JP2016001567A - Electrolyte and secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte capable of improving charge/discharge cycle characteristics of a secondary battery, especially cycle characteristics under a high temperature.SOLUTION: An electrolyte is characterized in containing a sulfone compound represented in the following formula (1), and a compound selected from a group consisting of a pyrrole compound, an aniline compound and a furan compound. In the formula (1), Rand Rare each independently a substituted or unsubstituted alkyl group. A carbon atom of Rand a carbon atom of Rmay form a cyclic structure by being bonded to each other through a single bond or a double bond.

Description

  The present invention relates to an electrolytic solution and a secondary battery using the same, and more particularly to an electrolytic solution for a lithium secondary battery capable of improving the cycle characteristics of the lithium secondary battery and a lithium secondary battery using the same.

  With the rapid market expansion of notebook computers, mobile phones, electric vehicles, stationary storage batteries, etc., secondary batteries with high energy density are required from the viewpoint of miniaturization and weight reduction of devices. Examples of a method for increasing the energy density of the lithium secondary battery include a method using an active material having a large capacity, a method for increasing the operating potential of the battery, and a method for improving charge / discharge efficiency. Among them, the method of increasing the operating potential of a battery is an effective means for reducing the size and weight of a battery module used in an electric vehicle or the like because it can provide an assembled battery having a smaller number of series than a conventional assembled battery.

As a positive electrode active material of a lithium secondary battery, a material having an operating potential of 4 V class (average operating potential = 3.6 to 3.8 V: lithium potential) such as lithium cobalt oxide and lithium manganate is used. In such a compound, the expression potential is defined by a redox reaction of Co ions or Mn ions (Co ³⁺ ← → Co ⁴⁺ or Mn ³⁺ ← → Mn ⁴⁺ ).

Further, for example, by using a compound in which Mn of spinel type lithium manganate is substituted with Ni, Co, Fe, Cu, Cr or the like as an active material, 5V class (average operating potential = 4.6 V or more: lithium potential) It is known to show. In such a compound, Mn exists in a tetravalent state, and the operating potential is defined by the oxidation / reduction of the substitution element instead of the oxidation-reduction reaction of Mn. For example, as spinel-type lithium manganate, LiNi _0.5 Mn _1.5 O ₄ has a capacity of 130 mAh / g or more, an average operating potential of 4.6 V or more with respect to Li metal, and a high energy density. It can be expected as a material. In addition, spinel-type lithium manganese oxide has a three-dimensional lithium diffusion path, has superior thermodynamic stability than other compounds, is easy to synthesize, is relatively inexpensive, and has abundant resources. There is also.

  However, when the above-mentioned 4V class or 5V class positive electrode is used, problems such as gas generation or capacity reduction due to decomposition of the electrolytic solution may occur depending on the use conditions of the secondary battery. Such a problem becomes particularly prominent under long-term cycles and high-temperature conditions and when a 5 V class positive electrode is used. In order to prevent decomposition of the electrolytic solution, development of forming a coating on the electrode surface is underway.

  Patent Document 1 discloses a mixture of a dioxide thiophene such as sulfolane and an acyclic sulfone as a solvent for the purpose of forming a film on the negative electrode. Patent Document 2 discloses the inclusion of an electrolytic oxidation polymerization monomer such as pyrrole, aniline, and derivatives thereof and an electrolytic reduction polymerization monomer for the purpose of forming a film on at least one of the positive electrode and the negative electrode.

  On the other hand, as a countermeasure against overcharge, overdischarge, and abnormal temperature rise, a technique is disclosed in which an electrolytic polymerizable monomer such as furan or biphenyl that is polymerized at the positive electrode at a potential difference of 4.5 V or more is previously contained in the electrolytic solution ( For example, Patent Documents 3 to 6). According to the disclosed literature, the oxide polymerized film formed by polymerizing and polymerizing the above-mentioned electropolymerizable monomer is deposited on the positive electrode, thereby increasing the internal resistance of the non-aqueous electrolyte, and the chemistry inside the lithium battery. The reaction is also said to stop.

JP-A-8-241732 JP 2006-216276 A Japanese Patent Laid-Open No. 9-45369 Japanese Patent Laid-Open No. 2002-25615 JP 2006-278106 A JP 2003-297423 A

  However, the technology described in the above-mentioned patent document does not sufficiently satisfy the charge / discharge cycle characteristics required for recent lithium secondary batteries, and further improvement has been demanded. In particular, there has been a demand for further improvement in maintaining the cycle discharge capacity under long-term cycles and high temperature conditions.

  The positive electrode of Patent Document 1 has an average operating potential described in the examples of less than 4.5 V (vs. lithium potential). For example, when a positive electrode operating at a high potential of 4.5 V or higher is used, sulfolane or the like is oxidized. It is difficult to prevent degradation and decrease in cycle discharge capacity.

  The secondary battery containing a substance selected from pyrrole, aniline, furan, and biphenyl proposed in Patent Documents 2 to 5 operates at a high potential because the average operating potential of the positive electrode is less than 4.5 V (vs. lithium potential). When the electrolyte solution containing the additive described in the examples is used using the positive electrode to be used, it is difficult to prevent the cycle discharge capacity from being lowered.

  The present invention has been made in view of the above circumstances, and provides an electrolytic solution and an additive capable of improving the charge / discharge cycle characteristics of a secondary battery, particularly capable of suppressing a decrease in discharge capacity during a charge / discharge cycle. The purpose is to provide.

  One embodiment of the present invention relates to an electrolytic solution containing a sulfone compound represented by the following formula (1) and one or more compounds selected from a pyrrole compound, an aniline compound, and a furan compound.

（式中、Ｒ_１及びＲ_２は、それぞれ独立に、置換または無置換のアルキル基を表し、Ｒ_１の炭素原子とＲ_２の炭素原子が単結合又は二重結合を介して結合し、環状構造を形成していてもよい。）

(Wherein R ₁ and R ₂ each independently represents a substituted or unsubstituted alkyl group, the carbon atom of R _{1 and} the carbon atom of R ₂ are bonded via a single bond or a double bond, and cyclic A structure may be formed.)

  ADVANTAGE OF THE INVENTION According to this invention, the electrolyte solution which can improve the charging / discharging cycling characteristics of a secondary battery can be provided.

It is a figure which shows an example of the cross-section of the secondary battery which concerns on embodiment of this invention.

[Features of the invention]
The electrolytic solution according to the present invention contains a sulfone compound and a compound selected from a pyrrole compound, an aniline compound, and a furan compound. According to the electrolytic solution of the present invention, it is possible to suppress a decrease in capacity after a charge / discharge cycle of the secondary battery.

  The secondary battery according to the present embodiment includes an electrode body including a positive electrode and a negative electrode, an outer package housing the electrode body, and a sulfone compound and a compound selected from a pyrrole compound, an aniline compound, and a furan compound. An electrolyte solution according to the present invention is provided.

[Action]
Although the mechanism of the present invention has not been elucidated in detail, an electrolytic solution according to the present invention containing a compound selected from a pyrrole compound, an aniline compound and a furan compound in addition to a sulfone compound is used as the electrolytic solution. Thus, it is considered that a film derived from the sulfone compound and a compound selected from the pyrrole compound, the aniline compound, and the furan compound is formed on the surface of the positive electrode, and the decomposition of the electrolytic solution component is suppressed.

  Each embodiment of the present invention will be described below. Each figure is a schematic diagram for facilitating the explanation and understanding of the invention, and its shape, dimensions, ratio, etc. are different from the actual device, but these are appropriately determined in consideration of the following explanation and known techniques. The design can be changed.

  A cross-sectional view of the secondary battery according to the present embodiment is shown in FIG. As shown in FIG. 1, the secondary battery according to the present embodiment includes a positive electrode current collector 3 made of a metal such as aluminum foil, and a positive electrode active material layer 1 containing a positive electrode active material provided thereon. It has the negative electrode which consists of the negative electrode current collector 4 which consists of metals, such as a positive electrode and copper foil, and the negative electrode active material layer 2 containing the negative electrode active material provided on it. The positive electrode and the negative electrode are laminated via a separator 5 made of a nonwoven fabric or a polypropylene microporous film so that the positive electrode active material layer 1 and the negative electrode active material layer 2 face each other. The positive electrode and the negative electrode may be wound in a spiral shape with a separator interposed therebetween. This electrode pair is accommodated in a container formed of exterior bodies 6 and 7 such as an aluminum laminate film. A positive electrode tab 9 is connected to the positive electrode current collector 3, a negative electrode tab 8 is connected to the negative electrode current collector 4, and these tabs are drawn out of the container. An electrolytic solution is injected into the container and sealed. It can also be set as the structure where the electrode group by which the several electrode pair was laminated | stacked was accommodated in the container.

  The positive electrode and the negative electrode according to the embodiment of the present invention include a material capable of inserting and extracting lithium ions. The positive electrode and the negative electrode can also include materials that can occlude and release alkali metal ions other than lithium.

  Hereinafter, the electrolytic solution, the positive electrode, the negative electrode, the separator, the exterior member, the positive electrode terminal, and the negative electrode terminal will be described.

(Electrolyte)
In this embodiment, the sulfone compound is represented by the following formula (1) (hereinafter, the “sulfone compound represented by the formula (1)” may be simply referred to as “sulfone compound”).

［式（１）において、Ｒ_１及びＲ_２は、それぞれ独立に、置換または無置換のアルキル基を示す。Ｒ_１の炭素原子とＲ_２の炭素原子が単結合又は二重結合を介して結合し、環状構造を形成していてもよい。］

[In Formula (1), R < ₁ > and R < ₂ > shows a substituted or unsubstituted alkyl group each independently. The carbon atom of R _{1 and} the carbon atom of R ₂ may be bonded via a single bond or a double bond to form a cyclic structure. ]

In sulfone compound represented by formula (1), it is preferable that the carbon number _{n 2} with carbon number _n 1, _{R 2} of _{R 1} is _{1 ≦ n 1 ≦ 12,1 ≦ n} 2 ≦ 12 , respectively, 1 ≦ n ₁ ≦ 6, 1 ≦ n ₂ ≦ 6 are more preferable, and 1 ≦ n ₁ ≦ 3 and 1 ≦ n ₂ ≦ 3 are still more preferable. The alkyl group includes linear, branched, or cyclic groups.

In R ₁ and R ₂ , examples of the substituent include an alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and an isobutyl group), and a C 6-10 carbon atom. An aryl group (for example, a phenyl group, a naphthyl group), a halogen atom (for example, a chlorine atom, a bromine atom, a fluorine atom) etc. are mentioned.

  In one embodiment, the sulfone compound is more preferably a cyclic sulfone compound represented by the following formula (1-1).

［式（１−１）中、Ｒ_３は、置換または無置換のアルキレン基を示す。］

[In Formula (1-1), R ₃ represents a substituted or unsubstituted alkylene group. ]

In R ₃ , the alkylene group preferably has 4 to 9 carbon atoms, and more preferably 4 to 6 carbon atoms.

In R ₃ , examples of the substituent include an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group), halogen atom (for example, chlorine atom, bromine atom, fluorine atom). Atom) and the like.

  The cyclic sulfone compound is more preferably a compound represented by the following formula (1-2).

［式（１−２）中、ｍは１〜６の整数である。］

[In Formula (1-2), m is an integer of 1-6. ]

  In Formula (1-2), m is an integer of 1 to 6, and preferably an integer of 1 to 3.

  Preferred examples of the cyclic sulfone compound represented by the formula (1-1) include tetramethylene sulfone, pentamethylene sulfone, hexamethylene sulfone and the like. Preferred examples of the cyclic sulfone compound having a substituent include 3-methylsulfolane and 2,4-dimethylsulfolane. These materials are compatible with other solvents such as the fluorinated ether compounds described below and have a relatively high dielectric constant, so that they have excellent lithium salt dissolution / dissociation action and are fluorinated. Compared with a sulfone compound, there is an advantage that the wettability (affinity) with the positive electrode mixture is high, and the effect can be obtained with a relatively small content.

  The sulfone compound may be a chain sulfone compound. Examples of the chain sulfone compound include ethyl methyl sulfone, ethyl isopropyl sulfone, ethyl isobutyl sulfone, dimethyl sulfone, and diethyl sulfone. Of these, ethyl methyl sulfone, ethyl isopropyl sulfone, and ethyl isobutyl sulfone are preferable. These materials are compatible with other solvents such as fluorinated ether compounds and have a relatively high dielectric constant, so that they are excellent in the dissolution / dissociation action of lithium salts, and also have a fluorinated sulfone compound and In comparison, there is an advantage that the wettability (affinity) with the positive electrode mixture is high and the effect can be obtained with a relatively small content.

  A sulfone compound can be used individually by 1 type or in mixture of 2 or more types.

  The content of the sulfone compound is preferably 5% by volume or more and 75% by volume or less in the nonaqueous electrolytic solvent, and more preferably more than 5% by volume and 50% by volume or less. In particular, when the below-mentioned furan compound is included in the electrolytic solution, the content of the sulfone compound is preferably more than 5% by volume. If the content of the sulfone compound is too small, the compatibility of the electrolytic solution is reduced. If the content is too high, the viscosity of the electrolytic solution is increased, and the capacity of charge / discharge cycle characteristics at room temperature may be reduced.

  In the present specification, the contents of the nonaqueous electrolytic solvent and the additive are described as values based on the volume (specific gravity) of each compound at room temperature (for example, 10 ° C. to 30 ° C., more specifically 25 ° C.). (However, the temperature at which the electrolyte is actually prepared is not particularly limited).

  In addition, when the positive electrode active material is operated at a high potential of 4.5 V or higher, it is preferable to use a solvent having high oxidation resistance. Examples of the solvent having high oxidation resistance include fluorinated solvents such as fluorinated ethers and fluorinated phosphates. These solvents can be used singly or in combination of two or more.

  In the present embodiment, the fluorinated ether compound is represented by the following formula (2).

［式（２）中、Ｒ_１及びＲ_２は、それぞれ独立して、アルキル基又はフッ化アルキル基を示し、Ｒ_１及びＲ_２のうち少なくとも一方はフッ化アルキル基である。］

[In Formula (2), R ₁ and R ₂ each independently represent an alkyl group or a fluorinated alkyl group, and at least one of R ₁ and R ₂ is a fluorinated alkyl group. ]

In formula (2), the total number of carbon atoms of R ₁ and R ₂ is preferably 10 or less.

  In formula (2), the fluorine atom content in the fluorinated alkyl group is preferably 50% or more, more preferably 60% or more, based on the total of fluorine atoms and hydrogen atoms. When the content of fluorine atoms is large, the voltage resistance is further improved, and even when a positive electrode active material that operates at a potential of 4.5 V or more with respect to lithium is used, the battery capacity deterioration after charge / discharge cycles is more effective. It is possible to reduce it.

Examples of the fluorinated ether compound include CF ₃ OCH ₃ , CF ₃ OC ₂ H ₅ , F (CF ₂ ) ₂ OCH ₃ , F (CF ₂ ) ₂ OC ₂ H ₅ , and CF ₃ (CF ₂ ) CH ₂ O. (CF ₂ ) CF ₃ , F (CF ₂ ) ₃ OCH ₃ , F (CF ₂ ) ₃ OC ₂ H ₅ , F (CF ₂ ) ₄ OCH ₃ , F (CF ₂ ) ₄ OC ₂ H ₅ , F (CF ₂ ) ₅ OCH ₃ , F (CF ₂ ) ₅ OC ₂ H ₅ , F (CF ₂ ) ₈ OCH ₃ , F (CF ₂ ) ₈ OC ₂ H ₅ , F (CF ₂ ) ₉ OCH ₃ , CF ₃ CH ₂ OCH ₃ , CF ₃ CH ₂ OCHF ₂ , CF ₃ CF ₂ CH ₂ OCH ₃ , CF ₃ CF ₂ CH ₂ OCHF ₂ , CF ₃ CF ₂ CH ₂ O (CF ₂ ) ₂ H, HCF ₂ CH ₂ OCH ₃ , H _{(CF 2)} 2 O _{H 2 CH 3, H (CF} 2) 2 OCH 2 CF 3, H (CF 2) 2 CH 2 OCHF 2, H (CF 2) 2 CH 2 O (CF 2) 2 H, H (CF 2) 2 CH ₂ O (CF ₂ ) ₃ H, H (CF ₂ ) ₃ CH ₂ O (CF ₂ ) ₂ H, H (CHF) ₂ CH ₂ O (CF ₂ ) ₂ H, (CF ₃ ) ₂ CHOCH ₃ , (CF ₃ ) ₂ CHCF ₂ OCH ₃ , CF ₃ CHFCF ₂ OCH ₃ , CF ₃ CHFCF ₂ OCH ₂ CH ₃ , CF ₃ CHFCF ₂ CH ₂ OCHF ₂ , CF ₃ CHFCF ₂ OCH ₂ (CF ₂ ) ₂ F, CF ₃ CHFCF _{2 OCH 2 CF 2 CF 2 H,} H (CF 2) 4 CH 2 O (CF 2) 2 H, F (CF 2) 4 CH 2 O (CF 2) such as ₂ H and the like.

  Among the fluorinated ether compounds, a fluorinated ether compound represented by the following formula (2-1) is more preferable.

_{^{X 1 - (CX 2 X 3}} ) n -O- (CX 4 X 5) m -X 6 (2-1)
[In Formula (2-1), n and m are each independently 1 to 8. X ^{1 to} X ⁶ are each independently a fluorine atom or a hydrogen atom. However, at least one of X ^{1 to} X ³ is a fluorine atom, and at least one of X ^{4 to} X ⁶ is a fluorine atom. ]

  The fluorinated ether compound is more preferably a compound represented by the following formula (2-2) from the viewpoint of voltage resistance and compatibility with other electrolytes.

_{^{X 1 - (CX 2 X 3}} ) n -CH 2 O-CX 4 X 5 -CX 6 X 7 -X 8 (2-2)
Wherein (2-2), n is 1 to ^8, X 1 to X ⁸ are each independently a fluorine atom or a hydrogen atom. However, at least one of X ^{1 to} X ³ is a fluorine atom, and at least one of X ^{4 to} X ⁸ is a fluorine atom. ]

In Formula (2-2), when n is 2 or more, a plurality of X ² may be the same or different from each other, and a plurality of X ³ are the same or different from each other. Also good.

  Furthermore, from the viewpoint of voltage resistance and compatibility with other electrolytes, the fluorinated ether compound is more preferably represented by the following formula (2-3).

^{H- (CY 1 Y 2 -CY 3} Y 4) n -CH 2 O-CY 5 Y 6 -CY 7 Y 8 -H (2-3)
[In Formula (2-3), n is 1, 2, 3 or 4. Y ^{1 to} Y ⁸ are each independently a fluorine atom or a hydrogen atom. However, at least one of Y ^{1 to} Y ⁴ is a fluorine atom, and at least one of Y ^{5 to} Y ⁸ is a fluorine atom. ]

In the formula ^(2-3), Y 1 ~Y ^4, when n is 2 or more, ^Y 1 ^{Y 2} where there exist a plurality may be the being the same or different, there exist a plurality ^Y 3 Y ⁴ may be the same as or different from each other.

  The content of the fluorinated ether compound is preferably 15% by volume or more and 90% by volume or less in the nonaqueous electrolytic solvent, more preferably 30% by volume or more and 90% by volume or less, and 40% by volume or more and 90% by volume. % Or less is more preferable. In one embodiment, it may be more preferable that it is 50 volume% or more and 80 volume% or less. By containing the fluorinated ether compound, the viscosity of the electrolytic solution can be lowered, so that the conductivity is further improved and the capacity reduction in the charge / discharge cycle can be suppressed. If the content of the fluorinated ether compound is too large, the dielectric constant of the electrolytic solution decreases, the supporting salt cannot be dissociated, and the capacity may be reduced. In addition, a fluorinated ether compound can be used individually by 1 type or in mixture of 2 or more types.

  In the present embodiment, the fluorinated phosphate ester is represented by the following formula (3).

［式（３）において、Ｒ^１、Ｒ^２、Ｒ^３は、それぞれ独立に、アルキル基またはフッ化アルキル基を示し、これらのうち少なくとも１つがフッ化アルキル基である。］

[In Formula (3), R ¹ , R ² and R ³ each independently represents an alkyl group or a fluorinated alkyl group, and at least one of them is a fluorinated alkyl group. ]

The fluorinated alkyl group is an alkyl group having at least one fluorine atom. In the formula ^(3), the number of carbon atoms in R 1, ^{R 2} and ^{R 3} each independently is preferably 1-3. At least one of R ¹ , R ² and R ³ is preferably a fluorinated alkyl group in which 50% or more of the hydrogen atoms of the corresponding unsubstituted alkyl group are substituted with fluorine atoms. Moreover, all of R ₁ , R ₂ and R ₃ are fluorinated alkyl groups, and 50% or more of the hydrogen atoms of the unsubstituted alkyl group to which R ₁ , R ₂ and R ₃ correspond are substituted with fluorine atoms. More preferred is a fluorinated alkyl group. When the content of fluorine atoms is large, the voltage resistance is further improved, and even when a positive electrode active material that operates at a potential of 4.5 V or more with respect to lithium is used, the battery capacity is further deteriorated after the charge / discharge cycle. This is because it can be reduced. Further, the ratio of fluorine atoms in the substituent containing a hydrogen atom in the fluorinated alkyl group is more preferably 55% or more.

  Although it does not specifically limit as fluorinated phosphate ester, For example, phosphoric acid tris (trifluoromethyl), phosphoric acid tris (pentafluoroethyl), phosphoric acid tris (2,2,2-trifluoroethyl) (TTFP) , Tris phosphate (2,2,3,3-tetrafluoropropyl), tris phosphate (3,3,3-trifluoropropyl), tris phosphate (2,2,3,3,3-pentafluoropropyl) ) Fluorinated alkyl phosphate compounds. Among these, as the fluorinated phosphate compound, tris (2,2,2-trifluoroethyl) phosphate (TTFP) is preferable. Fluorinated phosphates can be used alone or in combination of two or more.

  When the fluorinated phosphate ester is contained, the content of the fluorinated phosphate ester contained in the non-aqueous electrolytic solvent is not particularly limited, but is 0% by volume to 95% by volume in the non-aqueous electrolytic solvent. Preferably, 10 volume% or more and 95 volume% or less are more preferable, and 20 volume% or more and 70 volume% or less are more preferable. When the content of the fluorinated phosphate ester in the nonaqueous electrolytic solvent is 10% by volume or more, the effect of increasing the voltage resistance is further improved. Moreover, the ion conductivity of electrolyte solution improves that the content rate in the nonaqueous electrolytic solvent of fluorinated phosphate ester is 95 volume% or less, and the charge / discharge rate of a battery becomes more favorable.

  Since the fluorinated phosphate ester also has high oxidation resistance, oxidative decomposition of the solvent when a 5V class active material is used can be suppressed. As a result, it is possible to improve the capacity maintenance rate of the charge / discharge cycle and reduce gas generation.

  In this embodiment, it is preferable that electrolyte solution contains a cyclic carbonate as a nonaqueous electrolytic solvent. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC). In addition, some or all of hydrogen in these compounds may be substituted with fluorine. A cyclic carbonate can be used individually by 1 type or in mixture of 2 or more types. EC and PC are preferable because they have a high dielectric constant and excellent electrolyte solubility, and EC is more preferable. When the cyclic carbonate is contained, the content in the non-aqueous solvent is preferably 0.1% by volume or more, more preferably 5% by volume or more, from the viewpoint of increasing the dissociation degree of the supporting salt and the conductivity of the electrolytic solution. 70 volume% or less is preferable and 60 volume% or less is more preferable.

  In the present embodiment, the nonaqueous electrolytic solvent can include a chain carbonate. The chain carbonate is not particularly limited, and examples thereof include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). In addition, some or all of hydrogen in these compounds may be substituted with fluorine. Among these, dimethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, monofluoromethyl methyl carbonate, methyl 2,2,3,3, tetrafluoropropyl carbonate and the like are preferable from the viewpoint of voltage resistance and conductivity. . A chain carbonate can be used individually by 1 type or in combination of 2 or more types. When the chain carbonate is included, the content in the nonaqueous electrolytic solvent is preferably 0.1% by volume or more, more preferably 1% by volume or more, and still more preferably 5% by volume or more. Moreover, 90 volume% or less is preferable, 80 volume% or less is more preferable, and 70 volume% or less is further more preferable.

  In the present embodiment, the nonaqueous electrolytic solvent may contain an aliphatic carboxylic acid ester, γ-lactone, a cyclic ether, a chain ether other than the above, and the like. Examples of the aliphatic carboxylic acid ester include methyl formate, methyl acetate, ethyl propionate, and derivatives thereof (including fluorinated products). Examples of γ-lactone include γ-butyrolactone and its derivatives (including fluorinated products). Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran, and derivatives thereof (including fluorinated products). Examples of the chain ether include 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, and derivatives thereof (including fluorinated products). These can be used individually by 1 type or in mixture of 2 or more types.

  Other nonaqueous electrolytic solvents include, for example, dimethyl sulfoxide, formamide, acetamide, dimethylformamide, dioxolane (eg, 1,3-dioxolane), acetonitrile, propyl nitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxy Methane, dioxolane derivative, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, anisole, N-methylpyrrolidone, and derivatives thereof (including fluorinated compounds) It can also be used.

  In the present embodiment, the electrolytic solution further includes a compound selected from a pyrrole compound, an aniline compound, and a furan compound as an additive.

  A pyrrole compound is an aromatic heterocyclic compound containing nitrogen.

  An aniline compound is a compound obtained by substituting at least part of hydrogen atoms of an aromatic ring of an aromatic hydrocarbon such as benzene with an amino group.

  A furan compound is an aromatic heterocyclic compound containing oxygen.

  In this embodiment, as a pyrrole compound, the pyrrole compound represented by Formula (4) can be mentioned, for example.

（式中、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４およびＲ_５は、それぞれ独立に、水素原子、−Ｒ^ｘまたは−Ａであり、
−Ｒ^ｘは、炭素数１〜１８の直鎖または分岐鎖アルキル基、炭素数２〜１８の直鎖または分岐鎖アルケニル基、炭素数６〜１８のアリール基、炭素数７〜２０のアリールアルキル基、炭素数７〜２０のアルキルアリール基、炭素数２〜１０のアシル基、炭素数１〜６のアルコキシ基、炭素数２〜１０のアルコキシカルボニル基および炭素数３〜１０のアルコキシカルボニルアルキル基よりなる群より選択され、ただし、−Ｒ^ｘの少なくともひとつの水素原子が−Ａで置換されていてもよく、
−Ａは、ヒドロキシル基、カルボキシル基、ハロゲン、アミノ基、ニトロ基、シアノ基、アルデヒド基、イソシアナト基、炭素数６〜１８のアリールスルホニル基、トシル基、シリル基、フリル基、ピロリル基、チオール基、スルホン酸基、ヒドラジド基（−ＣＯ−ＮＨ−ＮＨ_２）、酸ハロゲン基、アミド基およびスルホンアミド基よりなる群より選択され、
ここで、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４からなる群より選ばれる隣接する２つが結合して環を形成していてもよい。）

(Wherein R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently a hydrogen atom, —R ^x or —A;
-R ^x is a straight-chain or branched-chain alkyl group having 1 to 18 carbon atoms, straight-chain or branched-chain alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, arylalkyl of 7 to 20 carbon atoms Group, an alkylaryl group having 7 to 20 carbon atoms, an acyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, and an alkoxycarbonylalkyl group having 3 to 10 carbon atoms is selected from the group consisting more, provided that at least one of the hydrogen atoms of the -R ^x may be substituted by -A,
-A is hydroxyl group, carboxyl group, halogen, amino group, nitro group, cyano group, aldehyde group, isocyanato group, arylsulfonyl group having 6 to 18 carbon atoms, tosyl group, silyl group, furyl group, pyrrolyl group, thiol Selected from the group consisting of a group, a sulfonic acid group, a hydrazide group (—CO—NH—NH ₂ ), an acid halogen group, an amide group, and a sulfonamide group,
Here, _two adjacent groups selected from the group consisting of R ₁ , R ₂ , R ₃ and R ₄ may be bonded to form a ring. )

In Formula (4), examples of the ring structure formed by bonding two adjacent members selected from R ₁ , R ₂ , R ₃ and R ₄ include an aromatic hydrocarbon ring (for example, a benzene ring) Etc.), saturated or unsaturated aliphatic hydrocarbon rings, and heterocycles in which one or more of the carbon atoms forming these rings are substituted with heteroatoms (eg, oxygen, nitrogen, sulfur, etc.). These ring structures are preferably 4- to 10-membered rings, and more preferably 5- to 8-membered rings. Examples of the polycyclic pyrrole compound represented by the formula (4) include a condensed compound of a pyrrole ring and an aromatic ring such as indole; a condensed compound of a pyrrole ring and another heterocyclic ring such as thienopyrrole; and pyrrole. Examples thereof include a condensed compound of a ring and a pyrrole ring.

In Formula (4), R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently a hydrogen atom, —R ^x or —A, where —R ^x is from 1 to A linear alkyl group having 10 carbon atoms, a branched alkyl group having 3 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkylaryl group having 7 to 13 carbon atoms, and 2 to 2 carbon atoms An acyl group of 8 or an alkoxycarbonyl group having 2 to 6 carbon atoms, provided that at least one hydrogen atom of —R ^x may be substituted with —A, and —A is a halogen (eg, bromine, iodine) , Chlorine, fluorine), amino group, nitro group, sulfonamide group, thiol group, cyano group, aldehyde group, arylsulfonyl group having 6 to 12 carbon atoms, tosyl group, silyl group or furyl group.

In one embodiment, it is particularly preferable that R ₁ and R ₄ are hydrogen atoms from the viewpoint of reactivity.

For example, R ₁ and R ₄ are hydrogen atoms, and R ₂ , R _3, and R ₅ are each independently a hydrogen atom, —R ^x, or —A, where —R ^x is 1 carbon atom A linear alkyl group having 5 to 5 carbon atoms, a branched alkyl group having 3 to 5 carbon atoms, a phenyl group, an alkylphenyl group having 7 to 10 carbon atoms, or an acyl group having 2 to 6 carbon atoms, and -A is a halogen (bromine , Iodine, chlorine, etc.), amino group, cyano group, aldehyde group, phenylsulfonyl group, tosyl group, silyl group or furyl group. All of R _{1 to} R ₅ may be hydrogen atoms.

In one embodiment, R ₁ and R ₄ are hydrogen atoms, and R ₂ , R ₃ and R ₅ are each independently a hydrogen atom, —R ^x or —A, where —R ^x is A linear alkyl group having 1 to 3 carbon atoms, a branched alkyl group having 3 to 5 carbon atoms, a phenyl group, a methylphenyl group or an acetyl group, and -A is a halogen (bromine, iodine, chlorine, etc.) or an amino group It is more preferable that

  In one embodiment, the pyrrole compound is more preferably a monocyclic compound (a compound in which the pyrrole ring does not constitute a condensed ring).

  Examples of pyrrole compounds include, for example, pyrrole (1H-pyrrole); pyrrole rings such as 3-acetylpyrrole, 3-acetyl-1-methylpyrrole, pyrrole-3-carboxylic acid, and 3-acetyl-1-tosylpyrrole. Compounds having a substituent at the 3-position; 1-methylpyrrole, 1-ethylpyrrole, 1- (2-cyanoethyl) pyrrole, 1-phenylpyrrole, 1-tosylpyrrole, 1- (2-hydroxyethyl) pyrrole, 1- (3-hydroxypropyl) pyrrole, 1- (triisopropylsilyl) pyrrole, 1- (phenylsulfonyl) pyrrole, 1- (4-chlorophenyl) -1H pyrrole, 1- (4-iodophenyl) pyrrole, 4- (1H -Pyrrol-1-yl) phenol, 1- {3- (bromomethyl) phenyl} -1H-pyrrole 1- {4- (bromomethyl) phenyl} -1H-pyrrole, 1- (3-isocyanatophenyl) -1H-pyrrole, 3- (1H-pyrrol-1-yl) aniline, 4- (1H-pyrrole-1 -Yl) aniline, 4- (1H-pyrrol-1-yl) benzaldehyde, 2- (1H-pyrrol-1-yl) benzoic acid, 3- (1H-pyrrol-1-yl) benzoic acid, 4- (1H -Pyrrol-1-yl) benzylamine, {2- (1H-pyrrol-1-yl) phenyl} methanol, {4- (1H-pyrrol-1-yl) phenyl} methanol, pyrrole such as N-furfurylpyrrole Compounds having a substituent at the 1-position of the ring; 2-ethylpyrrole, 2,4-dimethylpyrrole, 2-acetylpyrrole, 2-propionylpyol, 3-acetyl-2,4- Methylpyrrole, pyrrole-2-carbonitrile, N-methylpyrrole-2-carboxaldehyde, pyrrole-2-carboxylic acid, 1-methylpyrrole-2-carboxylic acid, 2-acetyl-1-methylpyrrole, 1- (2 -Aminophenyl) pyrrole, 1,5-dimethyl-2-pyrrolecarbonitrile, ethyl 2,4-dimethylpyrrole-3,5 dicarboxylate, ethyl 3,5-dimethyl-1H-pyrrolecarboxylate, 1- (4- And a compound having a substituent at the 2-position of the pyrrole ring, such as chlorophenyl) -1H-pyrrole-2-carbaldehyde and 1H-pyrrole-2-carboxylic hydrazide. Furthermore, indole; 4-methyl-4H-thieno {3,2-b} pyrrole-5-carbaldehyde, 6H-thieno {2,3-b} pyrrole-5-carboxylate, 4-methyl-4H- Thieno {3,2-b} pyrrole-5-carboxylic acid, 4H-thieno {3,2-b} pyrrole-5-carboxylic acid, {4-methyl-4H-thieno {3,2-b} pyrrole-5 -Ile} thienopyrrole such as methanol; pyrrole ring condensed polycyclic aromatic compound such as polypyrrole can be mentioned. Moreover, the pyrrole compound which has a heterocyclic ring may be sufficient.

  Examples of more preferable pyrrole compounds include pyrrole (1H-pyrrole), 3-acetylpyrrole, 3-acetyl-1-methylpyrrole, 3-acetyl-1-tosylpyrrole, 1- (1H-pyrrol-3-yl). Ethan-1-one, 1-methylpyrrole, 1-ethylpyrrole, 1- (2 cyanoethyl) pyrrole, 1-phenylpyrrole, 1-tosylpyrrole, 1- (triisopropylsilyl) pyrrole, 1- (phenylsulfonyl) pyrrole 1- (4-chlorophenyl) -1H pyrrole, 1- (4-iodophenyl) pyrrole, 4- (1H-pyrrol-1-yl) phenol, 1- {3- (bromomethyl) phenyl} -1H-pyrrole, 1- {4- (Bromomethyl) phenyl} -1H-pyrrole, 1- (3-isocyanatophenyl) -1H Pyrrole, 3- (1H-pyrrol-1-yl) aniline, 4- (1H-pyrrol-1-yl) aniline, 4- (1H-pyrrol-1-yl) benzaldehyde, 4- (1H-pyrrol-1-yl) Yl) benzylamine, N-furfurylpyrrole, and the like.

  Further, as the pyrrole compound, a pyrrole oligomer obtained by polymerizing 2 to 50, preferably 2 to 20, more preferably 2 to 10 monomers of these monocyclic or polycyclic pyrrole compounds may be used. .

  In this embodiment, a pyrrole compound can be used individually by 1 type or in combination of 2 or more types. From the viewpoint of film formation on the surface of the positive electrode, it contains at least one pyrrole compound that is oxidized at a potential lower than the decomposition potential of other nonaqueous electrolytic solvents and can form a conductive polymer film on the positive electrode. Is preferred.

  In this embodiment, as an aniline compound, the aniline compound represented by Formula (5) can be mentioned, for example.

（式中、
Ｒ_１及びＲ_２は、それぞれ独立に、水素原子または−Ｒ^ｘであり、
Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６およびＲ_７は、それぞれ独立に、水素原子、−Ｒ^ｘ、−Ａまたは−Ｚ−Ｂであり、
−Ｒ^ｘは、炭素数１〜２０の直鎖または分岐鎖アルキル基、炭素数３〜１２のシクロアルキル基、炭素数２〜１８の直鎖または分岐鎖アルケニル基、炭素数６〜１８のアリール基、炭素数７〜２０のアリールアルキル基、炭素数７〜２０のアルキルアリール基、炭素数２〜１０のアシル基、炭素数１〜６のアルコキシ基、炭素数２〜１０のアルコキシカルボニル基および炭素数３〜１０のアルコキシカルボニルアルキル基よりなる群より選択され、ただし、−Ｒ^ｘの少なくともひとつの水素原子が−Ａで置換されていてもよく、
−Ａは、ヒドロキシル基、カルボキシル基、ハロゲン、アミノ基、シアノ基、ニトロソ基、ニトロ基、アルデヒド基、スルホン酸基、ヒドラジド基、酸ハロゲン基、アミド基、スルホンアミド基およびチオール基よりなる群より選択され、
−Ｚ−は、直接結合、または、炭素数１〜５のアルキレン基、炭素数２〜５のアルケニレン基、スルホニル基、アゾ基およびエーテル基よりなる群より選ばれる２価の基であり、
−Ｂは、炭素数６〜１２のアリール基、アミノフェニル基、または、ヘテロ原子として酸素、窒素、硫黄およびホウ素から選ばれる一つ以上を有する複素環基であり、
ここで、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６およびＲ_７からなる群より選ばれる隣接する２つが結合して環を形成していてもよい。）

(Where
R ₁ and R ₂ are each independently a hydrogen atom or —R ^x ;
R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently a hydrogen atom, —R ^x , —A or —ZB;
-R ^x is a straight-chain or branched-chain alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, straight-chain or branched-chain alkenyl group having 2 to 18 carbon atoms, aryl having 6 to 18 carbon atoms A group having 7 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, an acyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, and is selected from the group consisting of alkoxycarbonylalkyl group having 3 to 10 carbon atoms, provided that at least one of the hydrogen atoms of the -R ^x may be substituted by -A,
-A is a group consisting of hydroxyl group, carboxyl group, halogen, amino group, cyano group, nitroso group, nitro group, aldehyde group, sulfonic acid group, hydrazide group, acid halogen group, amide group, sulfonamide group and thiol group More selected,
-Z- is a direct bond or a divalent group selected from the group consisting of an alkylene group having 1 to 5 carbon atoms, an alkenylene group having 2 to 5 carbon atoms, a sulfonyl group, an azo group and an ether group,
-B is an aryl group having 6 to 12 carbon atoms, an aminophenyl group, or a heterocyclic group having one or more selected from oxygen, nitrogen, sulfur and boron as a hetero atom;
Here, two adjacent groups selected from the group consisting of R ₃ , R ₄ , R ₅ , R ₆ and R ₇ may be bonded to form a ring. )

In the formula (5), the “heterocyclic group having one or more selected from oxygen, nitrogen, sulfur and boron as a hetero atom” represented by —B is a 5- to 8-membered monocyclic heterocyclic ring, or A group formed from a structure in which the two rings are condensed is preferable. For example, a monophorino group, pyridinyl group, piperazino group, furyl group, thiophenyl group, pyrrolyl group, triazolyl group, imidazolyl group, oxazolyl group, thiazolyl Group, purinyl group and dioxaborolanyl group. One or more hydrogen atoms of these heterocyclic groups may be substituted with an alkyl group having 1 to 3 carbon atoms. Further, at least one hydrogen atom of an amino phenyl group represented by -B may be substituted by -R ^x or -A.

In the formula (5), examples of the ring structure formed by bonding two adjacent members selected from R ₃ , R ₄ , R ₅ , R ₆ and R ₇ include aromatic hydrocarbon rings (for example, , Benzene rings, etc.), saturated or unsaturated aliphatic hydrocarbon rings, and heterocycles in which one or more of the carbon atoms forming these rings are replaced by heteroatoms (eg, oxygen, nitrogen, sulfur, etc.). It is done. These ring structures are preferably 4- to 10-membered rings, and more preferably 5- to 8-membered rings. Examples of the polycyclic aniline compound represented by the formula (5) include a condensed compound of an aniline ring and an aromatic hydrocarbon ring (including an aniline ring); a condensed compound of an aniline ring and a heterocyclic ring, and the like. .

In Formula (5), R ₁ and R ₂ are each independently a hydrogen atom or —R ^x , and R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently a hydrogen atom, — is R ^x or -A, wherein, -R ^x is a linear alkyl group having 1 to 18 carbon atoms, branched chain alkyl group having 3 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, 6 carbon atoms Preferably an aryl group having -12 carbon atoms, an arylalkyl group having 7-15 carbon atoms, an acyl group having 2-8 carbon atoms, an alkoxy group having 1-6 carbon atoms, or an alkoxycarbonyl group having 2-6 carbon atoms, A is more preferably a halogen (for example, bromine, iodine, chlorine, fluorine), an amino group, a nitro group, a thiol group, or a sulfonamide group.

In one embodiment, it is particularly preferred that R ₁ , R ₂ , R ₃ , R ₅ and R ₇ are hydrogen atoms. For example, R ₁ , R ₂ , R ₃ , R ₅ and R ₇ are hydrogen atoms, and R ₄ and R ₆ are each independently a hydrogen atom, —R ^x or —A, where —R ^x is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an acyl group having 2 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms, and -A is a halogen or an amino group. More preferably. All of R _{1 to} R ₇ may be hydrogen atoms.

In another embodiment, a compound in which at least one of R ₁ and R ₂ represents a group other than a hydrogen atom is more preferable. For example, at least one of R ₁ and R ₂ is a linear alkyl group having 1 to 16 carbon atoms, a branched alkyl group having 3 to 8 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a phenyl group, or 7 to 7 carbon atoms. It is preferably a 10 phenylalkyl group or an aminoalkyl group having 1 to 5 carbon atoms. In this case, it is particularly preferable that R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are hydrogen atoms.

  In one embodiment, the aniline compound is more preferably a monocyclic compound.

  Examples of compounds include aniline (phenylamine); N-methylaniline, N-ethylaniline, Nn-propylaniline, N-iso-propylaniline, Nn-butylaniline, N-iso-butylaniline, N-tert-butylaniline, Nn-pentylaniline, N-iso-pentylaniline, N-tert-pentylaniline, Nn-hexylaniline, N-iso-hexylaniline, N-tert-hexylaniline, N -Cyclohexylaniline, 2-methyl-N-cyclohexylaniline, Nn-heptylaniline, N-iso-heptylaniline, N-tert-heptylaniline, N-cycloheptylaniline, Nn-octylaniline, N-iso -Octylaniline, N-tert-octylua Phosphorus, Nn-nonanylaniline, N-iso-nonanylaniline, N-tert-nonanylaniline, Nn-decylaniline, N-iso-decylaniline, N-tert-decylaniline, Nn -Undecylaniline, N-iso-undecylaniline, N-tert-undecylaniline, Nn-dodecylaniline, N-iso-dodecylaniline, N-tert-dodecylaniline, Nn-tridecylaniline, N-iso-tridecylaniline, N-tert-tridecylaniline, Nn-tetradecylaniline, N-iso-tetradecylaniline, N-tert-tetradecylaniline, Nn-pentadecylaniline, N- iso-pentadecylaniline, N-tert-pentadecylaniline, N-allyla Phosphorus, N-cyclohexylaniline, N, N-dimethylaniline, 4-tert-butyl-N, N-dimethylaniline, 4-tert-butyl-phenylphenylaniline, N, N-diethylaniline, N, N-di- n-propylaniline, N, N-di-iso-propylaniline, N, N-di-n-butylaniline, N, N-di-iso-butylaniline, N, N-di-tert-butylaniline, N , N-di-n-pentylaniline, N, N-di-iso-pentylaniline, N, N-di-tert-pentylaniline, N, N-di-n-hexylaniline, N, N-di-iso -Hexylaniline, N, N-di-tert-hexylaniline, N, N-di-n-heptylaniline, N, N-di-iso-heptylaniline, N, N-di -Tert-heptylaniline, N, N-di-n-octylaniline, N, N-di-iso-octylaniline, N, N-di-tert-octylaniline, N-methyl-N-neopentylaniline, N -Methyl-N-cyclohexylaniline, N, N-dimethyl-3-nitroaniline, N-ethyl-N-hydroxyethylaniline, N, N-bis (cyanoethyl) aniline, N, N-dibutylaniline, 3-chloro- N-methylaniline, 2,2 ′-(phenylimino) diethanol, 3-bromo-N-methylaniline, 4- (2,3-dihydroimidazo [2,1-b] [1,3] thiazole-6 Yl) aniline, N-butyl-N- (3-phenylpropyl) aniline, N-propyl-N- (1-hydroxypropyl) aniline, N, N Bis (3-phenylpropyl) aniline, N-ethyl-N- (3-hydroxypropyl) aniline, N-methyl-N- (3-methylphenyl) benzenepropanamine, N-butyl-N- (hydroxypropyl) aniline N- (dihydroxypropyl) aniline, 4- (1-methylethyl) -N-phenylbenzeneaniline, N-methyl-N-ethylaniline, N- (2-phenylethyl) aniline, N-ethyl-N, N '-Dimethyl-N-phenyl-1,2-ethanediamine, N-benzyl-N-ethylaniline, α-methylbenzylphenylamine; 3-ethylaniline, m-toluidine, m-aminophenol, m-chloroaniline, 3-bromoaniline, m-fluoroaniline, m-iodoaniline, m-anisidine, m-nitro Aniline, m-aminobenzenesulfonic acid, 3- (1H-imidazol-1-ylmethyl) aniline, 3- (methylmercapto) aniline, 3- (4-methylpiperazin-1-yl) aniline, 3- (1-methyl -1H-pyrazol-5-yl) aniline, 3- (4-methyl-4H-1,2,4-triazol-3-yl) aniline, 3-thien-3-ylaniline, 3- (1H-1,2, , 4-Triazol-1-yl) aniline, 3- (trifluoromethoxy) aniline, 3- (4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl) aniline, 3- (Morpholinosulfonyl) aniline, 3-morpholinoin-4-ylaniline, 3- (morpholin-4-ylmethyl) aniline, 5- (3-aminophenyl) oxazol 3-pyridin-3-ylaniline, 3-pyridin-4-ylaniline, 3- (pyridin-2-yloxy) aniline, 3- (1H-1,2,4-triazol-1-ylmethyl) aniline, 3- ( Pyrrolidin-1-inmethyl) aniline, 3- (1H-pyrrol-1-yl) aniline, 3-pyrimidin-2-ylaniline, 3- (piperidin-1-ylmethyl) aniline, 3,5-dimethylaniline, 3,5 -Dichloroaniline, 3,5-difluoroaniline, 3,5-dimethoxyaniline, 3,5-bis (trifluoromethyl) aniline, 3- (2-methyl-1H-imidazol-1-yl) aniline, 3- ( 5-methyl-1,2,4-oxadiazol-3-yl) aniline), 3-amino-N, N-diethylaniline; Tyraniline, o-aminophenol, o-anisidine, o-ethylaniline, o-chloroaniline, o-phenetidine, 2-bromoaniline, 2-fluoroaniline, 2-iodoaniline, 2- (1-piperidino) aniline, 2 , 6-Diisopropylaniline, 2- (2-methyl-1,3-thiazol-4-yl) aniline, p-toluidine, p-ethylaniline, p-butylaniline, p-pentylaniline, p-phenetidine, p- Bromoaniline, p-chloroaniline, p-fluoroaniline, p-aminophenol, p-aminoazobenzene, p-anisidine, p-nitroaniline, 4- (2-furyl) aniline, 4- (1H-imidazole-1- Ylmethyl) aniline, 4- (tetrahydropyran-4-yloxy) aniline 4- (1H-pyrrol-1-yl) aniline, 4- (1H-1,2,4-triazol-1-yl) aniline, 4- (1H-1,2,4-triazol-1-ylmethyl) aniline 4-butoxyaniline, 4-phenoxyaniline, 4-isopropylaniline, 4-monomorpholinoaniline, 4- (morpholinosulfonyl) aniline, 4-tert-butylaniline, 4- (trifluoromethoxy) aniline, 4- Vinylaniline, 4-pyrimidin-2-ylaniline, 4-octyloxyaniline, 4- (methylmercapto) aniline, 4- (4-methylpiperazino) aniline, 4- (4,4,5,5-tetramethyl-1, 3,2-dioxaboran-2-yl) aniline, 4-chloro-N-methylaniline, 4-fluoro-N-methylanily , 4-hexyloxyaniline, 4- (morpholinomethyl) aniline, sulfanilic acid, 4,4′-diaminodiphenylsulfone, 4,4′-thiodianiline, 4,4′-azodianiline, N, N-diethyl-p- Phenylenediamine, 4-bromo-N, N-dimethylaniline, N, N-dimethyl-4-nitroaniline, N, N-dimethyl-4-nitrosoaniline, N, N-dimethyl-4,4′-azoaniline, 2 , 4-dimethylaniline, 2-methoxy-4-nitroaniline, 4-methoxy-2-methylaniline, 4-bromo-2-fluoroaniline, 4-bromo-2-methoxyaniline, 2-nitro-p-anisidine, 2,4-dichloroaniline, 2,4-dinitroaniline, 4-methyl-2-nitroaniline, 2,4-difluoroa Phosphorus, 2,5-dimethoxyaniline, 2,5-xylidine, 2,5-dichloroaniline, 2,5-dibromoaniline, 2-methoxy-5-methylaniline, 2-fluoro-5-nitroaniline, 5-chloro 2-hydroxyaniline, 5-chloro-2-methylaniline, 5-chloro-2-nitroaniline, 5-fluoro-2-methylaniline, 2,6-diisopropyl-N, N-dimethylaniline, 2,6- Xylidine, 2-chloro-6-methylaniline, 2,6-dichloroaniline, 2-methyl-6-nitroaniline, 3,4-xylidine, 4-chloro-3-nitroaniline, 4-fluoro-3-nitroaniline 3,4-dichloroaniline, 5-nitro-o-toluidine, 2,3-dimethylaniline, 2,3-dichloroaniline, p, '-Methylenedianiline, 2,6-dichloro-4-nitroaniline, 4,5-dimethyl-4-nitroaniline, 4,4'-methylenebis (N, N-dimethylaniline), 3,4,5-tri Aniline ring condensed polycycle such as methoxyaniline, N, N-dipropyl-m-toluidine, N-ethyl-N- (3-methylphenyl) benzenepropanamine, 3,4, -methylenedioxy-N-ethylamine, polyaniline Aromatic compounds can be mentioned. Further, it may be an aniline compound having a heterocycle such as 3,4- (methylenedioxy) aniline.

  As more preferred aniline compounds, aniline (phenylamine), N-methylaniline, N-ethylaniline, Nn-propylaniline, Nn-butylaniline, Nn-pentylaniline, Nn- Hexylaniline, Nn-heptylaniline, Nn-octylaniline, Nn-nonanylaniline, Nn-decylaniline, Nn-undecylaniline, Nn-dodecylaniline, Nn -Tridecylaniline, Nn-tetradecylaniline, Nn-pentadecylaniline, N-allylaniline, N, N-dimethylaniline, N, N-diethylaniline, N, N-di-n-propylaniline N, N-di-n-butylaniline, N, N-di-n-pentylaniline, N, N-di-n-hexylaniline, N- Tyl-N-neopentylaniline, N, N-dibutylaniline, N-butyl-N- (3-phenylpropyl) aniline, N, N-bis (3-phenylpropyl) aniline, N-methyl-N-ethylaniline N- (2-phenylethyl) aniline, N-ethyl-N, N′-dimethyl-N-phenyl-1,2-ethanediamine, N-benzyl-N-ethylaniline, α-methylbenzylphenylamine, 2 , 3-dimethylaniline and the like.

  Furthermore, as the aniline compound, an aniline oligomer obtained by polymerizing 2 to 50, preferably 2 to 20, more preferably 2 to 10 monomers of these monocyclic or polycyclic aniline compounds may be used. .

  In this embodiment, an aniline compound can be used individually by 1 type or in combination of 2 or more types. From the viewpoint of film formation on the positive electrode surface, it contains at least one aniline compound that can be oxidized at a potential lower than the decomposition potential of other nonaqueous electrolytic solvents and can form a conductive polymer film on the positive electrode. Is preferred.

  In this embodiment, as a furan compound, the furan compound represented by Formula (6) can be mentioned, for example.

（式中、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４は、それぞれ独立に、水素原子、−Ｒ^ｘまたは−Ａであり、
−Ｒ^ｘは、炭素数１〜１８の直鎖または分岐鎖アルキル基、炭素数２〜１８の直鎖または分岐鎖アルケニル基、炭素数６〜１８のアリール基、炭素数７〜２０のアリールアルキル基、炭素数７〜２０のアルキルアリール基、スチリル基、炭素数９〜１１のアルキルスチリル基、炭素数２〜１０のアシル基、炭素数１〜６のアルコキシ基、炭素数２〜１０のアルコキシカルボニル基および炭素数３〜１０のアルコキシカルボニルアルキル基よりなる群より選択され、ただし、−Ｒ^ｘの少なくともひとつの水素原子が−Ａで置換されていてもよく、
−Ａは、ヒドロキシル基、カルボキシル基、ハロゲン、アミノ基、ニトロ基、アルデヒド基、ボロン酸基（−Ｂ（ＯＨ）_２）、チオール基、ハロゲン化スルホニル基、フリル基、ハロカルボニル基、スルホン酸基、ヒドラジド基、酸ハロゲン基、アミド基およびスルホンアミド基よりなる群より選択され、
ここで、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４からなる群より選ばれる隣接する２つが結合して環を形成していてもよい。）

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, —R ^x or —A;
-R ^x is a straight-chain or branched-chain alkyl group having 1 to 18 carbon atoms, straight-chain or branched-chain alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, arylalkyl of 7 to 20 carbon atoms Group, alkyl aryl group having 7 to 20 carbon atoms, styryl group, alkyl styryl group having 9 to 11 carbon atoms, acyl group having 2 to 10 carbon atoms, alkoxy group having 1 to 6 carbon atoms, alkoxy having 2 to 10 carbon atoms is selected from the group consisting of alkoxycarbonylalkyl group of the carbonyl group and having 3 to 10 carbon atoms, provided that at least one of the hydrogen atoms of the -R ^x may be substituted by -A,
-A is hydroxyl group, carboxyl group, halogen, amino group, nitro group, aldehyde group, boronic acid group (-B (OH) ₂ ), thiol group, halogenated sulfonyl group, furyl group, halocarbonyl group, sulfonic acid Selected from the group consisting of a group, a hydrazide group, an acid halogen group, an amide group and a sulfonamide group;
Here, _two adjacent groups selected from the group consisting of R ₁ , R ₂ , R ₃ and R ₄ may be bonded to form a ring. )

In Formula (6), examples of the ring structure formed by bonding two adjacent members selected from R ₁ , R ₂ , R ₃ and R ₄ include an aromatic hydrocarbon ring (for example, a benzene ring) Etc.), saturated or unsaturated aliphatic hydrocarbon rings, and heterocyclic rings in which one or more of the carbon atoms forming these rings are substituted with heteroatoms (eg, oxygen, nitrogen, sulfur, etc.). These ring structures are preferably 4- to 10-membered rings, and more preferably 5- to 8-membered rings. Examples of the polycyclic furan compound represented by the formula (5) include a condensed compound of a furan ring and an aromatic hydrocarbon ring (for example, benzofuran, dibenzofuran); a condensed ring of a furan ring and an aliphatic hydrocarbon ring. Compound (for example, cycloocta (c) furan, mentofuran); a condensed compound of a furan ring and another heterocyclic ring, and the like.

In Formula (6), R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, —R ^x or —A, where —R ^x is a straight chain having 1 to 10 carbon atoms. Chain alkyl group, branched alkyl group having 3 to 10 carbon atoms, linear or branched alkenyl group having 2 to 10 carbon atoms, aryl group having 6 to 12 carbon atoms, arylalkyl group having 7 to 13 carbon atoms, and styryl group , An alkyl styryl group having 9 to 11 carbon atoms, an acyl group having 2 to 6 carbon atoms, and an alkoxycarbonyl group having 2 to 6 carbon atoms, provided that at least one hydrogen atom of -R ^x is -A It is more preferable that -A is a halogen (for example, bromine, iodine, chlorine, fluorine), an amino group, a thiol group, a nitro group, or a sulfonamide group.

In one embodiment, R ₁ and R ₄ are particularly preferably hydrogen atoms from the viewpoint of reactivity.

For example, R ₁ and R ₄ are hydrogen atoms, and R ₂ and R ₃ are each independently a hydrogen atom, —R ^x or —A, where —R ^x is a straight chain having 1 to 8 carbon atoms. Selected from the group consisting of a chain alkyl group, a branched alkyl group having 3 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, an acyl group having 2 to 6 carbon atoms, a styryl group, and an alkyl styryl group having 9 to 11 carbon atoms it is, however, may be at least one of the hydrogen atoms of the -R ^x substituted by -A, and more preferably -A is halogen (bromine, iodine, chlorine, etc.) or an amino group.

In one embodiment, R ₁ and R ₄ are hydrogen atoms, and R ₂ and R ₃ are each independently a linear alkyl group having 1 to 8 carbon atoms, a branched alkyl group having 3 to 8 carbon atoms, or a phenyl group. , A styryl group, a methylstyryl group or a halogen (bromine, iodine, chlorine, etc.) is particularly preferred.

  In one embodiment, the compound represented by Formula (6) is more preferably a monocyclic compound.

  Examples of furan compounds include furan (oxacyclopentadiene); 3-methyl furan, 3-ethyl furan, 3-n-propyl furan, 3-iso-propyl furan, 3-n-butyl furan, 3-iso-butyl. Furan, 3-n-pentylfuran, 3-iso-pentylfuran, 3-n-hexylfuran, 3-iso-hexylfuran, 3-phenylfuran, dibenzofuran, 1,3-diphenylisobenzofuran, 2,3-benzofuran , Furan such as ethyl 3-furanate, 3-furylboronic acid, 3-bromofuran, 3- (styryl) furan, 3- (3-methylstyryl) furan, dimethyl 3,4-furandicarboxylate, cycloocta (c) furan Compounds having a substituent at the 3-position of the ring; 2-methylfuran, 2-ethylfuran, 2-methoxyfuran 1-benzofuran-5-amine, 1-benzofuran-5-carbaldehyde, 1-benzofuran-5-carboxylic acid, 2,5-furandicarboxylic acid, 2-acetylfuran, mentofuran, 2-furoyl chloride, 1- Benzofuran-2-sulfonyl chloride, furfural, furfuryl alcohol, benzo [b] furan-2-carboxaldehyde, benzo [b] furan-2-carboxylic acid, benzo [b] furan-3-ylacetic acid, 2,3- Dimethylfuran, 2,5-dimethylfuran, 2,2'-methylenebisfuran, 2,5-di-tert-butylfuran, 2,5-dimethoxyfuran, 2,3-dimethylbenzofuran, 2,5-dimethylfuran Compounds having a substituent at the 2-position of the furan ring such as -3-thiol; Furan ring condensed polycyclic aromatization such as polyfuran Mention may be made of things. Moreover, the furan compound which has a heterocyclic ring may be sufficient.

  More preferred furan compounds include furan (oxacyclopentadiene), 3-methyl furan, 3-ethyl furan, 3-n-propyl furan, 3-iso-propyl furan, 3-n-butyl furan, 3-iso-butyl. Furan, 3-n-pentylfuran, 3-iso-pentylfuran, 3-n-hexylfuran, 3-iso-hexylfuran, 3-phenylfuran, 3-bromofuran, 3- (styryl) furan, 3- (3 -Methylstyryl) furan, dibenzofuran, 1,3-diphenylisobenzofuran, 2,3-benzofuran, cycloocta (c) furan and the like.

  Furthermore, as the furan compound, a furan oligomer obtained by polymerizing 2 to 50, preferably 2 to 20, more preferably 2 to 10 monomers of these monocyclic or polycyclic furan compounds may be used. .

  In this embodiment, a furan compound can be used individually by 1 type or in combination of 2 or more types. From the viewpoint of film formation on the positive electrode surface, it contains at least one furan compound that can be oxidized at a potential lower than the decomposition potential of other nonaqueous electrolytic solvents and can form a conductive polymer film on the positive electrode. Is preferred.

  The electrolytic solution includes at least one compound selected from a pyrrole compound, an aniline compound, and a furan compound, and may include two or more. In one embodiment, it is more preferable to include at least one selected from a pyrrole compound, an aniline compound, and a monocyclic furan compound.

  In this embodiment, the total amount of one or more compounds selected from a pyrrole compound, an aniline compound, and a furan compound is generally 0.5 g / L or more with respect to the nonaqueous electrolytic solvent, and 1 g It is preferable to add in the range of / L or more and 100 g / L or less. More preferably, it is 3 g / L or more and 50 g / L or less with respect to a nonaqueous electrolytic solvent, More preferably, it is 5 g / L or more and 30 g / L or less, Especially preferably, it is 20 g / L or less. When the content of the compound selected from the pyrrole compound, the aniline compound and the furan compound is within the above range, in addition to the effect of improving the capacity retention rate in the charge / discharge cycle, there is also an effect of improving the cell swelling.

  In the present embodiment, the ratio of the content of the sulfone compound and the content of the compound selected from the pyrrole compound, aniline compound, and furan compound was selected from the pyrrole compound, aniline compound, and furan compound relative to the sulfone compound (ml). The total content (g) of one or more compounds is generally in the range of 0.0005 to 2 g / ml, preferably in the range of 0.002 to 1 g / ml, and preferably 0.02 to 0.02. The range is more preferably 5 g / ml, and further preferably 0.04 to 0.12 g / ml. When the content of the compound selected from the pyrrole compound, the aniline compound and the furan compound and the ratio of the sulfone compound is in the range of 0.0005 to 2 g / ml, a film having a thickness of several nm to several hundred nm is formed on the positive electrode (or the positive electrode). Cycle characteristics at high temperature are improved by forming on the surface of the active material).

  In the present embodiment, a thiophene compound may be added to a compound selected from a pyrrole compound, an aniline compound, and a furan compound. It is considered that the positive electrode film can be formed more firmly by adding the thiophene compound.

  In the present embodiment, the thiophene compound is an aromatic heterocyclic compound containing sulfur.

  Examples of the thiophene compound include a monocyclic thiophene compound represented by the formula (7).

（式中、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４は、それぞれ独立に、水素原子、炭素数１〜１８の直鎖または分岐鎖アルキル基、炭素数２〜１８のアルケニル基、炭素数６〜１８のアリール基、水酸基、アルコキシ基、アシル基、アルコキシカルボニル基、アルコキシカルボニルアルキル基、アルデヒド基、カルボキシル基、ハロゲン基、酸ハロゲン基、アミノ基、ニトロ基、ヒドラジド基、スルホン酸基、アミド基、スルホンアミド基またはチオール基であり、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４の少なくとも２つが結合して環を形成していてもよい。）

Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, or 6 carbon atoms. ~ 18 aryl group, hydroxyl group, alkoxy group, acyl group, alkoxycarbonyl group, alkoxycarbonylalkyl group, aldehyde group, carboxyl group, halogen group, acid halogen group, amino group, nitro group, hydrazide group, sulfonic acid group, amide A group, a sulfonamide group or a thiol group, and at least two of R ₁ , R ₂ , R ₃ and R ₄ may be bonded to form a ring.)

In Formula (7), R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 10 carbon atoms, or a carbon number. 2 to 10 alkenyl groups, aryl groups having 6 to 12 carbon atoms, acyl groups, alkoxycarbonyl groups, alkoxycarbonylalkyl groups, halogens (eg, bromine, iodine, chlorine, fluorine), amino groups, nitro groups, sulfonamide groups Or it is more preferable that it is a thiol group.

In one embodiment, it is more preferred that R ₁ and R ₄ are hydrogen atoms.

  In the present embodiment, the thiophene compound may be a polycyclic thiophene compound. Examples of the polycyclic thiophene compound include a condensed thiophene compound in which two or more thiophene rings are condensed, and a thiophene ring condensed polycyclic aromatic compound in which a thiophene ring and another aromatic ring are condensed.

  Moreover, these monocyclic and polycyclic thiophene compounds may have a substituent. Although it does not specifically limit as a substituent, One or more hydrogen atoms are respectively independently C1-C18, Preferably a C1-C10 linear or branched alkyl group, C2-C2 18, preferably alkenyl group having 2 to 10 carbon atoms, aryl group having 6 to 18 carbon atoms, preferably 6 to 12 carbon atoms, alkoxy group, acyl group, alkoxycarbonyl group, alkoxycarbonylalkyl group, halogen group, amino group , A nitro group, a thiol group and the like.

  Examples of thiophene compounds include thiophene (thiacyclopentadiene); 3-methylthiophene, 2-methylthiophene, 3-ethylthiophene, 3-propylthiophene, 3-butylthiophene, 3-pentylthiophene, 3-hexylthiophene, 2 Alkylthiophene compounds such as 2,3-dimethylthiophene and 2,5-dimethylthiophene; acylthiophene compounds such as 2-acetylthiophene, 3-acetylthiophene, 2-acetyl-3-methylthiophene and 2-acetyl-5-methylthiophene Alkoxycarbonyl or alkoxycarbonylalkylthiophene compounds such as ethyl 3-thiopheneacetate and methyl 2-thiophenecarboxylate; alkoxythiophene compounds such as 2-methoxythiophene and 3-methoxythiophene Nitrothiophene compounds such as 2-nitrothiophene and 2,3-dinitrothiophene; Aminothiophene compounds such as 3-aminothiophene; 3-fluorothiophene, 2-bromo-3-methylthiophene, 3-bromothiophene, 2-bromothiophene 2,5-dibromothiophene, 3-chlorothiophene, 2-chlorothiophene, halogenated thiophene compounds such as 2,5-dichlorothiophene; 1,4-dithiapentalene, dithieno [3,2-b: 2 ′, 3 ′ -D] condensed thiophene compounds such as thiophene; and thiophene ring condensed polycyclic aromatic compounds such as benzothiophene, dibenzothiophene, benzodithiophene, and benzothienobenzothiophene. Further, it may be a thiophene compound having a heterocycle such as ethylenedioxythiophene.

  More preferable thiophene compounds include thiophene (thiacyclopentadiene), 3-methylthiophene, 3-ethylthiophene, 3-propylthiophene, 3-butylthiophene, 3-pentylthiophene, 3-hexylthiophene, and 3-acetylthiophene. , Ethyl 3-thiophene acetate, 3-aminothiophene, 3-bromothiophene, benzothiophene, benzodithiophene, and ethylenedioxythiophene.

  Further, as the thiophene compound, a thiophene oligomer in which 2 to 50, preferably 2 to 20, more preferably 2 to 10 monomers of these monocyclic or polycyclic thiophene compounds are polymerized may be used. .

  In this embodiment, a thiophene compound can be used individually by 1 type or in combination of 2 or more types. From the viewpoint of film formation on the surface of the positive electrode, it contains at least one thiophene compound that is oxidized at a potential lower than the decomposition potential of other nonaqueous electrolytic solvents and can form a conductive polymer film on the positive electrode. Is preferred.

  The addition amount of the thiophene compound is 0.5 g / L or more in total with the compound selected from the pyrrole compound, aniline compound, and furan compound with respect to the nonaqueous electrolytic solvent, and is 1 g / L or more and 100 g / L or less. It is preferable to add in a range. More preferably, it is 3 g / L or more and 50 g / L or less with respect to a nonaqueous electrolytic solvent, More preferably, it is 5 g / L or more and 30 g / L, Especially preferably, it is 20 g / L or less. When the content of the thiophene compound is within the above range, in addition to the effect of improving the capacity retention rate in the charge / discharge cycle, there is also an effect of improving cell swelling.

  As the ratio of the content of the sulfone compound and the content of the compound selected from the pyrrole compound, aniline compound and furan compound and the thiophene compound in the present embodiment, the compound selected from the pyrrole compound, aniline compound and furan compound The total content (g) of thiophene compound and thiophene compound is generally in the range of 0.0005 to 2 g / ml and in the range of 0.002 to 1 g / ml with respect to the sulfone compound (ml). Preferably, it is in the range of 0.02 to 0.5 g / ml, more preferably in the range of 0.04 to 0.12 g / ml. When the ratio of the compound selected from the pyrrole compound, aniline compound, and furan compound, the thiophene compound (g), and the sulfone compound (ml) is in the range of 0.0005 to 2 g / ml, the thickness is several nm to several hundreds. A film having a thickness of nm is formed on the surface of the positive electrode (or positive electrode active material) to improve the cycle characteristics at high temperature.

  In the present embodiment, the electrolytic solution may further include a cyclic sulfonate ester represented by the following formula (8) as an additive. When the electrolytic solution contains a cyclic sulfonic acid ester, the cyclic sulfonic acid ester forms a film on the surface of the positive electrode or the negative electrode, thereby suppressing the reaction of the electrolytic solution and suppressing the volume expansion.

［式（８）中、Ａ及びＢは、それぞれ独立に、アルキレン基又はフッ化アルキレン基を示す。Ｘは、単結合又は−ＯＳＯ_２−基を示す。］

[In Formula (8), A and B each independently represent an alkylene group or a fluorinated alkylene group. X represents a single bond or -OSO ₂ - a group. ]

  In Formula (8), carbon number of an alkylene group is 1-8, for example, Preferably it is 1-6, More preferably, it is 1-4.

  The fluorinated alkylene group represents a substituted alkylene group having a structure in which at least one hydrogen atom in the unsubstituted alkylene group is substituted with a fluorine atom. In Formula (8), carbon number of a fluorinated alkylene group is 1-8, for example, Preferably it is 1-6, More preferably, it is 1-4.

Incidentally, -OSO ₂ - groups may be either direction.

  In the formula (8), when X is a single bond, the cyclic sulfonate ester is preferably a cyclic monosulfonate ester, and the cyclic monosulfonate ester is preferably a compound represented by the following formula (8-1).

［式（８−１）中、Ｒ_１０１及びＲ_１０２は、それぞれ独立に、水素原子、フッ素原子、又は炭素数１〜４のアルキル基を示す。ｎは０、１、２、３、又は４である。］

[In Formula (8-1), R ₁₀₁ and R ₁₀₂ each independently represent a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms. n is 0, 1, 2, 3, or 4. ]

In the formula (8), when X is a -OSO ₂ -group, the cyclic sulfonic acid ester is a cyclic disulfonic acid ester, and the cyclic disulfonic acid ester is preferably a compound represented by the following formula (8-2).

［式（８−２）中、Ｒ_２０１〜Ｒ_２０４は、それぞれ独立に、水素原子、フッ素原子、又は炭素数１〜４のアルキル基を示す。ｎは１、２、３、又は４である。また、ｎが２以上の場合、複数個存在するＲ_２０３は互いに同一であっても異なっていてもよく、複数個存在するＲ_２０４は、互いに同一であっても異なっていてもよい。］

Wherein _{(8-2), R} 201 ~R ₂₀₄ each independently represent a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 4 carbon atoms. n is 1, 2, 3, or 4. When n is 2 or more, a plurality of R ₂₀₃ may be the same or different, and a plurality of R ₂₀₄ may be the same or different. ]

Examples of the cyclic sulfonate ester include 1,3-propane sultone, 1,2-propane sultone, 1,4-butane sultone, 1,2-butane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,3 -Monosulfonic acid ester such as pentane sultone [when X in formula (8) is a single bond], disulfonic acid ester such as methylenemethane disulfonic acid ester, ethylenemethane disulfonic acid ester [X in formula (8) is- In the case of an OSO ₂ -group] and the like. Among these, 1,3-propane sultone, 1,4-butane sultone, and methylene methane disulfonic acid ester are preferable from the viewpoints of film formation effect, availability, and cost.

  The content of the cyclic sulfonic acid ester in the electrolytic solution is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, and 0.3 to 3% by mass. Is more preferable. When the content of the cyclic sulfonic acid ester is 0.01% by mass or more, a coating can be more effectively formed on the positive electrode surface to suppress decomposition of the electrolytic solution. When the content of the cyclic sulfonic acid ester is 10% by mass or less, the initial capacity close to the theoretical capacity is ensured by charging at 20 ° C. by adjusting the viscosity and conductivity of the electrolytic solution within a more appropriate range. Can do.

In the present embodiment, the nonaqueous electrolytic solution is obtained by dissolving an electrolyte made of a lithium salt in a nonaqueous electrolytic solvent. Examples of the lithium salt is not particularly limited, for example, lithium imide _{salt, LiPF 6, LiAsF 6, LiAlCl} 4, LiClO 4, LiBF 4, LiSbF 6 and the like. Among these, LiPF ₆ and LiBF ₄ are preferable. Examples of the lithium imide salt include LiN (C _k F _{2k + 1} SO ₂ ) (C _m F _{2m + 1} SO ₂ ) (k and m are each a natural number and are preferably 1 or 2 independently). . A lithium salt can be used individually by 1 type, and can also be used in combination of 2 or more type. The concentration of the lithium salt in the electrolytic solution is preferably 0.5 to 1.5 mol / L. By setting the concentration of the lithium salt within this range, it is easy to adjust the density, viscosity, electrical conductivity, and the like to an appropriate range.

(Positive electrode)
The positive electrode according to the present embodiment is not particularly limited. For example, the positive electrode current collector is supported on one or both surfaces of the positive electrode current collector and includes a positive electrode active material, a conductive agent, and a binder. A material layer.

  The positive electrode active material according to the present embodiment is not particularly limited as long as it absorbs and releases lithium ions, but it is preferable to use a positive electrode active material that operates at a potential of 4.5 V or higher.

  The positive electrode active material that operates at a potential of 4.5 V or higher with respect to lithium can be selected, for example, by the following method. First, a positive electrode containing a positive electrode active material and Li metal are placed in a state of facing each other with a separator interposed therebetween, and an electrolytic solution is injected to produce a battery. When charging / discharging is performed at a constant current of, for example, 5 mAh / g per positive electrode active material mass in the positive electrode, a charge / discharge capacity of 10 mAh / g or more per mass of active material is a potential of 4.5 V or more with respect to lithium. Can be a positive electrode active material that operates at a potential of 4.5 V or higher with respect to lithium. Moreover, when charging / discharging is performed at a constant current of 5 mAh / g per positive electrode active material mass in the positive electrode, the charge / discharge capacity per active material mass at a potential of 4.5 V or higher with respect to lithium is 20 mAh / g or higher. It is preferable that it is 50 mAh / g or more, and it is further more preferable that it is 100 mAh / g or more. The shape of the battery can be, for example, a coin type.

  Examples of the positive electrode active material that operates at a potential of 4.5 V or higher include a spinel type, an olivine type, a Si composite oxide, and a positive electrode active material having a layered structure.

  In the present embodiment, for example, a spinel type lithium manganese composite oxide represented by the following formula (9) can be used.

Li _a (M _x Mn _2−xy Y _y ) (O _4−w Z _w ) (9)
[In the formula (9), x is 0 ≦ x ≦ 1.2, preferably 0.4 <x <1.1, and y is 0 ≦ y, preferably 0 ≦ y <0.5. X + y <2, 0 ≦ a ≦ 1.2, and 0 ≦ w ≦ 1. M is a transition metal and includes at least one selected from Co, Ni, Fe, Cr, or Cu, and Y is at least selected from Li, B, Na, Al, Mg, Ti, Si, K, or Ca. 1 type, and Z contains at least one of F and Cl. The compound represented by this can be mentioned.

Examples of the compound represented by the formula (9) include a material represented by the following formula (9-1).

LiNi _x Mn _2-xy A _y O ₄ (9-1)
[In Formula (9-1), 0.4 <x <0.6, 0 ≦ y <0.3, A is at least one selected from Li, B, Na, Mg, Al, Ti, and Si. Including. ]

Examples of materials that operate at a high potential of 4.5 V or higher with respect to lithium include LiNi _0.5 Mn _1.5 O ₄ , LiCoMnO ₄ , LiCrMnO ₄ , LiFeMnO ₄ , LiCu _0.5 Mn _1.5 O _{4, and the} like. Is more preferable. Alternatively, a solid solution of these materials, or a positive electrode active material in which a small amount of Al, Mg, B, Si, Ti, or other metal element is added to these materials may be used.

The olivine-based material has the following formula (10):
LiMPO ₄ (10)
[In Formula (10), M is a transition metal, and preferably includes at least one selected from Fe, Mn, Co, and Ni, and more preferably one of Co and Ni. For example, LiFePO ₄ , LiMnPO ₄ , LiCoPO ₄ , LiNiPO _{4 and the} like can be mentioned. Moreover, in these materials, you may use what substituted a part of transition metal with another element, or substituted the oxygen part with the fluorine. From the viewpoint of high energy density, in the above formula (10), it is preferable that M contains at least one of Co and Ni because it operates at a high potential of 4.5 V or higher with respect to lithium.

The layered material has the following formula (11):
_{Li (Li x M 1-x} -z Mn z) O 2 (11)
[In Formula (11), 0 ≦ x <0.3, 0.3 ≦ z ≦ 0.7, and M is at least one selected from Co, Ni, and Fe. The compound represented by this can be mentioned.

  In addition, a positive electrode active material that operates at less than 4.5 V with respect to lithium can be used as the positive electrode active material.

Although it does not specifically limit as a positive electrode active material which operate | moves with less than 4.5V with respect to lithium, Lithium containing complex oxide can be used. As the lithium-containing composite oxide, LiM1O ₂ (M1 is at least one element selected from the group consisting of Mn, Fe, Co, and Ni, and a part of M1 is substituted with Mg, Al, or Ti. LiMn _2−x M2 _x O ₄ (M2 is at least one element selected from the group consisting of Mg, Al, Co, Ni, Fe, and B, and 0 ≦ x <0.4. ) Etc. can be used. An olivine type material represented by LiFePO ₄ can also be used. These may be non-stoichiometric compositions such as Li-rich compositions. Moreover, these may use only 1 type and can also use 2 or more types together.

Examples of positive electrode active materials that operate at less than 4.5 V with respect to lithium include LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , and LiNi _{0. .6} Mn _0.2 Co _0.2 O ₂ , LiNi _0.8 Mn _0.1 Co _0.1 O ₂ , LiNiO ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiCoO _2, etc. It is preferable to use a lamellar compound, a spinel compound such as LiMn ₂ O ₄ , and an olivine compound such as LiFeO ₄ .

  A positive electrode active material can be used individually by 1 type or in combination of 2 or more types.

Specific surface areas of these positive electrode active materials are, for example, 0.01 to ⁵ m ² / g, preferably 0.05 to ⁴ m ² / g, more preferably 0.1 to ³ m ² / g, and 0.2 to ² m. ² / g is more preferable. By setting the specific surface area in such a range, the contact area with the electrolytic solution can be adjusted to an appropriate range. That is, by setting the specific surface area to 0.01 m ² / g or more, lithium ions can be inserted and desorbed smoothly, and the resistance can be further reduced. Moreover, by making a specific surface area 5 m < ² > / g or less, decomposition | disassembly of electrolyte solution can be accelerated | stimulated and it can suppress more that the constituent element of an active material elutes. The specific surface area can be measured by a usual BET specific surface area measurement method.

The center particle diameter of the positive electrode active material is preferably 0.01 to 50 μm, and more preferably 0.02 to 40 μm. By setting the particle size to 0.01 μm or more, elution of constituent elements of the positive electrode active material can be further suppressed, and deterioration due to contact with the electrolytic solution can be further suppressed. In addition, when the particle size is 50 μm or less, lithium ions can be easily inserted and desorbed smoothly, and the resistance can be further reduced. The central particle diameter is 50% cumulative diameter D ₅₀ (median diameter), and can be measured by a laser diffraction / scattering particle size distribution analyzer.

  Examples of the binder for the positive electrode include polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer rubber, and polytetrafluoroethylene. , Polypropylene, polyethylene, polyimide, and polyamideimide. Among these, polyvinylidene fluoride is preferable from the viewpoint of versatility and low cost. The amount of the binder for positive electrode to be used is preferably 2 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoints of binding force and energy density in a trade-off relationship.

  As the positive electrode current collector, for example, aluminum, nickel, silver, stainless steel (SUS), valve metal, or an alloy thereof can be used from the viewpoint of electrochemical stability. Examples of the shape include foil, flat plate, and mesh. In particular, an aluminum foil can be suitably used.

  A conductive auxiliary material may be added to the positive electrode material containing the positive electrode active material for the purpose of reducing impedance. Examples of the conductive auxiliary material include carbonaceous fine particles such as graphite, carbon black, and acetylene black.

  In addition, a material that releases alkali metal ions during operation of the lithium ion secondary battery may be added to the positive electrode material including the positive electrode active material for the purpose of supplementing the irreversible capacity of the negative electrode. Examples of materials that release alkali metal ions include known active materials, lithium copper oxide, and lithium hydroxide.

  The positive electrode is prepared by, for example, preparing a slurry containing a positive electrode active material, a binder, and a solvent (and optionally a conductive auxiliary material), applying the slurry onto the positive electrode current collector, and drying the slurry. Can be produced by forming a positive electrode active material layer.

(Negative electrode)
Although the negative electrode according to the present embodiment is not particularly limited, for example, a negative electrode current collector, a negative electrode active material layer that is supported on one or both surfaces of the negative electrode current collector, and includes a negative electrode active material and a binder, Have

  The negative electrode active material is not particularly limited as long as it can occlude and release lithium ions. For example, a known material can be used. Examples of the negative electrode active material include carbon materials that can occlude and release lithium ions, metals that can be alloyed with lithium, metal oxides that can occlude and release lithium ions, and mixtures thereof.

  Examples of the carbon material include graphite, coke, and hard carbon. Here, graphite with high crystallinity has high electrical conductivity, and is excellent in adhesiveness and voltage flatness with a negative electrode current collector made of a metal such as copper.

  Examples of metals that can be alloyed with lithium include Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, and alloys of two or more thereof. Examples thereof include lithium alloys such as lithium-aluminum alloy, lithium-lead alloy, and lithium-tin alloy, lithium metal, and Si. Among these, it is preferable to contain Sn or Si.

Examples of the metal oxide include metal oxides such as SnO ₂ , SnO, TiO ₂ , Nb ₂ O ₃ , and SiO whose base potential is lower than that of the positive electrode active material. Among these, tin oxide or silicon oxide is preferably contained, and silicon oxide is more preferably contained.

  As a metal oxide, it is preferable that the metal oxide by which the surface is carbon-coated is included from a viewpoint of an electroconductive improvement, and it is more preferable that it is a silicon oxide by which carbon coating was carried out. The carbon coating method is a method in which a metal oxide and a carbon compound are mixed by applying a shearing force with a ball mill or the like, a method in which a metal oxide and a carbon precursor are carbonized after being mixed, and a chemical vapor deposition method. And the like, and a method of decomposing a carbon compound with a metal oxide and coating the metal oxide.

  The negative electrode can be formed, for example, by placing a negative electrode slurry prepared by mixing a negative electrode active material, a conductivity-imparting agent, and a negative electrode binder on a negative electrode current collector.

  Examples of the conductivity-imparting agent include carbon materials and conductive oxide powders.

  The binder for the negative electrode is not particularly limited. For example, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer. Rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide, polyacrylic acid, or the like can be used. Among them, when a metal that can be alloyed with lithium or a metal oxide that can occlude and release lithium ions is used in an active material ratio of 10% or more, polyimide or polyamideimide is preferable because of its high binding property. The amount of the binder for the negative electrode to be used is preferably 5 to 25 parts by mass with respect to 100 parts by mass of the negative electrode active material from the viewpoints of “sufficient binding force” and “high energy” which are in a trade-off relationship. .

  As the negative electrode current collector, aluminum, nickel, stainless steel, chromium, copper, silver, and alloys thereof are preferable from the viewpoint of electrochemical stability. Examples of the shape include foil, flat plate, and mesh.

  Examples of the method for forming the negative electrode active material layer include a doctor blade method, a die coater method, a CVD method, and a sputtering method. After forming a negative electrode active material layer in advance, a thin film of aluminum, nickel, or an alloy thereof may be formed by a method such as vapor deposition or sputtering to form a negative electrode.

(Separator)
Examples of the separator provided between the positive electrode and the negative electrode include a porous polymer film, a woven fabric, a non-woven fabric, or an ionic conductivity made of a polyolefin such as polyethylene or polypropylene, a fluororesin such as polyimide or polyvinylidene fluoride, and cellulose. Examples include polymer electrolyte membranes. These can be used alone or in combination. In addition, a ceramic material may adhere to or adhere to the separator surface as necessary, for example, to improve safety.

(Battery shape and exterior)
Examples of the shape of the battery include a cylindrical shape, a square shape, a coin shape, a button shape, and a laminate shape.

  In the case of the laminate type, the electrodes and the separator are laminated in a planar shape, and there is no portion with a small R (a region close to the winding core of the wound structure or a region corresponding to a folded portion of the flat wound structure). Therefore, when an active material having a large volume change associated with charging / discharging is used, it is less likely to be adversely affected by the volume change of the electrode associated with charging / discharging than a battery having a wound structure.

  Examples of the battery outer package include stainless steel, iron, aluminum, titanium, alloys thereof, and plated products thereof. As the plating, for example, nickel plating can be used. When the shape of the battery is a laminate type, a laminate film is preferable as the outer package.

  As the laminate film, for example, a film in which a heat welding layer and a metal foil layer are laminated can be used. Examples of the metal foil layer on the resin base layer of the laminate film include aluminum, an aluminum alloy, and a titanium foil. Examples of the material of the heat-welded layer (resin base material layer) of the laminate film include thermoplastic polymer materials such as polyethylene, polypropylene, and polyethylene terephthalate. Moreover, the resin base material layer and the metal foil layer of the laminate film are not limited to one layer, but may be two or more layers. From the viewpoint of versatility and cost, an aluminum laminate film is preferable.

  When a laminate film is used as the exterior body, battery volume changes and electrode distortions are more likely to occur due to gas generation than when a metal can is used as the exterior body. This is because the laminate film is more easily deformed by the internal pressure of the battery than the metal can. In addition, when sealing a secondary battery using a laminate film as an exterior body, the internal pressure of the battery is usually lower than atmospheric pressure, and there is no extra space inside, so when gas is generated in the battery Immediately leads to battery volume change and electrode deformation. In addition, in the case of a laminate type battery, compared to a battery having a wound structure, when gas is generated between the electrodes, the gap between the electrodes tends to be widened because the gas tends to stay between the electrodes. When used, this tendency becomes more prominent. However, according to the present embodiment, the occurrence of such a problem can be suppressed, and a secondary battery excellent in long-term reliability can be provided even for a laminated battery using a laminate film outer package. it can.

  In one embodiment, the above-mentioned secondary battery may be a combined battery by combining a plurality of batteries. Further, the secondary battery described in the present specification can be suitably used for a motor driving power source, a vehicle application, a power storage facility, and the like.

  In one embodiment of the present invention, a coating is formed on the positive electrode surface (or the positive electrode active material surface) by using an electrolytic solution containing a sulfone compound and a compound selected from a pyrrole compound, an aniline compound, and a furan compound. Is done.

  Although the detailed mechanism is not known, the film formed is presumed to be a film containing a composite (reaction) product of a sulfone compound and a compound selected from a pyrrole compound, an aniline compound, and a furan compound.

  The thickness of the coating film to be formed is preferably 1 nm to 1 μm or less, for example, 5 nm to 200 nm or less because charge / discharge cycle characteristics can be improved even under high temperature conditions. Moreover, if the coating film is insoluble in a nonaqueous electrolytic solvent such as diethyl carbonate even after repeated charge / discharge cycles under a high temperature condition such as 45 ° C. or higher, the electrolyte solution in the charge / discharge cycle of the secondary battery It is more preferable because decomposition and elution of positive electrode active material components such as transition metals and oxygen atoms can be suppressed. The film to be formed is preferably stable even when the charge / discharge cycle of the secondary battery is repeated 5 times or more, preferably 50 times or more, more preferably 100 times or more.

  The voltage range of the charge / discharge cycle is not particularly limited as long as the positive electrode active material can be charged / discharged. As the positive electrode active material, any of the aforementioned 4V class active material and 5V class active material is used, the effect of improving the charge / discharge cycle characteristics by the electrolytic solution according to the present invention can be obtained. Although it is inferred, it is considered that the presence of a pyrrole compound, aniline compound or furan compound in the electrolytic solution induces the decomposition of the sulfone compound, and a composite film derived from these compounds and the sulfone compound is formed. . Furthermore, in a charge / discharge cycle in which a high voltage of 4.5 V or higher is applied, a more stable film can be formed, and therefore a higher effect can be obtained when a 5 V class active material is used. It is estimated to be.

  The charging / discharging conditions for forming the coating are not particularly limited, and a normal charging / discharging cycle of the secondary battery may be performed, or the initial charging / discharging cycle is performed at a relatively low current value of about 0.1 C, for example. It is also preferable. Here, 0.1 C represents a current value (that is, 0.1 ItA) that becomes a set capacity in 10 hours. Although the temperature which performs charging / discharging is not specifically limited, The range of room temperature (for example, 5 degreeC or more)-50 degreeC is preferable, and 10 degrees C or less is more preferable than the boiling point of an additive. The charge / discharge cycle performed at a low current value may be performed, for example, 10 cycles or less, usually 1 to 3 cycles, but the number of cycles may be increased as necessary.

  Examples will be described below, but the present invention is not limited to the examples described below unless the gist of the present invention is exceeded.

  The abbreviations of the compounds used in the following examples are described.

SL: sulfolane EC: ethylene carbonate DMC: dimethyl carbonate FE1: H (CF ₂ ) ₂ CH ₂ O (CF ₂ ) ₂ H

(Example 1)
(Preparation of positive electrode)
First, powders of MnO ₂ , NiO, Li ₂ CO ₃ , and Ti ₃ O ₃ were weighed so as to achieve the target composition ratio, and pulverized and mixed. Thereafter, the mixed powder was fired at 750 ° C. for 8 hours to produce LiNi _0.5 Mn _1.37 Ti _0.13 O ₄ . This positive electrode active material was confirmed to have a substantially single-phase spinel structure. The produced positive electrode active material and carbon black as a conductivity-imparting agent were mixed, and this mixture was dispersed in a solution in which polyvinylidene fluoride (PVDF) as a binder was dissolved in N-methylpyrrolidone to prepare a positive electrode slurry. The mass ratio of the positive electrode active material, the conductivity-imparting agent, and the positive electrode binder was 91/5/4. The positive electrode slurry was uniformly applied on both surfaces of the current collector made of Al. Then, it was made to dry in vacuum for 12 hours, and the positive electrode was produced by compression molding with a roll press.

(Preparation of negative electrode)
Graphite as the negative electrode active material was dispersed in N-methylpyrrolidone dissolved in polyvinylidene fluoride (PVDF) as the negative electrode binder to prepare a negative electrode slurry. The mass ratio of the negative electrode active material and the negative electrode binder was 90/10. The slurry was uniformly applied on both sides of the Cu current collector. Then, it was made to dry in vacuum for 12 hours, and the negative electrode was produced by compression molding with a roll press.

(Electrolyte)
Sulfolane (SL) as the sulfone compound, pyrrole as the pyrrole compound, aniline as the aniline compound, furan as the furan compound, fluorinated ether (FE1) represented by H (CF ₂ ) ₂ CH ₂ O (CF ₂ ) ₂ H, ethylene A solvent was prepared by mixing carbonate (EC) and dimethyl carbonate (DMC) so as to have the composition shown in Table 1. An electrolyte solution was prepared by adding LiPF ₆ to this solvent so that the concentration of LiPF ₆ was 1M.

(Production of laminated battery)
The positive electrode and the negative electrode were cut into 1.5 cm × 3 cm. Five layers of the obtained positive electrode and six layers of the negative electrode were alternately stacked while sandwiching a polypropylene porous film as a separator. The ends of the positive electrode current collector not covered with the positive electrode active material and the negative electrode current collector not covered with the negative electrode active material are welded respectively, and further, the positive electrode terminal made of aluminum and the negative electrode terminal made of nickel are connected to the welded portion. Each was welded to obtain an electrode element having a planar laminated structure. The electrode element was wrapped with an aluminum laminate film as an outer package, and an electrolyte solution was injected therein, and then sealed while reducing the pressure to produce a secondary battery.

(Formation of film)
Using the above laminate type, a cycle of constant current charging at 0.1 C to 4.8 V and then constant current discharging at 0.1 C to 3.6 V was repeated twice at 20 ° C.

(Examples 2-6 and Comparative Examples 1-6)
A battery was fabricated in the same manner as in Example 1 except that the composition of the solvent and additive was as shown in Table 1.

  The batteries obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were evaluated for charge / discharge characteristics.

(High temperature cycle test)
The battery produced as described above was evaluated for charge / discharge cycle characteristics at a high temperature. The cycle of constant current and constant voltage charge at 1C to 4.8V (2.5 hours in total) and constant current discharge to 3.0V at 1C was repeated 300 times at 45 ° C. As a capacity retention rate, the ratio of the discharge capacity after 300 cycles to the initial discharge capacity was determined.

(Sulfur content analysis on the positive electrode)
For Examples 1 to 4 and Comparative Examples 1 to 6, the positive electrode after 300 cycles was taken out, washed with diethyl carbonate in an argon atmosphere, and then subjected to a fluorescent X-ray analyzer (trade name: ZSX Prims II, manufactured by Rigaku Corporation). The sulfur contained in the positive electrode was analyzed by fluorescent X-ray analysis. As a result, the presence of sulfur was confirmed in Examples 1 to 4 using an electrolyte containing both a sulfone compound and a compound selected from a pyrrole compound, an aniline compound, and a furan compound, and Comparative Examples 1 to 6 not including both. No sulfur was detected. From this result, when only one compound selected from the sulfone compound and the pyrrole compound, the aniline compound and the furan compound was included, a stable film could not be formed on the positive electrode surface, whereas the sulfone compound and the pyrrole By including both the compound, the compound selected from the aniline compound, and the furan compound, it is guessed that the firm film is formed on the positive electrode surface which operate | moves at 4.5V or more.

(Example 7)
The capacity retention rate was measured in the same manner as in Example 6 except that the same amount of 3-acetylthiophene was used instead of aniline in Example 6. As a result, it was 54% at 45 ° C. and 300 cycles.

  As shown in Table 1, even when a positive electrode of 4.5 V or more is used, the lithium secondary battery includes both a sulfone compound and a compound selected from a pyrrole compound, an aniline compound, and a furan compound. It can be seen that the charge / discharge cycle characteristics under high temperature conditions can be improved.

  In addition, as shown in Example 6 and Example 7, the electrolyte solution contains a plurality of types of compounds selected from pyrrole compounds, aniline compounds, and furan compounds and sulfone compounds, and sulfone compounds, pyrrole compounds, and aniline compounds. In addition to the compound selected from the furan compound, even if a thiophene compound is further included in the electrolyte, the charge / discharge cycle characteristics under a high temperature condition of a lithium secondary battery using a positive electrode of 4.5 V or more are improved. You can see that

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to these, In the category of the summary of the invention as described in a claim, it can change variously. In addition, the present invention can be variously modified without departing from the scope of the invention in the implementation stage. Furthermore, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

DESCRIPTION OF SYMBOLS 1 Positive electrode active material layer 2 Negative electrode active material layer 3 Positive electrode collector 4 Negative electrode collector 5 Separator 6 Laminate exterior 7 Laminate exterior 8 Negative electrode tab 9 Positive electrode tab

Claims (17)

An electrolyte solution comprising a sulfone compound represented by the following formula (1) and one or more compounds selected from the group consisting of a pyrrole compound, an aniline compound, and a furan compound.

[In Formula (1), R < ₁ > and R < ₂ > shows a substituted or unsubstituted alkyl group each independently. The carbon atom of R _{1 and} the carbon atom of R ₂ may be bonded via a single bond or a double bond to form a cyclic structure. ] 2. The electrolytic solution according to claim 1, wherein the pyrrole compound is a compound represented by the following formula (2), the aniline compound is a compound represented by the following formula (3), and the furan compound is represented by the following formula (4).

(Wherein R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently a hydrogen atom, —R ^x or —A;
-R ^x is a straight-chain or branched-chain alkyl group having 1 to 18 carbon atoms, straight-chain or branched-chain alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, arylalkyl of 7 to 20 carbon atoms Group, an alkylaryl group having 7 to 20 carbon atoms, an acyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, and an alkoxycarbonylalkyl group having 3 to 10 carbon atoms is selected from the group consisting more, provided that at least one of the hydrogen atoms of the -R ^x may be substituted by -A,
-A is hydroxyl group, carboxyl group, halogen, amino group, nitro group, cyano group, aldehyde group, isocyanato group, arylsulfonyl group having 6 to 18 carbon atoms, tosyl group, silyl group, furyl group, pyrrolyl group, thiol Selected from the group consisting of a group, a sulfonic acid group, a hydrazide group, an acid halogen group, an amide group and a sulfonamide group,
Here, _two adjacent groups selected from the group consisting of R ₁ , R ₂ , R ₃ and R ₄ may be bonded to form a ring. )

(Where
R ₁ and R ₂ are each independently a hydrogen atom or —R ^x ;
R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently a hydrogen atom, —R ^x , —A or —ZB;
-R ^x is a straight-chain or branched-chain alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, straight-chain or branched-chain alkenyl group having 2 to 18 carbon atoms, aryl having 6 to 18 carbon atoms A group having 7 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, an acyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, and is selected from the group consisting of alkoxycarbonylalkyl group having 3 to 10 carbon atoms, provided that at least one of the hydrogen atoms of the -R ^x may be substituted by -A,
-A is a group consisting of hydroxyl group, carboxyl group, halogen, amino group, cyano group, nitroso group, nitro group, aldehyde group, sulfonic acid group, hydrazide group, acid halogen group, amide group, sulfonamide group and thiol group More selected,
-Z- is a direct bond or a divalent group selected from the group consisting of an alkylene group having 1 to 5 carbon atoms, an alkenylene group having 2 to 5 carbon atoms, a sulfonyl group, an azo group and an ether group,
-B is an aryl group having 6 to 12 carbon atoms, an aminophenyl group, or a heterocyclic group having one or more selected from oxygen, nitrogen, sulfur and boron as a hetero atom;
Here, two adjacent groups selected from the group consisting of R ₃ , R ₄ , R ₅ , R ₆ and R ₇ may be bonded to form a ring. )

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, —R ^x or —A;
-R ^x is a straight-chain or branched-chain alkyl group having 1 to 18 carbon atoms, straight-chain or branched-chain alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, arylalkyl of 7 to 20 carbon atoms Group, alkyl aryl group having 7 to 20 carbon atoms, styryl group, alkyl styryl group having 9 to 11 carbon atoms, acyl group having 2 to 10 carbon atoms, alkoxy group having 1 to 6 carbon atoms, alkoxy having 2 to 10 carbon atoms is selected from the group consisting of alkoxycarbonylalkyl group of the carbonyl group and having 3 to 10 carbon atoms, provided that at least one of the hydrogen atoms of the -R ^x may be substituted by -A,
-A is hydroxyl group, carboxyl group, halogen, amino group, nitro group, aldehyde group, boronic acid group, thiol group, halogenated sulfonyl group, furyl group, halocarbonyl group, sulfonic acid group, hydrazide group, acid halogen group , Selected from the group consisting of amide groups and sulfonamido groups,
Here, _two adjacent groups selected from the group consisting of R ₁ , R ₂ , R ₃ and R ₄ may be bonded to form a ring. ) The electrolyte solution according to claim 1 or 2, wherein the sulfone compound is a cyclic sulfone compound represented by the following formula (1-1).

[In Formula (1-1), R ₃ represents a substituted or unsubstituted alkylene group. ]   The content of the sulfone compound represented by the formula (1) is 5% by volume or more and 50% by volume or less in the nonaqueous electrolytic solvent, according to any one of claims 1 to 3. Electrolytic solution.   The total content of the compound selected from the pyrrole compound, the aniline compound, and the furan compound is 0.5 g / L or more and 100 g / L or less with respect to the nonaqueous electrolytic solvent. 5. The electrolytic solution according to any one of 4 above.   The compound selected from the pyrrole compound, the aniline compound, and the furan compound is contained at a ratio of 0.04 g / ml to 0.12 g / ml with respect to the sulfone compound. Electrolyte as described in any one of these.   7. A secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium, and an electrolytic solution containing a non-aqueous electrolytic solvent, wherein the electrolytic solution is according to claim 1. A secondary battery characterized by being an electrolyte solution.   The secondary battery according to claim 7, wherein the positive electrode includes a positive electrode active material that operates at 4.5 V or more with respect to lithium. The secondary battery according to claim 8, wherein the positive electrode active material is one or more lithium composite oxides represented by any one of the following formulas (5), (6), and (7).
Li _a (M _x Mn _2−xy Y _y ) (O _4−w Z _w ) (5)
[In formula (5), 0.4 ≦ x ≦ 1.2, 0 ≦ y, x + y <2, 0 ≦ a ≦ 1.2, and 0 ≦ w ≦ 1. M includes at least one selected from the group consisting of Co, Ni, Fe, Cr, and Cu. Y is at least one selected from the group consisting of Li, B, Na, Mg, Al, Ti, Si, K, and Ca. Z is at least one of F or Cl. ]
LiMPO ₄ (6)
[In Formula (6), M is at least one of Co and Ni. ]
_{Li (Li x M 1-x} -z Mn z) O 2 (7)
[In formula (7), 0 ≦ x <0.3, 0.3 ≦ z ≦ 0.7, and M is at least one selected from Co, Ni, and Fe. ] The secondary battery according to claim 9, wherein the positive electrode active material is a lithium manganese composite oxide represented by the following formula (5-1).
LiNi _x Mn _2-xy A _y O ₄ (5-1)
[In Formula (5-1), 0.4 <x <0.6, 0 ≦ y <0.3, A is at least one selected from Li, B, Na, Mg, Al, Ti, and Si. is there. ]   A secondary battery having a positive electrode and a negative electrode capable of inserting and extracting lithium, and an electrolytic solution containing a nonaqueous electrolytic solvent, and cannot be removed with diethyl carbonate on the surface of the positive electrode after a charge / discharge cycle. A secondary battery comprising a film containing sulfur.   The secondary battery according to claim 11, wherein the charge / discharge cycle is performed at 45 ° C. or higher.   The secondary battery according to claim 11, wherein the positive electrode includes a positive electrode active material that operates at 4.5 V or more with respect to lithium.   A positive electrode for a secondary battery, comprising a sulfur-containing film obtained by performing a charge / discharge cycle using the electrolytic solution according to claim 1. An electrolyte solution characterized by dissolving a sulfone compound represented by the following formula (8) and one or more compounds selected from the group consisting of a pyrrole compound, an aniline compound, and a furan compound in a nonaqueous electrolytic solvent. Manufacturing method.

[In Formula (8), R ₁ and R ₂ each independently represent a substituted or unsubstituted alkyl group. The carbon atom of R _{1 and} the carbon atom of R ₂ may be bonded via a single bond or a double bond to form a cyclic structure. ] A method for producing a secondary battery having a positive electrode and a negative electrode capable of inserting and extracting lithium, an electrolyte, and an outer package,
A step of arranging the positive electrode and the negative electrode facing each other to produce an electrode element;
Encapsulating the electrode element and the electrolytic solution produced by the production method according to claim 15 in an exterior body;
The manufacturing method of a secondary battery characterized by including.   The method for manufacturing a secondary battery according to claim 16, wherein the positive electrode includes a positive electrode active material that operates at 4.5 V or more with respect to lithium.

Images