JP2018106979A - Electrolyte, electrochemical device, lithium ion secondary battery, and module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte capable of corresponding to high voltage of an electrochemical device and improving cycle characteristics of the electrochemical device even at high voltage.SOLUTION: An electrolyte contains: a fluorinated lactone; and a metal salt having a specific structure, or the like. The fluorinated lactone is represented by general formula (1): [Chemical 1] (in the formula, X-Xeach independently represent H or F, but at least one of them is F).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 reduction in weight and size of electric products in recent years, development of lithium ion secondary batteries having high energy density has been promoted. In addition, as the field of application of lithium ion secondary batteries is expanded, there is a demand for improvement of battery characteristics. Especially in the future, when lithium ion secondary batteries are used for vehicles, battery characteristics become increasingly important.

Patent Document 1 discloses a negative electrode containing metal lithium, a lithium alloy or a material capable of absorbing and desorbing lithium, a positive electrode containing a material capable of absorbing and desorbing lithium, and a lithium salt in a non-aqueous solvent. And at least one hydrogen atom bonded to a carbon atom constituting a lactone ring in the non-aqueous solvent is substituted by a non-aqueous electrolyte secondary battery comprising at least an electrolytic solution obtained by dissolving A non-aqueous electrolyte secondary battery is described which contains a lactone compound in an amount of 0.01 to 10% by weight based on the weight of the electrolyte contained in the non-aqueous electrolyte secondary battery.

Patent Document 2 is a battery including an electrolyte together with a positive electrode and a negative electrode, wherein lithium metal is used as a negative electrode active material, and the electrolyte is a cyclic compound having a halogen atom as a solvent and a chain compound having a halogen atom. And a battery comprising the

Patent Document 3 discloses an electrolyte having a second cycle reduction current at 0.3 V against Li / Li ⁺ which is lower than the first cycle reduction current, and which does not passivate electrochemically. And an electrolyte containing at least one additive is preferably contained, and the additive is preferably carbonate, chloroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, sulfite, ethylene sulfite, propane sulfone, propylene. Sulfite, butyrolactone, phenylethylene carbonate, phenylvinylene carbonate, catechol carbonate, vinyl acetate, vinyl ethylene carbonate, dimethyl sulfite, fluoroethylene carbonate, trifluoropropylene carbonate DOO, it is described that comprises at least one member selected from the group consisting of bromo γ- butyrolactone, and fluoro γ- butyrolactone.

Patent Document 4 describes an electrolyte for a non-aqueous secondary battery containing an electrolyte and a phosphazene compound in an aprotic solvent, wherein 20% by volume to 90% by volume of the aprotic solvent is a carbonyl group and a halogen. An electrolyte for a non-aqueous secondary battery composed of a halogen-containing compound having an atom is described. The halogen-containing compound is preferably a compound represented by the following formula (H1) or (H2).

(Wherein, X ¹¹ , X ¹² , X ²¹ and X ²² independently represent CR ¹⁸ R ¹⁹ , an oxygen atom, NR ²⁰ or a sulfur atom. R ^{11 to} R ¹⁶ and R ^{21 to} R ²⁴ are independently R ^{18 to} R ²⁰ each independently represent a hydrogen atom, a halogen atom, an alkyl group or an aryl group Of R ^{11 to} R ¹⁶ , X ¹¹ and X ¹² At least one contains a halogen atom At least one of R ^{21 to} R ²⁴ , X ²¹ and X ²² contains a halogen atom na is an integer of 1 to 4. When na is 2 or more, R ²³ and R ²⁴ may be different from each other)

Unexamined-Japanese-Patent No. 2002-298912 JP, 2006-134834, A JP, 2006-202745, A JP, 2014-078433, A

In the case of applying an electrochemical device such as a lithium ion secondary battery to an application requiring a large capacity power source such as a vehicle, it is necessary to increase the voltage in order to achieve higher energy density. For this reason, there has been a demand for an electrolyte that is compatible with the increase in voltage and that can improve various characteristics of the electrochemical device.

The present invention has been made in view of the above-mentioned present situation, and can cope with high voltage of electrochemical devices, and can improve the cycle characteristics of electrochemical devices even with high voltage, and electricity excellent in cycle characteristics even with high voltage The purpose is to provide a chemical device.

The present invention is an electrolytic solution comprising a solvent and a compound (2), wherein the solvent is a compound represented by the general formula (1):

（式中、Ｘ^１１〜Ｘ^１６は、独立に、Ｈ又はＦ、但し、少なくとも一つはＦ）で示されるフッ素化ラクトン（１）を含み、化合物（２）は、一般式（２）：

(Wherein, X ^{11 to} X ^{16 each} independently represent a fluorinated lactone (1) represented by H or F, provided that at least one is F), and the compound (2) is a compound represented by the general formula (2):

(Wherein, 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 ²³ is an integer of 1 to 4, n ²¹ is 0-8 ^{integer, n 22} is 0 or ^{1, Z 21} is a transition metal, III of the periodic table, IV or group V element of.
X ²¹ 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 And the halogenated alkylene group, the arylene group and the halogenated arylene group may have a substituent or a hetero atom in the structure, and when n ²² is 1 and n ²³ is 2 to 4, n ²³ Each X ²¹ may be bonded)
L ²¹ represents 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 The alkylene group, the halogenated alkylene group, the arylene group, and the halogenated arylene group may have a substituent or a hetero atom in the structure, and when n ²¹ is 2 to 8, n ²¹ L ²¹ is Each may combine to form a ring) or -Z ²³ Y ²³ .
Y ²¹ , Y ²² and Z ²³ are each independently O, S, NY ²⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ²³ and Y ²⁴ 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 Arylated aryl group (the alkyl group, the halogenated alkyl group, the aryl group and the halogenated aryl group may have a substituent or a hetero atom in the structure, and when a plurality of Y ²³ or Y ²⁴ exist, Are bonded to form a ring))).

The solvent preferably contains 11% by volume or more of the fluorinated lactone (1).

The solvent preferably further contains at least one compound (a) selected from the group consisting of fluorinated carbonates and fluorinated chain esters.

The solvent contains 11 to 90% by volume of fluorinated lactone (1) and 10 to 89% by volume of the compound (a), and the electrolyte contains 0.01 to 10% by mass with respect to the solvent. It is preferable to include the compound (2) of

The above-mentioned solvent further has a general formula (4):

（式中、Ｒ^４１及びＲ^４２は、独立に、Ｈ、ＣＨ_３、Ｆ、ＣＨ_２Ｆ、ＣＨＦ_２又はＣＦ_３、Ｒ^４３は炭素数１若しくは２の非フッ素化アルキル基又は炭素数１若しくは２のフッ素化アルキル基）で示されるフッ素化ジエーテル（４）、一般式（５）：

(Wherein, R ⁴¹ and R ⁴² are independently H, CH ₃ , F, CH ₂ F, CHF ₂ or CF ₃ , R ⁴³ is a C 1 or C 2 non-fluorinated alkyl group or C 1 or C 2 A fluorinated diether (4) represented by the fluorinated alkyl group of 2), the general formula (5):

（式中、Ｒｆ^５１は、独立に、Ｆ又は炭素数１若しくは２のフッ素化アルキル基、Ｒ^５１、Ｒ^５２及びＲ^５３は、独立に、Ｈ、Ｆ、炭素数１若しくは２の非フッ素化アルキル基又は炭素数１若しくは２のフッ素化アルキル基）で示されるフッ素化ジエーテル（５）、一般式（６）：

(Wherein, R f ⁵¹ is independently F or a fluorinated alkyl group having 1 or 2 carbon atoms, R ⁵¹ , R ⁵² and R ⁵³ are independently H, F, 1 or 2 carbon atoms and non-fluorinated A fluorinated diether (5) represented by an alkyl group or a fluorinated alkyl group having 1 or 2 carbon atoms, a compound represented by the general formula (6):

（式中、Ｒ^６１は、炭素数１若しくは２の非フッ素化アルキル基、又は、炭素数１若しくは２のフッ素化アルキル基）で示されるフッ素化鎖状カーボネート（６）、及び、一般式（７）：

(Wherein, R ⁶¹ represents a non-fluorinated alkyl group having 1 or 2 carbon atoms, or a fluorinated alkyl group having 1 or 2 carbon atoms) fluorinated linear carbonate (6), and a compound represented by the general formula ( 7):

（式中、Ｒ^７１は、炭素数１若しくは２の非フッ素化アルキル基、又は、炭素数１若しくは２のフッ素化アルキル基）で示されるフッ素化鎖状カーボネート（７）からなる群より選択される少なくとも１種の化合物（ｂ）を含むことが好ましい。

(Wherein, R ⁷¹ is selected from the group consisting of fluorinated linear carbonates (7) represented by a C 1 or C 2 non-fluorinated alkyl group, or a C 1 or 2 C fluorinated alkyl group) It is preferred to include at least one compound (b).

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

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

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

According to the electrolytic solution of the present invention, the cycle characteristics of the electrochemical device can be improved even at high voltage.
The electrochemical device provided with the above-mentioned electrolytic solution has excellent cycle characteristics even at high voltage.

Hereinafter, the present invention will be specifically described.

（式中、Ｘ^１１〜Ｘ^１６は、独立に、Ｈ又はＦ、但し、少なくとも一つはＦ）で示されるフッ素化ラクトン（１）を含む。 The electrolytic solution of the present invention contains a solvent, and the solvent has the general formula (1):

(Wherein, X ^{11 to} X ^{16 each} independently represent H or F, provided that at least one of them is F).

のいずれかが好ましい。フッ素化ラクトン（１）として、１種又は２種以上を使用できる。 As fluorinated lactone (1),

Is preferred. As fluorinated lactone (1), 1 type or 2 types or more can be used.

In the electrolytic solution of the present invention, the solvent preferably contains 11% by volume or more of the fluorinated lactone (1) with respect to the solvent, since further excellent cycle characteristics can be obtained. As content of fluorinated lactone (1), 20 volume% or more is more preferable, 30 volume% or more is still more preferable, 80 volume% or less is preferable, and 70 volume% or less is more preferable.

The electrolytic solution of the present invention further contains a compound (2) represented by the general formula (2).

（式中、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^２３は１〜４の整数、ｎ^２１は０〜８の整数、ｎ^２２は０又は１、Ｚ^２１は遷移金属、周期律表のＩＩＩ族、ＩＶ族又はＶ族の元素。
Ｘ^２１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^２２が１でｎ^２３が２〜４のときにはｎ^２３個のＸ^２１はそれぞれが結合していてもよい）
Ｌ^２１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^２１が２〜８のときにはｎ^２１個のＬ^２１はそれぞれが結合して環を形成してもよい）又は−Ｚ^２３Ｙ^２３。
Ｙ^２１、Ｙ^２２及びＺ^２３は、それぞれ独立でＯ、Ｓ、ＮＹ^２４、炭化水素基又はフッ素化炭化水素基。Ｙ^２３及びＹ^２４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^２３又はＹ^２４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 (2):

(Wherein, 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 ²³ is an integer of 1 to 4, n ²¹ is 0-8 ^{integer, n 22} is 0 or ^{1, Z 21} is a transition metal, III of the periodic table, IV or group V element of.
X ²¹ 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 And the halogenated alkylene group, the arylene group and the halogenated arylene group may have a substituent or a hetero atom in the structure, and when n ²² is 1 and n ²³ is 2 to 4, n ²³ Each X ²¹ may be bonded)
L ²¹ represents 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 The alkylene group, the halogenated alkylene group, the arylene group, and the halogenated arylene group may have a substituent or a hetero atom in the structure, and when n ²¹ is 2 to 8, n ²¹ L ²¹ is Each may combine to form a ring) or -Z ²³ Y ²³ .
Y ²¹ , Y ²² and Z ²³ are each independently O, S, NY ²⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ²³ and Y ²⁴ 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 Arylated aryl group (the alkyl group, the halogenated alkyl group, the aryl group and the halogenated aryl group may have a substituent or a hetero atom in the structure, and when a plurality of Y ²³ or Y ²⁴ exist, May combine to form a ring))

As A ^{a +} , 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, lanthanide ion, actinide ion, tetrabutyl ammonium ion, tetraethyl ammonium ion, tetramethyl ammonium ion, triethyl methyl ammonium ion, triethyl ammonium ion, pyridinium ion, imidazolium ion , Hydrogen ion, tetraethyl phosphonium ion, tetramethyl phosphonium ion, tetraphenyl phosphonium Ions, triphenylsulfonium ion, triethylsulfonium ion and the like.

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

Next, the ligand part of the general formula (2) will be described. In the present specification, the organic or inorganic moiety bonded to Z ²¹ in the general formula (2) is referred to as a ligand.

Z ²¹ is preferably Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf or Sb, and Al , B or P is more preferable.

X ²¹ 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 group and arylene group may have a substituent or a hetero atom in the structure. Specifically, instead of hydrogen on an alkylene group and an 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 It may have a group, an acyl group, an amido 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. When n ²² is 1 and n ²³ is 2 to 4, each of n ²³ X ^21s may be bonded. Such examples may include ligands such as ethylenediaminetetraacetic acid.

L ²¹ represents 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 ²³ Y ²³ (Z ²³ and Y ²³ will be described later). The alkyl group and the aryl group here may also have a substituent and a hetero atom in the structure, as in X ^21, and when n ²¹ is 2 to 8, each of n ²¹ L ²¹ is It may combine to form a ring. As L ²¹ , a fluorine atom or a cyano group is preferable. In the case of a fluorine atom, the solubility and the degree of dissociation of the salt of the anion compound are improved, and along with this, the ion conductivity is improved. Moreover, it is because oxidation resistance improves and generation | occurrence | production of a side reaction can be suppressed by this.

Y ²¹ , Y ²² and Z ²³ each independently represent O, S, NY ²⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ²¹ and Y ²² are preferably O, S or NY ²⁴ and more preferably O. As a feature of the compound (2), since there is a bond to Z ²¹ with Y ²¹ and Y ²² in the same ligand, these ligands form a chelate structure with Z ²¹ . The heat resistance, chemical stability and hydrolysis resistance of this compound are improved by the effect of this chelate. The constant n ^{22 in} this ligand is 0 or 1, but in the case of 0, in particular, the chelating effect is a five-membered ring, so the chelating effect is most strongly exhibited and the stability is increased.
In the present specification, a fluorinated hydrocarbon group is a group in which at least one hydrogen atom of a hydrocarbon group is substituted by a fluorine atom.

Y ²³ and Y ²⁴ 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 6 to 20 carbon atoms It is a halogenated aryl group, and these alkyl group and aryl group may have a substituent or a hetero atom in the structure, and when two or more Y ²³ or Y ²⁴ exist, each is bonded To form a ring.

The constant n ²³ 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 ²¹ related to the number of ligands described above is an integer of 0 to 8, preferably an integer of 0 to 4, and more preferably 0, 2 or 4. Furthermore, it is preferable that n ²¹ be 2 when n ²³ is 1 and n ²¹ be 0 when n ²³ is 2.

In the general formula (2), the alkyl group, the halogenated alkyl group, the aryl group and the halogenated aryl group also include those having other functional groups such as a branch, a hydroxyl group and an ether bond.

As the compound (2), a compound represented by the general formula:

（式中、Ａ^ａ＋、ａ、ｂ、ｐ、ｎ^２１、Ｚ^２１及びＬ^２１は上述したとおり）で示される化合物、又は、一般式：

(Wherein, A ^{a +} , a, b, p, n ²¹ , Z ²¹ and L ²¹ are as described above) or a compound represented by the general formula:

（式中、Ａ^ａ＋、ａ、ｂ、ｐ、ｎ^２１、Ｚ^２１及びＬ^２１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。

(Wherein, A ^{a +} , a, b, p, n ²¹ , Z ²¹ and L ²¹ are as described above) is preferable.

As a compound (2), lithium oxalato borate salt is mentioned and following formula:

で示されるリチウムビス（オキサラト）ボレート（ＬＩＢＯＢ）、下記式：

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

で示されるリチウムジフルオロオキサラトボレート（ＬＩＤＦＯＢ）、下記式：

Lithium difluoro oxalato borate (LIDFOB) represented by the following formula:

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。

And lithium dicyano oxalato borate, etc.

As the compound (2), also, the following formula:

で示されるリチウムジフルオロオキサラトホスファナイト（ＬＩＤＦＯＰ）、下記式：

Lithium difluoro oxalato phosphanite (LIDFOP) represented by the following 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（ＬＩＴＦＯＰ）、下記式：

Lithium tetrafluoro oxalato phosphanite (LITFOP) represented by the following formula:

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。

And lithium bis (oxalato) difluorophosphanite and the like.

The content of the compound (2) is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and 10% by mass, with respect to the solvent, since further excellent cycle characteristics can be obtained. % Or less is preferable and 5 mass% or less is more preferable.

Since the electrolytic solution of the present invention further achieves superior cycle characteristics, the solvent is further selected from the group consisting of fluorinated carbonate and fluorinated chain ester (a) Is preferred. Moreover, it is also preferable to contain a fluorinated cyclic carbonate and a fluorinated linear carbonate as the compound (a), and it is also preferable to include only a fluorinated linear carbonate, and a fluorinated cyclic carbonate, a fluorinated linear carbonate and a fluorinated chain It is also preferred to include a cyclic ester.

When the solvent contains the compound (a), the solvent contains 11 to 90% by volume of the fluorinated lactone (1) and 10 to 89% by volume of the compound (a), and the electrolyte contains the solvent It is preferable that 0.01-10 mass% of compounds (2) are included with respect to.

When the solvent contains the compound (a), the solvent contains 20 to 70% by volume of the fluorinated lactone (1) and 30 to 80% by volume of the compound (a), and the electrolyte contains the solvent More preferably, it contains 0.01 to 5% by mass of the compound (2).

The fluorinated carbonate is preferably at least one selected from the group consisting of a fluorinated saturated cyclic carbonate and a fluorinated linear carbonate.

The fluorinated saturated cyclic carbonate is a saturated cyclic carbonate to which a fluorine atom is added, and 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、−Ｃ_２Ｈ_５、−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。

(Wherein, X ^{1 to} X ⁴ are the same or different and each is —H, —CH ₃ , —C ₂ H ₅ , —F, a fluorinated alkyl group which may have an ether bond, or an ether bond A fluorinated alkoxy group which may be substituted, provided that at least one of X ^{1 to} X ⁴ is —F, a fluorinated alkyl group which may have an ether bond, or an ether bond; And a compound represented by the above formula) is a good fluorinated alkoxy group.
When the above-mentioned fluorinated saturated cyclic carbonate is contained, a stable film can be formed on the negative electrode when the electrolytic solution of the present invention is applied to a lithium ion secondary battery etc., and the side reaction of the electrolytic solution on 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, "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 which may have an ether bond, or an ether bond It is preferable that it is a fluorinated alkoxy group.

From the fact that the viscosity decrease at low temperature, the increase in flash point, and the improvement of the solubility of the electrolyte salt can be expected, X ^{1 to} X ⁴ are -H, -F, fluorinated alkyl group (a), ether bond It is preferable that it is a fluorinated alkyl group (b) or a fluorinated alkoxy group (c).

The said fluorinated alkyl group (a) is what substituted at least 1 of the hydrogen atom which an alkyl group has with a fluorine atom. 1-20 are preferable, as for carbon number of a fluorinated alkyl group (a), 1-17 are more preferable, 1-7 are still more preferable, and 1-5 are especially preferable.
If the number of carbons is too large, the low temperature characteristics may deteriorate or the solubility of the electrolyte salt may decrease. If the number of carbons is too small, the solubility of the electrolyte salt may decrease, the discharge efficiency may decrease, and further An increase in viscosity etc. may be observed.

Among the above-mentioned fluorinated alkyl groups (a), examples of one having 1 carbon atom include CFH ₂ −, CF ₂ H −, and CF ₃ −. In particular, CF ₂ H- or CF ₃ -is preferable in terms of high temperature storage characteristics.

Among the above-mentioned fluorinated alkyl groups (a), those having two or more carbon atoms include those represented by 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; however, R ¹ and The fluorinated alkyl group represented by at least one of R ^{2 s} having 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 than carbon atoms, hydrogen atoms and fluorine atoms.

R ¹ is an alkyl group having one or more carbon atoms which may have a fluorine atom. As R ¹ , a linear or branched alkyl group having ^{1 to} 16 carbon atoms is preferable. 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.

Moreover, 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 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 Can be mentioned.

Moreover, when R ¹ is a branched alkyl group having a fluorine atom,

Etc. are preferably mentioned. However, since the viscosity is likely to be high if it has a branch such as CH ₃ -or CF _3- , the number thereof is more 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 which comprises 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 exemplifications, it is preferable to be composed of a structural unit not containing Cl, because deHCl reaction with a base does not occur and it is more stable.

When R ² is linear, it consists only of the above-described linear minimum structural unit, and in particular, —CH ₂ —, —CH ₂ CH ₂ — or —CF ₂ — is preferable. -CH ₂ -or -CH ₂ CH ₂ -is more preferable from the viewpoint that the solubility of the electrolyte salt can be further improved.

When R ² is branched, it contains at least one of the branched minimum structural units described above, and has a general formula of-(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 one represented by H or CH ₃₎ it can be preferably exemplified. In particular, these can further improve the solubility of the electrolyte salt.

Preferred fluorinated alkyl group (a), for example _{CF 3 CF 2 -, HCF 2} CF 2 -, H 2 CFCF 2 -, CH 3 CF 2 -, CF 3 CHF-, CH 3 CF 2 -, CF 3 CF _{2 CF 2 -, 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 one in which at least one of the hydrogen atoms of the alkyl group having an ether bond is substituted 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 becomes high, and the number of fluorine-containing groups increases. Therefore, the solubility of the electrolyte salt is reduced due to the reduction of the dielectric constant, and the compatibility with other solvents May be seen. As for carbon number of the fluorinated alkyl group (b) which has the said ether bond from this viewpoint, 2-10 are more preferable, and 2-7 are still more preferable.

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. Examples of the minimum structural unit constituting such a linear or branched alkylene group are 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 linear (i), branched (ii) or linear (i) and branched (ii) It may be configured by a combination. Preferred specific examples will be described later.

In addition, among the above exemplifications, it is preferable to be composed of a structural unit not containing Cl, because deHCl reaction with a base does not occur and it is more stable.

Further preferable examples of the fluorinated alkyl group (b) having an ether bond include a group represented by the general formula (b-1):
R ^3- (OR ⁴ ) _n 1-(b-1)
(Wherein, 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 an alkylene having 1 to 4 carbon atoms And 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, which can be combined as appropriate to form a fluorinated alkyl group (b) having an ether bond represented by the above general formula (b-1). Not limited to these.

(1) As R ³ , a general formula: X ^c ₃ C- (R ⁵ ) n _2- (wherein three X ^c are the same or different and each is H or F; R ⁵ is a C 1-5 fluorine atom Alkylene group which may be possessed; 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-.

As a specific example when n2 is 1, as 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 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.

When n2 is 1 and R ³ is a branched chain,

Etc.

However, since it is easy to increase the viscosity if it has a branch such as CH ₃ -or CF _3- , it is more preferable that R ³ be linear.

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

As preferable specific examples of R ⁴ , the following linear or branched ones can be exemplified.

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.

As branched ones,

Etc.

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

The fluorinated alkoxy group (c) may be represented by the general formula: X ^d ₃ C- (R ⁶ ) _{n 3} -O- (wherein three X ^d are the same or different H or F; R ⁶ is preferably carbon number Particularly preferred is a fluorinated alkoxy group represented by an alkylene group which may have 1 to 5 fluorine atoms; n3 is 0 or 1; provided that any of three X ^d contains a fluorine atom.

Specific examples of the fluorinated alkoxy group (c), a fluorinated alkoxy group terminal oxygen atom is bonded to an alkyl group exemplified as R ¹ in formula (a-1) can be mentioned.

The fluorine content of the fluorinated alkyl group (a) in the fluorinated saturated cyclic carbonate, the fluorinated alkyl group (b) having an ether bond, and the fluorinated alkoxy group (c) is preferably 10% by mass or more. If the fluorine content is too low, the viscosity lowering effect at low temperatures and the flash point raising effect may not be sufficiently obtained. From this viewpoint, the fluorine content is more preferably 12% by mass or more, and still more 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 {(number of fluorine atoms based on the structural formula of each group It is the value computed by x19) / formula weight of each group} x 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 determined by {(number of fluorine atoms × 19) / molecular weight of fluorinated saturated cyclic carbonate} × 100 (%) based on the structural formula of 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 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 the fluorinated saturated cyclic carbonate in which at least one of X ^{1 to} X ⁴ is a fluorinated alkyl group (b) having an ether bond or a fluorinated alkoxy group (c) 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, the fluorinated saturated cyclic carbonate is more preferably fluoroethylene carbonate, difluoroethylene carbonate or trifluoromethylethylene carbonate.

In addition, said fluorinated saturated cyclic carbonate is not limited only to the specific example mentioned 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.

As said fluorinated linear carbonate, general formula (B):
Rf ² OCOOR ⁶ (B)
(Wherein, R f ² is a fluorinated alkyl group of 1 to 7 carbon atoms, and R ⁶ is an alkyl group of 1 to 7 carbon atoms which may contain a fluorine atom) It can be mentioned.

The electrolytic solution of the present invention preferably contains the above-mentioned fluorinated linear carbonate in that it can be suitably used even under high voltage.

Rf ² is a fluorinated alkyl group having 1 to 7 carbon atoms, and R ⁶ is an alkyl group which may contain a fluorine atom having 1 to 7 carbon atoms.
The said fluorinated alkyl group substitutes at least one of the hydrogen atoms which an alkyl group has with a fluorine atom. When R ⁶ is an alkyl group containing a fluorine atom, it is a fluorinated alkyl group.
The Rf ² and R ⁶ preferably have 2 to 7 carbon atoms, and more preferably 2 to 4 carbon atoms, in terms of low viscosity.
If the number of carbons is too large, the low temperature characteristics may deteriorate or the solubility of the electrolyte salt may decrease. If the number of carbons is too small, the solubility of the electrolyte salt may decrease, the discharge efficiency may decrease, and further An increase in viscosity etc. may be observed.

Examples of the fluorinated alkyl group having 1 carbon atom include CFH ₂ −, CF ₂ H −, CF ₃ − and the like. In particular, CF ₂ H- or CF ₃ -is preferable in terms of high temperature storage characteristics.

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; however, R ¹ and The fluorinated alkyl group represented by at least one of R ^{2 s} having 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 than carbon atoms, hydrogen atoms and fluorine atoms.

R ¹ is an alkyl group having one or more carbon atoms which may have a fluorine atom. The R ^1, 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.

Moreover, 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 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 Can be mentioned.

Moreover, when R ¹ is a branched alkyl group having a fluorine atom,

Etc. are preferably mentioned. However, since the viscosity is likely to be high if it has a branch such as CH ₃ -or CF _3- , the number thereof is more 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 which comprises 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 exemplifications, it is preferable to be composed of a structural unit not containing Cl, because deHCl reaction with a base does not occur and it is more stable.

When R ² is linear, it consists only of the above-described linear minimum structural unit, and in particular, —CH ₂ —, —CH ₂ CH ₂ — or —CF ₂ — is preferable. -CH ₂ -or -CH ₂ CH ₂ -is more preferable from the viewpoint that the solubility of the electrolyte salt can be further improved.

When R ² is branched, it contains at least one of the branched minimum structural units described above, and has a general formula of-(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 one represented by H or CH ₃₎ it can be preferably exemplified. In particular, these can further improve the solubility of the electrolyte salt.

Specifically as a preferable fluorinated alkyl group, for example, CF ₃ CF _2- , HCF ₂ CF _2- , H ₂ CFCF _2- , CH ₃ CF _2- , CF ₃ CH _2- , CF ₃ CF ₂ CF _{2 -, HCF 2 CF 2 CF} 2 -, H 2 CFCF 2 CF 2 -, CH 3 CF 2 CF 2 -,

Etc.

Among them, as fluorinated alkyl groups 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 −, CF _{3 CF 2 CH 2 -, HCF 2} CF 2 CH 2 -, CF 3 CFHCF 2 CH 2 - are preferred, high flame retardancy, rate characteristic and oxidation-resistant viewpoint of _{satisfactory, 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 not containing a fluorine atom, it is an alkyl group having 1 to 7 carbon atoms. R ⁶ preferably has 1 to 4 carbon atoms, and more preferably 1 to 3 carbon atoms in view of low viscosity.

The alkyl group containing no above fluorine atom, for _{example, CH 3 -, CH 3 CH} 2 -, (CH 3) 2 CH-, C 3 H 7 - , and the like. Among them, CH ₃ -and CH ₃ CH ₂ -are preferable in terms of low viscosity and favorable 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-mentioned range, the compatibility with the solvent and the solubility of the salt can be maintained. 30 mass% or more is more preferable, 35 mass% or more is further more preferable, 60 mass% or less is more preferable, and 50 mass% or less is still more preferable.
In the present invention, the fluorine content is based on the structural formula of the above-mentioned fluorinated linear carbonate,
{(Number of fluorine atoms × 19) / molecular weight of fluorinated linear carbonate} × 100 (%)
Is a value calculated by

The fluorinated linear carbonate is preferably any of the following compounds in view of low viscosity.

As said fluorinated chain ester, general formula (3):
Rf ³¹ COORf ³²
(Wherein, R f ³¹ is a fluorinated alkyl group having 1 to 4 carbon atoms, and R f ³² is an alkyl group optionally containing a fluorine atom having 1 to 4 carbon atoms) From the viewpoint of good compatibility with these compounds and oxidation resistance.

Examples of Rf ³¹ include HCF _2- , CF _3- , CF ₃ CF _2- , HCF ₂ CF _2- , CH ₃ CF _2- , CF ₃ CH _2- and the like, and among them, HCF _2- , CF _3- -, CF ₃ CF _2- , and CF ₃ CH ₂ -are particularly preferable from the viewpoint of good viscosity and oxidation resistance.

The Rf ^32, for _{example, CH 3 -, C 2 H} 5 -, 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 - Among them, CH _3- , C ₂ H _5- , CF ₃ CH _2- , and CF ₃ CH ₂ CH ₂ -are particularly preferable, from the viewpoint of good compatibility with other solvents.

Specific examples of the fluorinated chain ester include CF ₃ CH ₂ C (= O) OCH ₃ , HCF ₂ C (= O) OCH ₃ , CF ₃ C (= O) OCH ₂ CH ₂ CF ₃ , 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 ) 1 type or 2 types such as ₂ can be exemplified, and among them, CF ₃ CH ₂ C (= O) OCH ₃ , HCF ₂ C (= O) OCH ₃ , 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 is the phase with other solvents Particularly preferred in view of good solubility and rate characteristics.

It is also preferable that the above-mentioned solvent contains non-fluorinated carbonate, since excellent ion conductivity and compatibility are obtained.

The non-fluorinated carbonate is preferably at least one selected from the group consisting of non-fluorinated saturated cyclic carbonate and non-fluorinated linear carbonate, and more preferably non-fluorinated saturated cyclic carbonate.

When the solvent contains the non-fluorinated carbonate, the solvent contains 11 to 80% by volume of fluorinated lactone (1) and 20 to 89% by volume of the non-fluorinated carbonate, and the electrolyte contains It is preferable that 0.01-10 mass% of compounds (2) are included with respect to the said solvent.

When the solvent contains the non-fluorinated carbonate, the solvent contains 20 to 70% by volume of a fluorinated chain lactone (1) and 30 to 80% by volume of the non-fluorinated carbonate; It is preferable that 0.01-5 mass% of compounds (2) are included with respect to the said solvent.

The above non-fluorinated carbonates are also preferably used in combination with the compound (a) because further superior cycle characteristics can be obtained.

When the solvent contains the non-fluorinated carbonate and the compound (a), the solvent is 11 to 80% by volume of fluorinated lactone (1), 10 to 80% by volume of the compound (a), and 5 to 50 The non-fluorinated carbonate is preferably contained by volume, and the electrolyte preferably contains 0.01 to 10% by mass of the compound (2) with respect to the solvent.

When the solvent contains the non-fluorinated carbonate and the compound (a), the solvent contains 20 to 70% by volume of the fluorinated lactone (1), 20 to 70% by volume of the compound (a), and 10 to 30 The non-fluorinated carbonate is preferably contained by volume, and the electrolyte preferably contains 0.01 to 5% by mass of the compound (2) with respect to the solvent.

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

Among them, the above 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. Is preferred.
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.

Examples of the non-fluorinated linear carbonates 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) And hydrocarbon-based chain carbonates such as CH ₃ OCOOCH ₂ CH ₂ CH ₃ (methyl propyl carbonate), methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate and the like. Among them, at least one selected from the group consisting of ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate is preferable.

In the electrolytic solution of the present invention, the solvent is further selected from the group consisting of fluorinated diether (4), fluorinated diether (5), fluorinated linear carbonate (6) and fluorinated linear carbonate (7) And at least one compound (b).

（式中、Ｒ^４１及びＲ^４２は、独立に、Ｈ、ＣＨ_３、Ｆ、ＣＨ_２Ｆ、ＣＨＦ_２又はＣＦ_３、Ｒ^４３は炭素数１若しくは２の非フッ素化アルキル基又は炭素数１若しくは２のフッ素化アルキル基）で示される。 The fluorinated diether (4) has the general formula (4):

(Wherein, R ⁴¹ and R ⁴² are independently H, CH ₃ , F, CH ₂ F, CHF ₂ or CF ₃ , R ⁴³ is a C 1 or C 2 non-fluorinated alkyl group or C 1 or C 2 2 fluorinated alkyl group).

As R ⁴¹ and R ⁴² , H or F is preferable independently.

As R ⁴³ , CH ₃ , CH ₂ F, CHF ₂ or CF ₃ is preferable.

As fluorinated diether (4), CH ₃ OCH ₂ CH ₂ OCF ₃ , CH ₃ OCH ₂ CH ₂ OCFH ₂ , CH ₃ OCH ₂ CH ₂ OCF ₂ H, H ₂ CFOCH ₂ CH ₂ OCFH ₂ , HCF ₂ OCH ₂ At least one selected from the group consisting of CH ₂ OCF ₂ H and CF ₃ OCH ₂ CH ₂ OCF ₃ is preferred.

（式中、Ｒｆ^５１は、独立に、Ｆ又は炭素数１若しくは２のフッ素化アルキル基、Ｒ^５１、Ｒ^５２及びＲ^５３は、独立に、Ｈ、Ｆ、炭素数１若しくは２の非フッ素化アルキル基又は炭素数１若しくは２のフッ素化アルキル基）で示される。 The fluorinated diether (5) has the general formula (5):

(Wherein, R f ⁵¹ is independently F or a fluorinated alkyl group having 1 or 2 carbon atoms, R ⁵¹ , R ⁵² and R ⁵³ are independently H, F, 1 or 2 carbon atoms and non-fluorinated Alkyl group or fluorinated alkyl group having 1 or 2 carbon atoms).

As Rf ⁵¹ , F, CH ₂ F, CHF ₂ or CF ₃ is preferable, and F is more preferable.

In terms of oxidation resistance and viscosity, R ⁵¹ , R ⁵² and R ⁵³ independently preferably H or F, and independently preferably F.

As fluorinated diether (5), CH ₃ -OCF ₂ CF ₂ OCH ₃ , CH ₃ -OCHFCF ₂ OCH ₃ , CH ₃ -OCF ₂ CH ₂ OCH ₃ , CH ₃ -OCHFCHFOCH ₃ , CH ₃ -OCH (CF ₃ At least one member selected from the group consisting of CH ₂ OCH ₃ , CH ₃ OCH (CH ₂ F) CH ₂ OCH ₃ and CH ₃ OCH (CHF ₂ ) CH ₂ OCH ₃ is preferred.

（式中、Ｒ^６１は、炭素数１若しくは２の非フッ素化アルキル基、又は、炭素数１若しくは２のフッ素化アルキル基）で示される。 The fluorinated linear carbonate (6) has the general formula (6):

(Wherein, R ⁶¹ is a non-fluorinated alkyl group having 1 or 2 carbon atoms, or a fluorinated alkyl group having 1 or 2 carbon atoms).

As R ⁶¹ , CH ₃ or C ₂ H ₅ is preferable.

The fluorinated chain carbonate _{(6), F 3 C-} OCOO-CH 3 and _{F 3 C-OCOO-C 2} H at least one ₅ is selected from the group consisting of is preferred.

（式中、Ｒ^７１は、炭素数１若しくは２の非フッ素化アルキル基、又は、炭素数１若しくは２のフッ素化アルキル基）で示される。 The fluorinated linear carbonate (7) has the general formula (7):

(Wherein, R ⁷¹ is a C 1 or C 2 non-fluorinated alkyl group, or a C 1 or 2 carbon fluorinated alkyl group).

As R ⁷¹ , CH ₃ or C ₂ H ₅ is preferable.

As the fluorinated linear carbonate (7), at least one selected from the group consisting of H ₂ FC-OCOOO-CH ₃ and H ₂ FC-OCOOO-C ₂ H ₅ is preferable, and H ₂ FC-OCOOO-CH is preferable. ₃ is more preferable.

The content of the compound (b) is preferably 5% by volume or more, more preferably 6% by volume or more, and still more preferably 10% by volume or more based on the solvent, since further excellent cycle characteristics can be obtained. Preferably, 80% by volume or less is preferable, and 60% by volume or less is more preferable.

In the electrolytic solution of the present invention, the solvent may contain the compound (a) and the compound (b).

When the solvent contains the compound (a) and the compound (b), the solvent contains 11 to 80% by volume of the fluorinated lactone (1), 10 to 80% by volume of the compound (a), and % Of the compound (b), and the electrolyte preferably contains 0.01 to 10% by mass of the compound (2) with respect to the solvent.

When the solvent contains the compound (a) and the compound (b), the solvent contains 20 to 70% by volume of the fluorinated lactone (1), 20 to 70% by volume of the compound (a), and 10 to 30% by volume % Of the compound (b), and the electrolyte preferably contains 0.01 to 5% by mass of the compound (2) with respect to the solvent.

It is preferable that the electrolyte solution of this invention contains electrolyte salt (however, except a compound (2)).
Examples of the electrolyte salt include alkali metal salts, alkaline earth metal salts, metal salts having aluminum as a cation, ammonium salts, liquid salts (ionic liquids), inorganic polymer type salts, organic polymer type Any salt that can be used for the electrolyte can be used, such as salts of

As an electrolyte salt of the electrolyte solution for lithium ion secondary batteries, an alkali metal salt is preferable and a lithium salt is more preferable.
Arbitrary things can be used as said lithium salt, The following are mentioned specifically. For _{example, LiPF 6, LiBF 4, LiClO} 4, LiAlF 4, LiSbF 6, inorganic lithium salts LiTaF 6, LiWF ₇ and the like;
Lithium tungstates such as LiWOF ₅ ;
HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Carboxylic acid lithium salts such as CO ₂ Li, CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li;
FSO ₃ Li, CH ₃ SO ₃ Li, CH ₂ FSO ₃ Li, CHF ₂ SO ₃ Li, CF ₃ SO ₃ Li, CF ₃ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ SO ₃ Li, CF ₃ CF ₂ Sulfonic acid lithium salts such as CF ₂ CF ₂ SO ₃ Li;
_{LiN (FCO) 2, LiN (} FCO) (FSO 2), LiN (FSO 2) 2, LiN (FSO 2) (CF 3 SO 2), LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO _{2) 2,} lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic _{1,3-perfluoropropanedisulfonylimide, LiN (CF 3 SO 2)} (C 4 F 9 SO 2) lithium imide salts such as ;
Lithium methide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) _{3 and the} like;
In addition, a salt represented by the formula: LiPF _a (C _n F _{2 n + 1} ) _6-a (wherein, a is an integer of 0 to 5 and n is an integer of 1 to 6) (eg 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 ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiBF Fluorine-containing organic compounds such as ₃ C ₃ F ₇ , 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 Lithium salts; and the like.

Among them, the above lithium salt is capable of suppressing deterioration after storage of the electrolytic solution at a high temperature, and thus 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 _{2 n + 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.

_Formula: The salt represented by _{LiPF a (C n F 2n +} 1) 6-a, for _{example, 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 (wherein And the alkyl group represented by C ₃ F ₇ or C ₄ F ₉ in the formula may be linear or branched, and the like.

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

An ammonium salt is preferable as the electrolyte salt of the electrolytic solution for an electric double layer capacitor.
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。

(In the formula, R ^1a , R ^2a , R ^3a and R ^4a are the same or different and each may be an alkyl group containing an ether bond of 1 to 6 carbon atoms; X ^- is an anion) Preferred are quaternary ammonium salts. In addition, those in which part or all of the hydrogen atoms of this ammonium salt are substituted with a fluorine atom and / or a fluorinated alkyl group having 1 to 4 carbon atoms are also preferable from the viewpoint of improving the oxidation resistance.

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) 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、粘性の低下を図ることができる。

(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 ^- represents an anion) an alkyl ether group-containing trialkyl ammonium salt,
Etc. The viscosity can be reduced by introducing an alkyl ether group.

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 ⁻ , and (C ₂ F ₅ SO ₂ ) ₂ N ⁻ .

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

Preferred 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 3} MeN (CF ₃ SO ₂ ) ₂ N, Et ₃ MeNC ₄ F ₉ SO ₃ may be used, and 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 etc. Be

(IIb) Spirocyclic 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 each is an alkyl group having 1 to 4 carbon atoms; X ^- is an anion; n 1 is an integer of 0 to 5; n 2 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 each is an alkyl group having 1 to 4 carbon atoms; X ^- is an anion; n 3 is an integer of 0 to 5; n 4 is an integer of 0 to 5) Spirocyclic bipyrrolidinium salts, 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 each is an alkyl group having 1 to 4 carbon atoms; X ^- is an anion; n 5 is an integer of 0 to 5; n 6 is an integer of 0 to 5) Spirocyclic bipyrrolidinium salts are preferably mentioned. In addition, those in which part or all of the hydrogen atoms of this spirocyclic bipyrrolidinium salt are substituted with a fluorine atom and / or a fluorinated alkyl group having 1 to 4 carbon atoms are also preferable from the viewpoint of improving the oxidation resistance.

Anion X ^- of the preferred embodiment are the same as for (IIa). Among them, BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ or (C ₂ F ₅ SO ₂ ) ₂ N ⁻ from the viewpoint of high dissociativeness and low internal resistance under high voltage. preferable.

などが挙げられる。 Preferred specific examples of the spirocyclic bipyrrolidinium salt include, for example,

Etc.

The spirocyclic bipyrrolidinium salt is excellent in solubility in solvents, oxidation resistance, and ion 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。

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

Anion X ^- of the preferred embodiment is the same as (IIa).

As a preferred embodiment, for example,

等が挙げられる。

Etc.

This imidazolium salt is excellent in that it has 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)
The N-alkyl pyridinium salt shown by these can be illustrated preferably. In addition, those in which part or all of hydrogen atoms of this N-alkylpyridinium salt are substituted with a fluorine atom and / or a fluorinated alkyl group having 1 to 4 carbon atoms are also preferable from the viewpoint of improving the oxidation resistance.

Anion X ^- of the preferred embodiment is the same as (IIa).

As a preferred embodiment, 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 each is an alkyl group having 1 to 6 carbon atoms; X ^- is an anion)
The N, N-dialkyl pyrrolidinium salt shown by these can be illustrated preferably. The oxidation resistance is also improved in the case where part or all of the hydrogen atoms of this N, N-dialkylpyrrolidinium salt is substituted with a fluorine atom and / or a fluorinated alkyl group having 1 to 4 carbon atoms. It is preferable from the point of view.

Anion X ^- of the preferred embodiment is the same as (IIa).

As a preferred embodiment, for example,

などが挙げられる。

Etc.

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

Among these ammonium salts, (IIa), (IIb) and (IIc) are preferable in terms of good solubility, oxidation resistance and ion conductivity, and further preferred

（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。

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

In addition, a lithium salt may be used as an electrolyte salt for an electric double layer capacitor. Examples of the lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF 6, LiN (SO 2 C 2 H 5) 2 is preferred.
Magnesium salts may be used to further improve the capacity. The magnesium salt, _{e.g., Mg (ClO 4) 2,} Mg (OOC 2 H 5) 2 and the like are preferable.

When the electrolyte salt is the above ammonium salt, the concentration is preferably 0.6 mol / l or more. If the amount is less than 0.6 mol / liter, not only the low temperature characteristics deteriorate, but also the initial internal resistance increases. The concentration of the electrolyte salt is more preferably 0.9 mol / l or more.
The concentration is preferably 3.0 mol / l or less, more preferably 2 mol / l or less, in terms of low temperature characteristics.
In the case where the above ammonium salt is triethylmethyl tetrafluoroborate (TEMABF ₄ ), the concentration is preferably 0.8 to 1.9 mol / L in terms of excellent low temperature characteristics.
In the case of spirobipyrrolidinium tetrafluoride (SBPBF ₄ ), it is preferably 0.7 to 2.0 mol / liter.

The electrolytic solution of the present invention preferably further comprises polyethylene oxide having a weight average molecular weight of 2000 to 4000 and having -OH, -OCOOH or -COOH at the end.
By containing such a compound, the stability of the electrode interface can be improved, and the characteristics of the electrochemical device can be improved.
As said polyethylene oxide, polyethylene oxide monool, polyethylene oxide carboxylic acid, polyethylene oxide diol, polyethylene oxide dicarboxylic acid, polyethylene oxide triol, polyethylene oxide tricarboxylic acid etc. are mentioned, for example. These may be used alone or in combination of two or more.
Among them, a mixture of polyethylene oxide monool and polyethylene oxide diol, and a mixture of polyethylene carboxylic acid and polyethylene dicarboxylic acid are preferable in that the characteristics of the electrochemical device become better.

If the weight average molecular weight of the above-mentioned polyethylene oxide is too small, there is a possibility that it is easy to be oxidatively decomposed. As for the said weight average molecular weight, 3000-4000 are more preferable.
The said weight average molecular weight can be measured by polystyrene conversion by gel permeation chromatography (GPC) method.

It is preferable that content of the said polyethylene oxide is 1 * 10 ^{< -6} > ^-1 * 10 ^<-2 > mol / kg in electrolyte solution. If the content of the polyethylene oxide is too high, the properties of the electrochemical device may be impaired.
The content of the polyethylene oxide is more preferably 5 × 10 ⁻⁶ mol / kg or more.

The electrolytic solution of the present invention may further contain unsaturated cyclic carbonate, an overcharge inhibitor, other known auxiliary agents and the like. Thereby, the deterioration of the characteristics of the electrochemical device can be suppressed.

Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, And catechol carbonates.

The vinylene carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylvinylene carbonate, 4,5-divinylvinylene carbonate, allylvinylene carbonate, 4 5-diallylvinylene carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluoro Vinylene carbonate etc. are mentioned.

Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5- Vinyl ethylene carbonate, 4-allyl-5-vinyl ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ethylene carbonate, 4-allyl -5-ethynyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, 4-phenyl-5-vinyl ethylene carbonate, 4-allyl-5-phenyl ethylene carbonate, allyl ethylene carbonate 4,5 diallyl carbonate, 4-methyl-5-allyl carbonate and the like.

Among them, as unsaturated cyclic carbonates, vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, vinylvinylene carbonate, 4,5-vinylvinylene carbonate, allylvinylene carbonate, 4,5-diallylvinylene carbonate, vinyl Ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, 4-allyl-5-vinyl Ethylene carbonate, ethynyl ethylene carbonate, 4,5-diethynyl ethylene carbonate, 4-methyl-5-ethynyl ethylene carbonate, 4-vinyl-5-ethynyl ether Ren carbonate is preferred. In addition, vinylene carbonate, vinyl ethylene carbonate and ethynyl ethylene carbonate are particularly preferable because they form a more stable surface protective film.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary unless the effects of the present invention are significantly impaired. The molecular weight is preferably 50 or more and 250 or less. Within this range, the solubility of the unsaturated cyclic carbonate in the electrolytic solution can be easily secured, and the effects of the present invention can be sufficiently exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more, and more preferably 150 or less.

The method for producing the unsaturated cyclic carbonate is not particularly limited, and any known method can be selected for production.

The unsaturated cyclic carbonates may be used alone or in any combination of two or more in any proportion.

The content of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary unless the effects of the present invention are significantly impaired. The content of the unsaturated cyclic carbonate is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 0.1% by mass or more in 100% by mass of the solvent in the present invention. The content is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. Within the above range, an electrochemical device using an electrolytic solution is likely to exhibit a sufficient cycle characteristics improvement effect, and also the high temperature storage characteristics deteriorate, the amount of gas generation increases, and the discharge capacity retention rate decreases. It is easy to avoid such situations.

Moreover, as unsaturated cyclic carbonate, the fluorinated unsaturated cyclic carbonate other than the above-mentioned non-fluorinated unsaturated cyclic carbonate can also be used suitably. The fluorinated unsaturated cyclic carbonate is a cyclic carbonate having an unsaturated bond and a fluorine atom.
The number of fluorine atoms 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 one or two are most preferable.

Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives, fluorinated ethylene carbonate derivatives substituted with a substituent having an aromatic ring or a carbon-carbon double bond, and the like.
As fluorinated vinylene carbonate derivatives, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4-fluoro-5-fluorovinylene carbonate And vinyl vinylene carbonate and the like.

As a fluorinated ethylene carbonate derivative substituted by a substituent having an aromatic ring or a carbon-carbon double bond, 4-fluoro-4-vinyl ethylene carbonate, 4-fluoro-4-allyl ethylene carbonate, 4-fluoro-5 -Vinyl ethylene carbonate, 4-fluoro-5-allyl ethylene carbonate, 4,4-difluoro-4-vinyl ethylene carbonate, 4,4-difluoro-4-allyl ethylene carbonate, 4,5-difluoro-4-vinyl ethylene carbonate 4,5-Difluoro-4-allyl ethylene carbonate, 4-fluoro-4,5-divinyl ethylene carbonate, 4-fluoro-4,5-diallyl ethylene carbonate, 4,5-difluoro-4,5-divinyl ethylene carbonate , 4, 5-diful 4, 4-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4, 4-difluoro-5-phenylethylene carbonate, 4, 5-difluoro-4- 4- Phenyl ethylene carbonate etc. are mentioned.

Among them, as fluorinated unsaturated cyclic carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate, 4-allyl-5-fluorovinylene carbonate, 4- Fluoro-4-vinyl ethylene carbonate, 4-fluoro-4-allyl ethylene carbonate, 4-fluoro-5-vinyl ethylene carbonate, 4-fluoro-5-allyl ethylene carbonate, 4,4-difluoro-4-vinyl ethylene carbonate, 4,4-Difluoro-4-allyl ethylene carbonate, 4,5-difluoro-4-vinyl ethylene carbonate, 4,5-difluoro-4-allyl ethylene carbonate, 4-fluoro-4,5-divinyl ethylene carbonate, -Fluoro-4,5-diallyl ethylene carbonate, 4,5-difluoro-4,5-divinyl ethylene carbonate, 4,5-difluoro-4,5-diallyl ethylene carbonate form a stable surface protective film, It is more preferably used.

The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited, and is optional 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. Within this range, the solubility of the fluorinated unsaturated cyclic carbonate in the electrolytic solution can be easily secured, and the effects of the present invention can be easily exhibited.

The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and any known method can be selected for production.
The molecular weight is more preferably 100 or more, and more preferably 200 or less.

The fluorinated unsaturated cyclic carbonates may be used alone or in any combination of two or more in any proportion.
Further, the content of the fluorinated unsaturated cyclic carbonate is not particularly limited, and is optional unless the effects of the present invention are significantly impaired.
The content of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 0.5% by mass or more in 100% by mass of the electrolytic solution. Also preferably, it is 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less.
Within this range, an electrochemical device using an electrolytic solution is likely to exhibit a sufficient cycle characteristics improvement effect, and also the high temperature storage characteristics deteriorate, the gas generation amount increases, and the discharge capacity retention rate decreases. It is easy to avoid such situations.

In the electrolytic solution of the present invention, an overcharge preventing agent can be used to effectively suppress the battery from bursting / ignition when the electrochemical device using the electrolytic solution becomes overcharged or the like. .

As an overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran and the like; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, etc .; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole, etc. And fluorine-containing anisole compounds.
Among them, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran and the like 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, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, The combined use of at least one selected from an oxygen-free aromatic compound such as t-amylbenzene and at least one selected from an oxygen-containing aromatic compound such as diphenyl ether and dibenzofuran is an overcharge preventing property and a high temperature storage characteristic It is preferable from the point of balance of

Other known auxiliary agents can be used in the electrolytic solution of the present invention.
Other auxiliary agents include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate, etc .; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, anhydride Carboxylic anhydrides such as itaconic acid, diglycolic anhydride, cyclohexanedicarboxylic acid anhydride, cyclopentanetetracarboxylic acid dianhydride and phenylsuccinic anhydride; 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, 1,3-propane sultone, 1-fluoro-1,3- Propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro Oro-1,3-propane sultone, 1-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro -1-propene-1,3-sultone, 1,4-butanesultone, 1-butene-1,4-sultone, 3-butene-1,4-sultone, methyl fluorosulfonate, ethyl fluorosulfonate, methanesulfonic acid Methyl, ethyl methane sulfonate, busulfan, sulfolene, diphenyl sulfone, N, N-dimethyl methane sulfonamide, N, N-diethyl methane sulfonamide, methyl vinyl sulfonate, ethyl vinyl sulfonate, allyl vinyl sulfonate, vinyl sulfonic acid Propargyl, methyl allyl sulfonate, ethyl allyl sulfonate, allyl Sulfur-containing compounds such as allyl sulfonylate, propargyl allyl sulfonate and 1,2-bis (vinylsulfonyloxy) ethane; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone Nitrogen-containing compounds such as 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; trimethyl phosphite, triethyl phosphite, triphenyl phosphite, trimethyl phosphate, triethyl phosphate, triphosphate Phosphorus-containing compounds such as phenyl, methyl methylphosphonate, diethyl ethylphosphonate, dimethyl vinylphosphonate, diethyl vinylphosphonate, ethyl diethylphosphonoacetate, methyl dimethylphosphinate, ethyl diethylphosphinate, trimethylphosphine oxide, triethylphosphine oxide and the like; Hep Examples thereof include hydrocarbon compounds such as tan, octane, nonane, decane and cycloheptane, and fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride.
These may be used alone or in combination of two or more.
By adding these assistants, capacity retention characteristics and cycle characteristics after high temperature storage can be improved.

The amount of the other auxiliary agent is not particularly limited, and is optional unless the effects of the present invention are significantly impaired.
The other auxiliary agent is preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the electrolytic solution.
Within this range, the effects of the other auxiliary agents can be sufficiently exhibited, and situations in which battery characteristics such as high load discharge characteristics are degraded can be easily avoided.
The compounding amount of the other auxiliary agent is more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and more preferably 3% by mass or less, still more preferably 1% by mass or less .

The electrolytic solution of the present invention can contain an acid anhydride having a succinic acid backbone. As the acid anhydride having a succinic acid skeleton, succinic anhydride, maleic anhydride, citraconic acid, 2-methylsuccinic acid, 2,3-dimethylsuccinic acid, 2-fluorosuccinic acid, 2,3-difluorosuccinic acid and the like Can be mentioned. Among these, succinic anhydride or maleic anhydride is preferred.

The content of the acid anhydride having a succinic acid skeleton is preferably 0.1 to 10% by mass in the electrolytic solution, more preferably 0.5% by mass or more, and more preferably 5% by mass or less.

The electrolytic solution of the present invention can contain a cyclic sulfonic acid compound. Examples of the cyclic sulfonic acid compounds 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. Among them, the electrolytic solution of the present invention preferably contains 1,3-propane sultone and / or 1,4-butane sultone in that high temperature characteristics can be improved.

The content of the cyclic sulfonic acid compound in the electrolytic solution is preferably 0.1 to 10% by mass, more preferably 0.5% by mass or more, and more preferably 5% by mass or less.

The electrolytic solution of the present invention is a cyclic and linear carboxylic acid ester, an ether compound, a nitrogen-containing compound, a boron-containing compound, an organic silicon-containing compound, an incombustible (flame retardant) agent, an interface, as long as the effects of the present invention are not impaired. The composition may further contain an activator, a dielectric additive, a cycle characteristic, a rate characteristic improver, and the like.

Examples of the cyclic carboxylic acid ester include those having 3 to 12 carbon atoms in total in the structural formula. Specifically, gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone and the like can be mentioned. Among them, gamma-butyrolactone is particularly preferable from the viewpoint of the improvement of the characteristics of the electrochemical device derived from the improvement of the lithium ion dissociation degree.

The compounding amount of the cyclic carboxylic acid ester is usually 0.1% by mass or more, preferably 1% by mass or more, in 100% by mass of the solvent. Within this range, the electrical conductivity of the electrolytic solution can be improved, and the large current discharge characteristics of the electrochemical device can be 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 made into an appropriate range, the decrease of the electric conductivity is avoided, the increase of the negative electrode resistance is suppressed, and the large current discharge characteristics of the electrochemical device is made into a good range. Make it easy.

As said chain | strand-shaped carboxylic acid ester, the thing of 3-7 total carbons in the structural formula is mentioned. Specifically, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyrate-n- Propyl, isopropyl isobutyrate and the like can be mentioned.

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

As said ether compound, a C3-C10 chain | strand-shaped ether and C3-C6 cyclic ether are preferable.
As a C3-C10 linear ether, diethylether, di-n-butylether, dimethoxymethane, methoxyethoxymethane, diethoxymethane, dimethoxyethane, methoxyethoxyethane, diethoxyethane, ethylene glycol di-n-propyl Ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether etc. are mentioned.

Moreover, as said ether compound, a fluorinated ether can also be used suitably.
As said fluorinated ether, the following general formula (K):
Rf ¹ -O-Rf ² (K)
(Wherein, R f ¹ and R f ² are the same or different and each is an alkyl group having 1 to 10 carbon atoms or a fluorinated alkyl group having 1 to 10 carbon atoms. However, at least one of R f ¹ and R f ² is fluorine And fluorinated ethers (K) represented by 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 above general formula (K), at least one of Rf ¹ and Rf ² may be a fluorinated alkyl group having 1 to 10 carbon atoms, but the flame retardancy of the electrolytic solution, stability at high temperature and high voltage, safety From the viewpoint of further improving the properties, it is preferable that both Rf ¹ and Rf ² be a fluorinated alkyl group having 1 to 10 carbon atoms. In this case, Rf ¹ and Rf ² may be the same or may be different from each other.
Among them, Rf ¹ and Rf ² are the same or different, and 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 More preferable.

If the total carbon number of Rf ¹ and Rf ² is too low, the boiling point of the fluorinated ether becomes too low, and if the carbon number of Rf ¹ or Rf ² is too high, the solubility of the electrolyte salt decreases and other solvents The compatibility with the compound also begins to be adversely affected, and the rate characteristic decreases because the viscosity increases. When the carbon number of Rf ¹ is 3 or 4, and the carbon number of Rf ² is 2 or 3, it is advantageous in that the boiling point and rate characteristics are excellent.

The fluorinated ether (K) preferably has a fluorine content of 40 to 75% by mass. When it has a fluorine content in this range, the balance between incombustibility and compatibility becomes particularly excellent. Moreover, it is preferable also from the point whose oxidation resistance and safety are favorable.
The lower limit of the fluorine content is more preferably 45% by mass, further 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 fluorinated ether (K)} × 100 (%) based on the structural formula of fluorinated ether (K) It is a value calculated by

As R f ¹ , for example, 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.
As the Rf ^2, for _{example, 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), 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 and the} like.

Among them, one containing HCF ₂ — or CF ₃ CFH— at one end or both ends is excellent in polarizability and can provide a fluorinated ether (K) having a high boiling point. The boiling point of the fluorinated ether (K) is preferably 67 to 120 ° C. The temperature is more preferably 80 ° C. or more, still more preferably 90 ° C. or more.

Such fluorinated ether (K), for _{example, 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, 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 H, or the like The above is mentioned.
Among them, HCF ₂ CF ₂ CH ₂ OCF ₂ CFHCF ₃ (boiling point 106 ° C.), CF ₃ CF ₂ CH, which is advantageous in that it has high boiling point, compatibility with other solvents and good solubility of 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.) 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.) It is more preferable that it is 1 type.

Examples of cyclic ethers 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 Can be mentioned. Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high ability to solvate lithium ions and improve the degree of ion dissociation. Among these, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferable because of their low viscosity and high ionic conductivity.

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

Examples of the boron-containing compound include borate esters such as trimethyl borate and triethyl borate, borate ethers, and alkyl borates.

Examples of the organic silicon-containing compounds, _{e.g., (CH 3)} 4 _-Si, include (CH 3) 3 -Si-Si (CH 3) 3 or the like.

Examples of the non-combustible (flame-retardant) agent include phosphoric acid esters and phosphazene compounds. Examples of the phosphoric acid ester include fluorine-containing alkyl phosphoric acid esters, non-fluorinated alkyl phosphoric acid esters, and aryl phosphoric acid esters. Among them, fluorine-containing alkyl phosphates are preferable in that they can exhibit the non-combustible effect in a small amount.

Specific examples of the fluorine-containing alkyl phosphoric acid ester include fluorine-containing dialkyl phosphoric acid esters described in JP-A-11-233141, and cyclic alkyl phosphoric acid esters described in JP-A-11-283669. And / or fluorine-containing trialkyl phosphate esters and the like.

As the incombustible (flame retardant) _{agents, (CH 3 O) 3 P} = O, (CF 3 CH 2 O) 3 P = O, (HCF 2 CH 2 O) 3 P = O, (CF 3 CF 2 CH ₂ ) ₃ P = O, (HCF ₂ CF ₂ CH ₂ ) 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, but from the viewpoint of favorable cycle characteristics and rate characteristics, a fluorine atom. Is preferable.

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 which may contain an ether bond of 3 to 10 carbon atoms; M ⁺ is Li ⁺ , Na ⁺ , K ⁺ or NHR ′ ₃ ⁺ (R ′ is the same or different) And a fluorine-containing carboxylic acid salt represented by the following formula:
Rf ² SO ₃ ⁻ M ⁺
(Wherein, R f ² is a fluorinated alkyl group which may contain an ether bond of 3 to 10 carbon atoms; M ⁺ is Li ⁺ , Na ⁺ , K ⁺ or NHR ′ ₃ ⁺ (R ′ is the same or different) And fluorine-containing sulfonates and the like, which are each represented by 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 of being able to reduce the surface tension of the electrolytic solution without deteriorating the charge and discharge cycle characteristics.

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

Examples of the above cycle characteristics and rate characteristics improver include methyl acetate, ethyl acetate, tetrahydrofuran, 1,4-dioxane and the like.

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

As such polymer materials, conventionally known polyethylene oxide and polypropylene oxide, modified products thereof (Japanese Patent Application Laid-Open Nos. 8-222270 and 2002-100405); polyacrylate polymers, polyacrylonitrile, polyvinylidene fluoride and the like And fluorine resins such as vinylidene fluoride-hexafluoropropylene copolymer (JP-A-4-506726, JP-A-8-507407, JP-A-10-294131); those fluororesins and hydrocarbon-based resins Composites with resins (JP-A-11-35765, JP-A-11-86630) and the like can be mentioned. In particular, it is desirable to use polyvinylidene fluoride or a vinylidene fluoride-hexafluoropropylene copolymer as the polymer material for gel electrolyte.

In addition, the electrolytic solution of the present invention may also contain the 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 is the formula (2-1):
-(D1) _n- (FAE) _m- (AE) _p- (Y) _q- (2-1)
(Wherein, D1 is the formula (2a):

(Wherein R f is a fluorine-containing ether group which may have a crosslinkable functional group; R ¹⁰ is a group or a bond which bonds the main chain with R f) an ether having a fluorine-containing ether group in the side chain unit;
The FAE is represented by the formula (2b):

(Wherein, Rfa is a hydrogen atom, a fluorinated alkyl group which may have a crosslinkable functional group; R ¹¹ is a group or a bond connecting the main chain with Rfa) and a fluorinated alkyl group is a side chain With ether units;
AE is the equation (2c):

(Wherein 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 substituted; R ¹² represents an ether unit represented by R ¹³ and a group or a bond connecting the main chain with R ¹³ ;
Y is any of the 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; however, n + m is not 0, and the bonding order of D1, FAE, AE and Y is Not identified);
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 fluorine atom and / or a phenyl group which may contain a crosslinkable functional group, -COOH Group, -OR (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 the terminal of D is an oxygen atom, -COOH group, It is an amorphous fluorine-containing polyether compound which has a fluorine-containing group in the side chain represented by -OR, not an ester group and a carbonate group.

Other additives may be further added to the electrolytic solution of the present invention as required. Examples of other additives include metal oxides and glasses.

The electrolytic 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 low, the film forming ability of the additive on the negative electrode tends to be reduced, and the characteristics of the electrochemical device tend to be deteriorated. In addition, when the HF content is too high, the oxidation resistance of the electrolytic solution tends to decrease due to the influence of HF. The electrolytic solution of the present invention does not lower the high temperature storability recovery capacity rate of the electrochemical device even if it contains HF in the above range.
As for content of HF, 1 ppm or more is more preferable, and 2.5 ppm or more is still more preferable. The content of HF is more preferably 60 ppm or less, further preferably 50 ppm or less, and particularly preferably 30 ppm or less.
The content of HF can be measured by neutralization titration.

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

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

Examples of electrochemical devices include lithium ion secondary batteries, capacitors (electric double layer capacitors), radical batteries, solar cells (especially dye-sensitized solar cells), fuel cells, various electrochemical sensors, electrochromic elements, electrochemical switching A device, an aluminum electrolytic capacitor, a tantalum electrolytic capacitor, etc. are mentioned, A lithium ion secondary battery and an electric double layer capacitor are suitable.
A module provided with the above-mentioned electrochemical device is also one of the present invention.

The present invention is also a lithium ion secondary battery comprising the electrolytic solution of the present invention.
The lithium ion secondary battery may include a positive electrode, a negative electrode, and the above-described electrolyte solution.

<Positive electrode>
The positive electrode is composed of a positive electrode active material layer containing a positive electrode active material and a current collector.

The positive electrode active material is not particularly limited as long as it can electrochemically store and release lithium ions. For example, a material containing lithium and at least one transition metal is preferable. Specific examples thereof include lithium-containing transition metal complex oxides and lithium-containing transition metal phosphate compounds. Among them, a lithium-containing transition metal complex oxide that produces a high voltage is particularly preferable as the positive electrode active material.

As a transition metal of the lithium-containing transition metal complex oxide, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable. As a specific example, lithium cobalt complex oxide such as LiCoO ₂ , LiNiO ₂ etc. Lithium-manganese complex oxides such as LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{4 and the} like, and a part of the transition metal atoms as the main component of these lithium transition metal complex oxides, Na, Substitution with other elements such as K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc. And the like. Specific examples of those substituted, for _{example, LiNi 0.5 Mn 0.5 O 2,} LiNi 0.85 Co 0.10 Al 0.05 O 2, LiNi 0.5 Co 0.2 Mn 0.3 O _{2, LiNi 0.6 Co 0.2 Mn 0.2} O 2, LiNi 0.33 Co 0.33 Mn 0.33 O 2, LiNi 0.45 Co 0.10 Al 0.45 O 2, LiMn 1. ₈ Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4 and the} like can be mentioned.

Among them, as the lithium-containing transition metal complex oxide, LiMn _1.5 Ni _0.5 O ₄ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , which have high energy density even at high voltage. LiNi _0.6 Co _0.2 Mn _0.2 O ₂ is preferred.

As a transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and as a specific example, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and a part of transition metal atoms which become main components of these lithium transition metal phosphate compounds Al, Ti, V, Cr, Mn What is substituted by other elements, such as Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc. are mentioned.

Examples of the lithium-containing transition metal composite oxide include
Formula: Li _a Mn _2-b M ¹ _b O ₄ (wherein, 0.9 ≦ a; 0 ≦ b ≦ 1.5; M ¹ is Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, Lithium-manganese spinel composite oxide represented by at least one metal selected from the group consisting of V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge)
Formula: LiNi _1-c M ² _c O ₂ (wherein, 0 ≦ c ≦ 0.5; M ² is Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, A lithium-nickel complex oxide represented by at least one metal selected from the group consisting of Sr, B, Ga, In, Si and Ge, or
_{Wherein: LiCo} in ^{_{1-d M 3 d O 2}} ( ^{wherein, 0 ≦ d ≦ 0.5; M} 3 is Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, And 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 from the viewpoint of being able to provide a lithium ion secondary battery with high energy density and high output. Or LiNi _1/3 Co _1/3 Mn _1/3 O ₂ is preferred.

Other of the positive electrode active _{material, 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. may be mentioned.

In addition, it is preferable to contain lithium phosphate in the positive electrode active material because continuous charge characteristics are improved. Although there is no restriction | limiting in use of lithium phosphate, It is preferable to mix and use said positive electrode active material and lithium phosphate. The lower limit of the amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass, based on 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 still more preferably 5% by mass or less.

Moreover, you may use the thing in which the substance of the composition different from this adhered on the surface of the said positive electrode active material. As surface adhesion substances, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as 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.

These surface adhesion substances are, for example, dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and dried, or the surface adhesion substance precursor is dissolved or suspended in a solvent and impregnated into 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 it to the positive electrode active material precursor and simultaneously baking it. In addition, when making carbon adhere, the method of making carbon quality adhere mechanically later, for example, in the form of activated carbon etc. can also be used.

The amount of the surface adhering substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and preferably 20% or less as an upper limit, based on the mass of the positive electrode active material. Is used at 10% or less, more preferably 5% or less. The surface adhesion substance can suppress the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material, and the battery life can be improved. However, when the adhesion amount is too small, the effect is not sufficiently expressed. If it is too high, the resistance may increase to inhibit the lithium ion ingress and egress.

The shape of the particles of the positive electrode active material may, for example, be a block, a polyhedron, a sphere, an oval sphere, a plate, a needle, or a column as conventionally used. In addition, primary particles may be aggregated 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 still more preferably 1.0 g / cm ³ or more. When the tap density of the positive electrode active material is below the above lower limit, the necessary amount of dispersion medium increases at the time of forming the positive electrode active material layer, and the required amount of the conductive material and the binder increases, and the positive electrode to the positive electrode active material layer The filling rate of the active material may be limited, and the battery capacity may be limited. By using a composite oxide powder with a high tap density, a high density positive electrode active material layer can be formed. Generally, the tap density is preferably as high as possible, and there is no particular upper limit. However, if it is too large, diffusion of lithium ions in the positive electrode active material layer through the electrolyte may be limited, and load characteristics may be easily degraded. The upper limit is preferably 4.0 g / cm ³ , more preferably 3.7 g / cm ³ , and still more preferably 3.5 g / cm ³ .
In the present invention, the tap density is determined by placing 5 to 10 g of the positive electrode active material powder in a 10 ml glass measuring cylinder and tapping the powder packing density (tap density) g / cm ³ when tapping 200 times with a stroke of about 20 mm. Ask as.

The median diameter d50 of the particles of the positive electrode active material (secondary particle diameter when primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 0.5 μm or more, further preferably Is preferably 0.8 μm or more, most preferably 1.0 μm or more, preferably 30 μm or less, more preferably 27 μm or less, still more preferably 25 μm or less, most preferably 22 μm or less. Below the lower limit, high tap density products may not be obtained. When the upper limit is exceeded, it takes time to diffuse lithium in the particles, resulting in deterioration of the battery performance or preparation of the positive electrode of the battery, ie active material When a conductive material, a binder or the like is slurried with a solvent and applied in a thin film, problems such as streaking may occur. Here, by mixing two or more types of the above-mentioned positive electrode active materials having different median diameters d50, the filling property at the time of preparation of the positive electrode can be further improved.

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

When 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. The upper limit is preferably 5 μm, more preferably 4 μm, still more preferably 3 μm, and most preferably 2 μm. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder packing property or significantly lowers the specific surface area, which may increase the possibility that battery performance such as output characteristics may be degraded. is there. On the other hand, if the lower limit is exceeded, usually problems such as poor reversibility of charge and discharge may occur due to underdeveloped crystals.

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, the longest value of the intercept by the left and right boundary lines of the primary particle with respect to the straight line in the horizontal direction is obtained for any 50 primary particles, and the average value is obtained Be

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, more preferably 40 m ² / g, further preferably 30 m ² / g. If the BET specific surface area is smaller than this range, the battery performance tends to be deteriorated, and if the BET specific surface area is large, it is difficult to increase the tap density, and a problem may easily occur in the coatability when forming the positive electrode active material layer.

In the present invention, the BET specific surface area is determined by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.) and predrying the sample for 30 minutes at 150 ° C. under nitrogen flow. It is defined as a value measured by a nitrogen adsorption BET one-point method by a gas flow method using a nitrogen-helium mixed gas which is accurately adjusted so that the value of the relative pressure of nitrogen to the 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 hybrid vehicles and dispersed power sources, high power is required, so the particles of the positive electrode active material are mainly secondary particles. It is preferable that
The particles of the positive electrode active material preferably include fine particles having an average particle diameter of secondary particles of 40 μm or less and an average primary particle diameter of 1 μm or less of 0.5 to 7.0% by volume. By including fine particles having an average primary particle diameter of 1 μm or less, the contact area with the electrolytic solution becomes large, and the diffusion of lithium ions between the electrode and the electrolytic solution can be made faster, as a result, the battery Output performance can be improved.

As a manufacturing method of a positive electrode active material, a general method is used as a manufacturing method of an inorganic compound. In particular, various methods can be considered to form spherical or elliptical spherical active materials. For example, a transition metal source material is dissolved or pulverized in a solvent such as water, and the pH is adjusted while stirring. Spherical precursor is collected and dried, if necessary, added with a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ and calcined at high temperature to obtain an active material. .

For the production of the positive electrode, the above-mentioned positive electrode active material may be used alone, or two or more of different compositions may be used in any combination or ratio. As a preferable combination in this case, 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 etc. Or a combination of 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, and 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. The upper limit is preferably 99% by mass, more preferably 98% by mass. If the content of the positive electrode active material in the positive electrode active material layer is low, the electrical 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 safe 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), fluororubber, ethylene-propylene rubber, styrene / butadiene / styrene block copolymer or its hydrogenated product, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Tadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or a 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). One of these substances may be used alone, or two or more of these substances may be used in any combination and ratio.

The content of the binder is usually 0.1% by mass or more, preferably 1% by mass or more, and 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% by mass or less, preferably 60% by mass or less, more preferably 40% by mass or less, and most preferably 10% by mass or less. If the proportion of the binder is too low, the positive electrode active material can not be sufficiently retained, and the mechanical strength of the positive electrode is insufficient, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity.

Examples of the thickener include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. One type may be used alone, or two or more types may be used in any combination and 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 a range of not more than mass%, more preferably not more than 2 mass%. Below this range, the coatability may be significantly reduced. If it exceeds, the proportion of the active material in the positive electrode active material layer may be reduced, which may cause a problem of a decrease in battery capacity or an increase in resistance between the positive electrode active materials.

A well-known conductive material can be used arbitrarily as said conductive material. Specific examples thereof include metal materials such as copper and nickel, graphites such as natural graphite and artificial graphite, carbon blacks 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 a solvent for forming a slurry, any solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as needed, is particularly selected as the solvent. There is no limitation, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and mixed solvents of alcohol and water. Examples of organic solvents 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) And amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphaamide and dimethylsulfoxide.

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

Examples of the shape of the current collector include metal foils, metal cylinders, metal coils, metal coils, metal plates, metal thin films, expanded metals, punched metals, foamed metals and the like in the case of metal materials, and in the case of carbon materials, carbon plates and carbons A thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. The thin film may be formed in a mesh shape as appropriate. 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 that the conductive support agent is apply | coated to the surface of a collector from a viewpoint of reducing the electrical contact resistance of a collector and a positive electrode active material layer. Examples of the conductive aid include carbon, and noble metals such as gold, platinum and silver.

The ratio of the thickness of the current collector to the thickness of the positive electrode active material layer is not particularly limited, but the value of (thickness of positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of current collector) is 20 It is preferably the following, more 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. If this range is exceeded, the current collector may generate Joule heat during high current density charge and discharge. Below this range, the volume ratio of the current collector to the positive electrode active material may increase, and the capacity of the battery may decrease.

The production of the positive electrode may be performed according to a conventional method. For example, the binder, thickener, conductive material, solvent and the like described above are added to the above-mentioned positive electrode active material to form a slurry-like positive electrode mixture, which is applied to a current collector, dried and pressed. There is a method of densifying.

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 4 g / cm ³ or less. If this range is exceeded, the permeability of the electrolyte to the vicinity of the current collector / active material interface may be reduced, and in particular, the charge / discharge characteristics at high current densities may be reduced, and a high output may not be obtained. On the other hand, if it is lower than that, the conductivity between the active materials may be reduced, and the battery resistance may be increased to fail to obtain a high output.

When using the electrolytic solution of the present invention, it is preferable to make the area of the positive electrode active material layer larger than the outer surface area of the battery case from the viewpoint of enhancing the stability at high output and high temperature. Specifically, the sum of the electrode area of the positive electrode and the surface area of the exterior of the secondary battery is preferably 15 or more, and more preferably 40 or more, in area ratio. The external surface area of the battery outer case is, in the case of a rectangular shape with a bottom, the total area obtained by calculation from the dimensions of the length, width, and thickness of the case portion filled with the power generation element excluding the protruding portion of the terminal. Say. In the case of a bottomed cylindrical shape, it is a geometric surface area which approximates the case part filled with the power generation element excluding the protruding part of the terminal as a cylinder. The sum of the 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 formed by forming the positive electrode mixture layer on both sides via the current collector foil. , The sum of the area to calculate each face 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 mixture layer obtained by subtracting the metal foil thickness of the core material is preferably set as the lower limit to one side of the current collector. Is preferably 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 that to which the substance of the composition different from this adhered on the surface of the said positive electrode plate. As surface adhesion substances, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as 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 active material layer containing a negative electrode active material, and a current collector.

As the negative electrode active material, a carbonaceous material capable of absorbing and desorbing lithium such as thermal decomposition products of organic matter and artificial graphite and natural graphite under various thermal decomposition conditions; and desorbing and releasing lithium such as tin oxide and silicon oxide Possible metal oxide materials; lithium metal; various lithium alloys; lithium-containing metal complex oxide materials and the like can be mentioned. These negative electrode active materials may be used as a mixture of two or more.

As carbonaceous materials capable of storing 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 of these graphites with pitch or other organic substances The material obtained by carbonization after application is preferred, and natural graphite, artificial graphite, artificial carbonaceous material, and carbonaceous materials obtained by heat-treating the artificial graphite material at 400 A carbonaceous material comprising at least two or more kinds of different crystalline carbonaceous materials and / or having an interface in which the different crystalline carbonaceous materials are in contact, and at least two or more different orientations of the negative electrode active material layer The material selected from carbonaceous materials having an interface in contact with the carbonaceous material is more preferable because the balance between the initial irreversible capacity and the high current density charge / discharge characteristics is good. 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.

As the above-mentioned artificial carbonaceous material and carbonaceous material obtained by heat treating artificial graphite material at 400 to 3200 ° C. one or more times, it is possible to oxidize coal coke, petroleum coke, coal pitch, petroleum pitch and these pitches. Treated, needle coke, pitch coke and carbon agents partially graphitized thereof, furnace black, acetylene black, pyrolyzate of organic matter such as pitch carbon fiber, carbonizable organic matter and carbides thereof, or carbonizable A solution obtained by dissolving the organic substance in a low molecular weight organic solvent such as benzene, toluene, xylene, quinoline, n-hexane and the like, carbides of these, and the like.

As a metal material (but excluding lithium titanium complex oxide) used as the above-mentioned negative electrode active material, if lithium can be occluded and released, a single lithium, a single metal and an alloy forming a lithium alloy, or oxidation thereof It may be any of compounds such as carbides, nitrides, silicides, sulfides or phosphides, and is not particularly limited. The single metal and alloy forming the lithium alloy is preferably a material containing Group 13 and Group 14 metal / metalloid elements, more preferably aluminum, silicon and tin (hereinafter referred to as “specific metal elements”. And metals or alloys or compounds containing these atoms. One of these may be used alone, or two or more of these may be used in any combination and ratio.

As a negative electrode active material having at least one kind of atom selected from specific metal elements, a metal simple substance of any one kind of specific metal element, an alloy composed of two or more kinds of specific metal elements, one kind or two kinds or more of specification Alloy consisting of metal element and one or more other metal elements, compound containing one or more specified metal elements, and oxide, carbide, nitride, silicide of the compound And complex compounds such as sulfides and phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

Moreover, the compound which these composite compounds couple | bonded with several types of elements, such as a simple metal, an alloy, or a nonmetallic element, etc. is also mentioned. Specifically, for example, in silicon and tin, an alloy of these elements and a metal which does not operate as a negative electrode can be used. For example, in the case of tin, a complex compound containing 5 to 6 elements in combination of a metal other than tin and silicon and acting as a negative electrode, a metal not acting as a negative electrode and a nonmetallic element may also be used it can.

Specifically, Si simple substance, SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi 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, SiO _v (0 <v ≦ 2), LiSiO or tin alone, SnSiO ₃ , LiSnO, Mg ₂ Sn, SnO _w (0 <w ≦ 2) can be mentioned.
In addition, a composite material containing Si or Sn as the first constituent element and additionally containing the second and third constituent elements can be mentioned. The second constituent element is, for example, at least one of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium and zirconium. The third constituent element is, for example, at least one of boron, carbon, aluminum and phosphorus.
In particular, since high battery capacity and excellent battery characteristics are obtained, silicon or tin alone (may contain a trace amount of impurities), SiO _v (0 <v ≦ 2), SnO _w (0 ≦ w ≦ 2), Si—Co—C composite, Si—Ni—C composite, Sn—Co—C composite, and Sn—Ni—C composite are preferable.

The lithium-containing metal complex 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 in terms of high current density charge and discharge characteristics, More preferably, a lithium-containing composite metal oxide material containing titanium is preferable, and a composite oxide of lithium and titanium (hereinafter abbreviated as "lithium-titanium composite oxide") is more preferable. That is, when a lithium titanium composite oxide having a spinel structure is used by being contained in a negative electrode active material for an electrolyte battery, the output resistance is greatly reduced, which is particularly preferable.

As said lithium titanium complex oxide, 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
Is particularly preferable because the battery performance is well balanced.

Particularly preferable 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 In addition, for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is mentioned as a preferable one.

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

Examples of the binding agent include the same as the binding agent that can be used for the positive electrode described above. 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, 15 Mass% or less is more preferable, 10 mass% or less is more preferable, and 8 mass% or less is particularly preferable. 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 may increase, which may result in a decrease in the battery capacity. Moreover, if it is less than the said range, strength reduction of a negative electrode may be caused.

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

As said thickener, the thing similar to the thickener mentioned above and which can be used for a positive electrode 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 below the above range, the coatability may be significantly reduced. If the above range is exceeded, the proportion of the negative electrode active material in the negative electrode active material layer may be reduced, and the battery capacity may be reduced or the resistance between the negative electrode active material may be increased.

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

As a solvent for forming a slurry, a solvent capable of dissolving or dispersing a negative electrode active material, a binder, a thickener used as needed, and a conductive material can be particularly selected. There is no limitation, and either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylacetamide, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like can be mentioned.

Examples of the material of the current collector for the negative electrode include copper, nickel, and stainless steel. Among them, copper foil is preferable in terms 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 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 too low. Conversely, if the thickness is too thin, the handling may be difficult.

The production of the negative electrode may be performed according to a conventional method. For example, the above-mentioned negative electrode material may be added with the above-mentioned binder, thickener, conductive material, solvent and the like to form a slurry, which is coated on a current collector, dried and then pressed to obtain high density. . Moreover, when using an alloy material, the method of forming the thin film layer (negative electrode active material layer) containing the above-mentioned negative electrode active material by methods, such as a vapor deposition method, a sputtering method, and a plating method, is also used.

The electrode structure when making the negative electrode active material 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 Is more preferable, 1.3 g · cm ⁻³ or more is particularly preferable, and 2.2 g · cm ⁻³ or less is preferable, 2.1 g · cm ⁻³ or less is more preferable, and 2.0 g · cm ⁻³ or less More preferably, 1.9 g · cm ⁻³ or less is particularly preferable. When 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, and the initial irreversible capacity is increased, and the electrolyte solution near the current collector / negative electrode active material interface In some cases, the high current density charge / discharge characteristics may be deteriorated due to the decrease in the permeability of the If the above range is exceeded, the conductivity between the negative electrode active materials may be reduced, the battery resistance may be increased, and the capacity per unit volume may be reduced.

The thickness of the negative electrode plate is designed according to the positive electrode plate to be used and is not particularly limited, but the thickness of the mixture layer obtained by subtracting the metal foil thickness of the core material 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 that to which the substance of the composition different from this adhered on the surface of the said negative electrode plate. As surface adhesion substances, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as 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 comprises 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 materials can be used. Among these, resins, glass fibers, inorganic substances, etc., which are formed of a material stable to the electrolytic solution of the present invention, are used, and porous sheet or non-woven fabric-like articles etc. excellent in liquid retention are used. preferable.

As a material of resin and a glass fiber separator, polyolefins, such as polyethylene and a polypropylene, aromatic polyamide, polytetrafluoroethylene, polyether sulfone, a glass filter etc. can be used, for example. One of these materials such as polypropylene / polyethylene two-layer film, polypropylene / polyethylene / polypropylene three-layer film may be used alone, or two or more thereof may be used in any combination and ratio. Among them, the separator is preferably a porous sheet or a non-woven fabric or the like that uses a polyolefin such as polyethylene or polypropylene as a raw material in that the permeability of the electrolytic solution and the shutdown effect are good.

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, and more preferably 30 μm or less. If the separator is thinner than the above range, the insulation and mechanical strength may be reduced. If the thickness is more than the above range, not only the battery performance such as rate characteristics may be degraded, but also the energy density of the entire electrolyte battery may be degraded.

Furthermore, when a porous sheet such as a porous sheet or non-woven fabric is used as the separator, the porosity of the separator is optional, but is usually 20% or more, preferably 35% or more, and more preferably 45% or more, Also, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. When the porosity is smaller than the above range, the film resistance tends to be increased and the rate characteristic tends to be deteriorated. Moreover, when it is larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

The average pore diameter of the separator is also optional, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. When the average pore size exceeds the above range, a short circuit is likely to occur. If the above range is exceeded, the film resistance may increase and the rate characteristics may deteriorate.

On the other hand, as the inorganic material, 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, and those having a particle shape or fiber shape are used. Used.

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

<Battery design>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate described above are intervened by the separator, and a structure in which the positive electrode plate and the negative electrode plate are spirally wound through the separator. Any one may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less .

When the electrode group occupancy rate falls below the above range, the battery capacity decreases. Further, when the above range is exceeded, the void space is small, the battery becomes high temperature, the members expand, the vapor pressure of the liquid component of the electrolyte becomes high, and the internal pressure rises, and the charge and discharge repetition performance as the battery Or, the characteristics such as high temperature storage may be lowered, and furthermore, a gas release valve may be actuated to release the internal pressure to the outside.

Although the current collecting structure is not particularly limited, in order to more effectively realize the improvement of the charge and discharge characteristics of the high current density by the electrolytic solution of the present invention, the structure of reducing the resistance of the wiring portion and the bonding portion may be used. preferable. When the internal resistance is thus reduced, the effect of using the electrolytic solution of the present invention is exhibited particularly well.

When the electrode group has the above-described laminated structure, a structure formed by bundling metal core portions of the respective electrode layers and welding them to terminals is suitably used. When the area of one electrode increases, the internal resistance increases, so it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the above-described wound structure, the internal resistance can be lowered by providing a plurality of lead structures on the positive electrode and the negative electrode and bundling them in the terminals.

The material of the outer case is not particularly limited as long as the material is stable to the electrolyte used. Specifically, a nickel-plated steel sheet, metals such as stainless steel, aluminum or aluminum alloy, magnesium alloy or the like, or a laminated film (laminated film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, metals of aluminum or aluminum alloy and laminate films are preferably used.

In the outer case using metals, the metals are welded to form a hermetically sealed structure by laser welding, resistance welding, ultrasonic welding, or a caulking structure is formed using the above metals via a resin gasket. The thing is mentioned. In the outer case using the above-mentioned laminated film, those having a sealing and sealing structure by thermally fusing the resin layers to each other may be mentioned. In order to improve the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, in the case where the resin layer is heat-sealed through the current collection terminal to form a sealed structure, the metal and the resin are joined, and therefore, a resin having a polar group or a modification having a polar group introduced as an intervening resin Resin is preferably used.

The shape of the lithium ion secondary battery of the present invention is arbitrary, and examples thereof include cylindrical, square, laminate, coin and large shapes. The shapes and configurations of the positive electrode, the negative electrode, and the separator can be changed and used according to the shapes of the respective batteries.

In addition, a module provided with the lithium ion secondary battery of the present invention is also one of the present invention.

A positive electrode, a negative electrode, and the above-described electrolyte solution, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material layer including a positive electrode active material, and the positive electrode active material includes Mn. The lithium ion secondary battery is also one of the preferred embodiments. Since the positive electrode active material layer containing a positive electrode active material containing Mn is provided, the lithium ion secondary battery is further excellent in high-temperature storage characteristics.

As the positive electrode active material containing Mn, it is possible to provide a lithium ion secondary battery having a high energy density and a high output, LiMn _1.5 Ni _0.5 O ₄ , LiNi _0.5 Co _0.2 Mn _{0 .3} O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ is preferred.

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. The upper limit is preferably 99% by mass, more preferably 98% by mass. If the content of the positive electrode active material in the positive electrode active material layer is low, the electrical capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

The positive electrode active material layer may further contain a conductive material, a thickener and a binder.

As the above-mentioned binder, any material can be used as long as it is a material safe 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), fluororubber, ethylene-propylene rubber, styrene / butadiene / styrene block copolymer or its hydrogenated product, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Tadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or a 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). One of these substances may be used alone, or two or more of these substances may be used in any combination and ratio.

The content of the binder is usually 0.1% by mass or more, preferably 1% by mass or more, and 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% by mass or less, preferably 60% by mass or less, more preferably 40% by mass or less, and most preferably 10% by mass or less. If the proportion of the binder is too low, the positive electrode active material can not be sufficiently retained, and the mechanical strength of the positive electrode is insufficient, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity.

Examples of the thickener include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. One type may be used alone, or two or more types may be used in any combination and 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 a range of not more than mass%, more preferably not more than 2 mass%. Below this range, the coatability may be significantly reduced. If it exceeds, the proportion of the active material in the positive electrode active material layer may be reduced, which may cause a problem of a decrease in battery capacity or an increase in resistance between the positive electrode active materials.

A well-known conductive material can be used arbitrarily as said conductive material. Specific examples thereof include metal materials such as copper and nickel, graphites such as natural graphite and artificial graphite, carbon blacks 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.

The positive electrode current collector is preferably made of a valve metal or an alloy thereof in order to further improve the high temperature storage characteristics. As said valve metal, aluminum, titanium, a tantalum, chromium etc. are mentioned. More preferably, the positive electrode current collector is made of aluminum or an alloy of aluminum.

The lithium ion secondary battery is further improved in high temperature storage characteristics, so that the part in contact with the electrolytic solution among the parts electrically connected to the positive electrode current collector is also a valve metal or an alloy thereof. It is preferable that it is comprised. In particular, of the battery outer case and the lead wire and the safety valve accommodated in the battery outer case, the portion electrically connected to the positive electrode current collector and in contact with the non-aqueous electrolyte is a valve metal or It is preferable to comprise the alloy. Stainless steel coated with valve metal or its alloy may be used.

The method for producing the positive electrode is as described above. For example, the above-mentioned binder, thickener, conductive material, solvent and the like are added to the above-mentioned positive electrode active material to obtain a slurry-like positive electrode mixture, There is a method of applying a positive electrode current collector, drying and pressing to increase the density.

The configuration of the negative electrode is as described above.

The electric double layer capacitor may include a positive electrode, a negative electrode, and the above-described electrolytic solution.
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 non-activated carbon having a large specific surface area and a conductive agent such as carbon black which imparts electron conductivity. The polarizable electrode can be formed in various ways. For example, a polarizable electrode composed of activated carbon and carbon black can be formed by mixing activated carbon powder, carbon black and a phenolic resin, and after press molding, firing and firing in an inert gas atmosphere and a water vapor atmosphere. 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 may be kneaded in the presence of alcohol to form a sheet, which may be dried to form a polarizable electrode. For example, polytetrafluoroethylene is used as the binder. Alternatively, activated carbon powder, carbon black, a binder and a solvent are mixed to form a slurry, and the slurry is coated on a metal foil of a current collector and dried to form a polarizable electrode integrated with the current collector. it can.

Although a polarizable electrode mainly composed of activated carbon may be used as an electrical double layer capacitor for both electrodes, a nonpolarizable electrode may be used on one side, for example, a positive electrode mainly composed of a battery active material such as metal oxide, and activated carbon A combination of the polarizable electrode and the negative electrode of the main component, the negative electrode mainly of the carbon material capable of reversibly absorbing and desorbing lithium ions, or the negative electrode of lithium metal or lithium alloy and the active carbon as the main component A configuration combining a positive pole is also possible.

Also, in place of or in combination with activated carbon, a carbonaceous material such as carbon black, graphite, expanded graphite, porous carbon, carbon nanotube, carbon nanohorn, ketjen black may be used.

As the non-polarizable electrode, preferably, a carbon material capable of reversibly absorbing and desorbing lithium ions is mainly used, and the carbon material in which lithium ions are occluded is used for the electrode. In this case, a lithium salt is used as the electrolyte. According to the electric double layer capacitor of this configuration, a withstand voltage higher than 4 V can be obtained.

The solvent used for preparation of the slurry in the preparation of the electrode is preferably one which dissolves the binder, and according to the type of binder, N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, phthalate The acid dimethyl, ethanol, methanol, butanol or water are chosen accordingly.

Examples of 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-based activated carbon or phenol resin-based activated carbon in that a large capacity can be obtained. Further, as the activation treatment method of activated carbon, there are a steam activation treatment method, a molten KOH activation treatment method and the like, and it is preferable to use activated carbon by the molten KOH activation treatment method in that a larger capacity can be obtained.

Preferred conductive agents used for the polarizable electrode include carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, metal fibers, conductive titanium oxide and ruthenium oxide. The mixing amount of the conductive agent such as carbon black used for the polarizable electrode is 1 to 10% of the total amount with the activated carbon so as to obtain good conductivity (low internal resistance) or because the capacity of the product decreases if it is too large. It is preferable to set it as 50 mass%.

In addition, as activated carbon used for the polarizable electrode, activated carbon having an average particle diameter of 20 μm or less and a specific surface area of 1,500 to 3,000 m ² / g is used so that a large capacity and low internal resistance electric double layer capacitor can be obtained. Is preferred. In addition, as preferable carbon materials for constituting an electrode composed mainly of a carbon material capable of reversibly absorbing and desorbing lithium ions, natural graphite, artificial graphite, graphitized mesocarbon small spheres, graphitized whiskers, gas layer Examples thereof include grown carbon fibers, baked products of furfuryl alcohol resin, and baked products of novolac resin.

The current collector may be any one that is chemically and electrochemically corrosion resistant. Stainless steel, aluminum, titanium or tantalum can be preferably used as the current collector of the polarizable electrode mainly composed of activated carbon. Among these, stainless steel or aluminum is a particularly preferable material in terms of both the properties and the cost of the obtained electric double layer capacitor. Preferably, stainless steel, copper or nickel is used as a current collector of an electrode composed mainly of a carbon material capable of reversibly absorbing and desorbing lithium ions.

In addition, in order to occlude lithium ions in advance in a carbon material capable of reversibly absorbing and desorbing lithium ions, (1) a powdery lithium is mixed with a carbon material capable of reversibly absorbing and desorbing lithium ions (2) A lithium foil is placed on an electrode formed of a carbon material capable of reversibly absorbing and desorbing lithium ions and a binder, and the electrode is a lithium salt in a state of being in electrical contact with the electrode. Lithium is ionized by immersing in a molten electrolyte and lithium ions are incorporated into the carbon material, (3) formed by the carbon material and the binder capable of reversibly absorbing and desorbing lithium ions The electrode is placed on the negative side, lithium metal is placed on the positive side, and it is immersed in a non-aqueous electrolyte solution using lithium salt as the electrolyte, and a carbon material is electrochemically supplied by passing an electric current. 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 above electric double layer capacitor can also be in these types. .

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

As the separator, those of conventionally known materials and constitutions can be used. For example, polyethylene porous membrane, polypropylene fiber or glass fiber, non-woven fabric of cellulose fiber, etc. may be mentioned.

In addition, a laminate type electric double layer capacitor in which sheet-like positive and negative electrodes are stacked via an electrolytic solution and a separator by a known method, or a gasket is fixed to make the positive and negative electrodes coin-shaped through the electrolytic solution and the separator. A coin-type electric double layer capacitor can also be configured.

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

Next, the present invention will be described by way of examples, but the present invention is not limited to only these examples.

ａ−２：βＦＧＢＬ

The abbreviations described in Table 1 and Table 2 respectively represent the following compounds.
a-1: α FGBL

a-2: β FGBL

b-1: CF ₃ CH ₂ OCOOCH ₃
b-2: CF ₃ CH ₂ OCOOC ₂ H ₅
b-3: CF ₃ CH ₂ OCOOCH ₂ CF ₃
c-1: CF ₃ CH ₂ COOCH ₃
c-2: HCF ₂ COOCH ₃
e-1: monofluoroethylene carbonate (FEC)
f-1: LIBOB
f-2: LIDFOB
f-3: LIDFOP
f-4: LITFOP
g-1: CH ₃ OCH ₂ CH ₂ OCF ₃
g-2: CH ₃ OCH ₂ CH ₂ OCFH ₂
g-3: CH ₃ OCH ₂ CH ₂ OCF ₂ H
g-4: H ₂ CFOCH ₂ CH ₂ OCFH ₂
g-5: HCF ₂ OCH ₂ CH ₂ OCF ₂ H
g-6: CF ₃ OCH ₂ CH ₂ OCF ₃
h-1: CH ₃ OCF ₂ CF ₂ OCH ₃
h-2: CH ₃ OCH ₂ CF ₂ OCH ₃
h-3: CH ₃ OHCHCHFOCH ₃
i-1: H ₂ CFOO COOCH ₃
i-2: CF ₃ OCOOCH ₃
i-3: H ₂ CFOOCOOC ₂ H ₅

Each component is mixed so as to become the composition described in Table 1 in the embodiment and comparative example described in Table 1, to which LiPF ₆ is added so as to have a concentration of 1.0 mol / l, and non-aqueous An electrolytic solution was obtained.

(Fabrication of positive electrode 1)
Active material, conductive material, LiNi _0.5 Mn _1.5 O ₄ as a positive electrode active material, acetylene black as a conductive material, N-methyl-2-pyrrolidone dispersion of polyvinylidene fluoride (PVdF) as a binder, A positive electrode mixture slurry was prepared in which the solid content ratio of the binder was 92/3/5 (mass% ratio). The obtained positive electrode material mixture slurry was uniformly coated on a 20 μm thick aluminum foil current collector, dried, and compression molded using a press to obtain a positive electrode.

(Fabrication of negative electrode)
Artificial graphite powder as negative electrode active material, aqueous dispersion of sodium carboxymethylcellulose as thickener (concentration 1% by mass of sodium carboxymethylcellulose), aqueous dispersion of styrene-butadiene rubber as binder (concentration of styrene-butadiene rubber 50 The solid content ratio of the active material, the thickener, and the binder is 97.6 / 1.2 / 1.2 (mass% ratio) and mixed in a water solvent using The prepared negative electrode mixture slurry was prepared. After apply | coating and drying uniformly to 20-micrometer-thick copper foil, it compressed and formed with the press and was set as the negative electrode.

(Preparation of lithium ion secondary battery)
A battery element was produced by laminating the negative electrode, the positive electrode and the polyethylene separator produced as described above in the order of the negative electrode, the separator and the positive electrode.
The battery element was inserted into a bag made of a laminated film in which both sides of an aluminum sheet (40 μm in thickness) were coated with a resin layer, with the terminals of the positive electrode and the negative electrode protruding. Each solution was poured into a bag and vacuum-sealed to prepare a sheet-like lithium ion secondary battery.

(High temperature cycle characteristic evaluation test)
The secondary battery manufactured above is charged with constant current to constant voltage up to 4.9 V at a current corresponding to 0.5 C at 60 ° C. in a state of being sandwiched and pressurized with a plate (hereinafter referred to as CC / CV charging ) (0.1 C cut) and then discharged to 3 V with a constant current of 0.5 C, making this one cycle, and repeating this until reaching 300 cycles. Then, the cycle capacity retention rate after 300 cycles at 60 ° C. was determined by the following equation.
(Discharge capacity after 300 cycles) / (initial discharge capacity) × 100 = cycle capacity retention rate (%)

The results are shown in Table 1.

Each component is mixed so as to become the composition described in Table 2 in the embodiment and comparative example described in Table 2, to which LiPF ₆ is added so as to have a concentration of 1.0 mol / l, and non-aqueous An electrolytic solution was obtained.

(Fabrication of positive electrode 2)
Active material using LiNi _0.5 Mn _0.3 Co _0.2 O ₂ as a positive electrode active material, acetylene black as a conductive material, N-methyl-2-pyrrolidone dispersion of polyvinylidene fluoride (PVdF) as a binder A positive electrode mixture slurry was prepared, in which the solid content ratio of the conductive material and the binder was 92/3/5 (mass% ratio). The obtained positive electrode material mixture slurry was uniformly coated on a 20 μm thick aluminum foil current collector, dried, and compression molded using a press to obtain a positive electrode.

(Fabrication of negative electrode)
Artificial graphite powder as negative electrode active material, aqueous dispersion of sodium carboxymethylcellulose as thickener (concentration 1% by mass of sodium carboxymethylcellulose), aqueous dispersion of styrene-butadiene rubber as binder (concentration of styrene-butadiene rubber 50 The solid content ratio of the active material, the thickener, and the binder is 97.6 / 1.2 / 1.2 (mass% ratio) and mixed in a water solvent using The prepared negative electrode mixture slurry was prepared. After apply | coating and drying uniformly to 20-micrometer-thick copper foil, it compressed and formed with the press and was set as the negative electrode.

(Preparation of lithium ion secondary battery)
A battery element was produced by laminating the negative electrode, the positive electrode and the polyethylene separator produced as described above in the order of the negative electrode, the separator and the positive electrode.
The battery element was inserted into a bag made of a laminated film in which both sides of an aluminum sheet (40 μm in thickness) were coated with a resin layer with the terminals of the positive electrode and the negative electrode protruding, and then electrolysis was performed with the composition shown in Table 2. Each solution was poured into a bag and vacuum-sealed to prepare a sheet-like lithium ion secondary battery.

(High temperature cycle characteristic evaluation test)
The secondary battery manufactured above is charged with constant current to constant voltage up to 4.4 V at a current corresponding to 0.5 C at 60 ° C. in a state of being sandwiched and pressurized with a plate (hereinafter referred to as CC / CV charging ) (0.1 C cut) and then discharged to 3 V with a constant current of 0.5 C, making this one cycle, and repeating this until reaching 300 cycles. Then, the cycle capacity retention rate after 300 cycles at 60 ° C. was determined by the following equation.
(Discharge capacity after 300 cycles) / (initial discharge capacity) × 100 = cycle capacity retention rate (%)

The results are shown in Table 2.

Claims (8)

An electrolytic solution containing a solvent and a compound (2),
The solvent has a general formula (1):

(Wherein, X ^{11 to} X ^{16 each} independently represent a fluorinated lactone (1) represented by H or F, provided that at least one is F),
The compound (2) is a compound represented by the general formula (2):

(Wherein, 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 ²³ is an integer of 1 to 4, n ²¹ is 0-8 ^{integer, n 22} is 0 or ^{1, Z 21} is a transition metal, III of the periodic table, IV or group V element of.
X ²¹ 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 And the halogenated alkylene group, the arylene group and the halogenated arylene group may have a substituent or a hetero atom in the structure, and when n ²² is 1 and n ²³ is 2 to 4, n ²³ Each X ²¹ may be bonded)
L ²¹ represents 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 The alkylene group, the halogenated alkylene group, the arylene group, and the halogenated arylene group may have a substituent or a hetero atom in the structure, and when n ²¹ is 2 to 8, n ²¹ L ²¹ is Each may combine to form a ring) or -Z ²³ Y ²³ .
Y ²¹ , Y ²² and Z ²³ are each independently O, S, NY ²⁴ , a hydrocarbon group or a fluorinated hydrocarbon group. Y ²³ and Y ²⁴ 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 Arylated aryl group (the alkyl group, the halogenated alkyl group, the aryl group and the halogenated aryl group may have a substituent or a hetero atom in the structure, and when a plurality of Y ²³ or Y ²⁴ exist, May be combined to form a ring))). The electrolytic solution according to claim 1, wherein the solvent contains 11% by volume or more of fluorinated lactone (1). The electrolytic solution according to claim 1 or 2, wherein the solvent further contains at least one compound (a) selected from the group consisting of fluorinated carbonate and fluorinated linear ester. The solvent contains 11 to 90% by volume of fluorinated lactone (1) and 10 to 89% by volume of the compound (a), and the electrolytic solution is 0.01 to 10% by mass with respect to the solvent. The electrolytic solution according to claim 3, comprising the compound (2) of The solvent further contains a compound represented by formula (4):

(Wherein, R ⁴¹ and R ⁴² are independently H, CH ₃ , F, CH ₂ F, CHF ₂ or CF ₃ , R ⁴³ is a C 1 or C 2 non-fluorinated alkyl group or C 1 or C 2 A fluorinated diether (4) represented by the fluorinated alkyl group of 2), the general formula (5):

(Wherein, R f ⁵¹ is independently F or a fluorinated alkyl group having 1 or 2 carbon atoms, R ⁵¹ , R ⁵² and R ⁵³ are independently H, F, 1 or 2 carbon atoms and non-fluorinated A fluorinated diether (5) represented by an alkyl group or a fluorinated alkyl group having 1 or 2 carbon atoms, a compound represented by the general formula (6):

(Wherein, R ⁶¹ represents a non-fluorinated alkyl group having 1 or 2 carbon atoms, or a fluorinated alkyl group having 1 or 2 carbon atoms) fluorinated linear carbonate (6), and a compound represented by the general formula ( 7):

(Wherein, R ⁷¹ represents a non-fluorinated alkyl group having 1 or 2 carbon atoms, or a fluorinated alkyl group having 1 or 2 carbon atoms) fluorinated linear carbonate (7)
The electrolytic solution according to claim 1, 2, 3 or 4 comprising at least one compound (b) selected from the group consisting of An electrochemical device comprising the electrolytic solution according to claim 1, 2, 3, 4 or 5. A lithium ion secondary battery comprising the electrolytic solution according to claim 1, 2, 3, 4 or 5. A module comprising the electrochemical device according to claim 6 or the lithium ion secondary battery according to claim 7.