JP6737280B2 - Non-aqueous electrolyte for power storage device and power storage device using the same - Google Patents

Description

The present invention relates to a non-aqueous electrolyte solution for an electricity storage device that can improve electrochemical characteristics in a wide temperature range and an electricity storage device using the same.

In recent years, power storage devices, particularly lithium secondary batteries, have been widely used as power sources for small electronic devices such as mobile phones and notebook computers, as well as power sources for electric vehicles and power storage. Since these electronic devices and automobiles may be used in a wide temperature range such as high temperature in midsummer and low temperature in extremely cold, it is required to improve electrochemical characteristics in a well-balanced manner over a wide temperature range. ..
In particular, in order to prevent global warming, there is an urgent need to reduce CO ₂ emissions, and even among environmentally friendly vehicles equipped with power storage devices such as lithium secondary batteries and lithium ion capacitors, hybrid electric The early spread of vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV) is required. Because of the long travel distances of automobiles, they may be used in a wide range of temperatures from extremely hot tropical regions to extremely cold regions. Therefore, it is particularly required that these on-vehicle electricity storage devices have no deterioration in electrochemical characteristics even when used in a wide temperature range from high temperature to low temperature.
In addition, in this specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery.

A lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of inserting and extracting lithium ions, a lithium salt, and a non-aqueous electrolytic solution containing a non-aqueous solvent. As a non-aqueous solvent, ethylene carbonate (EC) is used. ), carbonates such as propylene carbonate (PC) are used.
Known negative electrodes for lithium secondary batteries include metallic lithium, metallic compounds capable of occluding and releasing lithium ions (metal simple substance, metal oxide, alloy with lithium, etc.) and carbon materials. In particular, lithium secondary batteries using carbon materials such as coke, artificial graphite and natural graphite capable of inserting and extracting lithium ions have been widely put into practical use.

For example, a lithium secondary battery using a highly crystallized carbon material such as natural graphite or artificial graphite as a negative electrode material has a decomposition product or a product generated by reductive decomposition of the solvent in the non-aqueous electrolyte on the negative electrode surface during charging. It has been found that the gas interferes with the desired electrochemical reaction of the cell, resulting in poor cycling characteristics. Further, when the decomposition product of the non-aqueous solvent accumulates on the electrode surface, it becomes impossible to smoothly occlude and release lithium into the negative electrode, and the electrochemical characteristics tend to deteriorate when used in a wide temperature range.
Furthermore, a lithium secondary battery using a lithium metal or its alloy, a metal simple substance such as tin or silicon, or a metal oxide as a negative electrode material has a high initial capacity, but since it is pulverized during a cycle, a It is known that the reductive decomposition of the non-aqueous solvent occurs more rapidly than that of the negative electrode, and the battery performance such as the battery capacity and cycle characteristics is significantly reduced. Further, due to the pulverization of these negative electrode materials and the accumulation of decomposition products of the non-aqueous solvent, it becomes impossible to smoothly occlude and release lithium into the negative electrode, and the electrochemical characteristics tend to deteriorate when used in a wide temperature range. ..

On the other hand, a lithium secondary battery using, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO ₄ or the like as a positive electrode material is a positive electrode material and a non-aqueous electrolyte solution when the non-aqueous solvent in the non-aqueous electrolyte solution is in a charged state. At the interface with and, the decomposition products and gases generated by partial oxidative decomposition locally interfere with the desired electrochemical reaction of the battery, so that the electrochemical characteristics also deteriorate when used in a wide temperature range. I know that.

As described above, the decomposition product or gas when the non-aqueous electrolyte solution is decomposed on the positive electrode or the negative electrode impedes the movement of lithium ions or swells the battery, thereby lowering the battery performance. Despite such circumstances, electronic devices equipped with lithium secondary batteries are becoming more and more multifunctional, and power consumption is increasing. As a result, the capacity of lithium secondary batteries is becoming higher and higher, increasing the density of the electrodes and reducing the wasted space volume in the battery.The volume occupied by the non-aqueous electrolyte in the battery is small. Has become. Therefore, even if the non-aqueous electrolyte is decomposed a little, the electrochemical characteristics are likely to deteriorate when used in a wide temperature range.
Patent Document 1 describes that a non-aqueous electrolyte containing a cyclic sulfate such as ethylene glycol sulfate can suppress capacity deterioration due to charge/discharge cycles.
In Patent Document 2, hexahydro 1,3,2-benzodioxathiol 2,2-dioxide (6-membered ring sulfuric acid ester), 1,2-cyclohexanediol cyclic sulfite (6-membered ring sulfite ester), etc. It is described that the non-aqueous electrolytic solution containing the 2,2-cyclohexanediol derivative (6-membered ring compound) has excellent long-term cycle characteristics and can suppress the gas generation amount.
Further, in Patent Document 3, a non-aqueous electrolytic solution containing a cyclic (5-membered ring) carbonic acid ester compound such as 1,2-cyclopentanediol cyclic carbonate is disclosed as a room temperature cycle characteristic of a secondary battery, a storage characteristic and a low temperature. It is described that the cycle characteristics are improved.

Japanese Patent Laid-Open No. 10-189042 International Publication No. 2007/020876 Japanese Patent Laid-Open No. 2011-124008

It is an object of the present invention to provide a non-aqueous electrolyte solution for an electricity storage device that can improve electrochemical characteristics in a wide temperature range and an electricity storage device using the same.

As a result of detailed investigations on the performance of the above-described conventional non-aqueous electrolytes, the present inventors have found that the secondary batteries using the non-aqueous electrolytes of Patent Documents 1 and 3 have low temperature discharge characteristics after high temperature storage. The fact is that the effect of improving the electrochemical characteristics in a wide temperature range has not been sufficiently obtained. In addition, there is room for improvement in the nonaqueous electrolytic solution of Patent Document 2.
Therefore, the inventors of the present invention have conducted extensive studies in order to solve the above problems, and in a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, a cyclopentane structure represented by the following general formula (I) The present invention has been completed by discovering that the electrochemical characteristics of a power storage device, particularly the electrochemical characteristics of a lithium battery can be improved in a wide temperature range by containing at least one compound selected from sulfate ester and sulfite ester containing Such effects are not suggested at all in Patent Documents 1 to 3 above.

That is, the present invention provides the following (1) and (2).
(1) A non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte solution contains 0.01 to 10% by mass of a compound represented by the following general formula (I). A non-aqueous electrolyte solution for an electricity storage device.

（式中、ＸはＳ（＝Ｏ）_２基又はＳ＝Ｏ基を示し、Ｒ^１〜Ｒ^８は、それぞれ独立して水素原子、ハロゲン原子、又は水素原子の一部がハロゲン原子で置換されていてもよい炭素数１〜４のアルキル基を示す。）

(In the formula, X represents an S(═O) ₂ group or an S═O group, and R ^{1 to} R ⁸ are each independently a hydrogen atom, a halogen atom, or a part of the hydrogen atom is substituted with a halogen atom. Represents an optionally substituted alkyl group having 1 to 4 carbon atoms.)

(2) A power storage device including a positive electrode, a negative electrode, and a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, wherein the nonaqueous electrolytic solution is the nonaqueous electrolytic solution according to (1) above. An electricity storage device characterized by the above.

According to the present invention, there is provided a non-aqueous electrolyte solution for an electricity storage device capable of improving the electrochemical characteristics of the electricity storage device in a wide temperature range, particularly the low-temperature discharge characteristic after high temperature storage, and an electricity storage device such as a lithium battery using the same. be able to.

[Non-aqueous electrolyte for electricity storage devices]
The non-aqueous electrolytic solution for an electricity storage device of the present invention (hereinafter, also simply referred to as “non-aqueous electrolytic solution”) is a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, and has the general formula (I). The compound represented by is contained in the nonaqueous electrolytic solution in an amount of 0.01 to 10% by mass.

The reason why the nonaqueous electrolytic solution of the present invention can greatly improve the electrochemical characteristics of the electricity storage device in a wide temperature range is not clear, but it is considered as follows.
The compound used in the present invention is a compound selected from sulfate ester and sulfite ester containing a cyclopentane structure, as described in the general formula (I). The cyclopentane ring (5-membered ring) has a larger strain energy than the cyclohexane ring (6-membered ring). Therefore, the sulfuric ester or sulfite ester containing the cyclopentane structure represented by the general formula (I) is a sulfuric ester or sulfite ester containing a cyclohexane (six-membered ring) structure. , 2-Benzodioxathiol 2,2-dioxide and 1,2-cyclohexanediol are more susceptible to electrochemical decomposition than cyclic sulfite and form a dense and highly heat-resistant coating on the positive electrode and the negative electrode. Similarly, it is more susceptible to electrochemical decomposition than the ethylene glycol sulfate ester described in Patent Document 1, which is a sulfate ester containing no cycloalkane structure, and forms a dense and highly heat-resistant coating film on the positive electrode and the negative electrode. .. Therefore, the non-aqueous electrolyte solution of the present invention can improve the electrochemical characteristics in a wide temperature range such as low-temperature discharge characteristics after high-temperature storage, as compared with the non-aqueous electrolyte solutions of Patent Documents 1 and 2. Conceivable.
Further, even if a compound having a cyclopentane structure similar to the compound according to the present invention, such as 1,2-cyclopentanediol cyclic carbonate described in Patent Document 3, a functional compound such as a sulfuric acid ester or a sulfurous acid ester is used. In the case of a carbonic acid ester having a >C=O group instead of a group (>S(=O) ₂ group or >S=O group), the properties of the formed film are significantly different, and therefore, the low temperature after storage at high temperature It is not possible to improve the electrochemical characteristics in a wide temperature range such as discharge characteristics.

The compound selected from the sulfate ester and the sulfite ester contained in the non-aqueous electrolyte solution of the present invention is represented by the following general formula (I).

（式中、ＸはＳ（＝Ｏ）_２基又はＳ＝Ｏ基を示し、Ｒ^１〜Ｒ^８は、それぞれ独立して水素原子、ハロゲン原子、又は水素原子の一部がハロゲン原子で置換されていてもよい炭素数１〜４のアルキル基を示す。）

(In the formula, X represents an S(═O) ₂ group or an S═O group, and R ^{1 to} R ⁸ are each independently a hydrogen atom, a halogen atom, or a part of the hydrogen atom is substituted with a halogen atom. Represents an optionally substituted alkyl group having 1 to 4 carbon atoms.)

In the general formula (I), R ^{1 to} R ⁸ each independently have a hydrogen atom, a halogen atom such as a fluorine atom, or a carbon atom number 1 to which a part of the hydrogen atom may be substituted with a halogen atom. 3, preferably an alkyl group having 1 or 2 carbon atoms, more preferably a hydrogen atom or a fluorine atom, still more preferably a hydrogen atom.
1-3 are preferable, as for the number of the substituents of the alkyl group which may replace a halogen atom or a part of hydrogen atom with the halogen atom, 1 or 2 is preferable, and 1 is more preferable.
The substitution position of the halogen atom or the alkyl group in which a part of the hydrogen atom may be substituted with a halogen atom is the position 4 position as viewed from X (S(=O) ₂ group or S=O group), that is, R ² Alternatively, it is preferably at the position of R ³ , or R ⁶ or R ⁷ .

When R ^{1 to} R ⁸ are alkyl groups in which a part of hydrogen atoms may be substituted with halogen atoms, specific examples thereof include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Linear alkyl group; branched-chain alkyl group such as isopropyl group, sec-butyl group, and tert-butyl group; fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2-chloroethyl group, 2-fluoro group Ethyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, 3-fluoropropyl group, 3-chloropropyl group, 3,3-difluoropropyl group, 3,3,3-trifluoro group Alkyl groups in which a part of hydrogen atoms are substituted with halogen atoms, such as propyl group, 2,2,3,3-tetrafluoropropyl group, and 2,2,3,3,3-pentafluoropropyl group, are suitable. Can be mentioned. Among these, a methyl group, an ethyl group, an n-propyl group, a trifluoromethyl group, or a 2,2,2-trifluoroethyl group is preferable, a methyl group, an ethyl group, or a trifluoromethyl group is more preferable, and a methyl group. More preferred are groups or ethyl groups.

The sulfate ester or sulfite ester containing a cyclopentane structure represented by the general formula (I) includes a cis type compound represented by the following general formula (II) and a trans type compound represented by the following general formula (III). Include.

（式中、Ｘ及びＲ^１〜Ｒ^８は、一般式（I）と同義である。）

(In formula, X and R< ¹ >-R< ⁸ > are synonymous with General formula (I).)

The compound represented by the general formula (I) may be a mixture of the cis type compound represented by the general formula (II) and the trans type compound represented by the general formula (III). The cis type compound/trans type compound (mass ratio) is preferably 50/50 to 100/0, more preferably 60/40 to 100/0, further preferably 70/30 to 100/0, further preferably 80/. 20 to 100/0, more preferably 90/10 to 100/0, and particularly preferably the case of only the cis-type compound.

Specific preferred examples of the sulfuric acid ester represented by the general formula (I) include compounds 1 to 22 below.

Specific preferred examples of the sulfite ester represented by the general formula (I) include compounds 23 to 44 below.

Among the above preferred examples, tetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2,2-dioxide (Compound 1) and 4-fluorotetrahydro-4H-cyclopenta[d][ are preferred. 1,3,2]dioxathiol-2,2-dioxide (Compound 3), 4-methyltetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2,2-dioxide (Compound 8) ), tetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2-oxide (Compound 23), 4-fluorotetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol 2-oxide (compound 25) and 4-methyltetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2-oxide (compound 30) are one or more selected from.
More preferably, tetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2,2-dioxide (Compound 1), 4-fluorotetrahydro-4H-cyclopenta[d][1,3,2]. ] One kind or two or more kinds selected from dioxathiol-2,2-dioxide (Compound 3) and tetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2-oxide (Compound 23) And particularly preferably tetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2,2-dioxide (Compound 1).

In the non-aqueous electrolyte solution of the present invention, the total content of the compounds represented by the general formula (I) (sulfate ester and sulfite ester) contained in the non-aqueous electrolyte solution is 0.01 in the non-aqueous electrolyte solution. 10 to 10% by mass. When the content is 10% by mass or less, there is little fear that the coating film is excessively formed on the electrode and the low temperature characteristics are deteriorated. When the content is 0.01% by mass or more, the coating film is sufficiently formed and the temperature is wide. The range is preferable because the effect of improving the electrochemical characteristics is enhanced in the range. The content is more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more in the non-aqueous electrolytic solution. The upper limit is preferably 5% by mass or less, more preferably 3% by mass or less.

In the non-aqueous electrolytic solution of the present invention, the compound represented by the general formula (I) is combined with a non-aqueous solvent, an electrolyte salt, and other additives described below to obtain electrochemical characteristics in a wide temperature range. It produces a unique effect of synergistic improvement.

(Non-aqueous solvent)
As the non-aqueous solvent used in the non-aqueous electrolytic solution of the present invention, one or more selected from cyclic carbonates, chain esters, lactones, ethers and amides can be preferably mentioned. In order to synergistically improve electrochemical properties in a wide temperature range, it is preferable that a chain ester is contained, it is more preferable that a chain carbonate is contained, and it is further preferable that both a cyclic carbonate and a chain ester are contained. It is particularly preferable to include both cyclic carbonate and chain carbonate.
The term “chain ester” is used as a concept including chain carbonate and chain carboxylic acid ester.

Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), trans or Cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter, both are collectively referred to as "DFEC"), vinylene carbonate (VC), vinylethylene carbonate (VEC), and 4-ethynyl-1 , 3-dioxolan-2-one (EEC), or two or more of them may be selected. Ethylene carbonate (EC), propylene carbonate (PC), 4-fluoro-1,3-dioxolan-2-one (FEC). ), vinylene carbonate (VC), and 4-ethynyl-1,3-dioxolan-2-one (EEC), or two or more thereof are more preferable.

Further, it is preferable to use at least one kind of a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond, or a fluorine atom, since the electrochemical characteristics under a high temperature environment are further improved. It is more preferable to include both a cyclic carbonate having an unsaturated bond such as a -carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom. The cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is more preferably VC, VEC or EEC, and the cyclic carbonate having a fluorine atom is further preferably FEC or DFEC.

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, and more preferably 0. It is 2% by volume 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, further preferably 2.5% by volume or less. When the content is in the above range, the electrochemical characteristics in a wider temperature range can be increased without impairing the Li ion permeability, which is preferable.

The content of the cyclic carbonate having a fluorine atom is preferably 0.07% by volume or more, more preferably 0.7% by volume or more, further preferably 4% by volume or more, most preferably the total volume of the non-aqueous solvent. It is 6% by volume or more, and the upper limit thereof is preferably 35% by volume or less, more preferably 25% by volume or less, and further 15% by volume or less. When the content is in the above range, the electrochemical characteristics in a wider temperature range can be improved without impairing the Li ion permeability, which is preferable.

When the non-aqueous solvent contains both the cyclic carbonate having an unsaturated bond and the cyclic carbonate having a fluorine atom, the content of the cyclic carbonate having an unsaturated bond with respect to the content of the cyclic carbonate having a fluorine atom is preferably 0.2% by volume or more, more preferably 3% by volume or more, further preferably 7% by volume or more, and the upper limit is preferably 40% by volume or less, more preferably 30% by volume or less, further 15% by volume or less. is there. When the content is within the above range, the electrochemical characteristics in a wider temperature range can be improved without impairing the Li ion permeability, which is particularly preferable.

In addition, it is preferable that the non-aqueous solvent contains both the cyclic carbonate having an unsaturated bond, because the electrochemical characteristics of the coating formed on the electrode in a wide temperature range can be improved, and the ethylene carbonate and the unsaturated carbonate are preferable. The content of the cyclic carbonate having a bond is preferably 3% by volume or more, more preferably 5% by volume or more, further preferably 7% by volume or more with respect to the total volume of the non-aqueous solvent, and the upper limit thereof is It is preferably 45% by volume or less, more preferably 35% by volume or less, and further preferably 25% by volume or less.

These solvents may be used in one kind, and when two or more kinds are used in combination, it is preferable because the effect of improving the electrochemical characteristics in a high temperature environment is further improved, and three or more kinds are used in combination. Is particularly preferable.
Suitable combinations of these cyclic carbonates include EC and PC, EC and VC, PC and VC, VC and FEC, EC and FEC, PC and FEC, FEC and DFEC, EC and DFEC, PC and DFEC, VC and DFEC. , VEC and DFEC, VC and EEC, EC and EEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and VEC, EC and VC and EEC, EC and EEC and FEC, PC And VC and FEC, EC and VC and DFEC, PC and VC and DFEC, EC and PC and VC and FEC, or EC and PC and VC and DFEC are preferable. Of the above combinations, EC and VC, EC and FEC, PC and FEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and EEC, EC and EEC and FEC, PC and A combination of VC and FEC, or EC, PC, VC and FEC and the like is more preferable.

As the chain ester, one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate; dimethyl One or more kinds of symmetrical chain carbonates selected from carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate; pivalate esters such as methyl pivalate, ethyl pivalate, propyl pivalate, and propione Preferable examples thereof include one or more chain carboxylic acid esters selected from methyl acidate, ethyl propionate (EP), propyl propionate, methyl acetate, and ethyl acetate (EA).
Among the chain esters, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, methyl propionate, methyl acetate and ethyl acetate (EA). A chain ester having a methyl group selected from is preferable, and a chain carbonate having a methyl group is particularly preferable.
Moreover, when using chain carbonate, it is preferable to use 2 or more types. Further, it is more preferable that both the symmetric chain carbonate and the asymmetric chain carbonate are contained, and it is further preferable that the symmetric chain carbonate is contained more than the asymmetric chain carbonate.

The content of the chain ester is not particularly limited, but it is preferably used in the range of 60 to 90% by volume with respect to the total volume of the non-aqueous solvent. If the content is 60% by volume or more, the viscosity of the non-aqueous electrolyte does not become too high, and if it is 90% by volume or less, the electrical conductivity of the non-aqueous electrolyte is lowered, and the electrochemistry in a wide temperature range is achieved. The range is preferable because the property is less likely to deteriorate.

The volume ratio of the symmetric chain carbonate in the chain carbonate is preferably 51% by volume or more, more preferably 55% by volume or more. The upper limit is more preferably 95% by volume or less, further preferably 85% by volume or less. It is particularly preferable that the symmetrical chain carbonate contains dimethyl carbonate (DMC). Further, the asymmetric chain carbonate more preferably has a methyl group, and methyl ethyl carbonate (MEC) is particularly preferable. The above case is preferable because the electrochemical characteristics in a wider temperature range are improved.

The ratio of the cyclic carbonate and the chain ester is preferably 10/90 to 45/55, and 15/85 to 40/60 in terms of the cyclic carbonate/chain ester (volume ratio), from the viewpoint of improving the electrochemical characteristics at high temperature. Is more preferable, and 20/80 to 35/65 is particularly preferable.

In the present invention, other non-aqueous solvent may be added in addition to the above non-aqueous solvent. Other non-aqueous solvents include tetrahydrofuran, 2-methyltetrahydrofuran, cyclic ethers such as 1,4-dioxane, chains of 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane and the like. Preferable examples include one or more selected from amides such as ether ether, dimethylformamide and the like, sulfones such as sulfolane, and lactones such as γ-butyrolactone (GBL), γ-valerolactone and α-angelicalactone.
The content of the other non-aqueous solvent is usually 1% or more, preferably 2% or more, and usually 40% or less, preferably 30% or less, and more preferably 20% with respect to the total volume of the non-aqueous solvent. It is as follows.

The above-mentioned non-aqueous solvents are usually used in admixture in order to achieve appropriate physical properties. Examples of the combination include a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain ester (particularly a chain carbonate) and a lactone, a combination of a cyclic carbonate and a chain. Suitable examples include a combination of a linear ester (particularly a chain carbonate) and an ether, a combination of a cyclic carbonate, a chain carbonate and a chain carboxylic acid ester, and a combination of a cyclic carbonate, a chain ester and a lactone is more preferable. Of the lactones, it is more preferable to use γ-butyrolactone (GBL).

Other additives may be further added to the non-aqueous electrolyte for the purpose of improving the electrochemical characteristics in a wider temperature range.
Specific examples of the other additives include the following compounds (A) to (I).

(A) One or more nitriles selected from acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and sebaconitrile.
(B) Cyclohexylbenzene, fluorocyclohexylbenzene compound (1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene, 1 An aromatic compound having a branched alkyl group such as -fluoro-4-tert-butylbenzene, biphenyl, terphenyl (o-, m-, p-form), diphenyl ether, fluorobenzene, difluorobenzene (o-, m) -, p-form), anisole, 2,4-difluoroanisole, partially hydrogenated terphenyl (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl) and the like. Aromatic compounds.
(C) Methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate. One or more isocyanate compounds.

(D) 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-(methanesulfonyloxy)propionate 2- Propinyl, di(2-propynyl)oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, di(2-propynyl) glutarate, 2-butyne-1,4-diyl dimethanesulfonate, 2-butyne- One or two or more triple bond-containing compounds selected from 1,4-diyl diformate and 2,4-hexadiyne-1,6-diyl dimethanesulfonate.
(E) 1,3-propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propene sultone, 2,2-dioxide-1,2-oxathiolan-4-yl Acetate or sultone such as 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, ethylene sulfite, hexahydrobenzo[1,3,2]dioxathiolane-2-oxide(1,2) -Cyclohexanediol cyclic sulfite), or cyclic sulfite such as 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, butane-2,3-diyl dimethanesulfonate, butane Sulfonate such as -1,4-diyl dimethane sulfonate or methylene methane disulfonate, vinyl sulfone compound such as divinyl sulfone, 1,2-bis(vinylsulfonyl)ethane or bis(2-vinylsulfonylethyl)ether One or two or more cyclic or chain-like S═O group-containing compounds selected from the group consisting of:
(F) Cyclic acetal compounds such as 1,3-dioxolane, 1,3-dioxane and 1,3,5-trioxane.

(G) Trimethyl phosphate, tributyl phosphate, and trioctyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl)methyl phosphate, bis phosphate (2,2,2-trifluoroethyl)ethyl, bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2 phosphate 2,3,3-tetrafluoropropyl, bis(2,2-difluoroethyl)phosphate 2,2,2-trifluoroethyl, bis(2,2,3,3-tetrafluoropropyl)phosphate 2,2 ,2-trifluoroethyl and (2,2,2-trifluoroethyl)phosphate (2,2,3,3-tetrafluoropropyl)methyl phosphate, tris(1,1,1,3,3,3)phosphate -Hexafluoropropan-2-yl), methyl methylenebisphosphonate, ethyl methylenebisphosphonate, methyl ethylenebisphosphonate, ethyl ethylenebisphosphonate, methyl butylenebisphosphonate, ethyl butylenebisphosphonate, methyl 2-(dimethylphosphoryl)acetate, ethyl 2-(Dimethylphosphoryl)acetate, methyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl 2-(diethylphosphoryl)acetate, methyl 2 -(Dimethoxyphosphoryl)acetate, ethyl 2-(dimethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate, 2-propynyl 2-(dimethoxyphosphoryl)acetate, 2-propynyl 2-(diethoxyphosphoryl)acetate, and one or more phosphorus-containing compounds selected from methyl pyrophosphate and ethyl pyrophosphate.
(H) Chain-like carboxylic acid anhydrides such as acetic anhydride and propionic anhydride, succinic anhydride, maleic anhydride, 3-allyl succinic anhydride, glutaric anhydride, itaconic anhydride, or 3-sulfo-propionic anhydride Acid anhydrides such as compounds.
(I) A cyclic phosphazene compound such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, or ethoxyheptafluorocyclotetraphosphazene.

Among the above, it is preferable to include at least one selected from the group consisting of (A) nitrile, (B) aromatic compound, and (C) isocyanate compound, since the electrochemical characteristics in a wider temperature range are improved.

Among the (A) nitriles, one or more selected from succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile are more preferable.
(B) Among the aromatic compounds, one or more selected from biphenyl, terphenyl (o-, m-, p-form), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene. Is more preferable, and one or more selected from biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are particularly preferable.
Among the (C) isocyanate compounds, one or more selected from hexamethylene diisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate are more preferable.

The content of each of the compounds (A) to (C) is preferably 0.01 to 7 mass% in the non-aqueous electrolyte. In this range, the film is sufficiently formed without becoming too thick, and the electrochemical characteristics in a wider temperature range are improved. The content is more preferably 0.05% by mass or more, further preferably 0.1% by mass or more in the non-aqueous electrolytic solution, and the upper limit thereof is more preferably 5% by mass or less and further preferably 3% by mass or less. ..

Further, (D) triple bond-containing compound, (E) sultone, cyclic sulfite, sulfonic acid ester, vinyl sulfone-containing cyclic or chain-like S═O group-containing compound, (F) cyclic acetal compound, (G) It is preferable to include the phosphorus-containing compound, (H) cyclic acid anhydride, and (I) cyclic phosphazene compound because the electrochemical characteristics in a wider temperature range are improved.
Examples of the compound (D) having a triple bond include 2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl 2-(methanesulfonyloxy)propionate, and dipropynyl. One or more selected from (2-propynyl)oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, and 2-butyne-1,4-diyl dimethanesulfonate are preferable, and 2-propynyl methanesulfonate is used. One or more selected from 2-propynyl vinyl sulfonate, 2-propynyl 2-(methanesulfonyloxy)propionate, di(2-propynyl)oxalate, and 2-butyne-1,4-diyl dimethanesulfonate. More preferable.
(E) A cyclic or chain S═O group-containing compound selected from sultone, cyclic sulfite, sulfonate, and vinyl sulfone (provided that the compound represented by the general formula (I) is a triple bond-containing compound. It is preferable to use the compound (1) is not included).

Examples of the cyclic S=O group-containing compound include 1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, 2,4-butane sultone, 1,3-propene sultone and 2,2-dioxide-. 1,2-oxathiolan-4-yl acetate, 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, methylene methane disulfonate, ethylene sulfite, ethylene sulfate, and 4-(methylsulfonyl) One or more kinds selected from methyl)-1,3,2-dioxathiolane 2-oxide are preferable.
Examples of the chain S=O group-containing compound include butane-2,3-diyl dimethanesulfonate, butane-1,4-diyl dimethanesulfonate, dimethyl methane disulfonate, pentafluorophenyl methane sulfonate, divinyl sulfone, And one or more selected from bis(2-vinylsulfonylethyl)ether are preferred.
Among the cyclic or chain-like S═O group-containing compounds, 1,3-propane sultone, 1,4-butane sultone, 2,4-butane sultone, 2,2-dioxide-1,2-oxathiolan-4-yl acetate. More preferably, one or more selected from ethylene sulphate, pentafluorophenyl methane sulphonate and divinyl sulphone.

As the cyclic acetal compound (F), 1,3-dioxolane or 1,3-dioxane is preferable, and 1,3-dioxane is more preferable.
Examples of the phosphorus-containing compound (G) include tris(2,2,2-trifluoroethyl)phosphate, tris(1,1,1,3,3,3-hexafluoropropan-2-yl)phosphate, and methyl. 2-(dimethylphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate, methyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl 2 -(Diethylphosphoryl)acetate, methyl 2-(dimethoxyphosphoryl)acetate, ethyl 2-(dimethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate, 2-propynyl 2- (Dimethoxyphosphoryl)acetate or 2-propynyl 2-(diethoxyphosphoryl)acetate is preferable, and tris(2,2,2-trifluoroethyl)phosphate, tris(1,1,1,3,3,3)phosphate is used. 3-hexafluoropropan-2-yl), ethyl 2-(diethylphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl). Acetate, 2-propynyl 2-(dimethoxyphosphoryl)acetate, or 2-propynyl 2-(diethoxyphosphoryl)acetate is more preferred.
As the cyclic acid anhydride (H), succinic anhydride, maleic anhydride, or 3-allylic succinic anhydride is preferable, and succinic anhydride or 3-allylic succinic anhydride is more preferable.
The cyclic phosphazene compound (I) is preferably a cyclic phosphazene compound such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, or phenoxypentafluorocyclotriphosphazene, and is preferably methoxypentafluorocyclotriphosphazene or ethoxypentafluorocyclophosphazene. More preferred is triphosphazene.

The content of each of the compounds (D) to (I) is preferably 0.001 to 5 mass% in the non-aqueous electrolyte. In this range, the film is sufficiently formed without becoming too thick, and the electrochemical characteristics in a wider temperature range are improved. The content is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more in the non-aqueous electrolytic solution, and the upper limit thereof is more preferably 3% by mass or less and further preferably 2% by mass or less. ..

Further, in order to improve the electrochemical characteristics in a wider temperature range, a lithium salt having an oxalic acid skeleton, a lithium salt having a phosphoric acid skeleton and a lithium salt having an S═O group are further added to the non-aqueous electrolyte. It is preferable to include one or more lithium salts selected from the above.
Specific examples of the lithium salt include lithium bis(oxalato)borate [LiBOB], lithium difluoro(oxalato)borate [LiDFOB], lithium tetrafluoro(oxalato)phosphate [LiTFOP], and lithium difluorobis(oxalato)phosphate [LiDFOP]. Lithium salt having at least one oxalic acid skeleton selected from, lithium salts having a phosphoric acid skeleton such as LiPO ₂ F ₂ and Li ₂ PO ₃ F, lithium trifluoro((methanesulfonyl)oxy)borate [LiTFMSB], lithium It is selected from pentafluoro((methanesulfonyl)oxy)phosphate [LiPFMSP], lithium methyl sulfate [LMS], lithium ethyl sulfate [LES], lithium 2,2,2-trifluoroethyl sulfate [LFES], and FSO ₃ Li. Suitable examples are lithium salts having one or more S=O groups. Among these, it is more preferable to contain a lithium salt selected from LiBOB, LiDFOB, LiTFOP, LiDFOP, LiPO ₂ F ₂ , LiTFMSB, LMS, LES, LFES, and FSO ₃ Li.

The ratio of the lithium salt in the non-aqueous solvent is preferably 0.001M or more and 0.5M 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, still more preferably 0.04 M or more. The upper limit is preferably 0.4 M or less, more preferably 0.2 M or less. (However, M shows mol/L.)

(Electrolyte salt)
Suitable examples of the electrolyte salt used in the present invention include the following lithium salts.
Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , and LiN(SO ₂ F) ₂ [LiFSI], LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , _{LiCF 3 SO 3, LiC (SO} 2 CF 3) 3, LiPF 4 (CF 3) 2, LiPF 3 (C 2 F 5) 3, LiPF 3 (CF 3) 3, LiPF 3 (iso-C 3 F 7) ₃ , LiPF ₅ (iso-C ₃ F ₇ ) and other lithium salts containing a chain alkyl fluoride group, (CF ₂ ) ₂ (SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ NLi. Suitable examples include at least one lithium salt selected from lithium salts having a cyclic fluorinated alkylene chain and the like, and one kind or a mixture of two or more kinds thereof can be used.
Among these, one or two or more selected from LiPF ₆ , LiBF ₄ , LiN(SO ₂ F) ₂ [LiFSI], LiN(SO ₂ CF ₃ ) ₂ and LiN(SO ₂ C ₂ F ₅ ) ₂ are used. Most preferably, LiPF ₆ is used.

The concentration of the electrolyte salt is usually preferably 0.3 M or more, more preferably 0.7 M or more, still more preferably 1.1 M or more, with respect to the non-aqueous solvent. The upper limit thereof is preferably 2.5 M or less, more preferably 2.0 M or less, still more preferably 1.6 M or less.
Further, as a preferable combination of these electrolyte salts, at least one lithium salt containing LiPF ₆ and further selected from LiBF ₄ , LiN(SO ₂ CF ₃ ) ₂ and LiN(SO ₂ F) ₂ [LiFSI] is included. Is preferably contained in the non-aqueous electrolyte.
When the proportion of the lithium salt other than LiPF _{6 in the} non-aqueous solvent is 0.001 M or more, the effect of improving the electrochemical characteristics in a wide temperature range is likely to be exhibited, and when it is 1.0 M or less, a wide temperature range is obtained. It is preferable because there is little concern that the effect of improving the electrochemical characteristics in step 1 will be reduced. It is preferably 0.01 M or more, more preferably 0.03 M or more, still more preferably 0.04 M or more. The upper limit is preferably 0.8 M or less, more preferably 0.6 M or less, and further preferably 0.4 M or less.

[Production of non-aqueous electrolyte]
The non-aqueous electrolytic solution of the present invention is, for example, a compound containing a cyclopentane structure represented by the general formula (I) in which the above-mentioned non-aqueous solvent is mixed and the electrolyte salt and the non-aqueous electrolytic solution are mixed with the non-aqueous solvent. Can be obtained by adding.
At this time, the non-aqueous solvent and the compound represented by the general formula (I) to be added to the non-aqueous electrolytic solution to be used may be those which are purified in advance and used as few impurities as possible within a range not significantly reducing the productivity. preferable.

The non-aqueous electrolyte solution of the present invention can be used in the following first to fourth power storage devices, and as the non-aqueous electrolyte, not only liquid ones but also gelled ones can be used. Furthermore, the non-aqueous electrolytic solution of the present invention can also be used for solid polymer electrolytes. Above all, it is preferably used for the first electricity storage device (that is, for lithium batteries) or the fourth electricity storage device (that is, for lithium ion capacitors) that uses a lithium salt as an electrolyte salt, and for lithium batteries. More preferably, it is more preferably used for a lithium secondary battery.

[First power storage device (lithium battery)]
The lithium battery which is the first power storage device is a generic term for a lithium primary battery and a lithium secondary battery, and the lithium secondary battery is used as a concept including a so-called lithium ion secondary battery.
The lithium battery of the present invention comprises a positive electrode, a negative electrode, and the non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent. Components other than the non-aqueous electrolyte solution such as the positive electrode and the negative electrode can be used without particular limitation.
For example, as the positive electrode active material for a lithium secondary battery, a composite metal oxide with lithium containing one or more selected from the group consisting of cobalt, manganese, and nickel is used. These positive electrode active materials can be used alone or in combination of two or more.
Examples of such a lithium mixed metal oxide include LiCoO ₂ , LiCo _1-x M _x O ₂ (where M is Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and One or more elements selected from Cu, 0.001≦x≦0.05), LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01<x<1), LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O ₂ , LiNi _0.8 Mn _{0 .1} Co _0.1 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , Li ₂ MnO ₃ and LiMO ₂ (M is a transition metal such as Co, Ni, Mn, or Fe) as a solid solution , And one or more selected from LiNi _1/2 Mn _3/2 O ₄ are more preferable. Moreover, LiCoO ₂ and LiMn ₂ O _4, LiCoO ₂ and LiNiO _2, may be used in combination as LiMn ₂ O ₄ and LiNiO _2.

When a lithium mixed metal oxide that operates at a high charging voltage is used, generally, electrochemical characteristics are likely to deteriorate under a high temperature environment due to a reaction with an electrolyte during charging, but in the lithium secondary battery according to the present invention, It is possible to suppress deterioration of these electrochemical characteristics.
In particular, when a positive electrode active material containing Ni is used, generally, the catalytic action of Ni causes decomposition of the non-aqueous solvent on the surface of the positive electrode, which tends to increase the resistance of the battery. In particular, the electrochemical characteristics tend to deteriorate in a high temperature environment, but the lithium secondary battery according to the present invention is preferable because the deterioration of these electrochemical characteristics can be suppressed. Particularly, when the ratio of the atomic concentration of Ni to the atomic concentration of all the transition metal elements in the positive electrode active material exceeds 10 atomic %, the above effect becomes remarkable, so that it is preferable, and the positive electrode active material of 20 atomic% or more is used. It is more preferable to use a substance, and it is more preferable to use a positive electrode active material of 30 atomic% or more. Specifically, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O ₂ , Preferable examples include one or more selected from LiNi _0.8 Mn _0.1 Co _0.1 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

Further, lithium-containing olivine-type phosphate can be used as the positive electrode active material. In particular, a lithium-containing olivine-type phosphate containing one or more selected from iron, cobalt, nickel and manganese is preferable. Specific examples thereof include _one or more selected from LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO ₄ , and LiFe _1-x Mn _x PO ₄ (0.1<x<0.9).
Some of these lithium-containing olivine-type phosphates may be replaced with other elements, and some of iron, cobalt, nickel, and manganese are Co, Mn, Ni, Mg, Al, B, Ti, V, Nb. , Cu, Zn, Mo, Ca, Sr, W, and Zr may be substituted with one or more elements selected from the group, or may be coated with a compound or carbon material containing these other elements. Of these, LiFePO ₄ or LiMnPO ₄ is preferable.
Further, the lithium-containing olivine-type phosphate can be used by mixing with the above-mentioned positive electrode active material, for example.
The lithium-containing olivine-type phosphate forms a stable phosphoric acid skeleton (PO ₄ ) structure and is excellent in thermal stability during charging, and therefore can improve electrochemical characteristics in a wide temperature range.

As the positive electrode for lithium primary _{battery, CuO, Cu 2 O, Ag} 2 O, Ag 2 CrO 4, CuS, CuSO 4, TiO 2, TiS 2, SiO 2, SnO, V 2 O 5, V 6 O 12 _{, VO x, Nb 2 O 5} , Bi 2 O 3, Bi 2 Pb 2 O 5, Sb 2 O 3, CrO 3, Cr 2 O 3, MoO 3, WO 3, SeO 2, MnO 2, Mn 2 O 3 , Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , Ni ₂ O ₃ , NiO, CoO ₃ , CoO, etc., oxides of one or more metal elements or chalcogen compounds, sulfur such as SO ₂ , SOCl ₂ Examples thereof include compounds and fluorocarbon (fluorinated graphite) represented by the general formula (CF _x ) _n . Among these, MnO ₂ , V ₂ O ₅ , fluorinated graphite and the like are preferable.

The conductive agent of the positive electrode is not particularly limited as long as it is an electron conductive material that does not chemically 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, more preferably 2 to 5% by mass.

The positive electrode is a positive electrode active material containing a conductive agent such as acetylene black or carbon black, and polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), or acrylonitrile and butadiene. Positive electrode mixture by mixing with a binder such as copolymer (NBR), carboxymethyl cellulose (CMC), ethylene propylene diene terpolymer, and then adding a high boiling point solvent such as 1-methyl-2-pyrrolidone to the mixture and kneading Then, this positive electrode mixture is applied to an aluminum foil or a stainless lath plate of a current collector, dried and pressure-molded, and then under a vacuum at a temperature of about 50° C. to 250° C. for about 2 hours. It can be produced by heat treatment.
The density of the part of the positive electrode excluding the current collector is usually 1.5 g/cm ³ or more, and in order to further increase the capacity of the battery, preferably 2 g/cm ³ or more, more preferably 3 g/cm ³ or more, More preferably, it is 3.6 g/cm ³ or more. The upper limit is preferably 4 g/cm ³ or less.

As a negative electrode active material for a lithium secondary battery, a lithium metal, a lithium alloy, a carbon material capable of inserting and extracting lithium [graphitizable carbon or a (002) plane spacing of 0.37 nm or more is difficult. Graphitized carbon, graphite having a (002) plane spacing of 0.34 nm or less, etc.], tin (unit), tin compound, silicon (unit), silicon compound, lithium titanate compound such as Li ₄ Ti ₅ O ₁₂ And one or more selected from the above.
Among these, it is more preferable to use a highly crystalline carbon material such as artificial graphite or natural graphite in terms of lithium ion storage and release capacity, and the lattice spacing (d ₀₀₂ ) of the lattice plane ( ₀₀₂ ) is 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.
In particular, artificial graphite particles having a lumpy structure in which a plurality of flat graphite particles are aggregated or combined in a non-parallel manner, and mechanical properties such as compressive force, frictional force, and shearing force are repeatedly applied to form scaly natural graphite into a spherical shape. It is preferable to use particles which have been subjected to chemical treatment.

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 was press-molded to a density of 1.5 g/cm ³ or more. ) And the peak intensity I(004) of the (004) plane, I(110)/I(004), is preferably 0.01 or more because the electrochemical characteristics in a wider temperature range improve. More preferably, it is more preferably 0.1 or more. In addition, 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 the upper limit is 0.5. It is more preferably 3 or less.
Further, it is preferable that the highly crystalline carbon material (core material) is coated with a less crystalline carbon material than the core material because the electrochemical characteristics in a wide temperature range are further improved. The crystallinity of the coating carbon material can be confirmed by TEM.
When a highly crystalline carbon material is used, it tends to react with the non-aqueous electrolytic solution during charging and decrease the electrochemical characteristics at low temperature or high temperature due to an increase in interfacial resistance, but in the lithium secondary battery according to the present invention, The electrochemical characteristics are improved in a wide temperature range.

Further, examples of the metal compound capable of inserting and extracting lithium as the negative electrode active material include Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu. Examples thereof include compounds containing at least one metal element such as Zn, Ag, Mg, Sr, or Ba. These metal compounds may be used in any form such as a simple substance, an alloy, an oxide, a nitride, a sulfide, a boride, and an alloy with lithium, but any of a simple substance, an alloy, an oxide and an alloy with lithium. Is preferable because it can increase the capacity. Among these, those containing at least one element selected from Si, Ge and Sn are preferable, and those containing at least one element selected from Si and Sn are particularly preferable because they can increase the capacity of the battery.

The negative electrode is kneaded using the same conductive agent, binder, and high boiling point solvent as in the preparation of the above positive electrode to form a negative electrode mixture, and then the negative electrode mixture is applied to a copper foil or the like of a current collector. After drying, pressure molding, and heat treatment under vacuum at a temperature of about 50° C. to 250° C. for about 2 hours, it can be produced.
The density of the portion of the negative electrode excluding the current collector is usually 1.1 g/cm ³ or more, and in order to further increase the capacity of the battery, it is preferably 1.5 g/cm ³ or more, more preferably 1.7 g. /Cm ³ or more. The upper limit is preferably 2 g/cm ³ or less.

Further, examples of the negative electrode active material for a lithium primary battery include lithium metal or lithium alloy.

The structure of the lithium battery is not particularly limited, and a coin battery, a cylindrical battery, a prismatic battery, a laminated battery having a single-layer or multi-layer separator can be applied.
The battery separator is not particularly limited, but a single-layer or laminated microporous film of polyolefin such as polypropylene, polyethylene, and ethylene-propylene copolymer, woven fabric, and non-woven fabric can be used.
As the polyolefin laminate, a laminate of polyethylene and polypropylene is preferable, and a three-layer structure of polypropylene/polyethylene/polypropylene is more preferable.
The thickness of the separator is preferably 2 μm or more, more preferably 3 μm or more, still more preferably 4 μm or more, and its upper limit is 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less.

The lithium secondary battery according to the present invention has excellent electrochemical characteristics in a wide temperature range even when the end-of-charge voltage is 4.2 V or higher, particularly 4.3 V or higher, and the characteristics are good even at 4.4 V or higher. is there. The discharge end voltage can be usually 2.8 V or higher, and 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 it is usually used in the range of 0.1 to 30C. The lithium battery of the present invention can be charged and discharged at -40 to 100°C, preferably -10 to 80°C.

In the present invention, as a measure for increasing the internal pressure of the lithium battery, a method of providing a safety valve on the battery lid or making a notch in a member such as a battery can or a gasket can be adopted. Further, as a safety measure for preventing overcharge, a current cutoff mechanism that detects the internal pressure of the battery and cuts off the current can be provided on the battery lid.

[Second power storage device (electric double layer capacitor)]
A second electricity storage device of the present invention is an electricity storage device which contains the non-aqueous electrolytic solution of the present invention and stores energy by utilizing the electric double layer capacity of the electrolytic solution and an electrode interface. One example of the present invention is an electric double layer capacitor. The most typical electrode active material used in this electricity storage device is activated carbon. Double-layer capacity generally increases with surface area.

[Third electricity storage device]
A third electricity storage device of the present invention is an electricity storage device that contains the non-aqueous electrolyte solution of the present invention and stores energy by utilizing an electrode doping/dedoping reaction. Examples of the electrode active material used in this electricity storage device include metal oxides such as ruthenium oxide, iridium oxide, tungsten oxide, molybdenum oxide, and copper oxide, and π-conjugated polymers such as polyacene and polythiophene derivatives. Capacitors using these electrode active materials can store energy associated with electrode doping/dedoping reactions.

[Fourth power storage device (lithium ion capacitor)]
A fourth electricity storage device of the present invention is an electricity storage device that contains the non-aqueous electrolyte solution of the present invention and stores energy by utilizing intercalation of lithium ions into a carbon material such as graphite serving as a negative electrode. 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 utilizing 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 .

Examples of the electrolytic solution using the compound of the present invention will be shown below, but the present invention is not limited to these examples.

Examples 1 to 16 and Comparative Examples 1 to 4
[Fabrication of lithium-ion secondary battery]
_{LiNi 0.6 Mn 0.2 Co 0.2 O 2} 93 % by weight, acetylene black (conductive agent) 4% by weight were mixed, pre-polyvinylidene fluoride (binder) 3 wt% 1-methyl-2- The solution mixed with pyrrolidone was added and mixed to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to one surface of an aluminum foil (current collector), dried, pressure-treated and cut into a predetermined size to prepare a positive electrode sheet. The density of the part of the positive electrode excluding the current collector was 3.6 g/cm ³ .
Further, 5% by mass of silicon (single substance), 85% by mass of artificial graphite (d ₀₀₂ =0.335 nm, negative electrode active material), and 5% by mass of acetylene black (conductive agent) were mixed, and polyvinylidene fluoride (binder) was mixed in advance. 5 mass% was added to and mixed with a solution in which 1-methyl-2-pyrrolidone had been dissolved to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one surface of a copper foil (current collector), dried, pressure-treated and cut into a predetermined size to prepare a negative electrode sheet. The density of the part 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) of the (110) plane of the graphite crystal to the peak intensity I(004) of the (004) plane [I(110)/I (004)] was 0.1.
Then, the positive electrode sheet, the microporous polyethylene film separator, and the negative electrode sheet were laminated in this order, and the nonaqueous electrolytic solution having the composition shown in Tables 1 and 2 was added thereto 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., a constant current and a constant voltage of 1 C were used to charge to a final voltage of 4.3 V for 3 hours, and the temperature of the constant temperature bath was lowered to −10° C. The battery was discharged to a final voltage of 2.7 V under a constant current of 1 C, and the initial discharge capacity of -10°C was obtained.
<High temperature charge storage test>
Next, this coin battery was charged in a constant temperature bath of 70° C. with a constant current and a constant voltage of 1 C to a final voltage of 4.3 V for 3 hours, and stored at 4.3 V for 10 days. Then, it was put in a constant temperature bath of 25° C. and once discharged to a final voltage of 2.7 V under a constant current of 1 C.
<Low temperature discharge capacity retention rate after high temperature charge storage>
After that, similarly to the initial measurement of the discharge capacity, the discharge capacity retention rate at −10° C. after high temperature charge storage was determined by the following formula.
-10°C discharge capacity retention rate after 70°C charge storage (%) = (-10°C discharge capacity after 70°C charge storage/initial -10°C discharge capacity) x 100
The results are shown in Tables 1-2.
EP used in Example 8 in Table 1 is an abbreviation for ethyl propionate.

Examples 17-18 and Comparative Example 5
A negative electrode sheet was prepared by using lithium titanate Li ₄ Ti ₅ O ₁₂ (negative electrode active material) instead of the negative electrode active material used in Example 1. 85% by mass of lithium titanate and 10% by mass of acetylene black (conductive agent) were mixed, and 5% by mass of polyvinylidene fluoride (binder) was added to a solution prepared by dissolving in 1-methyl-2-pyrrolidone. The mixture was mixed to prepare a negative electrode mixture paste. This negative electrode material mixture paste was applied onto a copper foil (current collector), dried, pressure-treated and cut into a predetermined size to prepare a negative electrode sheet, and the end-of-charge voltage at the time of battery evaluation was 2 A laminated battery was prepared and battery evaluation was performed in the same manner as in Example 1 except that the discharge final voltage was 0.75 V, the discharge end voltage was 1.1 V, and the composition of the nonaqueous electrolytic solution was changed to a predetermined composition. The results are shown in Table 3.

In any of the lithium secondary batteries of Examples 1 to 16, Comparative Example 1 in which the sulfuric acid ester or sulfite ester represented by the general formula (I) was not added to the non-aqueous electrolyte solution of the present invention, ethylene glycol Comparative Example 2 when a sulfuric acid ester was added, Comparative Example 3 when hexahydro 1,3,2-benzodioxathiol 2,2-dioxide was added, and 1,2-cyclopentanediol cyclic carbonate were added. In this case, compared with the lithium secondary battery of Comparative Example 4, the electrochemical characteristics in a wide temperature range are remarkably improved. As described above, the effect of the present invention is a unique effect when the sulfuric acid ester or sulfite ester represented by the general formula (I) is contained in the non-aqueous electrolytic solution in which the electrolyte salt is dissolved in the non-aqueous solvent. It turned out to be.
Further, from the comparison between Examples 17 to 18 and Comparative Example 5, it is clear that the same effect is obtained when lithium titanate is used for the negative electrode, and therefore it is not an effect depending on a specific positive electrode or negative electrode. ..

Furthermore, the non-aqueous electrolyte of the present invention also has the effect of improving the discharge characteristics of a lithium primary battery in a wide temperature range.

By using the nonaqueous electrolytic solution for an electricity storage device of the present invention, an electricity storage device having excellent electrochemical characteristics in a wide temperature range can be obtained. Especially when used as a non-aqueous electrolyte for a storage battery device such as a lithium secondary battery mounted on a hybrid electric vehicle, a plug-in hybrid electric vehicle, a battery electric vehicle, etc. Can be obtained.

Claims (10)

A non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte solution contains 0.01 to 10% by mass of a compound represented by the following general formula (I). A non-aqueous electrolyte solution for an electricity storage device.

(In the formula, X represents an S(═O) ₂ group or an S═O group, and R ^{1 to} R ⁸ are each independently a hydrogen atom, a halogen atom, or a part of the hydrogen atom is substituted with a halogen atom. Represents an optionally substituted alkyl group having 1 to 4 carbon atoms.) R ^{1 to} R ⁸ in the general formula (I) are each independently a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 3 carbon atoms in which a part of the hydrogen atoms may be substituted with a fluorine atom. A non-aqueous electrolyte solution for an electricity storage device according to claim 1. The compound represented by the general formula (I) includes tetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2,2-dioxide and 4-fluorotetrahydro-4H-cyclopenta[d][1. ,3,2]Dioxathiol-2,2-dioxide, 4-methyltetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2,2-dioxide, tetrahydro-4H-cyclopenta[d ] [1,3,2]Dioxathiol-2-oxide, 4-fluorotetrahydro-4H-cyclopenta[d][1,3,2]dioxathiol-2-oxide, and 4-methyltetrahydro-4H- The nonaqueous electrolytic solution for an electricity storage device according to claim 1 or 2, which is one or more selected from cyclopenta[d][1,3,2]dioxathiol-2-oxide. The nonaqueous electrolytic solution for an electricity storage device according to claim 1, wherein the nonaqueous solvent contains a cyclic carbonate and a chain ester. The cyclic carbonate is one or more selected from ethylene carbonate, propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinylene carbonate, and 4-ethynyl-1,3-dioxolan-2-one. The non-aqueous electrolyte solution for an electricity storage device according to claim 4, which comprises. The nonaqueous electrolytic solution for an electricity storage device according to claim 4 or 5, wherein both the symmetric chain carbonate and the asymmetric chain carbonate are contained as the chain ester, and the symmetric chain carbonate is contained more than the asymmetric chain carbonate. An electricity storage device comprising a positive electrode, a negative electrode, and a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, wherein the nonaqueous electrolytic solution is the nonaqueous electrolytic solution according to any one of claims 1 to 6. An electricity storage device characterized by being. The negative electrode as a negative electrode active material, lithium metal, lithium alloys, carbon materials capable of inserting and extracting lithium, tin, tin compounds, silicon, silicon compounds, and one or more selected from lithium titanate compounds. The power storage device according to claim 7, which comprises: The positive electrode contains, as a positive electrode active material, a composite metal oxide with lithium containing one or more selected from cobalt, manganese, and nickel, or a lithium-containing olivine-type phosphate. Electricity storage device. The electricity storage device according to any one of claims 7 to 9, wherein the electricity storage device is a lithium secondary battery or a lithium ion capacitor.