Method for producing non-aqueous electrolyte

Abstract

A method for producing a nonaqueous electrolyte solution that contains a sulfonylimide compound represented by general formula (1) and an electrolyte solution solvent (B), the method comprising: a preparation step for preparing a sulfonylimide solution that contains the sulfonylimide compound represented by general formula (1) and an electrolyte solution solvent (A) that is different from the electrolyte solution solvent (B); and a fractional distillation step for removing the electrolyte solution solvent (A) by distillation by adding the electrolyte solution solvent (B) into the sulfonylimide solution that has been obtained in the preparation step. (1): LiN(RSO2)(FSO2) (In the formula, R represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.)

Description

[Technical field]

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

[0002] In order to improve the battery performance of secondary batteries such as lithium ion secondary batteries, various nonaqueous electrolytes and materials thereof used in secondary batteries have been studied. For example, Patent Document 1 proposes a method for producing an electrolyte material containing a specific fluorosulfonylimide salt and an electrolyte solvent. In this production method, a solution containing a specific fluorosulfonylimide salt and an electrolyte solvent is reduced in pressure and / or heated to volatilize the production solvent of the fluorosulfonylimide salt, thereby obtaining an electrolyte material with reduced residual solvent that affects the properties of the electrolyte material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 052752 Summary of the Invention [Problem to be solved by the invention]

[0004] However, users, including battery manufacturers, may use different electrolyte solvents, and therefore if the electrolyte solvent used in the production of the nonaqueous electrolyte can be replaced with another electrolyte solvent specified by the user without going through a complicated process such as an extraction process, this would be advantageous in that users would have more options for the nonaqueous electrolyte or its material.

[0005] The present disclosure has been made in consideration of the above points, and an object of the present disclosure is to provide a method for producing a nonaqueous electrolyte solution that enables the electrolyte solvent used in producing the nonaqueous electrolyte solution to be replaced with another electrolyte solvent without going through a complicated process such as an extraction process. [Means for solving the problem]

[0006] In order to achieve the above object, in this disclosure, two kinds of electrolyte solvents are used, and after preparing a solution containing a first electrolyte solvent in advance, the first electrolyte solvent is replaced with a second electrolyte solvent, that is, solvent replacement is performed.

[0007] The method for producing a nonaqueous electrolyte solution according to the present disclosure comprises the steps of: LiN(RSO 2 )(FSO 2 (R represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.) (1) and an electrolyte solvent (B), the method comprising: a preparation step of preparing a sulfonylimide solution containing the sulfonylimide compound represented by general formula (1) and an electrolyte solvent (A) different from the electrolyte solvent (B); and a fractional distillation step of adding the electrolyte solvent (B) to the sulfonylimide solution obtained in the preparation step and distilling off the electrolyte solvent (A).

[0008] In the manufacturing method, the boiling point difference between the electrolyte solvent (A) and the electrolyte solvent (B) may be 60°C or more and 300°C or less. The electrolyte solvent (A) may be a solvent having a boiling point of 60°C or more. The electrolyte solvent (B) may be a solvent having a boiling point of 200°C or more. The electrolyte solvent (A) and the electrolyte solvent (B) may be at least one selected from the group consisting of carbonate-based solvents and ester-based solvents. The electrolyte solvent (A) may be at least one selected from the group consisting of chain carbonate-based solvents and chain ester-based solvents. The electrolyte solvent (B) may be at least one selected from the group consisting of cyclic carbonate-based solvents and cyclic ester-based solvents. The water content in the nonaqueous electrolyte may be 10000 mass ppm or less. In the preparation step, the electrolyte solvent (A) may be added to a sulfonylimide aqueous solution containing the sulfonylimide compound represented by the general formula (1) to dehydrate it. The amount of the electrolyte solvent (A) remaining in the non-aqueous electrolyte may be 20% by mass or less relative to 100% by mass of the non-aqueous electrolyte. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a method for producing a nonaqueous electrolyte solution or a material thereof, which enables the electrolyte solvent used in producing the nonaqueous electrolyte solution to be replaced with another electrolyte solvent without going through a complicated process such as an extraction process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present embodiment will be described in detail below. The following description of the preferred embodiment is merely exemplary in nature and is not intended to limit the present invention, its application, or its uses.

[0011] [Method of manufacturing non-aqueous electrolyte] The method for producing a non-aqueous electrolyte according to this embodiment is a method for producing a non-aqueous electrolyte containing a specific sulfonylimide compound and an electrolyte solvent (B) by replacing an electrolyte solvent with a sulfonylimide solution containing the specific sulfonylimide compound and an electrolyte solvent (A) described later. The electrolyte solvent (B) is different from the electrolyte solvent (A). This production method includes at least a preparation step of preparing a sulfonylimide solution, and a fractionation step of adding the electrolyte solvent (B) to the sulfonylimide solution to replace the electrolyte solvent (A) with the electrolyte solvent (B).

[0012] <Preparation process> (Sulfonylimide compounds) The preparation step is a step of preparing a sulfonylimide solution. The sulfonylimide solution is a sulfonylimide solution represented by the general formula (1): [C1] LiN(RSO 2 )(FSO 2 ) (1) The compound contains a sulfonylimide compound represented by the following formula (hereinafter referred to as "sulfonylimide compound (1)" and a fluorine-containing sulfonylimide salt).

[0013] The sulfonylimide compound (1) is an electrolyte for a non-aqueous electrolyte solution obtained by the production method according to this embodiment. In the general formula (1), R represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.

[0014] Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group. Among the alkyl groups having 1 to 6 carbon atoms, a linear or branched alkyl group having 1 to 6 carbon atoms is preferred, and a linear alkyl group having 1 to 6 carbon atoms is more preferred.

[0015] Examples of the fluoroalkyl group having 1 to 6 carbon atoms include an alkyl group having 1 to 6 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms. Examples of the fluoroalkyl group having 1 to 6 carbon atoms include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, and a pentafluoroethyl group. In particular, the fluoroalkyl group may be a perfluoroalkyl group.

[0016] The substituent R is preferably a fluorine atom or a perfluoroalkyl group (for example, a perfluoroalkyl group having 1 to 6 carbon atoms, such as a trifluoromethyl group, a pentafluoroethyl group, or a heptafluoropropyl group), more preferably a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group, still more preferably a fluorine atom or a trifluoromethyl group, and even more preferably a fluorine atom.

[0017] Specific examples of the sulfonylimide compound (1) include lithium bis(fluorosulfonyl)imide (LiN(FSO 2 ) 2 , LiFSI), lithium (fluorosulfonyl) (methylsulfonyl) imide, lithium (fluorosulfonyl) (ethylsulfonyl) imide, lithium (fluorosulfonyl) (trifluoromethylsulfonyl) imide, lithium (fluorosulfonyl) (pentafluoroethylsulfonyl) imide, lithium (fluorosulfonyl) (heptafluoropropylsulfonyl) imide, etc. The sulfonylimide compounds may be used alone or in combination of two or more kinds.

[0018] Among the sulfonylimide compounds (1), from the viewpoint of improving the battery performance, lithium bis(fluorosulfonyl)imide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, and lithium (fluorosulfonyl)(pentafluoroethylsulfonyl)imide are preferred, and lithium bis(fluorosulfonyl)imide is more preferred. In other words, in the sulfonylimide solution, the sulfonylimide compound (1) is LiN(FSO2 ) 2 It is preferred that the compound contains

[0019] The sulfonylimide compound (1) may be a commercially available product or may be synthesized by a conventionally known method. The method for synthesizing the sulfonylimide compound (1) is not particularly limited, and any conventionally known method may be used. For example, methods described in WO 2011 / 149095, JP 2014-201453 A, JP 2010-168249 A, JP 2010-168308 A, JP 2010-189372 A, WO 2011 / 065502 A, JP-T-8-511274 A, WO 2012 / 108284 A, WO 2012 / 117961 A, WO 2012 / 118063 A, JP 2010-280586 A, JP 2010-254543 A, JP 2007-182410 A, WO 2010 / 010613 A, etc. can be mentioned. By the above-mentioned conventionally known method, a powder (solid) of the sulfonylimide compound (1) can be obtained.

[0020] The sulfonylimide compound (1) may contain a production solvent used in the production of the sulfonylimide compound (1) (a residual solvent contained in the sulfonylimide compound (1) obtained by the above-mentioned conventionally known production method) within the range that does not impair the object of the present invention. The residual solvent is a solvent used in the production reaction of the sulfonylimide compound (1) or a solvent used in the purification step. For example, water; alcohol-based solvents such as methanol, ethanol, propanol, and butanol; carboxylic acid-based solvents such as formic acid and acetic acid; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; nitrile-based solvents such as isobutyronitrile, acetonitrile, valeronitrile, and benzonitrile; ester-based solvents such as ethyl acetate, isopropyl acetate, and butyl acetate; aliphatic ether-based solvents such as diethyl ether, diisopropyl ether, t-butyl methyl ether, and cyclopentyl methyl ether; halogen-based solvents such as HF; nitro group-containing solvents such as nitromethane and nitrobenzene; nitrogen-containing organic solvents such as ethylformamide and N-methylpyrrolidone; dimethyl sulfoxide; glyme-based solvents, toluene, o-xylene, m-xylene, p-xylene, benzene, ethylbenzene, isopropylbenzene, 1,2,3 aromatic hydrocarbon solvents such as 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, tetralin, cymene, methylethylbenzene, 2-ethyltoluene, chlorobenzene, and dichlorobenzene; pentane, hexane, heptane, octane, decane, dodecane, undecane, tridecane, decalin, 2,2,4,6,6-pentamethylheptane, isoparaffin (e.g., "Marukasol R" (a mixture of 2,2,4,6,6-pentamethylheptane and 2,2,4,4,6-pentamethylheptane manufactured by Maruzen Petrochemical Co., Ltd.), "Isopar (registered trademark) G" (a C9-C11 mixed isoparaffin manufactured by ExxonMobil), and "Isopar (registered trademark) E" (a C8-C10 mixed isoparaffin manufactured by ExxonMobil), dichloromethane, chloroform, 1,2-dichloroethane, and other chain aliphatic hydrocarbon solvents;Cycloaliphatic hydrocarbon solvents such as cyclohexane, methylcyclohexane, 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, ethylcyclohexane, 1,2,4-trimethylcyclohexane, 1,3,5-trimethylcyclohexane, propylcyclohexane, butylcyclohexane, and "Swaclean 150" (a mixture of C9 alkylcyclohexanes manufactured by Maruzen Petrochemical Co., Ltd.); aromatic ether solvents such as anisole, 2-methylanisole, 3-methylanisole, and 4-methylanisole; ethylene carbonate, propylene carbonate, etc. Examples of the solvent include carbonate-based solvents such as butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; chain ether-based solvents such as dimethoxymethane and 1,2-dimethoxyethane; cyclic ether-based solvents such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, and 4-methyl-1,3-dioxolane; cyclic ester-based solvents such as γ-butyrolactone and γ-valerolactone; sulfolane-based solvents such as sulfolane and 3-methylsulfolane; N,N-dimethylformamide, dimethyl sulfoxide, and N-methyloxazolidinone.

[0021] (Electrolyte Solvent (A)) The sulfonylimide solution contains an electrolyte solvent (A) together with the sulfonylimide compound (1). The electrolyte solvent (A) is capable of dissolving and dispersing an electrolyte. As the electrolyte solvent (A), a non-aqueous solvent having a large dielectric constant, high solubility of an electrolyte salt, a boiling point at normal pressure of 60° C. or more, and a wide electrochemically stable range is preferable. An organic solvent having a low water content is more preferable. Examples of such an electrolyte solvent (A) include chain carbonate ester (carbonate) solvents such as dimethyl carbonate (DMC, boiling point: 90° C.), ethyl methyl carbonate (EMC, boiling point: 107° C.), and diethyl carbonate (DEC, boiling point: 125.8° C.); and chain ester solvents such as ethyl propionate (boiling point: 99° C.) and propyl propionate (boiling point: 124° C.). These solvents may be used alone or in combination of two or more. Of the electrolyte solvents (A), from the viewpoint of reducing the amount of electrolyte solvent (A) remaining in the non-aqueous electrolyte, at least one selected from the group consisting of chain carbonate solvents and chain ester solvents is preferred, with dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl propionate and propyl propionate being more preferred, and dimethyl carbonate, ethyl methyl carbonate and ethyl propionate being even more preferred.

[0022] (Method for preparing sulfonylimide solution) The method for preparing the sulfonylimide solution is not particularly limited, and may include, for example, a method for dissolving a powder (solid) of the sulfonylimide compound (1) in the electrolyte solvent (A); a method for synthesizing the sulfonylimide compound (1) in the electrolyte solvent (A) (for example, a method in which the electrolyte solvent (A) is used instead of butyl acetate in Production Example 1 described in International Publication No. 2016 / 052752 (Patent Document 1)); a method for dissolving HFSI (bis(fluorosulfonyl)imide) and LiOH or Li in the electrolyte solvent (A). 2 CO 3 and the like.

[0023] As another method for preparing the sulfonylimide solution, a sulfonylimide solution may be prepared by first preparing an aqueous sulfonylimide solution containing the sulfonylimide compound (1) and then dehydrating the resulting aqueous sulfonylimide solution to replace the solvent.

[0024] The method for preparing the sulfonylimide aqueous solution is not particularly limited, and includes, for example, a method of dissolving the powder (solid) of the sulfonylimide compound (1) in water; a method of dissolving water, LiOH or Li 2 CO 3 and a method of mixing and reacting a lithium salt such as HFSI (bis(fluorosulfonyl)imide) (preparation of an aqueous LiFSI solution).

[0025] The sulfonylimide compound (1) concentration in the aqueous sulfonylimide solution is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, from the viewpoint of dehydration efficiency. The upper limit of the concentration is preferably 70% by mass or less, from the viewpoint of dehydration efficiency.

[0026] The method for dehydrating the aqueous sulfonylimide solution to replace the solvent is not particularly limited, and examples thereof include a method for dehydrating a solution obtained by adding an electrolyte solvent (A) to an aqueous sulfonylimide solution (a solution for carrying out an operation of dehydrating and replacing with an electrolyte solvent (A), hereinafter also referred to as a "hydrous sulfonylimide solution for dehydration").

[0027] For example, the same amount of electrolyte solvent (A) as the distillate to be removed from the distillate obtained by azeotropic distillation of the water contained in the dehydrating hydrous sulfonylimide solution and the added electrolyte solvent (A) may be continuously added; the distillate may be phase-separated to remove the aqueous layer while refluxing the organic phase. By these operations (dehydration step), the dehydrating hydrous sulfonylimide solution is dehydrated to obtain a sulfonylimide solution containing the added electrolyte solvent (A). In the dehydration step, the water in the sulfonylimide aqueous solution is replaced by the added electrolyte solvent (A), resulting in a solution with a sufficiently reduced water content. The sulfonylimide solution contains the sulfonylimide compound (1) and the electrolyte solvent (A) as electrolytes, and may be used as it is as a nonaqueous electrolyte, or may be used as a raw material for a nonaqueous electrolyte (electrolyte solution, electrolyte material).

[0028] The amount of the electrolyte solvent (A) added (used) is not particularly limited in terms of the lower limit, and may be appropriately adjusted depending on the type and amount of the residual solvent in the sulfonylimide compound (1). For example, the amount is preferably 10,000 g or less, more preferably 1,000 g or less, even more preferably 500 g or less, still more preferably 200 g or less, even more preferably 100 g or less, and particularly preferably 50 g or less, relative to 100 g of the sulfonylimide compound (1).

[0029] The amount of the electrolyte solvent (A) added (used) is, for example, preferably 1 to 1,000 parts by mass, more preferably 5 to 500 parts by mass, even more preferably 10 to 300 parts by mass, still more preferably 30 to 200 parts by mass, and even more preferably 50 to 100 parts by mass, relative to 100 parts by mass of the sulfonylimide compound (1).

[0030] The dehydration step can be carried out under either normal pressure or reduced pressure (normal pressure and reduced pressure may be combined during the dehydration step), but is preferably carried out under reduced pressure from the viewpoint of suppressing thermal deterioration of the sulfonylimide solution caused by thermal decomposition of the sulfonylimide compound (1). The degree of reduced pressure may be appropriately adjusted depending on the concentration of the sulfonylimide compound (1), the type and amount of the electrolyte solvent (A), etc., and is not particularly limited, but is, for example, preferably 200 kPa or less, more preferably 40 kPa or less, even more preferably 15 kPa or less, and particularly preferably 10 kPa or less.

[0031] The heating temperature in the dehydration step is not particularly limited and may be appropriately adjusted depending on the degree of reduced pressure, the type and amount of the electrolyte solvent (A), etc., but a relatively low temperature is preferable from the viewpoint of suppressing thermal deterioration of the aqueous sulfonylimide solution caused by the decomposition of the sulfonylimide compound (1) by heat. The heating temperature is, for example, preferably 10 to 110°C, more preferably 15 to 100°C.

[0032] The treatment time in the dehydration step may be appropriately adjusted depending on the degree of reduced pressure, heating temperature, the type and amount of the electrolyte solvent (A), etc., and is not particularly limited; for example, the treatment time is preferably 0.1 to 24 hours, more preferably 0.5 to 12 hours, even more preferably 1 to 8 hours, and particularly preferably 2 to 5 hours.

[0033] The apparatus capable of reducing pressure and / or heating used in the dehydration step may be appropriately selected depending on the amount of solution, the degree of reduced pressure, the heating temperature, etc. Examples include a tank-type reactor, a tank-type reactor capable of reducing pressure, etc.

[0034] In the preparation process, a carbonate may be added to the sulfonylimide solution and / or the aqueous sulfonylimide solution within the range that does not impair the object of the present invention. When preparing the sulfonylimide solution and / or the aqueous sulfonylimide solution, a small amount of fluorosulfonic acid (HFSO 3 In addition, depending on the method for producing the sulfonylimide compound (1), the sulfonylimide compound (1) itself may contain HFSO. 3May also contain HFSO. 3 is a cause of deterioration of the aqueous sulfonylimide solution due to decomposition of the sulfonylimide compound (1), so the sulfonylimide solution and / or HFSO in the aqueous sulfonylimide solution should be avoided. 3 It is desirable to trap the carbon dioxide with carbonate.

[0035] The carbonate salt is lithium carbonate (Li 2 CO 3 ), Sodium Carbonate (Na 2 CO 3 ), potassium carbonate (K 2 CO 3 ), rubidium carbonate (Rb 2 CO 3 ), Cesium carbonate (Cs 2 CO 3 ) and other alkali metal carbonates; beryllium carbonate (BeCO 3 ), Magnesium carbonate (MgCO 3 ), calcium carbonate (CaCO 3 ), strontium carbonate (SrCO 3 ), barium carbonate (BaCO 3 ) and other alkaline earth metal carbonates; ammonium carbonate (NH 4 ) 2 CO 3 ); Copper(II) carbonate (CuCO 3 ); Iron(II) carbonate (FeCO 3 );Silver(I) carbonate(Ag 2 CO 3 The carbonates may be used alone or in combination of two or more kinds.

[0036] Among carbonates, HFSO 3 From the viewpoint of reliably trapping, alkali metal carbonates and alkaline earth metal carbonates are preferred, alkali metal carbonates are more preferred, and Li 2 CO 3 , Na 2 CO 3 , K 2 CO 3 , and Cs 2 CO 3 is more preferred, Li2 CO 3 is even more preferred.

[0037] The amount of carbonate to be added to the aqueous sulfonylimide solution may be appropriately determined depending on the concentration of the sulfonylimide compound (1). 3 From the viewpoint of reliably trapping, the amount is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, based on 100% by mass of the aqueous sulfonylimide solution. From the viewpoint of reducing the amount of insoluble particles of carbonate remaining in the aqueous sulfonylimide solution, the upper limit of the amount added is preferably 1% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.5% by mass or less, based on 100% by mass of the aqueous sulfonylimide solution.

[0038] (Sulfonylimide solution) The concentration of the sulfonylimide compound (1) in the sulfonylimide solution is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more from the viewpoint of improving storage stability, and is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less from the viewpoint of suppressing a decrease in battery performance due to an increase in the viscosity of the electrolyte.

[0039] The water content (water concentration) in the sulfonylimide solution is preferably 10000 mass ppm or less, more preferably 1000 mass ppm or less, even more preferably 100 mass ppm or less, and even more preferably 50 mass ppm or less, from the viewpoint of suppressing decomposition of the sulfonylimide compound (1) by water. The lower the water content, the more preferable it is, and it may be below the detection limit or substantially absent (0 mass ppm). The water content can be measured by the method described in the Examples below, for example, using a Karl Fischer water content meter or the like.

[0040] <Fractional distillation process> The fractional distillation step is a step of fractionally distilling the electrolyte solvent (A) and the electrolyte solvent (B) in the mixture obtained by adding the electrolyte solvent (B) to the sulfonylimide solution obtained in the preparation step. In this fractional distillation step, a mixture containing the sulfonylimide solution and the electrolyte solvent (B), that is, a liquid mixture containing the sulfonylimide compound (1) and two electrolyte solvents (A) and (B) with different boiling points, is heated, and a fractional distillation operation is performed to vaporize and separate (remove) the electrolyte solvent (A) with a lower boiling point. By this operation, the electrolyte solvent (A) in the sulfonylimide solution is replaced by the electrolyte solvent (B) added to the solution. As a result, the amount of the electrolyte solvent (A) is reduced, and a nonaqueous electrolyte containing more electrolyte solvent (B) than electrolyte solvent (A) is obtained.

[0041] (Electrolyte Solvent (B)) The electrolyte solvent (B) is capable of dissolving and dispersing the electrolyte. As the electrolyte solvent (B), a non-aqueous solvent having a large dielectric constant, high solubility of electrolyte salt, a boiling point of 60° C. or higher at normal pressure, and a wide electrochemical stability range is preferable. An organic solvent having a low water content is more preferable.

[0042] In addition, the electrolyte solvent (B) is a solvent having a different boiling point from the electrolyte solvent (A). Specifically, the electrolyte solvent (B) has a higher boiling point than the electrolyte solvent (A), and a combination in which the boiling point difference between the two is large is preferable. The larger the boiling point difference between the two, the higher the fractional distillation efficiency, and the electrolyte solvent (A) in the mixture is reduced, and a nonaqueous electrolyte containing the desired electrolyte solvent (B) is obtained. The boiling point difference between the electrolyte solvent (A) and the electrolyte solvent (B) is preferably 60°C or more, more preferably 80°C or more, even more preferably 100°C or more, and even more preferably 130°C or more, from the viewpoint of reducing the remaining amount of the electrolyte solvent (A) in the nonaqueous electrolyte. In addition, the upper limit of the boiling point difference is preferably 300°C or less, more preferably 200°C or less, even more preferably 190°C or less, even more preferably 180°C or less, even more preferably 170°C or less, and particularly preferably 160°C or less.

[0043] Examples of such electrolyte solvents (B) include solvents having a boiling point of 200° C. or higher at normal pressure. Specific examples include saturated cyclic carbonate ester (carbonate) solvents such as ethylene carbonate (EC, boiling point: 244° C.), propylene carbonate (PC, boiling point: 242° C.), 2,3-dimethylethylene carbonate (boiling point: 313° C.), 1,2-butylene carbonate (boiling point: 250° C.), and erythritan carbonate (boiling point: 345° C.); and cyclic ester solvents such as γ-butyrolactone (boiling point: 204° C.). These solvents may be used alone or in combination of two or more. Among the electrolyte solvents (B), from the viewpoint of reducing the amount of electrolyte solvent (A) remaining in the nonaqueous electrolyte, at least one selected from the group consisting of cyclic carbonate solvents and cyclic ester solvents is preferred, and ethylene carbonate, propylene carbonate, and γ-butyrolactone are preferred.

[0044] Thus, the electrolyte solvent (A) and the electrolyte solvent (B) are preferably at least one selected from the group consisting of carbonate-based solvents and ester-based solvents, and both are preferably carbonate-based solvents or ester-based solvents. When both are carbonate-based solvents, more preferably, the electrolyte solvent (A) is a chain carbonate-based solvent, and the electrolyte solvent (B) is a cyclic carbonate-based solvent. When both are ester-based solvents, more preferably, the electrolyte solvent (A) is a chain ester-based solvent, and the electrolyte solvent (B) is a cyclic ester-based solvent. When a cyclic carbonate-based solvent or a cyclic ester-based solvent is used during the production of the sulfonylimide compound (1), it is relatively difficult to reduce the amount of water mixed into the sulfonylimide compound (1) during the production. Therefore, when the sulfonylimide compound (1) is produced, the amount of water in the sulfonylimide compound (1) is sufficiently reduced by using a chain carbonate solvent or a chain ester solvent, and then the chain carbonate solvent or the chain ester solvent is replaced with a cyclic carbonate solvent or a cyclic ester solvent, thereby obtaining a nonaqueous electrolyte solution with a low water content. The water mixed into the sulfonylimide compound (1) during production can be, for example, LiOH or Li 2 CO 3Examples of water that may be used include water generated in the neutralization reaction between a lithium salt such as the above and HFSI, water used as a reaction solvent, and water from the extraction process.

[0045] The amount of electrolyte solvent (B) added (used) is not particularly limited in terms of the lower limit, and may be appropriately adjusted depending on the type and amount of electrolyte solvent (A), etc. For example, the amount is preferably 10,000 g or less, more preferably 1,000 g or less, even more preferably 500 g or less, still more preferably 200 g or less, even more preferably 100 g or less, and particularly preferably 50 g or less, relative to 100 g of sulfonylimide compound (1).

[0046] The amount of the electrolyte solvent (B) added (used) is, for example, preferably 1 to 1,000 parts by mass, more preferably 5 to 500 parts by mass, even more preferably 10 to 300 parts by mass, still more preferably 30 to 200 parts by mass, and even more preferably 50 to 100 parts by mass, relative to 100 parts by mass of the sulfonylimide compound (1).

[0047] The amount of electrolyte solvent (B) added (used) is, for example, preferably 10,000 g or less, more preferably 1,000 g or less, even more preferably 500 g or less, still more preferably 200 g or less, and even more preferably 100 g or less, relative to 100 g of the sulfonylimide solution containing the sulfonylimide compound (1) and the electrolyte solvent (A).

[0048] (Fractional distillation method) The method for distilling off the electrolyte solvent (A) from the liquid mixture obtained by adding the electrolyte solvent (B) to the sulfonylimide solution (fractionally distilling the electrolyte solvent (A) and the electrolyte solvent (B)) is not particularly limited, and any conventionally known method can be used. For example, a method of reducing pressure and / or heating the liquid mixture can be used.

[0049] The fractional distillation step can be carried out under either normal pressure or reduced pressure (normal pressure and reduced pressure may be combined during the fractional distillation step), but it is preferable to carry out the fractional distillation step under reduced pressure in order to suppress thermal deterioration of the aqueous sulfonylimide solution caused by the decomposition of the sulfonylimide compound (1) by heat. The degree of reduced pressure may be appropriately adjusted according to the concentration of the sulfonylimide compound (1), the type and amount of the electrolyte solvent (A) and the electrolyte solvent (B), and is not particularly limited, but is preferably 200 kPa or less, more preferably 40 kPa or less, even more preferably 15 kPa or less, even more preferably 10 kPa or less, and even more preferably 5 kPa or less. The degree of reduced pressure may be constant (the same) during the fractional distillation step, or may be changed midway. For example, after the electrolyte solvent (A) is distilled off at a first reduced pressure, the pressure may be reduced to a second reduced pressure lower than the first reduced pressure to further distill off the electrolyte solvent (A).

[0050] The heating temperature in the fractional distillation step is not particularly limited and may be appropriately adjusted depending on the degree of reduced pressure, the types and amounts of the electrolyte solvent (A) and the electrolyte solvent (B), etc., but a relatively low temperature is preferable from the viewpoint of suppressing thermal deterioration of the aqueous sulfonylimide solution caused by the decomposition of the sulfonylimide compound (1) by heat. The heating temperature is, for example, preferably 10 to 110°C, more preferably 15 to 100°C, and even more preferably 20 to 80°C.

[0051] The treatment time in the fractional distillation step may be appropriately adjusted depending on the degree of reduced pressure, heating temperature, the types and amounts of the electrolyte solvent (A) and the electrolyte solvent (B), and is not particularly limited. For example, the treatment time is preferably 0.1 to 24 hours, more preferably 0.2 to 12 hours, even more preferably 0.5 to 8 hours, and particularly preferably 0.5 to 5 hours.

[0052] The apparatus capable of reducing pressure and / or heating used in the fractional distillation step may be appropriately selected depending on the amount of solution, the degree of reduced pressure, the heating temperature, etc. Examples include a tank-type reactor, a tank-type reactor capable of reducing pressure, etc.

[0053] <Other processes> The method for producing the non-aqueous electrolyte may include other steps as long as they do not impair the object of the present invention. Examples of the other steps include filtration, column purification, activated carbon treatment, and molecular sieve treatment.

[0054] Through the above steps (operations), a non-aqueous electrolyte solution containing the sulfonylimide compound (1) and the electrolyte solvent (B) is obtained by solvent replacement from the sulfonylimide solution containing the sulfonylimide compound (1) and the electrolyte solvent (A). This non-aqueous electrolyte solution has a lower water content than non-aqueous electrolyte solutions obtained by conventional methods.

[0055] When the sulfonylimide solution is prepared using an aqueous sulfonylimide solution containing the sulfonylimide compound (1), a nonaqueous electrolyte solution with a lower water content can be obtained by adding an electrolyte solvent (A) to the aqueous solution and dehydrating the solution. That is, the method for producing a nonaqueous electrolyte solution may further include, before the preparation step (second preparation step) of preparing a sulfonylimide solution, a preparation step (first preparation step) of preparing an aqueous sulfonylimide solution, and a dehydration step of adding an electrolyte solvent (A) to the aqueous sulfonylimide solution obtained in the first preparation step, dehydrating the aqueous sulfonylimide solution, and replacing it with the electrolyte solvent (A).

[0056] [Nonaqueous electrolyte] (electrolyte) The electrolyte (non-aqueous electrolyte) may contain the sulfonylimide compound (1), but may also contain other electrolytes (electrolytes other than the sulfonylimide compound (1)). The other electrolytes may be mixed into the non-aqueous electrolyte, or may be mixed into the sulfonylimide solution and / or the sulfonylimide aqueous solution in the preparation process of the non-aqueous electrolyte. Examples of the other electrolytes include imide salts and non-imide salts.

[0057] Examples of the imide salt include fluorine-containing sulfonylimide salts (hereinafter referred to as "other sulfonylimide compounds") other than the sulfonylimide compound (1). Examples of the other sulfonylimide compounds include lithium bis(trifluoromethylsulfonyl)imide (LiN(CF 3 SO 2 )2 , hereinafter also referred to as "LiTFSI"); lithium bis(pentafluoroethylsulfonyl)imide; lithium bis(heptafluoropropylsulfonyl)imide; non-lithium salts of the fluorine-containing sulfonylimides listed as sulfonylimide compound (1) (for example, salts in which lithium (ion) in sulfonylimide compound (1) is replaced with a cation other than lithium ion), etc. Examples of salts in which a cation other than lithium ion is replaced include alkali metal salts such as sodium salts, potassium salts, rubidium salts, and cesium salts; alkaline earth metal salts such as beryllium salts, magnesium salts, calcium salts, strontium salts, and barium salts; aluminum salts; ammonium salts; and phosphonium salts. The other sulfonylimide compounds may be used alone or in combination of two or more kinds. In addition, the other sulfonylimide compounds may be commercially available products, or may be obtained by synthesis using a conventionally known method.

[0058] Examples of the non-imide salt include salts of non-imide anions and cations (lithium ions and the above-listed cations). 6 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 , LiPF 3 (C 3 F 7 ) 3 , LiPF 3 (C 4 F 9 ) 3 Fluorophosphate compounds such as LiBF 4 , LiBF(CF 3 ) 3 , LiBF(C 2 F 5 ) 3 , LiBF(C 3 F 7 ) 3 Fluoroborate compounds such as lithium hexafluoroarsenate (LiAsF 6 ), LiSbF 6, LiClO 4 , LiSCN, LiAlF 4 , C.F. 3 SO 3 Li, LiC[(CF 3 SO 2 ) 3 ], LiN(NO 2 ), LiN[(CN) 2 Lithium salts such as those mentioned above; non-lithium salts (for example, salts in which the lithium (ion) in these lithium salts is replaced with the above-mentioned cations (for example, NaBF 4 , NaPF 6 , NaPF 3 (CF 3 ) 3 The non-imide salts may be used alone or in combination of two or more. In addition, the non-imide salts may be commercially available products or may be synthesized by a conventional method.

[0059] These electrolytes (sulfonylimide compound (1), other electrolytes, etc.) may be present (contained) in the form of ions in the nonaqueous electrolyte.

[0060] The concentration (content, total content when two or more kinds are used in combination, the same applies below) of the sulfonylimide compound (1) in the nonaqueous electrolyte is preferably 30% by mass or more based on the entire nonaqueous electrolyte (based on 100% by mass of the total amount of the components contained in the nonaqueous electrolyte) from the viewpoint of improving battery performance. Moreover, the concentration is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less from the viewpoint of suppressing a decrease in battery performance due to an increase in the viscosity of the electrolyte.

[0061] From the viewpoint of improving the battery performance, the content of the sulfonylimide compound (1) in the non-aqueous electrolyte is preferably 10 mol % or more, more preferably 15 mol % or more, based on the total 100 mol % of the electrolyte salt contained in the non-aqueous electrolyte. The upper limit of the content is preferably 50 mol % or less.

[0062] (Other electrolyte solvents) The non-aqueous electrolyte may contain other electrolyte solvents (electrolyte solvents other than the electrolyte solvent (A) and the electrolyte solvent (B)) within the scope of the present invention. The other electrolyte solvents may be mixed with the non-aqueous electrolyte, or may be mixed with the sulfonylimide solution and / or the sulfonylimide aqueous solution in the preparation process of the non-aqueous electrolyte. The other electrolyte solvents are not particularly limited as long as they can dissolve and disperse the electrolyte. As the other electrolyte solvent, a non-aqueous solvent having a large dielectric constant, high solubility of the electrolyte salt, a boiling point of 60° C. or more at normal pressure, and a wide electrochemically stable range is preferable. An organic solvent having a low water content is more preferable.Examples of such organic solvents include ether solvents such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,4-dioxane, and 1,3-dioxolane; cyclic carbonate solvents having unsaturated bonds such as vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, 2-vinylethylene carbonate, and phenylethylene carbonate; fluorine-containing cyclic carbonate solvents such as fluoroethylene carbonate, 4,5-difluoroethylene carbonate, and trifluoropropylene carbonate; aromatic carboxylate solvents such as methyl benzoate and ethyl benzoate; γ- lactone-based solvents such as butyrolactone, γ-valerolactone, δ-valerolactone; phosphate-based solvents such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, triethyl phosphate; nitrile-based solvents such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile, isobutyronitrile; sulfur compound-based solvents such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, 2,4-dimethyl sulfolane; aromatic nitrile-based solvents such as benzonitrile, tolunitrile; nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 3-methyl-2-oxazolidinone, etc.; ethyl acetate, butyric acid. Le et al. These solvents may be used alone or in combination of two or more kinds.

[0063] (Additives) The non-aqueous electrolyte may contain an additive for improving various properties of the lithium ion secondary battery. The additive may be added to the non-aqueous electrolyte, or may be added to the sulfonylimide solution and / or the sulfonylimide aqueous solution in the preparation process of the non-aqueous electrolyte. Examples of the additive include carboxylic acid anhydrides such as succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexane dicarboxylic anhydride, cyclopentane tetracarboxylic dianhydride, and phenylsuccinic anhydride; ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone, tetramethylthiuram monosulfide, and trimethylene glycol sulfate. Sulfur-containing compounds such as esters; nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone, and N-methylsuccinimide; saturated hydrocarbon compounds such as heptane, octane, and cycloheptane; carbonate compounds such as vinylene carbonate, fluoroethylene carbonate (FEC), trifluoropropylene carbonate, phenylethylene carbonate, and erythritan carbonate; sulfamic acid (amidosulfuric acid, H 3 NSO 3 );sulfamates (alkali metal salts such as lithium salts, sodium salts, potassium salts, etc.; alkaline earth metal salts such as calcium salts, strontium salts, barium salts, etc.; other metal salts such as manganese salts, copper salts, zinc salts, iron salts, cobalt salts, nickel salts, etc.; ammonium salts; guanidine salts, etc.); lithium fluorosulfonates (LiFSO 3 ), sodium fluorosulfonate (NaFSO 3 ), potassium fluorosulfonate (KFSO 3 ), magnesium fluorosulfonate (Mg(FSO 3 ) 2 ) and other fluorosulfonic acid compounds; lithium monofluorophosphate (Li 2 PO 3 F), lithium difluorophosphate (LiPO 2 F 2fluorophosphate compounds such as lithium bis(oxalato)borate (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorooxalatophosphanite (LIDFOP), lithium tetrafluorooxalatophosphate (LITFOP), lithium difluorobis(oxalato)phosphate (LiDFOP), lithium tris(oxalato)phosphate, and other fluorooxalato compounds such as lithium salts having an oxalic acid skeleton. These additives may be used alone or in combination of two or more.

[0064] (moisture content) The amount of water (water concentration, water content) in the non-aqueous electrolyte is preferably 10000 mass ppm (1 mass%) or less, more preferably 1000 mass ppm or less, even more preferably 100 mass ppm or less, and even more preferably 50 mass ppm or less, from the viewpoint of suppressing the decomposition of the sulfonylimide compound (1) by water. The lower the water content, the more preferable it is, and it may be below the detection limit, or may contain substantially no water (0 mass ppm). The water content can be measured by the method described in the examples below, for example, using a Karl Fischer water content meter.

[0065] The nonaqueous electrolyte may contain moisture at a concentration of, for example, 0.1 ppm by mass or more, 0.3 ppm by mass or more, 0.5 ppm by mass or more, 0.7 ppm by mass or more, 0.8 ppm by mass or more, 1 ppm by mass or more, 1.5 ppm by mass or more, 2 ppm by mass or more, 3 ppm by mass or more, 5 ppm by mass or more, 7 ppm by mass or more, or 10 ppm by mass or more.

[0066] (Remaining amount of electrolyte solvent (A)) The remaining amount of the electrolyte solvent (A) contained in the nonaqueous electrolyte is preferably 25 mol % or less, and more preferably 20 mol % or less, relative to 100 mol % of the nonaqueous electrolyte, from the viewpoint of reducing the electrolyte solvent (A) and obtaining a nonaqueous electrolyte containing a desired electrolyte solvent (B).

[0067] Furthermore, from the viewpoint of reducing the amount of electrolyte solvent (A) and obtaining a nonaqueous electrolyte solution containing a desired electrolyte solvent (B), the remaining amount of electrolyte solvent (A) contained in the nonaqueous electrolyte solution is preferably 30 mass % or less, more preferably 25 mass % or less, and even more preferably 20 mass % or less, relative to the entire nonaqueous electrolyte solution (relative to 100 mass % of the total amount of components contained in the nonaqueous electrolyte solution).

[0068] The nonaqueous electrolyte thus constructed is used, for example, in batteries (batteries having a charge / discharge mechanism), electricity storage (electrochemical) devices (or ion conductor materials constituting these), etc. Specifically, the electrolyte can be used as an electrolyte constituting, for example, primary batteries, secondary batteries (for example, lithium (ion) secondary batteries), fuel cells, electrolytic capacitors, electric double layer capacitors, solar cells, electrochromic display elements, etc. Hereinafter, an explanation will be given taking batteries (particularly secondary batteries) as an example.

[0069] <Effects> According to the method for producing a nonaqueous electrolyte solution according to this embodiment, the following effects can be obtained. The method for producing a non-aqueous electrolyte solution involves preparing a sulfonylimide solution containing a sulfonylimide compound (1) and an electrolyte solvent (A), adding an electrolyte solvent (B) to the solution, and distilling the resulting liquid mixture to remove the electrolyte solvent (A). This series of steps (operations) allows the electrolyte solvent (A) to be replaced with the desired electrolyte solvent (B) without going through a complicated step such as an extraction step. In the method for producing a nonaqueous electrolyte, when at least one solvent selected from the group consisting of chain carbonate solvents and chain ester solvents is used as the electrolyte solvent (A) and at least one solvent selected from the group consisting of cyclic carbonate solvents and cyclic ester solvents is used as the electrolyte solvent (B), a nonaqueous electrolyte with a low water content can be obtained. When the method for producing a non-aqueous electrolyte solution further includes a series of steps (operations) of first preparing an aqueous sulfonylimide solution containing the sulfonylimide compound (1) and then adding an electrolyte solvent (A) to the aqueous solution to dehydrate it, the water content of the resulting sulfonylimide solution becomes even lower, resulting in a non-aqueous electrolyte solution with an even lower water content. EXAMPLES

[0070] The present disclosure will be described below based on examples. Note that the present disclosure is not limited to the following examples, and the following examples can be modified or changed based on the spirit of the present disclosure, and are not excluded from the scope of the present disclosure.

[0071] Synthesis Example 1 (Synthesis of LiFSI / DMC solution) In a dry room with a dew point of -40°C or less, a stirrer tip was placed in a 500 mL three-necked separable flask equipped with a cooling tube connected to a vacuum pump, a thermometer to measure the internal temperature, and a solvent inlet, and an aqueous solution of lithium bis(fluorosulfonyl)imide (hereinafter referred to as "LiFSI", Mw: 187.06, manufactured by Nippon Shokubai Co., Ltd.) containing 50% by mass of LiFSI (LiFSI / H 2 Then, 301.01 g of sulfonylimide aqueous solution and 23.13 g of dimethyl carbonate (DMC, Mw: 90.08) were added.

[0072] Next, the flask was depressurized to 10 kPa using a vacuum pump, and then the flask was immersed in an oil bath and gradually heated (oil bath temperature: 98°C or less). At the same time as the distillation of the solvent started, DMC was continuously added from the solvent inlet so that the liquid level was always constant. When the DMC basic unit reached 52.5 (per LiFSI weight), the dripping was stopped and the pressure was released. The water content (water concentration) in the LiFSI / DMC solution (sulfonylimide solution) after the pressure release was measured by the following method and was 13.3 mass ppm. The LiFSI / DMC solution was pressure-filtered using a PTFE (polytetrafluoroethylene) membrane filter with a pore size of 3 μm to remove turbidity components.

[0073] [Moisture measurement] The water content (water concentration) in the LiFSI / DMC solution was measured using a Karl Fischer water content analyzer AQ-2000 (Hiranuma Sangyo Co., Ltd.) with Aqualite RS-A (Hiranuma Sangyo Co., Ltd.) as the generating liquid and Aqualite CN (Hiranuma Sangyo Co., Ltd.) as the counter liquid.

[0074] Synthesis Example 2 (Synthesis of LiFSI / EMC solution) A LiFSI / EMC solution (sulfonylimide solution) was prepared by carrying out the same operation as in Synthesis Example 1, except that the solvent continuously added was changed to ethyl methyl carbonate (EMC, Mw: 104.11). The water content (water concentration) in the obtained LiFSI / EMC solution was measured by the above-mentioned method and was found to be 15.4 ppm by mass.

[0075] Synthesis Example 3 (Synthesis of LiFSI / EtCOOEt solution) A LiFSI / EtCOOEt solution (sulfonylimide solution) was prepared by carrying out the same operation as in Synthesis Example 1, except that the solvent to be continuously added was changed to ethyl propionate (EtCOOEt, Mw: 102.13). The water content (water concentration) in the obtained LiFSI / EtCOOEt solution was measured by the above-mentioned method and was found to be 15.7 ppm by mass.

[0076] <Example 1> To 25 g of the LiFSI / DMC solution obtained in Synthesis Example 1, 15 g of EC (ethylene carbonate, Mw: 88.06) was added, and the mixture was stirred until homogenous. Then, using a rotary evaporator ("REN-1000", manufactured by IWAKI Corporation) heated to 60°C, the pressure was reduced to 5 kPa and the solvent was distilled off for 30 minutes. The degree of pressure reduction was then further reduced to 2.5 kPa and the solvent was distilled off for 30 minutes. By the above operations, a LiFSI / EC solution (nonaqueous electrolyte) was obtained. The solvent composition of the LiFSI / EC solution was 1 The sample was analyzed by H-NMR, and the water content was measured by the method described above.

[0077] [ 1 H-NMR] 1H-NMR measurements were performed using a Varian “Unity Plus-400” (internal standard: trifluorotoluene, number of accumulations: 64).

[0078] <Example 2> A LiFSI / PC solution (non-aqueous electrolyte) was obtained in the same manner as in Example 1, except that PC (propylene carbonate, Mw: 102.09) was used instead of EC, and the solvent composition was 1 The sample was analyzed by H-NMR, and the water content was measured by the method described above.

[0079] <Example 3> A LiFSI / EC (nonaqueous electrolyte) solution was obtained in the same manner as in Example 1, except that the LiFSI / EMC solution obtained in Synthesis Example 2 was used instead of the LiFSI / DMC solution obtained in Synthesis Example 1. The solvent composition was 1 The sample was analyzed by H-NMR, and the water content was measured by the method described above.

[0080] <Example 4> A LiFSI / PC solution (non-aqueous electrolyte) was obtained in the same manner as in Example 3, except that PC was used instead of EC. The solvent composition was 1 The sample was analyzed by H-NMR, and the water content was measured by the method described above.

[0081] <Example 5> To 25 g of the LiFSI / EtCOOEt solution obtained in Synthesis Example 3, 15 g of GBL (γ-butyrolactone, Mw: 86.09) was added, and the mixture was stirred until homogenous. Then, using a rotary evaporator ("REN-1000", manufactured by IWAKI Corporation) heated to 60° C., the pressure was reduced to 5 kPa and the solvent was distilled off for 30 minutes. The degree of pressure reduction was then further reduced to 2.5 kPa and the solvent was distilled off for 30 minutes. By the above operations, a LiFSI / GBL solution (nonaqueous electrolyte) was obtained. The solvent composition of the LiFSI / GBL solution was 1 The sample was analyzed by H-NMR, and the water content was measured by the method described above.

[0082] <Comparative Example 1> A 100 mL flask was filled with an aqueous solution of LiFSI (LiFSI / H 2 Then, 19.83 g of EC and 6.76 g of EC were added and stirred until the mixture was homogenized. Thereafter, using a rotary evaporator ("REN-1000", manufactured by IWAKI) heated to 60°C, the pressure inside the flask was reduced to 5 kPa and the solvent was distilled off for 30 minutes. When the distillation stopped, the pressure was released, and 9.29 g of EC was added and distillation was carried out again under the same conditions. When the distillation stopped, the pressure was released and a LiFSI / EC solution containing 35 mass% LiFSI was obtained. The solvent composition in this LiFSI / EC solution was 1 The sample was analyzed by H-NMR, and the water content (water concentration) was measured by the method described above.

[0083] The electrolyte amount, electrolyte solvent composition, and water content of each LiFSI solution obtained above were analyzed, and the results are shown in Table 1.

[0084] [Table 1] [Industrial Applicability]

[0085] INDUSTRIAL APPLICABILITY As described above, the present disclosure is suitable for nonaqueous electrolyte solutions used in lithium ion secondary batteries and the like.

Claims

1. A method for producing a nonaqueous electrolyte solution containing a sulfonylimide compound represented by general formula (1) and an electrolyte solvent (B), comprising the steps of: a preparation step of preparing a sulfonylimide solution containing the sulfonylimide compound represented by the general formula (1) and an electrolyte solvent (A) different from the electrolyte solvent (B); a fractional distillation step of adding the electrolyte solvent (B) to the sulfonylimide solution obtained in the preparation step and distilling off the electrolyte solvent (A); The method for producing a nonaqueous electrolyte solution, wherein the difference in boiling point between the electrolyte solvent (A) and the electrolyte solvent (B) is 130° C. or more and 300° C. or less. LiN (RSO ２ ) (FSO ２ (R represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms.) (1)

2. The method for producing a nonaqueous electrolyte according to claim 1 , wherein the electrolyte solvent (A) has a boiling point of 60° C. or higher.

3. The method for producing a nonaqueous electrolyte according to claim 1 or 2, wherein the electrolyte solvent (B) has a boiling point of 200° C. or higher.

4. A method for producing a nonaqueous electrolyte solution containing a sulfonylimide compound represented by general formula (1) and an electrolyte solvent (B), comprising the steps of: a preparation step of preparing a sulfonylimide solution containing the sulfonylimide compound represented by the general formula (1) and an electrolyte solvent (A) different from the electrolyte solvent (B); a fractional distillation step of adding the electrolyte solvent (B) to the sulfonylimide solution obtained in the preparation step and distilling off the electrolyte solvent (A); The method for producing a non-aqueous electrolyte solution, wherein the electrolyte solvent (A) and the electrolyte solvent (B) are both carbonate-based solvents or ester-based solvents, and when both are carbonate-based solvents, the electrolyte solvent (A) is a chain carbonate-based solvent and the electrolyte solvent (B) is a cyclic carbonate-based solvent, and when both are ester-based solvents, the electrolyte solvent (A) is a chain ester-based solvent and the electrolyte solvent (B) is a cyclic ester-based solvent. LiN(RSO 2 )(FSO 2 ) (R represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms) (1)

5. A method for producing a nonaqueous electrolyte solution containing a sulfonylimide compound represented by general formula (1) and an electrolyte solvent (B), comprising the steps of: a preparation step of preparing a sulfonylimide solution containing the sulfonylimide compound represented by the general formula (1) and an electrolyte solvent (A) different from the electrolyte solvent (B); a fractional distillation step of adding the electrolyte solvent (B) to the sulfonylimide solution obtained in the preparation step and distilling off the electrolyte solvent (A); The electrolyte solvent (A) is at least one selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl propionate, and propyl propionate; In the preparation step, the electrolyte solvent (A) is added to an aqueous sulfonylimide solution containing the sulfonylimide compound represented by the general formula (1) to dehydrate the solution. LiN(RSO 2 )(FSO 2 ) (R represents a fluorine atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group having 1 to 6 carbon atoms) (1)

6. The method for producing a non-aqueous electrolyte solution according to claim 1 , wherein the water content in the non-aqueous electrolyte solution is 10,000 ppm by mass or less.

7. 6. The method for producing a non-aqueous electrolyte solution according to claim 1, wherein a remaining amount of the electrolyte solvent (A) in the non-aqueous electrolyte solution is 20 mass % or less relative to 100 mass % of the non-aqueous electrolyte solution.

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