JP6766818B2 - Non-aqueous electrolyte for lithium secondary batteries or lithium ion capacitors and lithium secondary batteries or lithium ion capacitors using it - Google Patents

Description

According to the present invention, the non-aqueous electrolyte solution does not solidify even at an extremely low temperature of −40 ° C., and the non-aqueous electrolyte solution or lithium ion capacitor for a lithium secondary battery is excellent in battery performance such as withstand voltage. The present invention relates to a non-aqueous electrolyte solution for use, and a lithium secondary battery or a lithium ion capacitor using the same.

In recent years, lithium secondary batteries or lithium ion capacitors have come to be widely used not only as small electronic devices such as mobile phones and notebook computers, but also as in-vehicle power supplies for electric vehicles and idling stops, and power supplies for power storage. I came. In order to extend the cruising range of these electric vehicles, further high voltage and high energy density power storage devices are being developed. As a result, electric vehicles have a long travel distance and have the potential to be used in a wide range of temperatures, from extremely hot areas such as the tropics to extremely cold areas. Therefore, these lithium secondary batteries and lithium ion capacitors may reach 60 ° C. or higher in a car under the scorching sun. In addition, the non-aqueous electrolyte solution may solidify at a cryogenic temperature of −40 ° C. or lower. Therefore, even when used in a "wide temperature range with a temperature range of 100 ° C", which is a high temperature of 60 ° C to an extremely low temperature of -40 ° C or less, it can be used while maintaining the liquid state, and has excellent battery performance. Is required to show.

The lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of occluding and releasing lithium, a non-aqueous electrolytic solution composed of a lithium salt and a non-aqueous solvent, and examples of the non-aqueous solvent include ethylene carbonate (EC). A carbonate such as dimethyl carbonate (DMC) is used.
When a non-aqueous electrolytic solution containing such a non-aqueous solvent is used at a high voltage of 4.2 V or higher, a part of the solvent may be decomposed. When used in a "wide temperature range with a temperature range of 100 ° C" from a high temperature of 60 ° C or higher to an extremely low temperature of -40 ° C or lower, physical properties such as flash point, freezing point, electrical conductivity, or viscosity become battery characteristics. It was found that it would have a great impact, and improvement of the above problems was required.

In Patent Document 1, the non-aqueous solvent is composed of a mixed solvent containing one or more cyclic esters and one or more chain esters, the mixed solvents are compatible with each other, and at least one chain ester is used. A non-aqueous electrolyte secondary battery, which is a halogenated chain carbonate, has been disclosed and has been shown to improve safety.
Patent Document 2 describes a film-forming compound in which a non-aqueous solvent is decomposed in the range of +1.0 to 3.0 V based on the equilibrium potential of fluorinated chain carboxylic acid ester and metallic lithium and lithium ion. A non-aqueous electrolyte solution for a secondary battery containing the present invention is disclosed, and it has been shown that a decrease in battery capacity is suppressed under high temperature conditions.
Further, Patent Document 3 discloses an electrolytic solution for a lithium ion battery containing 2,2-difluoroethyl acetate having a non-aqueous solvent of 50 to 90%, and the cycle characteristics are improved at a high voltage under high temperature conditions. It is shown.

Further, Patent Document 4 describes a mixture containing 20 to 35% by volume of ethylene carbonate, 35 to 45% by volume of ethylmethyl carbonate, 15 to 35% by volume of dimethyl carbonate, and 3 to 15% by volume of diethyl carbonate or propylene carbonate. It is disclosed that in a lithium secondary battery using a non-aqueous electrolytic solution composed of a solvent, the cycle characteristics at room temperature and −30 ° C. are improved.
Further, Patent Document 5 describes LiPF in a solvent obtained by mixing ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and methyl propionate in a volume ratio of 3: 3: 3: 1. ₆It is disclosed that the output characteristics at −30 ° C. are improved in a lithium secondary battery using a non-aqueous electrolytic solution in which 2M is dissolved and 2% by mass of vinylene carbonate is added.

JP-A-11-40195 International Publication No. 2008/102493 Pamphlet International Publication No. 2013/033579 Pamphlet Japanese Unexamined Patent Publication No. 2005-353579 Japanese Unexamined Patent Publication No. 2006-172775

The present invention is a lithium secondary that can be used while maintaining a liquid state in a "wide temperature range of up to 100 ° C" without solidifying even at -40 ° C or lower, and can exhibit excellent battery performance. It is an object of the present invention to provide a non-aqueous electrolyte solution for a battery or a lithium ion capacitor, a lithium secondary battery using the same, and a lithium ion capacitor.

As a result of detailed examination of the performance of the non-aqueous electrolyte solution of the prior art, the present inventors have improved the safety and the high temperature of the lithium secondary battery using the non-aqueous electrolyte solution of Patent Documents 1 to 5. Although it is possible to improve the cycle characteristics under conditions of -30 ° C or high-voltage batteries, it can be used while maintaining the liquid state without solidification even at -40 ° C or lower, and has excellent battery performance. Not only has it not been sufficiently effective for the problem of showing the above, but the fact is that it does not disclose the composition of the electrolytic solution that does not solidify even at -40 ° C or lower.
Therefore, as a result of intensive studies to solve the above problems, the present inventors have found that the lithium salt is dissolved in a non-aqueous solvent in an amount of 0.8 to 1.5 M (mol / L). In the aqueous electrolytic solution, the non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 10 to 20% by volume of the total non-aqueous solvent. Fluorinated chain ester and 20 to 40% by volume of methyl ethyl carbonate are contained, and the total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and dimethyl carbonate. The total content of the solvent and the fluorinated chain ester is 30 to 40% by volume, whereby the ignition point of the non-aqueous electrolyte solution is 20 ° C. or higher and the electrical conductivity is 8 mS / cm or higher. I found that. Moreover, by using a mixed solvent containing various carbonates and a fluorinated chain ester in a specific ratio, the temperature range is as wide as 100 ° C. without coagulation even at -40 ° C or lower. The present invention has been completed by finding that it can be used while maintaining the liquid state in the "temperature range" and that the withstand voltage showing excellent battery performance is also improved. It should be noted that such an action and effect cannot be achieved by the techniques of Patent Documents 1 to 5, and are not suggested at all by Patent Documents 1 to 5.

In addition, as a result of further diligent research to solve the above problems, the present inventors have dissolved a lithium salt in a non-aqueous solvent in an amount of 0.9 to 1.5 M (mol / L). In the non-aqueous electrolyte solution, the non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 20 to 40% of the total amount of the non-aqueous solvent. It contains 10 to 20% by volume of methyl ethyl carbonate and 10 to 20% by volume of ethyl propionate, and the total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and dimethyl carbonate. The total content of the solvent and ethyl propionate is 30 to 40% by volume, so that the ignition point of the non-aqueous electrolyte solution is 20 ° C. or higher and the electrical conductivity is 8 mS / cm or higher. I found. Moreover, by using a mixed solvent containing various carbonates and ethyl propionate having two ethyl groups at both ends of the ester (-COO-) in a specific ratio, it coagulates even at -40 ° C or lower. The present invention has been completed by finding that it can be used while maintaining a liquid state in a "wide temperature range with a temperature range of up to 100 ° C." and that the withstand voltage showing excellent battery performance is also improved. It should be noted that such an action and effect cannot be achieved by the techniques of Patent Documents 1 to 5, and are not suggested at all by Patent Documents 1 to 5.

That is, the present invention provides the following (1) to (4).
(1) In a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.8 to 1.5 M (mol / L).
The non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 10 to 20% by volume of fluorinated chains with respect to the whole non-aqueous solvent. Containing ester and 20-40% by volume methyl ethyl carbonate,
The total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and the total content of dimethyl carbonate and fluorinated chain ester is 30 to 40% by volume.
A non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor, characterized in that the flash point of the non-aqueous electrolyte solution is 20 ° C. or higher.

(2) In a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.9 to 1.5 M (mol / L).
The non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 20 to 40% by volume of methyl ethyl carbonate with respect to the whole non-aqueous solvent. , And containing 10 to 20% by volume of ethyl propionate,
The total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and the total content of dimethyl carbonate and ethyl propionate is 30 to 40% by volume.
A non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor, characterized in that the flash point of the non-aqueous electrolyte solution is 20 ° C. or higher.

(3) In a lithium secondary battery provided with a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent, the non-aqueous electrolyte solution is the non-aqueous solution according to (1) or (2) above. A lithium secondary battery characterized by being an electrolytic solution.

(4) In a lithium ion capacitor provided with a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a non-aqueous solvent, the non-aqueous electrolyte solution is the non-aqueous electrolytic solution according to (1) or (2) above. A lithium ion capacitor characterized by being a liquid.

The non-aqueous electrolytic solution of the present invention has an excellent withstand voltage and a high ignition point (20 ° C. or higher) by setting the lithium salt concentration in a specific range and mixing a specific solvent at a specific ratio. In addition, it has a low freezing point and exhibits high electrical conductivity without solidifying at -40 ° C. Therefore, according to the non-aqueous electrolytic solution of the present invention, excellent characteristics are exhibited in a wide temperature range from high temperature to extremely low temperature. The lithium secondary battery or lithium ion capacitor shown can be provided.

The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor and a lithium secondary battery or a lithium ion capacitor using the same.

[Non-aqueous electrolyte]
The non-aqueous electrolytic solution according to the first aspect of the present invention is a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.8 to 1.5 M (mol / L).
The non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 10 to 20% by volume of fluorinated chains with respect to the whole non-aqueous solvent. Containing ester and 20-40% by volume methyl ethyl carbonate,
The total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and the total content of dimethyl carbonate and fluorinated chain ester is 30 to 40% by volume.
A non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor, characterized in that the flash point of the non-aqueous electrolyte solution is 20 ° C. or higher.

Alternatively, the non-aqueous electrolytic solution according to the second aspect of the present invention is a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.9 to 1.5 M (mol / L).
The non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 20 to 40% by volume of methyl ethyl carbonate with respect to the whole non-aqueous solvent. , And containing 10 to 20% by volume of ethyl propionate,
The total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and the total content of dimethyl carbonate and ethyl propionate is 30 to 40% by volume.
A non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor, characterized in that the flash point of the non-aqueous electrolyte solution is 20 ° C. or higher.

[Lithium salt]
Preferred examples of the lithium salt used in the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect are as follows.
Lithium salts include inorganic lithium salts such as LiPF ₆ , LiPO ₂ F ₂ , and LiBF ₄ , LiN (SO ₂ F) ₂ [LiFSI], LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ). Lithium salt containing a chain alkyl fluoride group of _2nd grade, lithium methyl sulfate [LMS], lithium ethyl sulfate [LES], or lithium salt having an S = O group such as FSO ₃ Li, and lithium bis (oxalato). ) Lithium salts having a oxalate skeleton such as bolate [LiBOB], lithium difluoro (oxalat) borate [LiDFOB], lithium tetrafluoro (oxalat) phosphate [LiTFOP], or lithium difluorobis (oxalat) phosphate [LiDFOP] are preferred. At least one or a mixture of two or more selected from these can be used.
Among these, LiPF ₆ , LiPO ₂ F ₂ , LiN (SO ₂ F) ₂ , lithium methyl sulfate, lithium ethyl sulfate, or lithium difluorobis (oxalat) phosphate is more preferably used, and most preferably LiPF ₆ , LiPF ₆ . LiPO ₂ F ₂ , LiN (SO ₂ F) ₂ , lithium methyl sulfate, or lithium ethyl sulfate. In the non-aqueous electrolyte solution according to the first aspect, the concentration of the lithium salt is 0.8 M (mol / L) or more, preferably 1.0 M or more, preferably 1.1 M, with respect to the above-mentioned non-aqueous solvent. The above is more preferable. The upper limit thereof is 1.5 M or less, preferably 1.45 M or less, and more preferably 1.4 M or less. Further, the concentration of the lithium salt in the non-aqueous electrolytic solution according to the second aspect is 0.9 M (mol / L) or more, preferably 1.0 M or more, with respect to the above-mentioned non-aqueous solvent. 1M or more is more preferable, 1.15M or more is further preferable, and 1.2M or more is particularly preferable. The upper limit thereof is 1.5 M or less, preferably 1.45 M or less, and more preferably 1.4 M or less.
Further, as these electrolyte salts, those containing at least LiPF ₆ are preferable, those containing at least LiPF ₆ and LiN (SO ₂ F) ₂ are more preferable, and in addition to LiPF ₆ and LiN (SO ₂ F) _2. Therefore, those containing lithium salts other than these are more preferable. In the "wide temperature range of up to 100 ° C.", the ratio of lithium salts other than LiPF ₆ and / or LiN (SO ₂ F) ₂ , for example, LiPO ₂ F ₂ in the non-aqueous solvent is 0.001 M. The above is preferable because the battery characteristics in a wide temperature range are improved, and when the temperature is 0.3 M or less, there is little concern that the effect of improving the battery characteristics in a wide temperature range is reduced. It is preferably 0.01 M or more, particularly preferably 0.03 M or more, and most preferably 0.04 M or more. The upper limit is preferably 0.3 M or less, more preferably 0.25 M or less, and particularly preferably 0.2 M or less.

The ratio of the lithium salt having an oxalic acid skeleton and the lithium salt having an S = O group in the non-aqueous solvent is preferably 0.001 M or more and 0.5 M or less. Within this range, the effect of improving the electrochemical characteristics in a wide temperature range is further exhibited. It is preferably 0.01 M or more, more preferably 0.03 M or more, and particularly preferably 0.04 M or more. The upper limit is more preferably 0.4 M or less, and particularly preferably 0.2 M or less.

[Non-aqueous solvent]
The non-aqueous solvent used in the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect is from the viewpoint of synergistically improving the electrochemical properties in a wide temperature range. , Cyclic carbonate, chain carbonate, and a mixed solvent containing a chain ester.

As the cyclic carbonate, at least ethylene carbonate and propylene carbonate are used.
The content of ethylene carbonate is 5% by volume or more, preferably 7% by volume or more, more preferably 9% by volume or more, based on the whole non-aqueous solvent, from the viewpoint of improving the electric conductivity. The upper limit of the ethylene carbonate content is 25% by volume or less, preferably 22% by volume or less, more preferably 20% by volume or less, still more preferable, with respect to the entire non-aqueous solvent, from the viewpoint of lowering the freezing point. Is 17% by volume or less, particularly preferably 15% by volume or less.
The content of propylene carbonate is 5% by volume or more, preferably 7% by volume or more, and more preferably 9% by volume or more, based on the total amount of the non-aqueous solvent, from the viewpoint of improving the electrochemical properties in a high temperature environment. The upper limit of the content of propylene carbonate is 25% by volume or less, preferably 20% by volume or less, more preferably 17% by volume or less, more preferably 17% by volume or less, based on the whole non-aqueous solvent, from the viewpoint of improving the electric conductivity. Is 15% by volume or less.
Further, the total content of ethylene carbonate and propylene carbonate is 20% by volume or more, preferably 22% by volume or more, based on the whole non-aqueous solvent, from the viewpoint of improving the electric conductivity. The upper limit of the total content of ethylene carbonate and propylene carbonate is 30% by volume or less, preferably 27% by volume or less, based on the total non-aqueous solvent, from the viewpoint of improving the electrochemical characteristics in a high temperature environment. ..

Further, the non-aqueous solvent used in the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect contains ethylene carbonate and other cyclic carbonates other than propylene carbonate. It may be. Examples of the "other cyclic carbonate" include a cyclic carbonate having an alkyl group such as 1,2-butylene carbonate or 2,3-butylene carbonate and having a total carbon number of 5 or more, 4-fluoro-1,3-dioxolane-2-. Cyclic carbonate, vinylene carbonate (VC) having a fluorine atom such as on (FEC) or trans or cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter, both are collectively referred to as "DFEC"). ) Or cyclic carbonates with carbon-carbon double bonds such as vinylethylene carbonate (VEC), and 2-propynyl 2-oxo-1,3-dioxolan-4-carboxylate (PDC) or 4-ethynyl-1,3. One or more selected from the group consisting of cyclic carbonates having a carbon-carbon triple bond such as −dioxolan-2-one (EEC) is preferably used.
Examples of the "other cyclic carbonates" include 4-fluoro-1,3-dioxolane-2-one, vinylene carbonate, 2-propynyl 2-oxo-1,3-dioxolane-4-carboxylate, and 4-ethynyl. One or more selected from -1,3-dioxolane-2-one is more preferable.

Further, as the "other cyclic carbonate", when at least one of an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond or a cyclic carbonate having a fluorine atom is used, it is possible to use it in a high temperature environment. It is preferable because the electrochemical properties are further improved, and it is more preferable to contain both a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom.

The content of the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is preferably 0.07% by volume or more, more preferably 0.2% by volume, based on the total amount of the non-aqueous solvent. % Or more, more preferably 0.7% by volume or more, and the upper limit thereof is preferably 7% by volume or less, more preferably 4% by volume or less, still more preferably 2.5% by volume or less. It is preferable because the electrochemical properties in a wider temperature range can be increased without impairing the Li ion permeability.

The content of the cyclic carbonate having a fluorine atom is preferably 0.07% by volume or more, more preferably 0.3% by volume or more, still more preferably 0.7% by volume or more, and more preferably 0.7% by volume or more, based on the whole non-aqueous solvent. When the upper limit is preferably 10% by volume or less, more preferably 7% by volume or less, and further 5% by volume or less, the electrochemical characteristics in a wider temperature range are improved without impairing the Li ion permeability. It is preferable because it can be used.

The total content of a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom is 0.3% by volume based on the total non-aqueous solvent. The above is preferable, and 0.7% by volume or more is more preferable. The upper limit thereof is preferably 7% by volume or less, more preferably 5% by volume or less. When the content is within the above range, there is a synergistic effect due to the combined use of the cyclic carbonate having an unsaturated bond and the cyclic carbonate having a fluorine atom, which is more preferable.

When three or more kinds of these cyclic carbonates are used in combination, the effect of improving the electrochemical properties in a high temperature environment is further improved, and it is preferable to use them in combination of four or more kinds. Suitable combinations of these cyclic carbonates include EC and PC and VC, EC and PC and FEC, EC and PC and VEC, EC and PC and EEC, EC and PC and VC and FEC, EC and PC and VC and VEC. , EC and PC and VC and EEC, EC and PC and FEC and VEC, EC and PC and FEC and EEC, or EC and PC and VEC and EEC are preferable. Among the above combinations, a combination of EC and PC and VC, EC and PC and FEC, EC and PC and EEC, EC and PC and VC and FEC, or EC and PC and VC and EEC is more preferable.

In the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect, at least methyl ethyl carbonate and dimethyl carbonate are used as the chain carbonate.
The content of methyl ethyl carbonate is 20% by volume or more, preferably 23% by volume or more, more preferably 30% by volume or more, particularly, with respect to the entire non-aqueous solvent, from the viewpoint of improving the electrochemical properties in a high temperature environment. It is preferably 33% by volume or more. The upper limit of the content of methyl ethyl carbonate is 40% by volume or less, preferably 37% by volume or less, based on the whole non-aqueous solvent, from the viewpoint of improving the electric conductivity.
The content of dimethyl carbonate is 20% by volume or more, preferably 23% by volume or more, based on the whole non-aqueous solvent, from the viewpoint of improving the electric conductivity. The upper limit of the content of dimethyl carbonate is 30% by volume or less, preferably 27% by volume or less, based on the total amount of the non-aqueous solvent, from the viewpoint of improving the electrochemical characteristics in a high temperature environment.

Further, in the non-aqueous solvent used in the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect, methyl ethyl carbonate and other chain carbonates other than dimethyl carbonate are contained. May be included. Other chain carbonates include one or more asymmetric chain carbonates selected from methylpropyl carbonate (MPC), methylisopropyl carbonate (MIPC), methylbutyl carbonate, and ethylpropyl carbonate, diethyl carbonate (DEC). , Dipropyl carbonate, and one or more symmetrical chain carbonates selected from dibutyl carbonate are preferred.

The non-aqueous electrolyte solution according to the first aspect of the present invention contains a fluorinated chain ester as a chain ester. Examples of the fluorinated chain ester used in the present invention include those in which any carbon atom of the chain ester is replaced with a fluorine atom. In particular, a compound in which the carbon atom of the alkyloxy group portion of the chain ester is replaced with a fluorine atom is preferable.

As the fluorinated chain ester, a compound represented by the following general formula (I) is particularly preferable.

（式中、Ｒ^１は、ＣＦ_ｍＨ_３−ｍ、又はＯＣＦ_ｍＨ_３−ｍであり、Ｒ^２は、ＣＨ_３、Ｃ_２Ｈ_5、又はＣＨ₂ＣＦ_nＨ_３−nであり、ｍは、０から３の整数であり、ｎは、２又は３を示す。ただし、Ｒ^１及びＲ^２のいずれかが少なくとも一つのフッ素原子で置換されている。）

(In the formula, R ¹ is CF _m H _3-m or OCF _m H _3-m , and R ² is CH _3, C ₂ H _5, or CH ₂ CF _n H _3-n , m. Is an integer from 0 to 3, where n represents 2 or 3, where either R ¹ or R ² is replaced by at least one fluorine atom.)

Specific examples of the fluorinated chain ester represented by the general formula (I) include 2,2-difluoroethyl acetate (DFEA), 2,2,2-trifluoroethyl acetate (TFEA), and 2 , 2-Difluoroethyl methyl carbonate (DFEMC), 2,2,2-triluoloethyl methyl carbonate (TFEMC), methyltrifluoroacetate, ethyltrifluoroacetate, 2,2-difluoroethyltrifluoroacetate, and 2,2 , 2-Trifluoroethyl Trifluoroacetate is preferably selected from the group consisting of one or more.
Above all, from the viewpoint of improving the electrochemical properties in a high temperature environment, 2,2,2-trifluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, 2,2,2-trifluoroethyl acetate, or 2,2 -Difluoroethyl acetate is more preferred.

In the first aspect of the present invention, the content of the fluorinated chain ester is 10% by volume or more based on the total amount of the non-aqueous solvent from the viewpoint of improving the withstand voltage and improving the electrochemical characteristics in a high temperature environment. It is preferably 12% by volume or more. The upper limit of the content of the fluorinated chain ester is 20% by volume or less, preferably 18% by volume or less from the viewpoint of improving the electric conductivity.

Further, the non-aqueous solvent used in the non-aqueous electrolyte solution according to the first aspect of the present invention may contain other chain esters other than the fluorinated chain ester. Other chain esters include one or more selected from methyl pivalate (MPv), ethyl pivalate, propyl pivalate, methyl propionate (MP), propyl propionate, methyl acetate, and ethyl acetate. A chain carboxylic acid ester is preferably used. Among them, if one or more selected from methyl pivalate (MPv), ethyl pivalate, and propyl pivalate, which are chain esters in which all the hydrogen atoms of the carbon at the α-position of the ester are substituted with methyl groups, are contained, after high temperature storage. The low temperature characteristics are further improved.

Further, in the non-aqueous electrolytic solution according to the first aspect of the present invention, the total content of the dimethyl carbonate and the fluorinated chain ester is 30% by volume with respect to the entire non-aqueous solvent from the viewpoint of improving the electric conductivity. As mentioned above, it is preferably 32% by volume or more. The upper limit of the total content of the dimethyl carbonate and the fluorinated chain ester is 40% by volume or less, preferably 37% by volume, based on the total amount of the non-aqueous solvent from the viewpoint of improving the electrochemical characteristics in a high temperature environment. It is as follows.

The total content of the chain carbonate and the fluorinated chain ester in the non-aqueous electrolyte solution according to the first aspect of the present invention is not particularly limited, but is in the range of 70 to 80% by volume with respect to the entire non-aqueous solvent. It is preferable to use in. If the content is 70% by volume or more, the viscosity of the non-aqueous electrolyte solution does not become too high, and if it is 80% by volume or less, the electrical conductivity of the non-aqueous electrolyte solution decreases and the electrochemical characteristics over a wide temperature range. Is less likely to decrease, so the above range is preferable.

Alternatively, the non-aqueous electrolyte solution according to the second aspect of the present invention contains ethyl propionate as a chain ester.
In the non-aqueous electrolytic solution according to the second aspect of the present invention, the content of ethyl propionate is 10% by volume or more, preferably 12% by volume, based on the whole non-aqueous solvent from the viewpoint of improving the electric conductivity. That is all. The upper limit of the content of ethyl propionate is 20% by volume or less, preferably 18% by volume or less from the viewpoint of improving the electrochemical characteristics in a high temperature environment.

In addition, the non-aqueous solvent used in the non-aqueous electrolyte solution according to the second aspect of the present invention may contain a chain ester other than ethyl propionate. Other chain esters include one or more selected from methyl pivalate (MPv), ethyl pivalate, propyl pivalate, methyl propionate (MP), propyl propionate, methyl acetate, and ethyl acetate. A chain carboxylic acid ester is preferably used. Among them, if one or more selected from methyl pivalate (MPv), ethyl pivalate, and propyl pivalate, which are chain esters in which all the hydrogen atoms of the carbon at the α-position of the ester are substituted with methyl groups, are contained, after high temperature storage. The low temperature characteristics are further improved.

Further, in the non-aqueous electrolytic solution according to the second aspect of the present invention, the total content of dimethyl carbonate and ethyl propionate is 30% by volume or more with respect to the total non-aqueous solvent from the viewpoint of improving the electric conductivity. , Preferably 32% by volume or more. The upper limit of the total content of dimethyl carbonate and ethyl propionate is 40% by volume or less, preferably 37% by volume or less, based on the total non-aqueous solvent, from the viewpoint of improving the electrochemical characteristics in a high temperature environment. Is.

In the non-aqueous electrolyte solution according to the second aspect of the present invention, the total content of the chain carbonate and ethyl propionate is not particularly limited, but is in the range of 70 to 80% by volume with respect to the entire non-aqueous solvent. It is preferable to use it. If the content is 70% by volume or more, the viscosity of the non-aqueous electrolyte solution does not become too high, and if it is 80% by volume or less, the electrical conductivity of the non-aqueous electrolyte solution decreases and the electrochemical characteristics over a wide temperature range. Is less likely to decrease, so the above range is preferable.

In the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect, the volume ratio of the asymmetric chain carbonate to the chain carbonate is preferably 50% by volume or more, and is 52. More preferably by volume or more. The upper limit is more preferably 80% by volume or less, and further preferably 78% by volume or less. In the above case, the electrochemical characteristics in a wider temperature range are improved, which is preferable.

In the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect, the ratio of the cyclic carbonate, the chain carbonate and the chain ester is the viewpoint of improving the electrochemical properties at high temperature. Therefore, the cyclic carbonate: chain carbonate: chain ester (volume ratio) is preferably (20 to 30) :( 50 to 60) :( 10 to 20). In the above case, the electrochemical characteristics in a wider temperature range are improved, which is preferable.

Further, in the non-aqueous solvent used in the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect, other than cyclic carbonate, chain carbonate, and chain ester Other non-aqueous solvents may be included. Other non-aqueous solvents include cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and 1,4-dioxane, chains such as 1,2-dimethoxyethane, 1,2-diethoxyethane and 1,2-dibutoxyethane. One or more selected from amides such as ether, dimethylformamide, sulfolanes, and lactones such as γ-butyrolactone (GBL), γ-valerolactone, and α-angelica lactone are preferably mentioned.

The content of the other non-aqueous solvent is usually 1% by volume or more, preferably 2% by volume or more, and usually 20% by volume or less, preferably 10% by volume or less, more preferably 10% by volume or less, based on the whole non-aqueous solvent. It is 5% by volume or less.

For the purpose of improving the electrochemical properties in a wider temperature range, other additives may be added to the non-aqueous electrolytic solution according to the first aspect of the present invention and the non-aqueous electrolytic solution according to the second aspect of the present invention. preferable.
Specific examples of other additives include the following (A) S = O group-containing compound or (B) lithium salt compound.

(A) 1,3-Propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propensultone, 2,2-dioxide-1,2-oxathiolan-4-yl Acetate, or sultone such as 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, ethylene sulphite, hexahydrobenzo [1,3,2] dioxathiolane-2-oxide (1,2) -Cyclohexanediol cyclic sulphite), or cyclic sulphite such as 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, ethylene sultone, tetrahydro-4H-cyclopenta [d] [ 1,3,2] Dioxathiol-2,2-dioxide, [4,4'-bi (1,3,2-dioxathiolane)] 2,2', 2'-tetraoxide, (2,2-dioxide) Cyclic sulfates such as -1,3,2-dioxathiolan-4-yl) methyl methanesulfonate, or 4-((methylsulfonyl) methyl) -1,3,2-dioxathiolane 2,2-dioxide, butane-2,3 Sulfonic acid esters such as −diyl dimethanesulfonate, butane-1,4-diyldimethanesulfonate, or methylenemethane disulfonate, divinylsulfone, 1,2-bis (vinylsulfonyl) ethane, or bis (2-vinylsulfonylethyl). ) One or more S = O group-containing compounds selected from vinyl sulfonyl compounds such as ether.

Among these cyclic or chain S = O group-containing compounds selected from the group consisting of sulton, cyclic sulfite, cyclic sulfate, sulfonic acid ester, and vinyl sulfone, 1,3-propane sulton, 1,4- Butan Sulfone, 2,4-Butan Sulfone, 2,2-Dioxide-1,2-oxathiolane-4-yl acetate, and 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, ethylene sulfate, Tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2-dioxide, [4,5'-bi (1,3,2-dioxathiolane)] 2,2', 2'- From the group consisting of tetraoxide, (2,2-dioxide-1,3,2-dioxathiolan-4-yl) methylmethanesulfonate, butane-2,3-diyldimethanesulfonate, pentafluorophenylmethanesulfonate, and divinylsulfone. One or more selected are preferred. Furthermore, 1,3-propane sultone, 2,2-dioxide-1,2-oxathiolan-4-yl acetate, ethylene sulfate, tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2 , 2-Dioxide, [4,4'-bi (1,3,2-dioxathiolan)] 2,2', 2'-tetraoxide, (2,2-dioxide-1,3,2-dioxathiolan-4- Il) One or more selected from methyl methanesulfonate and pentafluorophenyl methanesulfonate are more preferable, and ethylene sulfate, tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2- More preferably, one or more cyclic sulfates selected from dioxide and [4,4'-bi (1,3,2-dioxathiolan)] 2,2', 2'-tetraoxide.

The content of the S = O group-containing compound is preferably 0.001 to 5% by mass in the non-aqueous electrolytic solution. In this range, the coating is sufficiently formed without becoming too thick, and the electrochemical properties in a wider temperature range are enhanced. The content is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, and the upper limit thereof is more preferably 3% by mass or less, further preferably 2% by mass or less in the non-aqueous electrolytic solution. ..

(B) Selected from 2,5,8,11-tetraoxadodecane (hereinafter, also referred to as “TOD”) and 2,5,8,11,14-pentaoxapentadecane (hereinafter, also referred to as “POP”) 1 Examples thereof include a lithium salt compound represented by the following general formula (II) or (III) consisting of a lithium cation having a species or more of an ether compound as a ligand and a difluorophosphate anion.

From the viewpoint of improving the electrochemical properties in a wide temperature range, the bis (difluorophosphoryl) (2,5,8,11-tetraoxadodecane) dilithium (TOD complex) represented by the above general formula (II) is more preferable. ..

The content of the lithium salt compound represented by the general formula (II) or (III) is preferably 0.01 to 5% by mass in the non-aqueous electrolytic solution. In this range, the coating is sufficiently formed without becoming too thick, and the electrochemical properties in a wider temperature range are enhanced. The content is more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, and the upper limit thereof is more preferably 4% by mass or less, further preferably 3% by mass or less in the non-aqueous electrolytic solution. ..

[Manufacturing of non-aqueous electrolyte]
The non-aqueous electrolytic solution according to the first aspect of the present invention and the non-aqueous electrolytic solution according to the second aspect are, for example, mixed with the non-aqueous solvent, and the lithium salt and the non-aqueous electrolytic solution are mixed with the non-aqueous solvent. It can be obtained by adding the additive of.
At this time, it is preferable that the non-aqueous solvent and the additive to be added to the non-aqueous electrolytic solution are purified in advance and have as few impurities as possible within a range that does not significantly reduce the productivity.

The non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect can be used in the following lithium secondary batteries or lithium ion capacitors, and are in a liquid state as non-aqueous electrolytes. Not only the ones but also the gelled ones can be used. Further, the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect can also be used for solid polymer electrolytes. Above all, it is more preferable to use it for a lithium secondary battery.

Since the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect contain each of the above components in the above proportions, the flash point is 20 ° C. or higher. It is preferably 20.5 ° C. or higher, and is excellent in stability in a high temperature environment.
Further, since the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect contain each of the above components in the above proportions, the freezing point is preferably −45. It is ℃ or less, more preferably −48 ℃ or less, still more preferably -50 ℃ or less, and has excellent electrical characteristics in a low temperature environment.
In addition, since the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect contain the above-mentioned components in the above-mentioned ratios, electrical conductivity at 25 ° C. The ratio is preferably 8 mS / cm or more, more preferably 8.1 mS / cm or more, still more preferably 8.3 mS / cm or more, still more preferably 9 mS / cm or more, and particularly preferably 9.1 mS or more. It is / cm or more, most preferably 9.3 mS / cm or more, and has excellent electrical conductivity.
Therefore, the non-aqueous electrolyte solution according to the first aspect of the present invention and the non-aqueous electrolyte solution according to the second aspect are used as a non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor, particularly in a wide temperature range. It is preferably used as a non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor.

[Lithium secondary battery]
In the present specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery.
The lithium secondary battery of the present invention is derived from the non-aqueous electrolytic solution according to the first aspect of the present invention and the non-aqueous electrolytic solution according to the second aspect, wherein the lithium salt is dissolved in the positive electrode, the negative electrode and the non-aqueous solvent. Become. Components other than the non-aqueous electrolyte solution, such as positive electrodes and negative electrodes, can be used without particular limitation.
For example, as the positive electrode active material for a lithium secondary battery, a composite metal oxide containing one or more selected from the group consisting of cobalt, manganese, and nickel, or iron, cobalt, nickel, and iron, cobalt, nickel, and Lithium-containing olivine-type phosphates containing one or more selected from manganese are used. These positive electrode active materials can be used alone or in combination of two or more.
Examples of such a lithium composite metal oxide, for _{example, LiCoO 2, LiMn 2 O 4} , LiNiO 2, LiCo 1-x Ni x O 2 (0.01 <x <1), LiNi x Mn y Co z O 2 (X + y + z = 1), solid solution of Li ₂ MnO ₃ and LiMO ₂ (M is a transition metal such as Co, Ni, Mn, Fe), LiNi _1/2 Mn _3/2 O ₄ , LiFePO ₄ , LiMnPO ₄ , And one or more selected from LiMn _1-x Fe _x PO ₄ (0.01 <x <1) are preferably mentioned, and two or more are more preferable. Some of these composite metal oxides with lithium or lithium-containing olivine-type phosphates may be replaced with other elements, and some of cobalt, nickel, manganese, and iron may be replaced with Co, Mn, Ni, Mg, Al. , B, Ti, V, Nb, Cu, Zn, Mo, Ca, Sr, W, and Zr, a compound or carbon material that is substituted with one or more elements selected from, or contains these other elements. It can also be covered with.

When a lithium composite metal oxide operating at a high charging voltage is used, the electrochemical characteristics tend to deteriorate in a high temperature environment due to the reaction with the electrolytic solution during charging. However, in the lithium secondary battery according to the present invention, these electrochemical properties are likely to deteriorate. It is possible to suppress the deterioration of the characteristics.
As for the voltage during charging, the positive electrode potential is 4.3 V (vs. Li / Li) from the viewpoint of increasing the voltage. ^＋) Or more is preferable, 4.35V (vs. Li / Li)^＋) Or more is more preferable, 4.4V (vs. Li / Li)^＋) The above is particularly preferable.
Further, in the case of a positive electrode active material containing Ni, the catalytic action of Ni causes decomposition of the non-aqueous solvent on the surface of the positive electrode, and the resistance of the battery tends to increase. In particular, the electrochemical properties tend to deteriorate in a high temperature environment, but the lithium secondary battery according to the present invention is preferable because it can suppress the deterioration of these electrochemical properties. In particular, when the ratio of the atomic concentration of Ni to the atomic concentration of all transition metal elements in the positive electrode active material exceeds 10 atomic%, the above effect becomes remarkable, and 20 atomic% or more is more preferable. , 30 atomic% or more is particularly preferable. Specifically, LiCo_1/3Ni_1/3Mn_1/3O ₂, LiNi_0.5Mn_0.3Co_0.2Mn_0.3O₂, LiNi_0.8Mn_0.1Co_0.1O₂, LiNi_0.8Co_0.15Al_0.05O₂Etc. are preferably mentioned.

Examples of the positive electrode for a lithium primary battery include metal oxides such as MnO ₂ , sulfur compounds such as SOCl ₂ , and fluorocarbon (fluoride graphite) represented by the general formula (CF _x ) _n . Among these, MnO ₂ , graphite fluoride and the like are preferable.

The conductive agent for the positive electrode is not particularly limited as long as it is an electron conductive material that does not cause a chemical change. Examples thereof include natural graphite (scaly graphite and the like), graphite such as artificial graphite, acetylene black, Ketjen black, channel black, furnace black, lamp black, carbon black such as thermal black and the like. Further, graphite and carbon black may be appropriately mixed and used. The amount of the conductive agent added to the positive electrode mixture is preferably 1 to 10% by mass, and particularly preferably 2 to 5% by mass.

For the positive electrode, the positive electrode active material is used as a conductive agent such as acetylene black or carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), and carboxymethyl cellulose (CMC). ), Etc., and a high boiling point solvent such as 1-methyl-2-pyrrolidone is added to the mixture to form a positive electrode mixture slurry, which is then placed on an aluminum foil of the current collector. It can be produced by applying, drying, and pressurizing to form a positive electrode mixture layer.
The density of the part except the collector of the positive electrode is usually at 1.5 g / cm ³ or more, for further increasing the capacity of the battery, it is preferably 2 g / cm ³ or more, more preferably, 3 g / cm ³ The above is more preferably 3.6 g / cm ³ or more. The upper limit thereof is preferably 4 g / cm ³ or less.

As the negative electrode active material for a lithium secondary battery, a lithium metal, a lithium alloy, and a carbon material capable of storing and releasing lithium [graphitized carbon and a (002) plane spacing of 0.37 nm or more). Graphite-resistant carbon, graphite with a (002) plane spacing of 0.34 nm or less], tin (elemental substance), tin compounds such as SnO _x (1≤x <2), silicon (elemental substance), SiO _x ( A silicon compound such as 1 ≦ x <2) or a lithium titanate compound such as Li ₄ Ti ₅ O ₁₂ can be used alone or in combination of two or more.
Among these, the storage and release capability of lithium ions, it is more preferable to use a highly crystalline carbon materials such as artificial graphite and natural graphite, spacing of lattice planes ₍₀₀₂₎ (d 0 ₀₂₎ 0 It is more preferable to use a carbon material having a graphite-type crystal structure of .340 nm (nanometer) or less, particularly 0.335 to 0.337 nm.
The peak intensity I (110) of the (110) plane of the graphite crystal obtained from the X-ray diffraction measurement of the negative electrode sheet when the density of the portion of the negative electrode excluding the current collector is pressure-molded to a density of 1.5 g / cm ³ or more. ) And the peak intensity I (004) of the plane (004) when I (110) / I (004) is 0.01 or more, the electrochemical characteristics in a wider temperature range are improved, which is preferable, 0.05 or more. Is more preferable, and 0.1 or more is further preferable. Further, since the crystallinity may be lowered due to excessive treatment and the discharge capacity of the battery may be lowered, the upper limit of the peak intensity ratio I (110) / I (004) is preferably 0.5 or less, and 0. 3 or less is more preferable.
Further, it is preferable that the highly crystalline carbon material (core material) is coated with a carbon material having a lower crystallinity than the core material because the electrochemical properties in a wide temperature range are further improved. The crystallinity of the coated carbon material can be confirmed by TEM.
When a highly crystalline carbon material is used, it reacts with a non-aqueous electrolytic solution during charging and tends to reduce the electrochemical properties at low or high temperatures due to an increase in interfacial resistance. However, in the lithium secondary battery according to the present invention. Good electrochemical properties over a wide temperature range.

The negative electrode is kneaded with a conductive agent, a binder, and a high boiling point solvent similar to those for producing the positive electrode described above to form a negative electrode mixture slurry, which is then applied onto a copper foil or the like of a current collector and dried. , It can be produced by pressurizing to form a positive electrode mixture layer.
The density of the portion of the negative electrode excluding the current collector is usually 1.1 g / cm ³ or more, and is preferably 1.5 g / cm ³ or more, more preferably 1.7 g in order to further increase the capacity of the battery. / Cm ³ or more. The upper limit thereof is preferably 2 g / cm ³ or less.

Moreover, as a negative electrode active material for a lithium primary battery, a lithium metal or a lithium alloy is preferably mentioned.

The structure of the lithium battery is not particularly limited, and a coin-type battery having a single-layer or multi-layer separator, a cylindrical battery, a square battery, a laminated battery, or the like can be applied.
The battery separator is not particularly limited, but a monolayer or laminated microporous film of polyolefin such as polypropylene or polyethylene, a woven fabric, or a non-woven fabric can be used.

The lithium secondary battery in the present invention has excellent electrochemical characteristics in a wide temperature range even when the charge termination voltage is 4.2 V or more, particularly 4.3 V or more, and further, the characteristics are also good at 4.4 V or more. is there. The discharge end voltage can usually be 2.8 V or higher, further 2.5 V or higher, but the lithium secondary battery in the present invention can be 2.0 V or higher. The current value is not particularly limited, but is usually used in the range of 0.1 to 30C. Further, the lithium battery in the present invention can be charged and discharged at -40 to 100 ° C, preferably -20 to 80 ° C.

[Lithium ion capacitor]
The lithium ion capacitor of the present invention is a power storage device that stores energy by utilizing the intercalation of lithium ions with a carbon material such as graphite which is a negative electrode. The lithium ion capacitor of the present invention comprises a non-aqueous electrolytic solution according to the first aspect of the present invention and a non-aqueous electrolytic solution according to the second aspect, in which a lithium salt is dissolved in a positive electrode, a negative electrode and a non-aqueous solvent. .. It is called a lithium ion capacitor (LIC). Examples of the positive electrode include those using an electric double layer between the activated carbon electrode and the electrolytic solution, those using the doping / dedoping reaction of the π-conjugated polymer electrode, and the like. The electrolytic solution contains at least a lithium salt such as LiPF ₆ . Further, as the negative electrode, the same one as the above-mentioned lithium secondary battery can be used.

Hereinafter, examples of the non-aqueous electrolyte solution of the present invention will be shown, but the present invention is not limited to these examples.

Examples 1-14, Comparative Examples 1-8
[Measurement of physical properties of non-aqueous electrolyte]
<Measurement of flash point>
The flash point of the non-aqueous electrolyte solution shown in Tables 1 and 2 is measured based on the JIS K-2265 standard using a tag-sealed flash point tester (manufactured by Tanaka Scientific Instruments Manufacturing Co., Ltd .; model ATG-7). did.
<Measurement of freezing point>
The freezing points of the non-aqueous electrolytes shown in Tables 1 and 2 were measured using an automatic freezing point meter (manufactured by Electrochemical Systems Co., Ltd .; model CP-2BX) based on the JIS K-0065 standard.
<Measurement of electrical conductivity>
The electric conductivity of the non-aqueous electrolytes shown in Tables 1 and 2 was measured in an environment of 25 ° C. using an electric conductivity meter (manufactured by DKK-TOA CORPORATION; model CM-30R).
Each physical property value is shown in Tables 1 and 2.

[Manufacturing of lithium ion secondary battery]
LiNi _0.5 Mn _0.3 Co _0.2 O ₂ ; 92% by mass, acetylene black (conductive agent); 5% by mass is mixed, and polyvinylidene fluoride (binding agent); 3% by mass is 1-methyl in advance. -2-Pyrrolidone was added to the dissolved solution and mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to one side on an aluminum foil (current collector), dried and pressure-treated, and cut into a predetermined size to prepare a positive electrode sheet. The density of the portion of the positive electrode excluding the current collector was 3.6 g / cm ³ . Further, silicon (single substance); 7% by mass, artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material); 85% by mass, acetylene black (conductive agent); 5% by mass are mixed, and polyvinylidene fluoride (condensation) is prepared in advance. Adhesive); 5% by mass was added to the solution dissolved in 1-methyl-2-pyrrolidone and mixed to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side on a copper foil (current collector), dried and pressure-treated, and cut into a predetermined size to prepare a negative electrode sheet. The density of the portion of the negative electrode excluding the current collector was 1.6 g / cm ³ . Further, as a result of X-ray diffraction measurement using this electrode sheet, the ratio [I (110) / I) of the peak intensity I (110) on the (110) plane and the peak intensity I (004) on the (004) plane of the graphite crystal. (004)] was 0.1. Then, the positive electrode sheet, the separator made of a microporous polyethylene film, and the negative electrode sheet were laminated in this order, and the non-aqueous electrolytic solution having the composition shown in Table 1 or Table 2 was added to prepare a laminated battery.

[Evaluation of low temperature characteristics after high temperature charge storage]
<Initial discharge capacity>
Using the laminated battery produced by the above method, the final voltage is 4.4 V (the charging potential of the positive electrode is 4.5 V (vs. Li ^/ Li ⁺ )) at a constant current and constant voltage of 1 C in a constant temperature bath at 25 ° C. ) Was charged for 3 hours, the temperature of the constant temperature bath was lowered to −20 ° C., and the battery was discharged to a final voltage of 2.75 V under a constant current of 1C to obtain the initial discharge capacity of −20 ° C.
<High temperature charge storage test>
Next, this laminated battery was charged in a constant temperature bath at 85 ° C. at a constant current and constant voltage of 1 C to a final voltage of 4.4 V for 3 hours, and stored at 4.4 V for 2 days. After storage for 2 days, battery swelling was confirmed immediately after taking out from the constant temperature bath. Specifically, the relative value was obtained when the thickness change of the laminated battery of Comparative Example 3 before and after storage was set to 100. Then, it was placed in a constant temperature bath at 25 ° C. and once discharged to a final voltage of 2.75 V under a constant current of 1 C.
<Discharge capacity after high temperature charge storage>
After that, the discharge capacity at −20 ° C. after high-temperature charge storage was determined in the same manner as in the initial measurement of the discharge capacity.
<Low temperature characteristics after high temperature charge storage>
The low temperature characteristics after high temperature charge storage were determined from the retention rate of the -20 ° C discharge capacity below.
-20 ° C discharge capacity retention rate (%) after high-temperature charge storage = (-20 ° C discharge capacity after high-temperature charge storage / initial -20 ° C discharge capacity) x 100
The battery characteristics are shown in Tables 1 and 2.
In Tables 1 to 3, "EC" is ethylene carbonate, "PC" is propylene carbonate, "DMC" is dimethyl carbonate, "EP" is ethyl propionate, "MEC" is methyl ethyl carbonate, and "TFEMC" is 2,2,2-Trifluoroethyl methyl carbonate, "DFEA" is 2,2-difluoroethyl acetate, "TFEA" is 2,2,2-trifluoroethyl acetate, "DFEMC" is 2,2-difluoroethyl methyl Carbonate, "VC" is vinylene carbonate, "FEC" is 4-fluoro-1,3-dioxolan-2-one, "TCDD" is tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol- 2,2-Dioxide, "TOD complex" is an abbreviation for bis (difluorophosphoryl) (2,5,8,11-tetraoxadodecane) dilithium.

Examples 15-25 and Comparative Examples 9-16
[Manufacturing of lithium ion capacitors]
Activated carbon powder with a specific surface area of 600 to 3000 m ² / g; 92% by mass, acetylene black (conductive agent); 5% by mass is mixed, and polyvinylidene fluoride (binding agent); 3% by mass is 1-methyl-2-. The mixture was added to the solution dissolved in pyrrolidone and mixed to prepare a positive mixture paste. This positive electrode mixture paste was applied to one side on an aluminum foil (current collector), dried and pressure-treated, and cut into a predetermined size to prepare a positive electrode sheet. Further, 95% by mass of artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material) was added to a solution in which 5% by mass of polyvinylidene fluoride (binder) was previously dissolved in 1-methyl-2-pyrrolidone. And mixed to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side on a copper foil (current collector), dried and pressure-treated, and cut into a predetermined size to prepare a negative electrode sheet. The density of the portion of the negative electrode excluding the current collector was 1.5 g / cm ³ . Further, as a result of X-ray diffraction measurement using this electrode sheet, the ratio of the peak intensity I (110) on the (110) plane and the peak intensity I (004) on the (004) plane [I (110) / I) of the graphite crystal. (004)] was 0.1. After heating and vacuum-drying the positive electrode and the negative electrode prepared as described above, lithium ions having an electric amount of 372 mAh / g per unit mass of the negative electrode active material were electrochemically occluded. Then, the positive electrode sheet, the separator made of a microporous polyethylene film, and the negative electrode sheet were laminated in this order, and the non-aqueous electrolytic solution having the composition shown in Table 3 was added to prepare a laminated battery.

[Evaluation of low temperature characteristics after high temperature charge storage]
<Initial discharge capacity>
Using the laminated battery produced by the above method, in a constant temperature bath at 25 ° C., at a constant current and constant voltage of 1C, the final voltage is 4.3V (the charging potential of the positive electrode is 4.4V (vs. Li ^/ Li ⁺ )). ) V was charged for 3 hours, the temperature of the constant temperature bath was lowered to −20 ° C., and the battery was discharged to a final voltage of 3 V under a constant current of 10 C to obtain the initial cell capacity of −20 ° C.
<High temperature charge storage test>
Next, this laminated battery was charged in a constant temperature bath at 85 ° C. at a constant current and constant voltage of 1 C to a final voltage of 4.3 V for 3 hours, and stored at 4.3 V for 2 days. After storage for 2 days, the presence or absence of battery swelling was confirmed immediately after taking out from the constant temperature bath. Specifically, the relative value was obtained when the thickness change of the laminated battery of Comparative Example 11 before and after storage was set to 100. Then, it was placed in a constant temperature bath at 25 ° C. and once discharged to a final voltage of 3 V under a constant current of 10 C.
<Discharge capacity after high temperature charge storage>
After that, the cell capacity at −20 ° C. after high-temperature charge storage was determined in the same manner as in the initial measurement of the discharge capacity.
<Low temperature characteristics after high temperature charge storage>
The low temperature characteristics after high temperature charge storage were determined from the retention rate of the cell capacity at −20 ° C. below.
-20 ° C cell capacity retention rate (%) after high-temperature charge storage = (-20 ° C cell capacity after high-temperature charge storage / initial -20 ° C cell capacity) x 100
The capacitor characteristics are shown in Table 3.

[Evaluation of Examples 1 to 14, Comparative Examples 1 to 8, Examples 15 to 25 and Comparative Examples 9 to 16]
The lithium secondary batteries of Examples 1 to 14 are all lithium of Comparative Examples 1 to 8 when a non-aqueous electrolytic solution containing a non-aqueous solvent mixed with the non-aqueous electrolytic solution of the present invention in a composition ratio different from that of the present invention is used. Compared to secondary batteries, the electrochemical characteristics over a wide temperature range are significantly improved. From the above, it was found that the effect of the present invention is a peculiar effect when the non-aqueous electrolytic solution having a specific composition of the present invention is used.
Further, from the comparison between Examples 15 to 25 and Comparative Examples 9 to 16, it was found that the same effect was obtained when the lithium capacitor was used.

Further, the non-aqueous electrolyte solution according to the first aspect of the present invention also has an effect of improving the discharge characteristics in a wide temperature range of the lithium primary battery.

Examples 26-33, Comparative Examples 17-24
[Measurement of physical properties of non-aqueous electrolyte]
<Measurement of flash point>
The flash points of the non-aqueous electrolyte solutions shown in Tables 4 and 5 are measured using a tag-sealed flash point tester (manufactured by Tanaka Scientific Instruments Manufacturing Co., Ltd .; model ATG-7) based on the JIS K-2265 standard. did.
<Measurement of freezing point>
The freezing points of the non-aqueous electrolytes shown in Tables 4 and 5 were measured using an automatic freezing point meter (manufactured by Electrochemical Systems Co., Ltd .; model CP-2BX) based on the JIS K-0065 standard.
<Measurement of electrical conductivity>
The electric conductivity of the non-aqueous electrolytes shown in Tables 4 and 5 was measured in an environment of 25 ° C. using an electric conductivity meter (manufactured by DKK-TOA CORPORATION; model CM-30R).
Each physical property value is shown in Tables 4 to 5.

[Manufacturing of lithium ion secondary battery]
LiNi _0.33 Mn _0.33 Co _0.34 O ₂ ; 93% by mass, acetylene black (conductive agent); 4% by mass is mixed, and polyvinylidene fluoride (binding agent); 3% by mass is 1-methyl in advance. -2-Pyrrolidone was added to the dissolved solution and mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to one side on an aluminum foil (current collector), dried and pressure-treated, and cut into a predetermined size to prepare a positive electrode sheet. The density of the portion of the positive electrode excluding the current collector was 3.6 g / cm ³ . Further, silicon (single substance); 5% by mass, artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material); 85% by mass, acetylene black (conductive agent); 5% by mass are mixed, and polyvinylidene fluoride (condensation) is prepared in advance. Adhesive); 5% by mass was added to the solution dissolved in 1-methyl-2-pyrrolidone and mixed to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side on a copper foil (current collector), dried and pressure-treated, and cut into a predetermined size to prepare a negative electrode sheet. The density of the portion of the negative electrode excluding the current collector was 1.6 g / cm ³ . Further, as a result of X-ray diffraction measurement using this electrode sheet, the ratio of the peak intensity I (110) on the (110) plane and the peak intensity I (004) on the (004) plane [I (110) / I) of the graphite crystal. (004)] was 0.1. Then, the positive electrode sheet, the separator made of a microporous polyethylene film, and the negative electrode sheet were laminated in this order, and the non-aqueous electrolytic solution having the composition shown in Tables 4 and 5 was added to prepare a laminated battery.

[Evaluation of low temperature characteristics after high temperature charge storage]
<Initial discharge capacity>
Using the laminated battery produced by the above method, the battery was charged in a constant temperature bath at 25 ° C. with a constant current and constant voltage of 1C to a final voltage of 4.35 V for 3 hours, and the temperature of the constant temperature bath was lowered to −20 ° C. The discharge was performed to a final voltage of 2.75 V under a constant current of 1C, and the initial discharge capacity at −20 ° C. was determined.
<High temperature charge storage test>
Next, this laminated battery was charged in a constant temperature bath at 60 ° C. at a constant current and constant voltage of 1 C to a final voltage of 4.3 V for 3 hours, and stored at 4.35 V for 14 days. After storage for 14 days, the presence or absence of battery swelling was confirmed immediately after taking out from the constant temperature bath. Specifically, when the thickness of the laminated battery before storage is 100%, the thickness after storage is 110% or more, and it is considered that there is swelling. Then, it was placed in a constant temperature bath at 25 ° C. and once discharged to a final voltage of 2.75 V under a constant current of 1 C.
<Discharge capacity after high temperature charge storage>
After that, the discharge capacity at −20 ° C. after high-temperature charge storage was determined in the same manner as in the initial measurement of the discharge capacity.
<Low temperature characteristics after high temperature charge storage>
The low temperature characteristics after high temperature charge storage were determined from the retention rate of the -20 ° C discharge capacity below.
-20 ° C discharge capacity retention rate (%) after high-temperature charge storage = (-20 ° C discharge capacity after high-temperature charge storage / initial -20 ° C discharge capacity) x 100
The battery characteristics are shown in Tables 4-5.
In Tables 4 to 6, "EC" is ethylene carbonate, "PC" is propylene carbonate, "DMC" is dimethyl carbonate, "EP" is ethyl propionate, "MEC" is methyl ethyl carbonate, and "MP" is Methylpropionate, "VC" is vinylene carbonate, "FEC" is 4-fluoro-1,3-dioxolan-2-one, "TCDD" is tetrahydro-4H-cyclopenta [d] [1,3,2] di Oxathiol-2,2-dioxide, "TOD complex" is an abbreviation for bis (difluorophosphoryl) (2,5,8,11-tetraoxadodecane) dilithium.

Examples 34 to 37, Comparative Examples 25 to 32
[Manufacturing of lithium ion capacitors]
Activated carbon powder with a specific surface area of 600 to 3000 m ² / g; 92% by mass, acetylene black (conductive agent); 5% by mass is mixed, and polyvinylidene fluoride (binding agent); 3% by mass is 1-methyl-2-. The mixture was added to the solution dissolved in pyrrolidone and mixed to prepare a positive mixture paste. This positive electrode mixture paste was applied to one side on an aluminum foil (current collector), dried and pressure-treated, and punched to a predetermined size to prepare a positive electrode sheet. Further, 95% by mass of artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material) was added to a solution in which 5% by mass of polyvinylidene fluoride (binder) was previously dissolved in 1-methyl-2-pyrrolidone. And mixed to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side on a copper foil (current collector), dried and pressure-treated, and cut into a predetermined size to prepare a negative electrode sheet. The density of the portion of the negative electrode excluding the current collector was 1.5 g / cm ³ . Further, as a result of X-ray diffraction measurement using this electrode sheet, the ratio of the peak intensity I (110) on the (110) plane and the peak intensity I (004) on the (004) plane [I (110) / I) of the graphite crystal. (004)] was 0.1. After heating and vacuum-drying the positive electrode and the negative electrode prepared as described above, lithium ions having an electric amount of 372 mAh / g per unit mass of the negative electrode active material were electrochemically occluded. Then, the positive electrode sheet, the separator made of a microporous polyethylene film, and the negative electrode sheet were laminated in this order, and the non-aqueous electrolytic solution having the composition shown in Table 6 was added to prepare a laminated battery.

[Evaluation of low temperature characteristics after high temperature charge storage]
<Initial discharge capacity>
Using the laminated battery produced by the above method, the battery was charged in a constant temperature bath at 25 ° C. with a constant current and constant voltage of 1C to a final voltage of 4.2 V for 3 hours, and the temperature of the constant temperature bath was lowered to −20 ° C. The cell was discharged to a final voltage of 3 V under a constant current of 10 C, and the initial cell capacity of −20 ° C. was determined.
<High temperature charge storage test>
Next, this laminated battery was charged in a constant temperature bath at 60 ° C. at a constant current and constant voltage of 1 C to a final voltage of 4.3 V for 3 hours, and stored at 4.3 V for 7 days. After storage for 14 days, the presence or absence of battery swelling was confirmed immediately after taking out from the constant temperature bath. Specifically, when the thickness of the laminated battery before storage is 100%, the thickness after storage is 110% or more, and it is considered that there is swelling. Then, it was placed in a constant temperature bath at 25 ° C. and once discharged to a final voltage of 3 V under a constant current of 10 C. <Discharge capacity after high temperature charge storage>
After that, the cell capacity at −20 ° C. after high-temperature charge storage was determined in the same manner as in the initial measurement of the discharge capacity.
<Low temperature characteristics after high temperature charge storage>
The low temperature characteristics after high temperature charge storage were determined from the retention rate of the cell capacity at −20 ° C. below.
-20 ° C cell capacity retention rate (%) after high-temperature charge storage = (-20 ° C cell capacity after high-temperature charge storage / initial -20 ° C cell capacity) x 100
The capacitor characteristics are shown in Table 6.

[Evaluation of Examples 26 to 33 and Comparative Examples 17 to 24, Examples 34 to 37 and Comparative Examples 25 to 32]
The lithium secondary batteries of Examples 26 to 33 are all lithium of Comparative Examples 17 to 24 when a non-aqueous electrolyte solution containing a non-aqueous solvent mixed with the non-aqueous electrolyte solution of the present invention in a different composition ratio is used. Compared to secondary batteries, the electrochemical characteristics over a wide temperature range are significantly improved. From the above, it was found that the effect of the present invention is a peculiar effect when the non-aqueous electrolytic solution having a specific composition of the present invention is used.
Further, from the comparison between Examples 34 to 37 and Comparative Examples 25 to 32, it was found that the same effect was obtained when the lithium capacitor was used.

Further, the non-aqueous electrolyte solution according to the second aspect of the present invention also has an effect of improving the discharge characteristics of the lithium primary battery in a wide temperature range.

If the non-aqueous electrolytic solution according to the first aspect of the present invention and the non-aqueous electrolytic solution according to the second aspect are used, a lithium secondary battery that can be used at a high potential and has excellent electrochemical characteristics in a wide temperature range. Alternatively, a lithium ion capacitor can be obtained. In particular, when used as a non-aqueous electrolyte for power storage devices such as lithium secondary batteries installed in hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, etc., lithium ion does not easily deteriorate in electrochemical characteristics over a wide temperature range. A secondary battery or a lithium ion capacitor can be obtained.

Claims (13)

In a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.8 to 1.5 M (mol / L).
The non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 20 to 40% by volume of methyl ethyl carbonate with respect to the whole non-aqueous solvent. , And 10 to 20% by volume of fluorinated chain ester,
The total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and the total content of dimethyl carbonate and fluorinated chain ester is 30 to 40% by volume.
A non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor, characterized in that the flash point of the non-aqueous electrolyte solution is 20 ° C. or higher. In a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.9 to 1.5 M (mol / L).
The non-aqueous solvent is 5 to 25% by volume of ethylene carbonate, 5 to 25% by volume of propylene carbonate, 20 to 30% by volume of dimethyl carbonate, and 20 to 40% by volume of methyl ethyl carbonate with respect to the whole non-aqueous solvent. , And containing 10 to 20% by volume of ethyl propionate,
The total content of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 20 to 30% by volume, and the total content of dimethyl carbonate and ethyl propionate is 30 to 40% by volume.
A non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor, characterized in that the ignition point of the non-aqueous electrolyte solution is 20 ° C. or higher (provided that a lithium salt is 1.1 to 1.5 M in a non-aqueous solvent). In the non-aqueous electrolyte solution dissolved in an amount of (mol / L), the non-aqueous solvent is 5 to 20% by volume of ethylene carbonate and 5 to 25% by volume of propylene carbonate with respect to the entire non-aqueous solvent. 20 to 30% by volume of dimethyl carbonate, 10 to 20% by volume of ethyl propionate, and 30 to 40% by volume of methyl ethyl carbonate, the total of ethylene carbonate and propylene carbonate in the non-aqueous solvent. The content is 20 to 30% by volume, the total content of dimethyl carbonate and ethyl propionate is 30 to 40% by volume, and the ignition point of the non-aqueous electrolyte solution is 20 ° C. or higher. Excludes non-aqueous electrolytes for lithium secondary batteries or lithium ion capacitors.) The fluorinated chain ester is 2,2-difluoroethyl acetate (DFEA), 2,2,2-trifluoroethyl acetate (TFEA), 2,2-difluoroethyl methyl carbonate (DFEMC), 2,2,2. -Selected from the group consisting of triluoloethyl methyl carbonate (TFEMC), methyltrifluoroacetate, ethyltrifluoroacetate, 2,2-difluoroethyltrifluoroacetate, and 2,2,2-trifluoroethyltrifluoroacetate 1 The non-aqueous electrolyte solution according to claim 1, which is characterized by having more than one species. The non-aqueous electrolyte solution for a lithium secondary battery or a lithium ion capacitor according to claim 1 or 2, wherein the freezing point of the non-aqueous electrolyte solution is −45 ° C. or lower. The non-aqueous electrolytic solution according to any one of claims 1 to 4, further comprising vinylene carbonate in an amount of 0.1 to 5% by volume based on the entire non-aqueous solvent. The non-aqueous electrolytic solution according to any one of claims 1 to 5, further comprising a fluoroethylene carbonate in an amount of 1 to 10% by volume based on the total amount of the non-aqueous solvent. The lithium salts are LiPF ₆ , (FSO ₂ ) ₂ NLi, LiPO ₂ F ₂ , lithium methyl sulfate, lithium ethyl sulfate, FSO ₃ Li, lithium difluoro (oxalat) borate, lithium tetrafluoro (oxalat) phosphate, lithium difluorobis. The non-aqueous electrolyte solution according to any one of claims 1 to 6, which comprises at least one selected from the group consisting of (oxalate) phosphate and lithium bis (oxalate) borate. The non-aqueous electrolytic solution according to any one of claims 1 to 7 in a lithium secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent. A lithium secondary battery characterized by being a liquid. The lithium secondary battery according to claim 8, wherein the positive electrode contains at least one selected from a lithium composite metal oxide and a lithium-containing olivine-type phosphate as a positive electrode active material. The negative electrode is selected from lithium metal, lithium alloy, a carbon material capable of occluding and releasing lithium, tin (elemental substance), tin compound, silicon (elemental substance), silicon compound, and lithium titanate compound as the negative electrode active material. The lithium secondary battery according to claim 8 or 9, wherein the lithium secondary battery comprises at least one of them. The non-aqueous electrolyte solution according to any one of claims 1 to 7 in a lithium ion capacitor including a positive electrode, a negative electrode, and a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent. A lithium ion capacitor characterized by being. The lithium ion capacitor according to claim 11, wherein the positive electrode contains activated carbon as a positive electrode active material. The negative electrode is selected from lithium metal, lithium alloy, a carbon material capable of occluding and releasing lithium, tin (elemental substance), tin compound, silicon (elemental substance), silicon compound, and lithium titanate compound as the negative electrode active material. The lithium ion capacitor according to claim 11 or 12, which comprises at least one of the above.