PC, EC, EMC and EP

[0021] [Method for Producing Nonaqueous Electrolyte] The method for producing a nonaqueous electrolyte according to the present disclosure is a method for producing a nonaqueous electrolyte by adding the nonaqueous solvent solution according to the present disclosure to a reference nonaqueous electrolyte solution containing a solute and a solvent for the nonaqueous electrolyte.

[0022] (Reference Non-Aqueous Electrolyte) The reference non-aqueous electrolyte contains a solute and a solvent for a non-aqueous electrolyte.

[0023] The solute is an ionic salt consisting of any pair of cation and anion, and is not particularly limited as long as it exists in an ionic state as a cation and an anion in a nonaqueous organic solvent, and various ionic salt solutes can be used. Specific examples of such ionic salt solutes include alkali metal ions such as lithium ion and sodium ion, alkaline earth metal ions, and quaternary ammonium ions as cations, and hexafluorophosphate, tetrafluoroboric acid, perchloric acid, hexafluoroarsenic acid, hexafluoroantimonic acid, and bis(fluorosulfonyl)imide as anions.

[0024] The ionic salt solutes in the present disclosure may be used singly or in any combination and ratio depending on the application. Among them, in consideration of the energy density, output characteristics, life, etc. of the battery, lithium, sodium, magnesium, quaternary ammonium, etc. are preferably used as the cation, and hexafluorophosphate, tetrafluoroborate, bis(fluorosulfonyl)imide, etc. are preferably used as the anion.

[0025] Specifically, the solute that is an ionic salt in the present disclosure may be at least one selected from the group consisting of hexafluorophosphates and tetrafluoroborates, or may be a combination of at least one selected from the group consisting of hexafluorophosphates and tetrafluoroborates with at least one selected from the group consisting of perchlorates, hexafluoroarsenates, hexafluoroantimonates, and bis(fluorosulfonyl)imide salts. The cation in the above specific example may be a lithium cation or a sodium cation.

[0026] The concentration of the ionic salt solute in the nonaqueous electrolyte solution of the present disclosure (hereinafter referred to as "solute concentration") is not particularly limited as long as it is a concentration that can fully exhibit the function of the ionic salt solute. For example, the lower limit may be 0.5 mol / L or more, preferably 0.7 mol / L or more, more preferably 0.9 mol / L or more, and the upper limit may be 5 mol / L or less, preferably 4 mol / L or less, more preferably 2 mol / L or less. A concentration of 0.5 mol / L or more is preferable because the ionic conductivity is less likely to decrease, and the cycle characteristics and output characteristics of the nonaqueous electrolyte battery are less likely to decrease. On the other hand, a concentration of 5 mol / L or less is preferable because the viscosity of the electrolyte solution for a nonaqueous electrolyte battery is less likely to increase, and the ionic conductivity is less likely to decrease. Note that when two or more types of ionic salt solutes are used, the total concentration of the solutes is preferably within the above-mentioned range.

[0027] The liquid temperature when dissolving the ionic salt solute in the nonaqueous organic solvent is not particularly limited, but is preferably -20 to 80°C, more preferably 0 to 60°C, for example.

[0028] Examples of the solvent for the non-aqueous electrolyte contained in the reference non-aqueous electrolyte include the same non-aqueous solvents as those described above.

[0029] The reference nonaqueous electrolyte solution is composed of the above-mentioned components as basic constituents, but other additives commonly used in this technical field may be added to the reference nonaqueous electrolyte solution of the present disclosure in any proportion, as long as the gist of the present disclosure is not impaired. When the nonaqueous electrolyte solution of the present disclosure contains other additives, the content thereof may be 0.01% by mass or more and 10% by mass or less, based on the total amount of the nonaqueous electrolyte solution. Other additives include, for example, cyclohexylbenzene, cyclohexylfluorobenzene, biphenyl, 2-fluorobiphenyl, t-butylbenzene, t-amylbenzene, 2-fluorotoluene, fluorobenzene, vinylene carbonate (hereinafter sometimes referred to as "VC"), vinylene carbonate oligomer (having a number average molecular weight of 170 to 5000 in terms of polystyrene), vinylethylene carbonate, difluoroanisole, fluoroethylene carbonate (hereinafter sometimes referred to as "FEC"), 1,6-diisocyanatohexane, ethynylethylene carbonate, trans-difluoroethylene carbonate, methylpropargyl carbonate, ethylpropargyl carbonate, dipropargyl carbonate, maleic anhydride, succinic anhydride, 1,3-propane sultone ... Lopensultone, butanesultone, dimethylvinylene carbonate, 1,3,2-dioxathiolane-2,2-dioxide, 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, methylenemethane disulfonate, dimethylmethane disulfonate, trimethylenemethane disulfonate, methyl methanesulfonate, methanesulfonyl fluoride, ethenesulfonyl fluoride, phenyl difluorophosphate, 1,2-ethanedisulfonic anhydride, trivinylmethylsilane, trivinylfluorosilane, tetravinylsilane, tris(trimethylsilyl)borate, succinonitrile, (ethoxy)pentafluorocyclotriphosphazene, tetrafluoro(picolinato)phosphate, difluoro(picolinato)borate, 1,3-dimethyl-1,3-divinyl-1,3-di(1,1,1,3,3,3-Hexafluoroisopropyl)disiloxane, lithium fluorosulfate, sodium fluorosulfate, lithium trifluoromethanesulfonate, sodium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, sodium nonafluorobutanesulfonate, lithium difluorooxalatoborate, sodium difluorooxalatoborate, lithium bis(oxalato)borate, sodium bis(oxalato)borate, lithium tetrafluorooxalatophosphate, sodium tetrafluorooxalatophosphate, lithium difluoro(malonato)borate, sodium difluoro(malonato)borate, lithium tetrafluoro(malonato)phosphate, sodium tetrafluoro(malonato)phosphate, lithium monofluorophosphate, sodium monofluorophosphate, lithium bis(difluorophosphoryl)imide, sodium bis(difluorophosphoryl)imide, lithium (difluorophosphoryl)(fluorosulfonyl)imide, sodium (difluorophosphoryl)(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, bis(trifluoromethanesulfonyl)imide Examples of the carboxylic acid salts include sodium tris(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethanesulfonyl)imide, sodium bis(pentafluoroethanesulfonyl)imide, lithium (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide, sodium (trifluoromethanesulfonyl)(pentafluoroethanesulfonyl)imide, sodium (trifluoromethanesulfonyl)(fluorosulfonyl)imide, sodium (trifluoromethanesulfonyl)(fluorosulfonyl)imide, lithium (pentafluoroethanesulfonyl)(fluorosulfonyl)imide, sodium tris(trifluoromethanesulfonyl)methide, sodium tris(trifluoromethanesulfonyl)methide, lithium acrylate, sodium acrylate, lithium methacrylate, sodium methacrylate, and other carboxylic acid salts; lithium methyl sulfate, sodium methyl sulfate, lithium ethyl sulfate, sodium ethyl sulfate, and other sulfate ester salts. ３ SO２ ) ２ , LiN (POF ２ ) ２ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , NaN(CF ３ SO ２ ) ２ , NaN(POF ２ ) ２ , NaCF ３ SO ３ , NaC ４ F ９ SO ３ The content of the nonaqueous electrolyte may be 0.01% by mass or more and 20% by mass or less relative to the total amount of the nonaqueous electrolyte. In addition, the electrolyte for a nonaqueous electrolyte battery may be quasi-solidified with a gelling agent or a crosslinked polymer and used, as in the case of use in a nonaqueous electrolyte battery called a lithium polymer battery.

[0030] The method for producing a nonaqueous electrolyte solution according to the present disclosure may further include a step of adding other additives.

[0031] The method for producing a nonaqueous electrolyte solution according to the present disclosure may include mixing a nonaqueous solvent solution, a solute, and a solvent for the nonaqueous electrolyte solution. In this case, the solute and the solvent for the nonaqueous electrolyte solution may be the same as those contained in the reference nonaqueous electrolyte solution. Furthermore, the method may include a step of adding other additives.

[0032] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to such examples.

[0033] Examples 1 to 8, Comparative Examples 1 to 4 Preparation of Concentrated Lithium Difluorobis(oxalato)phosphate Solution Ethyl methyl carbonate (EMC) and lithium difluorobis(oxalato)phosphate, each containing 10 ppm by mass or less of water, were dissolved in a fluororesin container (Flon Industries Co., Ltd., PFA container), to prepare a solution with a concentration of 25.1% by mass. Lithium tris(oxalato)phosphate, lithium tetrafluorooxalatophosphate, and lithium difluorophosphate were dissolved in this solution at the molar ratios (number of moles of each compound per mole of difluorobis(oxalato)phosphate) shown in Table 1. Water was added to this solution in an amount that would theoretically result in a water concentration of 700 ppm by mass, and the solution was maintained at 25°C for two weeks. Thereafter, the concentration of lithium difluorobis(oxalato)phosphate in the solution was adjusted to 100 ppm by mass. １９ The results are shown in Table 1.

[0034] In Table 1, LiDFBOP represents lithium difluorobis(oxalato)phosphate, LiP(Ox)3 represents lithium tris(oxalato)phosphate, LiTFOP represents lithium tetrafluorooxalatophosphate, and LiPO2F2 represents lithium difluorophosphate.

[0035]

[0036] The results in Table 1 show that when a certain amount or more of lithium tris(oxalato)phosphate is added, the decomposition of lithium difluorobis(oxalato)phosphate by water is suppressed.

[0037] According to the present disclosure, it is possible to provide a concentrated solution of difluorobis(oxalato)phosphate that exhibits excellent stability of the difluorobis(oxalato)phosphate even when water is mixed in. Furthermore, according to the present disclosure, it is possible to provide a method for producing a nonaqueous electrolyte solution using the concentrated solution of difluorobis(oxalato)phosphate.

[0038] Although the present 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 the present disclosure. This application is based on a Japanese patent application (Patent Application No. 2023-106166) filed on June 28, 2023, the contents of which are incorporated herein by reference.

Claims

1. A non-aqueous solvent solution comprising a non-aqueous solvent, a difluorobis(oxalato)phosphate, and a tris(oxalato)phosphate, wherein a concentration of the difluorobis(oxalato)phosphate in the non-aqueous solvent solution is 10 to 50 mass %, and a ratio of the difluorobis(oxalato)phosphate to the tris(oxalato)phosphate is 0.001 mole or more of the tris(oxalato)phosphate per mole of the difluorobis(oxalato)phosphate.

2. The non-aqueous solvent solution of claim 1, further comprising a tetrafluorooxalatophosphate salt.

3. The nonaqueous solvent solution according to claim 2, wherein the ratio of the difluorobis(oxalato)phosphate to the tetrafluorooxalatophosphate is 0.010 to 0.25 moles of the tetrafluorooxalatophosphate per mole of the difluorobis(oxalato)phosphate.

4. The non-aqueous solvent solution of claim 1, further comprising a difluorophosphate salt.

5. The nonaqueous solvent solution according to claim 4, wherein the ratio of said difluorobis(oxalato)phosphate to said difluorophosphate is 0.001 to 0.05 moles of said difluorophosphate per 1 mole of said difluorobis(oxalato)phosphate.

6. The nonaqueous solvent solution according to claim 4, further comprising a tetrafluorooxalatophosphate, wherein the ratio of the difluorobis(oxalato)phosphate, the tetrafluorooxalatophosphate and the difluorophosphate is 0.010 to 0.25 mol of the tetrafluorooxalatophosphate and 0.001 to 0.05 mol of the difluorophosphate per 1 mol of the difluorobis(oxalato)phosphate.

7. The nonaqueous solvent solution according to claim 1, wherein the ratio of said difluorobis(oxalato)phosphate to said tris(oxalato)phosphate is 1 mole of said difluorobis(oxalato)phosphate to 0.03 moles or less of said tris(oxalato)phosphate.

8. The non-aqueous solvent solution of claim 1, wherein the non-aqueous solvent comprises at least one of a cyclic ester and a chain ester.

9. The non-aqueous solvent solution according to claim 8, wherein the content of the chain ester is 50 to 100% by volume relative to the total amount of the non-aqueous solvent.

10. The nonaqueous solvent solution according to claim 8, wherein the cyclic ester is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, and γ-butyrolactone, and the chain ester is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate.

11. A method for producing a nonaqueous electrolyte, comprising adding the nonaqueous solvent solution according to any one of claims 1 to 10 to a reference nonaqueous electrolyte solution containing a solute and a solvent for the nonaqueous electrolyte.

12. The method for producing a non-aqueous electrolyte according to claim 11, wherein the reference non-aqueous electrolyte contains other additives.

13. The method for producing a non-aqueous electrolyte solution according to claim 11, further comprising the step of adding other additives.

14. A method for producing a non-aqueous electrolyte, comprising mixing the non-aqueous solvent solution according to any one of claims 1 to 10, a solute, and a solvent for the non-aqueous electrolyte.

15. The method for producing a non-aqueous electrolyte according to claim 14, further comprising the step of adding other additives.

16. The other additives are difluoro(oxalato)borate, bis(oxalato)borate, fluorosulfonate, bis(trifluoromethanesulfonyl)imide salt, bis(fluorosulfonyl)imide salt, (trifluoromethanesulfonyl)(fluorosulfonyl)imide salt, bis(difluorophosphoryl)imide salt, (difluorophosphoryl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(trifluoromethanesulfonyl)imide salt, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate, vinylene carbonate oligomer (number average molecular weight 170 to 5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynyl ethylene carbonate, ethyl ... ethylene carbonate, trans-difluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane-2,2-dioxide, 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, methylenemethane disulfonate, 1,2-ethane disulfonic anhydride, tris(trimethylsilyl)borate, succinonitrile, adiponitrile, (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. The method for producing a non-aqueous electrolyte according to claim 13, which is at least one selected from the group consisting of disiloxane.

17. The other additives are difluoro(oxalato)borate, bis(oxalato)borate, fluorosulfonate, bis(trifluoromethanesulfonyl)imide salt, bis(fluorosulfonyl)imide salt, (trifluoromethanesulfonyl)(fluorosulfonyl)imide salt, bis(difluorophosphoryl)imide salt, (difluorophosphoryl)(fluorosulfonyl)imide salt, (difluorophosphoryl)(trifluoromethanesulfonyl)imide salt, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, fluorobenzene, vinylene carbonate, vinylene carbonate oligomer (number average molecular weight is 170 to 5000), vinylethylene carbonate, fluoroethylene carbonate, 1,6-diisocyanatohexane, ethynyl ethylene carbonate, ethyl ... ethylene carbonate, trans-difluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane-2,2-dioxide, 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, methylenemethane disulfonate, 1,2-ethane disulfonic anhydride, tris(trimethylsilyl)borate, succinonitrile, adiponitrile, (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. The method for producing a non-aqueous electrolyte according to claim 15, which is at least one selected from the group consisting of tetrafluoroethylene carbonate, trans-difluoroethylene carbonate, 1,3-propane sultone, 1,3,2-dioxathiolane-2,2-dioxide, 4-propyl-1,3,2-dioxathiolane-2,2-dioxide, methylenemethane disulfonate, 1,2-ethane disulfonic anhydride, tris(trimethylsilyl)borate, succinonitrile, adiponitrile, (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.

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