JP6235313B2 - Non-aqueous electrolyte and lithium ion secondary battery using the non-aqueous electrolyte - Google Patents

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 the 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.

  By the way, in the 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 battery, since the carbonate solvent is decomposed, deposition of decomposition products and gas generation inside the battery occur, resulting in a problem that battery characteristics such as cycle characteristics deteriorate.

  In order to solve the above problem, Patent Document 2 proposes a method for improving the oxidation resistance of a nonaqueous electrolytic solution by using a fluorinated nonaqueous solvent as a nonaqueous solvent. Specifically, the oxidation resistance of the electrolytic solution is improved by using fluorinated ester and fluorinated ether at a high concentration of 50% by volume in total.

  Patent Documents 3 and 4 propose a method for improving the cycle performance and storage performance of a battery by including a specific cyclic phosphate in the nonaqueous electrolytic solution. Specifically, in Patent Document 3, the cycle characteristics are improved by containing 15% by volume of 2,2,2-trifluoroethylethylene phosphate as a fluorine-containing cyclic phosphate ester with respect to the non-aqueous solvent. I am trying. In Patent Document 4, 2-methoxy-1,3,2-phosphorane-2-oxide is used as a cyclic phosphate ester at a high concentration of 50% by volume with respect to the nonaqueous solvent, so that the battery can be stored at high temperature. The self-discharge at the time is suppressed.

International Publication No. 2008/114739 International Publication No. 2012/132976 JP 2013-157280 A Japanese Patent Laid-Open No. 10-50342

  However, when the fluorinated nonaqueous solvent disclosed in Patent Document 2 is used, the solubility of the lithium electrolyte in the nonaqueous solvent is lowered, and the ionic conductivity of the electrolytic solution is greatly lowered. As a result, the input / output characteristics of the battery are degraded, and as a result of the degradation of the input / output characteristics of the battery, the cycle characteristics may be degraded.

  Further, when 2,2,2-trifluoroethylethylene phosphate disclosed in Patent Document 3 is contained in a 15% by mass non-aqueous electrolyte with respect to the non-aqueous solvent, or disclosed in Patent Document 4. In the case where 2-methoxy-1,3,2-phosphorane-2-oxide is contained in a 50% by volume non-aqueous electrolyte with respect to the non-aqueous solvent, in a lithium ion secondary battery having a higher positive electrode potential than in the past, The effects of suppressing gas generation and improving cycle characteristics are not sufficient.

  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-described 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 electrolyte is suppressed, and cycle characteristics are improved. An object of the present invention is to provide a non-aqueous electrolyte solution that provides an excellent lithium-ion secondary battery and a lithium-ion secondary battery using the non-aqueous electrolyte solution.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have obtained a specific cyclic phosphate compound (A) and a lithium salt compound (B) having no oxalic acid structure in a non-aqueous solvent. And it discovered that the said subject could be solved by using the nonaqueous electrolyte solution which each contains 1 or more types of lithium salt compounds (C) which have an oxalic acid structure, and came to complete this invention.

That is, the present invention is as follows.
[1]
A cyclic phosphate compound (A) represented by the following general formula (1);
(In the formula (1), R ¹ is a hydroxy group, an optionally substituted alkoxy group having 1 to 15 carbon atoms, an optionally substituted alkyl group having 1 to 15 carbon atoms, and substituted. Or an alkynyl group having 2 to 15 carbon atoms which may be substituted, an alkynyl group having 2 to 15 carbon atoms which may be substituted, and an aryl group having 6 to 15 carbon atoms which may be substituted. It is a kind of group, and R ² is an optionally substituted alkylene group having 1 to 10 carbon atoms.)
A lithium salt compound (B) having no oxalic acid structure;
A lithium salt compound (C) having an oxalic acid structure;
A non-aqueous solvent ,
A nonaqueous electrolytic solution in which the content of the cyclic phosphate compound (A) is 0.01% by mass or more and 10% by mass or less with respect to the total amount of the nonaqueous electrolytic solution.
[2]
The content of the lithium salt compound (B) is 3% by mass or more and 30% by mass or less with respect to the total amount of the non-aqueous electrolyte,
The nonaqueous electrolytic solution according to [1] , wherein the content of the lithium salt compound (C) is 0.01% by mass or more and 10% by mass or less with respect to the total amount of the nonaqueous electrolytic solution.
[3]
The nonaqueous electrolytic solution according to [1] or [2] , wherein the lithium salt compound (B) contains LiPF ₆ .
[4]
The nonaqueous electrolytic solution according to any one of [1] to [3] , wherein the lithium salt compound (B) includes LiPF ₆ and LiPO ₂ F ₂ and / or LiBF ₄ .
[5]
The lithium salt compound (C) is 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 and LiPF ₄ (C _2. The nonaqueous electrolytic solution according to any one of [1] to [4] above, which contains one or more lithium salt compounds selected from the group consisting of ₂ O ₄ ).
[6]
In any one of [1] to [5] , the cyclic phosphate compound (A) includes a cyclic phosphate compound in which R ² in the general formula (1) is an ethylene group or a propylene group. The non-aqueous electrolyte described.
[7]
4. A positive electrode, a negative electrode, and the non-aqueous electrolyte solution according to any one of [1] to [6] above, wherein the potential of the positive electrode when fully charged is 4.4 V or more based on lithium. A lithium ion secondary battery having a voltage of 5 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, the generation of gas, that is, the decomposition of the electrolytic solution is suppressed, and a non-aqueous battery that provides a lithium ion secondary battery having excellent cycle characteristics is provided. A lithium ion secondary battery using the electrolytic solution and the non-aqueous electrolytic solution 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 nonaqueous electrolytic solution of the present embodiment has a cyclic phosphate compound (A) represented by the following general formula (1), a lithium salt compound (B) having no oxalic acid structure, and an oxalic acid structure. A lithium salt compound (C) and a non-aqueous solvent are contained. As a result, the nonaqueous electrolytic solution of the present embodiment suppresses gas generation, that is, decomposition of the electrolytic solution, even when applied to a lithium ion secondary battery having a higher positive electrode potential than the conventional one, and an excellent cycle. Characteristic can be expressed.
(In Formula (1), R ¹ is a hydroxy group, an optionally substituted alkoxy group having 1 to 15 carbon atoms, an optionally substituted alkyl group having 1 to 15 carbon atoms, and a substituted group. Or an alkynyl group having 2 to 15 carbon atoms which may be substituted, an alkynyl group having 2 to 15 carbon atoms which may be substituted, and an aryl group having 6 to 15 carbon atoms which may be substituted. It is a kind of group, and R ² is an optionally substituted alkylene group having 1 to 10 carbon atoms.)

[Cyclic phosphate ester compound (A)]
In the present embodiment, in general formula (1), R ¹ is a hydroxy group, an optionally substituted alkoxy group having 1 to 15 carbon atoms, or an optionally substituted alkyl group having 1 to 15 carbon atoms. 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, and an aryl group having 6 to 15 carbon atoms which may be substituted Represents a kind of group selected from the group consisting of

  The alkoxy group is not particularly limited, and examples thereof include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, a nonyloxy group, and a decyloxy group. The hydrogen atom or carbon atom of these alkoxy groups may be substituted with a different element or a 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 a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a phenyl group, a cyano group, a nitro group, a hydroxy group, a carboxy group, a sulfo group, and a phosphono group. , Ether groups, sulfide groups, carbonyl groups, and sulfonyl groups. Among these, from the viewpoint of more effectively suppressing gas generation, a fluorine atom, a hydroxy group, a carboxy group, a sulfo group, and a phosphono group are preferable, and a fluorine atom, a carboxy group, and a phosphono group are more preferable. The number of carbon atoms of the alkoxy group is 1 or more and 15 or less, preferably 1 or more and 10 or less, more preferably 1 or more and 8 or less, and further preferably 2 or more and 6 or less, from the viewpoint of suppressing gas generation. is there.

  Next, the alkyl group is not particularly limited, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. The hydrogen atom or carbon atom of these alkyl groups may be substituted with a different element or a 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. For example, methyl group, ethyl group, propyl group, butyl group, pentyl group, phenyl group, cyano group, nitro group, hydroxy group, carboxy group, sulfo group, phosphono group, ether Groups, sulfide groups, carbonyl groups and sulfonyl groups. Among these, from the viewpoint of more effectively suppressing gas generation, a fluorine atom, a hydroxy group, a carboxy group, a sulfo group, and a phosphono group are preferable, and a fluorine atom, a carboxy group, and a phosphono group are more preferable. The number of carbon atoms of the alkyl group is 1 or more and 15 or less, preferably 1 or more and 10 or less, more preferably 1 or more and 8 or less, and further preferably 2 or more and 6 or less from the viewpoint of suppressing gas generation. is there.

  The alkenyl group is not particularly limited, and examples thereof include an ethenyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, and a decenyl group. The hydrogen atom or carbon atom of 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. For example, methyl group, ethyl group, propyl group, butyl group, pentyl group, phenyl group, cyano group, nitro group, hydroxy group, carboxy group, sulfo group, phosphono group, ether Groups, sulfide groups, carbonyl groups and sulfonyl groups. Among these, from the viewpoint of more effectively suppressing gas generation, a fluorine atom, a hydroxy group, a carboxy group, a sulfo group, and a phosphono group are preferable, and a fluorine atom, a carboxy group, and a phosphono group are more preferable. The carbon number of the alkenyl group is 2 or more and 15 or less, 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. is there.

  The alkynyl group is not particularly limited, and examples thereof include an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, and a decynyl group. The hydrogen atom or carbon atom of these alkynyl groups may be substituted with a different element or a substituent as needed. 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. For example, methyl group, ethyl group, propyl group, butyl group, pentyl group, phenyl group, cyano group, nitro group, hydroxy group, carboxy group, sulfo group, phosphono group, ether Groups, sulfide groups, carbonyl groups and sulfonyl groups. Among these, from the viewpoint of more effectively suppressing gas generation, a fluorine atom, a hydroxy group, a carboxy group, a sulfo group, and a phosphono group are preferable, and a fluorine atom, a carboxy group, and a phosphono group are more preferable. The number of carbon atoms of the alkynyl group is 2 or more and 15 or less, 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. is there.

  Although it does not specifically limit as said aryl group, For example, a phenyl group, 1-naphthyl group, 2-naphthyl group, a benzyl group etc. are mentioned. The hydrogen atom or carbon atom of these aryl 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, methyl group, ethyl group, propyl group, butyl group, pentyl 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. Among these, from the viewpoint of more effectively suppressing gas generation, a fluorine atom, a hydroxy group, a carboxy group, a sulfo group, and a phosphono group are preferable, and a fluorine atom, a carboxy group, and a phosphono group are more preferable. The number of carbon atoms of the aryl group is 6 or more and 15 or less, preferably 6 or more and 10 or less, more preferably 6 or more and 8 or less, and further preferably 6 or more and 7 or less, from the viewpoint of suppressing gas generation. is there.

R ¹ is not particularly limited, but is preferably a hydroxy group, an optionally substituted alkoxy group having 1 to 10 carbon atoms, or an optionally substituted carbon number of 1 to 10 from the viewpoint of improving cycle characteristics. The following alkyl groups, optionally substituted alkenyl groups having 2 to 10 carbon atoms, optionally substituted alkynyl groups having 2 to 10 carbon atoms, and optionally substituted 6 to 10 carbon atoms A group selected from the group consisting of aryl groups, more preferably a hydroxy group, an optionally substituted alkoxy group having 1 to 8 carbon atoms, and an optionally substituted carbon group having 1 to 8 carbon atoms. An alkyl group having 2 to 8 carbon atoms which may be substituted, an alkynyl group having 2 to 8 carbon atoms which may be substituted, and A group selected from the group consisting of aryl groups having 6 to 8 carbon atoms, more preferably a hydroxy group, an alkoxy group having 2 to 6 carbon atoms, an alkyl group having 2 to 6 carbon atoms, It is a kind selected from the group consisting of an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, and an aryl group having 6 to 7 carbon atoms.

In this embodiment, R ² in the general formula (1) represents an optionally substituted alkylene group having 1 to 10 carbon atoms. Although it does not specifically limit as said alkylene group, For example, a methylene group, ethylene group, a propylene group, a butylene group, a pentylene group etc. can be mentioned. The hydrogen atom or carbon atom of these alkylene groups may be substituted with a different element or a substituent as needed. 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. For example, methyl group, ethyl group, propyl group, butyl group, pentyl group, phenyl group, cyano group, nitro group, hydroxy group, carboxy group, sulfo group, phosphono group, ether Groups, sulfide groups, carbonyl groups and sulfonyl groups. Among these, from the viewpoint of more effectively suppressing gas generation, a fluorine atom, a hydroxy group, a carboxy group, a sulfo group, and a phosphono group are preferable, and a fluorine atom, a carboxy group, and a phosphono group are more preferable. The number of carbon atoms of the alkylene group is 1 or more and 10 or less, preferably 1 or more and 8 or less, more preferably 1 or more and 5 or less, and further preferably 2 or more and 3 or less from the viewpoint of suppressing gas generation.

R ² is preferably an alkylene group having 1 to 5 carbon atoms which may be substituted from the viewpoint of more effectively suppressing gas generation, and may be an alkylene group having 2 to 3 carbon atoms which may be substituted. Is more preferable, and an ethylene group or a propylene group is more preferable.

  In the present embodiment, the content of the cyclic phosphate compound (A) is preferably 0.01% by mass or more based on the total amount of the nonaqueous electrolytic solution from the viewpoint of more effectively suppressing gas generation. More preferably, it is 0.1 mass% or more, More preferably, it is 0.3 mass% or more. From the viewpoint of input / output characteristics, the content of the cyclic phosphate ester compound (A) is preferably 10% by mass or less, more preferably 5% by mass or less, with respect to the total amount of the non-aqueous electrolyte. More preferably, it is 3% by mass or less.

  Although it does not specifically limit as cyclic phosphate ester compound (A) represented by General formula (1) in this embodiment, For example, a methylene methyl phosphonate, a methylene ethyl phosphonate, a methylene propyl phosphonate, a methylene butyl phosphonate, a methylene pentyl phosphonate Methylene hexyl phosphonate, methylene heptyl phosphonate, methylene octyl phosphonate, methylene ethenyl phosphonate, methylene (1-propenyl) phosphonate, methylene (2-propenyl) phosphonate, methylene (1-butenyl) phosphonate, methylene (2-butenyl) phosphonate, Methylene (3-butenyl) phosphonate, methylene (1-pentenyl) phosphonate, methylene (2-pentenyl) phosphonate, methylene (3-pentene Phosphonate, methylene (4-pentenyl) phosphonate, methylene ethynyl phosphonate, methylene (1-propynyl) phosphonate, methylene (2-propynyl) phosphonate, methylene (1-butynyl) phosphonate, methylene (2-butynyl) phosphonate, methylene ( 3-butynyl) phosphonate, methylene (1-pentynyl) phosphonate, methylene (2-pentynyl) phosphonate, methylene (3-pentynyl) phosphonate, methylene (4-pentynyl) phosphonate, methylene phenyl phosphonate, methylene benzyl phosphonate, ethylene methyl phosphonate, Ethylene ethyl phosphonate, ethylene propyl phosphonate, ethylene butyl phosphonate, ethylene pentyl phosphonate, ethylene hexyl phosphate Phonate, ethylene heptyl phosphonate, ethylene octyl phosphonate, ethylene ethenyl phosphonate, ethylene (1-propenyl) phosphonate, ethylene (2-propenyl) phosphonate, ethylene (1-butenyl) phosphonate, ethylene (2-butenyl) phosphonate, ethylene (3 -Butenyl) phosphonate, ethylene (1-pentenyl) phosphonate, ethylene (2-pentenyl) phosphonate, ethylene (3-pentenyl) phosphonate, ethylene (4-pentenyl) phosphonate, ethylene ethynyl phosphonate, ethylene (1-propynyl) phosphonate, ethylene (2-propynyl) phosphonate, ethylene (1-butynyl) phosphonate, ethylene (2-butynyl) phosphonate, ethylene (3-butynyl) phospho Sulfonate, ethylene (1-pentynyl) phosphonate, ethylene (2-pentynyl) phosphonate, ethylene (3-pentynyl) phosphonate, ethylene (4-pentynyl) phosphonate, ethylene phenyl phosphonate, ethylene benzyl phosphonate, propylene methyl phosphonate, propylene ethyl phosphonate, Propylene propyl phosphonate, propylene butyl phosphonate, propylene pentyl phosphonate, propylene hexyl phosphonate, propylene heptyl phosphonate, propylene octyl phosphonate, propylene ethenyl phosphonate, propylene (1-propenyl) phosphonate, propylene (2-propenyl) phosphonate, propylene (1-butenyl) ) Phosphonate, propylene (2-butenyl) phosphate Phonate, propylene (3-butenyl) phosphonate, propylene (1-pentenyl) phosphonate, propylene (2-pentenyl) phosphonate, propylene (3-pentenyl) phosphonate, propylene (4-pentenyl) phosphonate, propylene ethynylphosphonate, propylene (1- Propynyl) phosphonate, propylene (2-propynyl) phosphonate, propylene (1-butynyl) phosphonate, propylene (2-butynyl) phosphonate, propylene (3-butynyl) phosphonate, propylene (1-pentynyl) phosphonate, propylene (2-pentynyl) Phosphonate, propylene (3-pentynyl) phosphonate, propylene (4-pentynyl) phosphonate, propylene phenylphosphonate, propylene Benzyl phosphonate, methylene methyl phosphate, methylene ethyl phosphate, methylene propyl phosphate, methylene butyl phosphate, methylene pentyl phosphate, methylene hexyl phosphate, methylene heptyl phosphate, methylene octyl phosphate, methylene ethenyl phosphate, Methylene (1-propenyl) phosphate, methylene (2-propenyl) phosphate, methylene (1-butenyl) phosphate, methylene (2-butenyl) phosphate, methylene (3-butenyl) phosphate, methylene (1-pentenyl) ) Phosphate, methylene (2-pentenyl) phosphate, methylene (3-pentenyl) phosphate, methylene (4-pentenyl) phosphate , Methylene ethynyl phosphate, methylene (1-propynyl) phosphate, methylene (2-propynyl) phosphate, methylene (1-butynyl) phosphate, methylene (2-butynyl) phosphate, methylene (3-butynyl) phosphate Fate, methylene (1-pentynyl) phosphate, methylene (2-pentynyl) phosphate, methylene (3-pentynyl) phosphate, methylene (4-pentynyl) phosphate, methylene phenyl phosphate, methylene benzyl phosphate, ethylene methyl Phosphate, ethylene ethyl phosphate, ethylene propyl phosphate, ethylene butyl phosphate, ethylene pentyl phosphate, ethylene hexyl phosphate, ethyl Nheptyl phosphate, ethylene octyl phosphate, ethylene ethenyl phosphate, ethylene (1-propenyl) phosphate, ethylene (2-propenyl) phosphate, ethylene (1-butenyl) phosphate, ethylene (2-butenyl) phosphate Fate, ethylene (3-butenyl) phosphate, ethylene (1-pentenyl) phosphate, ethylene (2-pentenyl) phosphate, ethylene (3-pentenyl) phosphate, ethylene (4-pentenyl) phosphate, ethylene ethynyl phosphate Fate, ethylene (1-propynyl) phosphate, ethylene (2-propynyl) phosphate, ethylene (1-butynyl) phosphate, ethylene (2-butynyl) phosphate, ethyl (3-butynyl) phosphate, ethylene (1-pentynyl) phosphate, ethylene (2-pentynyl) phosphate, ethylene (3-pentynyl) phosphate, ethylene (4-pentynyl) phosphate, ethylene phenyl phosphate, ethylene Benzyl phosphate, propylene methyl phosphate, propylene ethyl phosphate, propylene propyl phosphate, propylene butyl phosphate, propylene pentyl phosphate, propylene hexyl phosphate, propylene heptyl phosphate, propylene octyl phosphate, propylene ethenyl phosphate, Propylene (1-propenyl) phosphate, propylene (2-propenyl) phosphate, propylene (1 -Butenyl) phosphate, propylene (2-butenyl) phosphate, propylene (3-butenyl) phosphate, propylene (1-pentenyl) phosphate, propylene (2-pentenyl) phosphate, propylene (3-pentenyl) phosphate , Propylene (4-pentenyl) phosphate, propylene ethynyl phosphate, propylene (1-propynyl) phosphate, propylene (2-propynyl) phosphate, propylene (1-butynyl) phosphate, propylene (2-butynyl) phosphate , Propylene (3-butynyl) phosphate, propylene (1-pentynyl) phosphate, propylene (2-pentynyl) phosphate, propylene (3-pentynyl) phosphate Propylene (4-pentynyl) phosphate, propylene phenyl phosphate, propylene benzyl phosphate.

[Lithium salt compound (B)]
The non-aqueous electrolyte of this embodiment contains a lithium salt compound (B) that does not have an oxalic acid structure. The “oxalic acid structure” refers to a chemical structure represented by the following general formula (2). In the present embodiment, it is also simply expressed as “C ₂ O ₄ ”.

The lithium salt compound (B) having no oxalic acid structure is not particularly limited as long as it is a lithium salt compound having no oxalic acid structure in the molecule. 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, can be cited LiB _{(CN) 4.} Among these, as the lithium salt compound (B), in consideration of both input / output characteristics and cycle characteristics, LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiPO ₂ F ₂ , Li ₂ PO ₃ F are preferably used alone or in combination of two or more, and LiPF ₆ and LiBF ₄ and / or LiPO are used. it is more preferable to use in combination with ₂ F _2.

  The content of the lithium salt compound (B) is preferably 3% by mass or more and 30% by mass or less, more preferably, with respect to the total amount of the non-aqueous electrolyte in consideration of both input / output characteristics and cycle characteristics. It is 5 mass% or more and 25 mass% or less, More preferably, it is 8 mass% or more and 20 mass% or less.

[Lithium salt compound (C)]
The nonaqueous electrolytic solution of the present embodiment contains a lithium salt compound (C) having an oxalic acid structure. Examples of the lithium salt compound having the oxalic acid structure (C), if a lithium salt compound having the oxalic acid structure in the molecule is not particularly limited, for _{example, 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, LiPF ₄ (C ₂ O ₄ ) can be mentioned. Among these, as the lithium salt compound (C), LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ), LiP () are considered in consideration of both solubility in a non-aqueous solvent and gas generation suppression. One or more selected from the group consisting of C ₂ O ₄ ) ₃ , LiPF ₂ (C ₂ O ₄ ) ₂ , and LiPF ₄ (C ₂ O ₄ ) are preferable, and LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ) is more preferred.

  The content of the lithium salt compound (C) is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass with respect to the total amount of the non-aqueous electrolyte, from the viewpoint of suppressing gas generation. % To 5% by mass, and more preferably 0.3% to 3% by mass.

  In the nonaqueous electrolytic solution of the present embodiment, the cyclic phosphate ester (A) and the lithium salt compound (C) are used in combination. From the viewpoint of further enhancing the gas generation suppressing effect (electrolytic solution decomposition suppressing effect) of the nonaqueous electrolytic solution of the present embodiment, the cyclic phosphate ester (A) and the lithium salt compound (C) are each converted to a nonaqueous electrolytic solution. On the other hand, it is preferable to make it coexist in a non-aqueous electrolyte solution with a content of 0.01 mass% or more and 10 mass% or less. Since the gas generation suppression effect is remarkably exhibited in the above concentration range, it is considered that the role of the lithium salt compound (C) is in reforming the positive electrode and the negative electrode rather than ensuring ionic conduction. The reason why the gas generation is remarkably suppressed is not necessarily clear. That is, the effect exhibited by the nonaqueous electrolytic solution of the present embodiment is not limited to the action or principle described in this paragraph, but the oxalic acid moiety contained in the lithium salt compound (C) and the cyclic phosphate ( It is considered that the cyclic structure part A) effectively suppresses gas generation by acting cooperatively on the positive electrode and the negative electrode.

[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 more preferably 1: It is 5-3: 1, More preferably, it is 1: 3-2: 1. 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.

  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.

[Lithium ion secondary battery]
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 5.5 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, a battery consisting of 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 about 4.4 V with respect to lithium. The potential of the positive electrode at full charge can be easily measured using a tripolar 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 ”.

[Positive electrode]
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.

(Positive electrode active material)
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. A spinel oxide positive electrode active material represented by: Li ₂ McO ₃ and LiMdO ₂ [Mc and Md each independently represents one or more selected from the group consisting of transition metals. 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 an olivine-type positive electrode active material represented by the formula: 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. From the viewpoint of structural stability, the layered oxide positive electrode active material represented by the formula: LiNi _x Co _y Mn _1-xy O ₂ [0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and x + y ≦ 1. ] Or LiNi _x Co _y Al _1-xy O ₂ [0.7 ≦ x ≦ 1, 0 ≦ y ≦ 0.3, and x + y ≦ 1. It is preferable to have a composition represented by More preferable compositions include LiCoO ₂ , LiNi _x Co _y Mn _1-xy O ₂ [0.4 ≦ x ≦ 1, 0 ≦ y ≦ 0.4, and x + y ≦ 1. And LiNi _0.85 Co _0.1 Al _0.05 O ₂ .

Formula _LiMn 2-x _Mb x _{O 4} [Mb represents at least one kind selected from the group consisting of transition metal, 0.2 ≦ x ≦ 0.7. The spinel oxide positive electrode active substance represented by], in view of structural _stability, it is _LiMn 2-x _Ni x _{O 4} [0.2 ≦ x ≦ 0.7. It is preferable to have a composition represented by As a more preferred composition, LiMn _1.5 Ni _0.5 O ₄ can be mentioned. From the viewpoint of structural stability, electronic conductivity, and the like, the spinel oxide further contains a transition metal or a transition metal oxide in addition to the above structure in a range of 30 mol% or less with respect to the number of moles of Mn atoms. be able to.

  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 pressurized, and then the positive electrode mixture layer can be fixed on the current collecting material. However, the method for manufacturing the positive electrode is not limited to the above-described examples.

[Negative electrode]
The negative electrode used for the lithium ion secondary battery of this embodiment contains a negative electrode active material.

(Negative electrode active material)
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; and 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 size 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.

[Separator]
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. On the other hand, from the viewpoint of maintaining the input / output characteristics of the battery, 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.

[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 binder As a dispersion solvent, a polyvinylidene fluoride 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. Further mixing was performed to prepare a slurry solution. 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: Production of negative electrode Graphite powder (manufactured by Osaka Gas Chemical Co., Ltd.) and graphite powder (manufactured by TIMCAL) as a negative electrode active material, and styrene-butadiene rubber and carboxymethylcellulose aqueous solution as a binder, 90: 10: 1.5: 1.8 Were mixed at a solid content mass ratio of water, water was added as a dispersion solvent so as to have a solid content of 45 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 In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, ethylene (3-butynyl) phosphate was 0.3% by mass; A nonaqueous electrolytic solution was prepared by adding and mixing LiPF ₆ (12.1% by mass) and LiB (C ₂ O ₄ ) ₂ (1% by mass).

4: Production of test battery The positive electrode and the negative electrode produced as described above were placed on both sides of a separator (thickness 25 μm, porosity 50%, pore diameter 0.1 μm to 1 μm) made of a polypropylene microporous film. The stacked laminate was inserted into a bag made of a laminate film in which both sides of an aluminum foil (thickness 40 μm) were covered with a resin layer while projecting positive and negative terminals, and then prepared as described above. A water electrolyte 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 charge / discharge 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. (Positive electrode potential = 4.4V) The battery was charged at a constant voltage of 4.35V for 2 hours and discharged to 3.0V at a constant current of 0.2C. 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 maintenance rate was measured after 100 cycles. As a result, the capacity retention rate after 100 cycles was as high as 90%. 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 small as 0.17 mL.

[Example 2]
A sheet battery was prepared in the same manner as in Example 1 except that ethylene (2-propynyl) phosphate was used instead of ethylene (3-butynyl) phosphate in the preparation of the nonaqueous electrolytic solution of Example 1. 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 low as 0.21 mL.

[Example 3]
A sheet-like battery was prepared in the same manner as in Example 1 except that ethylene (3-butenyl) phosphate was used instead of ethylene (3-butynyl) phosphate in the preparation of the nonaqueous electrolytic solution of Example 1. The cycle test and the gas generation test were conducted. 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 4]
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 ethylene hexyl phosphonate was used instead of ethylene (3-butynyl) phosphate. A gas generation test was 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 0.27 mL.

[Example 5]
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 ethylene octyl phosphate was used instead of ethylene (3-butynyl) phosphate. And a gas generation test was 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 0.23 mL.

[Example 6]
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 0.5% by mass of LiBF ₄ was further added to the mixed solvent, and the above cycle test and gas generation test were performed. Went. 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 0.17 mL.

[Example 7]
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 0.5% by mass of LiPO ₂ F ₂ was further added to the mixed solvent. A developmental test was performed. 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 0.15 mL.

[Example 8]
A sheet-like battery was produced in the same manner as in Example 1 except that LiPF ₂ (C ₂ O ₄ ) ₂ was used instead of LiB (C ₂ O ₄ ) ₂ in the preparation of the non-aqueous electrolyte of Example 1. The above cycle test and 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 0.19 mL.

[Example 9]
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 1% by mass was added instead of 0.3% by mass of ethylene (3-butynyl) phosphate. The above cycle test and 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 0.15 mL.

[Example 10]
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 3% by mass was added instead of 0.3% by mass of ethylene (3-butynyl) phosphate. The above cycle test and gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 86%, and the amount of gas generated after continuous charging was as small as 0.11 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]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1: 2, LiPF ₆ is 12.1% by mass, LiB (C ₂ O ₄ ) ₂ is 1% by mass, Was 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 a cycle test and a gas generation test were performed. As a result, the capacity retention rate after 100 cycles was as low as 88%, and the amount of gas generated after continuous charging was as large as 0.34 mL.

[Comparative Example 3]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, ethylene (3-butynyl) phosphate was 0.3% by mass, and LiPF ₆ was 12.1% by mass. To make 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 82%, and the amount of gas generated after continuous charging was as large as 0.28 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, LiPF ₆ was 12.1% by mass, LiBF ₄ was 0.5% by mass, and LiB (C ₂ 1 mass% of O ₄ ) ₂ was added to make 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 84%, and the amount of gas generated after continuous charging was as large as 0.32 mL.

[Comparative Example 5]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, LiPF ₆ was 12.1% by mass, LiPO ₂ F ₂ was 0.5% by mass, and LiB ( C ₂ O ₄ ) ₂ was added in an amount of 1% by mass 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 88%, and the amount of gas generated after continuous charging was as large as 0.28 mL.

[Comparative Example 6]
12.1 mass of LiPF ₆ in a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC) and 2,2,2-trifluoroethyl ethylene phosphate were mixed at a volume ratio of 42.5: 42.5: 15 % To make 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 79%, and the amount of gas generated after continuous charging was as large as 0.31 mL.

[Comparative Example 7]
To a mixed solvent in which 2-methoxy-1,3,2-dioxaphosphorane-2-oxide and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1, 12.1% by mass of LiPF ₆ was added and non-aqueous. An 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 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 58%, and the amount of gas generated after continuous charging was as low as 0.21 mL.

  Table 1 shows the results obtained in Examples 1 to 10 and Comparative Examples 1 to 7. From Table 1, all of the lithium ion secondary batteries of Examples 1 to 10 have Comparative Examples 2, 4, and 5 using a nonaqueous electrolytic solution that does not contain the cyclic phosphate ester (A), and an oxalic acid structure. It was revealed that the cycle characteristics were improved and the gas generation amount was reduced as compared with Comparative Example 3 using a non-aqueous electrolyte solution containing no lithium salt compound (C). From the above, the above-described effect of the nonaqueous electrolytic solution of the present embodiment is unique when the cyclic phosphate (A) and the lithium salt compound (C) having an oxalic acid structure coexist in the nonaqueous electrolytic solution. It was shown to be an effect.

  Moreover, all the lithium ion secondary batteries of Examples 1 to 10 contained 15% by volume of 2,2,2-trifluoroethylethylene phosphate described in Patent Document 3 with respect to the nonaqueous solvent. Compared to Comparative Example 6 and Comparative Example 7 containing 50% by volume of 2-methoxy-1,3,2-dioxaphosphorane-2-oxide described in Patent Document 4 with respect to the non-aqueous solvent It was clarified that the cycle characteristics were greatly improved and the gas generation amount was reduced.

[Example 11]
1: Manufacture of positive electrode active material Nickel sulfate and manganese sulfate at a molar ratio of transition metal element of 1: 3 are dissolved in water and mixed with nickel-manganese so that the total concentration of metal ions is 2 mol / L. An aqueous solution was prepared. Subsequently, this nickel-manganese mixed aqueous solution was dropped into 1650 mL of a 2 mol / L sodium carbonate aqueous solution heated to 70 ° C. at an addition rate of 12.5 mL / min for 120 minutes. In addition, at the time of dripping, air with a flow rate of 200 mL / min was bubbled into the aqueous solution while stirring. As a result, a precipitated substance was generated, and the obtained precipitated substance was sufficiently washed with distilled water and dried to obtain a nickel manganese compound. The obtained nickel-manganese compound and lithium carbonate having a particle size of 2 μm were weighed so that the molar ratio of lithium: nickel: manganese was 1: 0.5: 1.5, and obtained after dry-mixing for 1 hour. The obtained mixture was baked at 1000 ° C. for 5 hours in an oxygen atmosphere to obtain a positive electrode active material represented by LiNi _0.5 Mn _1.5 O ₄ .

2: Production of positive electrode A positive electrode active material obtained as described above, an acetylene black powder (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive auxiliary agent, and a polyvinylidene fluoride solution (manufactured by Kureha Co., Ltd.) as a binder, The mixture was mixed at a solid content mass ratio of 6: 6, N-methyl-2-pyrrolidone as a dispersion solvent was added so as to have a solid content of 40% by mass, and further mixed to prepare a slurry solution. 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.

3: Production of negative electrode Graphite powder (manufactured by Osaka Gas Chemical Company) 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: The mixture was mixed at a solid content mass ratio of 1.8, water was added as a dispersion solvent so as to have a solid content of 45 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.

4: Preparation of non-aqueous electrolyte In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, ethylene (3-butynyl) phosphate was 0.3% by mass; LiPF ₆ (12.1% by mass) and LiB (C ₂ O ₄ ) ₂ (1% by mass) were added to obtain a non-aqueous electrolyte.

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

6: Evaluation of test battery 6-1: Initial charge / discharge After charging the obtained sheet-like battery at a constant current of 0.05 C until reaching a voltage of 4.8 V in an environment of 25 ° C. (Positive electrode potential = 4.85V) The battery was charged at a constant voltage of 4.8V for 2 hours and discharged to 3.0V at a constant current of 0.2C. 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.

6-2: Cycle test The battery after initial charge / discharge is charged at a constant current of 1C until reaching a voltage of 4.8V under an environment of 50 ° C, and then charged at a constant voltage of 4.8V 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 maintenance rate was measured after 100 cycles. As a result, the capacity retention rate after 100 cycles was as high as 74%. 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

6-3: Gas generation test The battery after initial charge and 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 4.8 V in an environment of 50 ° C. The battery was continuously charged at a constant voltage of 8V 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 small as 1.16 mL.

[Example 12]
A sheet-like battery was prepared in the same manner as in Example 11 except that ethylene (2-propynyl) phosphate was used instead of ethylene (3-butynyl) phosphate in the preparation of the nonaqueous electrolytic solution of Example 11. The cycle test and the gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 70%, and the amount of gas generated after continuous charging was as small as 1.23 mL.

[Example 13]
A sheet-like battery was prepared in the same manner as in Example 11 except that ethylene (3-butenyl) phosphate was used instead of ethylene (3-butynyl) phosphate in the preparation of the nonaqueous electrolytic solution of Example 11. The cycle test and the gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 76%, and the amount of gas generated after continuous charging was as small as 1.14 mL.

[Example 14]
In the preparation of the nonaqueous electrolytic solution of Example 11, a sheet-like battery was prepared in the same manner as in Example 11 except that ethylenehexylphosphonate was used instead of ethylene (3-butynyl) phosphate, and the above cycle test and A gas generation test was conducted. As a result, the capacity retention rate after 100 cycles was as high as 69%, and the amount of gas generated after continuous charging was as small as 1.31 mL.

[Example 15]
In the preparation of the nonaqueous electrolytic solution of Example 11, a sheet-like battery was produced in the same manner as in Example 11 except that ethylene octyl phosphate was used instead of ethylene (3-butynyl) phosphate, and the above cycle test was performed. And a gas generation test was conducted. As a result, the capacity retention rate after 100 cycles was as high as 71%, and the amount of gas generated after continuous charging was as small as 1.27 mL.

[Example 16]
In the preparation of the nonaqueous electrolytic solution of Example 11, a sheet-like battery was produced in the same manner as in Example 11 except that 0.5% by mass of LiBF ₄ was further added to the mixed solvent, and the above cycle test and gas generation test were performed. Went. As a result, the capacity retention rate after 100 cycles was as high as 75%, and the amount of gas generated after continuous charging was as small as 1.15 mL.

[Example 17]
A sheet-like battery was produced in the same manner as in Example 11 except that LiPF ₂ (C ₂ O ₄ ) ₂ was used instead of LiB (C ₂ O ₄ ) ₂ in the preparation of the nonaqueous electrolytic solution of Example 11. The above cycle test and gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 72%, and the amount of gas generated after continuous charging was as small as 1.18 mL.

[Example 18]
In the preparation of the nonaqueous electrolytic solution of Example 11, a sheet-like battery was produced in the same manner as in Example 11 except that 1% by mass was added instead of 0.3% by mass of ethylene (3-butynyl) phosphate. The above cycle test and gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 73%, and the amount of gas generated after continuous charging was as low as 1.09 mL.

[Example 19]
In the preparation of the nonaqueous electrolytic solution of Example 11, a sheet-like battery was produced in the same manner as in Example 11 except that 3% by mass was added instead of 0.3% by mass of ethylene (3-butynyl) phosphate. The above cycle test and gas generation test were conducted. As a result, the capacity retention rate after 100 cycles was as high as 68%, and the amount of gas generated after continuous charging was as low as 1.01 mL.

[Comparative Example 8]
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 11, a sheet-like battery was produced in the same manner as in Example 11 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 32%, and the amount of gas generated after continuous charging was as large as 4.32 mL.

[Comparative Example 9]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1: 2, LiPF ₆ is 12.1% by mass, LiB (C ₂ O ₄ ) ₂ is 1% by mass, Was added to obtain a non-aqueous electrolyte. In the production of the test battery of Example 11, a sheet-like battery was produced in the same manner as in Example 11 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 64%, and the amount of gas generated after continuous charging was as large as 2.62 mL.

[Comparative Example 10]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, ethylene (3-butynyl) phosphate was 0.3% by mass, and LiPF ₆ was 12.1% by mass. To make a non-aqueous electrolyte. In the production of the test battery of Example 11, a sheet-like battery was produced in the same manner as in Example 11 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 52%, and the amount of gas generated after continuous charging was as high as 1.38 mL.

[Comparative Example 11]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, LiPF ₆ was 12.1% by mass, LiBF ₄ was 0.5% by mass, and LiB (C ₂ 1 mass% of O ₄ ) ₂ was added to make a non-aqueous electrolyte. In the production of the test battery of Example 11, a sheet-like battery was produced in the same manner as in Example 11 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 65%, and the amount of gas generated after continuous charging was as large as 2.61 mL.

[Comparative Example 12]
12.1 mass of LiPF ₆ in a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC) and 2,2,2-trifluoroethyl ethylene phosphate were mixed at a volume ratio of 42.5: 42.5: 15 % To make a non-aqueous electrolyte. In the production of the test battery of Example 11, a sheet-like battery was produced in the same manner as in Example 11 except that the non-aqueous electrolyte was used, and the cycle test and the gas generation test were performed. As a result, the capacity maintenance rate after 100 cycles was as low as 50%, and the amount of gas generated after continuous charging was as large as 1.32 mL.

[Comparative Example 13]
To a mixed solvent in which 2-methoxy-1,3,2-dioxaphosphorane-2-oxide and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1, 12.1% by mass of LiPF ₆ was added and non-aqueous. An electrolyte was used. In the production of the test battery of Example 11, a sheet-like battery was produced in the same manner as in Example 11 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 4%, and the amount of gas generated after continuous charging was as large as 2.21 mL.

  Table 2 shows the results obtained in Examples 11 to 19 and Comparative Examples 8 to 13. From Table 2, the lithium ion secondary batteries of Examples 11 to 19 are all Comparative Examples 9 and 11 using a nonaqueous electrolytic solution containing no cyclic phosphate (A), lithium salt compounds having an oxalic acid structure As compared with Comparative Example 10 using a non-aqueous electrolyte not containing (C), it was revealed that the cycle characteristics were improved and the gas generation amount was greatly reduced. From the above, it is shown that the effect of the present embodiment is a unique effect when the cyclic phosphate ester (A) and the lithium salt compound (C) having an oxalic acid structure coexist in the nonaqueous electrolytic solution. It was done.

  In addition, all of the lithium ion secondary batteries of Examples 11 to 19 contained 15% by volume of 2,2,2-trifluoroethylethylene phosphate described in Patent Document 3 with respect to the nonaqueous solvent. Compared to Comparative Example 13 and Comparative Example 13 containing 50% by volume of 2-methoxy-1,3,2-dioxaphosphorane-2-oxide described in Patent Document 4 with respect to the non-aqueous solvent It was clarified that the cycle characteristics were greatly improved and the gas generation amount was reduced.

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

Claims (7)

A cyclic phosphate compound (A) represented by the following general formula (1);
(In the formula (1), R ¹ is a hydroxy group, an optionally substituted alkoxy group having 1 to 15 carbon atoms, an optionally substituted alkyl group having 1 to 15 carbon atoms, and substituted. Or an alkynyl group having 2 to 15 carbon atoms which may be substituted, an alkynyl group having 2 to 15 carbon atoms which may be substituted, and an aryl group having 6 to 15 carbon atoms which may be substituted. It is a kind of group, and R ² is an optionally substituted alkylene group having 1 to 10 carbon atoms.)
A lithium salt compound (B) having no oxalic acid structure;
A lithium salt compound (C) having an oxalic acid structure;
A non-aqueous solvent ,
A nonaqueous electrolytic solution in which the content of the cyclic phosphate compound (A) is 0.01% by mass or more and 10% by mass or less with respect to the total amount of the nonaqueous electrolytic solution. The content of the lithium salt compound (B) is 3% by mass or more and 30% by mass or less with respect to the total amount of the non-aqueous electrolyte,
The content of the lithium salt compound (C), the total amount of the non-aqueous electrolyte, 10 mass% or less than 0.01 mass%, non-aqueous electrolyte according to claim 1. The lithium salt compound (B) comprises LiPF _6, non-aqueous electrolyte according to claim 1 or 2. The lithium salt compound (B), and LiPF _6, LiPO includes a ₂ F ₂ and / or LiBF _4, a non-aqueous electrolyte according to any one of claims 1-3. The lithium salt compound (C) is 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 and LiPF ₄ (C including ₂ O ₄₎ lithium salt least one compound selected from the group consisting of non-aqueous electrolyte according to any one of claims 1-4. The said cyclic phosphate ester compound (A) contains the cyclic phosphate ester compound whose R < ² > in the said General formula (1) is an ethylene group or a propylene group, The non-according to any one of Claims 1-5 Water electrolyte. A positive electrode, a negative electrode, and the nonaqueous electrolytic solution according to any one of claims 1 to 6 , wherein the potential of the positive electrode at the time of full charge is 4.4 V or more and 5.5 V or less based on lithium. There is a lithium ion secondary battery.