JP2017004690A - Electrolyte, electrochemical device, lithium ion secondary battery, and module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte capable of obtaining an electrochemical device or a module such as a lithium ion secondary battery, excellent in high-temperature storage characteristics, preventing resistance from increasing even after high-temperature storage.SOLUTION: The electrolyte includes: at least one kind selected from a group composed of amine (1), amide (2), and oxalic acid dialkyl (3); and a specific cyclic dicarbonyl compound. The cyclic dicarbonyl compound has 0.001 to 10 mass% to the electrolyte.SELECTED DRAWING: None

Description

The present invention relates to an electrolytic solution, an electrochemical device, a lithium ion secondary battery, and a module.

With the recent reduction in weight and size of electrical products, development of lithium-ion secondary batteries having high energy density is in progress. Further, as the application field of lithium ion secondary batteries expands, improvement of battery characteristics is desired. In particular, when lithium ion secondary batteries are used in vehicles, the battery characteristics will become increasingly important.

Patent Document 1 discloses a nonaqueous electrolyte battery composed of a positive electrode, a negative electrode using lithium as an active material, and a nonaqueous electrolyte solution as a nonaqueous electrolyte battery excellent in storage characteristics and cycle characteristics. A non-aqueous electrolyte battery is described in which a cyclic compound containing at least two ketone groups is added to the non-aqueous electrolyte.

Patent Document 2 discloses that a negative electrode containing graphite as a negative electrode material capable of inserting and extracting lithium, a positive electrode, and a mixed non-aqueous solvent containing cyclic carbonate and chain carbonate in a lithium salt and 0.5 to 10 wt. % Non-aqueous electrolyte secondary battery composed of an electrolyte solution in which% cyclic acid anhydride is dissolved is described.

Patent Document 3 discloses a compound having a specific ionic metal complex structure, A ^{a +} (PF ₆ ⁻ ) ^a , A ^{a +} (ClO ₄ ⁻ ) _a , A ^{a +} (BF ₄ ⁻ ) _a , A ^{a +} (AsF ₆ ^-) _a or _{^{a a + (SbF 6, -}} ) of at least one consisting of an electrochemical device for the electrolyte of the compounds represented by _a is described.

Japanese Patent Laid-Open No. 5-08168 JP 2000-268859 A Japanese Patent Laid-Open No. 2002-164082

However, the conventional non-aqueous electrolyte battery has a problem that when it is left in a high-temperature environment or repeated charge and discharge, the discharge capacity decreases and the resistance increases.

The present invention has been made in view of the above situation, and obtains an electrochemical device or module such as a lithium ion secondary battery that has excellent storage characteristics at high temperatures and does not increase in resistance even after storage at high temperatures. It is an object to provide an electrolyte solution that can be used.

The present invention includes an amine (1) represented by the general formula (1), an amide (2) represented by the general formula (2), and a dialkyl oxalate (3) represented by the general formula (3). At least one selected and at least one cyclic dicarbonyl compound selected from the group consisting of the compound (4) represented by the general formula (4) and the compound (5) represented by the general formula (5); And the cyclic dicarbonyl compound is 0.001 to 10% by mass with respect to the electrolytic solution.

（式中、Ｒ^１１及びＲ^１２は、同一又は異なってもよく、炭素数１〜７のアルキル基、Ｒｆ^１３は炭素数１〜７のフッ素化アルキル基） General formula (1):

(In the formula, R ¹¹ and R ¹² may be the same or different, the alkyl group having 1 to 7 carbon atoms, and Rf ¹³ is a fluorinated alkyl group having 1 to 7 carbon atoms).

（式中、Ｒ^２１及びＲ^２２は、同一又は異なってもよく、炭素数１〜７のアルキル基、Ｒ^２３は炭素数１〜７のアルキル基又は炭素数１〜７のフッ素化アルキル基） General formula (2):

(In the formula, R ²¹ and R ²² may be the same or different, and an alkyl group having 1 to 7 carbon atoms, R ²³ is an alkyl group having 1 to 7 carbon atoms or a fluorinated alkyl group having 1 to 7 carbon atoms).

（式中、Ｒ^３１及びＲ^３２は、同一又は異なっていてもよく、炭素数１〜７のアルキル基） General formula (3):

(In the formula, R ³¹ and R ³² may be the same or different and have 1 to 7 carbon atoms)

（Ａ^ａ＋は金属イオン、水素イオン又はオニウムイオン。ａは１〜３の整数、ｂは１〜３の整数、ｐはｂ／ａ、ｎ^４３は１〜４の整数、ｎ^４１は０〜８の整数、ｎ^４２は０又は１、Ｚ^４１は遷移金属、周期律表のＩＩＩ族、ＩＶ族又はＶ族の元素。
Ｘ^４１は、Ｏ、Ｓ、炭素数１〜１０のアルキレン基、炭素数１〜１０のハロゲン化アルキレン基、炭素数６〜２０のアリーレン基又は炭素数６〜２０のハロゲン化アリーレン基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよく、またｎ^４２が１でｎ^４３が２〜４のときにはｎ^４３個のＸ^４１はそれぞれが結合していてもよい）
Ｌ^４１は、ハロゲン原子、シアノ基、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基、炭素数６〜２０のハロゲン化アリール基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよく、またｎ^４１が２〜８のときにはｎ^４１個のＬ^４１はそれぞれが結合して環を形成してもよい）又は−Ｚ^４３Ｙ^４３。
Ｙ^４１、Ｙ^４２及びＺ^４３は、それぞれ独立でＯ、Ｓ、ＮＹ^４４、炭化水素基又はフッ素化炭化水素基。Ｙ^４３及びＹ^４４は、それぞれ独立でＨ、Ｆ、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基又は炭素数６〜２０のハロゲン化アリール基（アルキル基、ハロゲン化アルキル基、アリール基及びハロゲン化アリール基はその構造中に置換基、ヘテロ原子を持っていてもよく、Ｙ^４３又はＹ^４４が複数個存在する場合にはそれぞれが結合して環を形成してもよい）） General formula (4):

(A ^{a +} is a metal ion, hydrogen ion or onium ion. A is an integer of 1 to 3, b is an integer of 1 to 3, p is b / a, n ⁴³ is an integer of 1 to 4, n ⁴¹ is 0 to 8 , N ⁴² is 0 or 1, Z ⁴¹ is a transition metal, a group III, IV or V element of the periodic table.
X ⁴¹ is O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (alkylene group). , a halogenated alkylene group, an arylene group, and halogenated arylene group substituent in its structure, may have a hetero atom, and n ⁴² is ⁴³ pieces of n when n ⁴³ at 1 is 2 to 4 X ⁴¹ may be bonded to each other)
L ⁴¹ is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms ( The alkylene group, halogenated alkylene group, arylene group, and halogenated arylene group may have a substituent or a hetero atom in the structure. When n ⁴¹ is 2 to 8, n ⁴¹ L ⁴¹ is each may be combined with each other to form a ring) or ^-Z 43 ^{Y 43.}
Y ⁴¹ , Y ⁴² and Z ⁴³ are each independently O, S, NY ⁴⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ⁴³ and Y ⁴⁴ are each independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogen having 6 to 20 carbon atoms. Aryl group (an alkyl group, a halogenated alkyl group, an aryl group and a halogenated aryl group may have a substituent or a hetero atom in the structure thereof, and when there are a plurality of Y ⁴³ or Y ^44, May combine to form a ring)))

（式中、ｎ^５１は０又は１、ｎ^５２は０又は１、Ｚ^５１は遷移金属、周期律表のＩＩＩ族、ＩＶ族又はＶ族の元素。
Ｘ^５１は、Ｏ、Ｓ、炭素数１〜１０のアルキレン基、炭素数１〜１０のハロゲン化アルキレン基、炭素数６〜２０のアリーレン基又は炭素数６〜２０のハロゲン化アリーレン基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよい）。
Ｙ^５１及びＹ^５２は、それぞれ独立でＯ、Ｓ、ＮＹ^５４、炭化水素基又はフッ素化炭化水素基。Ｙ^５４はＨ、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基、炭素数６〜２０のハロゲン化アリール基（アルキル基、ハロゲン化アルキル基、アリール基及びハロゲン化アリール基はその構造中に置換基、ヘテロ原子を持っていてもよく、Ｙ^５４が複数個存在する場合にはそれぞれが結合して環を形成してもよい）） General formula (5):

(In the formula, n ⁵¹ is 0 or 1, n ⁵² is 0 or 1, Z ⁵¹ is a transition metal, a group III, group IV or group V element of the periodic table.
X ⁵¹ represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (alkylene group). , A halogenated alkylene group, an arylene group, and a halogenated arylene group may have a substituent or a hetero atom in the structure thereof.
Y ⁵¹ and Y ⁵² are each independently O, S, NY ⁵⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ⁵⁴ is H, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms (an alkyl group, a halogenated group). The alkyl group, aryl group and halogenated aryl group may have a substituent or a hetero atom in the structure thereof, and when there are a plurality of Y ^{54 s} , they may be bonded to form a ring) )

The electrolytic solution includes at least one compound (α) selected from the group consisting of amine (1) and amide (2), and the content of the compound (α) is 0.001 to 20 ppm in the electrolytic solution. It is preferable that

The electrolytic solution contains a dialkyl oxalate (3), and the content of the dialkyl oxalate (3) is preferably 0.001 to 10 ppm in the electrolytic solution.

The present invention is also an electrochemical device comprising the above-described electrolytic solution.

The present invention is also a lithium ion secondary battery comprising the above-described electrolytic solution.

The present invention is also a module comprising the above-described electrochemical device or the above-described lithium ion secondary battery.

The electrolytic solution of the present invention has excellent storage characteristics at high temperatures, and the resistance does not increase even after storage at high temperatures.

Hereinafter, the present invention will be specifically described.

The electrolytic solution of the present invention contains at least one selected from the group consisting of amine (1), amide (2) and dialkyl oxalate (3), and a cyclic dicarbonyl compound.

（式中、Ｒ^１１及びＲ^１２は、同一又は異なってもよく、炭素数１〜７のアルキル基、Ｒｆ^１３は炭素数１〜７のフッ素化アルキル基）で示される。 The amine (1) has the general formula (1):

^{(Wherein, R 11} and ^{R 12} may be the same or different, an alkyl group having 1 to 7 carbon atoms, ^{Rf 13} represents an alkyl group fluorinated 1-7 carbon atoms) represented by.

R ¹¹ and R ¹² are preferably an alkyl group having 1 to 4 carbon atoms and more preferably an alkyl group having 1 to 3 carbon atoms in terms of low molecular weight and low viscosity.

R ¹¹ is preferably —CH ₂ —CH ₃ , —CH ₃ , —CH ₂ CH ₂ CH ₃ , or —CH (CH ₃ ) _{2 in} terms of low molecular weight and low viscosity.
R ¹² is preferably —CH ₂ —CH ₃ , —CH ₃ , —CH ₂ CH ₂ CH ₃ , or —CH (CH ₃ ) _{2 in} terms of low molecular weight and low viscosity.

Rf ¹³ is preferably a fluorinated alkyl group having 2 to 5 carbon atoms, and more preferably a fluorinated alkyl group having 2 to 4 carbon atoms in terms of maintaining compatibility.
In the present specification, the “fluorinated alkyl group” is a group in which at least one hydrogen atom of an alkyl group is substituted with a fluorine atom.
Rf ¹³ is preferably CF ₃ CH ₂ —, CF ₃ CF ₂ CH ₂ —, or CF ₂ HCF ₂ CH ₂ —.

The amine (1) preferably has a fluorine content of 15 to 65% by mass. When the fluorine content is in the above range, the compatibility with the solvent and the solubility of the salt can be maintained. The fluorine content is more preferably 20% by mass or more, further preferably 30% by mass or more, more preferably 50% by mass or less, and still more preferably 40% by mass or less.
In the present invention, the fluorine content is based on the structural formula of amine (1).
{(Number of fluorine atoms × 19) / molecular weight of amine (1)} × 100 (%)
The value calculated by

The amine (1) is preferably one of the following compounds in that it is a low viscosity compound.

（式中、Ｒ^２１及びＲ^２２は、同一又は異なってもよく、炭素数１〜７のアルキル基、Ｒ^２３は炭素数１〜７のアルキル基又は炭素数１〜７のフッ素化アルキル基）
で示される。 The amide (2) has the general formula (2):

(In the formula, R ²¹ and R ²² may be the same or different, and an alkyl group having 1 to 7 carbon atoms, R ²³ is an alkyl group having 1 to 7 carbon atoms or a fluorinated alkyl group having 1 to 7 carbon atoms).
Indicated by

R ²¹ and R ²² are preferably an alkyl group having 2 to 5 carbon atoms, and more preferably an alkyl group having 2 to 4 carbon atoms.
R ²³ is preferably an alkyl group having 2 to 5 carbon atoms or a fluorinated alkyl group having 2 to 5 carbon atoms, more preferably an alkyl group having 2 to 4 carbon atoms or a fluorinated alkyl group having 2 to 4 carbon atoms.

R ²¹ is preferably —CH ₃ , —CH ₂ CH ₃ , —CH ₂ CH ₂ CH ₃ , or —CH (CH ₃ ) ₂ , and R ²² is preferably —CH ₃ , —CH ₂ CH ₃ , —CH ₂ CH ₂ CH ₃ or —CH (CH ₃ ) ₂ is preferable, and R ²³ is —CH ₃ , —CH ₂ CH ₃ , —CH ₂ CH ₂ CH ₃ , —CH (CH ₃ ) _2. or, _-CH 2 CF ₃ are preferred.

The amide (2) is preferably one of the following compounds from the viewpoint of maintaining compatibility.

（式中、Ｒ^３１及びＲ^３２は、同一又は異なっていてもよく、炭素数１〜７のアルキル基）で示される。 The dialkyl oxalate (3) has the general formula (3):

(In the formula, R ³¹ and R ³² may be the same or different and each represents an alkyl group having 1 to 7 carbon atoms).

As R ³¹ and ^{R 32,} in that the molecular weight is small, preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

R ³¹ is preferably CH ₃ —, CH ₃ CH ₂ —, CH ₃ CH ₂ CH ₂ —, or (CH ₃ ) ₂ CH— from the viewpoint of low molecular weight and low viscosity. R ³² is preferably CH ₃ —, CH ₃ CH ₂ —, CH ₃ CH ₂ CH ₂ —, or (CH ₃ ) ₂ CH— from the viewpoint of low molecular weight and low viscosity.

The dialkyl oxalate (3) is preferably any of the following compounds from the viewpoint of low molecular weight and low viscosity.

The electrolytic solution includes at least one compound (α) selected from the group consisting of amine (1) and amide (2), and the content of the compound (α) is 0.001 to 20 ppm in the electrolytic solution. It is preferable that When the content is within the above-described range, the electrochemical device using the electrolytic solution of the present invention is further excellent in storage characteristics at high temperatures, and resistance is less likely to increase even after storage at high temperatures. The content of the compound (α) is more preferably 0.01 ppm or more, more preferably 0.05 ppm or more, more preferably 10 ppm in the electrolytic solution in that the high-temperature storage characteristics are further improved and the resistance is less likely to increase even after high-temperature storage. The following is more preferable, 5 ppm or less is further preferable, and 1 ppm or less is particularly preferable. The content of the compound (α) can be measured by a GC-MS analysis method.

When the amine (1) and the amide (2) are used in combination as the compound (α), the content of the compound (α) is preferably the respective content of the amine (1) and the amide (2). .
Further, when the amine (1) and the amide (2) are used in combination as the compound (α), the content of the amine (1) is preferably 0.01 to 10 ppm, and the content of the amide (2) is 0. 0.001 to 10 ppm is preferred.
The content of amine (1) is more preferably 1 ppm or more, and more preferably 5 ppm or less.
The content of amide (2) is more preferably 5 ppm or less.

The electrolytic solution contains a dialkyl oxalate (3), and the content of the dialkyl oxalate (3) is preferably 0.001 to 10 ppm in the electrolytic solution. When the content is within the above-described range, the electrochemical device using the electrolytic solution of the present invention is further excellent in storage characteristics at high temperatures, and resistance is less likely to increase even after storage at high temperatures. The content of the dialkyl oxalate (3) is more preferably 0.01 ppm or more, more preferably 0.05 ppm or more in the electrolytic solution in that the high-temperature storage characteristics are further improved and the resistance is less likely to increase even after high-temperature storage. 5 ppm or less is more preferable, and 1 ppm or less is still more preferable. Content of dialkyl oxalate (3) can be measured by the method of GC-MS analysis.

The electrolytic solution further contains 0.001 to 10% by mass of a cyclic dicarbonyl compound with respect to the electrolytic solution. The content of the cyclic dicarbonyl compound is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, preferably 3% by mass or less, and more preferably 2% by mass or less. The content of the cyclic carbonyl compound can be measured by a GC-MS analysis method.

The cyclic dicarbonyl compound is at least one selected from the group consisting of compound (4) and compound (5).

（Ａ^ａ＋は金属イオン、水素イオン又はオニウムイオン。ａは１〜３の整数、ｂは１〜３の整数、ｐはｂ／ａ、ｎ^４３は１〜４の整数、ｎ^４１は０〜８の整数、ｎ^４２は０又は１、Ｚ^４１は遷移金属、周期律表のＩＩＩ族、ＩＶ族又はＶ族の元素。
Ｘ^４１は、Ｏ、Ｓ、炭素数１〜１０のアルキレン基、炭素数１〜１０のハロゲン化アルキレン基、炭素数６〜２０のアリーレン基又は炭素数６〜２０のハロゲン化アリーレン基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよく、またｎ^４２が１でｎ^４３が２〜４のときにはｎ^４３個のＸ^４１はそれぞれが結合していてもよい）
Ｌ^４１は、ハロゲン原子、シアノ基、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基、炭素数６〜２０のハロゲン化アリール基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよく、またｎ^４１が２〜８のときにはｎ^４１個のＬ^４１はそれぞれが結合して環を形成してもよい）又は−Ｚ^４３Ｙ^４３。
Ｙ^４１、Ｙ^４２及びＺ^４３は、それぞれ独立でＯ、Ｓ、ＮＹ^４４、炭化水素基又はフッ素化炭化水素基。Ｙ^４３及びＹ^４４は、それぞれ独立でＨ、Ｆ、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基又は炭素数６〜２０のハロゲン化アリール基（アルキル基、ハロゲン化アルキル基、アリール基及びハロゲン化アリール基はその構造中に置換基、ヘテロ原子を持っていてもよく、Ｙ^４３又はＹ^４４が複数個存在する場合にはそれぞれが結合して環を形成してもよい））
で示される。 Compound (4) has the general formula (4):

(A ^{a +} is a metal ion, hydrogen ion or onium ion. A is an integer of 1 to 3, b is an integer of 1 to 3, p is b / a, n ⁴³ is an integer of 1 to 4, n ⁴¹ is 0 to 8 , N ⁴² is 0 or 1, Z ⁴¹ is a transition metal, a group III, IV or V element of the periodic table.
X ⁴¹ is O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (alkylene group). , a halogenated alkylene group, an arylene group, and halogenated arylene group substituent in its structure, may have a hetero atom, and n ⁴² is ⁴³ pieces of n when n ⁴³ at 1 is 2 to 4 X ⁴¹ may be bonded to each other)
L ⁴¹ is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms ( The alkylene group, halogenated alkylene group, arylene group, and halogenated arylene group may have a substituent or a hetero atom in the structure. When n ⁴¹ is 2 to 8, n ⁴¹ L ⁴¹ is each may be combined with each other to form a ring) or ^-Z 43 ^{Y 43.}
Y ⁴¹ , Y ⁴² and Z ⁴³ are each independently O, S, NY ⁴⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ⁴³ and Y ⁴⁴ are each independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogen having 6 to 20 carbon atoms. Aryl group (an alkyl group, a halogenated alkyl group, an aryl group and a halogenated aryl group may have a substituent or a hetero atom in the structure thereof, and when there are a plurality of Y ⁴³ or Y ^44, May combine to form a ring)))
Indicated by

A ^{a +} includes lithium ion, sodium ion, potassium ion, magnesium ion, calcium ion, barium ion, cesium ion, silver ion, zinc ion, copper ion, cobalt ion, iron ion, nickel ion, manganese ion, titanium ion, Lead ion, chromium ion, vanadium ion, ruthenium ion, yttrium ion, lanthanoid ion, actinoid ion, tetrabutylammonium ion, tetraethylammonium ion, tetramethylammonium ion, triethylmethylammonium ion, triethylammonium ion, pyridinium ion, imidazolium ion , Hydrogen ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium Ions, triphenylsulfonium ions, triethylsulfonium ions, and the like.

When used for applications such as electrochemical devices, A ^{a +} is preferably a lithium ion, sodium ion, magnesium ion, tetraalkylammonium ion, or hydrogen ion, and particularly preferably a lithium ion. The valence ^a of the cation of A ^{a +} is an integer of 1 to 3. If it is larger than 3, the crystal lattice energy becomes large, which causes a problem that it becomes difficult to dissolve in a solvent. Therefore, when solubility is required, 1 is more preferable. Similarly, the valence b of the anion is an integer of 1 to 3, and 1 is particularly preferable. The constant p representing the ratio of cation to anion is inevitably determined by the valence ratio b / a of both.

Next, the ligand part of the general formula (4) will be described. In this specification, the organic or inorganic part couple ^| bonded with ^Z41 in General formula (4) is called a ligand.

Z ⁴¹ is preferably Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf or Sb. More preferably, B or P.

X ⁴¹ represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms. These alkylene groups and arylene groups may have a substituent or a hetero atom in the structure. Specifically, in place of hydrogen on the alkylene group and arylene group, a halogen atom, a chain or cyclic alkyl group, an aryl group, an alkenyl group, an alkoxy group, an aryloxy group, a sulfonyl group, an amino group, a cyano group, a carbonyl group It may have a group, an acyl group, an amide group, or a hydroxyl group as a substituent, or may have a structure in which nitrogen, sulfur, or oxygen is introduced instead of carbon on alkylene and arylene. Also, when ^{n 42} is ^{n 43} at 1 is 2 to ^{4, n 43} amino ^{X 41} may be bonded, respectively. Examples thereof include a ligand such as ethylenediaminetetraacetic acid.

L ⁴¹ is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms, or -Z ⁴³ Y ⁴³ (Z ⁴³ and Y ⁴³ will be described later). The alkyl group and aryl group here may also have a substituent or a hetero atom in the structure in the same manner as X ^41, and when n ⁴¹ is 2 to 8, each of n ⁴¹ L ⁴¹ is It may combine to form a ring. L ⁴¹ is preferably a fluorine atom or a cyano group. This is because in the case of a fluorine atom, the solubility and dissociation degree of the salt of the anion compound are improved, and the ionic conductivity is improved accordingly. Moreover, it is because oxidation resistance improves and generation | occurrence | production of a side reaction can be suppressed by this.

Y ⁴¹ , Y ⁴² and Z ⁴³ each independently represent O, S, NY ⁴⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ⁴¹ and Y ⁴² are preferably O, S or NY ⁴⁴ , and more preferably O. As a feature of the compound (4), since Y ⁴¹ and Y ⁴² bind to Z ⁴¹ in the same ligand, these ligands constitute a chelate structure with Z ⁴¹ . Due to the effect of this chelate, the heat resistance, chemical stability, and hydrolysis resistance of this compound are improved. The constant n ^{42 in} this ligand is 0 or 1. Particularly, 0 is preferable because this chelate ring becomes a five-membered ring, so that the chelate effect is exhibited most strongly and the stability is increased.
In the present specification, the fluorinated hydrocarbon group is a group in which at least one hydrogen atom of the hydrocarbon group is substituted with a fluorine atom.

Y ⁴³ and Y ⁴⁴ are each independently H, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated group having 6 to 20 carbon atoms. An aryl group, and these alkyl group and aryl group may have a substituent or a hetero atom in the structure, and when a plurality of Y ⁴³ or Y ⁴⁴ are present, A ring may be formed.

In addition, the constant n ⁴³ related to the number of ligands described above is an integer of 1 to 4, preferably 1 or 2, and more preferably 2. The constant n ⁴¹ related to the number of ligands described above is an integer of 0 to 8, preferably an integer of 0 to 4, more preferably 0, 2 or 4. Further, when n ⁴³ is 1, n ⁴¹ is preferably 2, and when n ⁴³ is 2, n ⁴¹ is preferably 0.

In the general formula (4), the alkyl group, the halogenated alkyl group, the aryl group, and the halogenated aryl group include those having other functional groups such as a branch, a hydroxyl group, and an ether bond.

（式中、Ａ^ａ＋、ａ、ｂ、ｐ、ｎ^４１、Ｚ^４１及びＬ^４１は上述したとおり）で示される化合物、又は、一般式：

（式中、Ａ^ａ＋、ａ、ｂ、ｐ、ｎ^４１、Ｚ^４１及びＬ^４１は上述したとおり）で示される化合物であることが好ましい。 As the compound (4), the general formula:

(Wherein A ^{a +} , a, b, p, n ⁴¹ , Z ⁴¹ and L ⁴¹ are as described above) or a general formula:

(Wherein, A ^{a +} , a, b, p, n ⁴¹ , Z ⁴¹ and L ⁴¹ are as described above) is preferable.

で示されるリチウムビス（オキサラト）ボレート、下記式：

で示されるリチウムジフルオロオキサラトボレート、下記式：

で示されるリチウムジシアノオキサラトボレート等が挙げられる。 Examples of the compound (4) include lithium oxalatoborate salts, which have the following formula:

Lithium bis (oxalato) borate represented by the following formula:

Lithium difluorooxalatoborate represented by the following formula:

And lithium dicyanooxalatoborate represented by the formula.

で示されるリチウムテトラフルオロオキサラトホスファナイト、下記式：

で示されるリチウムビス（オキサラト）ジフルオロホスファナイト等が挙げられる。 As the compound (4), the following formula:

Lithium tetrafluorooxalatophosphanite represented by the following formula:

And lithium bis (oxalato) difluorophosphanite represented by

（式中、ｎ^５１は０又は１、ｎ^５２は０又は１、Ｚ^５１は遷移金属、周期律表のＩＩＩ族、ＩＶ族又はＶ族の元素。
Ｘ^５１は、Ｏ、Ｓ、炭素数１〜１０のアルキレン基、炭素数１〜１０のハロゲン化アルキレン基、炭素数６〜２０のアリーレン基又は炭素数６〜２０のハロゲン化アリーレン基（アルキレン基、ハロゲン化アルキレン基、アリーレン基、及び、ハロゲン化アリーレン基はその構造中に置換基、ヘテロ原子を持っていてもよい）。
Ｙ^５１及びＹ^５２は、それぞれ独立でＯ、Ｓ、ＮＹ^５４、炭化水素基又はフッ素化炭化水素基。Ｙ^５４はＨ、炭素数１〜１０のアルキル基、炭素数１〜１０のハロゲン化アルキル基、炭素数６〜２０のアリール基、炭素数６〜２０のハロゲン化アリール基（アルキル基、ハロゲン化アルキル基、アリール基及びハロゲン化アリール基はその構造中に置換基、ヘテロ原子を持っていてもよく、Ｙ^５４が複数個存在する場合にはそれぞれが結合して環を形成してもよい））で示される。 Compound (5) has the general formula (5):

(In the formula, n ⁵¹ is 0 or 1, n ⁵² is 0 or 1, Z ⁵¹ is a transition metal, a group III, group IV or group V element of the periodic table.
X ⁵¹ represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (alkylene group). , A halogenated alkylene group, an arylene group, and a halogenated arylene group may have a substituent or a hetero atom in the structure thereof.
Y ⁵¹ and Y ⁵² are each independently O, S, NY ⁵⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ⁵⁴ is H, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms (an alkyl group, a halogenated group). The alkyl group, aryl group and halogenated aryl group may have a substituent or a hetero atom in the structure thereof, and when there are a plurality of Y ^{54 s} , they may be bonded to form a ring) ).

Z ⁵¹ may be Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf, Sb, or the like. However, n ⁵¹ is preferably 0.
n ⁵² is preferably 1. X ⁵¹ is preferably O or S, and more preferably O.
Y ⁵¹ and Y ⁵² are each independently a hydrocarbon group or a fluorinated hydrocarbon group, preferably a hydrocarbon group having 1 to 3 carbon atoms or a fluorinated hydrocarbon group having 1 to 3 carbon atoms. More preferably. It is preferable that n ⁵¹ is 0 and Y ⁵¹ and Y ⁵² are bonded to each other to form a ring.

（式中、Ｒ^５１〜Ｒ^５４は、同じか又は異なり、Ｈ、Ｆ、アルキル基又はフッ素化アルキル基）で示される化合物、又は、一般式：

（式中、Ｒ^５５及びＲ^５６は、同じか又は異なり、Ｈ、Ｆ、アルキル基又はフッ素化アルキル基、Ｒ^５７はアルケン基又はフッ素化アルケン基）
であることが好ましい。 Compound (5) has the general formula:

(Wherein R ^{51 to} R ⁵⁴ are the same or different and H, F, an alkyl group or a fluorinated alkyl group), or a general formula:

(Wherein R ⁵⁵ and R ⁵⁶ are the same or different, H, F, an alkyl group or a fluorinated alkyl group, and R ⁵⁷ is an alkene group or a fluorinated alkene group)
It is preferable that

The carbon number of the alkyl group, fluorinated alkyl group, alkene group, and fluorinated alkene group is preferably 1 to 10, and more preferably 1 to 3 in terms of good compatibility with the electrolytic solution.

Examples of R ^{51 to} R ⁵⁶ include H-, F-, CH _3- , CH ₃ CH _2- , CH ₃ CH ₂ CH _2- , CF _3- , CF ₃ CF _2- , CH ₂ FCH _2- , CF ₃ CF ₂ CF ₂ — and the like can be mentioned.

Examples of R ⁵⁷ include CH ₂ =, CH ₃ CH ₂ =, and the like.

（式中、Ｒ^５８及びＲ^５９は、同じか又は異なり、Ｈ、Ｆ、アルキル基又はフッ素化アルキル基）で示される化合物であることが好ましい。 Compound (5) has the general formula:

In the formula, R ⁵⁸ and R ⁵⁹ are the same or different and are preferably compounds represented by H, F, an alkyl group, or a fluorinated alkyl group.

It is preferable that carbon number of an alkyl group and a fluorinated alkyl group is 1-10, and 1-3 are more preferable at the point with compatibility with electrolyte solution being favorable.

Examples of R ⁵⁸ and R ⁵⁹ include H-, F-, CH _3- , CH ₃ CH _2- , CH ₃ CH ₂ CH _2- , CF _3- , CF ₃ CF _2- , CH ₂ FCH _2- , CF ₃ CF ₂ CF ₂ — and the like can be mentioned.

As the compound (5), succinic anhydride, glutaric anhydride, itaconic anhydride, diglycolic anhydride, cyclohexane carboxylic anhydride, cyclopentane tetracarboxylic anhydride, phenyl succinic anhydride, dimethyl succinic anhydride, Examples thereof include trifluoromethyl succinic anhydride, monofluoro succinic anhydride, tetrafluoro succinic anhydride, maleic anhydride, citraconic anhydride, trifluoromethyl maleic anhydride, and the like.
Of these, maleic anhydride and trifluoromethylmaleic anhydride are preferable.

The electrolytic solution of the present invention preferably contains a solvent.
The content of the solvent is preferably 70 to 95% by mass, more preferably 80% by mass or more, and more preferably 90% by mass or less based on the electrolytic solution.
The content of the solvent may be an amount that is 100% by mass when the total content of the cyclic dicarbonyl compound, amine (1), amide (2), and dialkyl oxalate (3) is added.

The solvent preferably contains carbonate.
The solvent preferably contains a cyclic carbonate and a chain carbonate.
The cyclic carbonate may be a non-fluorinated cyclic carbonate or a fluorinated cyclic carbonate.
The chain carbonate may be a non-fluorinated chain carbonate or a fluorinated chain carbonate.
The solvent preferably contains at least one selected from the group consisting of a non-fluorinated saturated cyclic carbonate, a fluorinated saturated cyclic carbonate, a fluorinated chain carbonate, and a non-fluorinated chain carbonate. Especially, it is more preferable that at least 1 sort (s) selected from the group which consists of a fluorinated saturated cyclic carbonate and a fluorinated chain carbonate is included.
The solvent is preferably a non-aqueous solvent, and the electrolytic solution of the present invention is preferably a non-aqueous electrolytic solution.

Examples of the non-fluorinated saturated cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.

Among them, the non-fluorinated saturated cyclic carbonate is at least one compound selected from the group consisting of ethylene carbonate, propylene carbonate, and butylene carbonate in that the dielectric constant is high and the viscosity is suitable. It is preferable.
As said non-fluorinated saturated cyclic carbonate, 1 type of the compound mentioned above may be used, and 2 or more types may be used together.

The content of the non-fluorinated saturated cyclic carbonate is preferably 0 to 99% by volume, more preferably 1% by volume or more, and more preferably 90% by volume or less with respect to the solvent.

The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate to which a fluorine atom is added. Specifically, the following general formula (A):

（式中、Ｘ^１〜Ｘ^４は同じか又は異なり、それぞれ−Ｈ、−ＣＨ_３、−Ｆ、エーテル結合を有してもよいフッ素化アルキル基、又は、エーテル結合を有してもよいフッ素化アルコキシ基を表す。ただし、Ｘ^１〜Ｘ^４の少なくとも１つは、−Ｆ、エーテル結合を有してもよいフッ素化アルキル基、又は、エーテル結合を有してもよいフッ素化アルコキシ基である。）で示される化合物が挙げられる。
上記フッ素化飽和環状カーボネートを含むと、本発明の電解液をリチウムイオン二次電池等に適用した場合に、負極に安定な被膜を形成することができ、負極での電解液の副反応を充分に抑制することができる。その結果、極めて安定で優れた充放電特性が得られる。
なお、本明細書中で「エーテル結合」は、−Ｏ−で表される結合である。

(In the formula, X ^{1 to} X ⁴ are the same or different and are each —H, —CH ₃ , —F, a fluorinated alkyl group that may have an ether bond, or a fluorine that may have an ether bond. Wherein at least one of X ^{1 to} X ⁴ is —F, a fluorinated alkyl group that may have an ether bond, or a fluorinated alkoxy group that may have an ether bond. And a compound represented by
When the fluorinated saturated cyclic carbonate is contained, when the electrolytic solution of the present invention is applied to a lithium ion secondary battery or the like, a stable film can be formed on the negative electrode, and the side reaction of the electrolytic solution at the negative electrode is sufficient. Can be suppressed. As a result, extremely stable and excellent charge / discharge characteristics can be obtained.
In the present specification, the “ether bond” is a bond represented by —O—.

From the viewpoint of good dielectric constant and oxidation resistance, one or two of X ^{1 to} X ⁴ may have —F, a fluorinated alkyl group that may have an ether bond, or an ether bond. A fluorinated alkoxy group is preferred.

Since it can be expected to lower the viscosity at low temperature, increase the flash point, and further improve the solubility of the electrolyte salt, X ^{1 to} X ⁴ represent -H, -F, a fluorinated alkyl group (a), an ether bond. The fluorinated alkyl group (b) or the fluorinated alkoxy group (c) is preferable.

The fluorinated alkyl group (a) is obtained by substituting at least one hydrogen atom of the alkyl group with a fluorine atom. 1-20 are preferable, as for carbon number of a fluorinated alkyl group (a), 2-17 are more preferable, 2-7 are still more preferable, and 2-5 are especially preferable.
If the carbon number is too large, the low-temperature characteristics may be lowered or the solubility of the electrolyte salt may be lowered. If the carbon number is too small, the solubility of the electrolyte salt is lowered, the discharge efficiency is lowered, and further, An increase in viscosity may be observed.

Among the fluorinated alkyl groups (a), those having 1 carbon include CFH ₂ —, CF ₂ H—, and CF ₃ —.

Among the fluorinated alkyl groups (a), those having 2 or more carbon atoms include the following general formula (a-1):
R ¹ -R ^2- (a-1)
(Wherein R ¹ is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R ² is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; provided that R ¹ and A fluorinated alkyl group represented by (at least one of R ² has a fluorine atom) can be preferably exemplified from the viewpoint of good solubility of the electrolyte salt.
R ¹ and R ² may further have other atoms other than the carbon atom, the hydrogen atom, and the fluorine atom.

R ¹ is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. R ¹ is preferably a linear or branched alkyl group having ^{1 to} 16 carbon atoms. The number of carbon atoms of R ^1, more preferably 1 to 6, 1 to 3 is more preferable.

As R ¹ , specifically, as a linear or branched alkyl group, CH ₃ —, CH ₃ CH ₂ —, CH ₃ CH ₂ CH ₂ —, CH ₃ CH ₂ CH ₂ CH ₂ —,

Etc.

When R ¹ is a linear alkyl group having a fluorine atom, CF ₃ —, CF ₃ CH ₂ —, CF ₃ CF ₂ —, CF ₃ CH ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ — CF ₃ CF ₂ CF _2- , CF ₃ CH ₂ CF _2- , CF ₃ CH ₂ CH ₂ CH _2- , CF ₃ CF ₂ CH ₂ CH _2- , CF ₃ CH ₂ CF ₂ CH _2- , CF ₃ CF ₂ CF ₂ CH ₂ —, CF ₃ CF ₂ CF ₂ CF ₂ —, CF ₃ CF ₂ CH ₂ CF ₂ —, CF ₃ CH ₂ CH ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ — _{, CF 3 CH 2 CF 2 CH} 2 CH 2 -, CF 3 CF 2 CF 2 CH 2 CH 2 -, CF 3 CF 2 CF 2 CF 2 CH 2 -, CF 3 CF 2 CH 2 CF 2 CH 2 -, CF ₃ C F ₂ CH ₂ CH ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH ₂ —, HCF ₂ —, HCF ₂ CH ₂ —, _{HCF 2 CF 2 -, HCF 2} CH 2 CH 2 -, HCF 2 CF 2 CH 2 -, HCF 2 CH 2 CF 2 -, HCF 2 CF 2 CH 2 CH 2 -, HCF 2 CH 2 CF 2 CH 2 -, HCF ₂ CF ₂ CF ₂ CF _2- , HCF ₂ CF ₂ CH ₂ CH ₂ CH _2- , HCF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH _2- , HCF ₂ CF _{2 CF 2 CF 2 CH 2 CH 2} -, FCH 2 -, FCH 2 CH 2 -, FCH 2 CF 2 -, FCH 2 CF 2 CH 2 -, FCH 2 CF 2 CF 2 - _{CH 3 CF 2 CH 2 -,} CH 3 CF 2 CF 2 -, CH 3 CF 2 CH 2 CF 2 -, CH 3 CF 2 CF 2 CF 2 -, CH 3 CH 2 CF 2 CF 2 -, CH 3 CF 2 CH ₂ CF ₂ CH _2- , CH ₃ CF ₂ CF ₂ CF ₂ CH _2- , CH ₃ CF ₂ CF ₂ CH ₂ CH _2- , CH ₃ CH ₂ CF ₂ CF ₂ CH _2- , CH ₃ CF ₂ CH _{2 CF 2 CH 2 CH 2 -,} CH 3 CF 2 CH 2 CF 2 CH 2 CH 2 -, HCFClCF 2 CH 2 -, HCF 2 CFClCH 2 -, HCF 2 CFClCF 2 CFClCH 2 -, HCFClCF 2 CFClCF 2 CH 2 - , etc. Is mentioned.

When R ¹ is a branched alkyl group having a fluorine atom,

Etc. are preferable. However, since the viscosity is likely to increase when the branch has CH ₃ — or CF ₃ —, the number is preferably small (one) or zero.

R ² is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. R ² may be linear or branched. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below. R ² is composed of these alone or in combination.

(I) Linear minimum structural unit:
_{-CH 2 -, - CHF -,} - CF 2 -, - CHCl -, - CFCl -, - CCl 2 -

(Ii) Branched minimum structural unit:

In addition, among the above examples, it is preferable that the base is composed of a constitutional unit that does not contain Cl, because de-HCl reaction with a base does not occur and is more stable.

When R ² is linear, it is composed of only the above-mentioned linear minimum structural unit, and —CH ₂ —, —CH ₂ CH ₂ — or —CF ₂ — is particularly preferable. From the viewpoint that the solubility of the electrolyte salt can be further improved, —CH ₂ — or —CH ₂ CH ₂ — is more preferable.

When R ² is branched, it comprises at least one of the above-described branched minimum structural units, and R ² is represented by the general formula — (CX ^a X ^b ) — (X ^a is H, F CH ₃ or CF ₃ ; X ^b is CH ₃ or CF _3, provided that when X ^b is CF ₃ , X ^a is H or CH ₃ . In particular, the solubility of the electrolyte salt can be further improved.

Preferred examples of the fluorinated alkyl group (a) include CF ₃ CF ₂ —, HCF ₂ CF ₂ —, H ₂ CFCF ₂ —, CH ₃ CF ₂ —, CF ₃ CF ₂ CF ₂ —, and HCF ₂ CF ₂ CF _{2. -, H 2 CFCF 2 CF 2} -, CH 3 CF 2 CF 2 -,

Etc.

The fluorinated alkyl group (b) having an ether bond is obtained by substituting at least one hydrogen atom of the alkyl group having an ether bond with a fluorine atom. The fluorinated alkyl group (b) having an ether bond preferably has 2 to 17 carbon atoms. If the number of carbon atoms is too large, the viscosity of the fluorinated saturated cyclic carbonate increases, and the fluorine-containing group increases, so that the solubility of the electrolyte salt decreases due to a decrease in the dielectric constant, and compatibility with other solvents. Decrease may be observed. In this respect, the fluorinated alkyl group (b) having an ether bond preferably has 2 to 10 carbon atoms, and more preferably 2 to 7 carbon atoms.

The alkylene group constituting the ether portion of the fluorinated alkyl group (b) having an ether bond may be a linear or branched alkylene group. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below.

(I) Linear minimum structural unit:
_{-CH 2 -, - CHF -,} - CF 2 -, - CHCl -, - CFCl -, - CCl 2 -

(Ii) Branched minimum structural unit:

The alkylene group may be composed of these minimum structural units alone, and may be linear (i), branched (ii), or linear (i) and branched (ii). You may comprise by the combination. Preferred specific examples will be described later.

In addition, among the above examples, it is preferable that the base is composed of a constitutional unit that does not contain Cl, because de-HCl reaction with a base does not occur and is more stable.

As the fluorinated alkyl group (b) having a more preferable ether bond, the general formula (b-1):
R ^3- (OR ⁴ ) _n1- (b-1)
(In the formula, R ³ may have a fluorine atom, preferably an alkyl group having 1 to 6 carbon atoms; R ⁴ may have a fluorine atom, preferably alkylene having 1 to 4 carbon atoms. N1 is an integer of 1 to 3; provided that at least one of R ³ and R ⁴ has a fluorine atom).

Examples of R ³ and R ⁴ include the following, and these can be combined as appropriate to form a fluorinated alkyl group (b) having an ether bond represented by the general formula (b-1). However, it is not limited to these.

(1) As R ³ , the general formula: X ^c ₃ C— (R ⁵ ) _n2 — (three X ^c are the same or different, and each is H or F; R ⁵ represents a fluorine atom having 1 to ⁵ carbon atoms. An alkylene group which may have; n2 is preferably an alkyl group represented by 0 or 1).

When n2 is 0, R ³ includes CH ₃ —, CF ₃ —, HCF ₂ —, and H ₂ CF—.

Specific examples when n2 is 1 include those in which R ³ is linear, CF ₃ CH _2- , CF ₃ CF _2- , CF ₃ CH ₂ CH _2- , CF ₃ CF ₂ CH _2- , CF ₃ CF ₂ CF ₂ —, CF ₃ CH ₂ CF ₂ —, CF ₃ CH ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CH ₂ —, CF ₃ CH ₂ CF ₂ CH ₂ —, CF ₃ CF ₂ CF _{2 CH 2 -, CF 3 CF} 2 CF 2 CF 2 -, CF 3 CF 2 CH 2 CF 2 -, CF 3 CH 2 CH 2 CH 2 CH 2 -, CF 3 CF 2 CH 2 CH 2 CH 2 -, CF ₃ CH ₂ CF ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CF ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ —, CF ₃ CF ₂ CH _{2 H 2 CH 2 CH 2 -,} CF 3 CF 2 CF 2 CF 2 CH 2 CH 2 -, CF 3 CF 2 CH 2 CF 2 CH 2 CH 2 -, HCF 2 CH 2 -, HCF 2 CF 2 -, HCF 2 _{CH 2 CH 2 -, HCF 2} CF 2 CH 2 -, HCF 2 CH 2 CF 2 -, HCF 2 CF 2 CH 2 CH 2 -, HCF 2 CH 2 CF 2 CH 2 -, HCF 2 CF 2 CF 2 CF 2 _{-, HCF 2 CF 2 CH 2} CH 2 CH 2 -, HCF 2 CH 2 CF 2 CH 2 CH 2 -, HCF 2 CF 2 CF 2 CF 2 CH 2 -, HCF 2 CF 2 CF 2 CF 2 CH 2 CH 2 _{-, FCH 2 CH 2 -,} FCH 2 CF 2 -, FCH 2 CF 2 CH 2 -, CH 3 CF 2 -, CH 3 CH 2 -, CH 3 CF 2 CH 2 -, C _{3 CF 2 CF 2 -, CH} 3 CH 2 CH 2 -, CH 3 CF 2 CH 2 CF 2 -, CH 3 CF 2 CF 2 CF 2 -, CH 3 CH 2 CF 2 CF 2 -, CH 3 CH 2 CH _{2 CH 2 -, CH 3 CF} 2 CH 2 CF 2 CH 2 -, CH 3 CF 2 CF 2 CF 2 CH 2 -, CH 3 CF 2 CF 2 CH 2 CH 2 -, CH 3 CH 2 CF 2 CF 2 CH _{2 -, CH 3 CF 2 CH} 2 CF 2 CH 2 CH 2 -, CH 3 CH 2 CF 2 CF 2 CH 2 CH 2 -, CH 3 CF 2 CH 2 CF 2 CH 2 CH 2 - and the like.

n2 is 1, and as R ³ is branched, the

Etc.

However, since the viscosity tends to increase when the branch has CH ₃ — or CF ₃ —, it is more preferable that R ³ is linear.

(2) In — (OR ⁴ ) _n1 — in the general formula (b-1), n1 is an integer of 1 to 3, and preferably 1 or 2. When n1 = 2 or 3, R ⁴ may be the same or different.

Preferable specific examples of R ⁴ include the following linear or branched ones.

As those _{linear, -CH 2 -, - CHF -} , - CF 2 -, - CH 2 CH 2 -, - CF 2 CH 2 -, - CF 2 CF 2 -, - CH 2 CF 2 -, _{-CH 2 CH 2 CH 2 -,} - CH 2 CH 2 CF 2 -, - CH 2 CF 2 CH 2 -, - CH 2 CF 2 CF 2 -, - CF 2 CH 2 CH 2 -, - CF 2 CF 2 CH ₂ —, —CF ₂ CH ₂ CF ₂ —, —CF ₂ CF ₂ CF ₂ — and the like can be exemplified.

As a branched chain,

Etc.

The fluorinated alkoxy group (c) is obtained by substituting at least one hydrogen atom of the alkoxy group with a fluorine atom. The fluorinated alkoxy group (c) preferably has 1 to 17 carbon atoms. More preferably, it is C1-C6.

As the fluorinated alkoxy group (c), the general ^{_{formula: X d 3 C- (R 6}} ) n3 -O- (3 single ^{X d} is either the same or different H or F; ^{R 6} is preferably the number of carbon atoms A fluorinated alkoxy group represented by an alkylene group optionally having 1 to 5 fluorine atoms; n3 is 0 or 1; but any one of three X ^ds contains a fluorine atom is particularly preferable.

Specific examples of the fluorinated alkoxy group (c) include a fluorinated alkoxy group in which an oxygen atom is bonded to the terminal of the alkyl group exemplified as R ¹ in the general formula (a-1).

The fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) in the fluorinated saturated cyclic carbonate is preferably 10% by mass or more. If the fluorine content is too low, the effect of lowering the viscosity at low temperatures and the effect of increasing the flash point may not be sufficiently obtained. From this viewpoint, the fluorine content is more preferably 12% by mass or more, and further preferably 15% by mass or more. The upper limit is usually 76% by mass.
The fluorine content of the fluorinated alkyl group (a), the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) is determined based on {(number of fluorine atoms) based on the structural formula of each group. × 19) / Formula amount of each group} × 100 (%).

Further, from the viewpoint of good dielectric constant and oxidation resistance, the fluorine content of the entire fluorinated saturated cyclic carbonate is preferably 10% by mass or more, and more preferably 15% by mass or more. The upper limit is usually 76% by mass.
The fluorine content of the fluorinated saturated cyclic carbonate is {(number of fluorine atoms × 19) / molecular weight of fluorinated saturated cyclic carbonate} × 100 (%) based on the structural formula of the fluorinated saturated cyclic carbonate. It is a calculated value.

Specific examples of the fluorinated saturated cyclic carbonate include the following.

As a specific example of the fluorinated saturated cyclic carbonate in which at least one of X ^{1 to} X ⁴ is —F,

等が挙げられる。これらの化合物は、耐電圧が高く、電解質塩の溶解性も良好である。

Etc. These compounds have a high withstand voltage and good solubility of the electrolyte salt.

other,

Etc. can also be used.

Specific examples of the fluorinated saturated cyclic carbonate in which at least one of X ^{1 to} X ⁴ is a fluorinated alkyl group (a) and the rest are all —H,

Etc.

Specific examples of fluorinated saturated cyclic carbonates in which at least one of X ^{1 to} X ⁴ is a fluorinated alkyl group (b) or a fluorinated alkoxy group (c) having an ether bond, and the rest are all —H as,

Etc.

Among them, the fluorinated saturated cyclic carbonate is preferably any of the following compounds.

Among the above fluorinated saturated cyclic carbonates, fluoroethylene carbonate and difluoroethylene carbonate are more preferable.

The fluorinated saturated cyclic carbonate is not limited to the specific examples described above. Moreover, the said fluorinated saturated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The content of the fluorinated saturated cyclic carbonate is preferably 0 to 99% by volume in the solvent, more preferably 1% by volume or more, further preferably 5% by volume or more, more preferably 95% by volume or less, and 90% by volume. % Or less is more preferable.

As said fluorinated chain carbonate, general formula (B):
Rf ² OCOOR ⁶ (B)
(Wherein Rf ² is a fluorinated alkyl group having 1 to 7 carbon atoms, and R ⁶ is an alkyl group that may contain a fluorine atom having 1 to 7 carbon atoms). Can be mentioned.

The electrolyte solution of the present invention preferably contains the fluorinated chain carbonate in that it can be suitably used even under a high voltage.

Rf ² is a fluorinated alkyl group having 1 to 7 carbon atoms, and R ⁶ is an alkyl group that may contain a fluorine atom having 1 to 7 carbon atoms.
The fluorinated alkyl group is obtained by substituting at least one hydrogen atom of the alkyl group with a fluorine atom. When R ⁶ is an alkyl group containing a fluorine atom, it becomes a fluorinated alkyl group.
Rf ² and R ⁶ are preferably 2 to 7 carbon atoms and more preferably 2 to 4 carbon atoms in terms of low viscosity.
If the carbon number is too large, the low-temperature characteristics may be lowered or the solubility of the electrolyte salt may be lowered. If the carbon number is too small, the solubility of the electrolyte salt is lowered, the discharge efficiency is lowered, and further, An increase in viscosity may be observed.

Examples of the fluorinated alkyl group having 1 carbon atom include CFH ₂ —, CF ₂ H—, and CF ₃ —.

Examples of the fluorinated alkyl group having 2 or more carbon atoms include the following general formula (d-1):
R ¹ -R ^2- (d-1)
(Wherein R ¹ is an alkyl group having 1 or more carbon atoms which may have a fluorine atom; R ² is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom; provided that R ¹ and A fluorinated alkyl group represented by (at least one of R ² has a fluorine atom) can be preferably exemplified from the viewpoint of good solubility of the electrolyte salt.
R ¹ and R ² may further have other atoms other than the carbon atom, the hydrogen atom, and the fluorine atom.

R ¹ is an alkyl group having 1 or more carbon atoms which may have a fluorine atom. R ¹ is preferably a linear or branched alkyl group having 1 to 6 carbon atoms. The number of carbon atoms of R ^1, more preferably 1 to 6, 1 to 3 is more preferable.

As R ¹ , specifically, as a linear or branched alkyl group, CH ₃ —, CH ₃ CH ₂ —, CH ₃ CH ₂ CH ₂ —, CH ₃ CH ₂ CH ₂ CH ₂ —,

Etc.

When R ¹ is a linear alkyl group having a fluorine atom, CF ₃ —, CF ₃ CH ₂ —, CF ₃ CF ₂ —, CF ₃ CH ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ — CF ₃ CF ₂ CF _2- , CF ₃ CH ₂ CF _2- , CF ₃ CH ₂ CH ₂ CH _2- , CF ₃ CF ₂ CH ₂ CH _2- , CF ₃ CH ₂ CF ₂ CH _2- , CF ₃ CF ₂ CF ₂ CH ₂ —, CF ₃ CF ₂ CF ₂ CF ₂ —, CF ₃ CF ₂ CH ₂ CF ₂ —, CF ₃ CH ₂ CH ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CH ₂ CH ₂ — _{, CF 3 CH 2 CF 2 CH} 2 CH 2 -, CF 3 CF 2 CF 2 CH 2 CH 2 -, CF 3 CF 2 CF 2 CF 2 CH 2 -, CF 3 CF 2 CH 2 CF 2 CH 2 -, CF ₃ C F ₂ CH ₂ CH ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CF ₂ CF ₂ CH ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CF ₂ CH ₂ CH ₂ —, HCF ₂ —, HCF ₂ CH ₂ —, _{HCF 2 CF 2 -, HCF 2} CH 2 CH 2 -, HCF 2 CF 2 CH 2 -, HCF 2 CH 2 CF 2 -, HCF 2 CF 2 CH 2 CH 2 -, HCF 2 CH 2 CF 2 CH 2 -, HCF ₂ CF ₂ CF ₂ CF _2- , HCF ₂ CF ₂ CH ₂ CH ₂ CH _2- , HCF ₂ CH ₂ CF ₂ CH ₂ CH _2- , HCF ₂ CF ₂ CF ₂ CF ₂ CH _2- , HCF ₂ CF _{2 CF 2 CF 2 CH 2 CH 2} -, FCH 2 -, FCH 2 CH 2 -, FCH 2 CF 2 -, FCH 2 CF 2 CH 2 -, FCH 2 CF 2 CF 2 - _{CH 3 CF 2 CH 2 -,} CH 3 CF 2 CF 2 -, CH 3 CF 2 CH 2 CF 2 -, CH 3 CF 2 CF 2 CF 2 -, CH 3 CH 2 CF 2 CF 2 -, CH 3 CF 2 CH ₂ CF ₂ CH _2- , CH ₃ CF ₂ CF ₂ CF ₂ CH _2- , CH ₃ CF ₂ CF ₂ CH ₂ CH _2- , CH ₃ CH ₂ CF ₂ CF ₂ CH _2- , CH ₃ CF ₂ CH _{2 CF 2 CH 2 CH 2 -,} CH 3 CF 2 CH 2 CF 2 CH 2 CH 2 -, HCFClCF 2 CH 2 -, HCF 2 CFClCH 2 -, HCF 2 CFClCF 2 CFClCH 2 -, HCFClCF 2 CFClCF 2 CH 2 - , etc. Is mentioned.

When R ¹ is a branched alkyl group having a fluorine atom,

Etc. are preferable. However, since the viscosity is likely to increase when the branch has CH ₃ — or CF ₃ —, the number is preferably small (one) or zero.

R ² is an alkylene group having 1 to 3 carbon atoms which may have a fluorine atom. R ² may be linear or branched. An example of the minimum structural unit constituting such a linear or branched alkylene group is shown below. R ² is composed of these alone or in combination.

(I) Linear minimum structural unit:
_{-CH 2 -, - CHF -,} - CF 2 -, - CHCl -, - CFCl -, - CCl 2 -

(Ii) Branched minimum structural unit:

In addition, among the above examples, it is preferable that the base is composed of a constitutional unit that does not contain Cl, because de-HCl reaction with a base does not occur and is more stable.

When R ² is linear, it is composed of only the above-mentioned linear minimum structural unit, and —CH ₂ —, —CH ₂ CH ₂ — or —CF ₂ — is particularly preferable. From the viewpoint that the solubility of the electrolyte salt can be further improved, —CH ₂ — or —CH ₂ CH ₂ — is more preferable.

When R ² is branched, it comprises at least one of the above-described branched minimum structural units, and R ² is represented by the general formula — (CX ^a X ^b ) — (X ^a is H, F CH ₃ or CF ₃ ; X ^b is CH ₃ or CF _3, provided that when X ^b is CF ₃ , X ^a is H or CH ₃ . In particular, the solubility of the electrolyte salt can be further improved.

Specific examples of preferred fluorinated alkyl groups include CF ₃ CF ₂ —, HCF ₂ CF ₂ —, H ₂ CFCF ₂ —, CH ₃ CF ₂ —, CF ₃ CF ₂ CF ₂ —, and HCF ₂ CF. _{2 CF 2 -, H 2 CFCF} 2 CF 2 -, CH 3 CF 2 CF 2 -,

Etc.

Among them, as the fluorinated alkyl group of Rf ² and _{^{R 6, CF 3 -, CF}} 3 CF 2 -, (CF 3) 2 CH-, CF 3 CH 2 -, C 2 F 5 CH 2 -, HCF 2 CF ₂ CH _2- , CF ₃ CFHCF ₂ CH ₂ -are preferable, and from the viewpoint of high flame retardancy, good rate characteristics and oxidation resistance, CF ₃ CH _2- , CF ₃ CF ₂ CH _2- , HCF ₂ CF ₂ CH ₂ — is more preferable.

When R ⁶ is an alkyl group containing no fluorine atom, it is an alkyl group having 1 to 7 carbon atoms. R ⁶ is preferably 1 to 4 carbon atoms, more preferably 1 to 3 in terms of low viscosity.

Examples of the alkyl group not containing a fluorine atom include CH ₃ —, CH ₃ CH ₂ —, (CH ₃ ) ₂ CH—, C ₃ H ₇ — and the like. Of these, CH ₃ — and CH ₃ CH ₂ — are preferable from the viewpoint of low viscosity and good rate characteristics.

The fluorinated chain carbonate preferably has a fluorine content of 20 to 70% by mass. When the fluorine content is in the above range, the compatibility with the solvent and the solubility of the salt can be maintained. The fluorine content is more preferably 30% by mass or more, further preferably 35% by mass or more, more preferably 60% by mass or less, and still more preferably 50% by mass or less.
In the present invention, the fluorine content is based on the structural formula of the fluorinated chain carbonate,
{(Number of fluorine atoms × 19) / molecular weight of fluorinated chain carbonate} × 100 (%)
The value calculated by

The fluorinated chain carbonate is preferably one of the following compounds from the viewpoint of low viscosity.

The content of the fluorinated chain carbonate is preferably 1 to 90% by volume in the solvent. When the content is within the above range, compatibility can be maintained.
The content of the fluorinated chain carbonate is more preferably 30% by volume or more in the electrolytic solution, more preferably 40% by volume or more, and more preferably 85% by volume or less in that the solubility of the salt can be maintained. 80% by volume or less is more preferable.

Examples of the non-fluorinated chain carbonate include CH ₃ OCOOCH ₃ (dimethyl carbonate: DMC), CH ₃ CH ₂ OCOOCH ₂ CH ₃ (diethyl carbonate: DEC), CH ₃ CH ₂ OCOOCH ₃ (ethyl methyl carbonate: EMC). ), CH ₃ OCOOCH ₂ CH ₂ CH ₃ (methylpropyl carbonate), methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, and other hydrocarbon-based chain carbonates. Among these, at least one selected from the group consisting of ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate is preferable.

The content of the non-fluorinated chain carbonate is preferably 0 to 99% by volume in the solvent, more preferably 1% by volume or more, and more preferably 90% by volume or less.

When the solvent contains a fluorinated saturated cyclic carbonate and a fluorinated chain carbonate, the content ratio of the fluorinated cyclic saturated carbonate to the fluorinated chain carbonate is (10 to 90) / (90 to 10) in volume ratio. It is preferable that it is (20-80) / (80-20).

Further, when the solvent includes a fluorinated saturated cyclic carbonate, a fluorinated chain carbonate, and a non-fluorinated chain carbonate, the content ratio of the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate, and the non-fluorinated chain carbonate is The volume ratio is preferably (10 to 90) / (45 to 5) / (45 to 5), and more preferably (20 to 80) / (40 to 10) / (40 to 10).

Further, when the solvent contains fluorinated saturated cyclic carbonate, fluorinated chain carbonate and non-fluorinated cyclic carbonate, the content ratio of fluorinated saturated cyclic carbonate, fluorinated chain carbonate and non-fluorinated cyclic carbonate is The ratio is preferably (10 to 90) / (5 to 80) / (5 to 85), and more preferably (20 to 80) / (10 to 70) / (10 to 40).

When the solvent contains a fluorinated saturated cyclic carbonate, a fluorinated chain carbonate, a non-fluorinated cyclic carbonate, and a non-fluorinated chain carbonate, the fluorinated saturated cyclic carbonate, the fluorinated chain carbonate, and the non-fluorine. The content ratio of the fluorinated cyclic carbonate and the non-fluorinated chain carbonate is preferably (5-45) / (5-45) / (45-5) / (45-5), (10-40) / (10-40) / (40-10) / (40-10) is more preferable.

The electrolytic solution of the present invention preferably contains an electrolyte salt (excluding the compound (4)).
As the above electrolyte salt, in addition to lithium salt, ammonium salt, metal salt, liquid salt (ionic liquid), inorganic polymer type salt, organic polymer type salt, etc. can be used for electrolyte solution. Any thing can be used.

As an electrolyte salt of the electrolyte solution for a lithium ion secondary battery, a lithium salt is preferable.
Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiPF ₆ and LiBF ₄ ; LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF _{3 SO 2) (C 4 F} 9 SO 2), LiC (CF 3 SO 2) 3, LiPF 4 (CF 3) 2, LiPF 4 (C 2 F 5) 2, LiPF 4 (CF 3 SO 2) 2, LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ and a fluorine-containing salt or the like represented by the formula: LiPF _a (C _n F _{2n + 1} ) _6-a (wherein a is an integer of 0 to 5 and n is an integer of 1 to 6) Organic acid lithium Etc. The. These can be used alone or in combination of two or more.

Among them, the lithium salt, in that it is possible to suppress the deterioration after the electrolytic solution was stored at high _{temperatures, LiPF 6, LiBF 4, LiCF} 3 SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F ₅ SO ₂ ) ₂ and the formula: LiPF _a (C _n F _{2n + 1} ) _6-a (wherein, a is an integer of 0 to 5 and n is an integer of 1 to 6) It is preferably at least one selected from the group consisting of salts.

Examples of the salt represented by the formula: LiPF _a (C _n F _{2n + 1} ) _6-a include 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 , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (C ₃ F ₇ ) ₂ , LiPF ₄ (C ₄ F ₉ ) ₂ And the alkyl group represented by C ₃ F ₇ or C ₄ F ₉ in the formula may be either a straight chain or a branched structure.

The concentration of the lithium salt in the electrolytic solution is preferably 0.5 to 3 mol / liter. Outside this range, the electrical conductivity of the electrolytic solution tends to be low, and the battery performance tends to deteriorate.
The concentration of the electrolyte salt is more preferably 0.9 mol / liter or more, and more preferably 1.5 mol / liter or less.

As the electrolyte salt of the electrolytic solution for the electric double layer capacitor, an ammonium salt is preferable.
Examples of the ammonium salt include (IIa) to (IIe) below.
(IIa) Tetraalkyl quaternary ammonium salt general formula (IIa):

（式中、Ｒ^１ａ、Ｒ^２ａ、Ｒ^３ａ及びＲ^４ａは同じか又は異なり、いずれも炭素数１〜６のエーテル結合を含んでいてもよいアルキル基；Ｘ⁻はアニオン）で示されるテトラアルキル４級アンモニウム塩が好ましく例示できる。また、このアンモニウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４のフッ素化アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(Wherein R ^1a , R ^2a , R ^3a and R ^4a are the same or different, and all are alkyl groups optionally containing an ether bond having 1 to 6 carbon atoms; X ⁻ is an anion) Preferred examples include quaternary ammonium salts. Moreover, it is preferable from the point which oxidation resistance improves what a part or all of the hydrogen atom of this ammonium salt is substituted by the fluorine atom and / or the C1-C4 fluorinated alkyl group.

As a specific example, general formula (IIa-1):

（式中、Ｒ^１ａ、Ｒ^２ａ及びＸ⁻は前記と同じ；ｘ及びｙは同じか又は異なり０〜４の整数で、かつｘ＋ｙ＝４）で示されるテトラアルキル４級アンモニウム塩、一般式（ＩＩａ−２）：

(Wherein R ^1a , R ^2a and X ⁻ are the same as above; x and y are the same or different and are integers of 0 to 4 and x + y = 4), a tetraalkyl quaternary ammonium salt represented by the general formula ( IIa-2):

（式中、Ｒ^５ａは炭素数１〜６のアルキル基；Ｒ^６ａは炭素数１〜６の２価の炭化水素基；Ｒ^７ａは炭素数１〜４のアルキル基；ｚは１又は２；Ｘ⁻はアニオン）で示されるアルキルエーテル基含有トリアルキルアンモニウム塩、
などがあげられる。アルキルエーテル基を導入することにより、粘性の低下が図ることができる。

(Wherein R ^5a is an alkyl group having 1 to 6 carbon atoms; R ^6a is a divalent hydrocarbon group having 1 to 6 carbon atoms; R ^7a is an alkyl group having 1 to 4 carbon atoms; z is 1 or 2; X ^- is an alkyl ether group containing trialkylammonium salt represented by the anion),
Etc. By introducing an alkyl ether group, the viscosity can be lowered.

The anion X ⁻ may be an inorganic anion or an organic anion. Examples of the inorganic anion include AlCl ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , TaF ₆ ⁻ , I ⁻ and SbF ₆ ⁻ . Examples of the organic anion include CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ^{− and the} like.

Among these, BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , and SbF ₆ ⁻ are preferable from the viewpoint of good oxidation resistance and ion dissociation.

Specific examples of the tetraalkyl quaternary ammonium salt include Et ₄ NBF ₄ , Et ₄ NClO ₄ , Et ₄ NPF ₆ , Et ₄ NAsF ₆ , Et ₄ NSbF ₆ , Et ₄ NCF ₃ SO ₃ , Et ₄ N _{CF 3 SO 2) 2 N,} Et 4 NC 4 F 9 SO 3, Et 3 MeNBF 4, Et 3 MeNClO 4, Et 3 MeNPF 6, Et 3 MeNAsF 6, Et 3 MeNSbF 6, Et 3 MeNCF 3 SO 3, Et _{3 MeN (CF 3 SO 2)} 2 N, may be used _{Et 3 MeNC 4 F 9 SO 3} , in _{particular, Et 4 NBF 4, Et 4} NPF 6, Et 4 NSbF 6, Et 4 NAsF 6, Et 3 MeNBF 4 N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium salt and the like. I can get lost.

(IIb) Spiro ring bipyrrolidinium salt general formula (IIb-1):

（式中、Ｒ^８ａ及びＲ^９ａは同じか又は異なり、いずれも炭素数１〜４のアルキル基；Ｘ⁻はアニオン；ｎ１は０〜５の整数；ｎ２は０〜５の整数）で示されるスピロ環ビピロリジニウム塩、一般式（ＩＩｂ−２）：

(Wherein R ^8a and R ^9a are the same or different and both are alkyl groups having 1 to 4 carbon atoms; X ⁻ is an anion; n1 is an integer of 0 to 5; n2 is an integer of 0 to 5) Spirocyclic bipyrrolidinium salt, general formula (IIb-2):

（式中、Ｒ^１０ａ及びＲ^１１ａは同じか又は異なり、いずれも炭素数１〜４のアルキル基；Ｘ⁻はアニオン；ｎ３は０〜５の整数；ｎ４は０〜５の整数）で示されるスピロ環ビピロリジニウム塩、又は、一般式（ＩＩｂ−３）：

(Wherein, R ^10a and R ^11a are the same or different, and both are alkyl groups having 1 to 4 carbon atoms; X ⁻ is an anion; n3 is an integer of 0 to 5; n4 is an integer of 0 to 5) Spiro ring bipyrrolidinium salt or general formula (IIb-3):

（式中、Ｒ^１２ａおよびＲ^１３ａは同じかまたは異なり、いずれも炭素数１〜４のアルキル基；Ｘ⁻はアニオン；ｎ５は０〜５の整数；ｎ６は０〜５の整数）で示されるスピロ環ビピロリジニウム塩が好ましく挙げられる。また、このスピロ環ビピロリジニウム塩の水素原子の一部または全部がフッ素原子および／または炭素数１〜４のフッ素化アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(Wherein R ^12a and R ^13a are the same or different and both are alkyl groups having 1 to 4 carbon atoms; X ⁻ is an anion; n5 is an integer of 0 to 5; n6 is an integer of 0 to 5) Spiro ring bipyrrolidinium salts are preferred. Moreover, it is preferable from the point which oxidation resistance improves what part or all of the hydrogen atom of this spiro ring bipyrrolidinium salt substituted with the fluorine atom and / or the C1-C4 fluorinated alkyl group.

Preferred examples of the anion X ⁻ are the same as in the case of (IIa). Among them, BF ₄ −, PF ₆ −, (CF ₃ SO ₂ ) ₂ N- or (C ₂ F ₅ SO ₂ ) ₂ N− is preferable because of its high dissociation property and low internal resistance under high voltage. preferable.

などが挙げられる。 Preferable specific examples of the spiro ring bipyrrolidinium salt include, for example,

Etc.

This spiro ring bipyrrolidinium salt is excellent in terms of solubility in a solvent, oxidation resistance, and ionic conductivity.

(IIc) Imidazolium salt general formula (IIc):

（式中、Ｒ^１４ａ及びＲ^１５ａは同じか又は異なり、いずれも炭素数１〜６のアルキル基；Ｘ⁻はアニオン）
で示されるイミダゾリウム塩が好ましく例示できる。また、このイミダゾリウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４のフッ素化アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(In the formula, R ^14a and R ^15a are the same or different and both are alkyl groups having 1 to 6 carbon atoms; X ⁻ is an anion)
The imidazolium salt shown by can be illustrated preferably. In addition, the imidazolium salt in which part or all of the hydrogen atoms are substituted with a fluorine atom and / or a fluorinated alkyl group having 1 to 4 carbon atoms is preferable from the viewpoint of improving oxidation resistance.

Preferred specific examples of the anion X ⁻ are the same as those in (IIa).

As a preferable specific example, for example,

等が挙げられる。

Etc.

This imidazolium salt is excellent in terms of low viscosity and good solubility.

(IId): N-alkylpyridinium salt general formula (IId):

（式中、Ｒ^１６ａは炭素数１〜６のアルキル基；Ｘ⁻はアニオン）
で示されるＮ−アルキルピリジニウム塩が好ましく例示できる。また、このＮ−アルキルピリジニウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４のフッ素化アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(Wherein R ^16a is an alkyl group having 1 to 6 carbon atoms; X ⁻ is an anion)
An N-alkylpyridinium salt represented by the formula is preferably exemplified. Moreover, what substituted a part or all of the hydrogen atom of this N-alkyl pyridinium salt by the fluorine atom and / or the C1-C4 fluorinated alkyl group is preferable from the point which oxidation resistance improves.

Preferred specific examples of the anion X ⁻ are the same as those in (IIa).

As a preferable specific example, for example,

などが挙げられる。

Etc.

This N-alkylpyridinium salt is excellent in that it has low viscosity and good solubility.

(IIe) N, N-dialkylpyrrolidinium salt general formula (IIe):

（式中、Ｒ^１７ａ及びＲ^１８ａは同じか又は異なり、いずれも炭素数１〜６のアルキル基；Ｘ⁻はアニオン）
で示されるＮ，Ｎ−ジアルキルピロリジニウム塩が好ましく例示できる。また、このＮ，Ｎ−ジアルキルピロリジニウム塩の水素原子の一部又は全部がフッ素原子及び／又は炭素数１〜４のフッ素化アルキル基で置換されているものも、耐酸化性が向上する点から好ましい。

(Wherein, R ^17a and R ^18a are the same or different and both are alkyl groups having 1 to 6 carbon atoms; X ⁻ is an anion)
N, N-dialkylpyrrolidinium salts represented by Moreover, the oxidation resistance of the N, N-dialkylpyrrolidinium salt in which part or all of the hydrogen atoms are substituted with fluorine atoms and / or fluorinated alkyl groups having 1 to 4 carbon atoms is improved. It is preferable from the point.

Preferred specific examples of the anion X ⁻ are the same as those in (IIa).

As a preferable specific example, for example,

などが挙げられる。

Etc.

This N, N-dialkylpyrrolidinium salt is excellent in terms of low viscosity and good solubility.

Of these ammonium salts, (IIa), (IIb) and (IIc) are preferable in terms of good solubility, oxidation resistance and ionic conductivity,

（式中、Ｍｅはメチル基；Ｅｔはエチル基；Ｘ⁻、ｘ、ｙは式（ＩＩａ−１）と同じ）が好ましい。

In the formula, Me is a methyl group; Et is an ethyl group; X ⁻ , x, and y are the same as those in the formula (IIa-1).

Moreover, you may use lithium salt as electrolyte salt for electrical double layer capacitors. Examples of the lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF 6, LiN (SO 2 C 2 H 5) 2 is preferred.
In order to further improve the capacity, a magnesium salt may be used. As the magnesium salt, for example, Mg (ClO ₄ ) ₂ , Mg (OOC ₂ H ₅ ) _{2 and the} like are preferable.

When the electrolyte salt is the ammonium salt, the concentration is preferably 1.1 mol / liter or more. If it is less than 1.1 mol / liter, not only the low-temperature characteristics are deteriorated, but also the initial internal resistance is increased. The concentration of the electrolyte salt is more preferably 1.25 mol / liter or more.
The concentration is preferably 1.7 mol / liter or less, more preferably 1.5 mol / liter or less, from the viewpoint of low temperature characteristics.
When the ammonium salt is triethylmethylammonium tetrafluoroborate (TEMABF ₄ ), the concentration is preferably 1.1 to 1.4 mol / liter in terms of excellent low temperature characteristics.
In the case of spirobipyrrolidinium tetrafluoroborate (SBPBF ₄ ), it is preferably 1.3 to 1.7 mol / liter.

The electrolytic solution of the present invention preferably further contains a polyethylene oxide having a weight average molecular weight of 2000 to 4000 and having —OH, —OCOOH, or —COOH at the terminal.
By containing such a compound, the stability of the electrode interface can be improved and the battery characteristics can be improved.
Examples of the polyethylene oxide include polyethylene oxide monool, polyethylene oxide carboxylic acid, polyethylene oxide diol, polyethylene oxide dicarboxylic acid, polyethylene oxide triol, and polyethylene oxide tricarboxylic acid. These may be used alone or in combination of two or more.
Of these, a mixture of polyethylene oxide monool and polyethylene oxide diol, and a mixture of polyethylene carboxylic acid and polyethylene dicarboxylic acid are preferable in terms of better battery characteristics.

If the weight average molecular weight of the polyethylene oxide is too small, it may be easily oxidized and decomposed. The weight average molecular weight is more preferably 3000 to 4000.
The said weight average molecular weight can be measured by polystyrene conversion by a gel permeation chromatography (GPC) method.

The polyethylene oxide content is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / kg in the electrolytic solution. When there is too much content of the said polyethylene oxide, there exists a possibility that a battery characteristic may be impaired.
The polyethylene oxide content is more preferably 5 × 10 ⁻⁶ mol / kg or more.

The electrolytic solution of the present invention may further contain at least one selected from the group consisting of an unsaturated cyclic carbonate and a cyclic sulfonic acid compound as an additive. By containing these compounds, deterioration of battery characteristics can be suppressed.

The unsaturated cyclic carbonate is a cyclic carbonate containing an unsaturated bond, that is, a cyclic carbonate having at least one carbon-carbon unsaturated bond in the molecule. Specifically, for example, vinylene carbonate compounds such as vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate; 4-vinylethylene carbonate (VEC), 4- Methyl-4-vinylethylene carbonate, 4-ethyl-4-vinylethylene carbonate, 4-n-propyl-4-vinylethylene carbonate, 5-methyl-4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4, Examples thereof include vinyl ethylene carbonate compounds such as 5-divinylethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate, and 4,4-diethyl-5-methylene ethylene carbonate. Among these, vinylene carbonate, 4-vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate or 4,5-divinylethylene carbonate is preferable, and vinylene carbonate or 4-vinylethylene carbonate is particularly preferable.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to electrolyte solution, and the effect of this invention will fully be expressed easily. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more, and more preferably 150 or less.

Moreover, as an unsaturated cyclic carbonate, a fluorinated unsaturated cyclic carbonate can also be used suitably.
The number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and most preferably 1 or 2 fluorine atoms.

Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives, fluorinated ethylene carbonate derivatives substituted with an aromatic ring or a substituent having a carbon-carbon double bond.
Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluor-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.

Examples of the fluorinated ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon double bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5. -Vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate 4,5-diflu B-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4- Examples thereof include phenylethylene carbonate.

The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 500 or less. If it is this range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to electrolyte solution, and the effect of this invention will be easy to be expressed.

The said unsaturated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

Examples of the cyclic sulfonic acid compound include 1,3-propane sultone, 1,4-butane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, and 3-fluoro-1 , 3-propane sultone and the like. Especially, it is preferable that the electrolyte solution of this invention contains a 1, 3- propane sultone and / or a 1, 4- butane sultone from the point which can improve a high temperature characteristic.

When at least one compound selected from the group consisting of the unsaturated cyclic carbonate and the cyclic sulfonic acid compound is used as an additive, the content thereof may be 0.1 to 10% by mass in the electrolytic solution. Preferably, 1 mass% or more is more preferable, and 5 mass% or less is more preferable.

The electrolyte solution of the present invention includes cyclic and chain carboxylic acid esters, ether compounds, nitrogen-containing compounds, boron-containing compounds, organosilicon-containing compounds, non-flammable (flame retardant) agents, and interfaces as long as the effects of the present invention are not impaired. Other solvents or additives such as activators, high dielectric additives, cycle and rate characteristics improvers, or overcharge inhibitors may also be included.

Examples of the cyclic carboxylic acid ester include those having 3 to 12 total carbon atoms in the structural formula. Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

The compounding quantity of cyclic carboxylic acid ester is 100 mass% of solvent normally, Preferably it is 0.1 mass% or more, More preferably, it is 1 mass% or more. Within this range, the electrical conductivity of the electrolytic solution is improved, and the large current discharge characteristics of the electrolytic solution battery are easily improved. Moreover, the compounding quantity of cyclic carboxylic acid ester becomes like this. Preferably it is 10 mass% or less, More preferably, it is 5 mass% or less. By setting the upper limit in this way, the viscosity of the electrolytic solution is set in an appropriate range, the decrease in electrical conductivity is avoided, the increase in negative electrode resistance is suppressed, and the large current discharge characteristics of the electrolytic solution battery are set in a favorable range. Make it easier.

Further, as the cyclic carboxylic acid ester, a fluorinated cyclic carboxylic acid ester (fluorinated lactone) can also be suitably used. Examples of the fluorine-containing lactone include the following formula (E):

(Wherein X ^{15 to} X ²⁰ are the same or different and all are —H, —F, —Cl, —CH ₃ or a fluorinated alkyl group; provided that at least one of X ^{15 to} X ²⁰ is a fluorinated alkyl. A fluorine-containing lactone represented by the following formula:

Examples of the fluorinated alkyl group for X ^{15 to} X ²⁰ include —CFH ₂ , —CF ₂ H, —CF ₃ , —CH ₂ CF ₃ , —CF ₂ CF ₃ , —CH ₂ CF ₂ CF ₃ , —CF (CF ₃ ) _{2 and the} like are mentioned, and —CH ₂ CF ₃ and —CH ₂ CF ₂ CF ₃ are preferred from the viewpoint of high oxidation resistance and an effect of improving safety.

If at least one of X ^{15 to} X ²⁰ is a fluorinated alkyl group, —H, —F, —Cl, —CH ₃ or the fluorinated alkyl group is substituted at only one position of X ^{15 to} X ^20. Alternatively, a plurality of locations may be substituted. Preferably, the number of the electrolyte salt is 1 to 3 and preferably 1 to 2 from the viewpoint of good solubility of the electrolyte salt.

But it is not fluorinated alkyl group substituted position particularly limited to, since the synthesis yields ^{good, X 17} and / or ^{X 18} is, in particular ^{X 17} or ^{X 18} is a fluorinated alkyl group, inter alia _-CH 2 CF ₃ , —CH ₂ CF ₂ CF ₃ is preferable. X ^{15 to} X ²⁰ other than the fluorinated alkyl group are —H, —F, —Cl or CH ₃ , and —H is particularly preferable from the viewpoint of good solubility of the electrolyte salt.

Examples of the fluorine-containing lactone include those represented by the following formula (F):

(In the formula, either one of A and B is CX ²⁶ X ²⁷ (X ²⁶ and X ²⁷ are the same or different, and all are —H, —F, —Cl, —CF ₃ , —CH ₃ or a hydrogen atom) An alkylene group which may be substituted with a halogen atom and may contain a hetero atom in the chain), the other is an oxygen atom; Rf ¹² is a fluorinated alkyl group or a fluorinated group which may have an ether bond An alkoxy group; X ²¹ and X ²² are the same or different; all are —H, —F, —Cl, —CF ₃ or CH ₃ ; X ^{23 to} X ²⁵ are the same or different and both are —H, —F , -Cl or an alkyl group in which a hydrogen atom may be substituted with a halogen atom and may contain a hetero atom in the chain; and a fluorine-containing lactone represented by n = 0 or 1).

Examples of the fluorine-containing lactone represented by the formula (F) include the following formula (G):

(In the formula, A, B, Rf ¹² , X ²¹ , X ²² and X ²³ are the same as those in formula (F)), the 5-membered ring structure is easy to synthesize and has chemical stability. It is preferably mentioned from a favorable point, and further, by the combination of A and B, the following formula (H):

(Wherein Rf ¹² , X ²¹ , X ²² , X ²³ , X ²⁶ and X ²⁷ are the same as those in formula (F)), and the following formula (I):

(Wherein Rf ¹² , X ²¹ , X ²² , X ²³ , X ²⁶ and X ²⁷ are the same as those in formula (F)).

Among these, the point that the excellent characteristics such as high dielectric constant and high withstand voltage can be exhibited especially, and the characteristics as the electrolytic solution in the present invention are improved in that the solubility of the electrolyte salt and the reduction of internal resistance are good. From

等が挙げられる。
フッ素化環状カルボン酸エステルを含有させることにより、イオン伝導度の向上、安全性の向上、高温時の安定性向上といった効果が得られる。

Etc.
By including the fluorinated cyclic carboxylic acid ester, effects such as improvement in ionic conductivity, improvement in safety, and improvement in stability at high temperatures can be obtained.

Examples of the chain carboxylic acid ester include those having 3 to 7 carbon atoms in the structural formula. Specifically, methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyric acid-n- Examples include propyl and isopropyl isobutyrate.

Among them, methyl acetate, ethyl acetate, acetate-n-propyl, acetate-n-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. are ions due to viscosity reduction. It is preferable from the viewpoint of improvement of conductivity.

Moreover, fluorinated chain carboxylic acid ester can also be used suitably. As the fluorine-containing ester, the following formula (J):
Rf ¹⁰ COORf ¹¹ (J)
(Wherein Rf ¹⁰ is a fluorinated alkyl group having 1 to 2 carbon atoms and Rf ¹¹ is a fluorinated alkyl group having 1 to 4 carbon atoms), the flame-retardant property is high, And it is preferable from the viewpoint of good compatibility with other solvents and oxidation resistance.

Examples of Rf ¹⁰ include CF _3- , CF ₃ CF _2- , HCF ₂ CF _2- , HCF _2- , CH ₃ CF _2- , CF ₃ CH _2-, and the like, among others CF _3- , CF ₃ CF ₂ − is particularly preferable from the viewpoint of good rate characteristics.

The Rf ^11, for _{example, CF 3 -, CF 3 CF} 2 -, (CF 3) 2 CH-, CF 3 CH 2 -, CF 3 CH 2 CH 2 -, CF 3 CFHCF 2 CH 2 -, C 2 F ₅ CH _2- , CF ₂ HCF ₂ CH _2- , C ₂ F ₅ CH ₂ CH _2- , CF ₃ CF ₂ CH _2- , CF ₃ CF ₂ CF ₂ CH _2-, etc. can be exemplified, among which CF ₃ CH _2- , (CF ₃ ) ₂ CH—, C ₂ F ₅ CH ₂ —, and CF ₂ HCF ₂ CH ₂ — are particularly preferred from the viewpoint of good compatibility with other solvents.

Specific examples of the fluorinated chain carboxylic acid ester include, for example, CF ₃ C (═O) OCH ₂ CF ₃ , CF ₃ C (═O) OCH ₂ CH ₂ CF ₃ , and CF ₃ C (═O) OCH ₂ C. _{One or more of 2} F ₅ , CF ₃ C (═O) OCH ₂ CF ₂ CF ₂ H, CF ₃ C (═O) OCH (CF ₃ ) _2, etc. can be exemplified, among which CF ₃ C ( _{= O) OCH 2 C 2 F} 5, CF 3 C (= O) OCH 2 CF 2 CF 2 H, CF 3 C (= O) OCH 2 CF 3, CF 3 C (= O) OCH (CF 3) 2 However, the compatibility with other solvents and the rate characteristics are particularly preferable.

The ether compound is preferably a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms.
Examples of the chain ether having 3 to 10 carbon atoms include diethyl ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, and ethylene glycol di-n-propyl. Examples include ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, and the like.

Further, as the ether compound, a fluorinated ether can also be suitably used.
As the fluorinated ether, the following general formula (K):
^{Rf 1 -O-Rf 2 (K} )
(In the formula, Rf ¹ and Rf ² are the same or different and are an alkyl group having 1 to 10 carbon atoms or a fluorinated alkyl group having 1 to 10 carbon atoms, provided that at least one of Rf ¹ and Rf ² is fluorine. A fluorinated ether (K) represented by the following formula: By containing the fluorinated ether (K), the flame retardancy of the electrolytic solution is improved, and the stability and safety at high temperature and high voltage are improved.

In the general formula (K), at least one of Rf ¹ and Rf ² may be a fluorinated alkyl group having 1 to 10 carbon atoms. However, the flame retardancy of the electrolyte solution, stability at high temperature and high voltage, and safety From the viewpoint of further improving the properties, it is preferable that both Rf ¹ and Rf ² are fluorinated alkyl groups having 1 to 10 carbon atoms. In this case, Rf ¹ and Rf ² may be the same or different from each other.
Among them, Rf ¹ and Rf ² are the same or different, Rf ¹ is a fluorinated alkyl group having 3 to 6 carbon atoms, and Rf ² is a fluorinated alkyl group having 2 to 6 carbon atoms. preferable.

When the total carbon number of Rf ¹ and Rf ² is too small, the boiling point of the fluorinated ether becomes too low, and when the carbon number of Rf ¹ or Rf ² is too large, the solubility of the electrolyte salt decreases, and other solvents As a result, the compatibility with the resin begins to have an adverse effect, and since the viscosity increases, the rate characteristics are reduced. When Rf ¹ has 3 or 4 carbon atoms and Rf ² has 2 or 3 carbon atoms, it is advantageous in that it has excellent boiling point and rate characteristics.

The fluorinated ether (K) preferably has a fluorine content of 40 to 75% by mass. When it has a fluorine content in this range, it is particularly excellent in the balance between incombustibility and compatibility. Moreover, it is preferable also from a point with favorable oxidation resistance and safety | security.
The lower limit of the fluorine content is more preferably 45% by mass, still more preferably 50% by mass, and particularly preferably 55% by mass. The upper limit is more preferably 70% by mass, and still more preferably 66% by mass.
The fluorine content of the fluorinated ether (K) is {(number of fluorine atoms × 19) / molecular weight of the fluorinated ether (K)} × 100 (% based on the structural formula of the fluorinated ether (K). ).

Examples of Rf ¹ include CF ₃ CF ₂ CH ₂ —, CF ₃ CFHCF ₂ —, HCF ₂ CF ₂ CF ₂ —, HCF ₂ CF ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CH ₂ —, CF ₃ CFHCF. _{2 CH 2 -, HCF 2 CF} 2 CF 2 CF 2 -, HCF 2 CF 2 CF 2 CH 2 -, HCF 2 CF 2 CH 2 CH 2 -, HCF 2 CF (CF 3) CH 2 - and the like.
Examples of Rf ² include CF ₃ CF ₂ CH ₂ —, CF ₃ CFHCF ₂ —, CF ₂ HCF ₂ CF ₂ —, CF ₂ HCF ₂ CH ₂ —, CF ₃ CF ₂ CH ₂ CH ₂ —, CF _{3 CFHCF 2 CH 2 -, CF} 2 HCF 2 CF 2 CF 2 -, CF 2 HCF 2 CF 2 CH 2 -, CF 2 HCF 2 CH 2 CH 2 -, CF 2 HCF (CF 3) CH 2 -, CF 2 _{HCF 2 -, CF 2 HCH 2} -, CH 3 CF 2 - , and the like.

Specific examples of the fluorinated ether (K) include, for example, HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H, CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H, HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , CF ₃ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , C ₆ F ₁₃ OCH ₃ , C ₆ F ₁₃ OC ₂ H ₅ , C ₈ F ₁₇ OCH ₃ , C ₈ F ₁₇ OC ₂ H ₅ , CF ₃ CFHCF ₂ CH (CH ₃ ) OCF ₂ CFHCF ₃ , HCF ₂ CF ₂ OCH (C ₂ H ₅ ) ₂ , HCF ₂ CF ₂ OC ₄ H ₉ , HCF ₂ CF ₂ OCH ₂ CH (C ₂ H ₅ ) ₂ , HCF ₂ CF ₂ OCH ₂ CH _{(CH 3) 2} or the like can be mentioned.

Among them, HCF ₂ at one or both ends - or _CF 3 -CFH- is excellent polarizable those containing, can give a high boiling point fluorinated ethers (K). The boiling point of the fluorinated ether (K) is preferably 67 to 120 ° C. More preferably, it is 80 degreeC or more, More preferably, it is 90 degreeC or more.

Examples of such a fluorinated ether (K) include CF ₃ CH ₂ OCF ₂ CFHCF ₃ , CF ₃ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ , and HCF ₂ CF ₂ CH. _{2 OCH 2 CF 2 CF 2 H} , CF 3 CFHCF 2 CH 2 OCF 2 CFHCF 3, HCF 2 CF 2 CH 2 OCF 2 CF 2 H, CF 3 CF 2 CH 2 OCF 2 CF 2 1 type of H, etc. or two The above is mentioned.
Of these, HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ (boiling point 106 ° C.), CF ₃ CF ₂ CH is advantageous because of its high boiling point, compatibility with other solvents, and good solubility of the electrolyte salt. ₂ OCF ₂ CFHCF ₃ (boiling point 82 ° C.), HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H (boiling point 92 ° C.) and CF ₃ CF ₂ CH ₂ OCF ₂ CF ₂ H (boiling point 68 ° C.). And at least one selected from the group consisting of HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ (boiling point 106 ° C.) and HCF ₂ CF ₂ CH ₂ OCF ₂ CF ₂ H (boiling point 92 ° C.). One type is more preferable.

Examples of the cyclic ether having 3 to 6 carbon atoms include 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane and the like and fluorinated compounds thereof. Is mentioned. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and improve the degree of ion dissociation. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferable because they have low viscosity and give high ionic conductivity.

Examples of the nitrogen-containing compound include nitrile, fluorine-containing nitrile, carboxylic acid amide, fluorine-containing carboxylic acid amide, sulfonic acid amide, and fluorine-containing sulfonic acid amide. In addition, 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxaziridinone, 1,3-dimethyl-2-imidazolidinone, N-methylsuccinimide and the like can also be used.

Examples of the boron-containing compound include boric acid esters such as trimethyl borate and triethyl borate, boric ether, and alkyl borate.

Examples of the organosilicon-containing compound include (CH ₃ ) ₄ —Si, (CH ₃ ) ₃ —Si—Si (CH ₃ ) _{3, and the} like.

Examples of the incombustible (flame retardant) agent include phosphate esters and phosphazene compounds. Examples of the phosphate ester include fluorine-containing alkyl phosphate esters, non-fluorinated alkyl phosphate esters, and aryl phosphate esters. Especially, it is preferable that it is a fluorine-containing alkyl phosphate ester at the point which can exhibit a nonflammable effect in a small quantity.

Specific examples of the fluorine-containing alkyl phosphate ester include fluorine-containing dialkyl phosphate esters described in JP-A No. 11-233141 and cyclic alkyl phosphate esters described in JP-A No. 11-283669. Or fluorine-containing trialkyl phosphate ester etc. are mentioned.

As the nonflammable (flame retardant) agent, (CH ₃ O) ₃ P═O, (CF ₃ CH ₂ O) ₃ P═O, and the like are preferable.

The surfactant may be any of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant. From the viewpoint of good cycle characteristics and rate characteristics, a fluorine atom It is preferable that it contains.

As such a surfactant containing a fluorine atom, for example, the following formula:
Rf ¹ COO ⁻ M ⁺
Wherein Rf ¹ is a fluorinated alkyl group that may contain an ether bond having 3 to 10 carbon atoms; M ⁺ is Li ⁺ , Na ⁺ , K ⁺ or NHR ′ ₃ ⁺ (R ′ is the same or different , Each of which is H or an alkyl group having 1 to 3 carbon atoms)) or a fluorine-containing carboxylate represented by the following formula:
Rf ² SO ₃ ⁻ M ⁺
(Wherein Rf ² is a fluorinated alkyl group that may contain an ether bond having 3 to 10 carbon atoms; M ⁺ is Li ⁺ , Na ⁺ , K ⁺ or NHR ′ ₃ ⁺ (R ′ is the same or different) Are preferably H or an alkyl group having 1 to 3 carbon atoms).

The content of the surfactant is preferably 0.01 to 2% by mass in the electrolytic solution from the viewpoint that the surface tension of the electrolytic solution can be reduced without reducing the charge / discharge cycle characteristics.

Examples of the high dielectric additive include sulfolane, methyl sulfolane, γ-butyrolactone, γ-valerolactone, acetonitrile, propionitrile and the like.

Examples of the cycle characteristic and rate characteristic improving agent include methyl acetate, ethyl acetate, tetrahydrofuran, 1,4-dioxane and the like.

The overcharge preventing agent is preferably an overcharge preventing agent having an aromatic ring in that the battery can be prevented from being ruptured or ignited during overcharging. Examples of the overcharge preventing agent having an aromatic ring include cyclohexylbenzene, biphenyl, alkylbiphenyl, terphenyl, terphenyl partial hydride, t-butylbenzene, t-amylbenzene, diphenyl ether, benzofuran, dibenzofuran, dichloroaniline. , Aromatic compounds such as toluene; fluorides of aromatic compounds such as hexafluorobenzene, fluorobenzene, 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5 -Fluorinated anisole compounds such as difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole. Of these, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, terphenyl partially hydrogenated, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge prevention property and a high temperature storage property. From the standpoint of balance.
The content of the overcharge inhibitor is preferably 0.1 to 5% by mass in the electrolyte solution in that the battery can be prevented from bursting or firing in the case of overcharging or the like.

The electrolytic solution of the present invention may further contain other known auxiliary agents as long as the effects of the present invention are not impaired. Examples of other known auxiliary agents include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, and methoxyethyl-methyl carbonate; 2,4,8,10-tetraoxaspiro [5,5] Spiro compounds such as undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5,5] undecane; ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, methane Chain sulfone such as ethyl sulfonate, busulfan, sulfolene, diphenyl sulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, fluorine-containing chain sulfone, chain-like sulfonate, fluorine-containing chain sulfone Acid ester, cyclic sulfone Fluorinated cyclic sulfones, sulfur-containing compounds such as sulfonic acid halides and fluorinated sulfonic acid halides; heptane, octane, nonane, decane, fluorinated aromatic compounds such as hydrocarbon compounds cycloheptane and the like, and the like. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved.

Further, the electrolytic solution of the present invention may be further combined with a polymer material to form a gel (plasticized) gel electrolytic solution.

Examples of such a polymer material include conventionally known polyethylene oxide and polypropylene oxide, modified products thereof (JP-A-8-222270 and JP-A-2002-1000040); polyacrylate polymers, polyacrylonitrile, and polyvinylidene fluoride. , Fluororesins such as vinylidene fluoride-hexafluoropropylene copolymer (JP-A-4-506726, JP-A-8-507407, JP-A-10-294131); these fluororesins and hydrocarbons Examples include composites with resins (Japanese Patent Laid-Open Nos. 11-35765 and 11-86630). In particular, it is desirable to use polyvinylidene fluoride or a vinylidene fluoride-hexafluoropropylene copolymer as the polymer material for the gel electrolyte.

In addition, the electrolytic solution of the present invention may also contain an ion conductive compound described in Japanese Patent Application No. 2004-301934.

This ion conductive compound has the formula (1-1):
A- (D) -B (1-1)
[Wherein D represents the formula (2-1):
-(D1) _n- (FAE) _m- (AE) _p- (Y) _q- (2-1)
(In the formula, D1 represents the formula (2a):

(Wherein, Rf is a fluorine-containing ether group which may have a crosslinkable functional group; the R ¹⁰ group or a bond that binds the Rf main chain) ether having a fluorine-containing ether group in the side chain represented by unit;
FAE is represented by formula (2b):

(Wherein, Rfa is hydrogen atom, a crosslinkable functional group may have a fluorinated alkyl group; R ¹¹ is a group or a bond that binds the Rfa main chain) a fluorinated alkyl group in the side chain indicated by Ether units having:
AE is the formula (2c):

(In the formula, R ¹³ has a hydrogen atom, an alkyl group which may have a crosslinkable functional group, an aliphatic cyclic hydrocarbon group which may have a crosslinkable functional group, or a crosslinkable functional group. An aromatic hydrocarbon group which may be present; R ¹² is an ether unit represented by R ¹³ and a group or a bond which bonds the main chain;
Y represents formulas (2d-1) to (2d-3):

A unit comprising at least one of
n is an integer of 0 to 200; m is an integer of 0 to 200; p is an integer of 0 to 10000; q is an integer of 1 to 100; provided that n + m is not 0, and the bonding order of D1, FAE, AE and Y is Not specified);
A and B are the same or different and are a hydrogen atom, a fluorine atom and / or an alkyl group which may contain a crosslinkable functional group, a phenyl group which may contain a fluorine atom and / or a crosslinkable functional group, -COOH A group, —OR (wherein R is a hydrogen atom or a fluorine atom and / or an alkyl group which may contain a crosslinkable functional group), an ester group or a carbonate group (provided that when D is an oxygen atom, a —COOH group, -OR, not an ester group or a carbonate group)].

You may mix | blend another additive with the electrolyte solution of this invention as needed. Examples of other additives include metal oxide and glass.

The electrolyte solution of the present invention preferably contains 0.5 to 70 ppm of HF. By containing HF, the film formation of the additive can be promoted. When the content of HF is too small, the film forming ability of the additive on the negative electrode is lowered, and the battery characteristics tend to be lowered. Moreover, when there is too much HF content, there exists a tendency for the oxidation resistance of electrolyte solution to fall under the influence of HF. Even when the electrolytic solution of the present invention contains HF in the above range, the high temperature storage capacity recovery capacity ratio of the battery does not decrease.
The content of HF is more preferably 1 ppm or more, and further preferably 2.5 ppm or more. The content of HF is more preferably 60 ppm or less, still more preferably 50 ppm or less, and particularly preferably 30 ppm or less.
The content of HF can be measured by a neutralization titration method.

The electrolytic solution of the present invention may be prepared by any method using the components described above.

The electrolyte solution of the present invention can be suitably applied to electrochemical devices such as lithium ion secondary batteries and electric double layer capacitors. Such an electrochemical device provided with the electrolytic solution of the present invention is also one aspect of the present invention.

Electrochemical devices include lithium secondary batteries, capacitors (electric double layer capacitors), radical batteries, solar cells (especially dye-sensitized solar cells), fuel cells, various electrochemical sensors, electrochromic elements, and electrochemical switching elements. , Aluminum electrolytic capacitors, tantalum electrolytic capacitors, and the like, and lithium secondary batteries and electric double layer capacitors are preferable.

The lithium ion secondary battery may include a positive electrode, a negative electrode, and the above-described electrolytic solution.

<Positive electrode>
A positive electrode is comprised from the positive electrode mixture containing the positive electrode active material which is a material of a positive electrode, and a collector.

The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. For example, a material containing lithium and at least one transition metal is preferable. Specific examples include lithium-containing transition metal composite oxides and lithium-containing transition metal phosphate compounds. Especially, as a positive electrode active material, the lithium containing transition metal complex oxide which produces a high voltage is especially preferable.
Examples of the lithium-containing transition metal composite oxide include:
Formula: Li _a Mn _2-b M ¹ _b O ₄ (where 0.9 ≦ a; 0 ≦ b ≦ 1.5; M ¹ is Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, A lithium-manganese spinel composite oxide represented by V, Ti, Mg, Ca, Sr, B, Ga, In, Si, and Ge).
Formula: LiNi _1-c M ² _c O ₂ (where 0 ≦ c ≦ 0.5; M ² is Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Lithium-nickel composite oxide represented by (at least one metal selected from the group consisting of Sr, B, Ga, In, Si and Ge), or
Formula: LiCo _1-d M ³ _d O ₂ (where 0 ≦ d ≦ 0.5; M ³ is Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Lithium-cobalt composite oxide represented by at least one metal selected from the group consisting of Sr, B, Ga, In, Si, and Ge.

Among them, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ can be provided because the lithium ion secondary battery with high energy density and high output can be provided. Or LiNi _1/3 Co _1/3 Mn _1/3 O ₂ is preferred.

As other positive electrode active materials, LiFePO ₄ , LiNi _0.8 Co _0.2 O ₂ , Li _1.2 Fe _0.4 Mn _0.4 O ₂ , LiNi _0.5 Mn _0.5 O ₂ , LiV ₃ O ₆ etc. are mentioned.

In addition, it is preferable to include lithium phosphate in the positive electrode active material because continuous charge characteristics are improved. Although there is no restriction | limiting in the use of lithium phosphate, It is preferable to mix and use the said positive electrode active material and lithium phosphate. The lower limit of the amount of lithium phosphate to be used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass with respect to the total of the positive electrode active material and lithium phosphate. %, And the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less.

Moreover, you may use what the substance of the composition different from this adhered to the surface of the said positive electrode active material. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

For example, these surface adhering substances are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, and dried. After the surface adhering substance precursor is dissolved or suspended in a solvent and added to the positive electrode active material, It can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously. In addition, when making carbon adhere, the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.

The amount of the surface adhering substance is, in terms of mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, further preferably 10 ppm or more, and the upper limit, preferably 20% or less, more preferably as the lower limit. Is used at 10% or less, more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the electrolyte solution on the surface of the positive electrode active material and can improve the battery life. However, when the amount of the adhering quantity is too small, the effect is not sufficiently manifested. If it is too high, the resistance may increase in order to inhibit the entry and exit of lithium ions.

Examples of the shape of the particles of the positive electrode active material include a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, and a column shape as conventionally used. Moreover, primary particles may aggregate to form secondary particles.

The tap density of the positive electrode active material is preferably 0.5 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further preferably 1.0 g / cm ³ or more. If the tap density of the positive electrode active material is lower than the lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of conductive material and binder increases, so that the positive electrode to the positive electrode active material layer The filling rate of the active material is restricted, and the battery capacity may be restricted. By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as large as possible, and there is no particular upper limit, but if it is too large, diffusion of lithium ions using the electrolytic solution in the positive electrode active material layer as a medium is rate-limiting, and load characteristics may be easily reduced. The upper limit is preferably 4.0 g / cm ³ or less, more preferably 3.7 g / cm ³ or less, and still more preferably 3.5 g / cm ³ or less.
In the present invention, the tap density is 5 to 10 g of the positive electrode active material powder placed in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm, and the powder packing density (tap density) g / cm ^3. Asking.

The median diameter d50 of the positive electrode active material particles (secondary particle diameter when primary particles aggregate to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably. Is 0.8 μm or more, most preferably 1.0 μm or more, preferably 30 μm or less, more preferably 27 μm or less, further preferably 25 μm or less, and most preferably 22 μm or less. If the lower limit is not reached, a high tap density product may not be obtained. If the upper limit is exceeded, it takes time to diffuse lithium in the particles, so that the battery performance may be lowered, or the positive electrode of the battery, that is, the active material When a conductive material, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur. Here, by mixing two or more kinds of the positive electrode active materials having different median diameters d50, it is possible to further improve the filling property at the time of forming the positive electrode.

In the present invention, the median diameter d50 is measured by a known laser diffraction / scattering particle size distribution measuring device. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

When the primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, and still more preferably 0.8. The upper limit is preferably 5 μm or less, more preferably 4 μm or less, still more preferably 3 μm or less, and most preferably 2 μm or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the specific surface area is greatly reduced, so that there is a high possibility that battery performance such as output characteristics will deteriorate. is there. On the other hand, when the value falls below the lower limit, there is a case where problems such as inferior reversibility of charge / discharge are usually caused because crystals are not developed.

In the present invention, the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

BET specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more, more preferably 0.2 m ² / g or more, still more preferably 0.3 m ² / g or more, and the upper limit is preferably ^{50 m} 2 / g or less, more preferably 40 m ² / g or less, and further preferably 30 m ² / g or less. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered. If the BET specific surface area is larger, the tap density is difficult to increase, and a problem may occur in applicability when forming the positive electrode active material layer.

In the present invention, the BET specific surface area is large after preliminarily drying the sample at 150 ° C. for 30 minutes under a nitrogen flow using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.). It is defined by a value measured by a nitrogen adsorption BET one-point method using a gas flow method using a nitrogen-helium mixed gas that is accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3.

When the lithium ion secondary battery of the present invention is used as a large-sized lithium ion secondary battery for a hybrid vehicle or a distributed power source, high output is required. Therefore, the positive electrode active material particles are mainly secondary particles. It is preferable that
The positive electrode active material particles preferably include 0.5 to 7.0% by volume of fine particles having an average secondary particle size of 40 μm or less and an average primary particle size of 1 μm or less. By containing fine particles having an average primary particle size of 1 μm or less, the contact area with the electrolytic solution is increased, and the diffusion of lithium ions between the electrode and the electrolytic solution can be further accelerated. Output performance can be improved.

As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for preparing a spherical or elliptical active material. For example, a transition metal source material is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring. And a spherical precursor is prepared and recovered, and dried as necessary. Then, a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ is added, and the active material is obtained by baking at a high temperature. .

For the production of the positive electrode, the positive electrode active material may be used alone, or two or more of the different compositions may be used in any combination or ratio. A preferable combination in this case is a combination of LiCoO ₂ and LiMn ₂ O ₄ such as LiNi _0.33 Co _0.33 Mn _0.33 O ₂ or a part of this Mn substituted with another transition metal or the like. Or a combination with LiCoO ₂ or a part of this Co substituted with another transition metal or the like.

The content of the positive electrode active material is preferably 50 to 99% by mass, more preferably 80 to 99% by mass of the positive electrode mixture, in view of high battery capacity. The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. Moreover, an upper limit becomes like this. Preferably it is 99 mass% or less, More preferably, it is 98 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

The positive electrode mixture preferably further contains a binder, a thickener, and a conductive material.
As the above-mentioned binder, any material can be used as long as it is a material that is safe with respect to the solvent and the electrolyte used in the production of the electrode. For example, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene , SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, NBR (Acrylonitrile-butadiene rubber), fluoro rubber, ethylene-propylene rubber, styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Tadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer Examples thereof include polymers, fluorinated polyvinylidene fluoride, tetrafluoroethylene / ethylene copolymers, and polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions). In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The content of the binder is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 1.5% by mass or more, as a ratio of the binder in the positive electrode active material layer. Usually, it is 80 mass% or less, Preferably it is 60 mass% or less, More preferably, it is 40 mass% or less, Most preferably, it is 10 mass% or less. When the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, battery capacity and conductivity may be reduced.

Examples of the thickener include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. 1 type may be used independently or 2 or more types may be used together by arbitrary combinations and a ratio.

The ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and usually 5% by mass or less, preferably 3%. It is in the range of not more than mass%, more preferably not more than 2 mass%. Below this range, applicability may be significantly reduced. If it exceeds, the ratio of the active material in the positive electrode active material layer may decrease, and there may be a problem that the capacity of the battery decreases and a problem that the resistance between the positive electrode active materials increases.

A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass in the positive electrode active material layer. % Or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.

As the solvent for forming the slurry, the positive electrode active material, the conductive material, the binder, and a solvent capable of dissolving or dispersing the thickener used as necessary may be used. There is no restriction, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.

Examples of the material for the positive electrode current collector include metals such as aluminum, titanium, tantalum, stainless steel, and nickel, or metal materials such as alloys thereof; carbon materials such as carbon cloth and carbon paper. Among these, a metal material, particularly aluminum or an alloy thereof is preferable.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. A thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. The thickness of the thin film is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.

Moreover, it is also preferable from the viewpoint of reducing the electrical contact resistance between the current collector and the positive electrode active material layer that the surface of the current collector is coated with a conductive additive. Examples of the conductive assistant include noble metals such as carbon, gold, platinum, and silver.

The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of the current collector) is 20 Is preferably 15 or less, most preferably 10 or less, and preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the positive electrode active material increases and the battery capacity may decrease.

The positive electrode may be manufactured by a conventional method. For example, the above-mentioned positive electrode active material is added with the above-mentioned binder, thickener, conductive material, solvent, etc. to form a slurry-like positive electrode mixture, which is applied to a current collector, dried and then pressed. A method of densification is mentioned.

The densification can be performed by a hand press, a roller press or the like. The density of the positive electrode active material layer is preferably 1.5 g / cm ³ or more, more preferably 2 g / cm ³ or more, still more preferably 2.2 g / cm ³ or more, and preferably 5 g / cm ³ or less. More preferably, it is 4.5 g / cm < ³ > or less, More preferably, it is the range of 4 g / cm < ³ > or less. If it exceeds this range, the permeability of the electrolyte solution to the vicinity of the current collector / active material interface decreases, and the charge / discharge characteristics particularly at a high current density decrease, and a high output may not be obtained. On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and a high output may not be obtained.

When using the electrolytic solution of the present invention, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of increasing the stability at high output and high temperature. Specifically, the sum of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more. The outer surface area of the battery outer case, in the case of a square shape with a bottom, is the total area calculated from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal. Say. In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.

The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material is preferably as a lower limit with respect to one side of the current collector. Is 10 μm or more, more preferably 20 μm or more, and preferably 500 μm or less, more preferably 450 μm or less.

Moreover, you may use what adhered the substance of the composition different from this to the surface of the said positive electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

<Negative electrode>
The negative electrode is composed of a negative electrode mixture containing a negative electrode active material and a current collector.

Examples of the negative electrode active material include carbonaceous materials capable of occluding and releasing lithium, such as organic pyrolysis products and artificial graphite and natural graphite under various pyrolysis conditions; occluding and releasing lithium such as tin oxide and silicon oxide. Possible metal oxide materials; lithium metal; various lithium alloys; lithium-containing metal composite oxide materials. These negative electrode active materials may be used in combination of two or more.

As a carbonaceous material capable of occluding and releasing lithium, artificial graphite or purified natural graphite produced by high-temperature treatment of graphitizable pitch obtained from various raw materials, or surface treatment with pitch or other organic substances on these graphites And carbonized material obtained by carbonizing natural graphite, artificial graphite, artificial carbonaceous material, and artificial graphite material at least once in the range of 400 to 3200 ° C., and a negative electrode active material layer. A carbonaceous material comprising at least two kinds of carbonaceous materials having different crystallinity and / or having an interface in contact with the different crystalline carbonaceous materials, and at least two kinds of different orientations of the negative electrode active material layer A carbonaceous material having an interface with which the carbonaceous material is in contact is more preferable because of a good balance between initial irreversible capacity and high current density charge / discharge characteristics. Moreover, these carbon materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The carbonaceous material obtained by heat treating the above-mentioned artificial carbonaceous material and artificial graphite material at least once in the range of 400 to 3200 ° C includes coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, and oxidation of these pitches. Treated, needle coke, pitch coke and partially carbonized carbon agents, furnace black, acetylene black, pyrolytic products of organic materials such as pitch-based carbon fibers, carbonizable organic materials and their carbides, or carbonizable And a solution obtained by dissolving an organic substance in a low-molecular organic solvent such as benzene, toluene, xylene, quinoline, and n-hexane, and carbides thereof.

As the metal material used as the negative electrode active material (excluding lithium-titanium composite oxide), if lithium can be occluded / released, simple lithium, simple metal and alloy forming lithium alloy, or oxidation thereof Any of compounds such as oxides, carbides, nitrides, silicides, sulfides or phosphides may be used, and there is no particular limitation. The single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements, more preferably aluminum, silicon and tin (hereinafter abbreviated as “specific metal elements”). ) Simple metals and alloys or compounds containing these atoms. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

As a negative electrode active material having at least one kind of atom selected from a specific metal element, a metal simple substance of any one specific metal element, an alloy composed of two or more specific metal elements, one type or two or more specific types Alloys comprising metal elements and one or more other metal elements, as well as compounds containing one or more specific metal elements, and oxides, carbides, nitrides and silicides of the compounds And composite compounds such as sulfides or phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

In addition, a compound in which these complex compounds are complexly bonded to several kinds of elements such as a simple metal, an alloy, or a nonmetallic element is also included. Specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. For example, in the case of tin, a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element may be used. it can.

Specifically, Si alone, SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₆ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiOv (0 <v ≦ 2), LiSiO or tin alone, SnSiO ₃ , LiSnO, Mg ₂ Sn , SnOw (0 <w ≦ 2).
In addition, a composite material containing Si or Sn as the first constituent element and the second and third constituent elements in addition thereto can be given. The second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, and zirconium. For example, the third constituent element is at least one of boron, carbon, aluminum, and phosphorus.
In particular, since a high battery capacity and excellent battery characteristics can be obtained, as the metal material, silicon or tin alone (which may contain a small amount of impurities), SiOv (0 <v ≦ 2), SnOw (0 ≦ w) ≦ 2), Si—Co—C composite material, Si—Ni—C composite material, Sn—Co—C composite material, and Sn—Ni—C composite material are preferable.

The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but a material containing titanium and lithium is preferable from the viewpoint of high current density charge / discharge characteristics, A lithium-containing composite metal oxide material containing titanium is more preferable, and a composite oxide of lithium and titanium (hereinafter abbreviated as “lithium titanium composite oxide”) is more preferable. That is, it is particularly preferable to use a lithium-titanium composite oxide having a spinel structure in a negative electrode active material for an electrolyte battery because the output resistance is greatly reduced.

The lithium titanium composite oxide has a general formula:
Li _x Ti _y M _z O ₄
[Wherein M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. ]
It is preferable that it is a compound represented by these.
Among the above compositions,
(I) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(Ii) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(Iii) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because of a good balance of battery performance.

Particularly preferred representative compositions of the above compounds are Li _4/3 Ti _5/3 O ₄ in (i), Li ₁ Ti ₂ O ₄ in (ii), and Li _4/5 Ti _11/5 O in (iii). ₄ . As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.

The negative electrode mixture preferably further contains a binder, a thickener, and a conductive material.

As said binder, the thing similar to the binder which can be used for a positive electrode mentioned above is mentioned. The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less. It is more preferably at most 10 mass%, further preferably at most 10 mass%, particularly preferably at most 8 mass%. When the ratio of the binder to the negative electrode active material exceeds the above range, the binder ratio in which the amount of the binder does not contribute to the battery capacity increases, and the battery capacity may be reduced. On the other hand, below the above range, the strength of the negative electrode may be reduced.

In particular, when the main component contains a rubbery polymer typified by SBR, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more. 0.6 mass% or more is more preferable, and is usually 5 mass% or less, preferably 3 mass% or less, and more preferably 2 mass% or less. When the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

As said thickener, the thing similar to the thickener which can be used for a positive electrode mentioned above is mentioned. The ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 5% by mass or less. 3 mass% or less is preferable and 2 mass% or less is more preferable. When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and the problem that the capacity | capacitance of a battery falls and the resistance between negative electrode active materials may increase.

Examples of the conductive material for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black.

As the solvent for forming the slurry, the negative electrode active material, the binder, and the thickener and conductive material used as necessary can be dissolved or dispersed as long as it is a solvent. There is no restriction, and either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.

Examples of the material for the negative electrode current collector include copper, nickel, and stainless steel. Of these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost.

The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and is usually 100 μm or less, preferably 50 μm or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be reduced too much, and conversely if it is too thin, handling may be difficult.

The negative electrode may be manufactured by a conventional method. For example, the above-described negative electrode material is added with the above-mentioned binder, thickener, conductive material, solvent, etc. to form a slurry, which is applied to a current collector, dried, pressed and densified. . In the case of using an alloy material, a method of forming the above-described thin film layer (negative electrode active material layer) containing the negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.

The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ or more. but more preferably, particularly preferably 1.3 g · ^{cm -3} or more, preferably 2.2 g · ^{cm -3} or less, more preferably 2.1 g · ^{cm -3} or less, 2.0 g · ^{cm -3} or less Further preferred is 1.9 g · cm ⁻³ or less. If the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles are destroyed, increasing the initial irreversible capacity, or the electrolyte solution near the current collector / negative electrode active material interface In some cases, high current density charge / discharge characteristics are deteriorated due to a decrease in permeability. On the other hand, if the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited. However, the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 μm or more, preferably 20 μm or more. More preferably, it is 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

Moreover, you may use what adhered the substance of the composition different from this to the surface of the said negative electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

<Separator>
The lithium ion secondary battery of the present invention preferably further includes a separator.
The material and shape of the separator are not particularly limited as long as they are stable to the electrolytic solution and excellent in liquid retention, and known ones can be used. Among them, a resin, glass fiber, inorganic material, etc., formed of a material that is stable with respect to the electrolytic solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. preferable.

As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. These materials, such as a polypropylene / polyethylene two-layer film and a polypropylene / polyethylene / polypropylene three-layer film, may be used alone or in combination of two or more in any combination and ratio. Especially, it is preferable that the said separator is the porous sheet | seat or nonwoven fabric etc. which use polyolefin, such as polyethylene and a polypropylene, from the point that the permeability of an electrolyte solution and a shutdown effect are favorable.

The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only battery performance such as rate characteristics may be lowered, but also the energy density of the entire electrolyte battery may be lowered.

Furthermore, when using a porous material such as a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.

On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Used.

As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above-mentioned independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

<Battery design>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

The current collecting structure is not particularly limited, but in order to more effectively realize the high current density charge / discharge characteristics by the electrolytic solution of the present invention, it is necessary to make the structure that reduces the resistance of the wiring part and the joint part. preferable. Thus, when internal resistance is reduced, the effect using the electrolyte solution of this invention is exhibited especially favorable.

In the case where the electrode group has the above laminated structure, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

The material of the outer case is not particularly limited as long as it is a material that is stable with respect to the electrolytic solution used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

In an exterior case using metals, the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

The shape of the lithium ion secondary battery of the present invention is arbitrary, and examples thereof include a cylindrical shape, a square shape, a laminate shape, a coin shape, and a large shape. In addition, the shape and structure of a positive electrode, a negative electrode, and a separator can be changed and used according to the shape of each battery.

Moreover, the module provided with the lithium ion secondary battery of this invention is also one of this invention.

The electric double layer capacitor may include a positive electrode, a negative electrode, and the electrolytic solution described above.
In the electric double layer capacitor, at least one of the positive electrode and the negative electrode is a polarizable electrode, and the following electrodes described in detail in JP-A-9-7896 can be used as the polarizable electrode and the nonpolarizable electrode.

The polarizable electrode mainly composed of activated carbon used in the present invention preferably contains a non-activated carbon having a large specific surface area and a conductive agent such as carbon black imparting electron conductivity. The polarizable electrode can be formed by various methods. For example, a polarizable electrode made of activated carbon and carbon black can be formed by mixing activated carbon powder, carbon black, and a phenolic resin, and firing and activating in an inert gas atmosphere and a water vapor atmosphere after press molding. Preferably, the polarizable electrode is joined to the current collector with a conductive adhesive or the like.

Alternatively, activated carbon powder, carbon black, and a binder can be kneaded in the presence of alcohol, formed into a sheet, and dried to form a polarizable electrode. For example, polytetrafluoroethylene is used as the binder. In addition, activated carbon powder, carbon black, binder and solvent are mixed to form a slurry, and this slurry is coated on the metal foil of the current collector and dried to obtain a polarizable electrode integrated with the current collector. it can.

An electric double layer capacitor may be formed by using a polarizable electrode mainly composed of activated carbon for both electrodes, but a configuration using a non-polarizable electrode on one side, for example, a positive electrode mainly composed of a battery active material such as a metal oxide, and activated carbon A structure combining a polarizable electrode negative electrode mainly composed of carbon, a negative electrode mainly composed of a carbon material capable of reversibly occluding and releasing lithium ions, or a negative electrode composed mainly of lithium metal or lithium alloy and activated carbon. A configuration combining a positive electrode with a polarity is also possible.

Further, carbonaceous materials such as carbon black, graphite, expanded graphite, porous carbon, carbon nanotube, carbon nanohorn, and ketjen black may be used instead of or in combination with activated carbon.

The non-polarizable electrode is preferably composed mainly of a carbon material capable of reversibly occluding and releasing lithium ions, and an electrode obtained by occluding lithium ions in this carbon material is used for the electrode. In this case, a lithium salt is used as the electrolyte. According to the electric double layer capacitor having this configuration, a higher withstand voltage exceeding 4 V can be obtained.

The solvent used for preparing the slurry in the preparation of the electrode is preferably a solvent that dissolves the binder. According to the type of the binder, N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, phthalate Dimethyl acid, ethanol, methanol, butanol or water is appropriately selected.

Examples of the activated carbon used for the polarizable electrode include phenol resin-based activated carbon, coconut-based activated carbon, and petroleum coke-based activated carbon. Among these, it is preferable to use petroleum coke activated carbon or phenol resin activated carbon in that a large capacity can be obtained. Activated carbon activation treatment methods include a steam activation treatment method, a molten KOH activation treatment method, and the like, and it is preferable to use activated carbon obtained by a molten KOH activation treatment method in terms of obtaining a larger capacity.

Preferred conductive agents used for the polarizable electrode include carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, metal fiber, conductive titanium oxide, and ruthenium oxide. The mixing amount of the conductive agent such as carbon black used for the polarizable electrode is so that good conductivity (low internal resistance) is obtained, and if it is too much, the product capacity is reduced. It is preferable to set it as 50 mass%.

Moreover, as the activated carbon used for the polarizable electrode, activated carbon having an average particle size of 20 μm or less and a specific surface area of 1500 to 3000 m ² / g is used so as to obtain a large capacity and low internal resistance electric double layer capacitor. Is preferred. Further, as a preferable carbon material for constituting an electrode mainly composed of a carbon material capable of reversibly inserting and extracting lithium ions, natural graphite, artificial graphite, graphitized mesocarbon spherule, graphitized whisker, gas layer Examples thereof include a grown carbon fiber, a fired product of furfuryl alcohol resin, and a fired product of novolac resin.

The current collector is only required to be chemically and electrochemically corrosion resistant. As the current collector of the polarizable electrode mainly composed of activated carbon, stainless steel, aluminum, titanium or tantalum can be preferably used. Of these, stainless steel or aluminum is a particularly preferable material in terms of both characteristics and cost of the obtained electric double layer capacitor. As the current collector of the electrode mainly composed of a carbon material capable of reversibly inserting and extracting lithium ions, stainless steel, copper or nickel is preferably used.

In addition, in order to preliminarily store lithium ions in a carbon material capable of reversibly inserting and extracting lithium ions, (1) mixing powdered lithium with a carbon material capable of reversibly inserting and extracting lithium ions. (2) A lithium foil is placed on an electrode formed of a carbon material capable of reversibly occluding and releasing lithium ions and a binder, and the electrode is in contact with the lithium salt. A method in which lithium is ionized by immersing it in an electrolyte solution in which lithium is ionized and lithium ions are taken into the carbon material; (3) formed by a carbon material and a binder capable of reversibly inserting and extracting lithium ions; Place the electrode on the negative side, place lithium metal on the positive side, immerse it in a non-aqueous electrolyte containing lithium salt as an electrolyte, and pass an electric current to make an electrochemical carbon material A method of incorporating in a state in which lithium has been ionized.

As the electric double layer capacitor, a wound type electric double layer capacitor, a laminate type electric double layer capacitor, a coin type electric double layer capacitor and the like are generally known, and the electric double layer capacitor can also be in these types. .

For example, in a wound electric double layer capacitor, a positive electrode and a negative electrode made of a laminate (electrode) of a current collector and an electrode layer are wound through a separator to produce a wound element, and the wound element is made of aluminum. And then filled with an electrolytic solution, preferably a non-aqueous electrolytic solution, and then sealed and sealed with a rubber sealing body.

As the separator, conventionally known materials and structures can be used. For example, a polyethylene porous membrane, polypropylene fiber, glass fiber, cellulose fiber non-woven fabric and the like can be mentioned.

In addition, by a known method, a laminate type electric double layer capacitor in which a sheet-like positive electrode and a negative electrode are laminated via an electrolytic solution and a separator, and a positive electrode and a negative electrode are formed into a coin shape by fixing with a gasket and the electrolytic solution and the separator. A configured coin type electric double layer capacitor can also be used.

The electrolytic solution of the present invention is useful as an electrolytic solution for a large-sized lithium ion secondary battery for a hybrid vehicle or a distributed power source, or an electric double layer capacitor.

Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited only to this example.

Examples 1 to 59, Comparative Examples 1 to 24
(Preparation of electrolyte)
So that the composition shown in Table components were mixed, to this was added LiPF ₆ at a concentration of 1.0 mol / liter, thereby preparing an electrolytic solution.
The compounds in the table are as follows.

(FA1) Fluorinated saturated cyclic carbonate:

(FA2) Fluorinated chain carbonate:

(A1) Non-fluorinated saturated cyclic carbonate:
A1-1 Ethylene carbonate A1-2 Propylene carbonate A1-3 Butylene carbonate

(A2) Non-fluorinated chain carbonate:
A2-1 Ethyl methyl carbonate A2-2 Diethyl carbonate A2-3 Dimethyl carbonate

Compound (X): Cyclic dicarbonyl compound

Using the obtained electrolytic solution, a lithium ion secondary battery was produced by the following method.

(Preparation of positive electrode)
LiNi _0.5 Mn _1.5 O ₄ as a positive electrode active material, acetylene black as a conductive material, polyvinylidene fluoride (PVdF) N-methyl-2-pyrrolidone dispersion as a binder, an active material, a conductive material, A positive electrode mixture slurry was prepared such that the solid content ratio of the binder was 92/3/5 (mass% ratio). The obtained positive electrode mixture slurry was uniformly applied onto an aluminum foil current collector having a thickness of 20 μm, dried, and then compression molded by a press to obtain a positive electrode.

(Preparation of negative electrode)
Artificial graphite powder as negative electrode active material, aqueous dispersion of sodium carboxymethylcellulose as a thickener (concentration of 1% by weight of sodium carboxymethylcellulose), aqueous dispersion of styrene-butadiene rubber as binder (concentration of styrene-butadiene rubber 50) Mass%) and mixing in an aqueous solvent at a solid content ratio of the active material, thickener and binder of 97.6 / 1.2 / 1.2 (mass% ratio) to form a slurry. A negative electrode mixture slurry was prepared. After uniformly applying and drying on a copper foil having a thickness of 20 μm, it was compression-molded by a press to obtain a negative electrode.

(Production of lithium ion secondary battery)
The negative electrode, the positive electrode, and the polyethylene separator manufactured as described above were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element.
The battery element was inserted into a bag made of a laminate film in which both surfaces of an aluminum sheet (thickness: 40 μm) were coated with a resin layer while projecting positive and negative terminals, and then the electrolytes of Examples and Comparative Examples were used. Each was poured into a bag and vacuum sealed to produce a sheet-like lithium ion secondary battery.

<High temperature storage characteristics evaluation test>
Constant current-constant voltage charging (hereinafter referred to as CC / CV charging) up to 4.9 V with a current corresponding to 0.5 C at 25 ° C. in a state where the secondary battery produced above is sandwiched between plates and pressurized. .) (0.1 C cut), and then discharged to 3 V at a constant current of 0.5 C. This was taken as one cycle, and the initial discharge capacity was determined from the discharge capacity at the third cycle. Here, 1C represents a current value for discharging the reference capacity of the battery in one hour, and for example, 0.5C represents a half current value. After performing CC / CV charge (0.1C cut) to 4.9V again, high temperature storage was performed under conditions of 60 ° C. and 480 hours. When the battery after storage is discharged to 3 V at 0.5 C at 25 ° C., then charged again to CC and CV (0.1 C cut) to 4.9 V at 0.5 C, and then discharged to 3.0 V Was taken as the recovery capacity.
The recovery capacity after high-temperature storage was measured, the ratio of the recovery capacity to the initial discharge capacity was determined, and this was defined as the recovery capacity ratio (%).
(Recovery capacity) / (Initial discharge capacity) × 100 = Recovery capacity ratio (%)

<Resistance increase after storage test>
A charge / discharge cycle performed under predetermined charge / discharge conditions (charging at 0.5 C at a predetermined voltage until the charging current reaches 0.1 C and discharging to 3.0 V at a current equivalent to 1 C) is defined as 3 cycles. The subsequent resistance was used as the initial resistance, and the resistance after the high-temperature storage test was measured. The measurement temperature was 25 ° C. Based on the following formula, the resistance increase rate after the storage test was determined. The high-temperature storage test refers to charging to 4.9 V after 3 cycles of charge / discharge, and then storing at 60 ° C. for 480 hours.
Resistance increase rate of resistance after high temperature storage test (%) = resistance after high temperature storage test (Ω) / 3 resistance after 3 cycles (Ω) × 100
The results are shown in Tables 1-3.

Claims (6)

At least selected from the group consisting of amine (1) represented by general formula (1), amide (2) represented by general formula (2), and dialkyl oxalate (3) represented by general formula (3) With one kind,
And at least one cyclic dicarbonyl compound selected from the group consisting of compound (4) represented by general formula (4) and compound (5) represented by general formula (5),
The electrolytic solution, wherein the cyclic dicarbonyl compound is 0.001 to 10% by mass with respect to the electrolytic solution.
General formula (1):

(In the formula, R ¹¹ and R ¹² may be the same or different, the alkyl group having 1 to 7 carbon atoms, and Rf ¹³ is a fluorinated alkyl group having 1 to 7 carbon atoms).
General formula (2):

(In the formula, R ²¹ and R ²² may be the same or different, and an alkyl group having 1 to 7 carbon atoms, R ²³ is an alkyl group having 1 to 7 carbon atoms or a fluorinated alkyl group having 1 to 7 carbon atoms).
General formula (3):

(In the formula, R ³¹ and R ³² may be the same or different and have 1 to 7 carbon atoms)
General formula (4):

(A ^{a +} is a metal ion, hydrogen ion or onium ion. A is an integer of 1 to 3, b is an integer of 1 to 3, p is b / a, n ⁴³ is an integer of 1 to 4, n ⁴¹ is 0 to 8 , N ⁴² is 0 or 1, Z ⁴¹ is a transition metal, a group III, IV or V element of the periodic table.
X ⁴¹ is O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (alkylene group). , a halogenated alkylene group, an arylene group, and halogenated arylene group substituent in its structure, may have a hetero atom, and n ⁴² is ⁴³ pieces of n when n ⁴³ at 1 is 2 to 4 X ⁴¹ may be bonded to each other)
L ⁴¹ is a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogenated aryl group having 6 to 20 carbon atoms ( The alkylene group, halogenated alkylene group, arylene group, and halogenated arylene group may have a substituent or a hetero atom in the structure. When n ⁴¹ is 2 to 8, n ⁴¹ L ⁴¹ is each may be combined with each other to form a ring) or ^-Z 43 ^{Y 43.}
Y ⁴¹ , Y ⁴² and Z ⁴³ are each independently O, S, NY ⁴⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ⁴³ and Y ⁴⁴ are each independently H, F, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a halogen having 6 to 20 carbon atoms. Aryl group (an alkyl group, a halogenated alkyl group, an aryl group and a halogenated aryl group may have a substituent or a hetero atom in the structure thereof, and when there are a plurality of Y ⁴³ or Y ^44, May combine to form a ring)))
General formula (5):

(In the formula, n ⁵¹ is 0 or 1, n ⁵² is 0 or 1, Z ⁵¹ is a transition metal, a group III, group IV or group V element of the periodic table.
X ⁵¹ represents O, S, an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 20 carbon atoms, or a halogenated arylene group having 6 to 20 carbon atoms (alkylene group). , A halogenated alkylene group, an arylene group, and a halogenated arylene group may have a substituent or a hetero atom in the structure thereof.
Y ⁵¹ and Y ⁵² are each independently O, S, NY ⁵⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ⁵⁴ is H, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, a halogenated aryl group having 6 to 20 carbon atoms (an alkyl group, a halogenated group). The alkyl group, aryl group and halogenated aryl group may have a substituent or a hetero atom in the structure thereof, and when there are a plurality of Y ^{54 s} , they may be bonded to form a ring) ) The compound (α) contains at least one compound (α) selected from the group consisting of an amine (1) and an amide (2), and the content of the compound (α) is 0.001 to 20 ppm in the electrolytic solution. Electrolyte of description. The electrolytic solution according to claim 1 or 2, comprising a dialkyl oxalate (3), wherein the content of the dialkyl oxalate (3) is 0.001 to 10 ppm in the electrolytic solution. An electrochemical device comprising the electrolytic solution according to claim 1, 2 or 3. A lithium ion secondary battery comprising the electrolytic solution according to claim 1, 2 or 3. A module comprising the electrochemical device according to claim 4 or the lithium ion secondary battery according to claim 5.