JP2015133255A - Nonaqueous electrolyte and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte in which generation of gas, that is, decomposition of the electrolyte is suppressed even when applied to a lithium ion secondary battery having higher positive electrode potential than conventional one and which is excellent in cycle characteristics, and also to provide the lithium ion secondary battery using the nonaqueous electrolyte.SOLUTION: A nonaqueous electrolyte contains a nonaqueous solvent, a lithium electrolyte, LiPOF, and an organic phosphorus compound whose highest occupied molecular orbital energy calculated by the density functional theory calculation is 8.0 eV or more and -7.0 eV or less.

Description

  The present invention relates to a non-aqueous electrolyte and a lithium ion secondary battery using the non-aqueous electrolyte.

  Lithium ion secondary batteries are widely used as power sources for mobile electronic devices such as mobile phones because they have excellent characteristics such as high energy density and high durability. In recent years, they are also used as power sources for automobiles such as electric vehicles. Has been.

At present, lithium ion secondary batteries are widely used. However, users of mobile electronic devices and electric vehicles still have a demand for higher energy density of batteries. In order to respond to this, attempts to improve the energy density of the battery are actively made, and in particular, attention has been paid to the expansion of the charging depth of the positive electrode active material and the development of a high potential positive electrode. According to Patent Document 1, when lithium-cobalt composite oxide (LiCoO ₂ ) is charged until the positive electrode potential becomes 4.3 V of lithium reference, the charging capacity is about 155 mAh / g, whereas it is 4.5 V. When it is charged until it becomes, the charge capacity becomes 190 mAh / g or more. Thus, by raising the potential of the positive electrode during full charge, the utilization factor of the positive electrode active material is improved, and as a result, the energy density of the battery can be increased.

  In a lithium ion secondary battery, a nonaqueous electrolytic solution in which a lithium electrolyte is dissolved in a nonaqueous solvent is used. As the non-aqueous solvent, a carbonate solvent obtained by mixing cyclic carbonates such as ethylene carbonate and propylene carbonate and chain carbonates such as dimethyl carbonate and ethyl methyl carbonate in a specific ratio is employed. Carbonate solvent has sufficient oxidation resistance and reduction resistance when applied to a conventional lithium ion secondary battery having a positive electrode potential of about 4.3 V with respect to lithium when fully charged, and also has lithium ion conductivity. Due to its superiority, it has been widely used. However, in a battery having a higher positive electrode potential than the conventional one, the carbonate solvent is decomposed, so that decomposition products are accumulated and gas is generated inside the battery, and various battery characteristics such as cycle characteristics and storage characteristics are deteriorated. Problems arise.

  In order to solve the above problem, Patent Document 2 proposes a method of suppressing decomposition of the nonaqueous electrolytic solution on the positive electrode side by including a specific phosphate ester compound in the nonaqueous electrolytic solution. ing. Specifically, the oxidation resistance of the non-aqueous electrolyte is improved by adding 5% by mass of tris (2-propenyl) phosphate to the non-aqueous electrolyte.

  Patent Document 3 proposes a method for improving the high-temperature cycle characteristics of a lithium ion secondary battery by including a specific unsaturated phosphate ester compound in the nonaqueous electrolytic solution. Specifically, it is described that high-temperature cycle characteristics are improved by adding 1% by mass of tris (2-propynyl) phosphate with respect to the nonaqueous electrolytic solution.

International Publication No. 2008/114739 JP 2006-221972 A JP 2011-77029 A

  However, the non-aqueous electrolyte added with 5% by mass of tris (2-propenyl) phosphate disclosed in Patent Document 2 and 1% by mass of tris (2-propynyl) phosphate disclosed in Patent Document 3 None of the added non-aqueous electrolytes is effective in suppressing gas generation and improving cycle characteristics when used in a lithium ion secondary battery having a higher positive electrode potential than the conventional one.

  As described above, the conventional technology does not show a solution for sufficiently suppressing cycle deterioration and gas generation in a lithium ion secondary battery having a high positive electrode potential.

  The present invention has been made in view of the above problems, and even when applied to a lithium ion secondary battery having a higher positive electrode potential than the conventional one, generation of gas, that is, decomposition of the electrolytic solution is suppressed, and cycle characteristics are excellent. An object is to provide a non-aqueous electrolyte and a lithium ion secondary battery using the non-aqueous electrolyte.

As a result of intensive studies to achieve the above object, the present inventors use a nonaqueous electrolytic solution containing a lithium electrolyte, LiPO ₂ F _2, and a specific organic phosphorus compound in a nonaqueous solvent. As a result, the inventors have found that the above problems can be solved, and have completed the present invention.

（上記一般式（１）中、Ｒ^１、Ｒ^２、及びＲ^３は、各々独立に、水素原子、置換されていてもよい炭素数２以上１５以下のアルキル基、置換されていてもよい炭素数２以上１５以下のアルケニル基、置換されていてもよい炭素数２以上１５以下のアルキニル基、又は置換されていてもよい炭素数６以上１５以下のアリール基であり、Ｒ^１、Ｒ^２、及びＲ^３のうち、少なくとも２つが結合して環構造を形成していてもよい。）

（上記一般式（２）中、Ｒ^４は、置換されていてもよい炭素数１以上１５以下のアルキル基又は置換されていてもよい炭素数６以上１５以下のアリール基であり、Ｒ^５及びＲ^６は、各々独立に、水素原子、置換されていてもよい炭素数２以上１５以下のアルキル基、置換されていてもよい炭素数２以上１５以下のアルケニル基、置換されていてもよい炭素数２以上１５以下のアルキニル基、又は置換されていてもよい炭素数６以上１５以下のアリール基であり、Ｒ^５及びＲ^６は、結合して環構造を形成していてもよい。）
〔３〕
前記有機リン化合物の含有量が、前記非水電解液の総量に対して、０．０１質量％以上１０質量％以下である、前項〔１〕〜〔２〕のいずれか一項に記載の非水電解液。
〔４〕
前記ＬｉＰＯ_２Ｆ_２の含有量が、前記非水電解液の総量に対して、０．００１質量％以上１０質量％以下である、前項〔１〕〜〔３〕のいずれか一項に記載の非水電解液。
〔５〕
前記リチウム電解質が、ＬｉＰＦ_６、ＬｉＢＦ_４、ＬｉＮ（ＳＯ_２Ｆ）_２、及びＬｉＮ（ＳＯ_２ＣＦ_３）_２からなる群より選ばれる１種以上を含む、前項〔１〕〜〔４〕のいずれか一項に記載の非水電解液。
〔６〕
前記一般式（１）中のＲ^１、Ｒ^２、及びＲ^３、並びに、前記一般式（２）中のＲ^５及びＲ^６が、各々独立に、置換されていてもよい炭素数２以上１５以下のアルケニル基又は置換されていてもよい炭素数２以上１５以下のアルキニル基である、前項〔２〕〜〔５〕のいずれか一項に記載の非水電解液。
〔７〕
前記非水溶媒が、エチレンカーボネート、プロピレンカーボネート、及びフルオロエチレンカーボネートからなる群より選ばれる一種以上の環状カーボネートを含有する、前項〔１〕〜〔６〕のいずれか一項に記載の非水電解液。
〔８〕
前記一般式（１）中のＲ^１、Ｒ^２、及びＲ^３、並びに、前記一般式（２）中のＲ^５及びＲ^６が、各々独立に、エテニル基、エチニル基、２−プロペニル基、２−プロピニル基、２−ブテニル基、２−ブチニル基、３−ブテニル基、又は３−ブチニル基である、前項〔２〕〜〔７〕のいずれか一項に記載の非水電解液。
〔９〕
正極と、負極と、前項〔１〕〜〔８〕のいずれか一項に記載の非水電解液と、を備え、満充電時の前記正極の電位が、リチウム基準で４．４Ｖ以上５．０Ｖ以下である、リチウムイオン二次電池。 That is, the present invention is as follows.
[1]
A non-aqueous solvent, a lithium electrolyte, LiPO ₂ F _2, and an organophosphorus compound having a maximum occupied orbital energy calculated by density functional calculation of −8.0 eV or more and −7.0 eV or less. , Non-aqueous electrolyte.
[2]
The non-aqueous electrolysis according to [1], wherein the organophosphorus compound includes an organophosphorus compound represented by the following general formula (1) and / or an organophosphorus compound represented by the following general formula (2). liquid.

(In the general formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, and an optionally substituted carbon. An alkenyl group having 2 to 15 carbon atoms, an alkynyl group having 2 to 15 carbon atoms which may be substituted, or an aryl group having 6 to 15 carbon atoms which may be substituted; R ¹ , R ² , And at least two of R ³ may be bonded to form a ring structure.)

(In the above general formula (2), R ⁴ is an optionally substituted alkyl group having 1 to 15 carbon atoms or an optionally substituted aryl group having 6 to 15 carbon atoms, and R ⁵ and Each R ⁶ independently represents a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, an optionally substituted alkenyl group having 2 to 15 carbon atoms, or an optionally substituted carbon; An alkynyl group having 2 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms which may be substituted, and R ⁵ and R ⁶ may be bonded to form a ring structure.
[3]
The content of the organophosphorus compound is 0.01% by mass or more and 10% by mass or less with respect to the total amount of the nonaqueous electrolyte solution, according to any one of [1] to [2] above. Water electrolyte.
[4]
The content of the LiPO ₂ F _{2 according} to any one of [1] to [3], wherein the content is 0.001% by mass to 10% by mass with respect to the total amount of the nonaqueous electrolytic solution. Non-aqueous electrolyte.
[5]
Any of [1] to [4] above, wherein the lithium electrolyte contains one or more selected from the group consisting of LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ , and LiN (SO ₂ CF ₃ ) _2. The non-aqueous electrolyte according to any one of the above.
[6]
R ¹ , R ² , and R ^{3 in} the general formula (1), and R ⁵ and R ⁶ in the general formula (2) are each independently 2 to 15 carbon atoms that may be substituted. The nonaqueous electrolytic solution according to any one of [2] to [5], which is the following alkenyl group or an optionally substituted alkynyl group having 2 to 15 carbon atoms.
[7]
The nonaqueous electrolysis according to any one of [1] to [6], wherein the nonaqueous solvent contains one or more cyclic carbonates selected from the group consisting of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate. liquid.
[8]
R ¹ , R ² , and R ^{3 in} the general formula (1) and R ⁵ and R ⁶ in the general formula (2) are each independently ethenyl group, ethynyl group, 2-propenyl group, The nonaqueous electrolytic solution according to any one of [2] to [7], which is a 2-propynyl group, a 2-butenyl group, a 2-butynyl group, a 3-butenyl group, or a 3-butynyl group.
[9]
A positive electrode, a negative electrode, and the non-aqueous electrolyte according to any one of [1] to [8] above, wherein the potential of the positive electrode at full charge is 4.4 V or more on the basis of lithium. A lithium ion secondary battery that is 0 V or less.

  According to the present invention, even when applied to a lithium ion secondary battery having a higher positive electrode potential than the conventional one, generation of gas, that is, decomposition of the electrolytic solution is suppressed, and the nonaqueous electrolytic solution excellent in cycle characteristics and the nonaqueous electrolytic solution are provided. A lithium ion secondary battery using the liquid can be provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to this, and various modifications can be made without departing from the gist thereof. Is possible.

[Non-aqueous electrolyte]
The non-aqueous electrolyte of the present embodiment has a non-aqueous solvent, a lithium electrolyte, LiPO ₂ F _2, and a maximum occupied orbital energy calculated by density functional calculation is −8.0 eV or more and −7.0 eV or less. And an organic phosphorus compound. The “organic phosphorus compound” in this embodiment is defined to indicate a phosphate ester compound and a phosphonate ester compound.

[Organic phosphorus compounds]
The nonaqueous electrolytic solution of the present embodiment contains an organophosphorus compound having a maximum occupied orbital energy calculated by density functional method calculation of −8.0 eV or more and −7.0 eV or less. In the non-aqueous electrolyte, the present inventors include LiPO ₂ F ₂ and an organophosphorus compound having a maximum occupied orbital energy calculated by density functional calculation of −8.0 eV or more and −7.0 eV or less. It has been found that a remarkable cycle characteristic improvement effect and a gas generation suppression effect can be obtained when, is used in combination.

  Here, the “density functional calculation” is an electronic state calculation based on a density functional theory that physical properties such as energy of an electron system can be calculated from the electron density. Using density functional calculation, it is possible to calculate physical properties such as the highest occupied orbit energy of the target electronic system. "Maximum occupied orbital energy" refers to the energy level of the highest occupied orbital, and is an index indicating the energy required to extract one electron from the electron system, and is related to the oxidation resistance of the molecule. is there. It is known that molecules with the highest occupied orbital energy tend to be oxidized, and molecules with the lowest occupied orbital energy tend to be less likely to be oxidized. The maximum occupied orbit energy in the present invention is obtained by using Gaussian 09 of Gaussian, which is commercially available software, using density functional method (B3LYP) as a calculation method and 6-31G + (d, p) as a basis function. It shall be calculated by optimizing the value by self-intangible landing calculation.

  The maximum occupied orbital energy of the organophosphorus compound is −8.0 eV or more and −7.0 eV or less, preferably −7.9 eV or more and −7.1 eV or less, and more preferably −7.8 eV or more and −7. 2 eV or less, more preferably −7.7 eV or more and −7.3 eV or less. When the maximum occupied orbital energy of the organophosphorus compound is −8 eV or more, a remarkable cycle characteristic improvement effect and gas generation suppression effect can be obtained. Moreover, when the maximum occupied orbital energy of the organic phosphorus compound is −7 eV or less, the stability of the organic phosphorus compound in the nonaqueous electrolytic solution is improved. When at least one double bond or triple bond exists in the molecule of the organophosphorus compound, since the highest occupied orbital energy of the organophosphorus compound tends to fall within the above range, the organophosphorus compound has an alkenyl group. Or it is preferable to have an alkynyl group.

（上記一般式（１）中、Ｒ^１、Ｒ^２、及びＲ^３は、各々独立に、水素原子、置換されていてもよい炭素数２以上１５以下のアルキル基、置換されていてもよい炭素数２以上１５以下のアルケニル基、置換されていてもよい炭素数２以上１５以下のアルキニル基、又は置換されていてもよい炭素数６以上１５以下のアリール基であり、Ｒ^１、Ｒ^２、及びＲ^３のうち、少なくとも２つが結合して環構造を形成していてもよい） Although it does not specifically limit as said organic phosphorus compound of this embodiment, For example, the organic phosphorus compound represented by following General formula (1) can be used.

(In the general formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, and an optionally substituted carbon. An alkenyl group having 2 to 15 carbon atoms, an alkynyl group having 2 to 15 carbon atoms which may be substituted, or an aryl group having 6 to 15 carbon atoms which may be substituted; R ¹ , R ² , And at least two of R ³ may combine to form a ring structure)

In the present embodiment, in the general formula (1), R ¹ , R ² , and R ³ are each independently a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, and a substituted group. An alkenyl group having 2 to 15 carbon atoms which may be substituted, an alkynyl group having 2 to 15 carbon atoms which may be substituted, or an aryl group having 6 to 15 carbon atoms which may be substituted; R ¹ , R ² , and R ³ may combine to form a ring structure. Among these, as R ¹ , R ² , and R ³ , an alkenyl group having 2 to 15 carbon atoms which may be substituted or 2 to 15 carbon atoms which may be substituted may be used from the viewpoint of suppressing gas generation. The following alkynyl groups are preferred.

  Although it does not specifically limit as an alkyl group in the said General formula (1), For example, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group is mentioned. A hydrogen atom or a carbon atom in these alkyl groups may be substituted with a different element or substituent as necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. The substituent is not particularly limited, and examples thereof include ethyl, propyl, butyl, pentyl, phenyl, cyano, nitro, hydroxy, carboxy, sulfo, phosphono, and ether groups. , Sulfide groups, carbonyl groups, and sulfonyl groups. The number of carbon atoms of the alkyl group is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, and still more preferably 2 or more and 6 or less, from the viewpoint of suppressing gas generation. The organophosphorus compound represented by the general formula (1) having an alkyl group is not particularly limited. For example, triethyl phosphate, tripropyl phosphate, tributyl phosphate, tripentyl phosphate, ethyl ethylene phosphate, Mention may be made of propyl ethylene phosphate, butyl ethylene phosphate, pentyl ethylene phosphate, hexyl ethylene phosphate, heptyl ethylene phosphate, octyl ethylene phosphate.

  The alkenyl group in the general formula (1) is not particularly limited, and examples thereof include ethenyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, and benzyl group. Can be mentioned. The hydrogen atom or carbon atom in these alkenyl groups may be substituted with a different element or a substituent, if necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. The substituent is not particularly limited, and examples thereof include ethyl, propyl, butyl, pentyl, phenyl, cyano, nitro, hydroxy, carboxy, sulfo, phosphono, and ether groups. , Sulfide groups, carbonyl groups, and sulfonyl groups. The carbon number of the alkenyl group is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, and further preferably 2 or more and 6 or less, from the viewpoint of suppressing gas generation. Examples of the organic phosphorus compound represented by the general formula (1) having the alkenyl group include triethenyl phosphate, tris (1-propenyl) phosphate, tris (2-propenyl) phosphate, and tris (1-butenyl). ) Phosphate, tris (2-butenyl) phosphate, tris (3-butenyl) phosphate, ethenylethylene phosphate, 2-propenylethylene phosphate, 2-butenylethylenephosphate, 3-butenylethylenephosphate Is mentioned.

  Although it does not specifically limit as an alkynyl group in the said General formula (1), For example, an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, a decynyl group is mentioned, for example. The hydrogen atom or carbon atom in these alkynyl groups may be substituted with a different element or a substituent, if necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. The substituent is not particularly limited, and examples thereof include ethyl, propyl, butyl, pentyl, phenyl, cyano, nitro, hydroxy, carboxy, sulfo, phosphono, and ether groups. , Sulfide groups, carbonyl groups, and sulfonyl groups. The carbon number of the alkynyl group is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, and further preferably 2 or more and 6 or less, from the viewpoint of suppressing gas generation. Examples of the organophosphorus compound represented by the general formula (1) having alkynyl include triethynyl phosphate, tris (1-propynyl) phosphate, tris (2-propynyl) phosphate, and tris (1-butynyl). Examples include phosphate, tris (2-butynyl) phosphate, tris (3-butynyl) phosphate, ethynyl ethylene phosphate, 2-propynyl ethylene phosphate, 2-butynyl ethylene phosphate, 3-butynyl ethylene phosphate It is done.

  Although it does not specifically limit as an aryl group in the said General formula (1), For example, a phenyl group, 1-naphthyl group, 2-naphthyl group, a benzyl group etc. are mentioned. A hydrogen atom or a carbon atom in these aryl groups may be substituted with a different element or substituent as necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. The substituent is not particularly limited, and examples thereof include ethyl, propyl, butyl, pentyl, cyano, nitro, hydroxy, carboxy, sulfo, phosphono, ether, and sulfide groups. , A carbonyl group, and a sulfonyl group. The number of carbon atoms of the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 8 or less, and still more preferably 6 or more and 7 or less, from the viewpoint of suppressing gas generation. Examples of the organic phosphorus compound represented by the general formula (1) having an aryl group include triphenyl phosphate and tribenzyl phosphate.

R ¹ , R ² , and R ³ are each independently a hydrogen atom, an optionally substituted alkyl group having 2 to 10 carbon atoms, or an optionally substituted carbon number from the viewpoint of improving cycle characteristics. An alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms which may be substituted, or an aryl group having 6 to 10 carbon atoms which may be substituted is preferable, more preferably a hydrogen atom, An alkenyl group having 2 to 8 carbon atoms which may be substituted, or an alkynyl group having 2 to 8 carbon atoms which may be substituted, more preferably an alkenyl group having 2 to 6 carbon atoms or carbon It is an alkynyl group having a number of 2 or more and 6 or less. Among these, from the viewpoint of ease of synthesis, ethenyl group, ethynyl group, 2-propenyl group, 2-propynyl group, 2-butenyl group, 2-butynyl group, 3-butenyl group and 3-butynyl are particularly preferable. It is a group. In addition, even when at least two of R ¹ , R ² , and R ³ are bonded to form a ring structure, a good cycle characteristic improving effect and gas generation suppressing effect can be obtained.

（上記一般式（２）中、Ｒ^４は、置換されていてもよい炭素数１以上１５以下のアルキル基及び置換されていてもよい炭素数６以上１５以下のアリール基であり、Ｒ^５及びＲ^６は、各々独立に、水素原子、置換されていてもよい炭素数２以上１５以下のアルキル基、置換されていてもよい炭素数２以上１５以下のアルケニル基、置換されていてもよい炭素数２以上１５以下のアルキニル基、又は置換されていてもよい炭素数６以上１５以下のアリール基であり、Ｒ^５及びＲ^６は、結合して環構造を形成していてもよい） As the organophosphorus compound of the present embodiment, an organophosphorus compound represented by the following general formula (2) can also be used.

(In the general formula (2), R ⁴ is an optionally substituted alkyl group having 1 to 15 carbon atoms and an optionally substituted aryl group having 6 to 15 carbon atoms, and R ⁵ and Each R ⁶ independently represents a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, an optionally substituted alkenyl group having 2 to 15 carbon atoms, or an optionally substituted carbon; An alkynyl group having 2 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms which may be substituted, and R ⁵ and R ⁶ may be bonded to form a ring structure)

In this embodiment, in the general formula (2), R ⁴ is an optionally substituted alkyl group having 1 to 15 carbon atoms and an optionally substituted aryl group having 6 to 15 carbon atoms, R ⁵ and R ⁶ are each independently a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, an optionally substituted alkenyl group having 2 to 15 carbon atoms, and substituted. An alkynyl group having 2 to 15 carbon atoms or an optionally substituted aryl group having 6 to 15 carbon atoms, and R ⁵ and R ⁶ may be bonded to form a ring structure. . Among these, as R ⁵ and R ⁶ , from the viewpoint of suppressing gas generation, an alkenyl group having 2 to 15 carbon atoms which may be substituted or an alkynyl group having 2 to 15 carbon atoms which may be substituted may be used. Is preferred.

  Although it does not specifically limit as an alkyl group in the said General formula (2), For example, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group is mentioned. A hydrogen atom or a carbon atom in these alkyl groups may be substituted with a different element or substituent as necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. The substituent is not particularly limited, and examples thereof include ethyl, propyl, butyl, pentyl, phenyl, cyano, nitro, hydroxy, carboxy, sulfo, phosphono, and ether groups. , Sulfide groups, carbonyl groups, and sulfonyl groups. The number of carbon atoms of the alkyl group is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, and still more preferably 2 or more and 6 or less, from the viewpoint of suppressing gas generation. Examples of the organic phosphorus compound represented by the general formula (2) having an alkyl group include bis (2-propenyl) ethylphosphonate, bis (2-propenyl) propylphosphonate, bis (2-propenyl) butylphosphonate, bis (2-propenyl) pentylphosphonate, bis (2-propenyl) hexylphosphonate, bis (2-propynyl) ethylphosphonate, bis (2-propynyl) propylphosphonate, bis (2-propynyl) butylphosphonate, bis (2-propynyl) Examples include pentyl phosphonate and bis (2-propynyl) hexyl phosphonate.

  Although it does not specifically limit as an aryl group in the said General formula (2), For example, a phenyl group, 1-naphthyl group, 2-naphthyl group, a benzyl group etc. are mentioned. A hydrogen atom or a carbon atom in these aryl groups may be substituted with a different element or substituent as necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. The substituent is not particularly limited, and examples thereof include ethyl, propyl, butyl, pentyl, cyano, nitro, hydroxy, carboxy, sulfo, phosphono, ether, and sulfide groups. , A carbonyl group, and a sulfonyl group. The number of carbon atoms of the aryl group is preferably 6 or more and 10 or less, more preferably 6 or more and 8 or less, and still more preferably 6 or more and 7 or less, from the viewpoint of suppressing gas generation. Examples of the organic phosphorus compound represented by the general formula (2) having an aryl group include bis (2-propenyl) phenylphosphonate and bis (2-propynyl) phenylphosphonate.

  The alkenyl group in the general formula (2) is not particularly limited, and examples thereof include ethenyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, and benzyl group. Can be mentioned. The hydrogen atom or carbon atom in these alkenyl groups may be substituted with a different element or a substituent, if necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. Examples of the substituent include, but are not limited to, ethyl group, propyl group, butyl group, pentyl group, phenyl group, cyano group, nitro group, hydroxy group, carboxy group, sulfo group, phosphono group, ether group, sulfide. A group, a carbonyl group, and a sulfonyl group. The carbon number of the alkenyl group is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, and further preferably 2 or more and 6 or less, from the viewpoint of suppressing gas generation. Examples of the organic phosphorus compound represented by the general formula (2) having an alkenyl group include bis (2-propenyl) ethylphosphonate, bis (2-propenyl) propylphosphonate, bis (2-propenyl) butylphosphonate, bis (2-propenyl) pentylphosphonate, bis (2-propenyl) hexylphosphonate, bis (2-propenyl) phenylphosphonate.

  Although it does not specifically limit as an alkynyl group in the said General formula (2), For example, an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, a decynyl group is mentioned. In these alkynyl groups, a hydrogen atom or a carbon atom may be substituted with a different element or a substituent, if necessary. Although it does not specifically limit as said dissimilar element, For example, boron, silicon, nitrogen, sulfur, a fluorine, chlorine, a bromine can be mentioned. Examples of the substituent include, but are not limited to, ethyl group, propyl group, butyl group, pentyl group, phenyl group, cyano group, nitro group, hydroxy group, carboxy group, sulfo group, phosphono group, ether group, sulfide. A group, a carbonyl group, and a sulfonyl group. The number of carbon atoms of the alkynyl group is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, and further preferably 2 or more and 6 or less, from the viewpoint of suppressing gas generation. Examples of the organic phosphorus compound represented by the general formula (2) having an alkynyl group include bis (2-propynyl) ethyl phosphonate, bis (2-propynyl) propyl phosphonate, bis (2-propynyl) butyl phosphonate, bis (2 -Propynyl) pentylphosphonate, bis (2-propynyl) hexylphosphonate, bis (2-propynyl) phenylphosphonate.

R ⁴ is preferably an optionally substituted alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms, more preferably substituted, from the viewpoint of improving cycle characteristics. An alkyl group having 1 to 8 carbon atoms or an optionally substituted aryl group having 6 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 7 carbon atoms It is a group.

R ⁵ and R ⁶ are each independently a hydrogen atom, an optionally substituted alkyl group having 2 to 10 carbon atoms, or an optionally substituted carbon number of 2 to 10 from the viewpoint of improving cycle characteristics. The following alkenyl groups, optionally substituted alkynyl groups having 2 to 10 carbon atoms, or optionally substituted aryl groups having 6 to 10 carbon atoms are preferable, more preferably hydrogen atoms and substituted. An alkenyl group having 2 to 8 carbon atoms which may be substituted, or an alkynyl group having 2 to 8 carbon atoms which may be substituted, more preferably an alkenyl group having 2 to 6 carbon atoms or 2 carbon atoms. The alkynyl group is 6 or less. Among these, from the viewpoint of ease of synthesis, ethenyl group, ethynyl group, 2-propenyl group, 2-propynyl group, 2-butenyl group, 2-butynyl group, 3-butenyl group and 3-butynyl are particularly preferable. It is a group.

The content of the organophosphorus compound of the present embodiment is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, with respect to the total amount of the nonaqueous electrolytic solution. More preferably, it is 0.1 mass% or more and 4 mass% or less, More preferably, it is 0.2 mass% or more and 3 mass% or less. When the content of the organic phosphorus compound is 0.01% by mass or more, the cycle characteristic improving effect and the gas generation suppressing effect tend to be further improved. Moreover, when the content of the organic phosphorus compound is 10% by mass or less, the input / output characteristics tend to be further improved. The content of the organophosphorus compound in the non-aqueous electrolyte is easily measured by analyzing the non-aqueous electrolyte using techniques such as ³¹ P-NMR, ¹ H-NMR, and GC-MS. be able to.

[LiPO ₂ F ₂ ]
The non-aqueous electrolyte of this embodiment contains LiPO ₂ F ₂ . The LiPO ₂ F ₂ and the organophosphorus compound are each in a content of 0.001% by mass to 10% by mass and 0.01% by mass to 10% by mass with respect to the total amount of the non-aqueous electrolyte, The coexistence in the non-aqueous electrolyte is preferable from the viewpoint of further enhancing the gas generation suppression effect of the non-aqueous electrolyte. The role of LiPO ₂ F ₂ in this embodiment is not always clear. That is, the effect exhibited by the nonaqueous electrolytic solution of the present embodiment is not limited to the effect or principle described in this paragraph, but the organophosphorus compound acts on the positive electrode and / or the negative electrode to suppress decomposition of the electrolytic solution. A coating is formed on the electrode. At this time, the coexisting LiPO ₂ F ₂ is taken into the film, so that it grows into a stronger film, and it is considered that gas generation is more effectively suppressed.

The content of the LiPO ₂ F ₂ is preferably 0.001% by mass or more and 10% by mass or less, and 0.01% by mass or more and 5% by mass or less with respect to the total amount of the non-aqueous electrolyte from the viewpoint of suppressing gas generation. Is more preferable, and 0.1 mass% or more and 3 mass% or less are still more preferable. The content of LiPO ₂ F _{2 in} the non-aqueous electrolyte is easily measured by analyzing the non-aqueous electrolyte using a technique such as ³¹ P-NMR, ¹⁹ F-NMR, or ion chromatography. be able to.

[Nonaqueous solvent]
The nonaqueous electrolytic solution of the present embodiment contains a nonaqueous solvent. The non-aqueous solvent is not particularly limited and various solvents can be used, but an aprotic polar solvent is preferable. The aprotic polar solvent is not particularly limited. For example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, trifluoromethyl ethylene carbonate, fluoroethylene. Cyclic carbonates such as carbonate and 4,5-difluoroethylene carbonate; lactones such as γ-butyrolactone and γ-valerolactone; sulfones such as sulfolane; sulfites such as ethylene sulfite and 1,3-propane sultone; tetrahydrofuran and Cyclic ethers such as dioxane; ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl iso Chain carbonates such as probil carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate and methyl trifluoroethyl carbonate; nitriles such as acetonitrile and propionitrile; chain ethers such as dimethyl ether and dimethoxyethane And chain carboxylic acid esters such as methyl acetate and methyl propionate. These can be used individually by 1 type or in combination of 2 or more types.

  As the non-aqueous solvent, it is preferable to use a carbonate solvent obtained by mixing a cyclic carbonate and a chain carbonate at a specific ratio. When mixing the cyclic carbonate and the chain carbonate, the mixing ratio of the cyclic carbonate and the chain carbonate is preferably 1:10 to 5: 1 by volume from the viewpoint of ion conductivity, and is preferably 1: 5 to 3 : 1 is more preferable, and 1: 3 to 2: 1 is more preferable. Although it does not specifically limit as a cyclic carbonate and various things can be used, For example, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate are preferable, and ethylene carbonate and propylene carbonate are more preferable. The chain carbonate is not particularly limited, and various types can be used. For example, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferable.

[Lithium electrolyte]
The non-aqueous electrolyte of this embodiment contains a lithium electrolyte. The lithium electrolyte is not particularly limited, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiSbF 6, LiFSO 3, LiCF 3 SO 3, LiN (SO 2 F) 2, LiN (SO 2 CF 3) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ CF ₂ CF ₃ ), LiPO ₂ F ₂ , Li ₂ PO ₃ F, LiPF ₃ (C ₃ F ₇ ) ₃ , LiB (CF ₃ ) ₄ , LiB (CN) ₄ , Li ₂ (C ₂ O ₄ ), LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ), LiAl (C ₂ O ₄ ) ₂ , LiAlF ₂ (C ₂ O ₄ ), LiP (C ₂ O ₄ ) ₃ , LiPF ₂ (C ₂ O ₄ ) ₂ , and LiPF ₄ (C ₂ O ₄ ). Among these, as the lithium electrolyte, in consideration of both cycle characteristics and input / output characteristics, LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF _{2 CF 3) 2, Li 2} PO 3 F, LiB (C 2 O 4) 2, LiBF 2 (C 2 O 4), LiP (C 2 O 4) 3, LiPF 2 (C 2 O 4) 2, LiPF It is preferable to use one or more lithium electrolytes selected from the group consisting of ₄ (C ₂ O ₄ ), and from the group consisting of LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ , LiN (SO ₂ CF ₃ ) _2. It is more preferable to use one or more selected lithium electrolytes, and it is more preferable to use LiPF ₆ .

  From the viewpoint of input / output characteristics, the content of the lithium electrolyte is preferably 3% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, and more preferably 7% by mass with respect to the total amount of the nonaqueous electrolytic solution. More preferably, the content is 20% by mass or less.

[Non-aqueous storage device]
The non-aqueous electrolyte of this embodiment is suitably used as an electrolyte for non-aqueous electricity storage devices. Here, the non-aqueous electricity storage device is a general term for an electricity storage device that does not use an aqueous solution as an electrolyte solution in the electricity storage device, and is not particularly limited. For example, a lithium secondary battery, a lithium ion secondary battery, a sodium secondary battery Sodium ion secondary battery, magnesium secondary battery, magnesium ion secondary battery, calcium secondary battery, calcium ion secondary battery, aluminum secondary battery, aluminum ion secondary battery, lithium ion capacitor, electric double layer capacitor, etc. Can be mentioned. Among these, from the viewpoint of practicality, a lithium secondary battery, a lithium ion secondary battery, and a lithium ion capacitor are preferable, and a lithium ion secondary battery is more preferable.

  The lithium ion secondary battery of the present embodiment includes a positive electrode, a negative electrode, and the non-aqueous electrolyte of the present embodiment, and the potential of the positive electrode when fully charged is not less than 4.4 V and not more than 5.0 V based on lithium. . Here, the “positive electrode potential at full charge” refers to a value obtained by adding the negative electrode potential at full charge to the charge voltage. For example, when graphite having a fully charged potential of about 0.05 V with respect to lithium is used alone as the negative electrode active material, when a battery comprising a positive electrode and a graphite negative electrode is fully charged at a charging voltage of 4.35 V, the potential of the positive electrode is It becomes about 4.4V on the basis of lithium. The potential of the positive electrode when fully charged can be easily specified using a triode cell. Specifically, when a three-electrode cell having a fully charged positive electrode as a working electrode, lithium metal as a reference electrode, and a fully charged negative electrode as a counter electrode is produced, the potential difference between the working electrode and the reference electrode is “full”. The potential of the positive electrode during charging ”.

  In the present embodiment, from the viewpoint of ensuring a sufficiently high level of the lithium standard of 4.4 V or higher as the potential of the positive electrode at the time of full charge, the positive electrode is a positive electrode active that absorbs and releases lithium ions at a potential of the lithium standard of 4.4 V or higher. It is preferable to contain a substance alone or in combination of two or more.

The positive electrode active material that occludes and releases lithium ions at a potential of 4.4 V or higher with respect to lithium is not particularly limited. However, from the viewpoint of the structural stability of the positive electrode active material, the general formula LiNi _x Co _y Ma _{1- x-y} O ₂ [Ma represents one or more selected from the group consisting of Mn and Al, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and x + y ≦ 1. A layered oxide positive electrode active material represented by the general formula: LiMn _2−x Mb _x O ₄ [Mb represents one or more selected from the group consisting of transition metals, and 0.2 ≦ x ≦ 0.7. Spinel oxide positive electrode active material represented _by]; Li 2 MCO ₃ and LiMdO ₂ [Mc and Md represents one or more members selected from the group consisting of independently transition metal. And a general formula zLi ₂ McO _3- (1-z) LiMdO ₂ [0.05 ≦ z ≦ 0.95. Li-excess layered oxide positive electrode active material represented by: LiMe _1-x Fe _x PO ₄ [Me represents one or more selected from the group consisting of Mn and Co, and 0 ≦ x ≦ 1. And Li ₂ MfPO ₄ F [Mf represents one or more selected from the group consisting of transition metals. And one or more positive electrode active materials selected from the group consisting of:

General formula LiNi _x Co _y Ma _1-xy O ₂ [Ma represents one or more selected from the group consisting of Mn and Al, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and x + y ≦ 1. As the layered oxide positive electrode active material represented by the following formula, LiNi _x Co _y Mn _1-xy O ₂ [0 ≦ x ≦ 1 and 0 ≦ y ≦ 1 from the viewpoint of structural stability, x + y ≦ 1. ] Or LiNi _x Co _y Al _1-xy O ₂ [0.7 ≦ x ≦ 1, where 0 ≦ y ≦ 0.3, and x + y ≦ 1. It is preferable to have a composition represented by More preferable compositions are LiCoO ₂ , LiNi _x Co _y Mn _1-xy O ₂ [0.3 ≦ x ≦ 1, 0 ≦ y ≦ 0.4, and x + y ≦ 1. And LiNi _0.85 Co _0.1 Al _0.05 O ₂ .

  A positive electrode for constituting a lithium ion secondary battery was prepared by adding an appropriate amount of a conductive additive such as acetylene black and a binder such as polyvinylidene fluoride to the above positive electrode active material, and preparing a positive electrode mixture. Is applied to a current collecting material such as an aluminum foil and then pressed, and then the positive electrode mixture layer is fixed onto the current collecting material. However, the method for manufacturing the positive electrode is not limited to the above-described examples.

  In this embodiment, as a negative electrode active material that can be used for a negative electrode for constituting a lithium ion secondary battery, lithium or a compound capable of occluding and releasing lithium ions can be used. The negative electrode active material is not particularly limited. For example, an alloy compound such as Al, Si, or Sn, a metal oxide such as CuO or CoO, a lithium-containing compound such as lithium titanate, or a carbon material may be used. it can.

  As the negative electrode active material in the lithium ion secondary battery of the present embodiment, a carbon material capable of occluding and releasing lithium ions at a low potential is preferable from the viewpoint of improving the energy density of the battery. Such a carbon material is not particularly limited. For example, hard carbon, soft carbon, artificial graphite, natural graphite, pyrolytic carbon, coke, glassy carbon, a fired body of an organic polymer compound, firing of an organic natural product Body, carbon fiber, mesocarbon microbeads, carbon black. Although it does not specifically limit as said coke, For example, pitch coke, needle coke, and petroleum coke are mentioned. In addition, a fired body of an organic polymer compound refers to a carbon material obtained by firing a polymer material such as a phenol resin at an appropriate temperature, and a fired body of an organic natural product refers to a naturally derived material such as coffee husk. Refers to carbonized by firing at an appropriate temperature.

  When a carbon material is used for the negative electrode active material, the interlayer distance d002 of the (002) plane of the carbon material is preferably 0.37 nm or less, more preferably 0.35 nm or less, and further preferably 0.34 nm or less. is there. The lower limit of d002 is not particularly limited, but is theoretically about 0.335 nm.

  Further, the size of the crystallite in the c-axis direction of the carbon material is preferably 3 nm or more, more preferably 8 nm or more, and further preferably 25 nm or more. The upper limit of the crystallite is not particularly limited, but is usually about 200 nm. And the average particle diameter of a carbon material becomes like this. Preferably they are 3 micrometers or more and 15 micrometers or less, More preferably, they are 5 micrometers or more and 13 micrometers or less. Moreover, it is preferable that the purity is 99.9% or more.

  A negative electrode for constituting a lithium ion secondary battery was prepared by adding an appropriate amount of a thickener such as carboxymethyl cellulose and a binder such as styrene butadiene rubber to the above negative electrode active material, and preparing a negative electrode mixture. Is applied to a current collecting material such as a copper foil and then pressed, and then the negative electrode mixture layer can be fixed on the current collecting material. However, the method for manufacturing the negative electrode is not limited to the above-described examples.

  The lithium ion secondary battery of this embodiment preferably includes a separator between the positive electrode and the negative electrode from the viewpoint of providing safety such as prevention of short circuit between the positive and negative electrodes. The separator is not particularly limited, and various separators employed in conventionally known lithium ion secondary batteries can be used. For example, a polyolefin resin such as polyethylene or polypropylene; a polyester resin such as polyethylene terephthalate; a microporous film or a nonwoven fabric formed by molding a resin represented by a polyamide resin such as polyaramid is preferably used. From the viewpoint of imparting safety, the thickness of the separator is preferably 5 μm or more, and more preferably 10 μm or more. However, when the separator is thicker than necessary, the input / output characteristics of the battery are deteriorated. Therefore, the thickness of the separator is preferably 30 μm or less, and more preferably 20 μm or less.

  The lithium ion secondary battery of the present embodiment includes, for example, the above-described positive electrode and negative electrode that are overlapped via a separator and wound as necessary to obtain a laminated electrode body or a wound electrode body. Is attached to the exterior body, the positive and negative electrodes and the positive and negative terminals of the exterior body are connected via a lead body, and the nonaqueous electrolyte of the present embodiment is injected into the exterior body, and then the exterior body is sealed. Can be produced. Although it does not specifically limit as an exterior body of the said battery, The laminated container etc. which consist of metal can containers, a metal foil laminated film, etc. can be used conveniently. The shape of the lithium ion secondary battery is not particularly limited. For example, a cylindrical shape, a square shape, a coin shape, a flat shape, a sheet shape, or the like is adopted.

  The lithium ion secondary battery of this embodiment has high energy density and excellent practical durability, so it is widely used not only as a power source for mobile electronic devices such as mobile phones but also as a power source for various devices. be able to.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples, unless the summary is exceeded.

[Evaluation of the highest occupied orbital energy of organophosphorus compounds]
For the various organophosphorus compounds shown in Table 1, the maximum occupied orbit energy was calculated under the following conditions using the following commercially available software.
Software Fair: Gaussian Gaussian 09
Calculation method: Density functional theory (B3LYP)
Basis function: 6-31G + (d, p)
The energy value was optimized by self-sufficient landing field calculation. The calculation results are shown in Table 1.

  From Table 1, the general formula (1) is compared with a short-chain phosphate compound such as trimethyl phosphate or a polyfluorinated phosphate compound such as 2,2,2-trifluoroethylene phosphate. Alternatively, it was found that the highest occupied orbital energy of the organophosphorus compound represented by the general formula (2) is high and tends to be rich in reactivity on the electrode.

[Example 1]
1. Production of positive electrode LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (manufactured by Nippon Kagaku Kogyo Co., Ltd.) as a positive electrode active material, acetylene black powder (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive additive, and polyfluoride as a binder A vinylidene chloride solution (manufactured by Kureha Co., Ltd.) is mixed at a solid content mass ratio of 90: 6: 4, and N-methyl-2-pyrrolidone is added as a dispersion solvent to a solid content of 40% by mass and further mixed. Thus, a slurry solution was prepared. This slurry-like solution was applied to one side of an aluminum foil having a thickness of 20 μm, and the solvent was removed by drying, followed by rolling with a roll press to obtain a positive electrode.

2. Manufacture of negative electrode Graphite powder (manufactured by Osaka Gas Chemical Co., Ltd.) and graphite powder (manufactured by TIMCAL) as a negative electrode active material, styrene butadiene rubber and carboxymethyl cellulose aqueous solution as a binder, 90: 10: 1.5: 1.8 solid The mixture was mixed at a partial mass ratio, water was added as a dispersion solvent so as to have a solid content of 45% by mass, and further mixed to prepare a slurry solution. This slurry-like solution was applied to one side of a copper foil having a thickness of 18 μm, and after removing the solvent by drying, it was rolled with a roll press to obtain a negative electrode.

3. Preparation of non-aqueous electrolyte solution To a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1: 2, tripropyl phosphate (manufactured by Wako Pure Chemical Industries, Ltd.) is 0.3% by mass. Then, 12.1% by mass of LiPF ₆ and 0.2% by mass of LiPO ₂ F ₂ were added and mixed to obtain a non-aqueous electrolyte.

4). Production of test battery The positive electrode and the negative electrode produced as described above were superimposed on both sides of a separator made of a microporous membrane made of polypropylene (film thickness 25 μm, porosity 50%, pore diameter 0.1 μm to 1 μm). The laminated body was inserted into a bag made of a laminate film in which both surfaces of an aluminum foil (thickness: 40 μm) were coated with a resin layer while projecting positive and negative terminals, and then prepared as described above. The liquid was poured into the bag and vacuum sealed to produce a sheet-like lithium ion secondary battery.

5. Evaluation of Test Battery 5-1: Initial Charging / Discharging After charging the obtained sheet-like battery at a constant current of 0.05 C until reaching a voltage of 4.35 V in an environment of 25 ° C., a constant voltage of 4.35 V The battery was charged for 2 hours at a constant current of 0.2 C and discharged to 3.0 V. This was repeated for 3 cycles. Note that 1C represents a current value for discharging the reference capacity of the battery in one hour, and 0.05C represents a current value of 1/20.

5-2: Cycle test The battery after initial charge / discharge is charged at a constant current of 1C until reaching a voltage of 4.35V under an environment of 50 ° C, and then charged at a constant voltage of 4.35V for 1 hour. The battery was discharged at a constant current to 3.0V. The above series of charging / discharging was made into 1 cycle, this was implemented 100 cycles, and the capacity | capacitance maintenance factor was measured after 100 cycles. As a result, the capacity retention rate after 100 cycles was as high as 89%. The capacity retention rate after 100 cycles was determined by the following formula.
Capacity maintenance rate after 100 cycles (%) = (discharge capacity at the 100th cycle / discharge capacity at the first cycle) × 100

5-3: Gas generation test The battery after initial charge / discharge was immersed in a water bath and the volume was measured. After charging, the battery was charged at a constant current of 1 C until reaching a voltage of 4.35 V in an environment of 50 ° C. The battery was continuously charged at a constant voltage of 35V for one week and discharged to 3.0V at a constant current of 1C.
After the battery was cooled to room temperature, it was immersed in a water bath to measure the volume, and the amount of gas generated after continuous charging was determined from the volume change of the battery before and after continuous charging. As a result, the amount of gas generated after continuous charging was as low as 0.30 mL.

[Example 2]
A sheet-like battery was prepared in the same manner as in Example 1 except that tris (2-propenyl) phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of tripropyl phosphate in the preparation of the nonaqueous electrolytic solution of Example 1. And the above cycle test and gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 91%, and the amount of gas generated after continuous charging was as small as 0.15 mL.

[Example 3]
1. Synthesis of bis (2-propenyl) hexyl phosphonate Under a nitrogen atmosphere, 1.20 g of 2-propen-1-ol (manufactured by Tokyo Chemical Industry Co., Ltd.) and triethylamine (Wako Pure Chemical Industries, Ltd.) were placed in a 100 mL eggplant flask equipped with a dropping funnel. 2.3 g) and 50 mL of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) were added, and 2.0 g of hexylphosphonic dichloride (manufactured by Aldrich) was added dropwise from a dropping funnel while cooling the flask with ice. After the dropwise addition, the mixture was returned to room temperature for 2 hours while stirring with ice and stirred for 12 hours, the reaction solution was filtered, and the filtrate was distilled off under reduced pressure. The remaining solution was distilled under reduced pressure to obtain 1.99 g (yield 83%) of bis (2-propenyl) hexylphosphonate.

The obtained product was identified by ¹ H-NMR (JNM-GSX400G, manufactured by JEOL Ltd.). Deuterated chloroform was used as the measurement solvent, and tetramethylsilane was used as 0 ppm as the reference substance.
The chemical shift of the product is shown below.
0.89ppm (3H, t)
1.29 ppm (6H, m)
1.65 ppm (2H, quin)
1.85 ppm (2H, td)
4.45 ppm (4H, m)
5.33 ppm (2H, m)
5.46 ppm (2H, dd)
6.21 ppm (2H, m)

2. Preparation of Non-Aqueous Electrolyte Example 1 except that bis (2-propenyl) hexylphosphonate obtained as described above was used instead of tripropyl phosphate in the preparation of the non-aqueous electrolyte of Example 1. In the same manner as above, a sheet-like battery was produced, and the cycle test and the gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 89%, and the amount of gas generated after continuous charging was as small as 0.17 mL.

[Example 4]
1. Synthesis of tris (2-propynyl) phosphate In a 100 mL eggplant flask equipped with a dropping funnel under a nitrogen atmosphere, 1.16 g of 2-propin-1-ol (manufactured by Tokyo Chemical Industry Co., Ltd.), 2.3 g of triethylamine, 50 mL of tetrahydrofuran Then, 1.51 g of phosphorus oxychloride (manufactured by Wako Pure Chemical Industries, Ltd.) was dropped from the dropping funnel while cooling the flask with ice. After the dropwise addition, the mixture was returned to room temperature for 2 hours while stirring with ice and stirred for 12 hours, the reaction solution was filtered, and the filtrate was distilled off under reduced pressure. The remaining solution was distilled under reduced pressure to obtain 1.78 g of tris (2-propynyl) phosphate (yield 85%).

The obtained product was identified by ¹ H-NMR. Deuterated chloroform was used as the measurement solvent, and tetramethylsilane was used as 0 ppm as the reference substance.
The chemical shift of the product is shown below.
2.62 ppm (3H, t)
4.72 ppm (6H, dd)

2. Preparation of non-aqueous electrolyte Example 1 except that tris (2-propynyl) phosphate obtained as described above was used in place of tripropyl phosphate in preparation of the non-aqueous electrolyte of Example 1. In the same manner as above, a sheet-like battery was produced, and the cycle test and the gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 92%, and the amount of gas generated after continuous charging was as small as 0.14 mL.

[Example 5]
1. Synthesis of bis (2-propynyl) hexylphosphonate Under a nitrogen atmosphere, 1.16 g of 2-propyn-1-ol, 2.3 g of triethylamine, and 50 mL of tetrahydrofuran were added to a 100 mL eggplant flask equipped with a dropping funnel, and the flask was iced. While cooling, 2.0 g of hexylphosphonic dichloride (manufactured by Aldrich) was dropped from the dropping funnel. After the dropwise addition, the mixture was returned to room temperature for 2 hours with ice cooling and stirred for 12 hours, the reaction solution was filtered, and the filtrate was distilled off under reduced pressure. The remaining solution was distilled under reduced pressure to obtain 1.98 g of bis (2-propynyl) hexylphosphonate (yield 83%).

The obtained product was identified by ¹ H-NMR. Deuterated chloroform was used as the measurement solvent, and tetramethylsilane was used as 0 ppm as the reference substance.
The chemical shift of the product is shown below.
0.89ppm (3H, t)
1.29 ppm (6H, m)
1.65 ppm (2H, quin)
1.85 ppm (2H, td)
2.57 ppm (2H, t)
4.68 ppm (4H, dd)

2. Preparation of Nonaqueous Electrolytic Solution Example 1 except that in the preparation of the nonaqueous electrolytic solution of Example 1, bis (2-propynyl) hexylphosphonate obtained as described above was used instead of tripropyl phosphate. In the same manner as above, a sheet-like battery was produced, and the cycle test and the gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 91%, and the amount of gas generated after continuous charging was as small as 0.16 mL.

[Example 6]
1. Synthesis of bis (2-propynyl) phenylphosphonate Under a nitrogen atmosphere, a 100 mL eggplant flask equipped with a dropping funnel was charged with 1.20 g of 2-propyn-1-ol, 2.3 g of triethylamine, and 50 mL of tetrahydrofuran, and the flask was iced. While cooling, 2.0 g of phenylphosphonic dichloride (manufactured by Aldrich) was dropped from the dropping funnel. After the dropwise addition, the mixture was returned to room temperature for 2 hours while stirring with ice and stirred for 12 hours, the reaction solution was filtered, and the filtrate was distilled off under reduced pressure. The remaining solution was distilled under reduced pressure to obtain 2.02 g (yield 85%) of bis (2-propynyl) phenylphosphonate.

The obtained product was identified by ¹ H-NMR. Deuterated chloroform was used as the measurement solvent, and tetramethylsilane was used as 0 ppm as the reference substance.
The chemical shift of the product is shown below.
2.54 ppm (2H, t)
4.74 ppm (4H, dd)
7.49 ppm (2H, t)
7.58 ppm (1H, t)
7.84 ppm (2H, dd)

2. Preparation of Nonaqueous Electrolytic Solution Example 1 except that bis (2-propynyl) phenylphosphonate obtained as described above was used in place of tripropyl phosphate in the preparation of the nonaqueous electrolytic solution of Example 1. In the same manner as above, a sheet-like battery was produced, and the cycle test and the gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 88%, and the amount of gas generated after continuous charging was as small as 0.18 mL.

[Example 7]
1. Synthesis of Octylethylene Phosphate 2.100 g of 1-octanol (manufactured by Wako Pure Chemical Industries, Ltd.), 2.63 g of triethylamine, and 80 mL of tetrahydrofuran were put into a 100 mL eggplant flask equipped with a dropping funnel under a nitrogen atmosphere, and the flask was iced. While cooling, 2.84 g of 2-chloro-2-oxo-1,3,2-dioxaphosphorane (manufactured by Tokyo Chemical Industry Co., Ltd.) was dropped from the dropping funnel. After the dropwise addition, the mixture was returned to room temperature for 2 hours while stirring with ice and stirred for 12 hours, the reaction solution was filtered, and the filtrate was distilled off under reduced pressure. The remaining solution was distilled under reduced pressure to obtain 1.67 g (yield 36%) of octylethylene phosphate.

The obtained product was identified by ¹ H-NMR. Deuterated chloroform was used as the measurement solvent, and tetramethylsilane was used as 0 ppm as the reference substance.
The chemical shift of the product is shown below.
0.92 ppm (3H, t)
1.31 ppm (12H, m)
1.72 ppm (2H, td)
4.28 ppm (4H, m)

2. Preparation of Nonaqueous Electrolytic Solution In the preparation of the nonaqueous electrolytic solution of Example 1, the same procedure as in Example 1 was performed except that octylethylene phosphate obtained as described above was used instead of tripropyl phosphate. A sheet battery was prepared, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as high as 89%, and the amount of gas generated after continuous charging was as small as 0.23 mL.

[Example 8]
1. Synthesis of 3-butynylethylene phosphate In a 100 mL eggplant flask equipped with a dropping funnel in a nitrogen atmosphere, 1.54 g of 3-butyn-1-ol (manufactured by Tokyo Chemical Industry Co., Ltd.), 2.90 g of triethylamine, tetrahydrofuran 50 mL was added, and 2.84 g of 2-chloro-2-oxo-1,3,2-dioxaphospholane was added dropwise from a dropping funnel while cooling the flask with ice. After the dropwise addition, the mixture was returned to room temperature for 2 hours while stirring with ice and stirred for 12 hours, the reaction solution was filtered, and the filtrate was distilled off under reduced pressure. The remaining solution was distilled under reduced pressure to obtain 2.43 g (yield 69%) of 3-butynylethylene phosphate.

The obtained product was identified by ¹ H-NMR. Deuterated chloroform was used as the measurement solvent, and tetramethylsilane was used as 0 ppm as the reference substance.
The chemical shift of the product is shown below.
2.08ppm (1H, t)
2.62 ppm (2H, q)
4.18 ppm (2H, td)
4.30ppm (4H, m)

2. Preparation of Nonaqueous Electrolytic Solution In the preparation of the nonaqueous electrolytic solution of Example 1, Example 1 was used except that 3-butynylethylene phosphate obtained as described above was used instead of tripropyl phosphate. Similarly, a sheet battery was prepared, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as high as 90%, and the amount of gas generated after continuous charging was as small as 0.17 mL.

[Example 9]
In the preparation of the non-aqueous electrolyte of Example 1, a sheet shape was obtained in the same manner as in Example 1 except that 1% by mass of tris (2-propenyl) phosphate was used instead of 0.3% by mass of tripropyl phosphate. A battery was prepared, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as high as 90%, and the amount of gas generated after continuous charging was as small as 0.14 mL.

[Example 10]
In the preparation of the nonaqueous electrolytic solution of Example 1, a sheet shape was obtained in the same manner as in Example 1 except that 3% by mass of tris (2-propenyl) phosphate was used instead of 0.3% by mass of tripropyl phosphate. A battery was prepared, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as high as 84%, and the amount of gas generated after continuous charging was as small as 0.12 mL.

[Example 11]
In the preparation of the nonaqueous electrolytic solution of Example 2, a sheet-like battery was produced in the same manner as in Example 2, except that the amount of LiPO ₂ F ₂ added was changed from 0.2% by mass to 0.1% by mass. The cycle test and gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as high as 90%, and the amount of gas generated after continuous charging was as small as 0.17 mL.

[Example 12]
In the preparation of the nonaqueous electrolytic solution of Example 2, a sheet-like battery was produced in the same manner as in Example 2, except that the amount of LiPO ₂ F ₂ added was changed from 0.2% by mass to 0.5% by mass. The cycle test and gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as high as 85%, and the amount of gas generated after continuous charging was as low as 0.20 mL.

[Example 13]
In the preparation of the nonaqueous electrolytic solution of Example 1, a sheet-like battery was produced in the same manner as in Example 1 except that LiBF ₄ 7.5% by mass was used instead of LiPF ₆ 12.1% by mass. A cycle test and a gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 89%, and the amount of gas generated after continuous charging was as low as 0.28 mL.

[Comparative Example 1]
12.1% by mass of LiPF ₆ was added to a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 1: 2 to obtain a nonaqueous electrolytic solution. In the production of the test battery of Example 1, a sheet-like battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte was used, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as low as 76%, and the amount of gas generated after continuous charging was as large as 0.54 mL.

[Comparative Example 2]
To a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 1: 2, LiPF ₆ was added at 12.1% by mass and LiPO ₂ F ₂ was added at 0.2% by mass. A water electrolyte was used. In the production of the test battery of Example 1, a sheet-like battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte was used, and a cycle test and a gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as low as 85%, and the amount of gas generated after continuous charging was as large as 0.48 mL.

[Comparative Example 3]
5% by mass of tris (2-propenyl) phosphate and 12.1% by mass of LiPF ₆ were added to a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2. Thus, a non-aqueous electrolyte was obtained. In the production of the test battery of Example 1, a sheet-like battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte was used, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as very low as 68%, and the amount of gas generated after continuous charging was as large as 0.37 mL.

[Comparative Example 4]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, tris (2-propynyl) phosphate was 0.3% by mass, and LiPF ₆ was 12.1% by mass. A non-aqueous electrolyte was added. In the production of the test battery of Example 1, a sheet-like battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte was used, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as low as 86%, and the amount of gas generated after continuous charging was as large as 0.21 mL.

[Comparative Example 5]
Volume of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) ratio of 1: a solvent mixture at 2, trimethyl phosphate (manufactured by Wako Pure Chemical Industries Ltd.) and 0.3 wt%, the LiPF ₆ 12. 1% by mass and 0.2% by mass of LiPO ₂ F ₂ were added to obtain a non-aqueous electrolyte. In the production of the test battery of Example 1, a sheet-like battery was produced in the same manner as in Example 1 except that the non-aqueous electrolyte was used, and the cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as low as 85%, and the amount of gas generated after continuous charging was as large as 0.42 mL.

[Comparative Example 6]
A sheet battery was prepared in the same manner as in Example 1 except that 0.3% by mass of triphenyl phosphate was used instead of 0.3% by mass of tripropyl phosphate in the preparation of the nonaqueous electrolytic solution of Example 1. The cycle test and the gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as low as 86%, and the amount of gas generated after continuous charging was as large as 0.38 mL.

Table 2 shows the results obtained in Examples 1 to 13 and Comparative Examples 1 to 6. From Table 2, the lithium ion secondary batteries of Examples 1 to 13 were prepared by comparing Comparative Example 1 using a non-aqueous electrolyte not containing an organic phosphorus compound and LiPO ₂ F ₂ and a non-aqueous electrolyte containing no organic phosphorus compound. Comparative Example 2 used, Comparative Examples 3 to 4 using a non-aqueous electrolyte not containing LiPO ₂ F ₂ , Comparative Example 5 using an organic phosphorus compound having a maximum occupied orbital energy of −8 eV or less, and the highest occupied As compared with Comparative Example 6 using an organophosphorus compound having an orbital energy of −7 eV or more, it was revealed that cycle characteristics were improved and gas generation was suppressed. From the above, the above-described effect of the nonaqueous electrolytic solution of the present embodiment is obtained when an organic phosphorus compound having a maximum occupied orbital energy of −8 eV or more and −7 eV or less and LiPO ₂ F ₂ coexist in the nonaqueous electrolytic solution. It was shown that this is a unique effect.

  The lithium ion secondary battery using the non-aqueous electrolyte of the present invention has industrial applicability in various consumer equipment power supplies and automobile power supplies.

Claims (9)

A non-aqueous solvent, a lithium electrolyte, LiPO ₂ F _2, and an organophosphorus compound having a maximum occupied orbital energy calculated by density functional calculation of −8.0 eV or more and −7.0 eV or less. , Non-aqueous electrolyte. The nonaqueous electrolytic solution according to claim 1, wherein the organophosphorus compound includes an organophosphorus compound represented by the following general formula (1) and / or an organophosphorus compound represented by the following general formula (2). .

(In the general formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, and an optionally substituted carbon. An alkenyl group having 2 to 15 carbon atoms, an alkynyl group having 2 to 15 carbon atoms which may be substituted, or an aryl group having 6 to 15 carbon atoms which may be substituted; R ¹ , R ² , And at least two of R ³ may be bonded to form a ring structure.)

(In the above general formula (2), R ⁴ is an optionally substituted alkyl group having 1 to 15 carbon atoms or an optionally substituted aryl group having 6 to 15 carbon atoms, and R ⁵ and Each R ⁶ independently represents a hydrogen atom, an optionally substituted alkyl group having 2 to 15 carbon atoms, an optionally substituted alkenyl group having 2 to 15 carbon atoms, or an optionally substituted carbon; An alkynyl group having 2 to 15 carbon atoms, or an aryl group having 6 to 15 carbon atoms which may be substituted, and R ⁵ and R ⁶ may be bonded to form a ring structure.   The non-aqueous electrolyte according to claim 1, wherein the content of the organic phosphorus compound is 0.01% by mass or more and 10% by mass or less with respect to the total amount of the non-aqueous electrolyte. . The content of the LiPO ₂ F ₂ is the relative amount of non-aqueous electrolyte is not more than 0.001 mass% to 10 mass%, the non-aqueous electrolyte according to any one of claims 1 to 3 liquid. The lithium electrolyte includes at least one selected from the group consisting of LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ , and LiN (SO ₂ CF ₃ ) _2. The non-aqueous electrolyte described in 1. R ¹ , R ² , and R ^{3 in} the general formula (1), and R ⁵ and R ⁶ in the general formula (2) are each independently 2 to 15 carbon atoms that may be substituted. The nonaqueous electrolytic solution according to any one of claims 2 to 5, which is the following alkenyl group or an optionally substituted alkynyl group having 2 to 15 carbon atoms.   The nonaqueous electrolytic solution according to any one of claims 1 to 6, wherein the nonaqueous solvent contains one or more cyclic carbonates selected from the group consisting of ethylene carbonate, propylene carbonate, and fluoroethylene carbonate. R ¹ , R ² , and R ^{3 in} the general formula (1) and R ⁵ and R ⁶ in the general formula (2) are each independently ethenyl group, ethynyl group, 2-propenyl group, The nonaqueous electrolytic solution according to any one of claims 2 to 7, which is a 2-propynyl group, a 2-butenyl group, a 2-butynyl group, a 3-butenyl group, or a 3-butynyl group.   A positive electrode, a negative electrode, and the nonaqueous electrolytic solution according to any one of claims 1 to 8, wherein the potential of the positive electrode at full charge is 4.4 V or more and 5.0 V or less on a lithium basis. There is a lithium ion secondary battery.