JP2019207890A - Non-aqueous electrolyte and power storage device using the same - Google Patents

Abstract

To provide a non-aqueous electrolyte for a power storage device and a power storage device using the same, which can improve electrochemical characteristics in a wide temperature range, particularly at a high temperature, and further reduce the increase rate of the electrode thickness after a high temperature cycle.SOLUTION: There is provided a nonaqueous electrolyte for a power storage device includes a specific asymmetric halogenated phenyl carbonate compound, and the content of the halogenated phenyl carbonate compound is 0.001 to 5% by mass in a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, and there is provided a power storage device using the nonaqueous electrolyte.SELECTED DRAWING: None

Description

The present invention (first invention) relates to a non-aqueous electrolyte capable of improving electrochemical characteristics in a wide temperature range, particularly charge storage characteristics and low-temperature output characteristics after charge storage, and an electricity storage device using the same.
In addition, the present invention (second invention) relates to a nonaqueous electrolytic solution that can improve electrochemical characteristics in a wide temperature range, and in particular, can improve electrochemical characteristics at high temperatures, 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 laptop computers, electric vehicles, and power storage sources.

<Regarding the first invention>
In the case of a lithium secondary battery used in a place where the environment easily changes, such as an electric vehicle or power storage, the battery characteristics are likely to deteriorate particularly when used in a high temperature environment such as midsummer. Therefore, the demand for the charge storage characteristics under a high temperature environment is increasing, and further improvement of the battery characteristics is demanded.
Note that in this specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery.

The lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of inserting and extracting lithium, a non-aqueous electrolyte composed of a lithium salt and a non-aqueous solvent, and the non-aqueous solvent includes ethylene carbonate (EC), Carbonates such as propylene carbonate (PC) are used.
As negative electrodes of lithium secondary batteries, metal lithium, metal compounds that can occlude and release lithium (metal simple substance, metal oxide, alloys with lithium, etc.) and carbon materials are known, and in particular, lithium is occluded. Lithium secondary batteries using carbon materials such as coke, artificial graphite, and natural graphite that can be released 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 is such that the solvent in the non-aqueous electrolyte is oxidized and decomposed on the positive electrode surface during charging, and reduced on the negative electrode surface. Decomposition products and gas generated by decomposition inhibit the desired electrochemical reaction of the battery, resulting in degradation of electrochemical characteristics over a wide temperature range, and insertion and extraction of lithium into the positive and negative electrodes. Since it cannot be smoothly performed, the electrochemical characteristics are liable to deteriorate.
In addition, lithium secondary batteries using lithium metal, its alloys, simple metals such as tin or silicon, and oxides as negative electrode materials have a high initial capacity, but are becoming finer during use as power storage devices. It is known that reductive decomposition of a non-aqueous solvent occurs at an accelerated rate as compared with the negative electrode, and the electrochemical characteristics in a wide temperature range are greatly deteriorated. If these negative electrode materials are pulverized or a decomposition product of a nonaqueous solvent accumulates, lithium cannot be smoothly occluded and released, and the electrochemical characteristics in a wide temperature range are likely to deteriorate.

On the other hand, lithium secondary batteries using, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiFePO _4, etc. as positive electrode materials are non-aqueous at high temperatures. It is known that the non-aqueous solvent in the electrolyte is oxidatively decomposed in the charged state, and by-products generated at that time are deposited on the negative electrode, forming a film with high electrical resistance, resulting in a decrease in electrochemical properties. .

Patent Document 1 proposes a nonaqueous electrolytic solution containing 5% by mass or more of a biphenyl group-containing phosphate ester compound as a flame retardant. It can be provided. It is described that when the amount of the flame retardant added is less than 5% by mass, the polymerization reaction cannot be promoted and the effect of preventing overcharge of the secondary battery becomes insufficient.
Non-Patent Document 1 improves the cycle characteristics of a coin cell using an electrolytic solution to which 4-phenylphenyl diethyl phosphate is not added by using a positive electrode that has been previously oxidized with 4-phenylphenyl diethyl phosphate. It has been suggested.

<Regarding the second invention>
A battery mounted on an electronic device or an electric vehicle is likely to be used under a high temperature in midsummer or in an environment warmed by heat generated by the electronic device. In thin electronic devices such as tablet terminals and ultrabooks, laminated batteries and square batteries that use a laminated film such as an aluminum laminated film are often used as exterior members. However, these batteries are thin. There is a problem that it is likely to be deformed easily due to a slight expansion of the exterior member, and the influence of the deformation on the electronic device is very large.

A lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of occluding and releasing lithium, and a non-aqueous electrolyte composed of a lithium salt and a non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate (EC) and propylene. Carbonates such as carbonate (PC) are used.
As negative electrodes of lithium secondary batteries, lithium metal, metal compounds capable of inserting and extracting lithium ions (metal simple substance, metal oxide, alloy with lithium, etc.) and carbon materials are known. In particular, non-aqueous electrolyte secondary batteries using carbon materials that can occlude and release lithium, such as coke and graphite (artificial graphite, natural graphite), are widely used. Since the negative electrode material stores and releases lithium and electrons at an extremely low potential equivalent to that of lithium metal, many solvents have a possibility of undergoing reductive decomposition, particularly at high temperatures. Therefore, some of the solvent in the electrolyte solution is reductively decomposed on the negative electrode regardless of the type of the negative electrode material, and the migration of lithium ions is hindered by the deposition of decomposition products, gas generation, and electrode swelling, especially at high temperatures. There are problems such as deterioration of battery characteristics such as cycle characteristics below, and deformation of the battery due to electrode swelling.
Furthermore, lithium secondary batteries using a single metal or metal oxide such as lithium metal, alloys thereof, tin or silicon as a negative electrode material have a high initial capacity, but are finely pulverized during a cycle. Compared to the above, reductive decomposition of nonaqueous solvents occurs at an accelerated rate, and there are known problems such as battery performance and battery performance such as battery capacity and cycle characteristics being greatly reduced, and battery deformation due to electrode swelling. ing.

On the other hand, materials capable of occluding and releasing lithium, such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO ₄ used as positive electrode materials, store lithium ions and electrons at a noble voltage of 3.5 V or more based on lithium. And many solvents have the potential to undergo oxidative degradation, especially at high temperatures, for release. Therefore, regardless of the type of positive electrode material, a part of the solvent in the electrolyte solution is oxidatively decomposed on the positive electrode. There was a problem of deteriorating characteristics.

  In spite of the above situation, 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 has been increasing, and the density of the electrodes has been increased and the useless space in the battery has been reduced. The volume occupied by the nonaqueous electrolyte in the battery has been reduced. It has become. Therefore, the battery performance at high temperature is likely to be degraded by a slight decomposition of the non-aqueous electrolyte.

Patent Document 2 proposes a non-aqueous electrolyte containing an aromatic carbonate such as bis (4-phenoxyphenyl) carbonate, and a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte. It is described that safety is improved.
Patent Document 3 includes at least one compound selected from the group consisting of a cyclic carbonate having a C = C unsaturated bond, a cyclic carbonate having a fluorine atom, and a fluorophosphate, including methylphenyl carbonate and the like. Non-aqueous electrolyte (A) containing diphenyl carbonate and vinylene carbonate (C) enhances safety during overcharge and suppresses deterioration of battery performance during continuous charge Is described.

JP 2014-164801 A JP 2004-111169 A International Publication No. 2009/107786

Electrochimica Acta Volume 112 (2013), Pages 74-81

An object of the first invention is to provide a non-aqueous electrolyte capable of improving electrochemical characteristics in a wide temperature range, in particular, charge storage characteristics and low-temperature output characteristics after charge storage, and an electricity storage device using the same.
The second invention provides a non-aqueous electrolyte capable of improving electrochemical characteristics over a wide temperature range, particularly at high temperatures, and further reducing the rate of increase in electrode thickness after a high temperature cycle, and an electricity storage device using the same The task is to do.

<First invention>
The present inventors examined in detail about the performance of the nonaqueous electrolyte solution of the said patent document 1. FIG. As a result, the non-aqueous electrolyte of Patent Document 1 is sufficiently satisfactory for the problem of improving the electrochemical characteristics in a wide temperature range, particularly the charge storage characteristics and the low temperature output characteristics after charge storage. I couldn't say that.
Therefore, the present inventors have made extensive studies to solve the above problems, and in a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, a specific phosphate ester is specified in the non-aqueous electrolyte solution. By containing it in an amount, the resistance increase caused by the decomposition products of the non-aqueous electrolyte on the positive electrode and the negative electrode is remarkably suppressed, so that electrochemical characteristics in a wide temperature range, particularly charge storage characteristics and after charge storage The inventors found that the low-temperature output characteristics can be improved and completed the first invention.

<Second invention>
As a result of examining the performance of the non-aqueous electrolyte solution of Patent Document 2 in detail, the present inventors can improve the safety during overcharge to some extent in the non-aqueous electrolyte secondary battery of Patent Document 2. However, the problem of reducing the increase rate of the electrode thickness accompanying charging / discharging is not disclosed at all and is not satisfactory.
Patent Document 3 discloses nothing about the problem of reducing the increase rate of the electrode thickness accompanying charge / discharge, and is a partial hydrogen atom of a benzene ring of a compound group represented by methylphenyl carbonate. However, although it is suggested that it may be substituted with a halogen atom, there is no example. In addition, there is no description that some hydrogen atoms in the benzene ring of diphenyl carbonate may be substituted with halogen atoms.
Furthermore, although Patent Document 3 describes the improvement of safety of overcharge, the suppression of deterioration during continuous charging, and the ability to suppress the generation of gas to some extent, the problem of reducing the electrode thickness due to charging and discharging is described. Is not disclosed at all.
Therefore, as a result of intensive studies to solve the above problems, the present inventors have determined that a compound in which the hydrogen atom of one benzene ring of diphenyl carbonate is substituted with a specific number of halogen atoms is a non-aqueous electrolyte. It has been found that the rate of increase in the electrode thickness after the high-temperature cycle can be reduced by containing it in the inside, and the second invention has been completed.

That is, the present invention provides the following (1) to (4).
<First invention>
(1) In a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous electrolytic solution, the biphenyl compound containing a phosphate structure represented by the following general formula (I) is included, and the content of the biphenyl compound is: A non-aqueous electrolyte characterized by being 0.1 to 4.5 mass in the non-aqueous electrolyte.

(In General Formula (I), R ¹ and R ² are each independently an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 3 to 8 carbon atoms, or the number of carbon atoms. 6 to 20 aryl groups, each of the alkyl group, alkenyl group, alkynyl group or aryl group may have at least one hydrogen atom substituted with a halogen atom.
X ¹ and X ² each independently represent a halogen atom or a halogenated alkyl group having 1 to 6 carbon atoms, m is an integer of 0 to 4, and n is an integer of 0 to 5. )

  (2) In an electricity storage device including a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, the non-aqueous electrolyte is the non-aqueous electrolyte described in (1). A power storage device characterized.

<Second invention>
(3) In a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, the composition contains an asymmetric halogenated phenyl carbonate compound represented by the following general formula (II), and the content of the halogenated phenyl carbonate compound is: A non-aqueous electrolyte characterized by being 0.001 to 5% by mass in the non-aqueous electrolyte.

(In the general formula (II), X ^{11 to} X ¹⁵ each independently represent a hydrogen atom or a halogen atom, and 1 to 4 of X ^{11 to} X ¹⁵ are halogen atoms.)
(4) In an electricity storage device including a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, the non-aqueous electrolyte is the non-aqueous electrolyte described in (3). A power storage device characterized.

According to the first invention, there are provided a non-aqueous electrolyte capable of improving electrochemical characteristics in a wide temperature range, in particular, charge storage characteristics and low-temperature output characteristics after charge storage, and an electricity storage device such as a lithium battery using the non-aqueous electrolyte. be able to.
According to the second invention, a non-aqueous electrolyte that can improve electrochemical characteristics in a wide temperature range, particularly a non-aqueous electrolyte that can reduce the rate of increase in electrode thickness after a high-temperature cycle, and lithium using the same An electricity storage device such as a battery can be provided.

  Hereinafter, the nonaqueous electrolytic solutions of the first invention and the second invention will be sequentially described.

[Non-aqueous electrolyte of the first invention]
The non-aqueous electrolyte of the first invention is a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent. It is a non-aqueous electrolyte characterized by including a compound and content of this biphenyl compound is 0.1-4.5 mass% in a non-aqueous electrolyte.

The reason why the nonaqueous electrolytic solution of the first invention can improve electrochemical characteristics in a wide temperature range, in particular, charge storage characteristics and low-temperature output characteristics after charge storage is not necessarily clear, but is considered as follows.
A part of the phosphoric ester structure in the biphenyl compound represented by the general formula (I) contained in the nonaqueous electrolytic solution of the first invention is electrochemically reduced on the negative electrode side to form a film. Since the coating includes both a coating component having high thermal stability derived from the biphenyl structure and a coating component excellent in lithium ion conductivity derived from the phosphate ester structure, an increase in electrical resistance of the coating is suppressed. For this reason, it is thought that the charge storage characteristic of electrical storage devices, such as a lithium secondary battery, improves.
A part of the reductive decomposition product of the biphenyl compound represented by the general formula (I) also forms a film on the positive electrode. Since the coating film is excellent in lithium ion conductivity even after being stored under charge, it is considered that the low-temperature output characteristics after storage under charge are improved.
Such an effect is manifested when the biphenyl compound containing the phosphate structure represented by the general formula (I) is used in a non-aqueous electrolyte solution. This is an exceptional effect of the present invention that cannot be realized by the method of previously forming a polymer film on the positive electrode.

  The biphenyl compound containing the phosphate ester structure contained in the nonaqueous electrolytic solution of the first invention is represented by the following general formula (I).

(In General Formula (I), R ¹ and R ² are each independently an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 3 to 8 carbon atoms, or the number of carbon atoms. 6 to 20 aryl groups, each of the alkyl group, alkenyl group, alkynyl group or aryl group may have at least one hydrogen atom substituted with a halogen atom.
X ¹ and X ² each independently represent a halogen atom or a halogenated alkyl group having 1 to 6 carbon atoms, m is an integer of 0 to 4, and n is an integer of 0 to 5. )

In the general formula (I), specific examples of X ¹ and X ² include linear alkyl such as methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, or n-hexyl group. A branched alkyl group of a group, isopropyl group, sec-butyl group, tert-butyl group, or tert-amyl group is preferred.
In general formula (I), m is preferably 3 or less, more preferably 2 or less, still more preferably 1 or less, and most preferably 0 from the viewpoint of improving electrochemical characteristics in a wide temperature range.
In the general formula (I), n is preferably 4 or less, more preferably 2 or less, still more preferably 1 or less, and most preferably 0 from the viewpoint of improving electrochemical characteristics in a wide temperature range.

In the general formula (I), specific examples of R ¹ and R ² include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, or linear alkyl group such as n-octyl group; branched alkyl group of isopropyl group, sec-butyl group, tert-butyl group, tert-amyl group, or 2-ethylhexyl group; vinyl group, 2-propenyl group A straight chain alkenyl group having 3 to 6 carbon atoms such as 2-butenyl group or 3-butenyl group; a branched alkenyl group of 2-methyl-2-propenyl group; 2-propynyl group, 2-butynyl group, 3 A straight-chain alkynyl group having 2 to 6 carbon atoms such as -butynyl group, 4-pentynyl group, or 5-hexynyl group; 1-methyl-2-propynyl group, 1-methyl-2-butynyl group, or 1,1- Dimethyl-2- A branched alkynyl group having 4 to 6 carbon atoms such as lopinyl group; fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2-fluoroethyl group, 2,2-difluoroethyl group, or 2,2,2-trimethyl Fluoroalkyl group such as fluoroethyl group; phenyl group, 2-methylphenyl group, 2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-tert- Butylphenyl group, 2-fluorophenyl group, 4-fluorophenyl group, 4-trifluoromethylphenyl group, 2,4-difluorophenyl group, perfluorophenyl group, 2-phenylphenyl group, 3-phenylphenyl group, 4 Preferred examples include aryl groups having 6 to 14 carbon atoms such as phenylphenyl group or 2,6-diphenylphenyl group. That.
Among these, methyl group, ethyl group, n-propyl group, isopropyl group, vinyl group, 2-propenyl group, 2-propynyl group, 2-butynyl group, 3-butynyl group, phenyl group, 2,4-dimethylphenyl Group, 2-fluorophenyl group, 3-fluorophenyl group or 4-fluorophenyl group is preferable, and methyl group, ethyl group, 2-propenyl group, 2-propynyl group and phenyl group are more preferable.

  The effect of improving electrochemical characteristics in a wide temperature range, in particular, charge storage characteristics and low-temperature output characteristics after charge storage, also depends on the substitution position of the phosphate ester structure. In general formula (I), a compound in which the phosphate ester structure is substituted at the 2-position or 3-position of the biphenyl structure is more preferred, and a compound substituted at the 2-position is more preferred.

  Specific examples of the biphenyl compound containing the phosphate structure represented by the general formula (I) include the following compounds.

Among the above compounds, compounds A1 to A13, A23 to A33, and A35 to A42 in which the biphenyl group is not substituted with a halogen atom or a haloalkyl group are more preferable. Further preferred compounds are 2-phenylphenyl dimethyl phosphate (compound A1), 2-phenylphenyl diethyl phosphate (compound A2), 2-phenylphenyl diisopropyl phosphate (compound A3), 2-phenylphenyl dibutyl phosphate (compound A4), 2-phenylphenyl divinyl phosphate (compound A5), 2-phenylphenyl diallyl phosphate (compound A6), 2-phenylphenyl di (2-propynyl) phosphate (compound A7), 2-phenylphenyl phosphate Diphenyl (compound A8), 2-phenylphenyl bis (2,2,2-trifluoroethyl) phosphate (compound A9), 2-phenylphenyl bis (4-fluorophenyl) phosphate (compound A10), phosphoric acid 2 -Phenylphenyl bis (4-chlorophenyl) (compound A11) 2-phenylphenyl bis (3-fluorophenyl) phosphate (compound A12), 2-phenylphenyl bis (2-fluorophenyl) phosphate (compound A13), 3-phenylphenyl dimethyl phosphate (compound A23), phosphorus 3-phenylphenyl diethyl acid (compound A24), 3-phenylphenyl dibutyl phosphate (compound A25), 3-phenylphenyl divinyl phosphate (compound A26), 3-phenylphenyl diallyl phosphate (compound A27), phosphoric acid 3 -Phenylphenyl di (2-propynyl) (compound A28), 3-phenylphenyl diphenyl phosphate (compound A29), 3-phenylphenyl bis (4-fluorophenyl) phosphate (compound A30), 3-phenylphenyl phosphate Bis (3-fluorophenyl) (compound 31), one or two selected from 3-phenylphenyl bis (2-fluorophenyl) phosphate (compound A32) and 3-phenylphenyl bis (2,2,2-trifluoroethyl) phosphate (compound A33) More than a kind of compound.
Among the above compounds, particularly preferred compounds are 2-phenylphenyl dimethyl phosphate (compound A1), 2-phenylphenyl diethyl phosphate (compound A2), 2-phenylphenyl diisopropyl phosphate (compound A3), 2-phosphate phosphate Phenylphenyl divinyl (compound A5), 2-phenylphenyl diallyl phosphate (compound A6), 2-phenylphenyl di (2-propynyl) phosphate (compound A7), 2-phenylphenyl diphenyl phosphate (compound A8), and 2-phenylphenyl phosphate One or more compounds selected from bis (2,2,2-trifluoroethyl) (Compound A9).

  In the nonaqueous electrolytic solution of the first invention, the content of the biphenyl compound represented by the general formula (I) contained in the nonaqueous electrolytic solution is 0.1 to 4.5% by mass in the nonaqueous electrolytic solution. It is. If the content is 4.5% by mass or less, there is little possibility that a film is excessively formed on the electrode and the electrochemical characteristics are lowered, and if it is 0.1% by mass or more, the film is sufficiently formed. The effect of improving the charge storage characteristics is enhanced. The content is preferably 0.2% by mass or more, and more preferably 0.5% by mass or more in the nonaqueous electrolytic solution. Moreover, the upper limit is preferably 4% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

  In the nonaqueous electrolytic solution of the first invention, the biphenyl compound represented by the general formula (I) is combined with a nonaqueous solvent, an electrolyte salt, and other additives described below to combine electrochemical characteristics in a wide temperature range. In particular, it exhibits a unique effect that the effect of improving the charge storage characteristics and the low-temperature output characteristics after storage is synergistically improved.

[Nonaqueous Electrolytic Solution of Second Invention]
The non-aqueous electrolyte of the second invention is a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, and an asymmetric halogenated phenyl carbonate compound represented by the following general formula (II) is contained in the non-aqueous electrolyte. In addition, the non-aqueous electrolyte is characterized in that the content of the halogenated phenyl carbonate compound is 0.001 to 5% by mass in the non-aqueous electrolyte.

(In the general formula (II), X ^{11 to} X ¹⁵ each independently represent a hydrogen atom or a halogen atom, and 1 to 4 of X ^{11 to} X ¹⁵ are halogen atoms.)

The reason why the nonaqueous electrolytic solution of the second invention can improve the electrochemical characteristics in a wide temperature range, particularly at high temperatures, and further reduce the increase rate of the electrode thickness after the high temperature cycle is not necessarily clear, but is as follows. Can be considered.
In the asymmetric halogenated phenyl carbonate compound contained in the non-aqueous electrolyte of the second invention, one of the two benzene rings bonded to the oxygen atom has 1 to 4 halogen atoms, and the other benzene ring has a substituent. There is no asymmetric carbonate. Therefore, the asymmetric halogenated phenyl carbonate compound is intermediate between the case where all of one benzene ring is a compound substituted with a halogen atom and the case where the compound is not substituted with a halogen atom at all. Expected to show susceptibility to redox. At the same time, a strong film (SEI) that does not hinder the permeation of lithium ions without excessive polymerization due to having a specific number of C—H bonds that are considered to be involved in polymerization, that is, a portion that is not substituted with a halogen atom. It is thought that it becomes easy to form a film. It is considered that this coating can suppress further decomposition of the solvent and suppress an increase in the thickness of the positive electrode and the negative electrode (particularly the negative electrode) after the high-temperature cycle.

  The asymmetric halogenated phenyl carbonate compound contained in the nonaqueous electrolytic solution of the second invention is represented by the following general formula (II).

(In the general formula (II), X ^{11 to} X ¹⁵ each independently represent a hydrogen atom or a halogen atom, and 1 to 4 of X ^{11 to} X ¹⁵ are halogen atoms.)

  In the general formula (II), specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. Among these, a fluorine atom or a chlorine atom is preferable, and a chlorine atom is more preferable from the viewpoint of easily forming a film that is stable on both the positive electrode and the negative electrode and excellent in lithium ion permeability upon oxidation and reduction.

In general formula (II), a compound in which 1 to 4 of X ^{11 to} X ¹⁵ are halogen atoms, in particular, a compound having 3 or less halogen atoms is preferable, and a compound having 2 or less halogen atoms. It is more preferable because the balance of oxidation-reduction is increased, and it is easy to form a coating film that is stable on both the positive electrode and the negative electrode and is excellent in lithium ion permeability, and is particularly a compound having one halogen atom. Further, the effect of suppressing the increase in the thickness of the negative electrode is further increased, which is further preferable.
The effect of suppressing the increase in thickness of the positive electrode and the negative electrode (particularly the negative electrode) also depends on the substitution position of the halogen atom. In the general formula (II), when a halogen atom is present in the ortho position (X ¹¹ or X ¹⁵ ) or the para position (X ¹³ ), the effect of suppressing an increase in the thickness of the electrode is enhanced, and in particular, the ortho position (X ¹¹ Or it is preferable to have a halogen atom in X ¹⁵ ).

  Specific examples of the compound represented by the general formula (II) include the following compounds. In the following formula, Ph represents a phenyl group.

  Among the above compounds, compounds B1 to B15 and B19 to B38 are preferable, compounds B1 to B9 and B19 to B27 are more preferable, 2-fluorophenyl phenyl carbonate (compound B1), 4-fluorophenyl phenyl carbonate (compound B3), 2 , 4-difluorophenyl phenyl carbonate (compound B5), 2,6-difluorophenyl phenyl carbonate (compound B7), 2-chlorophenyl phenyl carbonate (compound B19), 3-chlorophenyl phenyl carbonate (compound B20), 4-chlorophenyl phenyl carbonate (Compound B21), 2,4-dichlorophenyl phenyl carbonate (Compound B23), and 2,6-dichlorophenyl phenyl carbonate (Compound B25) Species or two or more compounds are more preferred. When these compounds are used, it is easy to form a coating film that is stable and excellent in lithium ion permeability on both the positive electrode and the negative electrode due to oxidation and reduction, and an increase in electrode thickness can be suppressed.

  In the non-aqueous electrolyte of the present invention, the content of the asymmetric halogenated phenyl carbonate compound represented by the general formula (II) contained in the non-aqueous electrolyte is 0.001 to 5 mass in the non-aqueous electrolyte. % Is preferred. If the content is 5% by mass or less, there is little possibility that the film is excessively formed on the electrode and the thickness of the electrode increases, and if it is 0.001% by mass or more, the film is sufficiently formed, and the high temperature cycle is performed. Since the characteristics are enhanced, the above range is preferable. The content is more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more in the non-aqueous electrolyte. Moreover, the upper limit is more preferably 3% by mass or less, and further preferably 2% by mass or less.

  If the non-aqueous electrolyte of the present invention further contains a symmetric phenyl carbonate compound, the coating becomes stronger and a specific effect that the rate of increase in electrode thickness after a high temperature cycle can be further reduced is preferable.

  As a symmetrical phenyl carbonate compound, as long as two benzene rings are the same, they may be substituted with a halogen atom.

  Specific examples of the symmetric phenyl carbonate include diphenyl carbonate, bis (2-fluorophenyl) carbonate, bis (3-fluorophenyl) carbonate, bis (4-fluorophenyl) carbonate, and bis (2,4-difluorophenyl) carbonate. And at least one selected from the group consisting of bis (2-chlorophenyl) carbonate, bis (3-chlorophenyl) carbonate, bis (4-chlorophenyl) carbonate, and bis (2,4-dichlorophenyl) carbonate.

  Among them, diphenyl carbonate, bis (4-fluorophenyl) carbonate, bis (2,4-difluorophenyl) carbonate, bis (2-chlorophenyl) carbonate, bis (3-chlorophenyl) carbonate, bis (4-chlorophenyl) carbonate, bis (2,4-dichlorophenyl) carbonate is preferred, diphenyl carbonate, bis (2-chlorophenyl) carbonate, bis (3-chlorophenyl) carbonate, bis (4-chlorophenyl) carbonate, bis (2,4-dichlorophenyl) carbonate are more preferred. Bis (2-chlorophenyl) carbonate, bis (3-chlorophenyl) carbonate, and bis (4-chlorophenyl) carbonate are more preferable.

  As content of the symmetric phenyl carbonate contained in the non-aqueous electrolyte, the mass ratio of [asymmetric halogenated phenyl carbonate compound / symmetric phenyl carbonate compound] is 50/50 to 99.9 / 0.1. In view of the fact that the coating film is not likely to become strong, it is preferable, 80/20 to 99.5 / 0.5 is more preferable, and 95/5 to 99.3 / 0.7 is further preferable.

  In the non-aqueous electrolyte of the present invention, the specific asymmetric halogenated phenyl carbonate represented by the general formula (II) is combined with a non-aqueous solvent, an electrolyte salt, and other additives described below at a high temperature. Electrochemical properties are synergistically improved and a unique effect of reducing the increase rate of the electrode thickness is exhibited.

<First invention and second invention>
[Nonaqueous solvent]
As the nonaqueous solvent used in the nonaqueous electrolytic solution of the present invention, one or more selected from cyclic carbonates, chain esters, lactones, ethers and amides are preferably mentioned. In order to synergistically improve electrochemical characteristics in a wide temperature range and electrochemical characteristics at high temperatures, it is preferable that a chain ester is included, more preferably a chain carbonate is included, and a cyclic carbonate and a chain carbonate are included. More preferably, both carbonates are included.
The term “chain ester” is used as a concept including a chain carbonate and a 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 collectively referred to as “DFEC”), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and 4-ethynyl-1 , 3-dioxolan-2-one (EEC), or one or more thereof, ethylene carbonate, propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinylene carbonate, and 4-ethynyl 1 selected from -1,3-dioxolan-2-one (EEC) Or two or more is more preferable.

  Further, it is preferable to use at least one of unsaturated bonds such as carbon-carbon double bonds or carbon-carbon triple bonds, or cyclic carbonates having a fluorine atom, since the electrochemical properties in a wide temperature range are further improved, Alternatively, the electrochemical characteristics at high temperature are further improved, and the rate of increase in the electrode thickness can be reduced, which is preferable, and a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond and a ring having a fluorine atom More preferably, both carbonates are included. As the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or carbon-carbon triple bond, VC, VEC, or EEC is more preferable, and as the cyclic carbonate having a fluorine atom, FEC or DFEC is more preferable.

(In the case of the first invention)
In the case of the first invention, 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 based on the total volume of the nonaqueous solvent. More preferably, it is 0.2% 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, still more preferably 2. 5 vol% or less is preferable because electrochemical characteristics in a wider temperature range can be further improved without impairing Li ion permeability.
The content of the cyclic carbonate having a fluorine atom is preferably 0.07% by volume or more, more preferably 4% by volume or more, still more preferably 6% by volume or more based on the total volume of the nonaqueous solvent. When the upper limit is preferably 35% by volume or less, more preferably 25% by volume or less, and further 15% by volume or less, electrochemical characteristics in a wider temperature range can be improved without impairing Li ion permeability. It is preferable because it is possible.

  When the non-aqueous solvent contains 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 carbon to the content of the cyclic carbonate having a fluorine atom The content of the cyclic carbonate having an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond is preferably 0.2% by volume or more, more preferably 3% by volume or more, and further preferably 7% by volume or more. The upper limit is preferably 40% by volume or less, more preferably 30% by volume or less, and even more preferably 15% by volume or less, and the electrochemical characteristics in a wider temperature range can be obtained without impairing Li ion permeability. Since it can improve, it is especially preferable.

  In addition, when the non-aqueous solvent contains both ethylene carbonate and a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond, the electrochemistry over a wide temperature range of the film formed on the electrode It is preferable because the characteristics can be improved, and the content of ethylene carbonate and a cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is preferably based on the total volume of the nonaqueous solvent. 3 volume% or more, more preferably 5 volume% or more, more preferably 7 volume% or more, and the upper limit thereof is preferably 45 volume% or less, more preferably 35 volume% or less, still more preferably 25 volume%. % Or less.

(In the case of the second invention)
In the case of the second invention, 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 based on the total volume of the nonaqueous solvent. More preferably, it is 0.2% by volume or more, more preferably 0.7% by volume or more, and the upper limit thereof is preferably 9% by volume or less, more preferably 6% by volume or less, still more preferably 5% by volume. % Or less is preferable because the stability of the coating at high temperatures can be increased.
The content of the cyclic carbonate having a fluorine atom is preferably 0.07% by volume or more, more preferably 4% by volume or more, still more preferably 7% by volume or more, based on the total volume of the nonaqueous solvent. The upper limit is preferably 35% by volume or less, more preferably 25% by volume or less, and even more preferably 15% by volume or less, which can further increase the stability of the coating at high temperatures and increase the increase rate of the electrode thickness. Since it can reduce, it is preferable.

When the non-aqueous solvent contains 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 carbon- relative to the content of the cyclic carbonate having a fluorine atom The content of the cyclic carbonate having an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond is preferably 0.2% by volume or more, more preferably 3% by volume or more, and further preferably 7% by volume or more. The upper limit is preferably 40% by volume or less, more preferably 30% by volume or less, and even more preferably 15% by volume or less, which can further increase the stability of the coating film at a high temperature and increase the electrode thickness. This is preferable because the rate of increase can be reduced.
Further, when the nonaqueous solvent contains ethylene carbonate and / or propylene carbonate, the stability of the film formed on the electrode is increased, and the rate of increase in the electrode thickness can be reduced, and the content of ethylene carbonate and / or propylene carbonate is preferable. Is preferably 3% by volume or more, more preferably 5% by volume or more, still more preferably 7% by volume or more, and the upper limit thereof is preferably 45% by volume or less, based on the total volume of the nonaqueous solvent. More preferably, it is 35 volume% or less, More preferably, it is 25 volume% or less.

(Common to the first and second inventions)
The above solvents may be used alone or in combination of two or more, because the effect of improving electrochemical properties over a wide temperature range is further improved, or the stability of the coating at high temperatures It is preferable to use three or more kinds in combination, because the properties increase further, the rate of increase in the electrode thickness can be reduced, and the electrochemical characteristics in a wide temperature range are further improved. Preferred 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 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, One or more symmetrical linear carbonates selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate, pivalate esters such as methyl pivalate, ethyl pivalate, and propyl pivalate Preferable examples include one or more chain carboxylic acid esters selected from methyl propionate, ethyl propionate, propyl propionate, methyl acetate, and ethyl acetate (EA).
Among the chain esters, chain esters having a methyl group selected from dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, methyl propionate, methyl acetate and ethyl acetate (EA) are preferable. In particular, a chain carbonate having a methyl group is preferred.
Moreover, when using chain carbonate, it is preferable to use 2 or more types. Further, it is more preferable that both a symmetric chain carbonate and an asymmetric chain carbonate are contained, and it is further more preferable that the content of the symmetric chain carbonate is more than that of 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 nonaqueous 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. The above range is preferable because there is little possibility that the characteristics will deteriorate, or there is little possibility that the electrochemical characteristics at a wide temperature range, particularly at high temperatures, will decrease.

  The volume ratio of the symmetric chain carbonate in the chain carbonate is preferably 51% by volume or more, and more preferably 55% by volume or more. The upper limit is more preferably 95% by volume or less, and still more preferably 85% by volume or less. It is particularly preferred that the symmetric chain carbonate contains dimethyl carbonate. The asymmetric chain carbonate preferably has a methyl group, and methyl ethyl carbonate is particularly preferable. In the above case, it is preferable because the electrochemical characteristics at a wider temperature range, particularly at high temperature, are improved, or the stability of the coating at high temperature is increased, the rate of increase in electrode thickness can be reduced, and a wider temperature range, especially It is preferable because electrochemical characteristics at high temperature are improved.

  The ratio between the cyclic carbonate and the chain ester is such that the cyclic carbonate / chain ester (volume ratio) is from the viewpoint of improving the electrochemical properties at high temperatures or from the viewpoint of improving the electrochemical properties at a wide temperature range, particularly at high temperatures. 10/90 to 45/55 are preferable, 15/85 to 40/60 are more preferable, and 20/80 to 35/65 are particularly preferable.

Other nonaqueous 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. Preferable examples include one or two or more selected from amides such as cyclic ethers, amides such as dimethylformamide, sulfones such as sulfolane, and lactones such as γ-butyrolactone (GBL), γ-valerolactone, and α-angelicalactone.
The other non-aqueous solvents are usually used as a mixture in order to achieve appropriate physical properties. The combination includes, for example, 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 (chain carbonate) and a lactone, and a cyclic carbonate and a chain. Preferred examples include combinations of esters (chain carbonates) and ethers, and combinations of cyclic carbonates, chain carbonates and chain carboxylic acid esters, etc., and combinations of cyclic carbonates, chain esters and lactones are more preferred. Of these, γ-butyrolactone (GBL) is more preferred.

  The content of the other nonaqueous solvent is usually 1% or more, preferably 2% or more, and usually 40% or less, preferably 30% or less, more preferably 20%, based on the total volume of the nonaqueous solvent. It is as follows.

(In the case of the first invention)
In the case of the first invention, it is preferable to add other additives to the non-aqueous electrolyte for the purpose of improving electrochemical characteristics over a wider temperature range.
Specific examples of other additives include the following compounds (A) to (I).

(A) One or more nitriles selected from acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and sebacononitrile.
(B) Aromatic compounds having a branched alkyl group such as cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, 1-fluoro-4-tert-butylbenzene, biphenyl, terphenyl (o-, m-, p-form), aromatic compounds such as fluorobenzene, methylphenyl carbonate, ethylphenyl carbonate, and diphenyl carbonate.
(C) selected from 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- One or more triple bond-containing compounds selected from propynyl, di (2-propynyl) oxalate, 2-butyne-1,4-diyl dimethanesulfonate, and 2-butyne-1,4-diyl diformate.
(E) 1,3-propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propene sultone, or 2,2-dioxide-1,2-oxathiolane-4- Sultone such as yl acetate, cyclic sulfite such as ethylene sulfate, cyclic sulfate such as ethylene sulfate, butane-2,3-diyl dimethanesulfonate, butane-1,4-diyl dimethanesulfonate, or methylenemethane disulfonate One or more S = O group-containing compounds selected from vinyl sulfone compounds such as sulfonic acid ester, divinyl sulfone, 1,2-bis (vinylsulfonyl) ethane, or bis (2-vinylsulfonylethyl) ether .
(F) Cyclic acetal compounds such as 1,3-dioxolane, 1,3-dioxane and 1,3,5-trioxane.

(G) Trimethyl phosphate, tributyl phosphate, trioctyl phosphate, tris (2,2,2-trifluoroethyl) phosphate, ethyl 2- (diethoxyphosphoryl) acetate, and 2-propynyl 2- (diethoxyphosphoryl) ) One or more phosphorus-containing compounds selected from acetate.
(H) Chain carboxylic 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 Cyclic acid anhydrides such as products.
(I) Cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, or ethoxyheptafluorocyclotetraphosphazene.

Among these, it is preferable to include at least one selected from (A) nitrile, (B) aromatic compound, and (C) isocyanate compound, since the electrochemical characteristics in a wider temperature range are further improved.
Among (A) nitriles, one or more selected from succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile are more preferable.
(B) Among aromatic compounds, one or two selected from biphenyl, terphenyl (o-, m-, p-form), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene The above is more preferable, and one or more selected from biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are particularly preferable.
Among (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 the compounds (A) to (C) is preferably 0.01 to 7% by 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 enhanced. The content is more preferably 0.05% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 5% by mass or less, further preferably 3% by mass or less. .

(D) Triple bond-containing compound, (E) Sultone, cyclic sulfite, sulfonic acid ester, cyclic S = O group-containing compound selected from vinyl sulfone, (F) cyclic acetal compound, (G) It is preferable to include a phosphorus-containing compound, (H) a cyclic acid anhydride, and (I) a cyclic phosphazene compound because the electrochemical properties in a wider temperature range are further improved.
(D) As a triple bond containing compound, 2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, di (2-propynyl) oxalate, and 2-butyne-1 , 4-diyl dimethanesulfonate is preferably selected from one or two or more, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, di (2-propynyl) oxalate, and 2-butyne-1,4- One or more selected from diyl dimethanesulfonate is more preferable.
(E) A cyclic or chain-containing S═O group-containing compound selected from sultone, cyclic sulfite, cyclic sulfate, sulfonic acid ester, and vinyl sulfone (provided that the triple bond-containing compound and any one of the above general formulas are used) It is preferable to use a specific compound).

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, 2,2-dioxide- One or more selected from 1,2-oxathiolan-4-yl acetate, methylene methane disulfonate, ethylene sulfite, and ethylene sulfate are preferred.
Examples of the chain-like S═O group-containing compound include butane-2,3-diyl dimethanesulfonate, butane-1,4-diyl dimethanesulfonate, dimethylmethane disulfonate, pentafluorophenyl methanesulfonate, divinylsulfone, And one or more selected from bis (2-vinylsulfonylethyl) ether are preferred.
Among the cyclic or chain-containing 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 , Ethylene sulfate, pentafluorophenyl methanesulfonate, and one or more selected from divinylsulfone are more preferable.

(F) As the cyclic acetal compound, 1,3-dioxolane or 1,3-dioxane is preferable, and 1,3-dioxane is more preferable.
(G) The phosphorus-containing compound is more preferably tris (2,2,2-trifluoroethyl) phosphate, ethyl 2- (diethoxyphosphoryl) acetate, or 2-propynyl 2- (diethoxyphosphoryl) acetate.
(H) As the cyclic acid anhydride, succinic anhydride, maleic anhydride, or 3-allyl succinic anhydride is preferable, and succinic anhydride or 3-allyl succinic anhydride is more preferable.
(I) As the cyclic phosphazene compound, a cyclic phosphazene compound such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, or phenoxypentafluorocyclotriphosphazene is preferable, and methoxypentafluorocyclotriphosphazene or ethoxypentafluorocyclo More preferred is triphosphazene.

  The content of the compounds (D) to (I) is preferably 0.001 to 5% by 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 enhanced. The content is more preferably 0.01% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 3% by mass or less, and further preferably 2% by mass or less. .

In addition, for the purpose of improving 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 included in the non-aqueous electrolyte. It is preferable to include one or more lithium salts selected from the inside.
Specific examples of lithium salts include lithium bis (oxalato) borate [LiBOB], lithium difluoro (oxalato) borate [LiDFOB], lithium tetrafluoro (oxalato) phosphate [LiTFOP], and lithium difluorobis (oxalato) phosphate [LiDFOP]. A lithium salt having at least one oxalic acid skeleton selected from Lithium salt having a phosphoric acid skeleton such as LiPO ₂ F ₂ or Li ₂ PO ₃ F, lithium trifluoro ((methanesulfonyl) oxy) borate [LiTFMSB], Lithium pentafluoro ((methanesulfonyl) oxy) phosphate [LiPFMSP], lithium methyl sulfate [LMS], lithium ethyl sulfate [LES], lithium 2,2,2-tri Le Oro ethylsulfate [LFES], and lithium salts suitably having 1 or more S = O group selected from _FSO 3 Li. Among these, it is more preferable to include a lithium salt selected from LiBOB, LiDFOB, LiTFOP, LiDFOP, LiPO ₂ F ₂ , LiTFMSB, LMS, LES, LFES, and FSO ₃ Li.

  The proportion 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 electrochemical characteristics over a wide temperature range is further exhibited. Preferably it is 0.01M or more, More preferably, it is 0.03M or more, Most preferably, it is 0.04M or more. The upper limit is more preferably 0.4M or less, and particularly preferably 0.2M or less. (However, M represents mol / L.)

(In the case of the second invention)
In the nonaqueous electrolytic solution of the second invention, as an additive that can be used in combination with the asymmetric halogenated phenyl carbonate compound represented by the general formula (II), (a) a SO ₂ group-containing compound, (b) fluorine Benzene compound, (c) phosphate ester compound, (d) carbon-carbon triple bond-containing compound, (e) carboxylic acid anhydride, (f) isocyanate compound, (g) lithium-containing ionic compound, (h) nitrile Examples thereof include at least one selected from a compound, (i) a benzene compound, (j) a cyclic acetal compound, and (k) a phosphazene compound. By including at least one selected from the compounds of (a) to (k), a mixed SEI film is formed by four or five or more functional groups or characteristic groups, and the rate of increase in electrode thickness after high-temperature cycling is increased. The effect of reducing can be further enhanced.

The (a) SO ₂ group-containing compound is not particularly limited as long as it is a compound having an “SO ₂ group” in the molecule. Specific examples thereof include 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-oxathiolane- Sultone such as 4-yl acetate or 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, ethylene sulfite, butane-2,3-diyl dimethanesulfonate, butane-1,4 -One or more types selected from the group consisting of diyl dimethane sulfonate, pentane-1,5-diyl dimethane sulfonate, methylene methane disulfonate, divinyl sulfone and the like are preferable, and two or more types are more preferable.
Among the SO ₂ group-containing compounds, 1,3-propane sultone, 1,4-butane sultone, 2,4-butane sultone, 2,2-dioxido-1,2-oxathiolan-4-yl acetate, 5,5-dimethyl -1,2-oxathiolane-4-one One or more selected from the group consisting of 2,2-dioxide, butane-2,3-diyl dimethanesulfonate, and divinylsulfone is more preferable.

The type of (b) fluorinated benzene compound is not particularly limited as long as it has a “phenyl group in which at least a part of the benzene ring is substituted with fluorine” in the molecule. Specific examples thereof include fluorobenzene, difluorobenzene (o, m, p form), 2,4-difluoroanisole, 1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4. -Cyclohexyl benzene, pentafluorophenyl methane sulfonate, 2-fluorophenyl methane sulfonate, 3-fluorophenyl methane sulfonate, 4-fluorophenyl methane sulfonate, 2,4-difluorophenyl methane sulfonate, 3,4-difluorophenyl methane sulfonate, 2 , 3,4-trifluorophenylmethanesulfonate, 2,3,5,6-tetrafluorophenylmethanesulfonate, 4-fluoro-3-trifluoromethylphenylmethanesulfonate, and 4- Ruoro-3-one or more suitably include selected from trifluoromethylphenyl methyl carbonate, or two or more is more preferable.
Examples of the fluorinated benzene compound include fluorobenzene, 2,4-difluoroaniol, 1-fluoro-4-cyclohexylbenzene, pantafluorophenylmethanesulfonate, 2-fluorophenylmethanesulfonate, 2,4-difluorophenylmethanesulfonate, And at least one selected from the group consisting of 4-fluoro-3-trifluoromethylphenylmethanesulfonate.

  The type of (c) phosphate ester compound is not particularly limited as long as it is a compound having a “P (═O) group” in the molecule. Specific examples thereof include trimethyl phosphate, tributyl phosphate, and trioctyl phosphate, tris (2,2,2-trifluoroethyl) phosphate, bis (2,2,2-trifluoroethyl) methyl phosphate, Bis (2,2,2-trifluoroethyl) phosphate, bis (2,2,2-trifluoroethyl) phosphate, 2,2-difluoroethyl phosphate, bis (2,2,2-trifluoroethyl phosphate) ) 2,2,3,3-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) (2,2,3,3-tetrafluoropropyl) methyl phosphate, tris (1,1,1,3, phosphate) 3, -Hexafluoropropan-2-yl), methyl methylene bisphosphonate, ethyl methylene bisphosphonate, methyl ethylene bisphosphonate, ethyl ethylene bisphosphonate, methyl butylene bisphosphonate, ethyl butylene bisphosphonate, 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- (die One or more selected from the group consisting of (toxylphosphoryl) acetate, 2-propynyl 2- (dimethoxyphosphoryl) acetate, 2-propynyl 2- (diethoxyphosphoryl) acetate, methyl pyrophosphate, ethyl pyrophosphate and the like are preferable examples. 2 or more are more preferable.

  Among the phosphoric acid ester compounds, tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3-hexafluoropropan-2-yl), 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 is preferred, Tris phosphate (2,2,2-trifluoroethyl), Tris phosphate (1,1,1,3,3,3-hexafluoropropan-2-yl) , Ethyl 2- (diethoxyphosphoryl) acetate, and 2-propynyl 2- (dieto One or more selected from the group consisting of (xyphosphoryl) acetate is more preferred.

(D) The type of the carbon-carbon triple bond-containing compound is not particularly limited as long as it is a compound having a “carbon-carbon triple bond” in the molecule. Specific examples include 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinyl sulfonate, 2- (methanesulfonyloxy) propion. 2-propynyl acid, di (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, di (2-propynyl) glutarate, 2-butyne-1,4-diyl dimethanesulfonate One or more selected from the group consisting of 2-butyne-1,4-diyl diformate, 2,4-hexadiyne-1,6-diyl dimethanesulfonate, and the like are preferable, and two or more are more preferable. is there.
Among the triple bond compounds, 2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di (2- Propinyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, 2-butyne-1,4-diyl dimethanesulfonate, and 2-butyne-1,4-diyl diformate Preferably, 2-propynyl methyl carbonate, methanesulfonic acid 2-propynyl, vinylsulfonic acid 2-propynyl, 2- (methanesulfonyloxy) propionic acid 2-propynyl, di (2-propynyl) oxalate, 2-butyne-1,4 − Yl dimethanesulfonate, and one or more members selected from the group consisting of 2-butyne-1,4-diyl diformate are more preferred.

The type of carboxylic acid anhydride is not particularly limited as long as it is a compound having a “C (═O) —O—C (═O) group” in the molecule. Specific examples thereof include linear carboxylic acid anhydrides such as acetic anhydride and propionic anhydride, succinic anhydride, maleic anhydride, allyl succinic anhydride, glutaric anhydride, itaconic anhydride, and 3-sulfo-propionic acid. One or more kinds selected from the group consisting of cyclic acid anhydrides such as anhydrides are preferably mentioned, and two or more kinds are more preferred.
Among the carboxylic acid anhydrides, one or more selected from succinic anhydride, maleic anhydride, and allyl succinic anhydride are preferable, and one selected from succinic anhydride and allyl succinic anhydride is more preferable.

(F) The isocyanate compound is not particularly limited as long as it is a compound having “N═C═O group”. Specific examples thereof include methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl. One or more kinds selected from the group consisting of methacrylate and the like are preferably mentioned, and two or more kinds are more preferred.
Among the isocyanate compounds, one or more selected from hexamethylene diisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate are preferable, hexamethylene diisocyanate, 2-isocyanatoethyl acrylate, and One or more selected from 2-isocyanatoethyl methacrylate is more preferable.

(G) The lithium-containing ionic compound is not particularly limited as long as it is a compound having “lithium” as a cation species. Specific examples thereof include lithium difluorophosphate, lithium fluorophosphate, lithium fluorosulfonate, difluorobis [oxalate-O, O ′] lithium phosphate (LiPFO), and tetrafluoro [oxalate-O, O ′] phosphate. Lithium, bis [oxalate-O, O ′] lithium borate (LiBOB), difluoro [oxalate-O, O ′] lithium borate, lithium methyl sulfate, lithium ethyl sulfate, lithium propyl sulfate, and the like are selected. 1 or more types are mentioned suitably, 2 or more types are more suitable.
Among the lithium-containing ionic compounds, lithium difluorophosphate, lithium fluorosulfonate, difluorobis [oxalate-O, O ′] lithium phosphate (LiPFO), lithium tetrafluoro [oxalate-O, O ′] lithium phosphate, One or more selected from lithium bis [oxalate-O, O ′] lithium borate (LiBOB), difluoro [oxalate-O, O ′] lithium borate, lithium methyl sulfate, lithium ethyl sulfate, and lithium propyl sulfate are more preferable. Two or more are particularly preferred.

  The combination of two or more of the lithium-containing ionic compounds includes lithium ethyl sulfate, lithium difluorophosphate, lithium fluorosulfonate, difluorobis [oxalate-O, O ′] lithium phosphate (LiPFO), tetrafluoro [ Oxalate-O, O ′] lithium phosphate, bis [oxalate-O, O ′] lithium borate (LiBOB), difluoro [oxalate-O, O ′] lithium borate, and at least one selected from lithium methyl sulfate In combination, lithium ethyl sulfate, lithium difluorophosphate, difluorobis [oxalate-O, O ′] lithium phosphate (LiPFO), lithium tetrafluoro [oxalate-O, O ′] lithium phosphate, bis [ Oxare DOO -O, O '] lithium borate (LiBOB), and it is more preferable to use at least one selected from lithium methyl sulfate.

The type of (h) nitrile compound is not particularly limited as long as it is a compound having a “nitrile group”. Specifically, at least one selected from the group consisting of acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, and sebacononitrile is preferable, and two or more are more preferable. is there.
Among the nitrile compounds, one or more selected from succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile are more preferable.

(I) The type of benzene compound is not particularly limited as long as it is a compound having a “phenyl group” in the molecule. Specific examples thereof include aromatic compounds having a branched alkyl group such as cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, biphenyl, terphenyl (o-, m-, p-isomer), diphenyl ether, anisole. , Terphenyl hydrides (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), and phenyl carbonate compounds such as methylphenyl carbonate or ethylphenyl carbonate One or more selected from the above are preferably mentioned, and two or more are more preferable.
Among the benzene compounds, one or two selected from cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, biphenyl, terphenyl (o-, m-, p-form), methylphenyl carbonate, and ethylphenyl carbonate The above is more preferable, and at least one selected from cyclohexylbenzene, tert-amylbenzene, biphenyl, o-terphenyl, methylphenyl carbonate, and ethylphenyl carbonate is particularly preferable.

(J) The type of cyclic acetal compound is not particularly limited as long as it is a compound having an “acetal group” in the molecule. Specifically, one or more selected from the group consisting of 1,3-dioxolane, 1,3-dioxane, 1,3,5-trioxane and the like are preferable, and two or more are more preferable. .
Among the cyclic acetal compounds, 1,3-dioxolane or 1,3-dioxane is preferable, and 1,3-dioxane is more preferable.

The type of (k) phosphazene compound is not particularly limited as long as it is a compound having “N═PN group” in the molecule. Specific examples thereof include one or more selected from the group consisting of methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, ethoxyheptafluorocyclotetraphosphazene, and the like. Two or more types are more preferable.
Among the phosphazene compounds, cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, or phenoxypentafluorocyclotriphosphazene are preferable, and are selected from methoxypentafluorocyclotriphosphazene and ethoxypentafluorocyclotriphosphazene. One or more are more preferable.

(A) SO ₂ group-containing compound, (b) fluorinated benzene compound, (c) phosphate ester compound, (d) carbon-carbon triple bond-containing compound, (e) carboxylic acid anhydride, (f) isocyanate compound , (G) lithium-containing ionic compound, (h) nitrile compound, (i) benzene compound, (j) cyclic acetal compound, or (k) phosphazene compound content is 0.001 in the non-aqueous electrolyte, respectively. -5 mass% is preferable. In this range, the film is sufficiently formed without becoming too thick, and not only the effect of improving the electrochemical characteristics in a wide temperature range, particularly at a high temperature, but also the increase rate of the electrode thickness can be further reduced. The content is more preferably 0.01% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 3.5% by mass or less, and 2.5% by mass. The following is more preferable.

Moreover, it is preferable to use together 2 or more types of compounds used in combination with the said general formula (I). Among the combinations, (g) a lithium-containing ionic compound, (a) a SO ₂ group-containing compound, (b) a fluorinated benzene compound, (c) a phosphate ester compound, (d) a carbon-carbon triple bond-containing compound , (E) carboxylic acid anhydride, (f) isocyanate compound, (h) nitrile compound, (i) benzene compound, (j) cyclic acetal compound, and (k) phosphazene compound. (G) a lithium-containing ionic compound, (a) a SO ₂ group-containing compound, (b) a fluorinated benzene compound, (c) a phosphate ester compound, (d) a carbon-carbon triple bond-containing compound, It is more preferable to use at least one selected from the group consisting of (f) an isocyanate compound, (h) a nitrile compound, and (i) a benzene compound.

<First invention and second invention>
(Electrolyte salt)
Preferred examples of the electrolyte salt used in the present invention include the following lithium salts.
Examples of lithium salts include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , 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 , lithium salts containing a chain-like fluorinated alkyl group such as LiPF ₅ (iso-C ₃ F ₇ ), (CF ₂ ) ₂ (SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ Preferred examples include lithium salts having a cyclic fluorinated alkylene chain such as NLi, and preferred examples include at least one lithium salt selected from these, and one or two of these It can be used as a mixture of the above.
Among these, one 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. And LiPF ₆ is most preferred.

  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, particularly preferably 1.2 M or more, and 1.3 M with respect to the non-aqueous solvent. The above is most preferable. The upper limit is preferably 2.5M or less, more preferably 2.0M or less, and still more preferably 1.6M or less. When the compound represented by the general formula (I) or (II) of the present invention is used at this concentration, the movement of lithium in the SEI film becomes smoother, and uniform charge / discharge can be achieved throughout the electrode. This is because decomposition of the electrolytic solution is suppressed, so that the effect of improving electrochemical characteristics in a wide temperature range is remarkably increased, or the effect of reducing the increase rate of the electrode thickness is remarkably enhanced.

As the preferred combination of these electrolyte salts include LiPF _6, further _{LiBF 4, LiN (SO 2 F} ) 2 _{[LiFSI], LiN (SO 2 CF 3)} 2, and LiN _{(SO 2 C} 2 F ₅ ) It is preferable that at least one lithium salt selected from ₂ is contained in the non-aqueous electrolyte, and 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 easily exhibited, or the effect of improving the electrochemical characteristics at a high temperature is easily exhibited, and the effect of improving the electrochemical characteristics in a wide temperature range is 1.0 M or less. This is preferable because there is little concern that the degradation of the electrochemical characteristics will decrease, or there is little concern that the effect of improving the electrochemical properties at high temperatures will be reduced. Preferably it is 0.01M or more, More preferably, it is 0.03M or more, More preferably, it is 0.04M or more. The upper limit is preferably 0.8M or less, more preferably 0.6M or less, still more preferably 0.5M or less, and particularly preferably 0.4M or less.

When LiPF ₆ is included in the non-aqueous electrolyte of the second invention, the ratio of the molar concentration of the asymmetric halogenated phenyl carbonate compound represented by the general formula (II) to LiPF ₆ is 0.0005 or more at a high temperature. The effect of improving the electrochemical characteristics is easily exhibited, and it is preferably 0.3 or less because there is little fear that the effect of improving the electrochemical characteristics at high temperature is reduced. The lower limit is more preferably 0.001 or more, and still more preferably 0.005 or more. Moreover, the upper limit is more preferably 0.2 or less, and still more preferably 0.1 or less.

[Production of non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention is, for example, mixed with the non-aqueous solvent, and the biphenyl compound represented by the general formula (I) with respect to the electrolyte salt and the non-aqueous electrolyte. It can be obtained by adding an asymmetric halogenated phenyl carbonate compound represented by the formula (II).
At this time, it is preferable that the compound added to the non-aqueous solvent and the non-aqueous electrolyte to be used is one that is purified in advance and has as few impurities as possible within a range that does not significantly reduce the productivity.

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

[First power storage device (lithium battery)]
The lithium battery as the first power storage device is a general 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 secondary battery of the present invention comprises the nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a nonaqueous solvent. Components other than the non-aqueous electrolyte, such as a positive electrode and a 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 lithium composite 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 Mn _0.3 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, Fe), and LiNi _1/2 Mn _3/2 O 1 or more is preferably used selected from ₄ 2 or more 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 composite metal oxide that operates at a high charge voltage is used, the electrochemical characteristics of the lithium secondary battery according to the present invention are likely to deteriorate over a wide temperature range due to reaction with the electrolyte during charging. The deterioration of characteristics can be suppressed.
In particular, in the case of a positive electrode active material containing Ni, the nonaqueous solvent is decomposed on the surface of the positive electrode due to the catalytic action of Ni, and the resistance of the battery tends to increase. In particular, the electrochemical characteristics in a high-temperature environment tend to be deteriorated. However, the lithium secondary battery according to the present invention is preferable because it can suppress the deterioration of these electrochemical characteristics. In particular, when the positive electrode active material in which the ratio of the atomic concentration of Ni to the atomic concentration of all transition metal elements in the positive electrode active material exceeds 30 atomic% is used, the above effect becomes significant, and more preferably 50 atomic% or more. 75% or more is particularly preferable. Specifically, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 Mn _0.3 O ₂ , LiNi _0.8 Mn _0.1 Co _0. Preferable examples include ₁ O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ .

In addition, in order to improve safety and cycle characteristics during overcharge, or to enable use at a charging potential of 4.3 V or higher, a part of the lithium composite metal oxide may be substituted with another element. . For example, a part of cobalt, manganese, nickel is replaced with at least one element such as Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, La, etc. , A part of O may be substituted with S or F, or a compound containing these other elements may be coated.
Among these, when a positive electrode containing Ni is used to increase the capacity, particularly when the charge potential of the positive electrode in a fully charged state is charged to 4.3 V or more on the basis of Li, elution of Ni ions from the positive electrode occurs. The decomposition of the electrolytic solution on the negative electrode is promoted by the catalytic effect of Ni deposited on the negative electrode, and electrochemical characteristics such as high-temperature cycle characteristics are lowered, and the thickness of the negative electrode is easily increased. However, an electricity storage device using the non-aqueous electrolyte of the present invention is preferable because it can suppress a decrease in these electrochemical characteristics and an increase in electrode thickness.

Furthermore, lithium-containing olivine-type phosphate can also be used as the positive electrode active material. In particular, a lithium-containing olivine-type phosphate containing at least one 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). . Among these, LiFePO ₄ or _{LiFe 1-x Mn x PO 4} (0.1 <x <0.9) are more preferable, LiFePO ₄ is more preferred.
Some of these lithium-containing olivine-type phosphates may be substituted with other elements, and some of iron, cobalt, nickel, and manganese are replaced with Co, Mn, Ni, Mg, Al, B, Ti, V, and Nb. , Cu, Zn, Mo, Ca, Sr, W and Zr can be substituted with one or more elements selected from these, or can be coated with a compound or carbon material containing these other elements. Among these, LiFePO ₄ or LiMnPO ₄ is preferable.
Moreover, lithium containing olivine type | mold phosphate can also be mixed with the said positive electrode active material, for example, and can be used.
Lithium-containing olivine-type phosphate forms a stable phosphate skeleton (PO ₄ ) structure and has excellent thermal stability during charging, thus improving electrochemical characteristics over a wide temperature range, and after high-temperature cycling The increasing rate of the electrode thickness can be further reduced.

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 and other oxides or chalcogen compounds of one or more metal elements, SO ₂ , SOCl _2, etc. Examples thereof include sulfur compounds, and fluorocarbons (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.

When the pH of the supernatant liquid when 10.0 g of the positive electrode active material is dispersed in 100 ml of distilled water is 10.0 to 12.5, the effect of improving the electrochemical characteristics in a wider temperature range can be easily obtained. The case of 10.9 to 12.0 is more preferable.
In addition, when Ni is contained as an element in the positive electrode, in addition to elution of Ni ions from the positive electrode, impurities such as LiOH in the positive electrode active material tend to increase. Therefore, the electricity storage using the non-aqueous electrolyte of the present invention The device is preferable because it is easy to obtain an effect of improving electrochemical characteristics in a wider temperature range and an effect of suppressing an increase in electrode thickness. The case where the atomic concentration of Ni in the positive electrode active material is 5 to 25 atomic% is more preferable, and the case where it is 11 to 21 atomic% is particularly 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 graphite such as natural graphite (flaky graphite etc.) and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black. Further, graphite and carbon black may be appropriately mixed and used. 1-10 mass% is preferable and, as for the addition amount to the positive mix of a electrically conductive agent, 2-5 mass% is more preferable.

For the positive electrode, the positive electrode active material is made of a conductive agent such as acetylene black or carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), acrylonitrile and butadiene. Mixing with a binder such as copolymer (NBR), carboxymethyl cellulose (CMC), ethylene propylene diene terpolymer, etc., and adding a high boiling point solvent such as 1-methyl-2-pyrrolidone to knead and mix Then, this positive electrode mixture was applied to a current collector aluminum foil, a stainless steel lath plate, etc., dried and pressure-molded, and then vacuumed at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. It can be manufactured by heat treatment.
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 It is above, More preferably, it is 3.6 g / cm ³ or more. The upper limit is preferably 4 g / cm ³ or less.

Examples of the negative electrode active material for a lithium secondary battery include lithium metal, lithium alloy, and carbon material capable of occluding and releasing lithium (e.g., graphitizable carbon and (002) plane spacing of 0.37 nm (nanometer). ) The above non-graphitizable carbon, graphite having a (002) plane spacing of 0.34 nm or less], tin (single), tin compound, silicon (single), silicon compound, Li ₄ Ti ₅ O _12, etc. A lithium titanate compound etc. can be used individually by 1 type or in combination of 2 or more types. Particularly preferred combinations are graphite and silicon, or graphite and silicon compound.
Among these, it is more preferable to use a highly crystalline carbon material such as artificial graphite or natural graphite in terms of the ability to occlude and release lithium ions, and the lattice spacing (d ₀₀₂ ) of the lattice plane ( ₀₀₂ ) is 0. It is particularly preferable to use a carbon material having a graphite type crystal structure of 340 nm or less, particularly 0.335 to 0.337 nm.

Artificial graphite particles having a massive structure in which a plurality of flat graphite fine particles are assembled or bonded non-parallel to each other, for example, scaly natural graphite particles are repeatedly given mechanical action such as compression force, friction force, shear force, Using graphite particles that have been subjected to spheroidization treatment, the density of the portion excluding the current collector of the negative electrode can be obtained from the X-ray diffraction measurement of the negative electrode sheet when pressure-molded to a density of 1.5 g / cm ³ or more. When the ratio I (110) / I (004) of the peak intensity I (110) of the (110) plane of the graphite crystal to the peak intensity I (004) of the (004) plane is 0.01 or more, the graphite crystal It is preferable because the metal elution amount is improved and the charge storage characteristics are improved, more preferably 0.05 or more, and still more preferably 0.1 or more. Moreover, since it may process too much and crystallinity may fall and the discharge capacity of a battery may fall, 0.5 or less is preferable and 0.3 or less is more preferable.
In addition, it is preferable that the highly crystalline carbon material (core material) is coated with a carbon material having lower crystallinity than the core material because electrochemical characteristics in a wide temperature range are further improved. The crystallinity of the carbon material of the coating can be confirmed by TEM.
When a highly crystalline carbon material is used, it reacts with the non-aqueous electrolyte during charging and tends to lower the electrochemical properties at low or high temperatures due to an increase in interfacial resistance, but in the lithium secondary battery according to the present invention, Excellent electrochemical characteristics over a wide temperature range.

  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, and Cu. , Zn, Ag, Mg, Sr, Ba, and other compounds containing at least one metal element. 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 the capacity can be increased. 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 the capacity of the battery can be increased. A particularly preferable metal compound is an oxide containing silicon, which is represented by SiOx (0 <x <2).

  When the negative electrode active material is used in combination with graphite and silicon, or graphite and a silicon compound, the lithium secondary content according to the present invention is such that the content of silicon and silicon compound in the total negative electrode active material is 1 to 45% by mass. It is preferable because the capacity can be increased while suppressing the decrease in the electrochemical characteristics of the battery and the increase in the electrode thickness. The content of silicon and silicon compounds in all negative electrode active materials is more preferably 2 to 15% by mass.

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

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

The structure of the lithium battery is not particularly limited, and a coin-type battery, a cylindrical battery, a square battery, a laminated battery, or the like having a single-layer or multi-layer separator can be applied.
Although it does not restrict | limit especially as a battery separator, The single layer or laminated | stacked microporous film, woven fabric, a nonwoven fabric, etc. of polyolefin, such as a polypropylene, polyethylene, an ethylene propylene copolymer, can be used.
The polyolefin laminate is preferably a laminate of polyethylene and polypropylene, more preferably a three-layer structure of polypropylene / polyethylene / polypropylene.
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 the upper limit is 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less.

  It is preferable to provide a heat-resistant layer made of inorganic particles and / or organic particles and a binder on one or both sides of the separator. The thickness of the heat-resistant layer is preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 1.5 μm or more, and the upper limit thereof is 7 μm or less, preferably 6 μm or less, more preferably 5 μm or less. .

As the inorganic particles contained in the heat-resistant layer, oxides or hydroxides containing an element selected from Al, Si, Ti, and Zr are preferably exemplified.
Specific examples of the inorganic particles include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), oxides such as BaTiO ₃ , and boehmite (Al ₂ O _3. one or more selected from 3H 2 _O) hydroxide and the like. Among these, at least one selected from silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), BaTiO ₃ , and boehmite (Al ₂ O ₃ .3H ₂ O) is preferable. SiO ₂ ), alumina (Al ₂ O ₃ ), BaTiO ₃ , or boehmite (Al ₂ O ₃ .3H ₂ O) is more preferable, and alumina (Al ₂ O ₃ ), BaTiO ₃ , or boehmite (Al ₂ O _3. 3H ₂ O) is more preferred.
Examples of the organic particles contained in the heat-resistant layer include one or more selected from polymer particles such as polyamide, aramid, and polyimide. Among these, at least one selected from polyamide, aramid, and polyimide is preferable, and polyamide or aramid is more preferable.

  Examples of the binder included in the heat-resistant layer include ethylene-acrylic acid copolymers such as ethylene-vinyl acetate copolymer (EVA) and ethylene-ethyl acrylate copolymer, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride. (PVDF), fluorinated rubber, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), poly N-vinyl One type or two or more types selected from acetamide, a cross-linked acrylic resin, a polyurethane, and an epoxy resin are included. Among these, ethylene-acrylic acid copolymer such as ethylene-ethyl acrylate copolymer, polyvinylpyrrolidone (PVP), poly N-vinylacetamide, polyvinylidene fluoride (PVDF), styrene and butadiene copolymer (SBR) And one or more selected from carboxymethylcellulose (CMC) are preferred.

  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 more, particularly 4.3 V or more, and the characteristics are also good at 4.4 V or more. is there. The end-of-discharge voltage is usually 2.8 V or more, and further 2.5 V or more, but the lithium secondary battery in the present invention can be 2.0 V or more. Although it does not specifically limit about an electric current value, Usually, it uses in the range of 0.1-30C. Moreover, the lithium battery in this invention can be charged / discharged at -40-100 degreeC, Preferably it is -10-80 degreeC.

  In the present invention, as a countermeasure against an increase in the internal pressure of the lithium battery, a method of providing a safety valve on the battery lid or cutting a member such as a battery can or a gasket can be employed. Further, as a safety measure for preventing overcharge, the battery lid can be provided with a current interruption mechanism that senses the internal pressure of the battery and interrupts the current.

[Second power storage device (electric double layer capacitor)]
The 2nd electrical storage device of this invention is an electrical storage device which stores the energy using the electric double layer capacity | capacitance of electrolyte solution and an electrode interface including the non-aqueous electrolyte of this invention. An example of the present invention is an electric double layer capacitor. The most typical electrode active material used for this electricity storage device is activated carbon. Double layer capacity increases roughly in proportion to surface area.

[Third power storage device]
The 3rd electrical storage device of this invention is an electrical storage device which stores the energy using the dope / dedope reaction of an electrode including the non-aqueous electrolyte of this invention. Examples of the electrode active material used in this power 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 storage device (lithium ion capacitor)]
The 4th electrical storage device of this invention is an electrical storage device which stores the energy using the intercalation of lithium ion to carbon materials, such as a graphite which is a negative electrode, containing the non-aqueous electrolyte of this invention. It is called a lithium ion capacitor (LIC). Examples of the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, and those using a π-conjugated polymer electrode doping / dedoping reaction. The electrolyte contains at least a lithium salt such as LiPF ₆ .

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

<First invention>
Examples I-1 to I-22, Comparative Examples I-1 to I-2
[Production of lithium ion secondary battery]
94% by mass of LiNi _0.8 Co _0.15 Al _0.05 O _{2 and} 3% by mass of acetylene black (conductive agent) are mixed, and 3% by mass of polyvinylidene fluoride (binder) is previously added to 1-methyl-2- A positive electrode mixture paste was prepared by adding to and mixing with the solution dissolved in pyrrolidone. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried and pressurized, punched out to a predetermined size, and a positive electrode sheet was produced. The density of the portion excluding the current collector of the positive electrode was 3.6 g / cm ³ . Further, 10% by mass of silicon (simple substance), 85% by mass of artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material), and 5% by mass of polyvinylidene fluoride (binder) in advance are added to 1-methyl-2-pyrrolidone. A negative electrode mixture paste was prepared by adding to the dissolved solution and mixing. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried and pressed to obtain a negative electrode sheet that was punched into a predetermined size. The density of the portion excluding the current collector of the negative electrode was 1.5 g / cm ³ . 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. And it laminated | stacked in order of the positive electrode sheet, the separator made from a microporous polyethylene film, and the negative electrode sheet, and added the non-aqueous electrolyte of the composition of Tables 1-3, and produced the 2032 type coin battery.

[Evaluation of low temperature output characteristics after storage at high temperature]
<Initial discharge capacity>
Using the coin battery produced by the above method, in a constant temperature bath at 25 ° C., it was charged with a constant current and a constant voltage of 0.2 C for 7 hours to a final voltage of 4.2 V, and a final voltage under a constant current of 0.2 C. The initial discharge capacity was determined by discharging to 2.5V.
<Capacity recovery rate in high-temperature charge storage test>
Next, this coin battery was charged in a constant temperature bath at 80 ° C. with a constant current and constant voltage of 0.2 C for 7 hours to a final voltage of 4.2 V, and stored in an open circuit state for 3 days. Then, it put into the thermostat of 25 degreeC, and discharged once to the final voltage 2.5V under the constant current of 1C.
Subsequently, in a constant temperature bath at 25 ° C., the battery is charged and stored by charging to a final voltage of 4.2 V for 7 hours at a constant current and constant voltage of 0.2 C and discharging to a final voltage of 2.5 V under a constant current of 0.2 C. The later recovery discharge capacity was determined. The capacity recovery rate after high-temperature charge storage was determined by the following formula.
Capacity recovery rate (%) = (recovery discharge capacity / initial discharge capacity) × 100
<Low-temperature discharge capacity maintenance rate after high-temperature charge storage>
Thereafter, the coin battery was charged in a constant temperature bath at 25 ° C. with a constant current and a constant voltage of 0.2 C to a final voltage of 4.2 V for 7 hours. Then, it put into the -20 degreeC thermostat, and discharge capacity was calculated | required by discharging to the final voltage 2.5V under 5 C constant current. The low-temperature discharge capacity retention rate after high-temperature storage was determined by the following formula.
Low temperature discharge capacity retention rate after high temperature storage (%) = (discharge capacity at −20 ° C. after high temperature storage / initial discharge capacity) × 100
The production conditions and battery characteristics of the battery are shown in Tables 1-3.

Comparative Example I-3
Li metal was used for the positive electrode and negative electrode used in Example I-1, and the same nonaqueous electrolyte was used as in Example I-1, except that the amount of 4-phenylphenyl diethyl phosphate added was 0.3% by mass. A coin battery was manufactured. As described in Non-Patent Document 1, the potential of the positive electrode was swept to 4.65 V at a rate of 0.1 mV / sec in a constant temperature bath at 25 ° C. and held at that potential for 20 minutes. Thereafter, the voltage was lowered to 3.0 V at 0.1 mV / sec, the battery was once disassembled in the glove box, and the positive electrode was taken out. A coin battery was prepared in the same manner as in Comparative Example I-1 except that this extracted positive electrode was used. As a result of measuring the battery, the capacity recovery rate was 54%, and the low temperature discharge capacity retention rate after high temperature storage was 98%.

Example I-23, Comparative Example I-4
In place of the negative electrode active material used in Example I-1, a negative electrode sheet was prepared using lithium titanate Li ₄ Ti ₅ O ₁₂ (negative electrode active material). 90% by mass of lithium titanate Li ₄ Ti ₅ O _{12 and 5} % by mass of acetylene black (conductive material) are mixed, and 5% by mass of polyvinylidene fluoride (binder) is dissolved in 1-methyl-2-pyrrolidone in advance. A negative electrode mixture paste was prepared by adding to and mixing with the placed solution. This negative electrode mixture paste was applied on an aluminum foil (current collector), dried, pressed and punched to a predetermined size to produce a negative electrode sheet, and the charge end voltage during battery evaluation was 2 A coin battery was manufactured and evaluated in the same manner as in Example I-1 except that the voltage was 0.7 V and the discharge end voltage was 2.0 V. The results are shown in Table 4.

Example I-24, Comparative Example I-5
A positive electrode sheet was prepared using LiFePO ₄ (positive electrode active material) coated with amorphous carbon instead of the positive electrode active material used in Example I-1. 90% by mass of LiFePO ₄ coated with amorphous carbon and 5% by mass of acetylene black (conductive agent) are mixed, and 5% by mass of polyvinylidene fluoride (binder) is dissolved in 1-methyl-2-pyrrolidone in advance. The positive electrode mixture paste was prepared by adding to and mixing with the previously-prepared solution. This positive electrode mixture paste was applied onto an aluminum foil (current collector), dried and pressurized, punched out to a predetermined size, and a positive electrode sheet was produced. A coin battery was fabricated and evaluated in the same manner as in Example I-1, except that the voltage was 6 V and the discharge end voltage was 2.0 V. The results are shown in Table 5.

In any of the lithium secondary batteries of Examples I-1 to I-22 described above, Comparative Example I-1 in which the biphenyl compound containing a phosphate ester structure is not added in the nonaqueous electrolytic solution of the first invention, Patent Document 1 The capacity recovery rate after high temperature storage and the low temperature discharge capacity maintenance rate are remarkably improved as compared with the non-aqueous electrolyte lithium secondary battery to which the phosphate compound used in the method described in 1 is added. As mentioned above, the effect of 1st invention is peculiar when 0.1-4.5 mass% of specific compounds of 1st invention are contained in the non-aqueous electrolyte in which electrolyte salt is dissolved in the non-aqueous solvent. It turned out to be an effect.
Further, from comparison between Example I-23 and Comparative Example I-3 and Comparative Example I-4, and comparison between Example I-24 and Comparative Example I-5, Li metal and lithium titanate Li ₄ Ti ₅ were used for the negative electrode. The same effect is observed when O ₁₂ (negative electrode active material) is used or when LiFePO ₄ (positive electrode active material) coated with amorphous carbon is used for the positive electrode. Therefore, it is clear that the effect of the present invention is not an effect dependent on a specific positive electrode or negative electrode.
Furthermore, the non-aqueous electrolyte of the first invention also has an effect of improving discharge characteristics in a wide temperature range such as a lithium primary battery, a lithium ion capacitor, and a lithium air battery.

<Second invention>
Examples II-1 to II-25, Comparative Examples II-1 to II-3
[Production of lithium ion secondary battery]
LiNi _0.5 Mn _0.3 Co _0.2 Mn _0.3 O ₂ (pH 11.1) 94% by mass and acetylene black (conductive agent) 3% by mass are mixed, and polyvinylidene fluoride (binder) in advance. A positive electrode mixture paste was prepared by adding and mixing 3% by mass with a solution dissolved in 1-methyl-2-pyrrolidone. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried and pressurized, and cut into a predetermined size to produce a belt-like positive electrode sheet. The density of the portion excluding the current collector of the positive electrode was 3.6 g / cm ³ .
In addition, 90% by mass of artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material) and 5% by mass of SiO (negative electrode active material) were added in advance to 5% by mass of polyvinylidene fluoride (binder). In addition to the solution dissolved in pyrrolidone, it mixed and the negative mix paste was prepared. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried and pressurized, and cut into a predetermined size to produce a negative electrode sheet. The density of the portion excluding the current collector of the negative electrode was 1.5 g / cm ³ . 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.
A heat-resistant layer (3 μm) having boehmite particles and an ethylene-vinyl acetate copolymer is formed on both sides of a laminated microporous film having a three-layer structure of polypropylene (3 μm) / polyethylene (5 μm) / polypropylene (3 μm). A separator having a thickness of 17 μm was produced.
The positive electrode sheet obtained above, a separator, and the negative electrode sheet obtained above were laminated in this order, and a non-aqueous electrolyte solution having the composition shown in Tables 1 to 5 was added to produce a laminate type battery.

[Evaluation of high-temperature cycle characteristics]
Using the battery produced by the above method, in a constant temperature bath at 50 ° C., charge at a constant current of 1 C and a constant voltage for 3 hours to a final voltage of 4.3 V (the positive electrode Li reference potential is 4.4 V). Discharging to a discharge voltage of 3.0 V under a constant current of 1 C was defined as one cycle, and this was repeated until 200 cycles were reached. And the discharge capacity maintenance factor after a cycle was calculated | required with the following formula | equation.
Discharge capacity retention ratio (%) = (discharge capacity at the 200th cycle / discharge capacity at the first cycle) × 100
<Initial anode thickness>
The battery cycled by the above method was disassembled and the initial negative electrode thickness was measured.
<Negative electrode thickness after high-temperature cycle>
The battery that had been subjected to 200 cycles by the above method was disassembled, and the negative electrode thickness after the high-temperature cycle was measured.
<Negative electrode thickness increase rate>
The negative electrode thickness increase value was determined by the following formula.
Negative electrode thickness increase value = negative electrode thickness after cycle−initial negative electrode thickness The negative electrode thickness increase rate (%) was determined based on the negative electrode thickness increase value of Comparative Example II-1 as 100%. The results are shown in Tables 6-9.

Example II-26 and Comparative Example II-4
Instead of the negative electrode active material used in Example II-3 and Comparative Example II-1, a negative electrode sheet was prepared using silicon (single element) (negative electrode active material). Silicon (simple substance) 40% by mass, artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material) 50% by mass, acetylene black (conductive agent) 5% by mass are mixed, and polyvinylidene fluoride (binder) 5 mass in advance. % Was added to the solution dissolved in 1-methyl-2-pyrrolidone and mixed to prepare a negative electrode mixture paste. Example II-3, except that this negative electrode mixture paste was applied to one side of a copper foil (current collector), dried, pressurized and cut into a predetermined size to produce a negative electrode sheet. A laminate-type battery was prepared in the same manner as in Comparative Example II-1, battery evaluation was performed, and the negative electrode thickness increase rate was determined based on the negative electrode thickness increase value of Comparative Example II-4 as 100%. The results are shown in Table 10.

Example II-27 and Comparative Example II-5
In place of the positive electrode active material used in Example II-3 and Comparative Example II-1, a positive electrode sheet was prepared using LiFePO ₄ (positive electrode active material) coated with amorphous carbon. 90% by mass of LiFePO ₄ coated with amorphous carbon and 5% by mass of acetylene black (conductive agent) are mixed, and 5% by mass of polyvinylidene fluoride (binder) is dissolved in 1-methyl-2-pyrrolidone in advance. The positive electrode mixture paste was prepared by adding to and mixing with the previously-prepared solution. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried, pressurized and cut into a predetermined size to produce a positive electrode sheet, and a charge end voltage for battery evaluation. A laminate type battery was prepared in the same manner as in Example II-3 and Comparative Example II-1, except that the discharge end voltage was set to 2.0 V and the discharge end voltage was set to 2.0 V. Was determined based on the negative electrode thickness increase value of Comparative Example II-5 as 100%. The results are shown in Table 11.

Any of the lithium secondary batteries of Examples II-1 to II-25 including the general formula (I) suppressed the increase in the thickness of the negative electrode after the high-temperature cycle as compared with Comparative Examples II-1 to II-3. Yes. As described above, the effect of reducing the increase rate of the electrode thickness of the second invention is unique to the case where the specific compound of the second invention is contained in the nonaqueous electrolytic solution in which the electrolyte salt is dissolved in the nonaqueous solvent. It turned out to be an effect.
Further, from the comparison between Example II-26 and Comparative Example II-4, and the comparison between Example II-27 and Comparative Example II-5, when silicon is used for the negative electrode or when LiFePO ₄ is used for the positive electrode, Similar effects are seen.
Furthermore, the nonaqueous electrolytic solution of the second invention also has an effect of improving the discharge characteristics in a wide temperature range of the lithium primary battery.

  If the nonaqueous electrolyte solution of the first invention is used, an electricity storage device having excellent electrochemical characteristics in a wide temperature range can be obtained. In particular, when used as a non-aqueous electrolyte for an electricity storage device mounted on a hybrid electric vehicle, a plug-in hybrid electric vehicle, a battery electric vehicle, etc., it is possible to obtain an electricity storage device capable of improving electrochemical characteristics in a wide temperature range. it can.

  By using the non-aqueous electrolyte solution of the second invention, it is possible to obtain an electricity storage device that is excellent in electrochemical characteristics in a wide temperature range, particularly at high temperatures, and further suppresses an increase in electrode thickness after a high temperature cycle. In particular, non-aqueous electrolytes for power storage devices such as lithium secondary batteries mounted on devices that are likely to be used at high temperatures such as hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, tablet terminals and ultrabooks When used as, it is possible to obtain an electricity storage device in which electrochemical characteristics are unlikely to deteriorate at a wide temperature range, particularly at high temperatures.

Claims (8)

A non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent includes an asymmetric halogenated phenyl carbonate compound represented by the following general formula (II), and the content of the halogenated phenyl carbonate compound is non-aqueous electrolysis The non-aqueous electrolyte for electrical storage devices characterized by being 0.001-5 mass% in a liquid.

^(Wherein, X 11 ^{to X 15} each independently represent a hydrogen atom or a halogen ^atom, one to 4 of X 11 ^{to X 15} is a halogen atom.) The nonaqueous electrolytic solution according to claim 1, wherein in general formula (II), one or two of X ^{11 to} X ¹⁵ are halogen atoms, and the rest are hydrogen atoms. In formula (II), X ¹¹ or X ¹⁵ ortho is a halogen atom, a non-aqueous electrolyte according to claim 1 or 2.   The nonaqueous electrolytic solution according to claim 1, wherein the halogen atom is a chlorine atom.   The compound represented by the general formula (II) is 2-fluorophenyl phenyl carbonate, 4-fluorophenyl phenyl carbonate, 2,4-difluorophenyl phenyl carbonate, 2,6-difluorophenyl phenyl carbonate, 2-chlorophenyl phenyl carbonate, The compound according to any one of claims 1 to 4, which is one or more selected from 3-chlorophenyl phenyl carbonate, 4-chlorophenyl phenyl carbonate, 2,4-dichlorophenyl phenyl carbonate, and 2,6-dichlorophenyl phenyl carbonate. The non-aqueous electrolyte described in 1.   The non-aqueous electrolyte further contains a symmetric phenyl carbonate compound, and the mass ratio of [asymmetric halogenated phenyl carbonate compound / symmetric phenyl carbonate compound] is 50/50 to 99.9 / 0.1. The nonaqueous electrolytic solution according to any one of the above.   The nonaqueous solvent according to any one of claims 1 to 6, wherein the nonaqueous solvent includes a cyclic carbonate and a chain carbonate, and the chain carbonate includes both a symmetric chain carbonate and an asymmetric chain carbonate. Electrolytic solution.   In the electrical storage device provided with the positive electrode, the negative electrode, and the nonaqueous electrolyte solution in which the electrolyte salt is dissolved in the nonaqueous solvent, the nonaqueous electrolyte solution is the nonaqueous electrolyte solution according to any one of claims 1 to 7. An electricity storage device characterized by being.