JP2018035060A - Lithium bis(fluorosulfonyl) imide composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium bis(fluorosulfonyl) imide composition that shows improvements in high-temperature discharge properties, low-temperature input/output properties, and room-temperature rate properties, in a non-aqueous electrolyte using LiFSI.SOLUTION: A lithium bis(fluorosulfonyl) imide composition contains lithium bis(fluorosulfonyl) imide of 90 mass% or more and Fions of more than 1000 mass ppm, with the content of SOions of 6000 mass ppm or less. The content of HF is 5000 mass ppm or less, preferably.SELECTED DRAWING: None

Description

  The present invention relates to a lithium bis (fluorosulfonyl) imide composition.

LiTFSI, LiPF ₆ , and LiFSI [lithium bis (fluorosulfonyl) imide] are known as lithium salts used in lithium ion batteries and lithium ion capacitors. Patent Document 1 describes an alkali metal salt of fluorosulfonylimide having a fluoride ion (F ⁻ ) content of preferably 1000 ppm or less. And it is described that when the content of fluoride ion (F ⁻ ) is large as an impurity, it is difficult to obtain desired characteristics when fluorosulfonylimide is used in various applications.

  Patent Document 2 describes a bis (fluorosulfonyl) imide salt characterized in that the content of fluorine ions is 100 ppm or less. Further, a bis (fluorosulfonyl) imide salt capable of isolating a high-purity bis (fluorosulfonyl) imide salt by suppressing contamination of impurities such as fluorine ions into the bis (fluorosulfonyl) imide salt Providing a manufacturing method is described. Patent Document 3 describes an alkali metal salt of fluorosulfonylimide containing 1 to 500 ppm of fluorine ions.

WO2011 / 149095 gazette Japanese Patent No. 5377784 WO2015 / 158879 Publication

  In the case where an electrolyte solution containing lithium bis (fluorosulfonyl) imide is used for a battery such as a secondary battery, the present inventors reduce the battery resistance, so that the positive electrode potential after charging becomes a noble state. In a combined storage test of a high temperature of ℃ or higher and a high voltage of 4.3 V or higher, it was found that the deterioration of the positive electrode progressed and the metal elution in the positive electrode progressed.

  Accordingly, an object of the present invention is to use a combined storage test of, for example, a high temperature of 80 ° C. or higher and a high voltage of 4.3 V or higher when an electrolyte containing lithium bis (fluorosulfonyl) imide is used for a battery such as a secondary battery. The lithium bis (fluorosulfonyl) imide composition, in which elution of the metal in the positive electrode due to the progress of the deterioration of the positive electrode is suppressed, and problems such as decomposition of the electrolytic solution and corrosion of the components of the electrochemical device are difficult to occur. is there.

The present inventors have made intensive studies in order to solve the above problems, including lithium bis (fluorosulfonyl) imide 90 mass% or more, F ^- including a specific amount of ion and SO ₄ ^2-ion, lithium bis The present inventors have found that the above problems can be solved by a (fluorosulfonyl) imide composition, and have completed the present invention.

That is, the lithium bis (fluorosulfonyl) imide composition of the present invention contains 90% by mass or more of lithium bis (fluorosulfonyl) imide, contains more than 1000 ppm by mass of F ⁻ ions, and further has a SO ₄ ^2- ion content. It is 6000 mass ppm or less.
In the lithium bis (fluorosulfonyl) imide composition of the present invention, the content of HF (hydrogen fluoride) is preferably 5000 ppm by mass or less.
Further, the lithium bis (fluorosulfonyl) imide composition of the present invention preferably contains 100 mass ppm to 5 mass% of LiFSO ₃ .
Furthermore, in the lithium bis (fluorosulfonyl) imide composition of the present invention, the pH of a solution obtained by dissolving 1 g of any of the above lithium bis (fluorosulfonyl) imide compositions in 30 mL of dehydrated methanol is 3 or more and 8 or less. Preferably there is.

Of the present invention, it includes lithium bis (fluorosulfonyl) imide 90 mass% or more, F ^- including ions and SO ₄ ^2-ion specific amount, according to the lithium bis (fluorosulfonyl) imide composition, such as a secondary battery In the battery, the F ^- ion component contained reacts with the positive electrode active material to form a fluorine-containing protective film on the surface of the positive electrode active material, so that elution of the metal after leaving at high temperature and high voltage can be suppressed, and the decomposition of the electrolyte and electrical Problems such as corrosion of the components of the chemical device hardly occur, and the capacity retention rate can be improved.

1. Lithium bis (fluorosulfonyl) imide composition The lithium bis (fluorosulfonyl) imide composition according to the present invention contains 90% by mass or more of lithium bis (fluorosulfonyl) imide (hereinafter sometimes referred to as LiFSI), and is an F ⁻ ion. More than 1000 ppm by mass, and the SO ₄ ^2- ion content is 6000 ppm by mass or less.

The content of F ⁻ ions in the lithium bis (fluorosulfonyl) imide composition of the present invention is preferably more than 1000 mass ppm and less than or equal to 50000 mass ppm, more preferably more than 2000 mass ppm and less than or equal to 30000 mass ppm, more preferably 3000 mass ppm. Ultra 20000 mass ppm or less. The lithium bis (fluorosulfonyl) imide composition according to the present invention, F ^- by a containing more than 1000 ppm by mass ions, F comprises ^- a fluorine-containing protective coating reaction was positive electrode active material surface ion component positive electrode active material When used in a battery such as a secondary battery, the metal elution after being left at high temperature and high voltage can be suppressed and the capacity retention rate can be improved. The content of F ⁻ ions can be measured by anion ion chromatography.

In the lithium bis (fluorosulfonyl) imide composition of the present invention, the content of SO ₄ ^2- ion is 6000 mass ppm or less, preferably 3000 mass ppm or less, more preferably 1000 mass ppm or less, and further preferably 500 mass. ppm or less, most preferably 300 ppm by mass or less. The lower limit of the content of SO ₄ ^2-ions is not particularly limited can be 1 mass ppm. In the lithium bis (fluorosulfonyl) imide composition according to the present invention, by using SO ₄ ^2- ion at 6000 mass ppm or less, decomposition of the electrolytic solution or electrochemical device is possible even when used as an electrolytic solution for electrochemical devices. It is difficult to cause problems such as corrosion of the components. The content of SO ₄ ^2- ion can be measured by anion ion chromatography.

  In the lithium bis (fluorosulfonyl) imide composition of the present invention, the HF content is preferably 5000 ppm by mass or less, and more preferably from 50 ppm by mass to 5000 ppm by mass. If the HF concentration is too high, HF corrodes the positive electrode active material or the positive electrode aluminum current collector, and metal elution may be further promoted. Therefore, the amount of HF is preferably 5000 ppm by mass or less. The content of HF can be measured by dissolving the lithium bis (fluorosulfonyl) imide composition in dehydrated methanol, neutralizing with a NaOH methanol solution, and measuring the resulting acid content as HF.

Moreover, the lithium bis (fluorosulfonyl) imide composition of the present invention may further contain 100 mass ppm to 5 mass% of LiFSO ₃ . When the content of LiFSO ₃ is in such a range, when used in a battery such as a secondary battery, the low temperature input / output characteristics, rate characteristics, and (45 ° C.) cycle characteristics of the battery may be further improved. is there. The content of LiFSO ₃ can be measured by F-NMR.

  In the lithium bis (fluorosulfonyl) imide composition of the present invention, the pH of a solution obtained by dissolving 1 g of the lithium bis (fluorosulfonyl) imide composition in 30 mL of dehydrated methanol is preferably 3 or more and 8 or less.

  The lithium bis (fluorosulfonyl) imide content in the lithium bis (fluorosulfonyl) imide composition according to the present invention is preferably 95% by mass or more, more preferably 97% by mass or more, and still more preferably. It is 98 mass% or more, and it is especially preferable that it is 99 mass% or more. The content of the solvent is preferably 70 ppm by mass or less, more preferably 50 ppm by mass or less, further preferably 30 ppm by mass or less, and particularly preferably 10 ppm by mass or less. Is preferably 5 ppm by mass or less, more preferably 1 ppm by mass or less, and most preferably no solvent.

  As said solvent, an organic solvent is mentioned, for example. The boiling point of the solvent is, for example, 0 to 250 ° C. Specifically, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, 4-methyl-1,3-dioxolane, cyclopentylmethyl ether, methyl-t-butyl ether, diethylene glycol dimethyl ether Aliphatic ether solvents such as diethylene glycol diethyl ether and triethylene glycol dimethyl ether; ester solvents such as methyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate and methyl propionate; N, N-dimethylformamide, N- Amide solvents such as methyl oxazolidinone; Nitro solvents such as nitromethane and nitrobenzene; Sulfur solvents such as sulfolane, 3-methylsulfolane and dimethyl sulfoxide; Acetonitrile Niprotic solvents such as propionitrile, isobutyronitrile, butyronitrile, valeronitrile, benzonitrile; aprotic solvents such as aromatic hydrocarbon solvents, linear, branched or cycloaliphatic Examples include poor solvents for lithium salts of fluorosulfonylimide, such as hydrocarbon solvents and aromatic ether solvents.

Examples of the poor solvent include toluene (boiling point 110.6 ° C), o-xylene (boiling point 144 ° C), m-xylene (boiling point 139 ° C), p-xylene (boiling point 138 ° C), ethylbenzene (boiling point 136 ° C), isopropyl. Benzene (boiling point 153 ° C), 1,2,3-trimethylbenzene (boiling point 169 ° C), 1,2,4-trimethylbenzene (boiling point 168 ° C), 1,3,5-trimethylbenzene (boiling point 165 ° C), tetralin (Boiling point 208 ° C.), cymene (boiling point 177 ° C.), methylethylbenzene (boiling point 153 ° C.), 2-ethyltoluene (boiling point 164 ° C.) and other aromatic hydrocarbon solvents; octane (boiling point 127 ° C.), decane (boiling point 174 ° C), dodecane (boiling point 217 ° C), undecane (boiling point 196 ° C), tridecane (boiling point 234 ° C), decalin (boiling point 191 ° C), 2, , 4,6,6-pentamethylheptane (boiling point 170 ° C.-195 ° C.), isoparaffin (for example, “Marcazole R” (2,2,4,6,6-pentamethylheptane manufactured by Maruzen Petrochemical Co., Ltd., 2 , 2,4,4,6-pentamethylheptane, boiling point 178 ° C.-181 ° C.), “Isopar® G” (C9-C11 mixed isoparaffin manufactured by ExxonMobil, boiling point 167 ° C.-176 ° C.), Linear or branched aliphatic hydrocarbon solvents such as “Isopar (registered trademark) E” (C8-C10 mixed isoparaffin, boiling point 115 ° C.-140 ° C. manufactured by ExxonMobil); cyclohexane (boiling point 81 ° C.) , Methylcyclohexane (boiling point 101 ° C.), 1,2-dimethylcyclohexane (boiling point 123 ° C.), 1,3-dimethylcyclohexane (boiling point 12) ° C), 1,4-dimethylcyclohexane (boiling point 119 ° C), ethylcyclohexane (boiling point 130 ° C), 1,2,4-trimethylcyclohexane (boiling point 145 ° C), 1,3,5-trimethylcyclohexane (boiling point 140 ° C) , Propylcyclohexane (boiling point 155 ° C.), butylcyclohexane (boiling point 178 ° C.), alkylcyclohexane having 8 to 12 carbon atoms (for example, “Swaclean 150” (mixture of C9 alkylcyclohexane manufactured by Maruzen Petrochemical Co., Ltd., boiling point 152− Cyclic aliphatic hydrocarbon solvents such as 170 ° C; anisole (boiling point 154 ° C), 2-methylanisole (boiling point 170 ° C), 3-methylanisole (boiling point 175 ° C), 4-methylanisole (boiling point 174 ° C), etc. An aromatic ether solvent;
However, the solvent prescribed | regulated by this invention is not specifically limited to what is shown to the said specific example.

Moreover, lithium bis (fluorosulfonyl) imide composition according to the present _invention preferably contains a FSO 2 _{NH 2} 10 wt ppm~1 wt%. The content of FSO ₂ NH ₂ is preferably 10 mass ppm or more, more preferably 100 mass ppm or more, still more preferably 500 mass ppm or more, and particularly preferably 1000 ppm or more. Moreover, 1 mass% or less is preferable, More preferably, it is 0.7 mass% or less, More preferably, it is 0.5 mass% or less, Most preferably, it is 0.3 mass% or less. When the content of FSO ₂ NH ₂ is in such a range, when used for a secondary battery or the like, the low-temperature input / output characteristics, rate characteristics, and (45 ° C.) cycle characteristics of the secondary battery and the like are improved. The content of FSO ₂ NH ₂ can be measured by F-NMR.
As another form of the lithium bis (fluorosulfonyl) imide composition, the amount of the solvent is not particularly limited, and a form containing 10 mass ppm to 1 mass% of FSO ₂ NH ₂ is also a preferred form.

2. Electrolytic Solution The electrolytic solution contains the above lithium bis (fluorosulfonyl) imide composition containing 90% by mass or more of lithium bis (fluorosulfonyl) imide and containing more than 1000 ppm by mass of F ⁻ ions. The content of the lithium bis (fluorosulfonyl) imide composition in the electrolytic solution is preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more, still more preferably more than 0.5 mol / L, most preferably. Is 0.6 mol / L or more, preferably 6 mol / L or less, more preferably 4 mol / L or less, still more preferably 2 mol / L or less, and most preferably 1.5 mol / L or less.

The electrolyte solution may contain other known components such as other lithium salts such as LiPF ₆ , radical scavengers such as antioxidants and flame retardants, and redox stabilizers.

  The electrolytic solution may contain a solvent. The solvent that can be used in the electrolytic solution is not particularly limited as long as it can dissolve and disperse electrolyte salts (sulfonylimide compounds and the above-described lithium salts). For example, solvents other than cyclic carbonate and cyclic carbonate Any conventionally known solvent used for batteries, such as a non-aqueous solvent, a medium such as a polymer and a polymer gel used in place of the solvent, and the like can be used.

In the above electrolytic solution, by using a lithium bis (fluorosulfonyl) imide composition containing more than 1000 ppm by mass of F ⁻ ions, the contained F ⁻ ion component reacts with the positive electrode active material to protect the surface of the positive electrode active material with fluorine. When used in a battery such as a secondary battery by forming a film, etc., metal elution after being left at high temperature and high voltage can be suppressed, and the capacity retention rate can be improved.

3. Method for Producing Electrolyte A method for producing an electrolyte includes a lithium bis (fluorosulfonyl) imide composition in which a bis (fluorosulfonyl) imide and a lithiating agent are reacted to produce the lithium bis (fluorosulfonyl) imide composition. And an electrolytic solution manufacturing step of manufacturing an electrolytic solution using the lithium bis (fluorosulfonyl) imide composition obtained in the lithium bis (fluorosulfonyl) imide composition manufacturing step.

3-1 Lithium bis (fluorosulfonyl) imide composition production process In the lithium bis (fluorosulfonyl) imide composition production process, bis (fluorosulfonyl) imide is reacted with a lithiating agent to produce lithium bis (fluorosulfonyl) imide. A composition is produced.

  In the present invention, the method for synthesizing bis (fluorosulfonyl) imide is not particularly limited, and examples thereof include a method for synthesizing bis (fluorosulfonyl) imide from bis (halogenated sulfonyl) imide using a fluorinating agent. . Examples of the halogen in the bis (halogenated sulfonyl) imide include Cl, Br, I, and At other than F.

  Hereinafter, a fluorination step of synthesizing bis (fluorosulfonyl) imide from bis (halogenated sulfonyl) imide using a fluorinating agent will be described.

  In the fluorination step, a fluorination reaction of bis (halogenated sulfonyl) imide is performed. For example, there are a method described in CA2527802, a method described in Jean'ne M. Shreeve et al., Inorg. Chem. 1998, 37 (24), 6295-6303, and the like. A commercially available bis (halogenated sulfonyl) imide as a starting material may be used, or a bis (halogenated sulfonyl) imide synthesized by a known method may be used. There is also a method of synthesizing bis (fluorosulfonyl) imide using urea and fluorosulfonic acid described in JP-A-8-511274.

  As a method for synthesizing bis (fluorosulfonyl) imide from bis (halogenated sulfonyl) imide using a fluorinating agent, a method using HF as the fluorinating agent can be preferably used. As an example, the fluorination reaction of bis (chlorosulfonyl) imide is represented by the following formula (1). For example, bis (fluorosulfonyl) imide (HFSI) can be obtained by introducing HF into bis (chlorosulfonyl) imide.

  The molar ratio of HF to bis (halogenated sulfonyl) imide at the start of the fluorination step is preferably 2 or more. The lower limit may be 3 or more and 5 or more, and the upper limit may be 100 or less, 50 or less, 20 or less, 10 or less. By setting the molar ratio in this manner, fluorination of bis (halogenated sulfonyl) imide can be performed more reliably. If the amount used is small, the reaction rate may decrease or the reaction may not proceed sufficiently, which is not desirable. If the amount used is large, the recovery of raw materials may become complicated and productivity may decrease. Not desirable.

As for the temperature of the said fluorination process, 20 degreeC or more, 40 degreeC or more, 60 degreeC or more, 80 degreeC or more can be mentioned as a minimum, and 200 degrees C or less, 160 degrees C or less, 140 degrees C or less, 120 degrees C or less can be mentioned as an upper limit. What is necessary is just to select suitably in view of reaction rate.
The fluorination step may be performed under high pressure or normal pressure.

  Subsequently, a mixture containing the bis (fluorosulfonyl) imide obtained by the above method and a lithiating agent is reacted to produce a lithium bis (fluorosulfonyl) imide composition.

  The mixture after reacting the mixture containing bis (fluorosulfonyl) imide and the lithiating agent comprises unreacted bis (fluorosulfonyl) imide, unreacted lithiating agent, lithium bis (fluorosulfonyl) imide, Contains by-products. The total weight ratio of bis (fluorosulfonyl) imide, lithiating agent and lithium bis (fluorosulfonyl) imide with respect to the entire mixture after the reaction is preferably 0.8 or more, more preferably 0.85 or more. 0.9 or more is more preferable, and 0.95 or more is particularly preferable.

  The total weight ratio of the mixture containing bis (fluorosulfonyl) imide and lithiating agent to the whole mixture of bis (fluorosulfonyl) imide and lithiating agent at the start of the reaction is preferably 0.8 or more, It is more preferably 0.85 or more, further preferably 0.9 or more, and particularly preferably 0.95 or more.

Examples of lithiating agents include alkyllithiums such as LiOH, Li ₂ CO ₃ , LiHCO ₃ , LiCl, LiF, CH ₃ OLi, EtLi, BuLi, and t-BuLi (where Et represents an ethyl group and Bu represents a butyl group). Compounds and the like. Among these, LiF is preferable.

  The following formula (2) shows the production of lithium bis (fluorosulfonyl) imide by reacting a mixture containing bis (fluorosulfonyl) imide and LiF.

The mixture after reacting the mixture containing bis (fluorosulfonyl) imide and LiF may contain unreacted bis (fluorosulfonyl) imide and unreacted LiF, and lithium bis (fluorosulfonyl). ) imide, F ^- comprises an ion, and _SO ^{4 2-ions,} the by-product HF, it may further contain LiFSO _3.

  The total weight ratio of bis (fluorosulfonyl) imide, LiF and lithium bis (fluorosulfonyl) imide with respect to the entire mixture after the reaction is preferably 0.8 or more, more preferably 0.85 or more, and 0 Is more preferably 0.9 or more, and particularly preferably 0.95 or more. Moreover, it is preferable to include the process of reducing content of HF produced | generated during reaction.

  The total weight ratio of the mixture containing bis (fluorosulfonyl) imide and LiF to the whole mixture of bis (fluorosulfonyl) imide and LiF at the start of the reaction is preferably 0.8 or more, and 0.85 or more. Is more preferably 0.9 or more, and particularly preferably 0.95 or more.

  In the lithium bis (fluorosulfonyl) imide composition production process, the total weight ratio of bis (fluorosulfonyl) imide, lithiating agent, and bis (fluorosulfonyl) imide lithium salt to the total mixture after the reaction is 0.8. You may use in the range used as the above. In the lithium chloride step, HF may not be used.

  The reaction temperature of the mixture containing bis (fluorosulfonyl) imide and the lithiating agent is preferably 50 ° C. or higher, more preferably 80 ° C. or higher, further preferably 100 ° C. or higher, 120 ° C. The above is particularly preferable. Examples of the upper limit temperature include 180 ° C. or lower and 160 ° C. or lower, and 140 ° C. and 150 ° C. can be used. If the reaction temperature is too low, the reaction may not proceed sufficiently. If the reaction temperature is too high, the product may be decomposed, which is undesirable. Moreover, the pressure range of the said reaction becomes like this. Preferably it is 1250 hPa or less, More preferably, it is 1150 hPa or less, More preferably, it is 1050 hPa or less.

  The molar ratio of lithium contained in the lithiating agent relative to bis (fluorosulfonyl) imide is preferably 0.8 or more and 1.2 or less, more preferably 0.9 or more and 1.1 or less, and 1.0 The vicinity is most preferable.

3-2 Drying and powdering step The mixture after the above reaction may be used as it is as a lithium bis (fluorosulfonyl) imide composition, but is dried and powdered to obtain lithium bis (fluorosulfonyl) imide. A composition is preferred.
The method for drying and pulverizing the lithium bis (fluorosulfonyl) imide composition is not particularly limited. When HF is contained, (1) HF is distilled off at a temperature equal to or higher than the melting point of lithium bis (fluorosulfonyl) imide. (2) a method of powdering at a temperature below the melting point of lithium bis (fluorosulfonyl) imide and further distilling off HF, (3) (1) and ( A method combining 2) can be used.
The mixture after the above reaction is dried and pulverized to obtain a lithium bis (fluorosulfonyl) imide composition, thereby more reliably containing 90% by mass or more of lithium bis (fluorosulfonyl) imide, F ⁻ A lithium bis (fluorosulfonyl) imide composition containing more than 1000 ppm by mass of ions can be obtained, and a more excellent electrolytic solution can be produced.

  The drying method of a lithium bis (fluorosulfonyl) imide composition is not specifically limited, A conventionally well-known drying apparatus can be used. When drying above the melting point of lithium bis (fluorosulfonyl) imide, the drying temperature is preferably 140 ° C. or higher. When drying below the melting point, the drying temperature is preferably 0 ° C to 140 ° C. More preferably, it is 10 degreeC or more, More preferably, it is 20 degreeC or more. Drying of the lithium bis (fluorosulfonyl) imide composition may be performed under reduced pressure or may be performed while supplying a gas to a drying apparatus. Examples of usable gas include inert gas such as nitrogen and argon and dry air. In particular, when HF is contained, since the boiling point of HF is as low as less than 20 ° C., it can be effectively dried in the above temperature range.

Note that bis (chlorosulfonyl) imide, a lithiating agent such as HF and LiF, which is a raw material preferably used in the above steps, is dissolved in a solvent as necessary, and then subjected to distillation, crystallization, reprecipitation, etc. It can be purified by a known method.
Preferably, bis (chlorosulfonyl) imide used as a raw material, lithiating agent such as HF and LiF, bis (fluorosulfonyl) imide as a product, lithium bis (fluorosulfonyl) imide, and produced as a by-product. The obtained hydrogen chloride, HF, and the like can be recovered by a known method such as distillation, crystallization, reprecipitation, etc. after dissolving in a solvent as necessary.

3-3 Electrolytic Solution Manufacturing Step In the electrolytic solution manufacturing step, an electrolytic solution is manufactured using the lithium bis (fluorosulfonyl) imide composition obtained in the lithium bis (fluorosulfonyl) imide composition manufacturing step. The electrolytic solution is prepared by mixing the lithium bis (fluorosulfonyl) imide composition obtained in the lithium bis (fluorosulfonyl) imide composition production process with the other known components, additives, and solvent. it can. The content of the lithium bis (fluorosulfonyl) imide composition in the electrolytic solution is preferably 0.05 mol / L or more, more preferably 0.1 mol / L or more, still more preferably more than 0.5 mol / L, most preferably. Is 0.6 mol / L or more, preferably 6 mol / L or less, more preferably 4 mol / L or less, still more preferably 2 mol / L or less, and most preferably 1.5 mol / L or less.

  In the method for producing the electrolytic solution, the lithium bis (fluorosulfonyl) imide composition obtained in the lithium bis (fluorosulfonyl) imide composition production step can be used as it is without being subjected to a purification step. For this reason, the manufacturing cost of the electrolyte solution containing lithium bis (fluorosulfonyl) imide can be suppressed.

4). Battery The battery includes the above-described electrolytic solution, a negative electrode, and a positive electrode. Specific examples include a primary battery, a lithium ion secondary battery, a battery having a charging and discharging mechanism, and the like. Below, a lithium ion secondary battery is demonstrated on behalf of these.

  The lithium ion secondary battery includes a positive electrode containing a positive electrode active material capable of occluding and releasing lithium ions, a negative electrode containing a negative electrode active material capable of occluding and releasing lithium ions, and a non-aqueous electrolyte. More specifically, a separator is provided between the positive electrode and the negative electrode, and the non-aqueous electrolyte is contained in the outer case together with the positive electrode, the negative electrode, and the like in a state of being impregnated in the separator.

4-1 Positive Electrode The positive electrode is formed by supporting a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like on a positive electrode current collector, and is usually formed into a sheet shape.

  The method for producing the positive electrode is not particularly limited. For example, (i) a positive electrode active material composition in which a positive electrode mixture is dissolved or dispersed in a dispersion solvent is applied to a positive electrode current collector by a doctor blade method or the like. A method of immersing the current collector in the positive electrode active material composition and then drying; (ii) bonding a sheet obtained by kneading and drying the positive electrode active material composition to the positive electrode current collector through a conductive adhesive (Iii) A positive electrode active material composition added with a liquid lubricant is applied or cast onto a positive electrode current collector to form a desired shape, and then the liquid lubricant is removed. Then, the method of extending | stretching to a uniaxial or multiaxial direction; etc. are mentioned. Moreover, you may pressurize the positive mix layer after drying as needed. Thereby, the adhesive strength with the positive electrode current collector is increased, and the electrode density is also increased.

  The material used for the positive electrode current collector, the positive electrode active material, the conductive auxiliary agent, the binder, and the solvent used in the positive electrode active material composition (solvent for dispersing or dissolving the positive electrode mixture) is not particularly limited. A material can be used, for example, each material described in JP, 2014-13704, A can be used.

  The amount of the positive electrode active material used is preferably 75 parts by mass or more and 99 parts by mass or less with respect to 100 parts by mass of the positive electrode mixture, more preferably 85 parts by mass or more, and further preferably 90 parts by mass or more. Yes, more preferably 98 parts by mass or less, still more preferably 97 parts by mass or less.

  In the case of using a conductive additive, the content of the conductive additive in the positive electrode mixture is preferably 0.1% by mass to 10% by mass with respect to 100% by mass of the positive electrode mixture (more preferably Preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 10% by mass). If the amount of the conductive assistant is too small, the conductivity is extremely deteriorated and the load characteristics and the discharge capacity may be deteriorated. On the other hand, when the amount is too large, the bulk density of the positive electrode mixture layer is increased, and the content of the binder needs to be further increased.

In the case of using the binder, the content of the binder in the positive electrode mixture is preferably 0.1% by mass to 10% by mass with respect to 100% by mass of the positive electrode mixture (more preferably 0.5% by mass). % To 9% by mass, more preferably 1% to 8% by mass). If the amount of the binder is too small, good adhesion cannot be obtained, and the positive electrode active material and the conductive additive may be detached from the current collector. On the other hand, if the amount is too large, the internal resistance may be increased, and the battery characteristics may be adversely affected.
The blending amounts of the conductive auxiliary agent and the binder can be appropriately adjusted in consideration of the intended use of the battery (emphasis on output, importance on energy, etc.), ion conductivity, and the like.

4-2 Negative electrode A negative electrode is formed by supporting a negative electrode active material, a binder, and, if necessary, a negative electrode mixture containing a conductive auxiliary agent on a negative electrode current collector, and is usually formed into a sheet shape. Yes.
As a manufacturing method of the negative electrode, a method similar to the manufacturing method of the positive electrode can be employed. In addition, the same conductive auxiliary agent, binder, and material dispersing solvent as used in the positive electrode are used in the production of the negative electrode.

  As the material of the negative electrode current collector and the negative electrode active material, conventionally known negative electrode active materials can be used. For example, each material described in JP-A-2014-13704 can be used.

4-3 Separator The separator is disposed so as to separate the positive electrode and the negative electrode. There is no restriction | limiting in particular in a separator, In this invention, all the conventionally well-known separators can be used, For example, each material as described in Unexamined-Japanese-Patent No. 2014-13704 can be used.

4-4 Battery exterior material Battery elements equipped with a positive electrode, negative electrode, separator, non-aqueous electrolyte, etc. are provided with battery exterior materials to protect the battery elements from external impacts and environmental degradation when using lithium ion secondary batteries. Is housed in. In the present invention, the material of the battery exterior material is not particularly limited, and any conventionally known exterior material can be used.

  The shape of the lithium ion secondary battery is not particularly limited, and any conventionally known shape can be used as the shape of the lithium ion secondary battery, such as a cylindrical shape, a square shape, a laminate shape, a coin shape, and a large size. Further, when used as a high voltage power source (several tens of volts to several hundreds of volts) for mounting on an electric vehicle, a hybrid electric vehicle, etc., a battery module configured by connecting individual batteries in series can be used. .

  The rated charging voltage of the lithium ion secondary battery is not particularly limited, but is preferably 3.6 V or higher. More preferably, it is 4.1 V or more, and most preferably more than 4.2 V. The effect of the present invention is particularly remarkable when used at a voltage exceeding 4.2V. More preferably, it is 4.3 V or more, and further preferably 4.35 V or more. The higher the rated charging voltage, the higher the energy density, but if it is too high, it may be difficult to ensure safety. Therefore, the rated charging voltage is preferably 4.6 V or less. More preferably, it is 4.5 V or less.

  Hereinafter, although an Example demonstrates in more detail, this invention is not limited at all by these.

[NMR measurement]
₁ H-NMR and ₁₉ F-NMR were measured using “Unity Plus-400” manufactured by Varian (internal standard substance: benzenesulfonyl fluoride, solvent: deuterated acetonitrile, integration number: 16 times). .

[ICP emission spectroscopy]
Using a multi-type ICP emission spectrophotometer ("ICPE-9000" manufactured by Shimadzu Corp.) using an aqueous solution with a concentration of 1% by mass obtained by mixing 0.1 g of LiFSI obtained in the following example with 9.9 g of ultrapure water. did.

[Ion chromatography analysis]
0.01 g LiFSI obtained in the above experimental example was diluted 1000 times with ultrapure water (over 18.2 Ω · cm) to obtain a measurement solution, and an ion chromatography system ICS-3000 (manufactured by Nippon Dionex Co., Ltd.) was used. Then, F ⁻ ions and SO ₄ ²⁻ ions contained in LiFSI were measured.
Separation mode: Ion exchange Eluent: 7-20 mM KOH aqueous solution Detector: Electrical conductivity detector Column: Anion analysis column Ion PAC AS-17C (manufactured by Nippon Dionex Co., Ltd.)

[Headspace gas chromatography analysis]
To 0.05 g of LiFSI composition obtained in the following Examples, 200 μL of dimethyl sulfoxide aqueous solution (dimethyl sulfoxide / ultra pure water = 20/80, volume ratio) and 2 mL of 20 mass% sodium chloride aqueous solution were added to obtain a measurement solution. The vial was sealed in a vial, and the amount of residual solvent contained in the lithium salt of fluorosulfonylimide was measured by a headspace-gas chromatography system (“Agilent 6890”, manufactured by Agilent).
Device: Agilent 6890
Column: HP-5 (length: 30 m, column inner diameter: 0.32 mm, film thickness: 0.25 μm) (manufactured by Agilent)
Column temperature conditions: 60 ° C. (2 minutes hold), 30 ° C./min. To 300 ° C., 300 ° C. (2 minutes hold)
Headspace condition: 80 ° C (30 minutes hold)
Injector temperature: 250 ° C
Detector: FID (300 ° C)

  LiFSI was prepared by the following manufacturing method.

Example 1
LiF 1.17 g (45 mmol) was weighed into a PFA (made of fluororesin) reaction vessel. The reaction vessel was ice-cooled, and 9.59 g (53 mmol) of HFSI was added. The reaction solution was heated to 120 ° C. and reacted for 1.5 hours. The reaction solution was evacuated under reduced pressure at 10 hPa and 140 ° C. for 2 hours to obtain a composition containing LiFSI. As a result, 7.30 g of LiFSI was obtained. The LiFSI production amount was determined by F-NMR measurement.

Example 2
In a PFA reaction vessel, 3.2 g (125 mmol) of LiF was weighed. The reaction vessel was ice-cooled, and 25.0 g (139 mmol) of HFSI was added. The reaction solution was heated to 140 ° C. and reacted for 1 hour. The reaction solution was evacuated under reduced pressure at 1.4 KPa and 140 ° C. for 2 hours to obtain a composition containing LiFSI. As a result, 22.70 g of LiFSI was obtained.

Example 3
LiF (1.43 g, 55 mmol) was weighed into a PFA reaction vessel. The reaction vessel was ice-cooled, and 7.45 g (41 mmol) of HFSI was added. The reaction solution was heated to 120 ° C. and reacted for 1.5 hours. The reaction solution was evacuated under reduced pressure at 10 hPa and 140 ° C. for 2 hours. As a result, 7.40 g of LiFSI [bis (fluorosulfonyl) imide lithium salt] was obtained. The LiFSI production amount was determined by F-NMR measurement.

Comparative Example 1
According to the method disclosed in JP 2014-201453 A, a composition containing LiFSI was obtained.

Each composition containing LiFSI obtained in Examples 1 to 3 and Comparative Example 1 was analyzed by F-NMR, and LiFSO ₃ was quantified. The contents of F ⁻ ions and SO ₄ ²⁻ ions in LiFSI were analyzed by ion chromatography. Also, 1 g of each composition containing LiFSI obtained in Examples 1 and 2 and Comparative Example 1 was dissolved in 30 mL of ultra-dehydrated methanol (manufactured by Wako Pure Chemical Industries, Ltd., water content of 10 ppm or less). HF was quantified by neutralization titration with 01N NaOH methanol solution (titration temperature 25 ° C.). The pH was measured with a pH electrode at the initial value during neutralization titration.
The results are shown in Table 1. In addition, F-NMR has a detection limit of 100 mass ppm and an ion chromatography determination limit of 1 mass ppm.

Using each composition containing LiFSI obtained in Examples 1 to 3 and Comparative Example 1, an electrolyte solution having a composition of 0.6M LiFSI + 0.6M LiPF ₆ EC / MEC = 3/7 was prepared. In weighing FSI, the content of LiFSO ₃ was considered and adjusted to 1.2 M / L. A commercially available product of LiPF ₆ was used. EC is ethylene carbonate and MEC is methyl ethyl carbonate.
Battery evaluation was carried out using each of these electrolytic solutions. As a cell used for battery evaluation, a LiCoO ₂ positive electrode, graphite as a negative electrode, a PE (polyethylene) separator, and a laminate battery with a charging voltage of 4.35 V and a design of 34 mAh were used.

<Initial rate characteristics (25 ° C) measurement>
The cell with the above specifications was charged and discharged under the following conditions, and the initial rate characteristics were measured.
Charging: Constant current Constant voltage charging: 4.35V 1C (34 mA) 1/50 C (0.68 mA) termination → Discharging: Constant current discharging: 0.2 C (6.8 mA), 1 C (34 mA), 2 C (68 mA) respectively The initial rate characteristics (25 ° C.) at a rate of 2.75 V were evaluated using the ratio (%) of the 0.2C discharge capacity and each of the 1C and 2C discharge capacities. The results are shown in Table 2. Examples 1 to 3 are improved over Comparative Example 1.

<Evaluation of initial low temperature input / output characteristics>
The initial low temperature input / output characteristics of the cells using the electrolytic solutions using the compositions containing LiFSI obtained in Examples 1 to 3 and Comparative Example 1 were evaluated as follows.
・ (Charge capacity when 0.2C constant current 2.75V end discharge state, 0 ° C 1C constant current charge 4.35V end) / (0.2C constant current 2.75V end discharge state, 25 ° C 4.35V 1C constant current constant voltage charge 1 / 50C charge capacity at end of charge) ratio (%) was defined as low temperature input characteristics.
・ (25 ° C 4.35V 1C constant current constant voltage charge 1 / 50C end charge state to 0 ° C 1C constant current discharge 2.75V end discharge capacity) / (25 ° C 4.35V 1C constant current constant voltage charge 1 / 50C end The low temperature discharge characteristic was defined as the ratio (%) of 25 ° C 1C constant current discharge 2.75V end discharge capacity) from the charged state.
The initial low-temperature input / output characteristics were evaluated using the ratio (%) between the low-temperature input characteristics and the low-temperature discharge characteristics. The results are shown in Table 3.

<4.35V charge 60 ° C 1 week standing test>
25 ° C. 4.35 V 1 C constant current constant voltage charge 1/50 C end-charged battery was stored at 60 ° C. for 1 week, and the cell circuit voltage before and after storage was measured. Further, the cell after storage was measured by the same method as the initial rate characteristic measurement, and the capacity retention rate was measured from the discharge capacity at each rate before and after storage.
Table 4 shows the cell circuit voltage (V), and Table 5 shows the capacity retention rate (%).

<After standing for 4.35V at 60 ° C for 1 week, standing for 4.4V at 85 ° C for 48 hours>
The cell which was left at 60 ° C. for 1 week in the state of 4.35 V charge was left to stand at 85 ° C. for 48 hours in the state of 4.4 V charge.
About the cell using the electrolyte solution using each composition containing LiFSI obtained in Examples 1 to 3 and Comparative Example 1, the deterioration rate after storage was measured using the discharge capacity ratio at each rate before and after being left. . The results are shown in Table 6.

As shown in Table 5, 6, F ^- in comparison with Comparative Example 1 containing little ion, F ^- ions comprise ultra 1000 mass ppm, further the content of _SO ^{4 2-ionic} or less 6000 mass ppm Example 1 to 3 improved the capacity retention rate and the deterioration rate after storage.

<ICP analysis>
4. After charging at 35 ° C for 1 week after charging at 35 ° F, open the capacity-measured cell after leaving at 4.4 ° C at 85 ° C for 48 hours in a discharged state, and collect the electrolyte under conditions of centrifuge at 2000 rpm for 5 minutes. Then, it was diluted 100 times with a 0.4% nitric acid aqueous solution, the diluted solution was analyzed by ICP, and the amount of cobalt in the electrolytic solution was analyzed.
The disassembled negative electrode and separator were separated, washed with an EMC (ethyl methyl carbonate) solution, and then vacuum dried at 45 ° C. for 24 hours.
Thereafter, the active material was peeled off from the negative electrode, immersed in 1 mL of 69% nitric acid aqueous solution for 8 hours, 15 g of water was added, the aqueous solution was filtered, and the amount of cobalt in the solution was analyzed by ICP.
Similarly, the separator was immersed in a 69% nitric acid aqueous solution for 8 hours, then 15 g of water was added and filtered, and the aqueous solution after filtration was analyzed for the amount of cobalt by ICP.
Table 7 shows the analytical values of Examples 1 to 3 when the amount of cobalt using the electrolytic solution of Comparative Example 1 is 100%. The ICP quantitative limit is 0.05 ppm.

From Table 7, in Examples 1 to 3, the amount of cobalt is reduced on the negative electrode, in the separator, and in the electrolyte solution, and is correlated with the content of F ⁻ ions, which is similar to the capacity retention rate after standing. I knew it was a relationship.

Example 4
In a 100 mL flask made of PFA, 20.0 g (110.6 mmol) of HFSI and 2.57 g (99.5 mmol) of LiF were weighed. The reaction solution was heated to 140 ° C. under normal pressure (1013 hPa) and reacted for 15 minutes, then the pressure was reduced to 2 kPa and devolatilization was performed at 143 ° C. for 1 hour. Thereafter, the mixture was cooled to obtain 19.4 g of a composition mainly composed of LiFSI. The analysis values are shown in Table 8.
The amount of the solvent was measured using Agilent 6890N Network GC System, and the lower limit of detection of less than 1 ppm by mass was not detected (ND).

Examples 5 and 6
A composition containing LiFSI as a main component was obtained in the same manner as in Example 4 except that the amount of LiF used was changed so that the molar ratio of HFSI / LiF shown in Table 8 was obtained. The analysis values are shown in Table 8.

Example 7
In a 100 mL flask made of PFA, 101.0 g (558 mmol) of HFSI and 14.5 g (558 mmol) of LiF were weighed. The reaction solution was heated to 150 ° C. at normal pressure (1013 hPa) and reacted for 15 minutes, and then the pressure was reduced to 50 kPa and aging was performed for 1 hour. Thereafter, the pressure was reduced to 10 kPa, and devolatilization was performed at 145 to 150 ° C. for 1 hour under a nitrogen flow of 10 mL / min. It cooled and obtained 103.3g of compositions which have LiFSI as a main component. The analysis values are shown in Table 8.

Comparative Example 2
[Fluorosulfonylimide synthesis step (fluorination step)]
990 g of butyl acetate was added to a Pyrex (registered trademark) reaction vessel A (internal volume 5 L) equipped with a stirrer under a nitrogen stream, and 110 g (514 mmol) of bis (chlorosulfonyl) imide was added thereto at room temperature (25 ° C.). It was dripped at.

  To the resulting bis (chlorosulfonyl) imide solution in butyl acetate, 55.6 g of zinc fluoride (540 mmol, 1.05 equivalents relative to bis (chlorosulfonyl) imide) was added at once at room temperature, and this was completely dissolved. The mixture was stirred at room temperature for 6 hours.

[Cation Exchange Step 1-Synthesis of Ammonium Salt]
To a Pyrex (registered trademark) reaction vessel B (internal volume: 3 L) equipped with a stirrer, 297 g (4360 mmol, 8.49 equivalents relative to bis (chlorosulfonyl) imide) of 25% by mass ammonia water was added. The reaction solution in the reaction vessel A was added dropwise to the reaction vessel B at room temperature with stirring of aqueous ammonia. After completion of the addition of the reaction solution, stirring was stopped, and the aqueous layer containing by-products such as zinc chloride was removed from the reaction solution divided into two layers, an aqueous layer and a butyl acetate layer, and ammonium bis (fluoro A butyl acetate solution of sulfonyl) imide was obtained.

¹⁹ F-NMR (solvent: deuterated acetonitrile) was measured using the obtained organic layer as a sample. In the obtained chart, the amount of trifluoromethylbenzene added as an internal standard substance, and the comparison between the integrated value of the peak derived from this and the integrated value of the peak derived from the target product, was included in the organic layer. The crude yield of ammonium bis (fluorosulfonyl) imide was determined (416 mmol).
¹⁹ F-NMR (solvent: deuterated acetonitrile): δ 56.0

[Cation Exchange Step 2-Synthesis of Lithium Salt]
With respect to ammonium bis (fluorosulfonyl) imide contained in the obtained organic layer, 133 g (834 mmol as Li) of a 15 mass% lithium hydroxide aqueous solution was added so that the amount of lithium was 2 equivalents. Stir for minutes. Thereafter, the aqueous layer was removed from the reaction solution to obtain a butyl acetate solution of lithium bis (fluorosulfonyl) imide.

  Using the obtained organic layer as a sample, it was confirmed by ICP emission spectroscopic analysis that protons of fluorosulfonylimide were exchanged for lithium ions. The concentration of lithium bis (fluorosulfonyl) imide in the organic layer was 7% by mass (yield: 994 g, yield of lithium bis (fluorosulfonyl) imide: 69.6 g).

The concentration of fluorosulfonylimide was measured by ¹⁹ F-NMR (solvent: deuterated acetonitrile) using the obtained organic layer as a sample, and the amount of trifluoromethylbenzene added as an internal standard substance in the measurement result chart. And the peak integration value derived from this and the peak integration value derived from the target product.

[Concentration process]
Using a rotary evaporator ("REN-1000", manufactured by IWAKI), part of the reaction solvent was distilled off from the butyl acetate solution of lithium bis (fluorosulfonyl) imide obtained in cation exchange step 2 under reduced pressure. 162 g of lithium bis (fluorosulfonyl) imide solution was obtained (concentration: 43% by mass).

  162 g of butyl acetate solution containing 69.6 g of lithium bis (fluorosulfonyl) imide was added to a 500 mL separable flask equipped with a dropping funnel, a condenser and a distillation receiver. Using a vacuum pump, the pressure inside the separable flask is reduced to 667 Pa, the separable flask is immersed in an oil bath heated to 55 ° C., and the butyl acetate solution in the separable flask is slowly heated while stirring. Thus, butyl acetate, which is a reaction solvent from the fluorosulfonylimide synthesis step, was distilled out. During the 10 minutes after the start of distillation, 1,2,4-trimethylbenzene having the same volume as the total amount of liquid collected in the distillation receiver was added as a poor solvent to the separable flask. Thereafter, butyl acetate (reaction solvent) in the system was concentrated while continuing to add 1,2,4-trimethylbenzene in the same volume as the distillate into the separable flask every 10 minutes. The white crystal of lithium bis (fluorosulfonyl) imide was precipitated by changing the blending ratio of bis and 1,2,4-trimethylbenzene. After the above operation was repeated until the supernatant in the separable flask became transparent, the flask was cooled to room temperature, and the resulting lithium bis (fluorosulfonyl) imide crystal suspension was filtered to obtain lithium bis (fluorosulfonyl). ) Imido crystals were collected by filtration. The time from the start of heating of the butyl acetate solution to the end of the concentration step was 6 hours, and the time required to start the precipitation of white crystals was 2 hours.

  Next, the obtained crystals were washed with a small amount of hexane, transferred to a flat bottom vat and dried under reduced pressure at 55 ° C. and 667 Pa for 12 hours to obtain white crystals of lithium bis (fluorosulfonyl) imide (yield: 65. 4g). The analysis values are shown in Table 8.

<Withstand voltage evaluation>
Using the samples obtained in Example 4 and Comparative Example 2, LSV (Linear Sweep Voltammetry) measurement was performed. Measured at a sweep rate of 0.5 mV / sec from 3 V to 7 V using HZ3000 manufactured by Hokuto Denko under the environment of 25 ° C. and dew point −40 ° C., using Li as the reference electrode, glassy carbon as the working electrode, and platinum as the counter electrode. Went. The measurement solution was an EC / EMC = 3/7 solution of 1M LiFSI. When the sample of Example 4 was used, the decomposition current value at 5 V was 0.003 mA / cm ² , but when the sample of Comparative Example 2 was used, the decomposition current value at 5 V was 0.25 mA / cm 2. ² .

<Battery evaluation>
Battery performance evaluation was performed using the samples obtained in Examples 4 to 6 and Comparative Example 2. The results are summarized in Table 9.

30mAh equivalent laminate study results 4.2V design positive electrode of the battery: LiCo1 / 3Ni1 / 3Mn1 / 3O 2 negative: Graphite separator: PE
* 1 Capacity measurement condition Charging: 4.2V 1C (30mA) constant current constant voltage charging 0.6mA termination ⇒ Discharging: 0.2C (6mA) / 1C (30mA) constant current discharging 2.75V termination 0.2C / 1C Ratio of each discharge capacity * 2 Discharge capacity measurement conditions Charging: 4.2V 1C (30mA) constant current constant voltage charging 0.6mA termination 25 ° C
⇒ 0 ° C rest 2 hours ⇒ Discharge: 1C (30mA) Constant current discharge 2.75V end 0 ° C
* 3 Charging capacity measurement conditions Discharge: 0.2C (6mA) constant current discharge End 2.75V 25 ℃
⇒ 0 ° C Rest 2 hours ⇒ Charging conditions 1C (30mA) 4.2V constant current charging * 4 Charging conditions: 4.2V 1C (30mA) constant current constant voltage charging 0.6mA termination 45 ° C
⇒ Discharge condition: 1C (30mA) 2.75V end 45 ° C

As described above, capacity deterioration at the time of standing at high temperature was suppressed by using a LiFSI composition containing a predetermined amount of F ⁻ ions and SO ₄ ²⁻ ions. The effect was particularly remarkable in a high voltage and high temperature environment.
As the presumed mechanism, it is considered that F ⁻ ions form a film on the positive electrode side, thereby suppressing cobalt elution in the positive electrode active material at a high temperature and suppressing capacity deterioration.
If the HF concentration is too high, HF corrodes the positive electrode active material or the positive electrode aluminum current collector and promotes metal elution, so the amount of HF is preferably 5000 ppm by mass or less.

Claims (4)

Containing 90% by mass or more of lithium bis (fluorosulfonyl) imide, containing more than 1000 ppm by mass of F ⁻ ions, and having a SO ₄ ^2- ion content of 6000 ppm by mass or less,
Lithium bis (fluorosulfonyl) imide composition. The content of HF is 5000 mass ppm or less,
The lithium bis (fluorosulfonyl) imide composition according to claim 1. Further, LiFSO ₃ is contained in an amount of 100 mass ppm to 5 mass%,
The lithium bis (fluorosulfonyl) imide composition according to claim 1 or 2. The pH of a solution obtained by dissolving 1 g of the lithium bis (fluorosulfonyl) imide composition according to any one of claims 1 to 3 in 30 mL of dehydrated methanol is 3 or more and 8 or less.
Lithium bis (fluorosulfonyl) imide composition.