JP7035579B2 - Additives for electrolytes - Google Patents

Description

The present invention relates to an additive for an electrolytic solution, and more particularly to an additive for an electrolytic solution composed of a neutral molecule having a trialkylsilyl group.

In recent years, portable electronic devices such as digital cameras, smartphones, and tablet devices have become widespread, and along with this, demand for energy storage devices such as secondary batteries that can be repeatedly used by charging, which are used as power sources for these devices, will increase significantly. At the same time, there is an increasing demand for higher capacity and higher energy density.
In these power storage devices, a solution in which an ionic conductive salt is dissolved in an aprotic organic solvent is generally used as an electrolytic solution.

By the way, in a power storage device aiming at high voltage operation, the withstand voltage of the electrolytic solution is a factor that determines the upper limit potential of the device, but under high voltage, the organic solvent and the ionic conductive salt constituting the electrolytic solution are exposed to the high voltage. Therefore, it may be electrically decomposed on the surface of the electrode, and an electrolytic solution having higher withstand voltage resistance is required.
As a technique for improving the withstand voltage of this electrolytic solution, a method of adding various additives to the electrolytic solution has been reported (see, for example, Patent Documents 1 to 4), but the effect of improving the withstand voltage and the suppression of internal resistance increase are achieved. There is room for further improvement.
In addition, although ionic liquids are known to have a high withstand voltage, they have a problem in terms of ionic conductivity in the low to normal temperature range compared to general organic solvents, and are suitable for devices that operate at high voltage at low temperatures. Is unsuitable.

In view of these points, the applicant has improved the withstand voltage of the electrolytic solution by adding the compound having a silicon-containing sulfonic acid anion to the existing electrolytic solution, and by using this electrolytic solution, the service life performance is improved. It has already been reported that a good storage device such as a secondary battery or a capacitor can be obtained (Patent Document 5).
However, when the compound having a silicon-containing sulfonic acid anion described in Patent Document 5 is added to an electrolytic solution containing a LiPF ₆ -based electrolyte, it rapidly undergoes salt exchange with the PF ₆ anion, making it difficult to use an electrolytic solution solvent. Since it may be converted into a soluble Li salt and precipitated, it may be difficult to apply the lithium ion battery to the electrolytic solution.

Japanese Unexamined Patent Publication No. 2000-123867 Japanese Unexamined Patent Publication No. 2007-165125 Japanese Unexamined Patent Publication No. 2010-205870 Japanese Unexamined Patent Publication No. 2012-038900 Japanese Unexamined Patent Publication No. 2017-62955

The present invention has been made in view of such circumstances, and is a new additive for an electrolytic solution that can improve the withstand voltage of the electrolytic solution and can be applied to the electrolytic solution of a lithium ion secondary battery, and the present invention. It is an object of the present invention to provide a predetermined neutral molecule having a trialkylsilyl group suitable for an additive in the molecule .

As a result of diligent studies to achieve the above object, the present inventor has added a predetermined neutral molecule having at least one trialkylsilyl group in the molecule to an existing electrolytic solution, or the electrolytic solution itself. The present invention has been completed by finding that the withstand voltage is improved by using the product as a voltage.

〔式中、Ｒ¹は、互いに独立して炭素数１～８のアルキル基を表し、Ｒ²は、互いに独立して炭素数１～８のアルキル基を表し、Ａは、炭素数１～１０のアルキレン基を表し、Ｘは、単結合、メチレン基および下記式（２）～（４）で表されるいずれかの連結基から選ばれる１種を表し、ｍは、１～３の整数を、ｎは、０～２の整数を表すが、ｍ＋ｎは、Ｘが単結合、メチレン基、下記式（２）で表される連結基または下記式（３）で表される連結基の場合は２であり、Ｘが下記式（４）で表される連結基の場合は３である。

（式（３）中、Ｒ³は、炭素数１～８のアルキル基を表す。）〕
２． 前記ｍが、２または３であり、前記ｎが、０である１の電解液用添加剤、
３． 前記Ｒ¹が、全てメチル基である１または２の電解液用添加剤、
４． 前記Ａが、炭素数２～５のアルキレン基である１～３のいずれかの電解液用添加剤、
５． 下記式（１Ａ）～（１Ｄ）で表されるいずれかの化合物からなる１の電解液用添加剤、

（式中、Ｍｅは、メチル基を意味する。）
６． 電解液の耐電圧向上剤である１～５のいずれかの電解液用添加剤、
７． 電解液用溶媒である１～５のいずれかの電解液用添加剤、
８． １～７のいずれかの電解液用添加剤と、有機溶媒と、電解質塩とを含む電解液、
９． 前記有機溶媒が、カーボネート類を含む８の電解液、
１０． 前記有機溶媒が、２種以上のカーボネート類を含む９の電解液、

１１． １～７のいずれか１項記載の電解液用添加剤と、電解質塩とを含み、有機溶媒を含まない電解液、
１２． ８～１１のいずれかの電解液を用いて構成される蓄電デバイス、
１３． １～７のいずれかの電解液用添加剤を用いて構成される蓄電デバイス、
１４． 二次電池または電気二重層キャパシタである１２または１３の蓄電デバイス、
１５． １～７のいずれかの電解液用添加剤を、溶媒および電解質塩を含む電解液に加え、電解液の耐電圧を向上させる方法、
１６． 下記式（１Ｂ）で表される化合物、

（式中、Ｍｅは、メチル基を意味する。）
１７． 下記式（１Ｄ）で表される化合物

（式中、Ｍｅは、メチル基を意味する。）
を提供する。 That is, the present invention
1. 1. An additive for an electrolytic solution, which is represented by the formula (1) and is composed of a neutral compound having a trialkylsilyl group in the molecule.

[In the formula, R ¹ represents an alkyl group having 1 to 8 carbon atoms independently of each other, R ² represents an alkyl group having 1 to 8 carbon atoms independently of each other, and A represents an alkyl group having 1 to 10 carbon atoms. Represents the alkylene group of, X represents one selected from a single bond, a methylene group, and any of the linking groups represented by the following formulas (2) to (4), and m represents an integer of 1 to 3. , N represents an integer of 0 to 2, and m + n is a single bond, a methylene group, a linking group represented by the following formula (2) or a linking group represented by the following formula (3). 2 and 3 when X is a linking group represented by the following formula (4).

(In formula (3), R ³ represents an alkyl group having 1 to 8 carbon atoms.)]
2. 2. 1 electrolyte solution additive, wherein m is 2 or 3 and n is 0.
3. 3. Additive for electrolytic solution of 1 or 2 in which R ¹ is all methyl groups,
4. The additive for an electrolytic solution according to any one of 1 to 3, wherein A is an alkylene group having 2 to 5 carbon atoms.
5. 1 Additive for electrolytic solution, which comprises any of the compounds represented by the following formulas (1A) to (1D).

(In the formula, Me means a methyl group.)
6. An additive for an electrolytic solution according to any one of 1 to 5, which is an agent for improving the withstand voltage of the electrolytic solution.
7. An additive for an electrolytic solution according to any one of 1 to 5, which is a solvent for an electrolytic solution,
8. An electrolytic solution containing any of the additives 1 to 7 for an electrolytic solution, an organic solvent, and an electrolyte salt.
9. 8 electrolytic solutions containing carbonates as the organic solvent,
10. Nine electrolytic solutions containing two or more kinds of carbonates as the organic solvent,

11. An electrolytic solution containing the additive for an electrolytic solution according to any one of 1 to 7 and an electrolyte salt and not containing an organic solvent.
12. A power storage device configured using any of the electrolytic solutions 8 to 11.
13. A power storage device configured using any of the electrolyte additives 1 to 7.
14. 12 or 13 energy storage devices, which are secondary batteries or electric double layer capacitors,
15. A method of adding the additive for an electrolytic solution according to any one of 1 to 7 to an electrolytic solution containing a solvent and an electrolytic salt to improve the withstand voltage of the electrolytic solution.
16. The compound represented by the following formula (1B),

(In the formula, Me means a methyl group.)
17. Compound represented by the following formula (1D)

(In the formula, Me means a methyl group.)
I will provide a.

The withstand voltage can be improved by adding the neutral compound having the trialkylsilyl group of the present invention in the molecule to the existing electrolytic solution or using it as the electrolytic solution.
Since this compound is not ionic, it does not precipitate due to salt exchange with the electrolyte and can be used in a metal ion battery system without any problem.
The power storage device provided with the electrolytic solution containing the additive for the electrolytic solution of the present invention has an increased operating upper voltage limit, and can increase the voltage and the capacity density.

FIG. 3 is a ^{1 1} H-NMR spectrum diagram of the compound (1B) obtained in Synthesis Example 1. 6 is a ¹ H-NMR spectrum diagram of the compound (1D) obtained in Synthesis Example 2. It is a figure which shows the cyclic voltammetry measurement result (oxidation side) of Examples 1 to 4 and Comparative Example 1. FIG. It is a figure which shows the cyclic voltammetry measurement result (reduction side) of Examples 2-4 and Comparative Example 1.

Hereinafter, the present invention will be described in more detail.
The additive for an electrolytic solution according to the present invention comprises a neutral compound having a trialkylsilyl group in the molecule represented by the formula (1).

In the formula (1), R ¹ represents an alkyl group having 1 to 8 carbon atoms independently of each other, and R ² represents an alkyl group having 1 to 8 carbon atoms independently of each other.
The alkyl group having 1 to 8 carbon atoms may be linear, branched or cyclic, and may be, for example, methyl, ethyl, n-propyl, i-propyl, c-propyl, n-butyl, i-butyl, s-. Examples thereof include butyl, t-butyl, c-butyl, n-pentyl, c-pentyl, n-hexyl, c-hexyl, n-heptyl, n-octyl, 2-ethylhexyl group and the like.
Among them, as R ¹ and R ² , an alkyl group having 1 to 4 carbon atoms is preferable, an alkyl group having 1 to 3 carbon atoms is more preferable, and a methyl group is even more preferable.

A represents an alkylene group having 1 to 10 carbon atoms.
The alkylene group having 1 to 10 carbon atoms may be linear, branched or cyclic, and may be, for example, methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene or decamethylene. Methylene and the like can be mentioned.
Among them, as A, an alkylene group having 2 to 5 carbon atoms is preferable, an ethylene, trimethylene and tetramethylene groups are more preferable, and an ethylene and trimethylene group are even more preferable.

X represents one selected from a single bond, a methylene group and any of the linking groups represented by the following formulas (2) to (4).

R ³ in the formula (3) represents an alkyl group having 1 to 8 carbon atoms, and specific examples thereof include the same groups as those exemplified in R ¹ above.
Among them, as R ³ , an alkyl group having 1 to 4 carbon atoms is preferable, and a methyl group is more preferable.

In the formula (1), m represents an integer of 1 to 3, n represents an integer of 0 to 2, and m + n is a single bond, a methylene group, a linking group represented by the above formula (2), or m + n. It is 2 in the case of the linking group represented by the above formula (3), and 3 in the case of the linking group represented by the above formula (4).
In particular, a compound in which m is 2 or 3 and n is 0 is preferable.

Specific examples of the compound represented by the formula (1) include, but are not limited to, those represented by the following formulas (1A) to (1D).

（式中、Ｍｅは、メチル基を意味する。）

(In the formula, Me means a methyl group.)

The neutral compounds having the above-mentioned various trialkylsilyl groups in the molecule can be synthesized by a known method.
For example, compound (1B) can be synthesized by a method such as reacting 1,1'-carbonyldiimidazole with 3-trimethylsilyl-1-propanol.
In addition, compound (1D) can be synthesized by a method such as reacting methylphosphonic acid dichloride with 3-trimethylsilyl-1-propanol in the presence of a base such as diisopropylethylamine.
Both compound (1A) and compound (1C) are known substances, and compound (1A) should be synthesized, for example, by the method described in Document M. Philipp et al., Electrochimica Acta 173 (2015) 687. The compound (1C) can be synthesized, for example, by the method described on page 340 of the New Experimental Chemistry Course 12 Organometallic Chemistry Maruzen Co., Ltd., published on March 20, 1976.

The additive for an electrolytic solution of the present invention can be used by adding it to an electrolytic solution containing an organic solvent and an electrolyte salt.
As the organic solvent, various organic solvents conventionally used as a solvent for an electrolytic solution can be appropriately selected and used, and specific examples thereof include alcohols such as methanol and ethanol; dibutyl ether, 1,2-. Dimethoxyethane, 1,2-ethoxymethoxyethane, methyl diglime, methyl triglime, methyl tetraglime, ethyl glyme, ethyl diglime, butyl diglyme, ethyl cellsolve, ethylcarbitol, butylcellsolve, butylcarbitol, etc. Chain ethers; heterocyclic ethers such as tetrahydrofuran, 2-methyltetrachloride, 1,3-dioxolane, 4,4-dimethyl-1,3-dioxane; γ-butyrolactone, γ-valerolactone, δ-valero Sulfones such as lactones, 3-methyl-1,3-oxazolidin-2-one, 3-ethyl-1,3-oxazolidin-2-one; N-methylformamide, N, N-dimethylformamide, N-methylacetamide , N-Methylpyrrolidinone and other amides; diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, propylene carbonate, ethylene carbonate, butylene carbonate and other carbonates; 1,3-dimethyl-2-imidazolidinone and other imidazolines; acetonitrile , Nitriles such as propionitrile; dinitriles such as adiponitrile and glutaronitrile; sulfones such as sulfolane, ethylmethyl sulfone, ethyl2-methoxyethyl sulfone; phosphoric acid esters such as methylphosphate and triethylphosphate, and these. Fluoro Substituents and the like can be mentioned, and these can be used alone or in combination of two or more.
Among them, an organic solvent containing carbonates is preferable, and an organic solvent containing two or more kinds of carbonates is even more preferable.

On the other hand, the electrolyte salt is appropriately selected according to the type of power storage device, and specific examples thereof include lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis (trifluoromethanesulfonyl) amide, and lithium bis (fluoro). Lithium salts such as sulfonyl) amide, lithium perchlorate, lithium acetate, lithium trifluoroacetate, lithium benzoate, lithium p-toluenesulfonate, lithium nitrate, lithium bromide, lithium iodide; tetramethylammonium hexafluorophosphate, Tertiary ammonium salts such as tetraethylammonium hexafluorophosphate, tetrapropylammonium hexafluorophosphate, methyltriethylammonium hexafluorophosphate, tetraethylammonium tetrafluoroborate, tetraethylammonium perchlorate; lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluoro). Sulfonyl) imide and the like.
In particular, since the additive for an electrolytic solution of the present invention is a neutral molecule, it can be suitably used even when a lithium salt such as lithium hexafluorophosphate is used as an electrolyte salt.

The concentration of the electrolyte salt in the electrolytic solution is not particularly limited and is usually about 0.5 to 3 mol / L, but preferably about 0.8 to 2 mol / L, preferably 0.9 to 1.5 mol / L. About L is more preferable.

The amount of the additive for the electrolytic solution of the present invention added in the electrolytic solution is not particularly limited as long as the withstand voltage improving effect is exhibited, but in consideration of efficiently exhibiting the withstand voltage improving effect, it is considered. In the whole electrolytic solution (100% by mass), 0.01% by mass or more is preferable, 0.05% by mass or more is more preferable, 0.1% by mass or more is further preferable, and 0.5% by mass or more is further preferable. ..
Further, the upper limit thereof is not particularly limited because it can be used as a solvent.

Further, the additive for an electrolytic solution of the present invention can be used as a solvent for an electrolytic solution.
In this case, only the additive for the electrolytic solution of the present invention may be used as the solvent for the electrolytic solution, or may be used in combination with the above-mentioned solvents for various electrolytic solutions. From the viewpoint of further increasing the withstand voltage of the electrolytic solution, it is preferable to use only the additive for the electrolytic solution of the present invention as the solvent for the electrolytic solution, but in consideration of the solubility of the electrolyte salt, it is appropriately mixed with another electrolytic solution. May be.

The power storage device in the present invention is not particularly limited, and various power storage devices such as an electric double layer capacitor, a lithium ion capacitor, a redox capacitor, a lithium secondary battery, a lithium ion secondary battery, a lithium air battery, and a proton polymer battery are stored. Devices are mentioned.
The power storage device of the present invention is not particularly limited as long as it includes an electrolytic solution containing the above-mentioned additive for an electrolytic solution, for example, a positive electrode current collector and a positive electrode active material layer formed on the surface thereof. A general secondary battery including a positive electrode having a positive electrode, a negative electrode having a negative electrode current collector and a negative electrode active material layer formed on the surface thereof, and a separator interposed between these electrodes, and a positive electrode (air electrode) layer. In an air cell having an electrolytic solution layer arranged between the electrode and the negative electrode layer and each electrode, an electrolytic solution containing the electrolytic solution additive of the present invention is applied, or a pair of polarized electrodes and between these electrodes. An electric double-layer capacitor including a separator interposed therebetween and an electrolytic solution, to which an electrolytic solution containing an additive for an electrolytic solution of the present invention is applied can be mentioned.

The materials constituting the secondary battery may be appropriately selected from conventionally known materials and used, and are not particularly limited, but examples thereof are as follows.
Specific examples of the positive electrode current collector include an aluminum foil, an aluminum alloy foil, and the like, and a three-dimensional porous body such as a foam or a non-woven fabric thereof can also be used for the current collector.
Specific examples of the positive electrode active material include a carbonaceous material such as activated carbon and carbon nanotubes, an olivine type crystal structure, a layered rock salt type crystal structure, or a spinel type crystal structure capable of reversibly supporting lithium. Examples include lithium oxide. Examples of the activated carbon raw material include palm, phenol resin, petroleum coke and the like, and examples of the activated carbon raw material activation method include a steam activation method and a molten alkali activation method. As the lithium oxide, a composite oxide represented by the general formula LiMPO ₄ (M is one or more of Fe (II), Mn (II), Co (II), Ni (II)) and lithium cobalt oxide (LiCoO). ₂ ), LiNiO ₂ , LiMnO ₂ , Li ₂ MnO ₃ , LiNi _0.8 Co _0.2 O ₂ and other NiCo-based materials.

Specific examples of the negative electrode current collector include copper foil, copper alloy foil, nickel foil, nickel alloy foil, stainless steel foil, aluminum foil, aluminum alloy foil and the like.
Specific examples of the negative electrode active material are not particularly limited as long as they can occlude and release lithium ions, but carbonaceous materials (such as graphite), silicon oxides, silicon alloys, tin oxides, tin alloys, and lithium. Metals capable of forming simple substances or lithium alloys include, for example, aluminum, lead, tin, indium, bismuth, silver, barium, calcium, mercury, palladium, platinum, tellurium, zinc, lanthanum and the like. These may be used alone or in combination of two or more. Carbonaceous materials or lithium composite oxides are preferred from a safety standpoint. Further, those containing Ti (titanium), Li (lithium) or both Ti and Li (for example, lithium titanate and the like) are preferable from the viewpoint of high current density charge / discharge characteristics.

Further, the positive electrode active material and the negative electrode active material may be used together with the conductive material.
Examples of the conductive material include carbon black, ketjen black, acetylene black, carbon whisker, carbon fiber, natural graphite, artificial graphite, titanium oxide, ruthenium oxide, aluminum, nickel and the like.

For the positive electrode and negative electrode active material layers, an electrode slurry containing the active material, the binder polymer, and the conductive material and the solvent described above, if necessary, is applied onto the current collector and dried under heating as necessary. Can be formed.
The binder polymer can be appropriately selected from known materials and used, for example, polyvinylidene fluoride (PVdF), polyvinylpyrrolidone, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-. Hexafluoropropylene copolymer [P (VDF-HFP)], vinylidene fluoride-trifluoroethylene trifluoride copolymer [P (VDF-CTFE)], polyvinyl alcohol, ethylene-propylene-diene ternary copolymer, Examples thereof include styrene-butadiene rubber and carboxymethyl cellulose (CMC).
The solvent is selected according to the type of the binder polymer, but generally, N-methyl-2-pyrrolidone or water is used.
The electrode on which the active material layer is formed may be pressed if necessary.

Specific examples of the separator include polyolefin-based separators such as polyethylene and polypropylene, polyester-based separators such as polyethylene terephthalate, polyamide-based separators, polyimide-based separators, cellulose-based separators, and glass fiber-based separators.

Further, the materials constituting the electric double layer capacitor may be appropriately selected from conventionally known materials and used, and are not particularly limited, but examples thereof are as follows.
Examples of a general polar electrode include a current collector coated with a composition containing a carbonaceous material, a binder polymer, and, if necessary, a conductive material.
The carbonaceous material is not particularly limited, and examples thereof include various conventionally known carbonaceous materials, and examples thereof include activated carbon, graphite, graphene, carbon nanotubes, carbon nanofibers, and carbon nanohorns.
Specific examples of the positive electrode current collector include aluminum foil and aluminum alloy foil.
Specific examples of the negative electrode current collector include copper foil, copper alloy foil, nickel foil, nickel alloy foil, stainless steel foil and the like.
In addition, examples of the binder polymer and the conductive material include the same as those exemplified for the secondary battery.
Further, a solvent may be used when preparing the above composition. This solvent is selected according to the type of the binder polymer, and in this case as well, N-methyl-2-pyrrolidone and water are suitable.
Specific examples of the separator include those similar to those exemplified for the secondary battery.

In the power storage device of the present invention, for example, a device structure formed by interposing a separator between a pair of electrodes is laminated, folded, or wound to form a coin shape or the like as necessary, and this is formed into a battery can or a battery can. After being housed in a battery container such as a laminate pack, it is filled with an electrolytic solution containing the additive for the electrolytic solution of the present invention, and if it is a battery can, it is sealed, while if it is a laminated pack, it is heat-sealed (heat welding). Can be obtained.

Hereinafter, the present invention will be described in more detail with reference to synthetic examples, examples and comparative examples, but the present invention is not limited to the following examples. The analyzer and conditions used are as follows.
[1] ^{1 1} H-NMR spectrum device: ECZ-400S manufactured by JEOL Ltd.
[2] Cyclic voltammetry device: Electrochemical measuring device HSV-100 manufactured by Hokuto Denko Co., Ltd.
Constant temperature constant temperature bath: ESPEC CO., LTD. SU-241
Measurement conditions: In a dry environment, the measurement was performed at a sweep rate of 5 mV / sec using a glassy carbon electrode as the working electrode, a platinum electrode as the counter electrode, and an Ag / AgNO ₃ electrode as the reference electrode at a temperature of 25 ° C.

[1] Synthesis of Additives for Electrolyte Solution [Synthesis Example 1] Synthesis of Compound (1B)

6.49 g of 1,1'-carbonyldiimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) was weighed into an eggplant-shaped flask, and the flask was ice-cooled. 11.64 g of 3-trimethylsilyl-1-propanol (manufactured by Sigma-Aldrich) was slowly added dropwise under ice-cooling and in a stirred state.
After completion of the dropping, the ice bath was removed, and after returning to room temperature, the mixture was heated to 80 ° C. in an oil bath, and stirring was continued at this temperature for 2 hours. After removing the oil bath and returning to room temperature, 100 ml of hexane (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was transferred to a separating funnel. After adding 100 ml of water, shaking and allowing to stand, and performing a washing operation to remove the lower aqueous layer three times, the upper layer was subjected to solvent distillation using an evaporator and then a vacuum pump to concentrate. The obtained reaction mixture was purified by subjecting it to a silica gel column having a developing solvent of hexane: ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) = 4: 1 (v / v) to obtain 10.06 g of the target compound (1B). Obtained. A ¹ H-NMR chart (solvent: deuterated chloroform) of compound (1B) is shown in FIG.

[Synthesis Example 2] Synthesis of compound (1D)

7.67 g of methylphosphonic acid dichloride (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.32 g of 1H-tetrazole (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in 709 ml of toluene (manufactured by Wako Pure Chemical Industries, Ltd.). While vigorously stirring, 15.20 g of 3-trimethylsilyl-1-propanol and 10.86 ml of diisopropylethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) were added dropwise over about 2 hours, and then the mixture was stirred overnight. The next day, the reaction solution was charged to silica gel as it was, and separated and purified by silica gel column chromatography using diethyl ether (manufactured by Kanto Chemical Co., Ltd.) -ethyl acetate = 9: 1 (v / v) to obtain the desired product. 11.54 g of the compound (1D) was obtained. A ¹ H-NMR chart (solvent: deuterated chloroform) of compound (1D) is shown in FIG.

[Synthesis Example 3] Synthesis of compound (1A)

Compound (1A) is a known substance and can be synthesized by a known method.
Here, after the reaction of methylchloroformate with 3-triethylsilylpropanol, the compound (1A) was obtained by distillation purification.

[Synthesis Example 4] Synthesis of compound (1C)

Compound (1C) is a known substance and can be synthesized by a known method.
Here, the compound (1C) was synthesized by the method described on page 340 of the New Experimental Chemistry Course 12 Organometallic Chemistry Maruzen Co., Ltd., published on March 20, 1976.

[2] Preparation of electrolytic solution [Example 1]
Compound (1B) was added to a 1MLiPF ₆ dimethyl carbonate (DMC) solution to a concentration of 1% by mass to prepare an electrolytic solution.

[Examples 2 to 4]
An electrolytic solution was prepared in the same manner as in Example 1 except that compound (1D), compound (1A) or compound (1C) was used.

Cyclic voltammetry measurements were performed on the electrolytic solutions prepared in Examples 1 to 4 and the 1MLiPF ₆ DMC solution (Comparative Example 1). The measurement results are shown in FIGS. 3 and 4.

As shown in FIG. 3, it can be seen that the electrolytic solution prepared by adding the additive for the electrolytic solution of the present invention has an improved withstand voltage on the oxidation side as compared with the electrolytic solution to which the additive is not added. On the other hand, as shown in FIG. 4, it can be seen that the potential window on the reduction side is not significantly affected.
In FIGS. 3 and 4, α represents compound (1D), β represents compound (1C), γ represents compound (1A), and δ represents compound (1B).

Claims (17)

An additive for an electrolytic solution, which is represented by the formula (1) and is composed of a neutral compound having a trialkylsilyl group in the molecule.

[In the formula, R ¹ represents an alkyl group having 1 to 8 carbon atoms independently of each other, R ² represents an alkyl group having 1 to 8 carbon atoms independently of each other, and A represents an alkyl group having 1 to 10 carbon atoms. Represents the alkylene group of, X represents one selected from any of the linking groups represented by the following formulas (2) to (4), m is an integer of 2 or 3, and n is 0 . M + n is 2 when X is a linking group represented by the following formula (2) or a linking group represented by the following formula (3), and X is the following formula (4). In the case of a linking group represented by, it is 3.

(In formula (3), R ³ represents an alkyl group having 1 to 8 carbon atoms.)] The R ¹ represents an alkyl group having 1 to 4 carbon atoms independently of each other, and the X represents one selected from any of the linking groups represented by the formulas (2) and (3). The additive for an electrolytic solution according to claim 1, wherein m is 2 . The additive for an electrolytic solution according to claim 1 or 2, wherein R ¹ is an all methyl group. The additive for an electrolytic solution according to any one of claims 1 to 3, wherein A is an alkylene group having 2 to 5 carbon atoms. The additive for an electrolytic solution according to claim 1, which comprises any of the compounds represented by the following formulas (1B) and (1D).

(In the formula, Me means a methyl group.) The additive for an electrolytic solution according to any one of claims 1 to 5, which is an agent for improving the withstand voltage of the electrolytic solution. The additive for an electrolytic solution according to any one of claims 1 to 5, which is a solvent for an electrolytic solution. An electrolytic solution containing the additive for an electrolytic solution according to any one of claims 1 to 7, an organic solvent, and an electrolyte salt. The electrolytic solution according to claim 8, wherein the organic solvent contains carbonates. The electrolytic solution according to claim 9, wherein the organic solvent contains two or more kinds of carbonates. An electrolytic solution containing the additive for an electrolytic solution according to any one of claims 1 to 7 and an electrolyte salt, and containing no organic solvent. A power storage device configured by using the electrolytic solution according to any one of claims 8 to 11. A power storage device configured by using the additive for an electrolytic solution according to any one of claims 1 to 7. The power storage device according to claim 12 or 13, which is a secondary battery or an electric double layer capacitor. A method for improving the withstand voltage of an electrolytic solution by adding the additive for an electrolytic solution according to any one of claims 1 to 7 to an electrolytic solution containing a solvent and an electrolytic salt. A compound represented by the following formula (1B).

(In the formula, Me means a methyl group.) A compound represented by the following formula (1D).

(In the formula, Me means a methyl group.)

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