JP2016066404A - Nonaqueous electrolytic solution and power storage device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution which enables the enhancement of an electrochemical property in a wide temperature range; and a power storage device using such a nonaqueous electrolytic solution.SOLUTION: A nonaqueous electrolytic solution comprises: a nonaqueous solvent; an electrolyte salt dissolved in the nonaqueous solvent; and at least one lithium phosphate expressed by the general formula (I) in which a particular polar group (X) is directly coupled to a phosphorus atom (P). A power storage device comprises the nonaqueous electrolytic solution. (In the general formula (I), R is an organic group selected from a group consisting of an alkyl group with 1-8C, an alkenyl group with 2-6C, an alkynyl group with 3-6C and an aryl group with 6-12C, in which part of hydrogen atoms may be substituted with a halogen atom, or a lithium atom; and X is a polar group including a -C(=O) group, a -P(=O) group or a -S(=O)group.)SELECTED DRAWING: None

Description

  The present invention relates to a nonaqueous electrolytic solution capable of improving electrochemical characteristics in a wide temperature range and an electricity storage device using the same.

In recent years, power storage devices, particularly lithium secondary batteries, have been widely used for small electronic devices such as mobile phones and notebook computers, electric vehicles, and power storage. Since these electronic devices and automobiles may be used in a wide temperature range such as a high temperature in midsummer or a low temperature of extremely cold, it is required to improve electrochemical characteristics in a wide range of temperatures.
In particular, in order to prevent global warming, there is an urgent need to reduce CO ₂ emissions. Among environmentally friendly vehicles equipped with power storage devices consisting of power storage devices such as lithium secondary batteries and capacitors, hybrid electric vehicles ( HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV) are required to spread quickly. Due to the long travel distance of automobiles, automobiles may be used in areas with a wide temperature range from extremely hot areas in the tropics to extremely cold areas. Therefore, in particular, these in-vehicle power storage devices are required not to deteriorate in electrochemical characteristics even when used in a wide temperature range from high temperature to low temperature.
In the present specification, the term lithium secondary battery is used as a concept including so-called lithium ion secondary batteries.

The lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of occluding and releasing lithium, a non-aqueous 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.
In addition, as the negative electrode, metal lithium, metal compounds that can occlude and release lithium (metal simple substance, oxide, alloy with lithium, etc.) and carbon materials are known, and in particular, lithium can be occluded and released. Lithium secondary batteries using carbon materials such as coke, artificial graphite and natural graphite 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 a decomposition product generated by reductive decomposition of a solvent in a non-aqueous electrolyte on the negative electrode surface during charging. It has been found that the gas interferes with the desired electrochemical reaction of the battery, resulting in poor cycle characteristics. Moreover, if the decomposition product of the nonaqueous solvent accumulates, the insertion and extraction of lithium into the negative electrode cannot be performed smoothly, and the electrochemical characteristics when used in a wide temperature range are liable to deteriorate.
Furthermore, lithium secondary batteries using lithium metal, alloys thereof, simple metals such as tin or silicon, and oxides as negative electrode materials have high initial capacities, but fine powders progress during the cycle. In comparison, it is known that reductive decomposition of a non-aqueous solvent occurs at an accelerated rate, and battery performance such as battery capacity and cycle characteristics is greatly reduced. In addition, if these anode materials are pulverized or decomposition products of nonaqueous solvents accumulate, lithium cannot be smoothly stored and released, and the electrochemical characteristics when used in a wide temperature range are likely to deteriorate. .

On the other hand, a lithium secondary battery using, for example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO _4, or the like as the positive electrode includes a positive electrode material, a non-aqueous electrolyte, and a non-aqueous solvent in a non-aqueous electrolyte in a charged state. The degradation products and gas generated by partial oxidative decomposition at the interface of the battery hinder the desired electrochemical reaction of the battery, which also causes degradation of electrochemical characteristics when used in a wide temperature range. I know.

As described above, the battery performance has been deteriorated due to the movement of lithium ions or the expansion of the battery due to the decomposition product or gas when the non-aqueous electrolyte is decomposed on the positive electrode or the negative electrode. In spite of such a 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 volume occupied by non-aqueous electrolyte in the battery has become smaller, such as increasing the electrode density and reducing the useless space volume in the battery. . Therefore, there is a situation in which the electrochemical characteristics when used in a wide temperature range are likely to deteriorate with a slight decomposition of the non-aqueous electrolyte.
Patent Document 1 discloses that a nonaqueous electrolytic solution containing a phosphate ester compound such as triethylphosphonoacetate or triethylphosphonoformate as an additive can improve continuous charge characteristics and high-temperature storage characteristics and suppress gas generation. Is described.

International Publication No. 2008/123038 Pamphlet

  An object of the present invention is to provide a nonaqueous electrolytic solution capable of improving electrochemical characteristics in a wide temperature range and an electricity storage device using the same.

As a result of examining the performance of the above-described conventional non-aqueous electrolyte in detail, the non-aqueous electrolyte secondary battery of Patent Document 1 has a wide temperature range such as low-temperature discharge characteristics after high-temperature storage. The fact was that it was almost impossible to achieve the effect of improving the electrochemical characteristics.
Therefore, the present inventors have made extensive studies to solve the above problems, and in a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, phosphoric acid in which a specific polar group is directly bonded to a phosphorus atom. The inventors have found that the inclusion of one or more types of lithium can improve the electrochemical characteristics of the electricity storage device, particularly the electrochemical characteristics of the lithium battery, over a wide temperature range, thereby completing the present invention. Such an effect is not suggested at all in Patent Document 1.

  That is, the present invention provides the following (1) to (4).

(1) In a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, lithium phosphate in which a specific polar group (X) is directly bonded to the phosphorus atom (P) represented by the general formula (I) A non-aqueous electrolyte characterized by containing one or more.

（Ｒは炭素数１〜８のアルキル基、炭素数２〜６のアルケニル基、炭素数３〜６のアルキニル基、及び炭素数６〜１２のアリール基からなる群より選ばれる水素原子の一部がハロゲン原子で置換されていてもよい有機基またはリチウム原子であり、Ｘは−Ｃ（＝Ｏ）基、−Ｐ（＝Ｏ）基、または−Ｓ（＝Ｏ）_２基を含む極性基である。

(R is a part of a hydrogen atom selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 12 carbon atoms. Is an organic group optionally substituted with a halogen atom or a lithium atom, and X is a polar group containing a —C (═O) group, a —P (═O) group, or a —S (═O) ₂ group. is there.

(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 a phosphorus represented by the general formulas (II) to (IV). A power storage device comprising at least one selected from the group consisting of lithium phosphates in which a specific polar group is directly bonded to an atom (P).

（Ｒ^１及びＲ^２はそれぞれ独立にＲと同義である。）

(R ¹ and R ² are each independently synonymous with R.)

（Ｒ^１、Ｒ^３、及びＲ^４はそれぞれ独立にＲと同義である。）

(R ¹ , R ³ , and R ⁴ are each independently synonymous with R.)

（Ｒ^１及びＲ^５はそれぞれ独立にＲと同義である。）

(R ¹ and R ⁵ are each independently synonymous with R.)

(3) Lithium phosphate in which a specific polar group is directly bonded to the phosphorus atom (P) represented by the general formulas (V) to (VII).

（Ｒ^１１及びＲ^１２はそれぞれ独立にＲと同義である。ただし、Ｒ^１１及びＲ^１２の少なくとも１方は炭素数３〜６のアルキニル基である。）

(R ¹¹ and R ¹² are each independently synonymous with R. However, at least one of R ¹¹ and R ¹² is an alkynyl group having 3 to 6 carbon atoms.)

（Ｒ^１１、Ｒ^１３、及びＲ^１４はそれぞれ独立にＲと同義である。ただし、Ｒ^１１、Ｒ^１３、及びＲ^１４のすべてがリチウム原子の場合は除く。）

(R ¹¹ , R ¹³ , and R ¹⁴ are each independently synonymous with R, except when R ¹¹ , R ¹³ , and R ¹⁴ are all lithium atoms.)

（Ｒ^１１及びＲ^１５はそれぞれ独立にＲと同義である。）

(R ¹¹ and R ¹⁵ are each independently synonymous with R.)

(4) An additive for an electricity storage device comprising lithium phosphate in which a specific polar group is directly bonded to the phosphorus atom (P) represented by the general formulas (V) to (VII).

（Ｒ^１１及びＲ^１２はそれぞれ独立にＲと同義である。ただし、Ｒ^１１及びＲ^１２の少なくとも１方は炭素数３〜６のアルキニル基である。）

(R ¹¹ and R ¹² are each independently synonymous with R. However, at least one of R ¹¹ and R ¹² is an alkynyl group having 3 to 6 carbon atoms.)

（Ｒ^１１、Ｒ^１３、及びＲ^１４はそれぞれ独立にＲと同義である。ただし、Ｒ^１１、Ｒ^１３、及びＲ^１４のすべてがリチウム原子の場合は除く。）

(R ¹¹ , R ¹³ , and R ¹⁴ are each independently synonymous with R, except when R ¹¹ , R ¹³ , and R ¹⁴ are all lithium atoms.)

（Ｒ^１１及びＲ^１５はそれぞれ独立にＲと同義である。）

(R ¹¹ and R ¹⁵ are each independently synonymous with R.)

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous electrolyte which can improve the electrochemical characteristic of the electrical storage device in a wide temperature range, especially the low temperature discharge characteristic after high temperature storage, and electrical storage devices, such as a lithium battery using the same, can be provided. .

  The present invention relates to a non-aqueous electrolyte and an electricity storage device using the same.

[Non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention is a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent. The non-aqueous electrolyte is specific to the phosphorus atom (P) represented by the general formula (I) in the non-aqueous electrolyte. A non-aqueous electrolyte characterized by containing one or more types of lithium phosphate to which a polar group (X) is directly bonded.

The reason why the nonaqueous electrolytic solution of the present invention can greatly improve the electrochemical characteristics of the electricity storage device in a wide temperature range is not necessarily clear, but is considered as follows.
As described in the general formula (I), the lithium phosphate used in the present invention has a phosphorus atom (P), a -C (= O) group, a -P (= O) group, or -S (= O) A specific polar group (X) selected from _two groups is directly bonded. Therefore, a dense and highly heat-resistant film is formed on the positive electrode and the negative electrode, which is easily subjected to electrochemical decomposition. Moreover, since the lithium phosphate represented by the general formula (I) is literally a lithium salt, the coating film is excellent in lithium ion conductivity. Therefore, compared with triethylphosphonoacetate and triethylphosphonoformate described in Patent Document 1, it is considered that the electrochemical characteristics in a wide temperature range are remarkably improved.

  The lithium phosphate in which the specific polar group (X) is directly bonded to the phosphorus atom (P) contained in the nonaqueous electrolytic solution of the present invention is represented by the following general formula (I).

（Ｒは炭素数１〜８のアルキル基、炭素数２〜６のアルケニル基、炭素数３〜６のアルキニル基、及び炭素数６〜１２のアリール基からなる群より選ばれる水素原子の一部がハロゲン原子で置換されていてもよい有機基またはリチウム原子であり、Ｘは−Ｃ（＝Ｏ）基、−Ｐ（＝Ｏ）基、又は−Ｓ（＝Ｏ）_２基を含む極性基である。）

(R is a part of a hydrogen atom selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 12 carbon atoms. Is an organic group optionally substituted with a halogen atom or a lithium atom, and X is a polar group containing a —C (═O) group, a —P (═O) group, or a —S (═O) ₂ group. is there.)

  In the general formula (I), R is a group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 12 carbon atoms. A part of selected hydrogen atoms represents an organic group or lithium atom which may be substituted with a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 3 to 4 carbon atoms, or an alkynyl group having 3 to 6 carbon atoms An organic group or a lithium atom in which a part of hydrogen atoms selected from the group consisting of a group and an aryl group having 6 to 10 carbon atoms may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, and carbon An organic group in which part of the hydrogen atoms selected from the group consisting of alkynyl groups of 3 to 4 may be substituted with a halogen atom is more preferable.

  Specific examples in the case where R is an organic group in which a part of hydrogen atoms may be substituted with a halogen atom include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, Linear alkyl group such as n-hexyl group, n-heptyl group, or n-octyl group, branched chain alkyl group such as iso-propyl group, sec-butyl group, tert-butyl group, or tert-amyl group Group, cyclopropyl group, cyclobutyl group, cyclopentyl group, or cyclohexyl group such as cyclohexyl group, fluoromethyl group, difluoromethyl group, 2-chloroethyl group, 2-fluoroethyl group, 2,2-difluoroethyl group, 2, 2,2-trifluoroethyl group, 3-fluoropropyl group, 3-chloropropyl group, 3,3-difluoropropyl group, 3,3, -An alkyl group in which a part of hydrogen atoms such as trifluoropropyl group, 2,2,3,3-tetrafluoropropyl group, or 2,2,3,3,3-pentafluoropropyl group is substituted with a halogen atom A linear alkenyl group such as vinyl group, 1-propenyl group, 2-propenyl group, 2-butenyl group, 3-butenyl group, 4-pentenyl group, or 5-hexen-1-yl group, 1-propene- Branched alkenyl groups such as 2-yl group, 1-buten-2-yl group, or 2-methyl-2-propen-1-yl group, 3,3-difluoro-2-propen-1-yl group, 4 , 4-difluoro-3-buten-1-yl group, 3,3-dichloro-2-propen-1-yl group, or 4,4-dichloro-3-buten-1-yl group Part is a halogen atom Linear alkynyl group such as substituted alkenyl group, 2-propynyl group, 2-butynyl group, 3-butynyl group or 4-heptynyl group, 1-methyl-2-propynyl group, 1,1-dimethyl-2 -Branched alkynyl group such as propynyl group, 1-methyl-3-butynyl group, or 1-methyl-4-heptynyl group, phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, An aryl group such as 2,4-di-tert-butylphenyl group or 4-tert-butylphenyl group, or 2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 2-trifluoromethyl Phenyl group, 3-trifluoromethylphenyl group, 4-trifluoromethylphenyl group, 4-fluoro-2-trifluoromethylphenyl group Group, 4-fluoro-3-trifluoromethylphenyl group, 2,4-difluorophenyl group, 2,6-difluorophenyl group, 3,5-difluorophenyl group, 2,4,6-trifluorophenyl group, Preferable examples include aryl groups in which a part of hydrogen atoms such as 2,3,5,6-tetrafluorophenyl group or perfluorophenyl group are substituted with halogen atoms. Among them, methyl group, ethyl group, n- Propyl group, n-butyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, 2-propenyl group or 2-propynyl group are preferred, methyl group, ethyl group, 2,2, A 2-trifluoroethyl group or a 2-propynyl group is more preferable.

  The lithium phosphate represented by the general formula (I) is lithium phosphate in which a specific polar group is directly bonded to the phosphorus atom (P) represented by the following general formulas (II) to (IV).

（Ｒ^１及びＲ^２はそれぞれ独立にＲと同義である。）

(R ¹ and R ² are each independently synonymous with R.)

（Ｒ^１、Ｒ^３、及びＲ^４はそれぞれ独立にＲと同義である。）

(R ¹ , R ³ , and R ⁴ are each independently synonymous with R.)

（Ｒ^１及びＲ^５はそれぞれ独立にＲと同義である。）

(R ¹ and R ⁵ are each independently synonymous with R.)

  Of the lithium phosphates represented by the general formulas (II) to (IV), the general formula (II) or (III) is more preferable, and the general formula (II) is more preferable.

In the general formula (II), R ¹ and R ² are each independently synonymous with R, and at least one of R ¹ and R ² may be an organic group in which a part of hydrogen atoms may be substituted with a halogen atom. It is preferably a group, and more preferably both are organic groups in which a part of hydrogen atoms may be substituted with a halogen atom.

Specific examples and preferred ranges in the case where R ¹ and R ² are organic groups in which a part of hydrogen atoms may be substituted with halogen atoms are the same as the preferred ranges of R, and among R ¹ and R ² More preferably, at least one is an alkynyl group having 3 to 4 carbon atoms.

In the general formula (III), R ¹ , R ³ , and R ⁴ are each independently synonymous with R, and at least one of R ¹ , R ³ , and R ⁴ is a halogen atom part of which is a halogen atom It is preferably an organic group which may be substituted, more preferably at least two are organic groups in which some of the hydrogen atoms may be substituted with halogen atoms, and all of the hydrogen atoms are partially halogenated. More preferably, it is an organic group which may be substituted with an atom.

Specific examples and preferred ranges in which R ¹ , R ³ , and R ⁴ are organic groups in which part of the hydrogen atoms may be substituted with halogen atoms are the same as the preferred ranges of R, R ¹ , More preferably, at least one of R ³ and R ⁴ is an alkynyl group having 3 to 4 carbon atoms.

In the general formula (IV), R ¹ and R ⁵ are each independently synonymous with R, and at least one of R ¹ and R ⁵ may be an organic group in which a part of hydrogen atoms may be substituted with a halogen atom. It is preferable that both are organic groups in which a part of hydrogen atoms may be substituted with a halogen atom.

Specific examples and preferred ranges in the case where R ¹ and R ⁵ are organic groups in which a part of hydrogen atoms may be substituted with halogen atoms are the same as the preferred ranges of R, and among R ¹ and R ⁵ More preferably, at least one is an alkynyl group having 3 to 4 carbon atoms.

  Specific examples of the lithium phosphate in which a specific polar group is directly bonded to the phosphorus atom (P) represented by the general formulas (II) to (IV) include the following compounds.

[Compound of general formula (II)]

[Compound of general formula (III)]

[Compound of general formula (IV)]

が好適に挙げられる。

Are preferable.

  Among the above preferred examples, compounds A1 to A16, A20 to A35, A40 to A49, A51, A57 to A61, A63 to A85, A87 to A89, B1 to B3, B9 to B13, B17 to B21, C1 to C3, or C6 To C9, and compounds A1 to A4, A8, A20 to A21, A23 to A29, A33 to A35, A43 to A45, A51, A57, A60 to A61, A63 to A67, A77 to A80, A82, A84 to A85, A89, B1-B3, B9-B11, B17-B18, B20-B21, C1-C2, or C7 are more preferable, and lithium methyl methoxycarbonylphosphonate (compound A1), lithium ethyl methoxycarbonylphosphonate (compound A2), lithium butyl Methoxycarbonylphosphonate (Compound A ), Lithium butyl ethoxycarbonylphosphonate (compound A8), lithium 2-propenyl methoxycarbonylphosphonate (compound A20), lithium 2-propynyl methoxycarbonylphosphonate (compound 21), lithium 3-butyn-2-yl methoxycarbonylphosphonate (compound 23) ), Lithium 2-methyl-3-butyn-2-yl methoxycarbonylphosphonate (compound 24), lithium phenyl methoxycarbonylphosphonate (compound A25), lithium 2,4-di-tert-butylphenyl methoxycarbonylphosphonate (compound A28) , Lithium ethyl ethoxycarbonylphosphonate (compound A33), lithium ethyl butoxycarbonylphosphonate (compound A35) Lithium ethyl 2,2-difluoroethoxycarbonylphosphonate (Compound A44), lithium ethyl 2,2,2-trifluoroethoxycarbonylphosphonate (Compound A45), lithium ethyl 2-propenyloxycarbonylphosphonate (Compound A51), lithium ethyl 2- Propynyloxycarbonylphosphonate (compound A57), lithium ethyl 3-butyn-2-yloxycarbonylphosphonate (compound A60), lithium ethyl 2-methyl-3-butyn-2-yloxycarbonylphosphonate (compound A61), lithium ethyl phenyl Oxycarbonylphosphonate (compound A63), lithium ethyl 4-tert-butylphenyloxycarbonylphosphonate (compound A66), lithium Umphenyl 4-tert-butylphenyloxycarbonylphosphonate (compound A77), dilithium methoxycarbonylphosphonate (compound A78), dilithium ethoxycarbonylphosphonate (compound A79), ethyl dilithium oxycarbonylphosphonate (compound A84), trilithium oxycarbonylphosphonate ( Compound A89), lithium trimethyl high positive phosphate (compound B1), lithium triethyl high positive phosphate (compound B2), lithium tributyl high positive phosphate (compound B3), lithium tris (2-propenyl) high positive phosphate (compound B9), lithium tris (2- Propynyl) high positive phosphate (compound B10), lithium methyl methylsulfate Niruhosuhoneto (Compound C1), lithium ethyl methylsulfonyl phosphonate (Compound C2), or lithium ethyl 2-propyn-1-yl-sulfonyl phosphonate (Compound C7) is particularly preferred.

  In the non-aqueous electrolyte of the present invention, the content of lithium phosphate in which the specific polar group represented by the general formula (I) contained in the non-aqueous electrolyte is directly bonded to the phosphorus atom is the non-aqueous electrolyte. It is preferable that it is 0.001-10 mass% inside. If the content is 10% by mass or less, there is little possibility that a film is excessively formed on the electrode and the low-temperature characteristics are deteriorated, and if it is 0.001% by mass or more, the formation of the film is sufficient and a wide temperature range. The above range is preferable because the improvement effect of electrochemical characteristics in the range is enhanced. 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 5% by mass or less, and further preferably 3% by mass or less.

  In the non-aqueous electrolyte of the present invention, a non-aqueous solvent, an electrolyte salt, and other additives described below for lithium phosphate in which the specific polar group represented by the general formula (I) is directly bonded to a phosphorus atom When combined, it produces a unique effect that the electrochemical properties are synergistically improved over a wide temperature range.

[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 exemplified. In order to improve the electrochemical properties synergistically over a wide temperature range, it is preferable that a chain ester is included, more preferably a chain carbonate is included, and both a cyclic carbonate and a chain carbonate are included. preferable.

  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 two or more selected from ethylene carbonate, propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinylene carbonate and 4-ethynyl- Selected from 1,3-dioxolan-2-one (EEC) One or two or more is more preferable.

  Further, it is preferable to use at least one of unsaturated carbonates 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. -It is more preferable that both a cyclic carbonate containing an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom 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.

  The content of the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is preferably 0.07% by volume or more, more preferably 0.8%, based on the total volume of the nonaqueous solvent. 2 vol% or more, more preferably 0.7 vol% or more, and the upper limit thereof is preferably 7 vol% or less, more preferably 4 vol% or less, further preferably 2.5 vol% or less. And, it is preferable because electrochemical characteristics in a wider temperature range can be further increased 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 further 15% by volume or less, which improves electrochemical characteristics in a wider temperature range without impairing Li ion permeability. This is particularly 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 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.

  These solvents may be used alone, and when used in combination of two or more, it is preferable because the effect of improving electrochemical characteristics over a wide temperature range is further improved, and used in combination of three or more. It is particularly preferable to do this. 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, 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 electrochemical characteristics in a wide temperature range. The above range is preferable because there is little risk of 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. The above case is preferable because electrochemical characteristics in a wider temperature range are improved.

  The ratio between the cyclic carbonate and the chain ester is preferably 10:90 to 45:55, and 15:85 to 40:60, from the viewpoint of improving electrochemical properties at high temperatures. Is more preferable, and 20:80 to 35:65 is 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. As the combination, for example, a combination of a cyclic carbonate, a chain ester, and a lactone, or a combination of a cyclic carbonate, a chain ester, and an ether is preferably exemplified, and a combination of a cyclic carbonate, a chain ester, and a lactone is more preferable. Of these lactones, 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.

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

(A) One or more nitriles selected from acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, suberonitrile, and sebacononitrile.

(B) cyclohexylbenzene, fluorocyclohexylbenzene compound (1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene, 1 Aromatic compounds having a branched alkyl group such as fluoro-4-tert-butylbenzene, biphenyl, terphenyl (o-, m-, p-isomer), diphenyl ether, fluorobenzene, difluorobenzene (o-, m -, P-form), anisole, 2,4-difluoroanisole, terphenyl partially hydride (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), etc. Aroma Compound.

(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- Propynyl, di (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, di (2-propynyl) glutarate, 2-butyne-1,4-diyl dimethanesulfonate, 2- One or more triple bond-containing compounds selected from butyne-1,4-diyl diformate and 2,4-hexadiyne-1,6-diyl dimethanesulfonate.

(E) 1,3-propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propene sultone, 2,2-dioxide-1,2-oxathiolan-4-yl Acetate, or sultone such as 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, ethylene sulfite, hexahydrobenzo [1,3,2] dioxathiolane-2-oxide (1,2 -Cyclohexanediol cyclic sulfite), or cyclic sulfites such as 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, butane-2,3-diyl dimethanesulfonate, butane -1,4-diyl dimethanesulfonate, or methylenemethane disulfonate Phosphate esters, divinyl sulfone, 1,2-bis (vinylsulfonyl) ethane, or bis (2-vinylsulfonylethyl) one or two or more of the S = O group containing compound selected from vinyl sulfone compounds such as ethers.

(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), bis (2,2,2-trifluoroethyl) methyl phosphate, bis phosphate (2,2,2-trifluoroethyl) ethyl, bis (2,2,2-trifluoroethyl) phosphate 2,2-difluoroethyl, 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 phosphoric acid (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoropropyl) methyl, phosphoric acid tris (1,1,1,3,3,3 -Hexaful Lopropan-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- (dimethoxy) Phosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) L) Acetate, 2-propynyl 2- (dimethoxyphosphoryl) acetate, 2-propynyl 2- (diethoxyphosphoryl) acetate, and one or more phosphorus-containing compounds selected from methyl pyrophosphate and ethyl pyrophosphate.

(H) Chain 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 more selected from biphenyl, terphenyl (o-, m-, p-isomer), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene Are 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, 2-propynyl 2- (methanesulfonyloxy) propionate, di One or more selected from (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, and 2-butyne-1,4-diyl dimethanesulfonate, 2-propynyl methanesulfonate, One or more selected from 2-propynyl vinyl sulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di (2-propynyl) oxalate, and 2-butyne-1,4-diyl dimethanesulfonate Preferred.

  (E) A cyclic or chain-containing S═O group-containing compound selected from sultone, cyclic sulfite, sulfonic acid ester, and vinyl sulfone (provided that the triple bond-containing compound and any of the above general formulas are specified) It is preferable to use a lithium salt.

  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- 1,2-oxathiolan-4-yl acetate, 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, methylene methane disulfonate, ethylene sulfite, and 4- (methylsulfonylmethyl)- One, two or more selected from 1,3,2-dioxathiolane 2-oxide 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 , And 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, butane-2,3-diyl dimethanesulfonate, pentafluorophenyl methanesulfonate, divinylsulfone, or two or more thereof Is 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) Phosphorus-containing compounds include tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3-hexafluoropropan-2-yl), methyl 2- (dimethylphosphoryl) acetate, ethyl 2- (dimethylphosphoryl) acetate, methyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2 -(Diethylphosphoryl) acetate, methyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (Dimethoxyphospho Ryl) acetate or 2-propynyl 2- (diethoxyphosphoryl) acetate is preferred, and tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3- Hexafluoropropan-2-yl), ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (dimethoxyphosphoryl) acetate or 2-propynyl 2- (diethoxyphosphoryl) acetate is more preferred.

  (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]. Lithium salt having at least one oxalic acid skeleton selected from: lithium salt having phosphoric acid skeleton such as LiPO ₂ F ₂ and 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 the lithium salt is suitably exemplified with one or more S = O group selected from _{FSO 3 Li, LiBOB, LiDFOB,} LiTFOP, LiDFOP, LiPO 2 F 2, LiTFMSB, LMS, LES More preferably, it contains a lithium salt selected from LFES, LFES, and FSO ₃ Li.

  The total content of one or more lithium salts selected from lithium salts having an oxalic acid skeleton, lithium salts having a phosphoric acid skeleton, and lithium salts having an S═O group is 0.001 in the non-aqueous electrolyte. -10 mass% is preferable. If the content is 10% by mass or less, a film is excessively formed on the electrode and is less likely to deteriorate the storage characteristics. If the content is 0.001% by mass or more, formation of the film is sufficient, The effect of improving the characteristics when used at a high voltage is increased. The content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and the upper limit is preferably 5% by mass or less in the non-aqueous electrolyte. 3 mass% or less is more preferable, and 2 mass% or less is still more preferable.

(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 , and 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 more of these may be used. The above can be mixed and used.
Among these, at least one selected from LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , and LiN (SO ₂ F) ₂ [LiFSI] is used. Preferably, LiPF ₆ is used. The concentration of the electrolyte salt is usually preferably 0.3 M or more, more preferably 0.7 M or more, and further preferably 1.1 M or more with respect to the non-aqueous solvent. Moreover, the upper limit is preferably 2.5M or less, more preferably 2.0M or less, and still more preferably 1.6M or less.
In addition, as a preferable combination of these electrolyte salts, LiPF ₆ is included, and at least one lithium selected from LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ F) ₂ [LiFSI] is used. The case where the salt is contained in the non-aqueous electrolyte is preferable, and the proportion of the lithium salt other than LiPF _{6 in the} non-aqueous solvent is 0.001M or more, which improves the electrochemical characteristics in a wide temperature range. The effect is easily exerted, and it is preferable that it is 0.005 M or less because there is little concern that the effect of improving electrochemical characteristics in a wide temperature range is reduced. Preferably it is 0.01M or more, Especially preferably, it is 0.03M or more, Most preferably, it is 0.04M or more. The upper limit is preferably 0.4M or less, particularly preferably 0.2M or less.

[Production of non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention is prepared, for example, by mixing the non-aqueous solvent described above with a specific polar group represented by the general formula (I) being phosphorous with respect to the electrolyte salt and the non-aqueous electrolyte. It can be obtained by adding lithium phosphate directly bonded to the atom.
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 more preferably used for a lithium secondary battery.

[First power storage device (lithium battery)]
In this specification, the lithium battery is a general term for a lithium primary battery and a lithium secondary battery. In this specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery. The lithium 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 cobalt, manganese and nickel is used. These positive electrode active materials can be used individually by 1 type or in combination of 2 or more types.
Examples of such a lithium composite metal oxide include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01 <x <1), LiCo _1/3 Ni _1/3. One type or two or more types selected from Mn _1/3 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , and LiCo _0.98 Mg _0.02 O ₂ may be mentioned. 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.

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, A part of O can be substituted with S or F, or a compound containing these other elements can be coated.
Among these, lithium composite metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , and LiNiO ₂ that can be used at a charged potential of the positive electrode in a fully charged state of 4.3 V or more on the basis of Li are preferable, and LiCo _1-x M _x O ₂ (where M is one or more elements selected from Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and Cu, 0.001 ≦ x ≦ 0. 05), LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , Li ₂ MnO ₃ and LiMO ₂ (M is a transition of Co, Ni, Mn, Fe, etc.) A lithium composite metal oxide that can be used at 4.4 V or higher, such as a solid solution with (metal), is more preferable. When a lithium composite metal oxide that operates at a high charging voltage is used, the electrochemical characteristics when used in a wide temperature range are liable to deteriorate due to a reaction with the electrolyte during charging, but the lithium secondary battery according to the present invention Then, the deterioration of these electrochemical characteristics can be suppressed.
In particular, in the case of a positive electrode containing Mn, the resistance of the battery tends to increase with the elution of Mn ions from the positive electrode, so that the electrochemical characteristics when used in a wide temperature range tend to be lowered. The lithium secondary battery according to the invention is preferable because it can suppress a decrease in these electrochemical characteristics.

Furthermore, lithium-containing olivine-type phosphate can also be used as the positive electrode active material. In particular, lithium-containing olivine-type phosphate containing one or more selected from iron, cobalt, nickel and manganese is preferable. Specific examples thereof include one or more selected from LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , and LiMnPO ₄ .
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 may be substituted with one or more elements selected from these, or may 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.

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, sulfur such as SO ₂ and SOCl ₂ Examples thereof include a compound and fluorocarbon (fluorinated graphite) represented by the general formula (CF _x ) _n . Among _{these, MnO 2, V 2 O 5} , fluorinated graphite and the like are preferable.

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 10.5 to 12.0 is more preferable.
Further, when Ni is contained as an element in the positive electrode, since impurities such as LiOH in the positive electrode active material tend to increase, an effect of improving electrochemical characteristics in a wider temperature range is easily obtained, which is preferable. The case where the atomic concentration of Ni in the substance is 5 to 25 atomic% is more preferable, and the case where it is 8 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. For example, graphite such as natural graphite (scaly graphite, etc.), graphite such as artificial graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, and one or more carbon blacks selected from thermal black It is done. 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 especially preferable.

The positive electrode is composed of a conductive agent such as acetylene black and 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 subjected to vacuum 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 a carbon material capable of occluding and releasing lithium (easily graphitized carbon and a (002) plane spacing of 0.37 nm or more). Non-graphitizable carbon, graphite with (002) plane spacing of 0.34 nm or less, etc.], tin (single), tin compound, silicon (single), silicon compound, lithium titanate such as Li ₄ Ti ₅ O ₁₂ A compound etc. can be used individually by 1 type or in combination of 2 or more types.
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 ( ₀₀₂ ) has an interplanar spacing (d ₀₀₂ ) of 0.1. It is more preferable to use a carbon material having a graphite type crystal structure of 340 nm (nanometer) or less, particularly 0.335 to 0.337 nm.
In particular, artificial graphite particles having a massive structure in which a plurality of flat graphite fine particles are assembled or bonded non-parallel to each other, and mechanical actions such as compressive force, frictional force, shearing force, etc. are repeatedly applied, and scaly natural graphite is spherical. It is preferable to use particles that have been treated.
The peak intensity I (110) of the (110) plane of the graphite crystal obtained from the X-ray diffraction measurement of the negative electrode sheet when the density of the portion excluding the current collector of the negative electrode is pressed to a density of 1.5 g / cm ³ or more. ) And the (004) plane peak intensity I (004) ratio I (110) / I (004) is preferably 0.01 or more because the electrochemical characteristics in a wider temperature range are further improved. More preferably, it is more preferably 0.1 or more. In addition, since the crystallinity may be lowered due to excessive treatment and the discharge capacity of the battery may be lowered, the upper limit of the peak intensity ratio I (110) / I (004) is preferably 0.5 or less. 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 characteristics at low or high temperatures due to an increase in interface resistance. However, 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 more preferable because the capacity of the battery can be increased.

The negative electrode is kneaded using the same conductive agent, binder, and high-boiling solvent as in the production 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, more preferably 1.7 g in order to further increase the battery capacity. / Cm ³ or more. The upper limit is preferably 2 g / cm ³ or less.

  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 there is no restriction | limiting in particular as a separator for batteries, The single layer or laminated microporous film of polyolefin, such as a polypropylene and polyethylene, a woven fabric, a nonwoven fabric, etc. can be used.

  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 higher, and more preferably 2.5 V or higher, but the lithium secondary battery in the present invention can be 2.0 V or higher. 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)]
It is an electricity storage device that stores energy by using the electric double layer capacity at the interface between the electrolyte and the electrode. 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]
It is an electrical storage device which stores energy using dope / dedope reaction of an electrode. 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)]
It is an electricity storage device that stores energy by utilizing lithium ion intercalation with a carbon material such as graphite as a negative electrode. It is called a lithium ion capacitor (LIC). Examples of the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, and those using a π-conjugated polymer electrode doping / dedoping reaction. The electrolytic solution contains at least a lithium salt such as LiPF ₆ .

  In the above-described configuration example of the electricity storage device, the example in which the electrolyte includes lithium phosphate in which the specific polar group represented by the general formulas (II) to (IV) is directly bonded to the phosphorus atom has been described. You may contain lithium acid in other electrical storage device components other than electrolyte solution.

  In the second to fourth aspects described below, lithium phosphate in which the specific polar group represented by the general formula (I) is directly bonded to the phosphorus atom is added in advance to other components other than the electrolytic solution. An example of the electricity storage device will be described.

[Second embodiment: Example in which lithium phosphate in which specific polar group represented by general formula (I) is directly bonded to phosphorus atom is added to positive electrode]
Lithium phosphate in which a specific polar group represented by the general formula (I) is directly bonded to a phosphorus atom is mixed with the above-described positive electrode active material, conductive agent, and binder, and this is mixed with 1-methyl-2- After adding a high boiling point solvent such as pyrrolidone and kneading to make a positive electrode mixture, this positive electrode mixture was applied to a current collector aluminum foil or stainless steel lath plate, etc., 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 addition amount of lithium phosphate in which the specific polar group represented by the general formula (I) is directly bonded to the phosphorus atom is preferably 0.001 to 10% by mass with respect to the positive electrode active material. The addition amount is more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more with respect to the positive electrode active material. Moreover, the upper limit is more preferably 8% by mass or less, and further preferably 5% by mass or less.

[Third embodiment: Example in which lithium phosphate in which specific polar group represented by general formula (I) is directly bonded to phosphorus atom is added to negative electrode]
The lithium carboxylate represented by the general formula (I) is kneaded using the same conductive agent, binder, and high-boiling solvent as in the production of the positive electrode to obtain a negative electrode mixture. It can be produced by applying to a copper foil or the like of a current collector, drying and press-molding, and then heat-treating under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours.

  The addition amount of lithium phosphate in which the specific polar group represented by the general formula (I) is directly bonded to the phosphorus atom is preferably 0.001 to 10% by mass with respect to the negative electrode active material. The addition amount is more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more with respect to the negative electrode active material. Moreover, the upper limit is more preferably 8% by mass or less, and further preferably 5% by mass or less.

[Fourth aspect: Example in which lithium phosphate in which specific polar group represented by general formula (I) is directly bonded to phosphorus atom is added to separator]
The separator is immersed in a solution in which a lithium phosphate having a specific polar group represented by the general formula (I) directly bonded to a phosphorus atom dissolved in an organic solvent or water is impregnated, and then dried by a method of drying the general formula ( A separator containing lithium phosphate, in which the specific polar group represented by I) is directly bonded to the phosphorus atom, on the surface or in the pores can be produced. In addition, a coating liquid is prepared by dispersing lithium phosphate in which a specific polar group represented by the general formula (I) is directly bonded to a phosphorus atom in an organic solvent or water, and the coating liquid is applied to the entire surface of the separator. It can produce by apply | coating.

  A lithium phosphate in which a specific polar group is directly bonded to a phosphorus atom (P) represented by general formulas (V) to (VII), which is a novel substance of the present invention.

（Ｒ^１１及びＲ^１２はそれぞれ独立にＲと同義である。ただし、Ｒ^１１及びＲ^１２の少なくとも１方は炭素数３〜６のアルキニル基である。）

(R ¹¹ and R ¹² are each independently synonymous with R. However, at least one of R ¹¹ and R ¹² is an alkynyl group having 3 to 6 carbon atoms.)

（Ｒ^１１、Ｒ^１３、及びＲ^１４はそれぞれ独立にＲと同義である。ただし、Ｒ^１１、Ｒ^１３、及びＲ^１４のすべてがリチウム原子の場合は除く。）

(R ¹¹ , R ¹³ , and R ¹⁴ are each independently synonymous with R, except when R ¹¹ , R ¹³ , and R ¹⁴ are all lithium atoms.)

（Ｒ^１１及びＲ^１５はそれぞれ独立にＲと同義である。）

(R ¹¹ and R ¹⁵ are each independently synonymous with R.)

  The lithium phosphate in which a specific polar group is directly bonded to the phosphorus atom (P) represented by the general formulas (V) to (VII) used in the present invention, the phosphate ester as a precursor is added in the presence of a solvent. Although it can synthesize | combine by making it react with lithium salt, it is not limited to these methods at all.

  The phosphoric acid ester used as a precursor can be synthesized by a known method. For example, Journal of the American Chemical Society, 2006, vol. 128, # 15, p. 5251-5261, Angelwandte Chemie-International Edition, 2010, vol. 49, # 38, p. The method described in Japanese Patent No. 6852-6855, German Patent No. 956404, or the like can be applied.

  Examples of the lithium base include lithium acetate, lithium formate, lithium propionate, lithium trifluoroacetate, lithium oxalate, or lithium benzoate, lithium fluoride, lithium chloride, lithium chloride, lithium bromide, or lithium iodide. Suitable examples include alkali metal halides such as lithium carbonate, lithium carbonate, and lithium hydroxide, but are not limited thereto.

  Among the lithium salts, lithium acetate, lithium chloride, lithium iodide, lithium carbonate, or lithium hydroxide is preferable, and lithium acetate or lithium chloride is more preferable.

  The amount of the lithium salt used is preferably 0.5 mol or more, more preferably 0.7 mol or more, still more preferably 0.9 mol or more with respect to 1 mol of the phosphate ester. . This is because if the amount is less than 0.5 mol, the reaction does not proceed sufficiently and the yield decreases. As an upper limit, 2 mol or less is preferable, 1.5 mol or less is more preferable, and it is still more preferable that it is 1.1 mol or less. This is because when the amount of the lithium salt used is more than 2 moles, side reactions are likely to proceed, the yield decreases, and impurities increase.

  As the solvent used in the reaction, water, alcohol, nitrile, ketone, sulfone, amide, ether, ester, aromatic, or halogenated hydrocarbon is preferably exemplified, and alcohol, ketone, or ether is particularly preferable.

Specific examples of the solvent include the following.
Water, alcohol such as methanol, ethanol, n-propanol, nitrile such as acetonitrile or propionitrile, ketone such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, sulfone such as dimethyl sulfoxide, N, N-dimethylformamide or N, N -Amides such as dimethylacetamide, ethers such as diethyl ether or tetrahydrofuran, ethyl acetate, ethyl propionate, esters such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate, aromatics such as toluene or xylene, or dichloromethane, 1,2 -Halogen-based hydrocarbons such as dichloroethane or o-dichlorobenzene are preferably exemplified, but the solvent is not limited thereto as long as it does not inhibit the reaction.

  Among them, alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, or ethers such as diethyl ether and tetrahydrofuran are preferable, and acetone, methyl ethyl ketone, diethyl ether, and tetrahydrofuran are more preferable.

  0.5 mass part or more is preferable with respect to 1 mass part of phosphate ester, and, as for the minimum of the usage-amount of the said solvent, 1 mass part or more is more preferable. The upper limit of the amount of the organic solvent used is preferably 50 parts by mass or less and more preferably 20 parts by mass or less with respect to 1 part by mass of the phosphate ester.

  As an upper limit of reaction temperature, 80 degrees C or less is preferable, 70 degrees C or less is more preferable, and 60 degrees C or less is especially preferable. This is because when the reaction temperature is higher than 80 ° C., the side reaction easily proceeds. As a minimum, 0 degreeC or more is preferable, 5 degreeC or more is more preferable, and 10 degreeC or more is especially preferable. This is because when the reaction temperature is lower than 0 ° C., the reaction rate is greatly reduced. However, when the boiling point of the solvent used is 80 ° C. or lower, the boiling point of the solvent is the upper limit of the reaction temperature, and when the melting point of the solvent used is 0 ° C. or higher, the melting point of the organic solvent is the lower limit of the reaction temperature.

  The reaction time varies depending on the reaction temperature and the amount of lithium salt and solvent used, but the lower limit is preferably 0.5 hours or more, and more preferably 1 hour or more. This is because the reaction does not proceed sufficiently in less than 0.5 hours. On the other hand, the upper limit is preferably 24 hours or less, and more preferably 16 hours or less. This is because if the time exceeds 24 hours, the side reaction tends to proceed.

  Hereinafter, although the synthesis example of lithium phosphate represented by general formula (I) and the Example of electrolyte solution using the same are shown, this invention is not limited at all by these examples.

Synthesis Example 1 [Synthesis of Lithium Ethyl 2-propynyloxycarbonylphosphonate (Compound A57)]
2-Propinyl (diethoxyphosphorylphoryl) formate (10.00 g, 45.4 mmol) was added to a slurry of lithium chloride (1.73 g, 40.9 mmol) and acetone (70 g) and refluxed for 6 hours. After cooling to room temperature, white crystals were separated by filtration, washed with tetrahydrofuran, and then dried under reduced pressure to obtain 2.45 g of lithium ethyl 2-propynyloxycarbonylphosphonate (yield 30%).
About the obtained lithium ethyl 2-propynyloxycarbonyl phosphonate, < ¹ > H-NMR measurement was performed and the structure was confirmed.
(1) ¹ H-NMR (400 MHz, DMSO-d ₆ ): δ = 4.61 (dd, J = 2.4, 0.9 Hz, 2 H), 3.84-3.77 (m, 2 H), 3.49 (t, J = 2.4 Hz, 1 H), 1.12 (t, J = 7.1 Hz, 3 H)

Examples 1-19, Comparative Examples 1-2
[Production of lithium ion secondary battery]
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ; 94% by mass, acetylene black (conductive agent); 3% by mass are mixed, and polyvinylidene fluoride (binder); In addition to the solution dissolved in -2-pyrrolidone, the mixture was mixed to prepare a positive electrode mixture paste. 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, silicon (simple substance): 10% by mass, artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material); 80% by mass, acetylene black (conductive agent); Adhesive); 5% by mass was added to and mixed with the solution in which 1-methyl-2-pyrrolidone was dissolved to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried and pressurized, punched out to a predetermined size, and a negative electrode sheet was produced. 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 characteristics after high temperature charge storage]
<Initial discharge capacity>
Using the coin battery produced by the above method, in a constant temperature bath at 25 ° C., charge at a constant current of 1 C and a constant voltage to a final voltage of 4.35 V for 3 hours, lower the temperature of the constant temperature bath to −10 ° C., The battery was discharged to a final voltage of 2.75 V under a constant current of 1 C, and an initial discharge capacity of −10 ° C. was obtained.
<High-temperature charge storage test>
Next, this coin battery was charged in a constant temperature bath of 65 ° C. with a constant current and a constant voltage of 1 C for 3 hours to a final voltage of 4.35 V, and stored for 10 days in a state where it was maintained at 4.35 V. Then, it put into the thermostat of 25 degreeC, and discharged once to the final voltage 2.75V under the constant current of 1C.
<Discharge capacity after storage at high temperature>
Thereafter, in the same manner as the measurement of the initial discharge capacity, the discharge capacity at −10 ° C. after storage at high temperature was obtained.
<Low temperature characteristics after high temperature charge storage>
The low temperature characteristic after high temperature charge storage was calculated | required from the following -10 degreeC discharge capacity maintenance factor.
−10 ° C. discharge capacity retention ratio after storage at high temperature charge (%) = (− 10 ° C. discharge capacity after initial storage at high temperature / initial discharge capacity at −10 ° C.) × 100
The battery characteristics are shown in Tables 1-3.

Example 20, Comparative Example 3
A positive electrode sheet was produced using LiNi _1/2 Mn _3/2 O ₄ (positive electrode active material) instead of the positive electrode active material used in Example 1. LiNi _1/2 Mn _3/2 O ₄ coated with amorphous carbon; 94% by mass, acetylene black (conductive agent); 3% by mass are mixed in advance and polyvinylidene fluoride (binder); 3% by mass Was added to a solution dissolved in 1-methyl-2-pyrrolidone and mixed to prepare a positive electrode mixture paste. 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 prepared. A coin battery was fabricated and evaluated in the same manner as in Example 1 except that the discharge end voltage was 4.9 V and the non-aqueous electrolyte composition was changed to a predetermined one. . The results are shown in Table 4.

Example 21 and Comparative Example 4
In place of the negative electrode active material used in Example 1, a negative electrode sheet was prepared using lithium titanate Li ₄ Ti ₅ O ₁₂ (negative electrode active material). Lithium titanate Li ₄ Ti ₅ O ₁₂ ; 80% by mass, acetylene black (conductive agent); 15% by mass are mixed in advance, and polyvinylidene fluoride (binder); 5% by mass in 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 onto a copper foil (current collector), dried and pressurized, punched out to a predetermined size, and a negative electrode sheet was produced. A coin battery was fabricated and evaluated in the same manner as in Example 1 except that the discharge end voltage was 8 V, the discharge end voltage was 1.2 V, and the composition of the nonaqueous electrolyte was changed to a predetermined one. The results are shown in Table 5.

Examples 22-23
Comparative example except that a positive electrode prepared by adding a predetermined amount of lithium phosphate in which a specific polar group represented by the general formula (I) is directly bonded to a phosphorus atom to 100% of the positive electrode active material was used. A lithium secondary battery was prepared in the same manner as in Example 1, and the battery was evaluated. The results are shown in Table 6.

Examples 24-25
A lithium secondary battery was produced in the same manner as in Comparative Example 1 except that lithium phosphate in which the specific polar group represented by the general formula (I) was directly bonded to the phosphorus atom was not added to the positive electrode, but was added to the negative electrode. The battery was evaluated. The results are shown in Table 6.

In any of the lithium secondary batteries of Examples 1 to 19, phosphorus in which a specific polar group (X) is directly bonded to the phosphorus atom (P) represented by the general formula (I) in the nonaqueous electrolytic solution of the present invention. Compared to the lithium secondary battery of Comparative Example 1 in which no lithium acid was added and Comparative Example 2 in which triethylphosphonoformate was added, the electrochemical characteristics in a wide temperature range were remarkably improved. As described above, the effect of the present invention is that, in a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, lithium phosphate in which a specific polar group (X) is directly bonded to the phosphorus atom (P) of the present invention is used. It was found that the effect was unique when it was contained.
Further, from the comparison between Example 20 and Comparative Example 3 and the comparison between Example 21 and Comparative Example 4, when nickel manganate lithium salt (LiNi _1/2 Mn _3/2 O ₄ ) was used for the positive electrode, or titanium was used for the negative electrode. Since the same effect is observed when lithium acid is used, it is clear that the effect is not dependent on a specific positive electrode or negative electrode.

  Further, from the comparison between Examples 22 to 25 and Comparative Example 1, lithium phosphate in which a specific polar group (X) was directly bonded to the phosphorus atom (P) represented by the general formula (I) It was found that there is an effect even if it is included in.

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

  If the non-aqueous electrolyte of the present invention is used, an electricity storage device having excellent electrochemical characteristics in a wide temperature range can be obtained. Especially when used as a non-aqueous electrolyte for electricity storage devices such as lithium secondary batteries mounted on hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, etc., the electricity storage devices are unlikely to deteriorate in electrochemical characteristics over a wide temperature range. Can be obtained.

Claims (5)

In a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, it contains at least one lithium phosphate in which a specific polar group (X) is directly bonded to the phosphorus atom (P) represented by the general formula (I) A non-aqueous electrolyte characterized by:

(R is a part of a hydrogen atom selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 12 carbon atoms. Is an organic group optionally substituted with a halogen atom or a lithium atom, and X is a polar group containing a —C (═O) group, a —P (═O) group, or a —S (═O) ₂ group. is there.) The lithium phosphate is at least one selected from the group consisting of lithium phosphates in which a specific polar group is directly bonded to a phosphorus atom (P) represented by the following general formulas (II) to (IV). The nonaqueous electrolytic solution according to claim 1.

(R ¹ and R ² are each independently synonymous with R.)

(R ¹ , R ³ , and R ⁴ are each independently synonymous with R.)

(R ¹ and R ⁵ are each independently synonymous with R.)   An electricity storage device comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte is the non-aqueous electrolyte according to claim 2. device. Lithium phosphate in which a specific polar group is directly bonded to the phosphorus atom (P) represented by the general formulas (V) to (VII).

(R ¹¹ and R ¹² are each independently synonymous with R. However, at least one of R ¹¹ and R ¹² is an alkynyl group having 3 to 6 carbon atoms.)

(R ¹¹ , R ¹³ , and R ¹⁴ are each independently synonymous with R, except when R ¹¹ , R ¹³ , and R ¹⁴ are all lithium atoms.)

(R ¹¹ and R ¹⁵ are each independently synonymous with R.) An additive for an electricity storage device comprising lithium phosphate in which a specific polar group is directly bonded to a phosphorus atom (P) represented by general formulas (V) to (VII).

(R ¹¹ and R ¹² are each independently synonymous with R. However, at least one of R ¹¹ and R ¹² is an alkynyl group having 3 to 6 carbon atoms.)

(R ¹¹ , R ¹³ , and R ¹⁴ are each independently synonymous with R, except when R ¹¹ , R ¹³ , and R ¹⁴ are all lithium atoms.)

(R ¹¹ and R ¹⁵ are each independently synonymous with R.)