JP2007165301A - Lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery with a high capacity, excellent life, and a high output, and with fall of a battery capacity and output restrained even with repeated charge and discharge of the battery, even in a larger format. <P>SOLUTION: The lithium secondary battery utilizes a cathode using two or more kinds of cathode active materials with different compositions, and nonaqueous electrolyte solution containing a cyclosiloxane compound expressed by formula (1), a fluorosilane compound expressed by formula (2), a compound expressed by formula (3), a compound having an S-F bond in the molecule, nitrate, nitrite, monofluoro phosphate, difluoro phosphate, and acetate or propionate by 10 ppm or more in the whole electrolyte solution. In formula (1), R<SP>1</SP>and R<SP>2</SP>denote an organic group with the carbon number of 1 to 12, and n is an integer of 3 to 10. In formula (2), R<SP>3</SP>to R<SP>5</SP>denote an organic group with the carbon number of 1 to 12, x is an integer of 1 to 3, and p, q, and r are an integer of 0 to 3, respectively, satisfying: 1≤p+q+r≤3. In formula (3), R<SP>6</SP>to R<SP>8</SP>denote an organic group with the carbon number of 1 to 12, and A is a group constituted of H, C, N, O, F, S, Si and/or P. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lithium secondary battery, and more specifically, by using a non-aqueous electrolyte solution for a lithium secondary battery containing a specific component and two or more types of positive electrode active materials having different compositions. The present invention relates to a long-life, high-power lithium secondary battery.

  Lithium secondary batteries are high-capacity secondary batteries and are used in various applications. However, they are mainly used for relatively small batteries such as mobile phones. The use of is expected to expand. Large batteries require particularly high output and long life, and simply increasing the size of a conventional small battery is not sufficient as performance.

  Thus, various improvements of battery materials for improving output and life have been proposed (for example, Patent Document 1). In particular, various studies have been made on positive electrode active materials, which are factors that greatly affect the performance of lithium secondary batteries, and various active materials containing lithium and transition metals are known.

  However, these positive electrode active materials have advantages and disadvantages, respectively, and none of them has a large capacity, good life, high output, and low cost. Therefore, it has been studied to balance performance by mixing positive electrode active materials having different compositions, and it is also known that a synergistic effect can be obtained depending on the combination (for example, Patent Document 2).

However, sufficient performance has not been obtained yet, and further improvement has been demanded.
JP 2005-71749 A JP 2001-15108 A

  The present invention has been made in view of the background art, and the problem is that even when the size is increased, the battery has a large capacity, a good life, and a high output. An object of the present invention is to provide a lithium secondary battery in which a decrease in capacity and output is suppressed.

  As a result of intensive studies to solve the above problems, the inventors use a positive electrode containing two or more types of positive electrode active materials having different compositions and a non-aqueous electrolyte solution containing a compound selected from a specific group. Thus, it was found that a lithium secondary battery having a good life and a high output could be obtained, and the present invention was completed.

［一般式（１）中、Ｒ^１及びＲ^２は互いに同一であっても異なっていてもよい炭素数１〜１２の有機基を表し、ｎは３〜１０の整数を表す。］

［一般式（２）中、Ｒ^３〜Ｒ^５は互いに同一であっても異なっていてもよい炭素数１〜１２の有機基を表し、ｘは１〜３の整数を表し、ｐ、ｑ及びｒはそれぞれ０〜３の整数を表し、１≦ｐ＋ｑ＋ｒ≦３である。］

［一般式（３）中、Ｒ^６〜Ｒ^８は互いに同一であっても異なっていてもよい炭素数１〜１２の有機基を表し、ＡはＨ、Ｃ、Ｎ、Ｏ、Ｆ、Ｓ、Ｓｉ及び／又はＰから構成される基を表す。］ That is, the present invention is a lithium secondary battery comprising at least a positive electrode and a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte solution containing a lithium salt in a non-aqueous solvent, the non-aqueous electrolysis The liquid is a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), a compound having an SF bond in the molecule. A non-aqueous electrolyte containing 10 ppm or more of at least one compound selected from the group consisting of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate The present invention provides a lithium secondary battery, which is an aqueous electrolyte solution, wherein the positive electrode is a positive electrode containing two or more types of positive electrode active materials having different compositions.

[In General Formula (1), R ¹ and R ² represent the same or different organic group having 1 to 12 carbon atoms, and n represents an integer of 3 to 10. ]

[In General Formula (2), R ^{3 to} R ⁵ represent an organic group having 1 to 12 carbon atoms which may be the same or different from each other, x represents an integer of 1 to 3, p, q and Each r represents an integer of 0 to 3, and 1 ≦ p + q + r ≦ 3. ]

[In General Formula (3), R ^{6 to} R ⁸ represent an organic group having 1 to 12 carbon atoms which may be the same as or different from each other, and A represents H, C, N, O, F, S, Represents a group composed of Si and / or P; ]

  According to the present invention, a lithium secondary battery having a high capacity, a long life, a high output, and a reduction in battery capacity and output even when the battery is repeatedly charged and discharged (excellent in repeated charge / discharge characteristics (cycle characteristics)). Therefore, for example, a lithium secondary battery that is particularly suitable as a large battery for use in automobiles can be provided.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to the gist of the present invention. The specific content of is not limited.

<Non-aqueous electrolyte for lithium secondary battery>
The non-aqueous electrolyte solution for secondary batteries of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, in the same manner as a normal non-aqueous electrolyte solution. The electrolyte is not particularly limited as long as it is known to be a lithium salt that can be used as an electrolyte for a non-aqueous electrolyte solution for a lithium secondary battery, and examples thereof include the following.

[Lithium salt]
Inorganic lithium salts: inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ ; perhalogenates such as LiClO ₄ , LiBrO ₄ , LiIO ₄ ; inorganic chloride salts such as LiAlCl ₄ .
Fluorine-containing organic lithium salt: perfluoroalkane sulfonate such as LiCF ₃ SO ₃ ; LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ Perfluoroalkanesulfonylimide salts such as SO ₂ ); Perfluoroalkanesulfonylmethide salts such as LiC (CF ₃ SO ₂ ) ₃ ; Li [PF ₅ (CF ₂ CF ₂ CF ₃ )], Li [PF ₄ ( CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ] and other fluoroalkyl fluorophosphates.
Oxalatoborate salt: lithium bis (oxalato) borate, lithium difluorooxalatoborate and the like.

These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. Among these, LiPF ₆ is preferable when comprehensively judging solubility in a non-aqueous solvent, charge / discharge characteristics in the case of a secondary battery, output characteristics, cycle characteristics, and the like.

A preferable example in the case of using two or more types together is a combination use of LiPF ₆ and LiBF _{4. In} this case, the ratio of LiBF _{4 in} the total of both is 0.01% by mass or more and 20% by mass or less. It is preferable that it is 0.1 mass% or more and 5 mass% or less especially. Another example is the combined use of an inorganic fluoride salt and a perfluoroalkanesulfonylimide salt. In this case, the proportion of the inorganic fluoride salt in the total of both is 70% by mass or more and 99% by mass. Or less, more preferably 80% by mass or more and 98% by mass or less. The combined use of both has the effect of suppressing deterioration due to high temperature storage.

  The concentration of the lithium salt in the nonaqueous electrolytic solution is not particularly limited, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.7 mol / L or more. Moreover, the upper limit is 2 mol / L or less normally, Preferably it is 1.8 mol / L or less, More preferably, it is 1.7 mol / L or less. If the concentration is too low, the electrical conductivity of the non-aqueous electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity. May decrease.

[Nonaqueous solvent]
As the non-aqueous solvent, it can be appropriately selected from those conventionally proposed as solvents for non-aqueous electrolyte solutions. For example, the following are mentioned.
1) Cyclic carbonate:
As for carbon number of the alkylene group which comprises a cyclic carbonate, 2-6 are preferable, Most preferably, it is 2-4. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of these, ethylene carbonate and propylene carbonate are preferable.
2) Chain carbonate:
As the chain carbonate, dialkyl carbonate is preferable, and the number of carbon atoms of the alkyl group is preferably 1 to 5, and particularly preferably 1 to 4, respectively. Specific examples include dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. Of these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable.
3) Cyclic ester:
Specific examples include γ-butyrolactone and γ-valerolactone.
4) Chain ester:
Specific examples include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.
5) Cyclic ether:
Specific examples include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and the like.
6) Chain ether:
Specific examples include dimethoxyethane and dimethoxymethane.
7) Sulfur-containing organic solvent:
Specific examples include sulfolane and diethylsulfone.

  These may be used alone or in combination of two or more, but it is preferable to use in combination of two or more. For example, it is preferable to use a high dielectric constant solvent such as cyclic carbonates and cyclic esters in combination with a low viscosity solvent such as chain carbonates and chain esters.

  One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of the cyclic carbonates and the chain carbonates in the nonaqueous solvent is 85% by volume or more, preferably 90% by volume or more, and more preferably 95% by volume or more. Further, the capacity of the cyclic carbonate with respect to the total of the cyclic carbonate and the chain carbonate is 5% or more, preferably 10% or more, more preferably 15% or more, usually 50% or less, preferably 35% or less, More preferably, it is 30% or less. It is particularly preferred that the above preferred volume range of the total amount of carbonates occupying the entire non-aqueous solvent is combined with the preferred above volume range of cyclic carbonates relative to cyclic and chain carbonates.

  In this mixed solvent, a lithium salt and a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), and S in the molecule A non-aqueous electrolyte solution containing at least one compound selected from the group consisting of a compound having a -F bond, nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate is This is preferable because the balance between cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) and suppression of gas generation of a battery manufactured using this is improved.

  Specific examples of preferred combinations of cyclic carbonates and chain carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination. When propylene carbonate is contained, the volume ratio of ethylene carbonate to propylene carbonate is usually 99: 1 to 40:60, preferably 95: 5 to 50:50.

  Among these, those containing asymmetric chain carbonates are more preferable, particularly ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl. Those containing ethylene carbonate such as methyl carbonate, symmetric chain carbonates, and asymmetric chain carbonates are preferred because of a good balance between cycle characteristics and large current discharge characteristics. Among them, the asymmetric chain carbonate is preferably ethyl methyl carbonate, and the alkyl group constituting the dialkyl carbonate preferably has 1 to 2 carbon atoms.

  Other examples of preferred non-aqueous solvents are those containing chain esters. As the chain ester, methyl acetate, ethyl acetate and the like are particularly preferable. The capacity of the chain ester in the non-aqueous solvent is usually 5% or more, preferably 8% or more, more preferably 15% or more, usually 50% or less, preferably 35% or less, more preferably 30% or less, More preferably, it is 25% or less. In particular, those containing a chain ester in the mixed solvent of cyclic carbonates and chain carbonates are preferable from the viewpoint of improving the low-temperature characteristics of the battery.

  Examples of other preferable non-aqueous solvents include one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, γ-butyrolactone and γ-valerolactone, or two or more organic solvents selected from the group. The mixed solvent becomes 60% by volume or more of the whole. Such a mixed solvent preferably has a flash point of 50 ° C. or higher, and particularly preferably has a flash point of 70 ° C. or higher. A non-aqueous electrolyte using this solvent reduces evaporation of the solvent and leakage even when used at high temperatures. Among them, the amount of γ-butyrolactone in the nonaqueous solvent is 60% by volume or more, and the total of ethylene carbonate and γ-butyrolactone in the nonaqueous solvent is 80% by volume or more, preferably 90% by volume or more. And the volume ratio of ethylene carbonate to γ-butyrolactone is 5:95 to 45:55, or the total of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 80% by volume or more, preferably 90% When the ratio of ethylene carbonate to propylene carbonate is 30:70 to 60:40, the balance between cycle characteristics and large current discharge characteristics is generally improved.

[Specific compounds]
The non-aqueous electrolyte of the present invention includes a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), and S in the molecule. A compound having —F bond, at least one compound selected from the group consisting of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate (these are referred to as “specific compound”) (It may be abbreviated to be included) or added.

[[Cyclic Siloxane Compound Represented by General Formula (1)]]
R ¹ and although R ² are identical there may be different even if an organic group having 1 to 12 carbon atoms with each other, as R ¹ and R ² in the general formula (1) cyclic siloxane compound represented by, Chain alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group and t-butyl group; cyclic alkyl groups such as cyclohexyl group and norbornyl group; vinyl group, Alkenyl groups such as 1-propenyl group, allyl group, butenyl group, 1,3-butadienyl group; alkynyl groups such as ethynyl group, propynyl group, butynyl group; halogenated alkyl groups such as trifluoromethyl group; 3-pyrrolidino An alkyl group having a saturated heterocyclic group such as a propyl group; an aryl group such as a phenyl group optionally having an alkyl substituent; a phenylmethyl group; Examples thereof include aralkyl groups such as nylethyl group; trialkylsilyl groups such as trimethylsilyl group; trialkylsiloxy groups such as trimethylsiloxy group.

Among them, those having a smaller number of carbon atoms are more likely to exhibit characteristics, and organic groups having 1 to 6 carbon atoms are preferable. Alkenyl groups act on non-aqueous electrolytes and coatings on electrode surfaces to improve input / output characteristics, and aryl groups have the effect of capturing radicals generated in the battery during charge and discharge to improve overall battery performance. Therefore, it is preferable. Accordingly, R ¹ and R ² are particularly preferably a methyl group, a vinyl group, or a phenyl group.

  In general formula (1), n represents an integer of 3 to 10, but an integer of 3 to 6 is preferable, and 3 or 4 is particularly preferable.

  Examples of the cyclic siloxane compound represented by the general formula (1) include, for example, hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane, hexaphenylcyclotrisiloxane, 1,3,5-trimethyl-1,3,5. -Cyclotrisiloxane such as trivinylcyclotrisiloxane, cyclotetrasiloxane such as octamethylcyclotetrasiloxane, cyclopentasiloxane such as decamethylcyclopentasiloxane, and the like. Of these, cyclotrisiloxane is particularly preferred.

[[Fluorosilane compound represented by general formula (2)]]
R ^{3 to} R ⁵ in the fluorosilane compound represented by the general formula (2) are organic groups having 1 to 12 carbon atoms which may be the same as or different from each other, but R in the general formula (1) Examples of the chain alkyl group, cyclic alkyl group, alkenyl group, alkynyl group, halogenated alkyl group, alkyl group having a saturated heterocyclic group, phenyl group optionally having an alkyl group, etc. mentioned as examples of ¹ and R ² In addition to aryl groups, aralkyl groups, trialkylsilyl groups, trialkylsiloxy groups, carbonyl groups such as ethoxycarbonylethyl groups; carboxyl groups such as acetoxy groups, acetoxymethyl groups, trifluoroacetoxy groups; methoxy groups, ethoxy groups, Oxy group such as propoxy group, butoxy group, phenoxy group, allyloxy group; amino group such as allylamino group; Mention may be made of the group, and the like.

  In general formula (2), x represents an integer of 1 to 3, p, q, and r each represents an integer of 0 to 3, and 1 ≦ p + q + r ≦ 3. Inevitably, x + p + q + r = 4.

  Examples of the fluorosilane compound represented by the general formula (2) include trimethylfluorosilane, triethylfluorosilane, tripropylfluorosilane, phenyldimethylfluorosilane, triphenylfluorosilane, vinyldimethylfluorosilane, vinyldiethylfluorosilane, In addition to monofluorosilanes such as vinyldiphenylfluorosilane, trimethoxyfluorosilane, and triethoxyfluorosilane, difluorosilanes such as dimethyldifluorosilane, diethyldifluorosilane, divinyldifluorosilane, and ethylvinyldifluorosilane; methyltrifluorosilane, Also included are trifluorosilanes such as ethyltrifluorosilane.

  If the boiling point of the fluorosilane compound represented by the general formula (2) is low, it will volatilize, and therefore it may be difficult to contain a predetermined amount in the non-aqueous electrolyte. Moreover, even if it is made to contain in a non-aqueous electrolyte solution, there exists a possibility that it may volatilize on the conditions that the heat_generation | fever of a battery by charging / discharging or external environment becomes high temperature. Accordingly, those having a boiling point of 50 ° C. or higher at 1 atm are preferable, and those having a boiling point of 60 ° C. or higher are particularly preferable.

  Further, like the compound of the general formula (1), the organic group having a smaller number of carbon atoms is more effective, and the alkenyl group having 1 to 6 carbon atoms acts on the non-aqueous electrolyte solution or the electrode surface coating. Thus, the input / output characteristics are improved, and the aryl group has the effect of capturing radicals generated in the battery during charge / discharge and improving the overall battery performance. Therefore, from this viewpoint, the organic group is preferably a methyl group, a vinyl group, or a phenyl group, and examples of the compound include trimethylfluorosilane, vinyldimethylfluorosilane, phenyldimethylfluorosilane, and vinyldiphenylfluorosilane. .

[[Compound represented by formula (3)]]
R ^{6 to} R ⁸ in the compound represented by the general formula (3) are organic groups having 1 to 12 carbon atoms which may be the same as or different from each other. A chain alkyl group, a cyclic alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, an alkyl group having a saturated heterocyclic group, or an alkyl group, which are mentioned as examples of R ^{3 to} R ⁵ Aryl groups such as phenyl groups, aralkyl groups, trialkylsilyl groups, trialkylsiloxy groups, carbonyl groups, carboxyl groups, oxy groups, amino groups, benzyl groups, and the like can be similarly exemplified.

  A in the compound represented by the general formula (3) is not particularly limited as long as A is a group composed of H, C, N, O, F, S, Si and / or P, but the general formula (3) C, S, Si or P is preferable as the element directly bonded to the oxygen atom therein. Examples of the existence form of these atoms include a chain alkyl group, a cyclic alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, a carbonyl group, a sulfonyl group, a trialkylsilyl group, a phosphoryl group, and a phosphinyl group. Those are preferred. The molecular weight of the compound represented by the general formula (3) is preferably 1000 or less, particularly preferably 800 or less, and more preferably 500 or less.

  Examples of the compound represented by the general formula (3) include siloxane compounds such as hexamethyldisiloxane, 1,3-diethyltetramethyldisiloxane, hexaethyldisiloxane, and octamethyltrisiloxane; methoxytrimethylsilane, ethoxy Alkoxysilanes such as trimethylsilane; peroxides such as bis (trimethylsilyl) peroxide; carboxylic acid esters such as trimethylsilyl acetate, triethylsilyl acetate, trimethylsilyl propionate, trimethylsilyl methacrylate, trimethylsilyl trifluoroacetate; methanesulfonic acid Sulfonic acid esters such as trimethylsilyl, trimethylsilyl ethanesulfonate, triethylsilyl methanesulfonate, trimethylsilyl fluoromethanesulfonate; bis (trimethylsilyl) Sulfuric esters such as sulfates; tris (trimethylsiloxy) borate esters such as boron; tris (trimethylsilyl) phosphate, tris (trimethylsilyl) phosphite phosphoric acid or phosphorous acid esters such as phosphite and the like.

  Of these, siloxane compounds, sulfonic acid esters, and sulfuric acid esters are preferable, and sulfonic acid esters are particularly preferable. The siloxane compound is preferably hexamethyldisiloxane, the sulfonic acid ester is preferably trimethylsilyl methanesulfonate, and the sulfuric acid ester is preferably bis (trimethylsilyl) sulfate.

[[Compound with SF bond in molecule]]
The compound having an S—F bond in the molecule is not particularly limited, but sulfonyl fluorides and fluorosulfonic acid esters are preferred. For example, methanesulfonyl fluoride, ethanesulfonyl fluoride, methanebis (sulfonyl fluoride), ethane-1,2-bis (sulfonyl fluoride), propane-1,3-bis (sulfonyl fluoride), butane-1,4 -Bis (sulfonyl fluoride), difluoromethane bis (sulfonyl fluoride), 1,1,2,2-tetrafluoroethane-1,2-bis (sulfonyl fluoride), 1,1,2,2,3 Examples include 3-hexafluoropropane-1,3-bis (sulfonyl fluoride), methyl fluorosulfonate, ethyl fluorosulfonate, and the like. Of these, methanesulfonyl fluoride, methanebis (sulfonyl fluoride) or methyl fluorosulfonate is preferable.

[[Nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, propionate]]
The counter cation of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, propionate is not particularly limited, but metal elements such as Li, Na, K, Mg, Ca, Fe, Cu, etc. In addition, ammonium or quaternary ammonium represented by NR ⁹ R ¹⁰ R ¹¹ R ¹² (wherein R ^{9 to} R ¹² each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms). Is mentioned. Here, the organic group having 1 to 12 carbon atoms of R ^{9 to} R ¹² is an alkyl group which may be substituted with a halogen atom, a cycloalkyl group which may be substituted with a halogen atom, or a halogen atom. An aryl group which may be present, a nitrogen atom-containing heterocyclic group, and the like. R ^{9 to} R ¹² are each preferably a hydrogen atom, an alkyl group, a cycloalkyl group, a nitrogen atom-containing heterocyclic group, or the like. Among these counter cations, lithium, sodium, potassium, magnesium, calcium or NR ⁹ R ¹⁰ R ¹¹ R ¹² is preferable, and lithium is particularly preferable from the viewpoint of battery characteristics when used in a lithium secondary battery. Of these, nitrates or difluorophosphates are preferred from the standpoint of improving output characteristics and cycle characteristics, and lithium difluorophosphate is particularly preferred. In addition, those compounds synthesized in a non-aqueous solvent may be used substantially as they are, or those synthesized separately and substantially isolated may be added to the non-aqueous solvent.

  A specific compound, that is, a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), and an SF bond in the molecule. Compound, nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate or propionate may be used alone, or two or more compounds may be used in any combination and ratio May be. Moreover, even if it is a compound classified into said each with a specific compound, 1 type may be used independently and 2 or more types of compounds may be used together by arbitrary combinations and ratios.

  The ratio of these specific compounds in the non-aqueous electrolyte solution is essential to be 10 ppm or more (0.001 mass% or more) in total with respect to the total non-aqueous electrolyte solution, but is preferably 0.01 mass% or more. Preferably it is 0.05 mass% or more, More preferably, it is 0.1 mass% or more. The upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. If the concentration of the specific compound is too low, the effect of improving battery output or the effect of improving battery life may be difficult to obtain, while if the concentration is too high, the charge / discharge efficiency may be reduced.

  In addition, when these specific compounds are actually used in the production of secondary batteries as non-aqueous electrolytes, the content of the specific compounds is significantly reduced even if the battery is disassembled and the non-aqueous electrolyte is taken out again. There are many. Therefore, what can detect the said specific compound at least from the non-aqueous electrolyte solution extracted from the battery is considered to be included in this invention.

  The non-aqueous electrolyte solution according to the present invention can be prepared by dissolving an electrolyte lithium salt, a specific compound, and, if necessary, other compounds in a non-aqueous solvent. In preparing the non-aqueous electrolyte, each raw material is preferably dehydrated in advance, and the water content is usually 50 ppm or less, preferably 30 ppm or less, particularly preferably 10 ppm or less.

[Other compounds]
The non-aqueous electrolyte solution in the present invention contains a lithium salt that is an electrolyte and a specific compound as essential components in a non-aqueous solvent, but other compounds are optionally added within the range that does not impair the effects of the present invention. Can be contained in an amount of. Specific examples of such other compounds include:
(1) Aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, o-cyclohexylfluoro Partially fluorinated products of the above-mentioned aromatic compounds such as benzene and p-cyclohexylfluorobenzene; fluorinated anisole such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole Overcharge inhibitors such as compounds;
(2) vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, trifluoropropylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, etc. Negative electrode film-forming agent;
(3) Ethylene sulfite, propylene sulfite, dimethyl sulfite, propane sultone, butane sultone, methyl methanesulfonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetra Positive electrode protecting agents such as methylene sulfoxide, diphenyl sulfide, thioanisole, diphenyl disulfide, dipyridinium disulfide;
Etc.

  As the overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. Two or more of these may be used in combination. When using 2 or more types together, it is particularly preferable to use cyclohexylbenzene or terphenyl (or a partially hydrogenated product thereof) together with t-butylbenzene or t-amylbenzene.

  As the negative electrode film forming agent, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, and maleic anhydride are preferable. Two or more of these may be used in combination. When using 2 or more types together, vinylene carbonate and vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride, or maleic anhydride are preferable. As the positive electrode protective agent, ethylene sulfite, propylene sulfite, propane sultone, butane sultone, methyl methanesulfonate, and busulfan are preferable. Two or more of these may be used in combination. Moreover, the combined use of a negative electrode film forming agent and a positive electrode protective agent, or the combined use of an overcharge inhibitor, a negative electrode film forming agent, and a positive electrode protective agent is particularly preferable.

  The content ratio of these other compounds in the non-aqueous electrolyte solution is not particularly limited, but is preferably 0.01% by mass or more, particularly preferably 0.1% by mass or more, respectively, based on the whole non-aqueous electrolyte solution. The upper limit is preferably 5% by mass or less, particularly preferably 3% by mass or less, and further preferably 2% by mass or less. By adding these compounds, it is possible to suppress rupture / ignition of the battery at the time of abnormality due to overcharge, and to improve the capacity maintenance characteristic and cycle characteristic after high-temperature storage.

  There is no particular limitation on the method for preparing the non-aqueous electrolyte solution for the secondary battery of the present invention, and it is prepared by dissolving a lithium salt, a specific compound, and, if necessary, other compounds in a non-aqueous solvent according to a conventional method. Can do.

<Positive electrode>
The positive electrode used for the lithium secondary battery of the present invention will be described below.
[[Positive electrode active material]]
The positive electrode active material used for the positive electrode is described below.
[[[composition]]]
The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. A substance containing lithium and at least one transition metal is preferable, and examples thereof include a lithium transition metal composite oxide and a lithium-containing transition metal phosphate compound.

The transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples include lithium / cobalt composite oxide such as LiCoO ₂ or LiNiO ₂ . Lithium / nickel composite oxide, LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _{3 and} other lithium / manganese composite oxides, Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and those substituted with other metals such as Si.

The lithium-cobalt composite oxide is not particularly limited, but preferably has a composition represented by the following composition formula (4).
Li _x Co _(1-y) M ¹ _y O ₂ composition formula (4)
[In composition formula (4), M ¹ represents at least one element selected from the group consisting of Ni, Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb, and x is 0 < x represents a number that satisfies 1.2, and y represents a number that satisfies 0.05 ≦ y ≦ 0.8. ]

In the composition formula (4), M ¹ is particularly preferably Ni, Mn, Al, or Fe, x is particularly preferably 0.2 ≦ x ≦ 1.15, and y is 0.1 ≦ 0.1. It is particularly preferable that y ≦ 0.5.

The lithium / nickel composite oxide is not particularly limited, but preferably has a composition represented by the following composition formula (5).
Li _x Ni _(1-y) M ² _y O ₂ composition formula (5)
[In composition formula (5), M ² represents at least one element selected from the group consisting of Co, Mn, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb, and x is 0 < x represents a number that satisfies 1.2, and y represents a number that satisfies 0.05 ≦ y ≦ 0.8. ]

In the composition formula (5), M ² is particularly preferably Co, Mn, Al, and Fe, x is particularly preferably 0.2 ≦ x ≦ 1.15, and y is 0.1 ≦ 0.1. It is particularly preferable that y ≦ 0.5.

The lithium-manganese composite oxide is not particularly limited, but preferably has a composition represented by the following composition formula (6).
Li _x Mn _(1-y) M ³ _y O ₂ composition formula (6)
[In composition formula (6), M ³ represents at least one element selected from the group consisting of Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb, and x is 0 < x represents a number that satisfies 1.2, and y represents a number that satisfies 0.05 ≦ y ≦ 0.8. ]

In the composition formula (6), M ³ is particularly preferably Ni, Co, or Fe, x is particularly preferably 0.2 ≦ x ≦ 1.15, and y is 0.1 ≦ y ≦. Particularly preferred is 0.7.

As said lithium manganese composite oxide, what has a composition represented by the following compositional formula (7) is also preferable.
Li _x Mn _(2-y) M ⁴ _y O ₄ composition formula (7)
[In the composition formula (7), M ⁴ represents at least one element selected from the group consisting of Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb, and x is 0 < x represents a number that satisfies 1.2, and y represents a number that satisfies 0.05 ≦ y ≦ 0.8. ]

In the composition formula (7), M ⁴ is particularly preferably Ni, Co, Al, Mg, x is particularly preferably 0.05 ≦ x ≦ 1.15, and y is 0.1 ≦ 0.1. It is particularly preferable that y ≦ 0.7.

As said lithium manganese composite oxide, what has a composition represented by the following compositional formula (8) is also preferable.
Li _x Mn _(1-y) M ⁵ _y O ₃ composition formula (8)
[In formula (8), ^{M 5} represents Ni, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, at least one element selected from the group consisting of Zn and Nb, x is 0 < x represents a number that satisfies 2.4, and y represents a number that satisfies 0.05 ≦ y ≦ 0.8. ]

In the composition formula (8), M ⁵ is particularly preferably Ni, Co, Al, Mg, x is particularly preferably 0.1 ≦ x ≦ 2.3, and y is 0.1 ≦ 0.1. It is particularly preferable that y ≦ 0.5.

As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ). ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

The iron phosphates are not particularly limited, but those having a composition represented by the following composition formula (9) are preferable.
Li _x Fe _(1-y) M ⁶ _y PO ₄ composition formula (9)
[In the composition formula (9), M ⁶ represents at least one element selected from the group consisting of Ni, Co, Mn, Al, Ti, Mg, Cr, Ga, Cu, Zn, and Nb, and x is 0 < x represents a number that satisfies 1.2, and y represents a number that satisfies 0.05 ≦ y ≦ 0.8. ]

In the composition formula (9), M ⁶ is particularly preferably Ni, Co, Mn, and Al, x is particularly preferably 0.2 ≦ x ≦ 1.15, and y is 0.1 ≦ 0.1. It is particularly preferable that y ≦ 0.5.

  The positive electrode active material in the present invention is preferably used in combination of two or more of the above-described positive electrode active materials in any combination and ratio. Since each positive electrode active material has different performance, it is preferable to combine necessary performances according to the intended use of the battery. In general, the performance is considered to be an arithmetic average depending on the combination. However, with regard to the lifetime, the effect of the positive electrode active material having a longer lifetime may be obtained more unexpectedly. By combining a material and a positive electrode active material having a relatively poor life but other good performance, a high output, large capacity, long life lithium secondary battery of the present invention could be achieved.

  Examples of preferable combinations include a positive electrode active material represented by the composition formula (4) and a positive electrode active material represented by the composition formula (6), a positive electrode active material represented by the composition formula (4) and the composition formula (7). ), A positive electrode active material represented by composition formula (4), a positive electrode active material represented by composition formula (8), a positive electrode active material represented by composition formula (4), and a composition formula A positive electrode active material represented by (9), a positive electrode active material represented by composition formula (5), a positive electrode active material represented by composition formula (6), and a positive electrode active material represented by composition formula (5) Cathode active material represented by composition formula (7), cathode active material represented by composition formula (5) and cathode active material represented by composition formula (8), cathode active material represented by composition formula (5) The material and the positive electrode active material represented by the composition formula (9), the positive electrode active material represented by the composition formula (6), the positive electrode active material represented by the composition formula (7), and the composition formula (6) The positive electrode active material represented by active material with formula (8), a cathode active material represented by the composition formula as a cathode active material represented by the composition formula (6) (9), and the like. Particularly preferably, the positive electrode active material represented by the composition formula (5) and the positive electrode active material represented by the composition formula (7), the positive electrode active material represented by the composition formula (6) and the composition formula (7) are represented. Cathode active material.

  The combination ratio is not particularly limited, but is preferably 10:90 to 90:10, and more preferably 20:80 to 80:20.

The positive electrode used in the lithium secondary battery of the present invention contains two or more types of positive electrode active materials having different compositions, and at least one of the positive electrode active materials has a BET specific surface area, an average primary particle size, The median diameter d ₅₀ and / or the tap density (hereinafter abbreviated as “the following physical properties”) are preferably within the following specific ranges. Among two or more types of positive electrode active materials having different compositions, a positive electrode active material having a physical property not within the following range may be contained, but two or more positive electrode active materials have a certain physical property within the following range. Preferably there is. The content ratio of “all positive electrode active materials in which any of the following physical properties are within the following specific range” with respect to “all positive electrode active materials contained in the positive electrode” is not particularly limited depending on the physical properties. , 30% by mass or more is preferable, 50% by mass or more is more preferable, and all of them are particularly preferable. Each of the two or more positive electrode active materials contained in the positive electrode preferably has any one or more of the following physical properties within the following specific ranges, but more preferably any two or more. It is particularly preferable that the number is any three or more, and it is most preferable that all of the following physical properties are within the following specific ranges.

[[[BET specific surface area]]]
The BET specific surface area of at least one positive electrode active material of the positive electrode active material contained in the positive electrode used for the secondary battery of the present invention is preferably 0.4 m ² / g or more, more preferably 0.5 m ² / g or more, Preferably it is 0.6 m ² / g or more, and the upper limit is 2 m ² / g or less, preferably 1.8 m ² / g or less, more preferably 1.5 m ² / g or less. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered, and if the BET specific surface area is larger, the tap density is difficult to increase, and there may be a problem in applicability when forming the positive electrode active material.

  The BET specific surface area is determined by using a surface area meter (for example, a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample for 30 minutes at 150 ° C. under nitrogen flow, and then measuring the relative pressure of nitrogen relative to atmospheric pressure. It is defined by a value measured by a nitrogen adsorption BET one-point method using a gas flow method using a nitrogen-helium mixed gas that is accurately adjusted to have a value of 0.3.

[[[Average primary particle size]]]
The average primary particle size of at least one positive electrode active material of the positive electrode active material contained in the positive electrode used for the secondary battery of the present invention is preferably 0.1 μm or more, more preferably 0.2 μm or more, and still more preferably 0.8. It is 3 μm or more, most preferably 0.4 μm or more, and the upper limit is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, and most preferably 1 μm or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the specific surface area is greatly reduced, so that there is a high possibility that battery performance such as output characteristics will deteriorate. is there. On the other hand, when the value falls below the lower limit, there is a case where problems such as inferior reversibility of charge / discharge are usually caused because crystals are not developed.

  The primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done. In some cases, primary particles are aggregated to form secondary particles. Even in this case, only the primary particles are measured.

[[[Median diameter d ₅₀ ]]]
The median diameter d ₅₀ of particles of at least one positive electrode active material of the positive electrode active material contained in the positive electrode used in the secondary battery of the present invention (secondary particles when primary particles are aggregated to form secondary particles) Diameter) is preferably 1 μm or more, more preferably 1.2 μm or more, still more preferably 1.5 μm or more, most preferably 2 μm or more, and the upper limit is preferably 20 μm or less, more preferably 18 μm or less, still more preferably It is 16 μm or less, most preferably 15 μm or less. If the lower limit is not reached, a high tap density product may not be obtained. If the upper limit is exceeded, it takes time for the diffusion of lithium in the particles. When a conductive material, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur. Here, different median size d ₅₀ by mixing a positive electrode active material of two or more with, it is also possible to further improve the filling property at the time of the positive electrode creation.

The median diameter d ₅₀ in the present invention is measured by a known laser diffraction / scattering particle size distribution measuring apparatus. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

[[[Tap density]]]
The tap density of at least one positive electrode active material of the positive electrode active material contained in the positive electrode used for the secondary battery of the present invention is preferably 1.3 g / cm ³ or more, more preferably 1.5 g / cm ³ or more, and still more preferably. Is 1.6 g / cm ³ or more, and most preferably 1.7 g / cm ³ or more. If the tap density of the positive electrode active material is lower than the lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of the conductive material and the binder increases. In some cases, the filling rate of the substance is limited, and the battery capacity is limited. By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as large as possible, but there is no particular upper limit. The upper limit is preferably 2.7 g / cm ³ or less, more preferably 2.5 g / cm ³ or less.

In the present invention, the tap density is measured by passing a sieve having a mesh size of 300 μm, dropping a sample onto a 20 cm ³ tapping cell to fill the cell volume, and then measuring a powder density measuring device (for example, a tap denser manufactured by Seishin Enterprise Co., Ltd.). , Tapping with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume and the weight of the sample is defined as the tap density.

[[[Surface coating]]]
At least one positive electrode active material of the positive electrode active material contained in the positive electrode used for the secondary battery of the present invention has a material having a composition different from that of the positive electrode active material constituting the main body of the positive electrode active material (hereinafter, “ It is preferable to use a material to which “surface adhering substance” is abbreviated. Examples of the positive electrode active material constituting the main body include the positive electrode active material having the above-described composition. Examples of the surface-adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, Examples thereof include sulfates such as magnesium sulfate, calcium sulfate and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate, and carbon.

  These surface adhering substances are, for example, a method of impregnating and drying a positive electrode active material constituting the main body by dissolving or suspending in a solvent, and a positive electrode constituting the main body by dissolving or suspending a surface adhering substance precursor in a solvent. After the impregnation is added to the active material, it can be attached to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and simultaneously firing. In addition, when making carbon adhere, the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.

  The amount of the surface adhering substance is by mass with respect to the positive electrode active material constituting the main body, preferably as a lower limit, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and an upper limit, preferably 20% by mass or less. More preferably, it is used at 10 mass% or less, More preferably, it is used at 5 mass% or less. The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. However, when the amount of the adhering quantity is too small, the effect is not sufficiently exhibited. If the amount is too large, the resistance may increase in order to inhibit the entry and exit of lithium ions.

[[[shape]]]
The shape of the particles of at least one positive electrode active material of the positive electrode active material contained in the positive electrode used in the secondary battery of the present invention is a lump, polyhedron, sphere, ellipsoid, plate, needle, Columnar shapes and the like are used, and among them, primary particles are preferably aggregated to form secondary particles, and the shape of the secondary particles is preferably spherical or elliptical. In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, it is preferable that the primary particles are aggregated to form secondary particles, rather than a single particle active material having only primary particles, in order to relieve expansion and contraction stress and prevent deterioration. In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so that the expansion and contraction of the electrode during charging and discharging is small, and the electrode is produced. The mixing with the conductive material is also preferable because it is easy to mix uniformly.

[[[Production method]]]
As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for producing a spherical or elliptical spherical active material. For example, transition metal raw materials such as transition metal nitrates and transition metal sulfates and, if necessary, raw materials of other elements are mixed with water. It is dissolved or pulverized and dispersed in a solvent such as, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , LiNO _3, etc. A method of obtaining an active material by adding a Li source of the above, a transition metal source material such as transition metal nitrate, transition metal sulfate, transition metal hydroxide, transition metal oxide, and other elements as required The raw material is dissolved or pulverized and dispersed in a solvent such as water, and is then dried and molded with a spray dryer or the like to obtain a spherical or elliptical precursor, and LiOH, Li ₂ CO ₃ , LiNO _{3 and} other Li Add the source at high temperature A method of obtaining an active material by firing, a transition metal source material such as transition metal nitrate, transition metal sulfate, transition metal hydroxide, transition metal oxide, and LiOH such as LiOH, Li ₂ CO ₃ , and LiNO ₃ Dissolve or pulverize the source and other elemental raw materials as necessary in a solvent such as water, and dry-mold them with a spray drier or the like to obtain a spherical or elliptical precursor, which is heated at a high temperature. Examples thereof include a method for obtaining an active material by firing.

[[Composition of positive electrode]]
Below, the structure of the positive electrode used for this invention is described.
[[[Electrode structure and fabrication method]]]
The positive electrode for a lithium secondary battery of the present invention is produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. Manufacture of the positive electrode using a positive electrode active material can be performed by a conventional method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form are pressure-bonded to a positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

  Two or more types of positive electrode active materials may be mixed in advance and used, or may be mixed by adding them simultaneously when forming the positive electrode.

[[[Positive electrode active material]]]
The content of the positive electrode active material used in the positive electrode of the lithium secondary battery of the present invention in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. is there. Moreover, an upper limit becomes like this. Preferably it is 95 mass% or less, More preferably, it is 93 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient.

[[[Conductive material]]]
A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. Conversely, if the content is higher than this range, the battery capacity may decrease.

[[[Binder]]]
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that can be dissolved or dispersed in the liquid medium used in electrode production may be used. , Polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, and other resin polymers; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber , Rubber polymers such as butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric polymer such as isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer Soft resinous polymers such as polymers; Fluoropolymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers; alkali metal ions (especially lithium ions) And a polymer composition having ion conductivity. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60% by mass. % Or less, more preferably 40% by mass or less, and most preferably 10% by mass or less. When the ratio of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, battery capacity and conductivity may be reduced.

[[[Liquid medium]]]
The liquid medium for forming the slurry may be any type of solvent that can dissolve or disperse the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. There is no particular limitation, and either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.

[[[Thickener]]]
In particular, when an aqueous medium is used, it is preferable to make a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. When a thickener is further added, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. The upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below this range, applicability may be significantly reduced. If it exceeds, the ratio of the active material in the positive electrode active material layer may decrease, and there may be a problem that the capacity of the battery decreases and a problem that the resistance between the positive electrode active materials increases.

[[[Consolidation]]]
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. Density of the positive electrode active material layer is preferably 1.5 g / cm ³ or more as a lower limit, more preferably 2 g / cm ^3, and even more preferably at 2.2 g / cm ³ or more, the upper limit, preferably 3.5g / Cm ³ or less, more preferably 3 g / cm ³ or less, and even more preferably 2.8 g / cm ³ or less. If this range is exceeded, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface may decrease, and the charge / discharge characteristics at a high current density may decrease. On the other hand, if it is lower, the conductivity between the active materials may be reduced, and the battery resistance may be increased.

[[[Current collector]]]
There is no restriction | limiting in particular as a material of a positive electrode electrical power collector, A well-known thing can be used arbitrarily. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. Examples include thin films and carbon cylinders. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. Although the thickness of the thin film is arbitrary, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.

  The thickness ratio between the current collector and the positive electrode active material layer is not particularly limited, but (thickness of active material layer on one side immediately before non-aqueous electrolyte injection) / (thickness of current collector) is 20 or less. More preferably, it is 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the positive electrode active material increases and the battery capacity may decrease.

[[[Electrode area]]]
When using the non-aqueous electrolyte of the present invention, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of increasing the stability at high output and high temperature. Specifically, the sum of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more. The outer surface area of the outer case is the total area obtained by calculation from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal in the case of a bottomed square shape. . In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.

[[[Discharge capacity]]]
When the non-aqueous electrolyte for secondary battery of the present invention is used, the electric capacity of the battery element housed in one battery case of the secondary battery (electric capacity when the battery is discharged from the fully charged state to the discharged state) ) Is 3 ampere hours (Ah) or more, since the effect of improving output characteristics is increased. Therefore, the positive electrode plate is preferably designed so that the discharge capacity is fully charged and is 3 ampere hours (Ah) or more and 20 Ah or less, and more preferably 4 Ah or more and 10 Ah or less. If it is less than 3 Ah, the voltage drop due to the electrode reaction resistance becomes large when taking out a large current, and the power efficiency may deteriorate. Above 20 Ah, the electrode reaction resistance decreases and the power efficiency improves, but the temperature distribution due to the internal heat generation of the battery during pulse charge / discharge is large, the durability of repeated charge / discharge is inferior, and abnormalities such as overcharge and internal short circuit When the heat release efficiency deteriorates due to sudden heat generation at the time, the probability that the internal pressure rises and the gas release valve operates (valve operation), or the battery contents erupt violently (explosion) increases. There is.

[[[Positive electrode plate thickness]]]
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material is relative to one side of the current collector. The lower limit is preferably 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 200 μm or less, more preferably 100 μm or less.

<Lithium secondary battery>
The lithium secondary battery of the present invention will be described in detail below.

[Battery shape]
The battery shape is not particularly limited, and examples thereof include a bottomed cylindrical shape, a bottomed square shape, a thin shape, a sheet shape, and a paper shape. When incorporating into a system or device, in order to increase the volumetric efficiency and improve the storage capacity, it may be of a different shape such as a horseshoe shape or a comb shape considering the fit in the peripheral system arranged around the battery. . From the viewpoint of efficiently releasing the heat inside the battery to the outside, a rectangular shape having at least one surface that is relatively flat and has a large area is preferable.

  In a battery having a bottomed cylindrical shape, since the outer surface area with respect to the power generating element to be filled becomes small, it is preferable to design so that Joule heat generated by the internal resistance at the time of charging and discharging efficiently escapes to the outside. Moreover, it is preferable to design so that the filling ratio of the substance having high thermal conductivity is increased and the temperature distribution inside is reduced.

In the bottomed square shape, the ratio between the area S of the largest surface (the product of the width and height of the outer dimensions excluding the terminal portion, unit cm ² ) and the thickness T (unit cm) of the battery outer shape The 2S / T value is preferably 100 or more, and more preferably 200 or more. By increasing the maximum surface, it is possible to improve characteristics such as cycle performance and high-temperature storage even for high-power and large-capacity batteries, and increase heat dissipation efficiency during abnormal heat generation. Can be prevented from becoming a dangerous state.

[Battery configuration]
The rechargeable lithium secondary battery of the present invention includes the above-described positive electrode and negative electrode capable of occluding and releasing lithium ions, the above-described non-aqueous electrolyte, a separator disposed between the positive electrode and the negative electrode, a current collecting terminal, and It is comprised at least by an exterior case etc. If necessary, a protective element may be mounted inside the battery and / or outside the battery.

[Negative electrode]
Below, the negative electrode used for the lithium secondary battery of this invention is demonstrated.
[[Negative electrode active material]]
The negative electrode active material used for the negative electrode is described below.
[[[composition]]]
The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium simple substance And lithium alloys such as lithium aluminum alloy and metals that can form alloys with lithium such as Sn and Si. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Of these, carbonaceous materials or lithium composite oxides are preferably used from the viewpoint of safety.

  The metal composite oxide is not particularly limited as long as it can occlude and release lithium, but preferably contains titanium and / or lithium as a constituent component from the viewpoint of high current density charge / discharge characteristics.

As a carbonaceous material,
(1) natural graphite,
(2) Artificial carbonaceous material and artificial graphite material; carbonaceous material [for example, natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or those obtained by oxidizing these pitches, needle coke, pitch Coke and carbon materials partially graphitized, furnace black, acetylene black, pyrolysis products of organic substances such as pitch-based carbon fibers, carbonized organic substances (for example, coal tar pitch from soft pitch to hard pitch, or dry distillation Coal heavy oil such as liquefied oil, normal pressure residual oil, direct current heavy oil of reduced pressure residual oil, cracked petroleum heavy oil such as ethylene tar produced during thermal decomposition of crude oil, naphtha, etc., acenaphthylene, Aromatic hydrocarbons such as decacyclene, anthracene, phenanthrene, N-ring compounds such as phenazine and acridine, thiophene, bithiophene S-ring compound, polyphenylene such as biphenyl and terphenyl, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized product of these, organic polymer such as nitrogen-containing polyacrylonitrile, polypyrrole, sulfur-containing polythiophene, Organic polymers such as polystyrene, natural polymers such as polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan and saccharose, thermoplastic resins such as polyphenylene sulfide and polyphenylene oxide, furfuryl alcohol resin, phenol -Thermosetting resins such as formaldehyde resin and imide resin) and their carbides or carbonizable organic substances in low molecular organic solvents such as benzene, toluene, xylene, quinoline, n-hexane, and the like Carbides] The one or more times in the range of 400 to 3200 ° C. heat treated carbon material,
(3) a carbon material in which the negative electrode active material layer is composed of at least two types of carbonaceous materials having different crystallinity and / or has an interface in contact with the different crystalline carbonaceous materials,
(4) A carbon material in which the negative electrode active material layer is composed of at least two kinds of carbonaceous materials having different orientations and / or has an interface in contact with the carbonaceous materials having different orientations,
Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics.

[[Negative electrode configuration, physical properties, preparation method]]
Regarding the properties of the carbonaceous material, the negative electrode containing the carbonaceous material, the electrodeification method, the current collector, and the lithium ion secondary battery, any one or more of (1) to (19) shown below It is desirable to satisfy

(1) X-ray parameters For carbonaceous materials, the d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method is preferably 0.335 nm or more, and the upper limit is usually It is desired that the thickness is 0.36 nm or less, preferably 0.35 nm or less, and more preferably 0.345 nm or less. The crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction by the Gakushin method is preferably 1 nm or more, and more preferably 1.5 nm or more.

(2) Ash content The ash content in the carbonaceous material is 1% by mass or less, particularly 0.5% by mass or less, especially 0.1% by mass or less, and the lower limit is 1 ppm or more with respect to the total mass of the carbonaceous material. It is preferable that If the above range is exceeded, deterioration of battery performance due to reaction with the non-aqueous electrolyte during charge / discharge may not be negligible. Below this range, the manufacturing process requires a lot of time, energy and equipment for preventing contamination, which may increase costs.

(3) Volume-based average particle diameter The volume-based average particle diameter of the carbonaceous material is usually 1 μm or more, preferably 3 μm or more, more preferably a volume-based average particle diameter (median diameter) determined by a laser diffraction / scattering method. Is 5 μm or more, more preferably 7 μm or more. Moreover, an upper limit is 100 micrometers or less normally, Preferably it is 50 micrometers or less, More preferably, it is 40 micrometers or less, More preferably, it is 30 micrometers or less, Most preferably, it is 25 micrometers or less. If it falls below the above range, the irreversible capacity may increase, leading to loss of the initial battery capacity. On the other hand, when the above range is exceeded, when an electrode is produced by coating, a non-uniform coating surface tends to be formed, which may be undesirable in the battery production process.

  In the present invention, the volume-based average particle size is determined by dispersing carbon powder in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering type particle size. It is defined by the median diameter measured using a distribution meter (for example, LA-700 manufactured by Horiba, Ltd.).

(4) Raman R value, Raman half-value width The Raman R value of the carbonaceous material measured using the argon ion laser Raman spectrum method is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more. The upper limit is 1.5 or less, preferably 1.2 or less, more preferably 1.0 or less, and still more preferably 0.5 or less. When the Raman R value is below this range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge / discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, the reactivity with the non-aqueous electrolyte will increase, and the efficiency and gas generation may increase.

Further, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} carbonaceous material of the present invention is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and the upper limit is usually 100 cm ⁻¹ or less, preferably The range is 80 cm ⁻¹ or less, more preferably 60 cm ⁻¹ or less, and still more preferably 40 cm ⁻¹ or less. When the Raman half width is less than this range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge and discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, the reactivity with the non-aqueous electrolyte will increase, and the efficiency and gas generation may increase.

The Raman spectrum is measured using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), the sample is naturally dropped into the measurement cell and filled, and the sample surface in the cell is irradiated with an argon ion laser beam. The cell is rotated in a plane perpendicular to the laser beam. The obtained Raman spectrum, the intensity I _A of the peak P _A in the vicinity of 1580 cm ^-1, and measuring the intensity I _B of a peak P _B in the vicinity of 1360 cm ^-1, the intensity ratio R (R = I _B / I _A ) Is calculated and defined as the Raman R value of the carbonaceous material. Further, the half width of the peak P _A near 1580 cm ^{−1 of} the obtained Raman spectrum is measured, and this is defined as the Raman half width of the carbonaceous material.

The Raman measurement conditions here are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
・ Raman R value, half width analysis: Background processing ・ Smoothing processing: Simple average, 5 points of convolution

(5) BET specific surface area The specific surface area of the carbonaceous material of the present invention measured using the BET method is usually 0.1 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1.0 m ^2. / G or more, more preferably 1.5 m ² / g or more. The upper limit is usually 100 m ² / g or less, preferably 25 m ² / g or less, more preferably 15 m ² / g or less, and still more preferably 10 m ² / g or less. When the value of the specific surface area is less than this range, the acceptability of lithium is likely to deteriorate during charging when used as a negative electrode material, and lithium may easily precipitate on the electrode surface. On the other hand, if it exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte increases, gas generation tends to increase, and a preferable battery may be difficult to obtain.

  The specific surface area according to the BET method is determined by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Riken Okura), preliminarily drying the sample at 350 ° C. for 15 minutes under a nitrogen flow, and then comparing the nitrogen relative to the atmospheric pressure. A value measured by a nitrogen adsorption BET one-point method using a gas flow method is used, using a nitrogen helium mixed gas accurately adjusted so that the pressure value becomes 0.3.

(6) Pore size distribution The pore size distribution of the carbonaceous material used in the present invention is determined by mercury porosimetry (mercury intrusion method), and the pore diameter is within a particle corresponding to 0.01 μm or more and 1 μm or less. The amount of voids, irregularities due to particle surface steps, contact surfaces between particles, etc. is 0.01 mL / g or more, preferably 0.05 mL / g or more, more preferably 0.1 mL / g or more, and the upper limit is 0.6 mL. / G or less, preferably 0.4 mL / g or less, more preferably 0.3 mL / g or less. If it exceeds this range, a large amount of binder may be required when forming an electrode plate. If it is less than the range, the high current density charge / discharge characteristics may be deteriorated, and the effect of mitigating the expansion / contraction of the electrode during charge / discharge may not be obtained.

  Further, the total pore volume corresponding to the pore diameter in the range of 0.01 μm to 100 μm is preferably 0.1 mL / g or more, more preferably 0.25 mL / g or more, still more preferably 0.4 mL / g or more, The upper limit is 10 mL / g or less, preferably 5 mL / g or less, more preferably 2 mL / g or less. If this range is exceeded, a large amount of binder may be required during electrode plate formation. If it is less than that, it may not be possible to obtain the effect of dispersing the thickener or the binder during the electrode plate formation.

  The average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, further preferably 0.5 μm or more, and the upper limit is 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less. Beyond this range, a large amount of binder may be required. If it is less, the high current density charge / discharge characteristics may deteriorate.

  As an apparatus for mercury porosimetry, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) was used. About 0.2 g of a sample was sealed in a powder cell and pretreated by degassing for 10 minutes at room temperature under vacuum (50 μmHg or less). Subsequently, the pressure was reduced to 4 psia (about 28 kPa), mercury was introduced, the pressure was increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure was reduced to 25 psia (about 170 kPa). The number of steps at the time of pressure increase was 80 points or more, and the mercury intrusion amount was measured after an equilibration time of 10 seconds in each step. The pore size distribution was calculated from the mercury intrusion curve thus obtained using the Washburn equation. The surface tension (γ) of mercury was 485 dyne / cm, and the contact angle (ψ) was 140 °. As the average pore diameter, the pore diameter when the cumulative pore volume was 50% was used.

(7) Circularity Using circularity as the degree of sphericity of the carbonaceous material, the circularity of particles having a particle size in the range of 3 to 40 μm is preferably 0.1 or more, particularly preferably 0.5 or more. Preferably it is 0.8 or more, more preferably 0.85 or more, and most preferably 0.9 or more. High circularity is preferable because high current density charge / discharge characteristics are improved.
The circularity is defined by the following formula. When the circularity is 1, a theoretical sphere is obtained.
Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  As the value of the circularity, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) is used, and about 0.2 g of a sample is mixed with polyoxyethylene (20) sorbitan monolaurate as a surfactant. Particles having a detection range of 0.6 to 400 μm and a particle size in the range of 3 to 40 μm after being dispersed in a 0.2 mass% aqueous solution (about 50 mL) and irradiated with an ultrasonic wave of 28 kHz for 1 minute at an output of 60 W Use the value measured for.

  The method for improving the degree of circularity is not particularly limited, but a spheroidized sphere is preferable because the shape of the interparticle void when the electrode body is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approximating a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by an adhesive force possessed by a binder or the particles Is mentioned.

(8) True density The true density of the carbonaceous material is usually 1.4 g / cm ³ or more, preferably 1.6 g / cm ³ or more, more preferably 1.8 g / cm ³ or more, and still more preferably 2.0 g / cm ^3. cm ³ and the upper limit is 2.26 g / cm ³ or less. The upper limit is the theoretical value of graphite. Below this range, the crystallinity of the carbon is too low and the initial irreversible capacity may increase. In the present invention, the true density is defined by a value measured by a liquid phase substitution method (pycnometer method) using butanol.

(9) Tap density The tap density of the carbonaceous material is usually 0.1 g / cm ³ or more, preferably 0.5 g / cm ³ or more, more preferably 0.7 g / cm ³ or more, and particularly preferably 1.0 g / cm ^3. It is desired to be cm ³ or more. The upper limit is preferably 2 g / cm ³ or less, more preferably 1.8 g / cm ³ or less, and particularly preferably 1.6 g / cm ³ or less. When the tap density is below this range, the packing density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, there are too few voids between the particles in the electrode, it becomes difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics. The tap density is measured by a method similar to the method described in the section of the positive electrode and is defined thereby.

(10) Orientation ratio The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. Below this range, the high-density charge / discharge characteristics may deteriorate.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. X-ray diffraction is performed by setting a molded body obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm and compressing it at 600 kgf / cm ^{2 so} that it is flush with the surface of the measurement sample holder. Measure. A ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated from the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, and defined as the orientation ratio of the active material.

The X-ray diffraction measurement conditions here are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degree, light receiving slit = 0.15 mm, scattering slit = 0.5 degree. Measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

(11) Aspect ratio (powder)
The aspect ratio is theoretically 1 or more, and the upper limit is 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaking or a uniform coated surface may not be obtained during electrode plate formation, and the high current density charge / discharge characteristics may deteriorate. The aspect ratio is expressed as A / B, where the longest diameter A of the carbonaceous material particles when observed three-dimensionally and the shortest diameter B perpendicular to the diameter A. The carbon particles are observed with a scanning electron microscope capable of magnifying observation. Arbitrary 50 graphite particles fixed on the end face of a metal plate having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted, and A and B are measured. Find the average value.

(12) Sub-material mixing “Sub-material mixing” means that two or more carbonaceous materials having different properties are contained in the negative electrode and / or the negative electrode active material. The properties described here include one or more of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Show properties. Particularly preferred embodiments include that the volume-based particle size distribution is not symmetrical when the median diameter is centered, that two or more carbonaceous materials having different Raman R values are contained, and the X-ray parameters are It is different.

  As an example of the effect, carbonaceous material such as natural graphite, graphite such as artificial graphite, carbon black such as acetylene black, amorphous carbon such as needle coke, etc. is contained as a conductive material, so that electric resistance is increased. It can be reduced. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. When added as a conductive material, it is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is 45% by mass or less, preferably 40% by mass. It is a range. Below this range, the effect of improving conductivity may be difficult to obtain. If it exceeds, the initial irreversible capacity may increase.

(13) Electrode production The electrode may be produced by a conventional method. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do. The thickness of the negative electrode active material layer per side in the stage immediately before the non-aqueous electrolyte injection process of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is 150 μm or less, preferably 120 μm. Hereinafter, it is more preferably 100 μm or less. If it exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may deteriorate. On the other hand, below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

(14) Current collector Any known current collector can be used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is particularly preferable from the viewpoint of ease of processing and cost. When the current collector is a metal material, examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector. When the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.

  A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to. Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

The following physical properties are desired for the current collector substrate.
(1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material thin film forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.05 μm or more, preferably 0.1 μm or more, particularly The upper limit is usually 1.5 μm or less, preferably 1.3 μm or less, particularly preferably 1.0 μm or less. By setting the average surface roughness (Ra) of the current collector substrate within the range between the lower limit and the upper limit described above, good charge / discharge cycle characteristics can be expected. By setting it to the above lower limit or more, the area of the interface with the active material thin film is increased, and the adhesion with the active material thin film is improved. The upper limit of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally difficult to obtain as foils having a practical thickness as a battery. 1.5 μm or less is preferable.

(2) Tensile strength The tensile strength of the current collector substrate is not particularly limited, but is usually 100 N / mm ² or more, preferably 250 N / mm ² or more, more preferably 400 N / mm ² or more, and particularly preferably 500 N / mm ^2. That's it. The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as the elongation rate. If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(3) 0.2% proof stress of 0.2% proof stress current collector substrate is not particularly limited, normally 30 N / mm ² or more, preferably 150 N / mm ² or more, particularly preferably 300N / mm ² or more . The 0.2% proof stress is the magnitude of the load necessary to give a plastic (permanent) strain of 0.2%. It means that The 0.2% proof stress in the present invention is measured by the same apparatus and method as the elongation rate. If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the active material thin film accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. it can.

  Although the thickness of a metal thin film is arbitrary, it is 1 micrometer or more normally, Preferably it is 3 micrometers or more, More preferably, it is 5 micrometers or more. Moreover, an upper limit is 1 mm or less normally, Preferably it is 100 micrometers or less, More preferably, it is 30 micrometers or less. If the thickness is less than 1 μm, the strength may be reduced, and application may be difficult. On the other hand, if the thickness exceeds 100 μm, it may be difficult to change the shape of a desired electrode by winding or the like. The metal thin film may be mesh.

(15) Ratio of thickness of current collector and active material layer The ratio of the thickness of current collector and active material layer is not particularly limited, but (thickness of active material layer on one side immediately before non-aqueous electrolyte injection) ) / (Current collector thickness) is preferably 150 or less, particularly preferably 20 or less, more preferably 10 or less, and the lower limit is preferably 0.1 or more, particularly preferably 0.4 or more. More preferably, it is in the range of 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the negative electrode active material increases and the battery capacity may decrease.

(16) Electrode density The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1.0 g / cm ³ or more, more preferably Is 1.2 g / cm ³ , more preferably 1.3 g / cm ³ or more, and the upper limit is 2.0 g / cm ³ or less, preferably 1.9 g / cm ³ or less, more preferably 1.8 g / cm ^3. Hereinafter, the range is more preferably 1.7 g / cm ³ or less. Exceeding this range may destroy active material particles, leading to an increase in initial irreversible capacity and deterioration of high current density charge / discharge characteristics due to reduced permeability of the non-aqueous electrolyte near the current collector / active material interface. . On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and the capacity per unit volume may be lowered.

(17) Binder The binder for binding the active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used during electrode production. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile-butadiene rubber), rubber-like polymers such as ethylene-propylene rubber; styrene / butadiene / styrene block copolymers or hydrogenated products thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymer such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinegar Soft resinous polymers such as vinyl copolymers and propylene / α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymers Molecule: a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The solvent for forming the slurry is not particularly limited as long as it is a solvent that can dissolve or disperse the active material, the binder, and the thickener and conductive material used as necessary. Either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, a mixed solvent of alcohol and water, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, acrylic acid. Methyl, diethyltriamine, N, N-dimethylaminopropylamine, propylene oxide, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine , Methyl naphthalene, hexane and the like. In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-described thickener, and a slurry is formed using a latex such as SBR. In addition, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder to the active material is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is 20% by mass or less, preferably 15%. It is in the range of not more than mass%, more preferably not more than 10 mass%, still more preferably not more than 8 mass%. When it exceeds this range, the binder ratio in which the binder amount does not contribute to the battery capacity increases, and the battery capacity may be reduced. On the other hand, if it is lower, the strength of the negative electrode may be reduced. In particular, when the main component contains a rubbery polymer typified by SBR, the ratio of the binder to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 0.8%. The upper limit is 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. Further, when the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the active material is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more. As an upper limit, it is 15 mass% or less, Preferably it is 10 mass% or less, More preferably, it is the range of 8 mass% or less.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Further, when a thickener is blended, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. Is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below this range, applicability may be significantly reduced. If it exceeds the upper limit, the ratio of the active material in the negative electrode active material layer may be reduced, resulting in a problem that the capacity of the battery is reduced and a problem that the resistance between the negative electrode active materials is increased.

(18) Electrode orientation ratio The electrode orientation ratio is preferably 0.001 or more, particularly preferably 0.005 or more, more preferably 0.01 or more, and the upper limit is 0.67 or less, which is a theoretical value. Below this range, the high-density charge / discharge characteristics may deteriorate.

  The measurement of the electrode plate orientation ratio is as follows. About the negative electrode after pressing to the target density, the active material orientation ratio of the electrode is measured by X-ray diffraction. The specific method is not particularly limited. As a standard method, peak separation is performed by fitting peaks of carbon (110) diffraction and (004) diffraction by X-ray diffraction using asymmetric Pearson VII as a profile function. The integrated intensities of the peaks of (110) diffraction and (004) diffraction are calculated. From the obtained integrated intensity, a ratio represented by (110) diffraction integrated intensity / (004) diffraction integrated intensity is calculated. The electrode active material orientation ratio calculated by the measurement ratio is defined as the electrode plate orientation ratio.

The X-ray diffraction measurement conditions here are as follows. “2θ” indicates a diffraction angle.
-Target: Cu (Kα ray) graphite monochromator-Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree-Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds (004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds Sample preparation: Fix the electrode to the glass plate with double-sided tape with a thickness of 0.1 mm

(19) Impedance The resistance of the negative electrode when charged to 60% of the nominal capacity from the discharged state is preferably 100Ω or less, particularly preferably 50Ω or less, more preferably 20Ω or less, and / or the double layer capacity is 1 ×. 10 ⁻⁶ F or more is preferable, particularly preferably 1 × 10 ⁻⁵ F, and more preferably 1 × 10 ⁻⁴ F. Within this range, the output characteristics are good and preferable.

The resistance and double layer capacity of the negative electrode are measured by the following procedure. The lithium-ion secondary battery to be measured is charged at a current value that can be charged for 5 hours in a nominal capacity, then maintained in a state where it is not charged / discharged for 20 minutes, and then discharged at a current value that can be discharged in 1 hour for a nominal capacity. The capacity when the capacity is 80% or more of the nominal capacity is used. About the lithium ion secondary battery of the above-mentioned discharge state, it charges to 60% of a nominal capacity with the electric current value which can charge a nominal capacity in 5 hours, Immediately transfers a lithium ion secondary battery in the glove box under argon gas atmosphere. Here, the lithium ion secondary battery is quickly disassembled and taken out in a state where the negative electrode is not discharged or short-circuited, and if it is a double-sided coated electrode, the electrode active material on one side is peeled off without damaging the electrode active material on the other side. Two electrodes are punched to 12.5 mmφ, and are opposed to each other so that the active material surface does not shift through a separator. 60μL of non-aqueous electrolyte used in the battery was dropped between the separator and both negative electrodes, and kept in close contact with the outside air, and the current collector of both negative electrodes was made conductive and the AC impedance method was carried out. To do. The measurement was performed at a temperature of 25 ° C. and a complex impedance measurement was performed in a frequency band of 10 ⁻² to 10 ⁵ Hz, and the surface resistance (R) was obtained by approximating the arc of the negative resistance component of the obtained Cole-Cole plot with a semicircle. And double layer capacity | capacitance (Cdl) is calculated | required.

  The area of the negative electrode plate is not particularly limited, but is designed to be slightly larger than the opposing positive electrode plate so that the positive electrode plate does not protrude from the negative electrode plate. From the viewpoint of suppressing the life of a cycle in which charge and discharge are repeated and deterioration due to high temperature storage, it is preferable that the area be as close to the positive electrode as possible, since the ratio of electrodes that work more uniformly and effectively is increased and the characteristics are improved. In particular, when the electrode is used at a large current, the design of the electrode area is important.

  The thickness of the negative electrode plate is designed according to the positive electrode plate to be used and is not particularly limited, but the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 μm or more, Preferably it is 20 micrometers or more, More preferably, it is 30 micrometers or more, and an upper limit is 150 micrometers or less, Preferably it is 120 micrometers or less, More preferably, it is 100 micrometers or less.

[Separator]
The separator used in the present invention has a predetermined mechanical strength that electrically insulates both electrodes, has a high ion permeability, and has resistance to oxidation on the side in contact with the positive electrode and reduction on the negative electrode side. There is no particular limitation as long as it has both. As a material for the separator having such required characteristics, a resin, an inorganic material, glass fiber, or the like is used. As the resin, olefin polymer, fluorine polymer, cellulose polymer, polyimide, nylon and the like are used. Specifically, it is preferable to select from materials that are stable with respect to the non-aqueous electrolyte and have excellent liquid retention properties, and it is preferable to use a porous sheet or nonwoven fabric made of polyolefin such as polyethylene and polypropylene. preferable. As the inorganic substance, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used, and those having a particle shape or fiber shape are used. As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed on both surfaces of the positive electrode using alumina particles having a 90% particle size of 1 μm or less as a binder.

[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either may be used. The ratio of the volume of the electrode group to the battery internal volume (hereinafter referred to as electrode group occupancy) is preferably 40% to 90%, and more preferably 50% to 80%. When the electrode group occupancy is less than 40%, the battery capacity becomes small, and when it exceeds 90%, the void space is small, the battery becomes hot, the member expands, or the vapor pressure of the liquid component of the electrolyte In some cases, the internal pressure rises due to an increase in the pressure, which deteriorates various characteristics such as charge / discharge repetition performance as a battery and high-temperature storage, and further, a gas release valve that releases the internal pressure to the outside may operate.

[Current collection structure]
The current collecting structure is not particularly limited, but in order to more effectively realize the output characteristics improvement by the non-aqueous electrolyte solution of the present invention, it is necessary to make the structure to reduce the resistance of the wiring part and the joint part. is there. When such an internal resistance is small, the effect of using the nonaqueous electrolytic solution of the present invention is exhibited particularly well.

  In the case where the electrode group has the laminated structure described above, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

  By optimizing the above structure, the internal resistance can be made as small as possible. In a battery used at a large current, the impedance measured by the 10 kHz AC method (hereinafter abbreviated as “DC resistance component”) is preferably 10 milliohms (mΩ) or less, and the DC resistance component is 5 milliohms (mΩ). It is more preferable to make it below. When the direct current resistance component is 0.1 milliohms or less, the high output characteristics are improved, but the ratio of the current collecting structure used increases and the battery capacity may decrease.

  The non-aqueous electrolyte of the present invention is effective in reducing reaction resistance related to lithium insertion / extraction with respect to the electrode active material, which is considered to be a factor that can realize good output characteristics. However, it was found that a battery having a large direct current resistance is inhibited by the direct current resistance, and the effect of reducing the reaction resistance cannot be reflected 100% on the output characteristics. This can be improved by using a battery having a small DC resistance component, and the effect of the non-aqueous electrolyte solution of the present invention can be sufficiently exhibited. From the viewpoint of drawing out the effect of the non-aqueous electrolyte and producing a battery having high output characteristics, this requirement and the electric capacity of the battery element housed in one battery exterior of the secondary battery described above ( It is particularly preferable to satisfy the requirement that the electric capacity when the battery is discharged from the fully charged state to the discharged state is 3 ampere hours (Ah) or more at the same time.

[Exterior case]
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In the exterior case using the above metals, a laser-sealed, resistance-welded, ultrasonic welding is used to weld the metals together to form a sealed sealed structure, or a caulking structure using the above-mentioned metals via a resin gasket To do. Examples of the outer case using the laminate film include those having a sealed and sealed structure by heat-sealing resin layers. In order to improve the sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

[Protective element]
PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, the current flowing through the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation For example, a valve (current cutoff valve) that shuts off the current can be used. It is preferable to select a protective element that does not operate under normal use at a high current. From the viewpoint of high output, it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.

  Although the mechanism for improving the life and output by using the non-aqueous electrolyte and the positive electrode described above is not clear, the additive in the non-aqueous electrolyte is adsorbed on the surface of the positive electrode active material, so Since an undesirable side reaction with the aqueous electrolyte can be suppressed, it is considered that the resistance on the surface of the positive electrode is reduced, the output is improved, and the life is improved. In particular, in a positive electrode containing two or more kinds of positive electrode active materials, it is considered that side reaction is larger in one of the positive electrode active materials, and it is considered that the effect of improving the life is great by suppressing this effectively. Moreover, in the battery using the positive electrode active material described above, since the ratio of the resistance on the surface of the positive electrode is large with respect to the resistance of the battery, reducing the resistance on the surface of the positive electrode in this way improves the output of the battery. It is considered that the effect is large and preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

表１中、正極活物質の物性としては、前記の方法に従って、ＢＥＴ比表面積、平均一次粒子径（ＳＥＭで測定）、メジアン径ｄ_５０、タップ密度の測定を行った。 [Positive electrode active material]
The types and physical properties of the positive electrode active materials used in the following examples and comparative examples are as follows.

In Table 1, as physical properties of the positive electrode active material, the BET specific surface area, the average primary particle diameter (measured by SEM), the median diameter d ₅₀ , and the tap density were measured according to the methods described above.

[Positive electrode active material A]
The positive electrode active material A is a lithium-cobalt composite oxide synthesized by the following method, and is represented by a composition formula LiCoO ₂ . LiOH as a lithium raw material and Co (OH) ₂ as a cobalt raw material are weighed so as to have a molar ratio of Li: Co = 1: 1, respectively, and pure water is added to this to form a slurry, which is stirred and circulated. Using a medium agitation type wet bead mill, the solid content in the slurry was wet pulverized to a median diameter of 0.2 μm.

  The slurry was spray-dried with a spray dryer to obtain substantially spherical granulated particles having a particle diameter of about 9 μm, which were made of a lithium raw material and a cobalt raw material. The granulated particles were calcined at 880 ° C. for 6 hours under an air flow (a temperature raising / lowering rate of 5 ° C./min). After cooling to room temperature, it was taken out and crushed, and passed through a sieve having an opening of 45 μm to obtain a positive electrode active material A.

[Positive electrode active material B]
The positive electrode active material B is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by a composition formula Li _1.05 Ni _0.8 Co _0.2 O ₂ . NiO as a nickel raw material, Co (OH) ₂ as a cobalt raw material, Ni: Co = 80: 20 are weighed so that the molar ratio is 80:20, and pure water is added to this to form a slurry. The solid content in the slurry was wet pulverized to a median diameter of 0.25 μm using a mold wet bead mill.

  The slurry was spray-dried with a spray dryer to obtain substantially spherical granulated particles having a particle diameter of about 8 μm, which consisted of only nickel raw material and cobalt raw material. To the resulting granulated particles, add LiOH powder with a median diameter of 3 μm so that the ratio of the number of moles of Li to the total number of moles of Ni and Co is 1.05, and mix with a high speed mixer. Then, a mixed powder of granulated particles of nickel raw material and cobalt raw material and lithium raw material was obtained. This mixed powder was calcined at 740 ° C. for 6 hours under an oxygen flow (climbing temperature rate 5 ° C./min), then crushed and passed through a sieve having an opening of 45 μm to obtain a positive electrode active material B.

[Positive electrode active material C]
The positive electrode active material C is a lithium transition metal composite oxide synthesized by the following method, and is represented by a composition formula Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ . NiO as a nickel raw material, Co (OH) ₂ as a cobalt raw material, and AlOOH as an aluminum raw material are weighed so as to have a molar ratio of Ni: Co: Al = 80: 15: 5, and pure water is added to the slurry. With stirring, the solid content in the slurry was wet pulverized to a median diameter of 0.25 μm using a circulating medium stirring type wet bead mill.

  The slurry was spray-dried with a spray dryer to obtain substantially spherical granulated particles having a particle diameter of about 10 μm, which consisted of only nickel raw material, cobalt raw material and aluminum raw material. LiOH powder with a median diameter of 3 μm was added to the resulting granulated particles so that the ratio of the number of moles of Li to the total number of moles of Ni, Co, and Al was 1.05, and mixed with a high speed mixer. Thus, a mixed powder of granulated particles of nickel raw material, cobalt raw material, aluminum raw material and lithium raw material was obtained. This mixed powder was calcined at 740 ° C. for 6 hours under an oxygen flow (climbing temperature rate 5 ° C./min) and then crushed and passed through a sieve having an opening of 45 μm to obtain a positive electrode active material C.

[Positive electrode active material D]
The positive electrode active material D is a positive electrode active material synthesized by the method described below and having a sulfur compound and an antimony compound attached to the surface of the positive electrode active material C. That is, while 96.7 parts by weight of the positive electrode active material C was stirred in a fluidized tank, an aqueous solution of 1.3 parts by weight of lithium sulfate (Li ₂ SO ₄ H ₂ O) was sprayed thereon in a spray form. To the resulting mixture, 2.0 parts by weight of antimony trioxide (Sb ₂ O ₃ , particle median diameter 0.8 μm) was added and mixed well. This mixture was transferred to an alumina container and calcined at 680 ° C. for 2 hours in an air atmosphere to obtain a positive electrode active material D.

[Positive electrode active material E]
The positive electrode active material E is a lithium transition metal composite oxide synthesized by the following method, and is represented by a composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ . Mn ₃ O ₄ as a manganese raw material, NiO as a nickel raw material, and Co (OH) ₂ as a cobalt raw material are weighed so as to have a molar ratio of Mn: Ni: Co = 1: 1: 1, and pure water is added thereto. In addition, the slurry was agitated, and the solid content in the slurry was wet pulverized to a median diameter of 0.2 μm using a circulating medium agitation type wet bead mill while stirring.

  The slurry was spray-dried with a spray dryer to obtain substantially spherical granulated particles having a particle size of about 5 μm, which consisted only of manganese raw material, nickel raw material and cobalt raw material. Add LiOH powder with a median diameter of 3 μm to the resulting granulated particles so that the ratio of the number of moles of Li to the total number of moles of Mn, Ni, and Co is 1.05, and mix with a high-speed mixer. Then, a mixed powder of granulated particles of nickel raw material, cobalt raw material, manganese raw material and lithium raw material was obtained. This mixed powder was calcined at 950 ° C. for 12 hours under an air stream (climbing temperature rate 5 ° C./min), then crushed and passed through a sieve having an opening of 45 μm to obtain a positive electrode active material E.

[Positive electrode active material F]
The positive electrode active material F is a lithium transition metal composite oxide synthesized by the method described below, and is represented by a composition formula Li _1.04 Mn _1.84 Al _0.12 O ₄ . LiOH as a lithium raw material, Mn ₂ O ₃ as a manganese raw material, and AlOOH as an aluminum raw material were weighed so as to have a molar ratio of Li: Mn: Al = 1.04: 1.84: 0.12, respectively. Pure water was added to the slurry to form a slurry, and while stirring, the solid content in the slurry was wet pulverized to a median diameter of 0.5 μm using a circulating medium stirring type wet bead mill.

  The slurry was spray-dried with a spray dryer to obtain substantially spherical granulated particles having a particle diameter of about 10 μm, which were made of a lithium raw material, a manganese raw material, and an aluminum raw material. After the granulated particles were calcined at 900 ° C. for 3 hours under a nitrogen flow (heating rate 5 ° C./min), the flow gas was switched from nitrogen to air, and further calcined at 900 ° C. for 2 hours (temperature falling rate 1 ° C./min). )did. After cooling to room temperature, it was taken out and pulverized, and passed through a sieve having an opening of 45 μm to obtain a positive electrode active material F.

Example 1
<< Preparation of positive electrode >>
A positive electrode was produced using a positive electrode active material in which the positive electrode active material A and the positive electrode active material B were sufficiently mixed at a mass ratio of 1: 1. The mixed positive electrode active material had a BET specific surface area of 1.2 m ² / g, an average primary particle diameter of 0.8 μm, a median diameter d ₅₀ of 6.5 μm, and a tap density of 2.1 g / cm ^3. Met.

90% by mass of the mixed positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder are mixed in an N-methylpyrrolidone solvent. And slurried. The obtained slurry was applied to both sides of an aluminum foil having a thickness of 15 μm, dried, and rolled to a thickness of 70 μm with a press machine. The positive electrode active material layer had a width of 100 mm, a length of 100 mm, and a width of 30 mm. A positive electrode was cut out into a shape having a coating part. The density of the positive electrode active material layer was 2.35 g / cm ³ and (thickness of positive electrode active material layer on one side) / (thickness of current collector) was 1.8.

<Production of negative electrode>
Artificial graphite powder KS-44 (manufactured by Timcal, trade name) 98 parts by weight, 100 parts by weight of an aqueous dispersion of sodium carboxymethylcellulose (concentration 1% by weight of carboxymethylcellulose sodium) as a thickener and binder, and 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber: 50% by mass) was added and mixed with a disperser to form a slurry. The obtained slurry was applied to both sides of a copper foil having a thickness of 10 μm, dried, and rolled to a thickness of 75 μm with a press machine, and the negative electrode active material layer had a width of 104 mm, a length of 104 mm, and a width of 30 mm. It cut out in the shape which has a coating part, and was set as the negative electrode.

<< Preparation of non-aqueous electrolyte >>
Under a dry argon atmosphere, it was sufficiently dried at a concentration of 1 mol / L in a mixed solvent of purified ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 3: 3: 4. Lithium hexafluorophosphate (LiPF ₆ ) was dissolved. Furthermore, hexamethylcyclotrisiloxane was contained so that it might become 0.3 mass%.

<Production of battery>
The 33 positive electrodes and 34 negative electrodes were alternately arranged and laminated so that a separator (thickness 25 μm) of a porous polyethylene sheet was sandwiched between the electrodes. At this time, the positive electrode active material surface was faced so as not to deviate from the negative electrode active material surface. The uncoated portions of each of the positive electrode and the negative electrode were welded together to produce a current collecting tab, and an electrode group was enclosed in a battery can (outside dimension: 120 × 110 × 10 mm). Then, 20 mL of nonaqueous electrolyte solution was inject | poured into the battery can with which the electrode group was loaded, it was made to osmose | permeate electrode enough, and it sealed and produced the battery. The ratio of the total electrode area of the positive electrode to the sum of the outer surface areas of the batteries was 21.3.

<Battery evaluation>
(Battery capacity measurement method)
For a new battery that has not undergone a charge / discharge cycle, a voltage range of 4.2 V to 3.0 V and a current value of 0.2 C at 25 ° C. The initial charge / discharge was performed for 5 cycles at 1C. The discharge capacity at the 5th cycle at this time was defined as the initial capacity. The results of battery evaluation are shown in Table 2.

(Initial output measurement method)
In a 25 ° C. environment, the battery is charged with a constant current of 0.2 C for 150 minutes, discharged at 0.1 C, 0.3 C, 1.0 C, 3.0 C, and 10.0 C, respectively, for 10 seconds. The voltage was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3 V) was defined as output (W). The results of battery evaluation are shown in Table 2.

(Cycle test (measurement method of battery capacity after endurance and output after endurance))
The cycle test was performed in a high temperature environment of 60 ° C., which is regarded as the actual maximum use temperature of the lithium secondary battery. After charging with a constant current constant voltage method of 2C to a charge upper limit voltage of 4.2V, a charge / discharge cycle for discharging with a constant current of 2C to a discharge end voltage of 3.0V was defined as one cycle, and this cycle was repeated up to 500 cycles. The battery after the cycle test was charged and discharged for 3 cycles at a current value of 0.2 C in a 25 ° C. environment, and the 0.2 C discharge capacity at the third cycle was defined as the battery capacity after endurance. Moreover, the output was measured with respect to the battery after the end of the cycle test to obtain the output after durability. The results of battery evaluation are shown in Table 2.

Example 2
The same operation as in Example 1 was performed except that 0.3% by mass of trimethylsilyl methanesulfonate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. The results of battery evaluation are shown in Table 2.

Example 3
The same operation as in Example 1 was performed except that 0.3% by mass of phenyldimethylfluorosilane was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. The results of battery evaluation are shown in Table 2.

Example 4
The same operation as in Example 1 was performed except that 0.3% by mass of lithium difluorophosphate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. The results of battery evaluation are shown in Table 2.

Comparative Example 1
The same operation as in Example 1 was performed except that hexamethylcyclotrisiloxane was not contained in the nonaqueous electrolytic solution. The results of battery evaluation are shown in Table 2.

Example 5
A positive electrode was prepared using a positive electrode active material in which positive electrode active material A and positive electrode active material E were sufficiently mixed at a mass ratio of 1: 1 as a positive electrode active material, and rolled to a thickness of 78 μm with a press machine. This was carried out in the same manner as in Example 1 except that the sheet and 33 negative electrodes were used. (The thickness of the positive electrode active material layer on one side of the positive electrode) / (the thickness of the positive electrode current collector) is 2.1, and the ratio of the total electrode area of the positive electrode to the sum of the outer surface area of the battery is 20.6. there were. The mixed positive electrode active material had a BET specific surface area of 1.2 m ² / g, an average primary particle diameter of 0.8 μm, a median diameter d ₅₀ of 5.7 μm, and a tap density of 2.0 g / cm ^3. Met. Table 3 shows the results of battery evaluation.

Example 6
The same operation as in Example 5 was performed except that 0.3% by mass of trimethylsilyl methanesulfonate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 3 shows the results of battery evaluation.

Example 7
The same operation as in Example 5 was performed except that 0.3% by mass of phenyldimethylfluorosilane was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 3 shows the results of battery evaluation.

Example 8
The same operation as in Example 5 was performed except that 0.3% by mass of lithium difluorophosphate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 3 shows the results of battery evaluation.

Comparative Example 2
The same operation as in Example 5 was performed except that hexamethylcyclotrisiloxane was not contained in the nonaqueous electrolytic solution. Table 3 shows the results of battery evaluation.

Example 9
A positive electrode was prepared using a positive electrode active material in which positive electrode active material A and positive electrode active material F were sufficiently mixed at a mass ratio of 1: 1 as a positive electrode active material, and the positive electrode 30 was rolled to a thickness of 91 μm with a press. This was carried out in the same manner as in Example 1 except that the sheet and 31 negative electrodes were used. (The thickness of the positive electrode active material layer on one side of the positive electrode) / (the thickness of the positive electrode current collector) is 2.5, and the ratio of the total electrode area of the positive electrode to the sum of the exterior surface area of the battery is 19.4. there were. The mixed positive electrode active material had a BET specific surface area of 1.0 m ² / g, an average primary particle diameter of 0.6 μm, a median diameter d ₅₀ of 7.5 μm, and a tap density of 2.2 g / cm ^3. Met. Table 4 shows the results of battery evaluation.

Example 10
The same operation as in Example 9 was performed except that 0.3% by mass of trimethylsilyl methanesulfonate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 4 shows the results of battery evaluation.

Example 11
The same operation as in Example 9 was performed except that 0.3% by mass of phenyldimethylfluorosilane was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 4 shows the results of battery evaluation.

Example 12
The same operation as in Example 9 was performed except that 0.3% by mass of lithium difluorophosphate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 4 shows the results of battery evaluation.

Comparative Example 3
The same operation as in Example 9 was performed except that hexamethylcyclotrisiloxane was not contained in the nonaqueous electrolytic solution. Table 4 shows the results of battery evaluation.

Example 13
A positive electrode was prepared using a positive electrode active material in which positive electrode active material C and positive electrode active material E were sufficiently mixed at a mass ratio of 1: 1 as a positive electrode active material, and rolled to a thickness of 72 μm with a press machine. A battery was fabricated in the same manner as in Example 1 except that the sheet and 34 negative electrodes were used. The mixed positive electrode active material had a BET specific surface area of 0.9 m ² / g, an average primary particle diameter of 0.7 μm, a median diameter d ₅₀ of 6.7 μm, and a tap density of 2.0 g / cm ^3. Met. (Thickness of the positive electrode active material layer on one side of the positive electrode) / (thickness of the positive electrode current collector) is 1.9, and the ratio of the total electrode area of the positive electrode to the sum of the outer surface area of the battery is 21.3. there were. The battery was evaluated in the same manner as in Example 1 except that the voltage range of capacity measurement was 3.0 to 4.1 V and the charge upper limit voltage of the cycle test was 4.1 V. Table 5 shows the results of battery evaluation.

Example 14
The same operation as in Example 13 was performed except that 0.3% by mass of trimethylsilyl methanesulfonate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 5 shows the results of battery evaluation.

Example 15
The same operation as in Example 13 was carried out except that 0.3% by mass of phenyldimethylfluorosilane was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 5 shows the results of battery evaluation.

Example 16
The same operation as in Example 13 was performed except that 0.3% by mass of lithium difluorophosphate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 5 shows the results of battery evaluation.

Comparative Example 4
The same operation as in Example 13 was carried out except that hexamethylcyclotrisiloxane was not contained in the nonaqueous electrolytic solution. Table 5 shows the results of battery evaluation.

Example 17
A positive electrode was prepared using a positive electrode active material in which positive electrode active material C and positive electrode active material F were sufficiently mixed at a mass ratio of 1: 1 as a positive electrode active material, and the positive electrode 32 was rolled to a thickness of 78 μm with a press. This was carried out in the same manner as in Example 1 except that the sheet and 33 negative electrodes were used. (The thickness of the positive electrode active material layer on one side of the positive electrode) / (the thickness of the positive electrode current collector) is 2.1, and the ratio of the total electrode area of the positive electrode to the sum of the outer surface area of the battery is 20.6. there were. The mixed positive electrode active material had a BET specific surface area of 0.8 m ² / g, an average primary particle diameter of 0.6 μm, a median diameter d ₅₀ of 8.5 μm, and a tap density of 2.2 g / cm ^3. Met. Table 6 shows the results of battery evaluation.

Example 18
The same operation as in Example 17 was performed except that 0.3% by mass of trimethylsilyl methanesulfonate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 6 shows the results of battery evaluation.

Example 19
The same operation as in Example 17 was performed except that 0.3% by mass of phenyldimethylfluorosilane was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 6 shows the results of battery evaluation.

Example 20
The same operation as in Example 17 was carried out except that 0.3% by mass of lithium difluorophosphate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 6 shows the results of battery evaluation.

Comparative Example 5
The same operation as in Example 17 was performed except that hexamethylcyclotrisiloxane was not contained in the nonaqueous electrolytic solution. Table 6 shows the results of battery evaluation.

Example 21
A positive electrode is produced using a positive electrode active material in which a positive electrode active material D and a positive electrode active material E are sufficiently mixed at a mass ratio of 1: 1 as a positive electrode active material, and rolled to a thickness of 72 μm with a press machine. A battery was fabricated in the same manner as in Example 1 except that the sheet and 34 negative electrodes were used. The mixed positive electrode active material had a BET specific surface area of 0.9 m ² / g, an average primary particle diameter of 0.7 μm, a median diameter d ₅₀ of 6.7 μm, and a tap density of 2.0 g / cm ^3. Met. (Thickness of the positive electrode active material layer on one side of the positive electrode) / (thickness of the positive electrode current collector) is 1.9, and the ratio of the total electrode area of the positive electrode to the sum of the outer surface area of the battery is 21.3. there were. The battery was evaluated in the same manner as in Example 1 except that the voltage range of the capacity measurement was 3.0 to 4.1 V and the upper limit voltage of the cycle test was 4.1 V. Table 7 shows the results of battery evaluation.

Example 22
The same operation as in Example 17 was performed except that 0.3% by mass of trimethylsilyl methanesulfonate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 7 shows the results of battery evaluation.

Example 23
The same operation as in Example 17 was performed except that 0.3% by mass of phenyldimethylfluorosilane was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 7 shows the results of battery evaluation.

Example 24
The same operation as in Example 17 was carried out except that 0.3% by mass of lithium difluorophosphate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 7 shows the results of battery evaluation.

Comparative Example 6
The same operation as in Example 17 was performed except that hexamethylcyclotrisiloxane was not contained in the nonaqueous electrolytic solution. Table 7 shows the results of battery evaluation.

Example 25
A positive electrode was prepared using a positive electrode active material in which a positive electrode active material E and a positive electrode active material F were sufficiently mixed at a mass ratio of 1: 1 as a positive electrode active material, and the positive electrode 31 was rolled to a thickness of 86 μm with a press. This was carried out in the same manner as in Example 1 except that 32 sheets and 32 negative electrodes were used. (Thickness of the positive electrode active material layer on one side of the positive electrode) / (thickness of the positive electrode current collector) is 2.4, and the ratio of the total electrode area of the positive electrode to the sum of the outer surface area of the battery is 20.0. there were. The mixed positive electrode active material had a BET specific surface area of 1.1 m ² / g, an average primary particle diameter of 0.6 μm, a median diameter d ₅₀ of 6.2 μm, and a tap density of 2.0 g / cm ^3. Met. Table 8 shows the results of battery evaluation.

Example 26
The same operation as in Example 17 was performed except that 0.3% by mass of trimethylsilyl methanesulfonate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 8 shows the results of battery evaluation.

Example 27
The same operation as in Example 17 was performed except that 0.3% by mass of phenyldimethylfluorosilane was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 8 shows the results of battery evaluation.

Example 28
The same operation as in Example 17 was carried out except that 0.3% by mass of lithium difluorophosphate was contained in the nonaqueous electrolytic solution instead of hexamethylcyclotrisiloxane. Table 8 shows the results of battery evaluation.

Comparative Example 7
The same operation as in Example 17 was performed except that hexamethylcyclotrisiloxane was not contained in the nonaqueous electrolytic solution. Table 8 shows the results of battery evaluation.

  From the results shown in Tables 2 to 8, in any positive electrode, the output and capacity retention rate are improved by the inclusion of the specific compound in the non-aqueous electrolyte, and the battery capacity and output are sufficiently maintained even after the cycle test. I found out.

  The use of the lithium secondary battery of the present invention is not particularly limited, and can be used for various known uses. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Widely used in electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorbikes, bicycles, lighting equipment, toys, game equipment, watches, power tools, strobes, cameras, etc. It is what is done.

Claims (10)

A lithium secondary battery comprising at least a positive electrode and a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte solution containing a lithium salt in a non-aqueous solvent, wherein the non-aqueous electrolyte solution has the general formula ( 1) a cyclic siloxane compound represented by formula (2), a fluorosilane compound represented by formula (2), a compound represented by formula (3), a compound having an SF bond in the molecule, a nitrate, a nitrite, A non-aqueous electrolyte solution containing at least 10 ppm of at least one compound selected from the group consisting of monofluorophosphate, difluorophosphate, acetate and propionate in the entire non-aqueous electrolyte, The lithium secondary battery, wherein the positive electrode is a positive electrode containing two or more types of positive electrode active materials having different compositions.

[In General Formula (1), R ¹ and R ² represent the same or different organic group having 1 to 12 carbon atoms, and n represents an integer of 3 to 10. ]

[In General Formula (2), R ^{3 to} R ⁵ represent an organic group having 1 to 12 carbon atoms which may be the same or different from each other, x represents an integer of 1 to 3, p, q and Each r represents an integer of 0 to 3, and 1 ≦ p + q + r ≦ 3. ]

[In General Formula (3), R ^{6 to} R ⁸ represent an organic group having 1 to 12 carbon atoms which may be the same as or different from each other, and A represents H, C, N, O, F, S, Represents a group composed of Si and / or P; ]   The non-aqueous electrolyte includes a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), and an SF bond in the molecule. At least one compound selected from the group consisting of a compound having a salt, nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate, 0.01% by mass or more and 5% by mass 2. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a non-aqueous electrolyte solution containing at most%. The lithium secondary battery according to claim 1 or ² , wherein a BET specific surface area of at least one positive electrode active material of the positive electrode active material contained in the positive electrode is 0.4 m ² / g or more and 2 m ² / g or less. .   4. The lithium secondary material according to claim 1, wherein an average primary particle size of at least one positive electrode active material of the positive electrode active material contained in the positive electrode is 0.1 μm or more and 2 μm or less. 5. battery. 5. The lithium secondary battery according to claim 1, wherein a median diameter d ₅₀ of at least one positive electrode active material of the positive electrode active material contained in the positive electrode is 1 μm or more and 20 μm or less. The tap density of at least one positive electrode active material of the positive electrode active material contained in the positive electrode is 1.3 g / cm ³ or more and 2.7 g / cm ³ or less. The lithium secondary battery as described in.   The at least one positive electrode active material of the positive electrode active material contained in the positive electrode is obtained by adhering a substance having a composition different from that of the substance constituting the main body of the positive electrode active material to the surface thereof. The lithium secondary battery according to claim 1.   The positive electrode is a positive electrode in which a positive electrode active material layer containing a positive electrode active material and a binder is formed on a current collector, and the content of the positive electrode active material in the positive electrode active material layer is 80 The lithium secondary battery according to any one of claims 1 to 7, wherein the lithium secondary battery has a range of not less than mass% and not more than 95 mass%. The positive electrode is a positive electrode formed by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector, and the density of the positive electrode active material layer is 1.5 g / cm ³ or more. The lithium secondary battery according to any one of claims 1 to 8, wherein the lithium secondary battery has a range of 3.5 g / cm ³ or less.   The positive electrode is a positive electrode in which a positive electrode active material layer containing a positive electrode active material and a binder is formed on a current collector, wherein a ratio of the thickness of the positive electrode active material layer and the current collector, The thickness of the active material layer on one side immediately before the nonaqueous electrolyte solution injection / (thickness of the current collector) is in the range of 0.5 or more and 20 or less. The lithium secondary battery according to claim.