JP2015043298A - Non-aqueous electrolyte and lithium ion secondary battery using the non-aqueous electrolyte - Google Patents

Abstract

Disclosed is a non-aqueous electrolyte for a lithium ion battery that is excellent in cycle characteristics because generation of gas is suppressed by decomposition of the electrolyte even when applied to a lithium ion secondary battery having a high positive electrode potential. A non-aqueous electrolyte for a lithium ion battery is a phosphate ester containing a double bond represented by a specific compound such as dimethyl vinyl phosphate, diethyl vinyl phosphate, dipropyl vinyl phosphate, dibutyl vinyl phosphate, etc. It contains a compound (A), a lithium salt compound (B) having no oxalic acid structure, a lithium salt compound (C) having an oxalic acid structure, and a nonaqueous solvent containing a sulfite compound. [Selection figure] None

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.

  Although it is a lithium ion secondary battery that has become widespread, users of mobile electronic devices and electric vehicles still demand a higher energy density of the battery. 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 the lithium ion secondary battery, an 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. The 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 excellent lithium ion conductivity. Therefore, it came to be 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 deterioration of battery characteristics such as cycle characteristics.

  In order to solve the above problem, Patent Document 2 proposes a method of improving the oxidation resistance of an 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 Document 3 proposes a method for improving the cycle performance of a battery by including a specific phosphate ester in a non-electrolytic solution. Specifically, the cycle characteristics are improved by adding 2 to 25% by mass of a phosphate ester such as tripropyl phosphate or triallyl phosphate with respect to the non-aqueous electrolyte.

International Publication No. 2008/114739 International Publication No. 2012/132976 JP 2006-221972 A

  However, when the fluorinated non-aqueous solvent disclosed in Patent Document 2 is used, the solubility of the lithium electrolyte in the non-aqueous solvent is lowered and the ionic conductivity of the electrolytic solution is greatly lowered. There is a problem that the input / output characteristics of the device are impaired.

  Moreover, when the triallyl phosphate disclosed in Patent Document 3 is contained in a 5% by mass nonaqueous electrolytic solution, the effect of improving the cycle performance of the battery is not sufficient, and the effect of suppressing gas generation is not satisfactory. .

  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 is to provide an excellent 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 have determined that a specific phosphate ester compound (A) having a double bond and a lithium salt having no oxalic acid structure in a non-aqueous solvent It has been found that the above problems can be solved by using a non-aqueous electrolyte solution containing at least one compound (B) and one or more lithium salt compounds (C) having an oxalic acid structure, and the present invention has been completed.

That is, the present invention is as follows.
[1]
A double bond-containing phosphate ester compound (A) represented by the following general formula (1);
(In the formula, a represents an integer of 1 to 3, and b represents an integer of 0 to 10. R1 represents a hydroxy group, an optionally substituted alkoxy group having 1 to 15 carbon atoms, One of R 1, R 3, R 4, R 5 and R 6, which is selected from an optionally substituted alkyl group having 1 to 15 carbon atoms and an optionally substituted aryl group having 6 to 15 carbon atoms, Each is independently a hydrogen atom, a halogen atom or an optionally substituted organic 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 non-aqueous electrolyte solution.
[2]
The non-aqueous electrolyte according to [1], wherein the content of the component (A) is 0.01% by mass or more and 10% by mass or less with respect to the non-aqueous electrolyte.
[3]
The content of the component (B) is 3% by mass or more and 30% by mass or less with respect to the non-aqueous electrolyte, and the content of (C) is 0.01% by mass with respect to the non-aqueous electrolyte. The non-aqueous electrolyte according to [1] or [2], which is not less than 10% and not more than 10% by mass.
[4]
Component (B) comprises LiPF _6, non-aqueous electrolyte according to any one of [1] to [3].
[5]
The non-aqueous electrolyte according to any one of [1] to [4], wherein the component (B) includes LiPF ₆ and LiPO ₂ F ₂ and / or LiBF ₄ .
[6]
The component (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 O ₄ ) The nonaqueous electrolyte solution according to any one of [1] to [5], which contains one or more lithium salt compounds selected from the group consisting of lithium salt compounds.
[7]
Any of [1] to [6], wherein the component (A) includes a double bond-containing phosphate ester compound in which R2, R3, R4, R5, and R6 in the general formula (1) are all hydrogen atoms A non-aqueous electrolyte according to any one of the above.
[8]
The nonaqueous electrolytic solution according to any one of [1] to [7], wherein the nonaqueous solvent contains a sulfite ester compound.
[9]
A positive electrode;
A negative electrode,
[1] to the nonaqueous electrolyte solution according to any one of [8],
With
A lithium ion secondary battery in which the potential of the positive electrode when fully charged is 4.4 V or more and 5.5 V or less based on lithium.

  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.

  The non-aqueous electrolyte of the present embodiment includes a double bond-containing phosphate ester compound (A) represented by the following general formula (1), a lithium salt compound (B) having no oxalic acid structure, and oxalic acid A lithium salt compound (C) having a structure and a nonaqueous solvent are contained. Therefore, even when the nonaqueous electrolytic solution of this embodiment is applied to a lithium ion secondary battery having a higher positive electrode potential than the conventional one, gas generation, that is, decomposition of the electrolytic solution is suppressed, and excellent cycle characteristics are expressed. can do.

(Wherein, a represents an integer of 1 or more and 3 or less, b represents an integer of 0 or more and 10 or less. R1 is independently a hydroxy group or an optionally substituted carbon number of 1 or more and 15 or less. An alkoxy group having 1 to 15 carbon atoms which may be substituted, and an aryl group having 6 to 15 carbon atoms which may be substituted, and may be R2, R3, R4, R5 And R6 are each independently a hydrogen atom, a halogen atom, or an optionally substituted organic group having 1 to 10 carbon atoms.

  In the present embodiment, in the general formula (1), 3-a R1s are each independently a hydroxy group, an optionally substituted alkoxy group having 1 to 15 carbon atoms, and an optionally substituted carbon. This represents one kind selected from the group consisting of an alkyl group having 1 to 15 carbon atoms and an optionally substituted aryl group having 6 to 15 carbon atoms.

  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 heptoxy group, an octyloxy group, a nonyloxy group, and a decyloxy group. In these alkoxy groups, a hydrogen atom 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 alkoxy group is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, from the viewpoint of suppressing gas generation.

  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. In these alkyl groups, a hydrogen atom 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 preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, from the viewpoint of suppressing gas generation.

  Although it does not specifically limit as said aryl group, For example, a phenyl group, 1-naphthyl group, 2-naphthyl group etc. are mentioned. In these aryl groups, a hydrogen atom 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. 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 preferably 6 or more and 10 or less, more preferably 6 or more and 8 or less, from the viewpoint of suppressing gas generation.

  As R1, from the viewpoint of improving cycle characteristics, a hydroxy group, an optionally substituted alkoxy group having 1 to 10 carbon atoms, an optionally substituted alkyl group having 1 to 10 carbon atoms, and a substituted group. It is preferably one kind selected from aryl groups having 6 to 10 carbon atoms, more preferably a hydroxy group, an optionally substituted alkoxy group having 1 to 5 carbon atoms, and an optionally substituted carbon. It is a kind selected from an alkyl group having 1 to 5 carbon atoms and an aryl group having 6 to 8 carbon atoms which may be substituted.

  In this embodiment, R2, R3, R4, R5, and R6 in the general formula (1) each independently comprise a hydrogen atom, a halogen atom, and an optionally substituted organic group having 1 to 10 carbon atoms. Represents a kind selected from the group. Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Examples of the organic group include, but are not limited to, alkyl groups such as a methyl group; alkenyl groups such as a 2-propenyl group; alkynyl groups such as a 2-propynyl group; aryl groups such as a phenyl group; alkoxy such as a methoxy group Group; a cyano group and a carboxy group can be used. Specific examples of the organic group include, but are not limited to, methyl group, ethyl group, propyl group, butyl group, pentyl group, ethenyl group, 1-propenyl group, 2-propenyl group, 1-butenyl group, and 2-butenyl. Group, 3-butenyl group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group, methoxy group, ethoxy group, propoxy group, butoxy group, phenyl group, benzyl group, A cyano group or a carboxy group can be used. The number of carbon atoms in the organic group is preferably 1 or more and 8 or less, more preferably 1 or more and 5 or less, and still more preferably 1 or more and 3 or less, from the viewpoint of suppressing gas generation. R4 and R5 may be connected by an alkylene group, an alkelene group, or the like to form a ring structure. As R2, R3, R4, R5, and R6, from the viewpoint of more effectively suppressing gas generation, a hydrogen atom, a fluorine atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, Preferred is an alkenyl group having 1 to 10 carbon atoms, an alkynyl group having 1 to 10 carbon atoms which may be substituted, an aryl group having 6 to 10 carbon atoms which may be substituted, or a carboxy group. An atom, a fluorine atom, an optionally substituted alkyl group having 1 to 5 carbon atoms, an optionally substituted alkenyl group having 1 to 5 carbon atoms, and an optionally substituted carbon atom having 1 to 5 carbon atoms An alkynyl group, an optionally substituted aryl group having 6 to 8 carbon atoms, and a carboxy group are more preferable. From the same viewpoint, R2, R3, R4, R5, and R6 in the general formula (1) are all hydrogen atoms, that is, in the nonaqueous electrolytic solution of the present embodiment, R2, R3, More preferably, R4, R5, and R6 each include a double bond-containing phosphate ester compound that is a hydrogen atom.

  In the present embodiment, the double bond-containing phosphate ester compound (A) is preferably contained in an amount of 0.01% by mass or more based on the non-aqueous electrolyte from the viewpoint of more effectively suppressing gas generation. From the same viewpoint, it is more preferably 0.1% by mass or more, and further preferably 0.3% by mass or more. Further, from the viewpoint of input / output characteristics, the double bond phosphate ester compound (A) is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass with respect to the non-aqueous electrolyte. % Or less.

  Although it does not specifically limit as a double bond containing phosphate ester compound (A) represented by General formula (1) in this embodiment, For example, dimethyl vinyl phosphate, diethyl vinyl phosphate, dipropyl vinyl phosphate, Dibutyl vinyl phosphate, dipentyl vinyl phosphate, dihexyl vinyl phosphate, diheptyl vinyl phosphate, dioctyl vinyl phosphate, dinonyl vinyl phosphate, didecyl vinyl phosphate, dimethyl (2-propenyl) phosphate, diethyl (2 -Propenyl) phosphate, dipropyl (2-propenyl) phosphate, dibutyl (2-propenyl) phosphate, dipentyl (2-propenyl) phosphate, dihexyl (2-propenyl) Phosphate, diheptyl (2-propenyl) phosphate, dioctyl (2-propenyl) phosphate, dinonyl (2-propenyl) phosphate, didecyl (2-propenyl) phosphate, dimethyl (2-butenyl) phosphate, diethyl ( 2-butenyl) phosphate, dipropyl (2-butenyl) phosphate, dibutyl (2-butenyl) phosphate, dipentyl (2-butenyl) phosphate, dihexyl (2-butenyl) phosphate, diheptyl (2-butenyl) phosphate Fate, dioctyl (2-butenyl) phosphate, dinonyl (2-butenyl) phosphate, didecyl (2-butenyl) phosphate, dimethyl (3-butenyl) phosphate, diethyl (3-butenyl) phosphate Sulfate, dipropyl (3-butenyl) phosphate, dibutyl (3-butenyl) phosphate, dipentyl (3-butenyl) phosphate, dihexyl (3-butenyl) phosphate, diheptyl (3-butenyl) phosphate, dioctyl (3 -Butenyl) phosphate, dinonyl (3-butenyl) phosphate, didecyl (3-butenyl) phosphate, vinyl phosphate, divinyl phosphate, trivinyl phosphate, mono (2-propenyl) phosphate, bis (2- Propenyl) phosphate, tris (2-propenyl) phosphate, mono (2-butenyl) phosphate, bis (2-butenyl) phosphate, tris (2-butenyl) phosphate, mono (3-butenyl) phosphate Fate, bis (2-butenyl) phosphate, tris (2-butenyl) phosphate, benzyl dimethyl phosphate, benzyl diethyl phosphate, benzyl dipropyl phosphate, benzyl dipentyl phosphate, benzyl dihexyl phosphate, benzyl diheptyl phosphate Fate, benzyl dioctyl phosphate, benzyl dinonyl phosphate, benzyl didecyl phosphate, benzyl phosphate, dibenzyl phosphate, tribenzyl phosphate, divinyl methyl phosphonate, divinyl ethyl phosphonate, divinyl propyl phosphonate, divinyl butyl phosphonate, divinyl Pentyl phosphonate, divinyl hexyl phosphonate, divinyl heptyl phosphonate, di Nyloctylphosphonate, divinylnonylphosphonate, divinyldecylphosphonate, bis (2-propenyl) methylphosphonate, bis (2-propenyl) ethylphosphonate, bis (2-propenyl) propylphosphonate, bis (2-propenyl) butylphosphonate, bis ( 2-propenyl) pentylphosphonate, bis (2-propenyl) hexylphosphonate, bis (2-propenyl) heptylphosphonate, bis (2-propenyl) octylphosphonate, bis (2-propenyl) nonylphosphonate, bis (2-propenyl) decyl Phosphonate, bis (2-butenyl) methylphosphonate, bis (2-butenyl) ethylphosphonate, bis (2-butenyl) propylphosphonate, bis (2-butenyl) butylphosphine Bis (2-butenyl) pentylphosphonate, bis (2-butenyl) hexylphosphonate, bis (2-butenyl) heptylphosphonate, bis (2-butenyl) octylphosphonate, bis (2-butenyl) nonylphosphonate, bis (2 -Butenyl) decylphosphonate, bis (3-butenyl) methylphosphonate, bis (3-butenyl) ethylphosphonate, bis (3-butenyl) propylphosphonate, bis (3-butenyl) butylphosphonate, bis (3-butenyl) pentylphosphonate Bis (3-butenyl) hexylphosphonate, bis (3-butenyl) heptylphosphonate, bis (3-butenyl) octylphosphonate, bis (3-butenyl) nonylphosphonate, bis (3-butenyl) decylphosphonate, Dibenzyl methyl phosphonate, dibenzyl ethyl phosphonate, dibenzyl propyl phosphonate, dibenzyl butyl phosphonate, dibenzyl pentyl phosphonate, dibenzyl hexyl phosphonate, dibenzyl heptyl phosphonate, dibenzyl octyl phosphonate, dibenzyl nonyl phosphonate, dibenzyl decyl phosphonate Can be mentioned. As is apparent from the above exemplified compounds, the double bond-containing phosphate ester compound (A) has at least one carbon-carbon double bond in the molecule. That is, a in the general formula (1) is an integer of 1 or more and 3 or less, preferably 2 or 3, and more preferably 3. Further, b in the general formula (1) is an integer of 0 or more and 10 or less, preferably 0 or more and 5 or less, more preferably 1 or more and 5 or less.

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, the oxalic acid structure 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), considering 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 ) 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 ₂ F _{2 are used.} It is more preferable to use in combination. The concentration of the lithium salt compound (B) is 3% by mass or more, preferably 30% by mass or less, preferably 5% by mass or more with respect to the non-aqueous electrolyte in consideration of both input / output characteristics and cycle characteristics. Is more preferably 25% by mass or less, more preferably 8% by mass or more and even more preferably 20% by mass or less.

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 () in consideration of both solubility in a non-aqueous solvent and gas generation suppression. 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 and LiBF ₂ (C ₂ O ₄ ) are more preferable. The concentration of the lithium salt compound (C) is 0.01% by mass or more, preferably 10% by mass or less, preferably 0.1% by mass or more, and 5% by mass with respect to the non-aqueous electrolyte from the viewpoint of suppressing gas generation. More preferably, it is 0.3 mass% or less, and more preferably 3 mass% or less.

  The non-aqueous electrolyte of this embodiment uses a double bond-containing phosphate ester (A) and a lithium salt compound (C) 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 double bond-containing phosphate ester (A) and the lithium salt compound (C) are each non-aqueous. It is preferable to coexist in the non-aqueous electrolyte with a content of 0.01% by mass to 10% by mass with respect to the electrolyte. Since the gas generation suppressing 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 ion conduction. The reason why the gas generation is remarkably suppressed is not necessarily clear. That is, the effect exhibited by the non-aqueous electrolyte 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 double bond-containing phosphorus It is considered that the double bond site of the acid ester (A) acts cooperatively on the positive electrode and the negative electrode, thereby effectively suppressing gas generation.

  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. 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.

  From the viewpoint of improving cycle characteristics, in the nonaqueous electrolytic solution of the present embodiment, the nonaqueous solvent preferably contains a sulfite compound. The sulfite compound is not particularly limited, and examples thereof include ethylene sulfite, propylene sulfite, 1,3-propane sultone, 1,4-butane sultone, 1,5-pentane sultone, 1,6-hexane sultone, and the like. Can be used. Among these, from the viewpoint of improving cycle characteristics, 1,3-propane sultone, 1,4-butane sultone, and 1,5-pentane sultone are preferable, and 1,3-propane sultone and 1,4-pentane sultone are more preferable. Butane sultone. When 0.3% by mass or more of the sulfite compound is contained in the non-aqueous electrolyte, the cycle characteristics tend to be further improved, but preferably 0.5% by mass or more, more preferably 1% by mass or more. It is. When the content of the sulfite compound is 10% by mass or less with respect to the non-aqueous electrolyte, the input / output characteristics tend to be maintained. In consideration of such a tendency, the content is preferably 5% by mass or less. More preferably, it is 3 mass% or less.

The non-aqueous electrolyte solution of this embodiment, from the viewpoint of cycle characteristics improve, it will be preferable to include LiPO ₂ F _2, LiBF _4.

  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, and 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 5.5 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, 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 in the charged state ”.

  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 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 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 represent one or more selected from transition metals independently. 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 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 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 Mn and Al, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and x + y ≦ 1 is there. 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 [0.4 ≦ 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 a 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 pressed, and then the positive electrode material mixture layer is fixed on 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. d002 is more preferably 0.35 nm or less, and still more preferably 0.34 nm or less. 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. The average particle diameter of the carbon material is preferably 3 μm or more and 15 μm or less, more preferably 5 μm or more and 13 μm 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.

[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 In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, diethyl (2-propenyl) phosphate was 0.3% by mass, LiPF ₆ (12.1% by mass) and LiB (C ₂ O ₄ ) ₂ (1% by mass) 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 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 in a 25 ° C. environment at a constant current of 0.05 C until reaching a voltage of 4.35 V, 4.35 V The battery was charged at a constant voltage for 2 hours and discharged to 3.0 V 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 regarded as one cycle, and this was carried out for 100 cycles, and the capacity retention rate (%) was measured after 100 cycles. As a result, the capacity retention rate (%) after 100 cycles was as high as 91%. The capacity retention rate (%) after 100 cycles was obtained 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, the volume was measured by immersing in a water bath, and the amount of generated gas (mL) after continuous charge was determined from the volume change of the battery before and after continuous charge. As a result, the amount of generated gas (mL) after continuous charging was as small as 0.16 mL.

[Example 2]
A sheet battery was prepared in the same manner as in Example 1 except that dibutyl (2-propenyl) phosphate was used instead of diethyl (2-propenyl) phosphate in the preparation of the non-aqueous electrolyte 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 generated gas (mL) after continuous charging was as small as 0.17 mL.

[Example 3]
A sheet-like battery was prepared in the same manner as in Example 1 except that bis (2-propenyl) methylphosphonate was used instead of diethyl (2-propenyl) phosphate in the preparation of the non-aqueous electrolyte 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 generated gas (mL) after continuous charging was as small as 0.16 mL.

[Example 4]
A sheet battery was prepared in the same manner as in Example 1 except that bis (2-propenyl) hexylphosphonate was used instead of diethyl (2-propenyl) 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 generated gas (mL) after continuous charging was as small as 0.17 mL.

[Example 5]
A sheet battery was prepared in the same manner as in Example 1 except that tris (2-propenyl) phosphate was used instead of diethyl (2-propenyl) phosphate in the preparation of the non-aqueous electrolyte 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 91%, and the amount of generated gas (mL) after continuous charging was as low as 0.15 mL.

[Example 6]
A sheet battery was prepared in the same manner as in Example 1 except that dibenzyl phosphate was used instead of diethyl (2-propenyl) phosphate in the preparation of the nonaqueous electrolytic solution of Example 1, 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 89%, and the amount of generated gas (mL) after continuous charging was as low as 0.19 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 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 92%, and the amount of generated gas (mL) after continuous charging was as low as 0.14 mL.

[Example 8]
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 93%, and the amount of generated gas (mL) after continuous charging was as small as 0.13 mL.

[Example 9]
A sheet-like battery was prepared in the same manner as in Example 1 except that LiBF ₂ (C ₂ O ₄ ) was used instead of LiB (C ₂ O ₄ ) ₂ 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 91%, and the amount of generated gas (mL) after continuous charging was as low as 0.12 mL.

[Example 10]
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 91%, and the amount of generated gas (mL) after continuous charging was as small as 0.16 mL.

[Example 11]
In the preparation of the nonaqueous electrolytic solution of Example 1, a sheet-like battery was produced in the same manner as Example 1 except that 1% by mass was added instead of 0.3% by mass of diethyl (2-propenyl) 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 90%, and the amount of generated gas (mL) after continuous charging was as small as 0.14 mL.

[Example 12]
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 of diethyl (2-propenyl) phosphate was added instead of 0.3% by mass. 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 generated gas (mL) after continuous charging was as small as 0.11 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 0.3% by mass of diethyl (2-propenyl) phosphate was added instead of 5% by mass. 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 generated gas (mL) after continuous charging was as small as 0.11 mL.

[Example 14]
A sheet-like battery was produced in the same manner as in Example 1 except that 0.5% by mass was added instead of adding 1% by mass of LiB (C ₂ O ₄ ) ₂ in the preparation of the nonaqueous electrolytic solution 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 90%, and the amount of generated gas (mL) after continuous charging was as low as 0.15 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 prepared 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 generated gas (mL) 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 producing the test battery of Example 1, a sheet-like battery was prepared 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 generated gas (mL) 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, diethyl (2-propenyl) 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 prepared 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 generated gas (mL) after continuous charging was as large as 0.24 mL.

[Comparative Example 4]
To a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 1: 2, 5% by mass of triallyl phosphate and 12.1% by mass of LiPF ₆ were added. A non-aqueous electrolyte was used. In the production of the test battery of Example 1, a sheet-like battery was prepared 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 68%, and the amount of generated gas (mL) after continuous charging was as large as 0.37 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, 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 prepared 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 generated gas (mL) after continuous charging was as large as 0.32 mL.

[Comparative Example 6]
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 prepared 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 generated gas (mL) after continuous charging was as large as 0.28 mL.

  Table 1 shows the results obtained in Examples 1 to 14 and Comparative Examples 1 to 6. From Table 1, all the lithium ion secondary batteries of Examples 1 to 14 are Comparative Example 2 using a non-aqueous electrolyte containing no double bond-containing phosphate ester (A), a lithium salt having an oxalic acid structure. Compared with Comparative Example 3 using a non-aqueous electrolyte containing no compound (C) and Comparative Example 4 using a non-aqueous electrolyte containing 5% by mass of triallyl phosphate disclosed in Patent Document 3. It was revealed that the cycle characteristics were improved and the gas generation amount was greatly reduced. From the above, the above effect of the nonaqueous electrolytic solution of the present embodiment is obtained when the double bond-containing phosphate ester (A) and the lithium salt compound (C) having an oxalic acid structure coexist in the nonaqueous electrolytic solution. It was shown to be a peculiar effect.

[Example 15]
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 1,3-propane sultone was further added to the mixed solvent. And a gas generation test was conducted. As a result, the capacity retention rate (%) after 100 cycles was as high as 92%, and the amount of generated gas (mL) after continuous charging was as small as 0.16 mL.

[Example 16]
In the preparation of the nonaqueous electrolytic solution of Example 1, a sheet battery was prepared in the same manner as in Example 1 except that 1.5% by mass of 1,3-propane sultone was further added to the mixed solvent. And a gas generation test was conducted. As a result, the capacity retention rate (%) after 100 cycles was as high as 93%, and the amount of generated gas (mL) after continuous charging was as low as 0.15 mL.

[Example 17]
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 5% by mass of 1,3-propane sultone 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 generated gas (mL) after continuous charging was as small as 0.16 mL.

[Example 18]
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 1.5% by mass of 1,4-butane sultone was further added to the mixed solvent. A gas generation test was conducted. As a result, the capacity retention rate (%) after 100 cycles was as high as 93%, and the amount of generated gas (mL) after continuous charging was as low as 0.15 mL.

  The results obtained in Example 1 and Examples 15 to 18 are shown in Table 2. From Table 2, it was shown that when the sulfite compound was added to the nonaqueous electrolytic solution of this embodiment, the cycle characteristics were further improved.

[Example 19]
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 nonaqueous 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, diethyl (2-propenyl) 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., 4.8 V The battery was charged at a constant voltage for 2 hours and discharged to 3.0 V 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 regarded as one cycle, and this was carried out for 100 cycles, and the capacity retention rate (%) was measured after 100 cycles. As a result, the capacity retention rate (%) after 100 cycles was as high as 75%. The capacity retention rate (%) after 100 cycles was obtained 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. Then, the battery was charged until it reached a voltage of 4.8 V at a constant current of 1 C 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, the volume was measured by immersing in a water bath, and the amount of generated gas (mL) after continuous charge was determined from the volume change of the battery before and after continuous charge. As a result, the amount of generated gas (mL) after continuous charging was as small as 1.21 mL.

[Example 20]
A sheet-like battery was prepared in the same manner as in Example 19 except that dibutyl (2-propenyl) phosphate was used instead of diethyl (2-propenyl) phosphate in the preparation of the non-aqueous electrolyte of Example 19. The cycle test and the gas generation test were conducted. As a result, the capacity retention rate (%) after 100 cycles was as high as 72%, and the amount of generated gas (mL) after continuous charging was as low as 1.26 mL.

[Example 21]
A sheet-like battery was prepared in the same manner as in Example 19 except that bis (2-propenyl) methylphosphonate was used instead of diethyl (2-propenyl) phosphate in the preparation of the nonaqueous electrolytic solution of Example 19. 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 generated gas (mL) after continuous charging was as low as 1.14 mL.

[Example 22]
A sheet battery was prepared in the same manner as in Example 19 except that bis (2-propenyl) hexylphosphonate was used instead of diethyl (2-propenyl) phosphate in the preparation of the non-aqueous electrolyte of Example 19. The cycle test and the gas generation test were conducted. As a result, the capacity retention rate (%) after 100 cycles was as high as 72%, and the amount of generated gas (mL) after continuous charging was as small as 1.17 mL.

[Example 23]
A sheet-like battery was prepared in the same manner as in Example 19 except that tris (2-propenyl) phosphate was used instead of diethyl (2-propenyl) phosphate in the preparation of the non-aqueous electrolyte of Example 19. The cycle test and the gas generation test were conducted. As a result, the capacity retention rate (%) after 100 cycles was as high as 75%, and the amount of generated gas (mL) after continuous charging was as low as 1.18 mL.

[Example 24]
A sheet battery was prepared in the same manner as in Example 19 except that dibenzyl phosphate was used instead of diethyl (2-propenyl) phosphate in the preparation of the non-aqueous electrolyte of Example 19, 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 70%, and the amount of generated gas (mL) after continuous charging was as low as 1.27 mL.

[Example 25]
In the preparation of the nonaqueous electrolytic solution of Example 19, a sheet-like battery was produced in the same manner as in Example 19 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 76%, and the amount of generated gas (mL) after continuous charging was as low as 1.19 mL.

[Example 26]
A sheet-like battery was prepared in the same manner as in Example 19 except that LiBF ₂ (C ₂ O ₄ ) was used instead of LiB (C ₂ O ₄ ) ₂ in the preparation of the non-aqueous electrolyte of Example 19. 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 generated gas (mL) after continuous charging was as small as 1.13 mL.

[Example 27]
A sheet-like battery was produced in the same manner as in Example 19 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 19. The above cycle test and gas generation test were conducted. As a result, the capacity retention rate (%) after 100 cycles was as high as 75%, and the amount of generated gas (mL) after continuous charging was as low as 1.20 mL.

[Example 28]
In the preparation of the nonaqueous electrolytic solution of Example 19, a sheet-like battery was produced in the same manner as in Example 19 except that 1% by mass was added instead of 0.3% by mass of diethyl (2-propenyl) 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 71%, and the amount of generated gas (mL) after continuous charging was as low as 1.08 mL.

[Example 29]
In the preparation of the nonaqueous electrolytic solution of Example 19, a sheet-like battery was produced in the same manner as in Example 19 except that 3% by mass was added instead of 0.3% by mass of diethyl (2-propenyl) 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 77%, and the amount of generated gas (mL) after continuous charging was as low as 0.98 mL.

[Example 30]
In the preparation of the nonaqueous electrolytic solution of Example 19, a sheet-like battery was produced in the same manner as in Example 19 except that 5% by mass was added instead of 0.3% by mass of diethyl (2-propenyl) 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 generated gas (mL) after continuous charging was as low as 1.04 mL.

[Example 31]
A sheet-like battery was produced in the same manner as in Example 19 except that 0.5% by mass was added instead of adding 1% by mass of LiB (C ₂ O ₄ ) ₂ in the preparation of the nonaqueous electrolytic solution of Example 19. Then, a cycle test and a gas generation test were performed. As a result, the capacity retention rate (%) after 100 cycles was as high as 75%, and the amount of generated gas (mL) after continuous charging was as low as 1.16 mL.

[Comparative Example 7]
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 19, a sheet battery was prepared in the same manner as in Example 19 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 generated gas (mL) after continuous charging was as large as 4.32 mL.

[Comparative Example 8]
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 19, a sheet battery was prepared in the same manner as in Example 19 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 generated gas (mL) after continuous charging was as large as 2.62 mL.

[Comparative Example 9]
In a mixed solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, diethyl (2-propenyl) 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 19, a sheet battery was prepared in the same manner as in Example 19 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 58%, and the amount of generated gas (mL) after continuous charging was as large as 1.32 mL.

[Comparative Example 10]
To 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 added at 12.1% by mass and triallyl phosphate was added at 5% by mass. A non-aqueous electrolyte was used. In the production of the test battery of Example 19, a sheet battery was prepared in the same manner as in Example 19 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 2%, and the amount of generated gas (mL) after continuous charging was as large as 3.72 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 19, a sheet battery was prepared in the same manner as in Example 19 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 generated gas (mL) after continuous charging was as large as 2.61 mL.

  Table 3 shows the results obtained in Examples 19 to 31 and Comparative Examples 7 to 11 described above. From Table 3, all of the lithium ion secondary batteries of Examples 19 to 31 were Comparative Example 8 using a non-aqueous electrolyte solution not containing a double bond-containing phosphate ester (A), a lithium salt having an oxalic acid structure. Compared to Comparative Example 9 using a nonaqueous electrolytic solution containing no compound (C) and Comparative Example 10 using a nonaqueous electrolytic solution containing 5% by mass of triallyl phosphate disclosed in Patent Document 3. It was revealed that the cycle characteristics were improved and the gas generation amount was greatly reduced. From the above, the effect of this embodiment is a unique effect when the double bond-containing phosphate ester (A) and the lithium salt compound (C) having an oxalic acid structure coexist in the non-aqueous electrolyte. It was shown that.

  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 (9)

A double bond-containing phosphate ester compound (A) represented by the following general formula (1);
(In the formula, a represents an integer of 1 to 3, and b represents an integer of 0 to 10. R1 represents a hydroxy group, an optionally substituted alkoxy group having 1 to 15 carbon atoms, One of R 1, R 3, R 4, R 5 and R 6, which is selected from an optionally substituted alkyl group having 1 to 15 carbon atoms and an optionally substituted aryl group having 6 to 15 carbon atoms, Each is independently a hydrogen atom, a halogen atom or an optionally substituted organic 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 non-aqueous electrolyte solution.   The non-aqueous electrolyte according to claim 1, wherein the content of the component (A) is 0.01% by mass or more and 10% by mass or less with respect to the non-aqueous electrolyte.   The content of the component (B) is 3% by mass or more and 30% by mass or less with respect to the non-aqueous electrolyte, and the content of the (C) is 0.01% by mass with respect to the non-aqueous electrolyte. The nonaqueous electrolytic solution according to claim 1, wherein the nonaqueous electrolytic solution is not less than 10% and not more than 10% by mass. The (B) component comprises LiPF _6, non-aqueous electrolyte according to any one of claims 1 to 3. The component (B), and LiPF _6, LiPO includes a ₂ F ₂ and / or LiBF _4, a non-aqueous electrolyte according to any one of claims 1-4. The component (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 O The nonaqueous electrolytic solution according to any one of claims 1 to 5, comprising one or more lithium salt compounds selected from ₄ ).   The component (A) includes a double bond-containing phosphate ester compound in which R2, R3, R4, R5, and R6 in the general formula (1) are all hydrogen atoms. The nonaqueous electrolytic solution according to Item.   The nonaqueous electrolytic solution according to any one of claims 1 to 7, wherein the nonaqueous solvent contains a sulfite ester compound. A positive electrode;
A negative electrode,
The nonaqueous electrolytic solution according to any one of claims 1 to 8,
With
A lithium ion secondary battery in which the potential of the positive electrode at full charge is 4.4 V or more and 5.5 V or less based on lithium.