JP2019117811A - Nonaqueous electrolyte solution for secondary battery and nonaqueous electrolyte secondary battery using the same - Google Patents

Abstract

To provide a nonaqueous electrolyte solution for a secondary battery and a nonaqueous electrolyte secondary battery which enable the large enhancement of low-temperature characteristics.SOLUTION: The above problem is solved by a nonaqueous electrolyte solution for a secondary battery, comprising: a nonaqueous solvent; and a lithium salt. The nonaqueous solvent is a mixed solvent containing at least ethylene carbonate and a chain carbonate. The proportion of the ethylene carbonate to a total amount of the nonaqueous solvent is 1 vol.% or more and 25 vol.% or less. Of the nonaqueous solvent, the total percentage of the ethylene carbonate and chain carbonate which account for is 80 vol.% or more. The electrolyte solution further comprises a compound having a S-F bond in its molecule, which is a sulfonyl fluoride or fluorosulfonate and which is included at a total amount of 10 ppm or more and 5 mass% or less in the whole nonaqueous electrolyte solution. The compound may be otherwise added to the electrolyte solution.SELECTED DRAWING: None

Description

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

  In recent years, with the miniaturization of electronic devices, the demand for higher capacity for secondary batteries is increasing, and lithium secondary batteries having higher energy density than nickel-cadmium batteries and nickel-hydrogen batteries are attracting attention. There is.

Examples of electrolytes for lithium secondary batteries include electrolytes such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO _{3, and the} like. Cyclic carbonates such as ethylene carbonate and propylene carbonate, linear carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, cyclic esters such as γ-butyrolactone and γ-valerolactone, linear esters such as methyl acetate and methyl propionate , Non-aqueous solvents such as cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and tetrahydropyran, chain ethers such as dimethoxyethane and dimethoxymethane, and sulfur-containing organic solvents such as sulfolane and diethyl sulfone. Water-based electrolyte solution It is needed.

  In the secondary battery using such a lithium non-aqueous electrolyte, the reactivity and the ion conductivity are different depending on the composition of the non-aqueous electrolyte, so the battery characteristics are largely changed by the non-aqueous electrolyte. Further, as a characteristic of the battery, there is a problem that the internal resistance becomes high in a low temperature environment, and the discharge capacity in the case of discharging at a constant discharge rate (hereinafter abbreviated as "rate") decreases.

  As lithium secondary batteries are used in various electronic devices, as well as in automobiles and power tools, there has been a demand for an electrolyte which does not significantly reduce the performance even in a low temperature environment. For example, in Patent Document 1, 2-methyltetrahydrofuran, 1,2-dimethoxyethane, 4-methyl 1,3-dioxolane or the like is mixed with a mixed solvent of ethylene carbonate and diethyl carbonate to improve low-temperature characteristics. Proposed. However, in these methods, when using batteries in severe cold regions such as -20 ° C and -30 ° C, sufficient characteristics can not be obtained.

  Further, Patent Document 2 uses a non-aqueous electrolyte containing cyclic siloxane and / or a reaction product thereof, and Patent Document 3 uses a non-aqueous electrolyte containing a silicon compound having a specific structure. Are both described as being able to improve input / output characteristics and cycle characteristics. These methods are effective but certainly not sufficient.

Japanese Patent Application Laid-Open No. 3-55570 JP 2004-71458 A JP 2004-87459 A

  The present invention has been made in view of the background art, and an object thereof is to provide a non-aqueous electrolytic solution and a non-aqueous electrolytic solution secondary battery for a secondary battery, which significantly improve low-temperature characteristics.

  As a result of intensive studies conducted in view of the above problems, the present inventor uses a mixed solvent containing ethylene carbonate as a non-aqueous solvent for a non-aqueous electrolytic solution, and the proportion of ethylene carbonate in the mixed solvent is 1% by volume or more and 25 vol. The present inventors have found that the present invention can be achieved by synergistically achieving very good low temperature properties by containing a specific chemical substance at the same time, while making it less than 10%.

［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, according to the present invention, in the non-aqueous electrolyte for a secondary battery comprising a non-aqueous solvent and a lithium salt, the non-aqueous solvent is a mixed solvent containing at least ethylene carbonate, and ethylene relative to the total non-aqueous solvent. The cyclic siloxane compound represented by the general formula (1), the fluorosilane compound represented by the general formula (2), and the general formula (3), wherein the proportion of the carbonate is 1% by volume or more and 25% by volume or less And at least one selected from the group consisting of compounds having S-F bond in the molecule, nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates and propionates. The present invention resides in a non-aqueous electrolyte for a secondary battery characterized by containing 10 ppm or more of the above-mentioned compound in the whole non-aqueous electrolyte or added thereto.

[In the general formula (1), ^{R 1} and ^{R 2} represent identical there may be different even if an organic group having 1 to 12 carbon atoms with each other, n represents an integer of 3 to 10. ]

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

[In the general formula (3), R ^{6 to} R ⁸ each independently represent the same or different organic group having 1 to 12 carbon atoms, and A represents H, C, N, O, F, S, Represents a group composed of Si and / or P. ]

  The present invention is also a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte solution, a negative electrode capable of absorbing and desorbing lithium ions, and a positive electrode, wherein the non-aqueous electrolyte solution is the non-aqueous electrolyte for the above-mentioned secondary battery. It resides in a non-aqueous electrolyte secondary battery characterized in that it is a solution.

The present invention is also a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte solution, a negative electrode capable of absorbing and desorbing lithium ions, and a positive electrode, wherein the non-aqueous electrolyte solution is the non-aqueous electrolyte for the above-mentioned secondary battery. A non-aqueous electrolytic solution secondary battery, which is a liquid and has the following properties (1), (2) and / or (3).
(1) The sum of the electrode area of the positive electrode and the surface area of the exterior of the secondary battery is 20 times or more in area ratio.
(2) The DC resistance component of the secondary battery is 10 milliohms (mΩ) or less.
(3) The electric capacity of the battery element housed in one battery outer case of the secondary battery is 3 amperes-hour (Ah) or more.

  According to the present invention, it is possible to largely improve the low temperature characteristics of the non-aqueous electrolyte secondary battery, more specifically, to improve the low temperature characteristics without deteriorating the cycle characteristics and the storage characteristics.

  Hereinafter, the embodiment of the present invention will be described in detail, but the description of the configuration requirements described below is an example (representative example) of the embodiment of the present invention, and the contents thereof are not specified. Various modifications may be made within the scope of the present invention.

<Nonaqueous Electrolyte for Lithium Secondary Battery>
The non-aqueous electrolyte solution for a secondary battery of the present invention contains an electrolyte and a non-aqueous solvent which dissolves the same, as the non-aqueous electrolyte solution in common use.

[Lithium salt]
In the present invention, as the electrolyte, a lithium salt which is known to be usable as an electrolyte of a non-aqueous electrolyte solution for lithium secondary batteries is suitably used, and although there is no particular limitation, for example, the following can be mentioned.

Inorganic lithium salt:
Inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ and LiSbF ₆ ; perhalogenates such as LiClO ₄ , LiBrO ₄ and LiIO ₄ ; inorganic chloride salts such as LiAlCl _{4 and the} like.
Fluorine-containing organic lithium salt:
Perfluoroalkanesulfonic acid salts 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 SO ₂ ), etc. Perfluoroalkanesulfonylimide salts; Perfluoroalkanesulfonyl methide 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 Fluoroalkyl fluorophosphates such as Li [PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ], and the like.
Oxalato borate salt:
Lithium bis (oxalato) borate, lithium difluoro oxalato borate and the like.

One of these may be used alone, or two or more of these may be used in any combination and ratio. Among these, LiPF ₆ is preferable in comprehensively judging solubility in a non-aqueous solvent, charge / discharge characteristics in the case of using a secondary battery, output characteristics, cycle characteristics and the like.

  The concentration of the lithium salt in the non-aqueous electrolyte solution is not particularly limited, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, and more preferably 0.7 mol / L or more. The upper limit is usually 2 mol / L or less, preferably 1.8 mol / L or less, more preferably 1.7 mol / L or less. If the concentration is too low, the conductivity of the electrolyte may be insufficient. If the concentration is too high, the conductivity may decrease due to the increase in viscosity, and the performance of the lithium secondary battery is degraded. May.

A preferred example in the case of using two or more in combination is a combination of LiPF ₆ and LiBF _{4. In} this case, the proportion 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.

  Another example is the combined use of an inorganic fluoride salt and a perfluoroalkanesulfonic acid imide 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 is preferable, and 80% by mass or more and 98% by mass or less are more preferable. The combined use of the two has the effect of suppressing deterioration due to high temperature storage.

[Non-aqueous solvent]
The non-aqueous solvent of the present invention is a mixed solvent containing ethylene carbonate as an essential component, but it may be appropriately selected from non-aqueous solvents other than ethylene carbonate, which have conventionally been proposed as solvents for non-aqueous electrolytes. Can be used. As such, for example, the following may be mentioned.
1) Cyclic carbonates other than ethylene carbonate Ethylene carbonates are cyclic carbonates, but in the present invention, other cyclic carbonates can be added. When other cyclic carbonates are used, the carbon number of the alkylene group constituting these other cyclic carbonates is preferably 3 to 6, particularly preferably 3 to 4. Among them, propylene carbonate, butylene carbonate and the like are preferable, and propylene carbonate is particularly preferable.
2) Chain-like carbonate As a chain-like carbonate, a dialkyl carbonate is preferable, As for carbon number of the alkyl group to comprise, 1-5 are respectively preferable, Especially preferably, it is 1-4. Specific examples thereof 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. Among them, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferable.
3) Cyclic ester Specifically, for example, γ-butyrolactone, γ-valerolactone and the like can be mentioned.
4) Chain-like ester Specifically, methyl acetate, ethyl acetate, propyl acetate, methyl propionate etc. are mentioned, for example.
5) Cyclic Ether Specifically, for example, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and the like can be mentioned.
6) Chain Ether Specifically, for example, dimethoxyethane, dimethoxymethane and the like can be mentioned.
7) Sulfur-Containing Organic Solvent Specifically, for example, sulfolane, diethylsulfone and the like can be mentioned.

  As these non-aqueous solvents, one type may be used other than ethylene carbonate, or two or more types may be used in combination. For example, it is preferable to use a low viscosity solvent such as chain carbonates or chain esters in combination from the viewpoint of charge and discharge characteristics at a high current value.

  One preferred combination of non-aqueous solvents is a combination based on ethylene carbonate and linear carbonates. Among them, it is preferable that the total of ethylene carbonates and chain carbonates in the non-aqueous solvent is 80% by volume or more, preferably 85% by volume or more, and more preferably 90% by volume or more.

  In this mixed solvent, a lithium salt, 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), S in the molecule A non-aqueous electrolytic solution containing at least one selected from the group consisting of a compound having a —F bond, a nitrate, a nitrite, a monofluorophosphate, a difluorophosphate, an acetate and a propionate, It is preferable because the low temperature characteristics of the battery manufactured using the battery are good, and the balance between the cycle characteristics and the high temperature storage characteristics (in particular, the remaining capacity after high temperature storage and the high load discharge capacity) and the gas generation suppression are improved.

  Specific examples of preferable combinations of ethylene carbonates and chain carbonates include 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, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc. may be mentioned.

  A combination in which propylene carbonate is further added to the combination of ethylene carbonate and linear carbonates is also mentioned as a preferable combination. When containing propylene carbonate, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50. Furthermore, the amount of propylene carbonate in the entire nonaqueous solvent is usually 0.1% by volume or more, preferably 1% by volume or more, more preferably 2% by volume or more, and usually 10% by volume or less, preferably 8% by volume or less More preferably, the content is 5% by volume or less, because the low-temperature properties are further excellent while maintaining the properties of the combination of ethylene carbonate and linear carbonates.

  Among these, those containing asymmetric linear carbonates are more preferable, and in particular, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate and diethyl carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate and ethyl Those containing ethylene carbonate, symmetrical linear carbonates and asymmetric linear carbonates, such as methyl carbonate, are preferable because both cycle characteristics and low-temperature output characteristics are good. From the viewpoint of the viscosity as the electrolytic solution and the electrical conductivity, the carbon number of the alkyl group constituting the dialkyl carbonate is preferably small, and 1 to 2 is particularly preferable. Specifically, it is preferable that the asymmetric linear carbonates be ethyl methyl carbonate in that the low temperature output improvement effect when using a specific compound is increased in addition to the small viscosity.

  Another example of a preferred mixed solvent is one containing a linear ester. In particular, one containing a chain ester in the mixed solvent of cyclic carbonates and chain carbonates is preferable from the viewpoint of improving the low temperature characteristics of the battery, and methyl acetate and ethyl acetate are particularly preferable as the chain ester. preferable. The volume of the linear ester in the non-aqueous solvent is usually 5% or more, preferably 8% or more, more preferably 15% or more, and usually 50% or less, preferably 35% or less, more preferably 30% or less, More preferably, it is 25% or less.

  In the present invention, the proportion of ethylene carbonate in the entire mixed solvent is 1% by volume or more, preferably 3% by volume or more, more preferably 5% by volume or more, and more preferably 10% by volume or more. The upper limit is 25% by volume or less, preferably 20% by volume or less, and more preferably 15% by volume or less. Below the lower limit, the repeated charge / discharge (cycle) characteristics of the battery and the high temperature storage characteristics may be deteriorated, and furthermore, the electric conductivity may be deteriorated to cause deterioration of the output characteristics. If the upper limit is exceeded, the effect of improving the low temperature properties obtained when mixed with the specific compound of the present invention may be reduced. In addition, the non-aqueous electrolyte solution of the present invention is a low-resistance secondary battery having a DC resistance component of 10 milliohms (mΩ) or less, or a relatively large secondary battery with a rated discharge capacity of 3 amps-hour (Ah) or more and less than 20 Ah. It is particularly preferable to use for a battery, and can exhibit a large low temperature output.

[Specific compound]
The non-aqueous electrolytic solution 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 At least one compound selected from the group consisting of compounds having -F bond, nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates and propionates (these compounds are referred to as "specific compounds" and And the like, which may be abbreviated.

[[Cyclic siloxane compound represented by Formula (1)]]
R ¹ and R ² in the cyclic siloxane compound represented by the general formula (1) are organic groups having 1 to 12 carbon atoms which may be the same as or different from each other, and as R ¹ and R ² , Linear alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, sec-butyl and t-butyl; cyclic alkyl such as cyclohexyl and norbornanyl; vinyl Alkenyl groups such as 1-propenyl group, allyl group, butenyl group and 1,3-butadienyl group; alkynyl groups such as ethynyl group, propynyl group and 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 which may have an alkyl substituent; a phenylmethyl group; Examples include aralkyl groups such as phenethyl 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. The alkenyl group is preferable because it acts on the electrolytic solution and the film on the surface of the electrode to improve input / output characteristics, and the aryl group has a function to capture radicals generated in the battery during charge and discharge to improve overall battery performance. . Therefore, as R ¹ and R ² , a methyl group, a vinyl group or a phenyl group is particularly preferable.

  In general formula (1), although n represents the integer of 3-10, the integer of 3-6 is preferable and 3 or 4 is especially 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. Among these, cyclotrisiloxane is particularly preferable.

[[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, and R in the general formula (1) ^The linear alkyl group, the cyclic alkyl group, the alkenyl group, the alkynyl group, the halogenated alkyl group, the alkyl group having a saturated heterocyclic group, the phenyl group which may have an alkyl group, etc. mentioned as examples of ¹ and R ² In addition to aryl groups, aralkyl groups, trialkylsilyl groups and trialkylsiloxy groups, and carbonyl groups such as ethoxycarbonylethyl group; carboxyl groups such as acetoxy group, acetoxymethyl group and trifluoroacetoxy group; methoxy group, ethoxy group, Oxy groups such as propoxy group, butoxy group, phenoxy group and allyloxy group; amino groups 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 represent an integer of 0 to 3, and 1 ≦ p + q + r ≦ 3.

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

  Since the fluorosilane compound represented by General formula (2) will volatilize if a boiling point is low, it may become difficult to make the electrolytic solution contain a predetermined amount. Further, even after being contained in the electrolytic solution, there is a possibility that the heat generation of the battery due to charge and discharge and the volatilization may be performed under such conditions that the external environment becomes high temperature. Therefore, one having a boiling point of 50 ° C. or more at 1 atmospheric pressure is preferable, and one having a boiling point of 60 ° C. or more is 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 film of the electrolytic solution or the electrode surface. The aryl group has an effect of capturing radicals generated in the battery at the time of charge and discharge to improve the overall battery performance by improving the input / output characteristics. Therefore, from this viewpoint, as the organic group, a methyl group, a vinyl group or a phenyl group is preferable, and as an example of the compound, trimethylfluorosilane, vinyldimethylfluorosilane, phenyldimethylfluorosilane, vinyldiphenylfluorosilane, etc. are particularly preferable. .

[[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, and examples thereof include It may have an alkyl group having an alkyl group having a chain alkyl group, a cyclic alkyl group, an alkenyl group, an alkynyl group, a halogenated alkyl group, a saturated heterocyclic group, and an alkyl group mentioned as examples of R ^{3 to} R ⁵ in Likewise, aryl groups such as phenyl group, aralkyl groups, trialkylsilyl groups, trialkylsiloxy groups, carbonyl groups, carboxyl groups, oxy groups, amino groups, benzyl groups and the like can be mentioned.

  A in the compound represented by the general formula (3) is not particularly limited as long as it is a group composed of H, C, N, O, F, S, Si and / or P, but the general formula (3) As the element directly bonded to the oxygen atom in the inside, C, S, Si or P is preferable. Examples of the form of these atoms include, for example, chain alkyl groups, cyclic alkyl groups, alkenyl groups, alkynyl groups, halogenated alkyl groups, carbonyl groups, sulfonyl groups, trialkylsilyl groups, phosphoryl groups, phosphinyl groups and the like. Is preferred. In addition, 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, octamethyltrisiloxane and the like; 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, and 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.

  Among these, siloxane compounds, sulfonic acid esters and sulfuric acid esters are preferable, and sulfonic acid esters are particularly preferable. As siloxane compounds, hexamethyldisiloxane is preferable, as sulfonic acid esters, trimethylsilyl methanesulfonate is preferable, and as sulfuric acid esters, bis (trimethylsilyl) sulfate is preferable.

[[Compound having S-F 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 preferable. 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, 3-hexafluoropropane-1,3-bis (sulfonyl fluoride), methyl fluorosulfonate, ethyl fluorosulfonate and the like. Among them, methanesulfonyl fluoride, methane bis (sulfonyl fluoride) or methyl fluorosulfonate is preferable.

[[Nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, propionate]]
There are no particular limitations on the counter cation of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate, but metal elements such as Li, Na, K, Mg, Ca, Fe, and Cu And ammonium represented by NR ⁹ R ¹⁰ R ¹¹ R ¹² (wherein, R ^{9 to} R ¹² each independently represent a hydrogen atom or an organic group having 1 to 12 carbon atoms), quaternary ammonium Can be 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 by a halogen atom, a cycloalkyl group which may be substituted by a halogen atom, or a halogen atom. And aryl groups, nitrogen atom-containing heterocyclic groups, and the like. As R ^{9 to} R ¹² , a hydrogen atom, an alkyl group, a cycloalkyl group, a nitrogen atom-containing heterocyclic group and the like are preferable. 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.

  Further, among them, nitrate or difluorophosphate is preferable in view of the output characteristic improvement rate and cycle characteristics, and lithium difluorophosphate is particularly preferable. Moreover, as these compounds, those synthesized in a non-aqueous solvent may be used substantially as they are, and those separately synthesized and substantially isolated may be used in a non-aqueous solvent or in a non-aqueous electrolytic solution May be added to

  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 Compounds, nitrates, nitrites, monofluorophosphates, difluorophosphates, acetates or propionates may be used alone or in any combination and ratio of two or more compounds. You may In addition, among the compounds classified as the specific compounds, one kind may be used alone, or two or more kinds of compounds may be used in combination in an optional combination and ratio.

  The proportion of these specific compounds in the non-aqueous electrolyte is essentially 10 ppm or more (0.001 mass% or more) in total with respect to all the non-aqueous electrolytes, but preferably 0.01 mass% or more, more preferably 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. When the concentration of the specific compound is too low, the improvement effect of the low temperature characteristics may be difficult to obtain, while when the concentration is too high, the charge and discharge efficiency may be lowered.

  In addition, when the specific compounds are actually used as a non-aqueous electrolyte solution for the preparation of a secondary battery, even if the battery is disassembled and the non-aqueous electrolyte solution is taken out again, the content therein is significantly reduced. There are many. Those which can detect at least 10 ppm of the specific compound from the non-aqueous electrolytic solution withdrawn from the battery are considered to be included in the present invention.

  In preparation of the non-aqueous electrolytic solution, 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.

  Although it is not clear that the low temperature discharge characteristics are greatly improved by using the nonaqueous solvent containing a specific proportion of ethylene carbonate and these specific compounds in combination, the specific compound may have a certain degree of low temperature discharge characteristic improvement effect. is there. It is thought that it has some effect on the electrode and also because it interacts with lithium ions in the non-aqueous electrolyte, but it is widely used as a solvent for non-aqueous electrolytes for lithium secondary batteries Ethylene carbonate appears to have the effect of inhibiting this action. Ethylene carbonate is likely to coordinate (solvate) to lithium ions, thereby interfering with the interaction (and deintercalation) of the lithium ion and the specific compound (and the positive electrode) and reducing the effect of improving the low temperature discharge characteristics. it is conceivable that.

  On the other hand, ethylene carbonate is useful for securing the solubility of the lithium salt which is the electrolyte and for enhancing the electrical conductivity of the non-aqueous electrolyte. The present invention is the result achieved by finding out means for minimizing the inhibition of the low temperature characteristic improvement effect while securing the conductivity as a result of earnestly examining considering both these characteristics and using it particularly at low temperature Industrial value is great as a non-aqueous electrolytic solution to be supplied to a battery.

[Other compounds]
The non-aqueous electrolytic solution of the present invention contains a lithium salt as an electrolyte and a specific compound as an essential component in a non-aqueous solvent containing ethylene carbonate, but other compounds may impair the effect of the present invention as necessary. It can be contained in any amount as long as it does not exist.

  As such other compounds, for example, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated form of terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran and the like; -Partially fluorinated compounds of the above aromatic compounds such as fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene and the like; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5 Overcharge inhibitors such as fluorine-containing anisole compounds such as difluoroanisole; vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, trifluoropropylene carbonate, succinic anhydride, glutar anhydride Negative electrode film forming agents such as maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic acid anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, propane sultone, butane sultone, methyl methanesulfonate, busulfan, Positive electrodes such as methyl toluene sulfonate, dimethyl sulfate, ethylene glycol, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, thioanisole, diphenyl disulfide, dipyridinium disulfide, etc. Protective agents and the like can be mentioned.

  As the overcharge inhibiting agent, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, a partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran and the like are preferable. Two or more of these may be used in combination. When two or more kinds are used in combination, it is particularly preferable to use cyclohexylbenzene or terphenyl (or a partially hydrogenated product thereof) in combination 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 two or more types are used in combination, it is particularly preferable to use vinylene carbonate in combination with vinyl ethylene carbonate, fluoroethylene carbonate, succinic anhydride and maleic anhydride.

  As a 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, combined use with a negative electrode film formation agent and a positive electrode protective agent, and combined use with an overcharge prevention agent, a negative electrode film formation agent, and a positive electrode protection agent are especially preferable.

  The content of these other compounds in the non-aqueous electrolyte is not particularly limited, but is preferably 0.01% by mass or more, particularly preferably 0.1% by mass or more, based on the whole non-aqueous electrolyte. 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 battery rupture and ignition at the time of abnormality due to overcharge, and to improve capacity retention characteristics and cycle characteristics after high temperature storage.

  There is no particular limitation on the method of preparing the non-aqueous electrolyte solution for secondary battery of the present invention, and lithium salt, specific compound and other compound as needed are dissolved in non-aqueous solvent containing ethylene carbonate according to a conventional method. It can be prepared by

<Non-aqueous electrolyte secondary battery>
Hereinafter, the non-aqueous electrolyte secondary battery of the present invention will be described in detail.
[Battery shape]
The battery shape is not particularly limited, and examples thereof include a bottomed cylindrical shape, a bottomed rectangular shape, a thin shape, a sheet shape, and a paper shape. When incorporated into a system or equipment, in order to enhance the volumetric efficiency and to improve storability, it may be a horseshoe-shaped, comb-shaped, or other type taking into account the fit to the peripheral system placed around the battery . From the viewpoint of efficiently releasing the heat inside the battery to the outside, a rectangular shape having at least one relatively flat, large area surface is preferable.

  In the bottomed cylindrical battery, the external surface area to the charged power generating element is small, so it is preferable to design to efficiently escape the Joule heat generated due to the internal resistance at the time of charge and discharge. Moreover, it is preferable to design so that the filling ratio of the substance with high thermal conductivity may be increased and the temperature distribution in the inside may be reduced.

In the bottomed rectangular shape, the ratio of the area T of the largest surface (the product of the width and height of the external dimension excluding the terminal portion, unit cm ² ) and the thickness T (unit cm) of the battery outline The value of 2S / T is preferably 100 or more, and more preferably 200 or more. By enlarging the maximum surface, characteristics such as cycle performance and high temperature storage can be improved even with a high output and large capacity battery, and the heat release efficiency at abnormal heat generation can be improved, and "valve operation" described later It is possible to suppress the danger of "bursting".

[Battery configuration]
The chargeable / dischargeable secondary battery of the present invention comprises a positive electrode and a negative electrode capable of absorbing and desorbing lithium ions, the above non-aqueous electrolyte solution of the present invention, a separator disposed between the positive electrode and the negative electrode, a current collector terminal, and an exterior It is at least configured by a case or the like. If necessary, a protective element may be mounted inside the battery and / or outside the battery.

[Positive electrode]
The positive electrode used for the non-aqueous electrolyte secondary battery of the present invention will be described below.
[[Positive electrode active material]]
The positive electrode active material used for the positive electrode will be described below.

[[[composition]]]
The positive electrode active material is not particularly limited as long as it can electrochemically store and release lithium ions. Substances containing lithium and at least one transition metal are preferred, and examples thereof include lithium transition metal complex oxides and lithium-containing transition metal phosphate compounds.

As a transition metal of the lithium transition metal complex oxide, V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. are preferable. As a specific example, lithium cobalt complex oxide such as LiCoO ₂ , LiNiO ₂ etc. Lithium / manganese complex oxides such as lithium / nickel complex oxides, LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ MnO _3, etc., and part of transition metal atoms that become main components of these lithium transition metal complex oxides And those substituted with other metals such as V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, and the like. Specific examples of those substituted, for _{example, LiNi 0.5 Mn 0.5 O 2,} LiNi 0.85 Co 0.10 Al 0.05 O 2, LiNi 0.33 Co 0.33 Mn 0.33 O 2, LiMn 1.8 Al 0.2 O 4, LiMn 1.5 Ni 0.5 O 4 , etc. Can be mentioned.

As a transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and as a specific example, 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 a part of transition metal atoms which become main components of these lithium transition metal phosphate compounds Al, Ti, V, Cr, Mn And those substituted with other metals such as Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb and Si.

[[[Surface coating]]]
Further, it is also possible to use a material in which a substance having a composition different from the substance constituting the main positive electrode active material adheres to the surface of the positive electrode active material. As surface adhesion substances, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate.

  These surface adhesion substances are, for example, dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and dried, or the surface adhesion substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and heated. It can be made to adhere on the surface of a positive electrode active material by the method of making it react, etc., the method of adding to a positive electrode active material precursor, and baking simultaneously.

  The amount of the surface adhering substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and preferably 20% or less as an upper limit, more preferably 10 parts by mass or less based on the positive electrode active substance. % Or less, more preferably 5% or less. The surface adhesion substance can suppress the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material, and the battery life can be improved. However, when the adhesion amount is too small, the effect is not sufficiently expressed. If it is too high, the resistance may increase to inhibit the lithium ion ingress and egress.

[[[shape]]]
As the shape of the positive electrode active material particles in the present invention, a block, polyhedron, sphere, oval sphere, plate, needle, column, etc., which are conventionally used, are used. It is preferable that the secondary particles be in the form of particles, and the shape of the secondary particles is spherical or elliptical. Usually, since the active material in the electrode expands and contracts with the charge and discharge of the electrochemical element, the active material is likely to be broken due to the stress or deterioration such as breakage of the conductive path. Therefore, it is preferable that primary particles are aggregated and secondary particles are formed rather than a single particle active material consisting of only primary particles, because stress of expansion and contraction is alleviated and deterioration is prevented. In addition, since spherical or elliptic spherical particles have less orientation at the time of molding of the electrode than plate-like equiaxially oriented particles, expansion and contraction of the electrode at the time of charge and discharge are also small, and the electrode is prepared Even in the mixing with the conductive agent at the time, it is preferable because it is easily mixed uniformly.

[[[[Tap Density]]]]
The tap density of the positive electrode active material is usually 1.3 g / cm ³ or more, preferably 1.5 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, and most preferably 1.7 g / cm ³ or more . When the tap density of the positive electrode active material is below the above lower limit, the necessary amount of dispersion medium is increased at the time of forming the positive electrode active material layer, and the required amount of the conductive material and the binder is increased. The filling rate of the substance may be limited and the battery capacity may be limited. By using a composite oxide powder with a high tap density, a high density positive electrode active material layer can be formed. Generally, the tap density is preferably as high as possible and there is no particular upper limit, but if it is too large, diffusion of lithium ions in the positive electrode active material layer through the electrolyte may be limited and load characteristics may tend to be degraded. It is 2.5 g / cm ³ or less, preferably 2.4 g / cm ³ or less.

In the present invention, the tap density is passed through a sieve with an opening of 300 μm and the sample is dropped to a 20 cm ³ tapping cell to fill the cell volume, and then a powder density measuring instrument (for example, Tap Denser manufactured by Seishin Enterprise Co., Ltd.) The tapping is performed 1000 times using a stroke length of 10 mm, and the density obtained from the volume and the weight of the sample at that time is defined as a tap density.

[[[[Median diameter d50]]]
The median diameter d50 of the particles (secondary particle diameter when primary particles are aggregated to form secondary particles) is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, most The upper limit is usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, and most preferably 15 μm or less. Below the lower limit, high tap density products may not be obtained. When the upper limit is exceeded, it takes time to diffuse lithium in the particles, resulting in deterioration of the battery performance, or positive electrode formation of the battery, ie, active material When a conductive agent, a binder or the like is slurried with a solvent and applied in a thin film, problems such as streaking may occur. Here, by mixing two or more types of positive electrode active materials having different median diameters d50, it is possible to further improve the filling property at the time of preparation of the positive electrode.

  The median diameter d50 in the present invention is measured by a known laser diffraction / scattering type particle size distribution measuring apparatus. When LA-920 manufactured by HORIBA is used as a particle size distribution analyzer, a 0.1 mass% sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

[[[[Average primary particle size]]]
When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is usually 0.01 μm or more, preferably 0.05 μm or more, and more preferably 0.08 μm or more. Most preferably, it is 0.1 μm or more, usually 3 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and most preferably 0.6 μm or less. If the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder packing property or significantly lowers the specific surface area, which may increase the possibility that battery performance such as output characteristics may be degraded. is there. On the other hand, if the lower limit is exceeded, usually problems such as poor reversibility of charge and discharge may occur due to underdeveloped crystals.

  The primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000, the longest value of the intercept by the left and right boundary lines of the primary particle with respect to the straight line in the horizontal direction is obtained for any 50 primary particles, and the average value is obtained Be

[[[BET specific surface area]]]
The BET specific surface area of the positive electrode active material used in the secondary battery of the present invention is 0.2 m ² / g or more, preferably 0.3 m ² / g or more, more preferably 0.4 m ² / g or more, and the upper limit is 4.0 m ² / g or less, preferably 2.5 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 deteriorate, and if the BET specific surface area is large, it is difficult to increase the tap density, and problems may easily occur in the coatability when forming the positive electrode active material.

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

[[[Manufacturing method]]]
As a manufacturing method of a positive electrode active material, a general method is used as a manufacturing method of an inorganic compound. In particular, various methods can be considered to form a spherical or elliptical spherical active material. For example, transition metal raw materials such as transition metal nitrates and sulfates and, if necessary, raw materials of other elements such as water, etc. Dissolve or grind and disperse in a solvent, adjust pH while stirring to prepare a spherical precursor, dry it as necessary, and then Li such as LiOH, Li ₂ CO ₃ , LiNO ₃ etc. Method to obtain active material by adding source and calcining at high temperature, transition metal source material such as transition metal nitrate, sulfate, hydroxide, oxide etc. and source material of other element if necessary, solvent such as water It is dissolved or crushed and dispersed in it, and it is dry-formed by a spray drier etc. to form spherical or elliptical spherical precursor, to which Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ etc. is added and calcined at high temperature Methods of obtaining active materials, Transition metal source materials such as transition metal nitrates, sulfates, hydroxides and oxides, Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ and source materials of other elements as necessary, such as water It is dissolved or pulverized in a solvent, dried and molded by a spray dryer or the like to form a spherical or elliptical spherical precursor, which is calcined at high temperature to obtain an active material.

[[Configuration of positive electrode]]
The configuration of the positive electrode used in the present invention will be described below.
[[[[Electrode structure and preparation method]]]
The positive electrode is manufactured by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. The production of the positive electrode using the positive electrode active material can be carried out by a conventional method. That is, a positive electrode active material, a binder, and optionally a conductive material, a thickener and the like mixed in a dry state to form a sheet is pressure bonded to a positive electrode current collector, or a liquid medium of these materials A positive electrode can be obtained by forming a positive electrode active material layer on a current collector by applying it as a slurry by dissolving or dispersing it as a slurry and drying it.

  The content of the positive electrode active material in the positive electrode active material layer is usually 10% by mass or more, preferably 30% by mass or more, and particularly preferably 50% by mass or more. The upper limit is usually 99.9% by mass or less, preferably 99% by mass or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electrical capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient. In the present invention, one type of positive electrode active material may be used alone, or two or more types having different compositions or different powder physical properties may be used in any combination and ratio.

  In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press, or the like.

The electrode structure of the positive electrode active material layer is not particularly limited, but the density of the positive electrode active material layer present on the current collector is preferably 1.0 g / cm ³ or more, more preferably as the lower limit. Is 1.5 g / cm ³ , more preferably 2.0 g / cm ³ or more, and the upper limit is preferably 4.0 g / cm ³ or less, more preferably 3.5 g / cm ³ or less, still more preferably 3.0 g / Cm ³ or less. If this range is exceeded, the permeability of the electrolyte to the vicinity of the current collector / active material interface may be reduced, and in particular, the charge / discharge characteristics at high current density may be reduced. If it is lower than that, the conductivity between the active materials may be reduced, and the battery resistance may be increased.

[[[Conductive material]]]
As the conductive material, any known conductive material can be used. Specific examples thereof include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite; carbon blacks such as acetylene black; carbon materials such as amorphous carbon such as needle coke and the like. 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 Is used so as to be 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 to manufacture the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used at the time of electrode manufacture may be used. Resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber Rubber-like polymers such as butadiene rubber, ethylene / propylene rubber, etc .; styrene / butadiene / styrene block copolymer or its hydrogenated substance, EPDM (ethylene-propylene-diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric polymers such as isoprene / styrene block copolymers or their hydrogenated products; Syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefin copolymer Soft resinous polymers such as coalescing agents; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer etc .; alkali metal ions (especially lithium ion) And the like, and the like. One of these substances may be used alone, or two or more of these substances may be used in any combination and ratio.

  The proportion 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 It is at most mass%, more preferably at most 40 mass%, most preferably at most 10 mass%. If the proportion of the binder is too low, the positive electrode active material can not be sufficiently retained, and the mechanical strength of the positive electrode is insufficient, which may deteriorate battery performance such as cycle characteristics. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity.

[[[Liquid medium]]]
As a liquid medium for forming a slurry, any solvent can be used as long as it can dissolve or disperse the positive electrode active material, the conductive agent, the binder, and the thickener used if 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 methyl naphthalene; 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) And amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphaamide and dimethyl sulfoxide.

  In particular, when an aqueous medium is used, it is preferable to use a thickener and a latex such as styrene butadiene rubber (SBR) to make a slurry. Thickeners are usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. One of these may be used alone, or two or more of these may be used in any combination and ratio. When a thickener is further added, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 0.6% by mass or more. The upper limit is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. Below this range, the coatability may be significantly reduced. If it exceeds, the proportion of the active material in the positive electrode active material layer may be reduced, which may cause a problem of a decrease in battery capacity or an increase in resistance between the positive electrode active materials.

[[[Current collector]]]
There is no restriction | limiting in particular as a material of a positive electrode collector, A well-known thing can be used arbitrarily. Specific examples thereof include metal materials such as aluminum, stainless steel, nickel plating, titanium and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Among them, 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, punched metal, foamed metal and the like in the case of a metal material, and in the case of a carbonaceous material, a carbon plate, A carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. The thin film may be formed in a mesh shape as appropriate. The thickness of the thin film is arbitrary, but 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 ratio of the thickness of the current collector to the thickness of the positive electrode active material layer is not particularly limited, but (the thickness of the active material layer on one side immediately before the injection of the electrolyte) / (thickness of the current collector) is 150 or less Is 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 1 or more. If this range is exceeded, the current collector may generate Joule heat during high current density charge and discharge. Below this range, the volume ratio of the current collector to the positive electrode active material may increase, and the capacity of the battery may decrease.

[[[Electrode area]]]
In the case of using the non-aqueous electrolyte solution for a secondary battery of the present invention, it is preferable to make the area of the positive electrode active material layer larger than the outer surface area of the battery outer case from the viewpoint of exerting the low temperature output improvement effect larger. . Specifically, the sum of the electrode area of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 20 times or more in area ratio, and more preferably 40 times or more. The external surface area of the outer case means, in the case of a rectangular shape with a bottom, the total area obtained by calculation from the dimensions of the length, width and thickness of the case portion filled with the power generating element excluding the protruding portion of the terminal. . In the case of a bottomed cylindrical shape, it is a geometric surface area which approximates the case part filled with the power generation element excluding the protruding part of the terminal as a cylinder. The sum of the 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 formed by forming the positive electrode mixture layer on both sides via the current collector foil. , The sum of the area to calculate each face separately.

  The reason why the low temperature characteristics improvement effect of the non-aqueous electrolyte solution is amplified by setting the sum of the electrode area of the positive electrode to the surface area of the exterior of the secondary battery at 20 times or more in area ratio is unclear. There is a possibility that the reduction in resistance to lithium ion deintercalation reaction due to the large electrode area and the reduction in reaction resistance due to the non-aqueous electrolyte have some synergistic effect, and (2) the non-aqueous electrolyte of the present invention has viscosity Since the high ethylene carbonate content is suppressed, the permeability to the electrode mixture layer is good, and even when used for a battery with a large electrode surface area, the electrolyte sufficiently diffuses and penetrates to improve the output by the specific compound. There is a possibility that the effect has been largely drawn out. In order to take advantage of the effect of the above (2), it is preferable to simultaneously satisfy the size of the electrode surface area and the requirements of a high capacity battery and a low (direct current) resistance battery to be described later. These requirements realize a large output improvement effect by using it in combination with the non-aqueous electrolyte solution of the present invention, and taking a large surface area of the electrode is effective to express this effect without inhibiting it. It is because it is thought.

[[[Discharge capacity]]]
When the non-aqueous electrolyte solution of the present invention is used, the electric capacity (electric capacity when the battery is discharged from the fully charged state to the discharged state) of the battery element contained in one battery outer part of the secondary battery is 3 It is particularly preferable that the temperature is higher than the ampere-hour (Ah) because the improvement effect of the low temperature discharge characteristics is increased. Therefore, the positive electrode plate is preferably designed so that the discharge capacity is fully charged and is 3 amps hour (Ah) or more and less than 20 Ah, and more preferably 4 Ah or more and less than 10 Ah. If it is less than 3 Ah, the voltage drop due to the electrode reaction resistance may be large at the time of taking out a large current, and the power efficiency may be deteriorated. In this case, the low temperature discharge characteristics are also deteriorated, and the low temperature discharge characteristics obtained when using the non-aqueous electrolyte solution of the present invention containing 1% by volume or more and 25% by volume or less ethylene carbonate and the specific compound in the non-aqueous solvent. Improvement may be insufficient. At 20 Ah or more, the electrode reaction resistance decreases and the power efficiency improves, but the temperature distribution due to heat generation inside the battery during pulse charge and discharge is large, the durability of charge and discharge repetition is poor, and abnormalities such as overcharge and internal short circuit When the heat release efficiency worsens due to sudden heat generation at the time, the internal pressure rises and the phenomenon that the gas release valve operates (valve operation) and the phenomenon that the contents of the battery are violently spouted out (burst) increase There is.

[[[[Positive 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 mixture layer obtained by subtracting the metal foil thickness of the core material is 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.

[Negative electrode]
The negative electrode used for the non-aqueous electrolyte secondary battery of the present invention will be described below.
[[Anode active material]]
The negative electrode active material used for the negative electrode will be described below.

[[[composition]]]
The negative electrode active material is not particularly limited as long as it can occlude and release lithium ions electrochemically, and carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal complex oxides, lithium alone And lithium alloys such as lithium aluminum alloys, metals which can be alloyed with lithium such as Sn and Si, and the like. One of these may be used alone, or two or more of these may be used in any combination and ratio. Among them, 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 it is preferable from the viewpoint of high current density charge and discharge characteristics that titanium and / or lithium is contained as a component.

As a carbonaceous material,
(1) Natural graphite,
(2) artificial carbonaceous material and artificial graphitic material; carbonaceous material {eg, natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch or those obtained by oxidizing these pitches, needle coke, pitch Pyrolysates of organic matter such as coke and carbon material partially graphitized thereof, furnace black, acetylene black, pitch-based carbon fiber, carbonizable organic matter (eg coal tar pitch from soft pitch to hard pitch, or dry distillation liquefaction) Heavy oil such as coal-based heavy oil, normal pressure residual oil, direct-current heavy oil of reduced pressure residual oil, crude oil, ethylene tar such as heavy petroleum oil which is by-produced during pyrolysis of naphtha, acenaphthylene, decacyclene, Aromatic hydrocarbons such as anthracene and phenanthrene, N-ring compounds such as phenazine and acridine, thiophene and bithiophene Ring compounds, polyphenylenes such as biphenyl and terphenyl, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized products thereof, organic polymers such as nitrogen-containing polyacrylonitrile and polypyrrole, sulfur-containing polythiophenes, Organic polymers such as polystyrene, natural polymers such as polysaccharides represented by cellulose, lignin, mannan, polygalactouronic acid, chitosan and sucrose, 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 dissolved in low molecular organic solvents such as benzene, toluene, xylene, quinoline and n-hexane and the like Charcoal Carbon material is heat treated one or more times in a range things} from 400 3200 ° C.,

(3) A carbon material having an interface in which the negative electrode active material layer is made of at least two or more different crystalline carbonaceous substances and / or in which the different crystalline carbonaceous substances are in contact with each other
(4) A carbon material having an interface in which the negative electrode active material layer is made of at least two or more kinds of different orientations of carbonaceous matter and / or at which the different orientation carbonaceous matter contacts
The balance among initial irreversible capacity and high current density charge / discharge characteristics is preferable.

[[Configuration, Physical Properties, Preparation Method of Negative Electrode]]
A property of a carbonaceous material, a negative electrode containing the carbonaceous material and an electrode forming method, a current collector, and a lithium ion secondary battery, any one or more of the following (1) to (19) It is desirable to satisfy at the same time.

(1) X-ray parameter In the carbonaceous material, 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, usually 0.360 nm It is desired that the thickness be as follows, preferably 0.350 nm or less, 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 1.0 nm or more, and more preferably 1.5 nm or more.

(2) Ash content The ash content contained in the carbonaceous material is 1% by mass or less, in particular 0.5% by mass or less, particularly 0.1% by mass or less, and the lower limit is 1 ppm or more based on the total mass of the carbonaceous material Is preferred. If the above range is exceeded, the deterioration of the battery performance due to the reaction with the electrolyte during charge and discharge may not be negligible. Below this range, manufacturing may require a lot of time, energy and equipment for preventing pollution, which may increase the cost.

(3) Volume-Based Average Particle Size The volume-based average particle size of the carbonaceous material is usually 1 μm or more, preferably 3 μm or more, more preferably the volume-based average particle size (median diameter) determined by laser diffraction / scattering method Is 5 μm or more, more preferably 7 μm or more. The upper limit is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less. Below the above range, the irreversible capacity may increase, which may lead to the loss of the initial battery capacity. If the above range is exceeded, a non-uniform coated surface is likely to be formed when preparing the electrode by coating, which may be undesirable in the battery manufacturing process.

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

(4) Raman R value, Raman half value width The Raman R value of the carbonaceous material measured using argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.03 or more, more preferably 0.10 or more The upper limit thereof is 1.50 or less, preferably 1.2 or less, more preferably 1.0 or less, and still more preferably 0.50 or less. If the R value is below this range, the crystallinity of the particle surface may be too high, and sites for Li to enter into the layer may be reduced with charge and discharge. That is, the chargeability may be reduced. In addition, when the negative electrode is densified by pressing after being applied to the current collector, crystals may be easily oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if this range is exceeded, the crystallinity of the particle surface may be reduced, the reactivity with the electrolytic solution may be increased, and the efficiency may be reduced or the gas generation may be increased.

The Raman half value width in the vicinity of 1580 cm ^{-1 of the} carbonaceous material 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 80 cm ^-1 or less, More preferably, it is in the range of 60 cm ^-1 or less, still more preferably 40 cm ^-1 or less. If the Raman half width is below this range, the crystallinity of the particle surface may be too high, and sites for Li to enter into the layer may be reduced as charge and discharge occur. That is, the chargeability may be reduced. In addition, when the negative electrode is densified by pressing after being applied to the current collector, crystals may be easily oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if this range is exceeded, the crystallinity of the particle surface may be reduced, the reactivity with the electrolytic solution may be increased, and the efficiency may be reduced or the gas generation may be increased.

The measurement of the Raman spectrum is carried out using a Raman spectrometer (for example, Raman spectrometer manufactured by JASCO Corporation), allowing the sample to fall naturally into the measurement cell and filling it, while irradiating the sample surface in the cell with argon ion laser light , By rotating the cell in a plane perpendicular to the laser light. 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. In addition, 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: 514.5 nm
・ Laser power on sample: 15 to 25 mW
・ Resolution: 10 to 20 cm ^-1
・ Measurement range: 1100 cm ^{-1 to} 1730 cm ^-1
・ Raman R value, half width analysis: background processing,
・ Smoothing processing: Simple average, convolution 5 points

(5) BET Specific Surface Area The specific surface area of the carbonaceous material 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, it is 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, still more preferably 10 m ² / g or less. If the value of the specific surface area falls below this range, the acceptability of lithium at the time of charging when used as a negative electrode material tends to deteriorate, and lithium tends to precipitate on the electrode surface, which may cause safety problems. On the other hand, if it exceeds this range, the reactivity with the electrolyte increases when used as a negative electrode material, gas generation tends to be large, and it may be difficult to obtain a preferable battery.
The specific surface area by the BET method is the relative pressure of nitrogen to atmospheric pressure after performing predrying for 15 minutes at 350 ° C. under flowing nitrogen with a sample using a surface area meter (for example, Okura Riken fully automatic surface area measurement device) Using a nitrogen-helium mixed gas accurately adjusted so that the pressure value becomes 0.3, the value measured by the nitrogen adsorption BET one-point method by the gas flow method is used.
(6) Pore size distribution The pore size distribution of the carbonaceous material is determined by Hg porosimetry (mercury intrusion method), and the voids in the particle corresponding to the pore diameter of 0.01 μm or more and 1 μm or less, the particle surface The amount of irregularities due to steps, the contact surface 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 Is in the range of 0.4 mL / g or less, more preferably 0.3 mL / g or less. If this range is exceeded, a large amount of binder may be required during electrode plate formation. If it is lower than this, the high current density charge / discharge characteristics may be deteriorated, and the effect of alleviating expansion and contraction of the electrode during charge and 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 at the time of electrode plate formation. If it is lower than that, the dispersing effect of the thickener and the binder may not be obtained at the time of electrode plate formation.

  The average pore diameter is preferably 0.05 μm or more, more preferably 0.1 μm or more, still more preferably 0.5 μm or more, and the upper limit thereof is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less It is. Above this range, a large amount of binder may be required. Below this range, the high current density charge / discharge characteristics may be degraded.

  As an apparatus for Hg porosimetry, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex) was used. About 0.2 g of the sample was sealed in a powder cell and degassed for 10 minutes at room temperature under vacuum (50 μm Hg or less) for pretreatment. Subsequently, the pressure was reduced to 4 psia (about 28 kPa), mercury was introduced, the pressure was stepped up from 4 psia (about 28 kPa) to 40,000 psia (about 280 MPa), and the pressure was reduced to 25 psia (about 170 kPa). The number of steps for boosting was 80 points or more, and in each step, the amount of mercury intrusion was measured after an equilibration time of 10 seconds. 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 °. The average pore size was the pore size at which the cumulative pore volume was 50%.

(7) Degree of circularity The degree of circularity is used as the degree of spherical shape of the carbonaceous material, and the degree of circularity of particles having a particle diameter 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, it is 0.85 or more, Most preferably, it is 0.9 or more. If the degree of circularity is large, high current density charge / discharge characteristics are improved, which is preferable.

The degree of circularity is defined by the following equation, and when the degree of circularity is 1, it becomes a theoretical perfect sphere.
Circularity = (perimeter of equivalent circle having the same area as particle projection shape) / (actual perimeter of particle projection shape)

  As the value of circularity, for example, using a flow-type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.), about 0.2 g of a sample is made of polyoxyethylene (20) sorbitan monolaurate which is a surfactant. After dispersing in a 0.2 mass% aqueous solution (about 50 mL) and irradiating 28 kHz ultrasonic waves with an output of 60 W for 1 minute, the detection range is specified to 0.6 to 400 μm, and the particle size is 3 to 40 μm Use the value measured for.

  The method for improving the degree of circularity is not particularly limited, but it is preferable to use a sphericizing treatment to make it spherical since the shape of the interparticle voids when the electrode body is formed is completed. As an example of the spheroidizing process, a mechanical force or a mechanical processing method in which a plurality of fine particles are granulated by a binder or the adhesive force of the particles themselves, etc. Can be 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, further preferably 2.0 g / cm ^3. It is cm ³ or more, 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 carbon is so low that the initial irreversible capacity may increase. In the present invention, the true density is defined as one measured by a liquid phase displacement 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, particularly preferably 1. It is desirable that it is 0 g / cm ³ or more. Also, it is preferably 2.0 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 this range is exceeded, the gaps between particles in the electrode become too small, it may be difficult to ensure the conductivity between particles, and it may be difficult to obtain desirable battery characteristics. The tap density is measured and defined in the same manner as the method described in the section of the positive electrode active material.

(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 within the range of 0.67 or less is there. Below this range, the high density charge and discharge characteristics may be degraded. The orientation ratio is measured by X-ray diffraction after pressure-molding the sample.

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 is set using clay to be flush with the surface of the sample holder for measurement and X-ray diffraction Measure The ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated from the peak intensities of (110) diffraction and (004) diffraction of the obtained carbon, and is 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 (K α ray) graphite monochromator Slit: divergence slit = 0.5 degrees, light receiving slit = 0.15 mm, scattering slit = 0.5 degrees 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 thereof is 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaks may occur at the time of forming an electrode plate, or a uniform coated surface may not be obtained, and the high current density charge / discharge characteristics may be degraded.

  The aspect ratio is represented by A / B, where A is the longest diameter of the carbon material particle when observed three-dimensionally, and B is the shortest diameter orthogonal to the diameter. The carbon particles are observed with a scanning electron microscope capable of magnified observation. Select any 50 graphite particles fixed to the end face of metal with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed for each, measure A and B, and measure A / B average Determine the value.

(12) Admixture of Adjuncts The term “adjunct mixed” means containing two or more kinds of carbonaceous materials having different properties in the negative electrode and / or in the negative electrode active material. The properties mentioned here are 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 the characteristics. In a particularly preferred embodiment, the volume-based particle size distribution is not symmetrical when centered on the median diameter, contains two or more kinds of carbonaceous materials having different Raman R values, and X-ray parameters There are different things, etc.

  As an example, carbon materials such as natural graphite, graphite such as artificial graphite (graphite), carbon black such as acetylene black, amorphous carbon such as needle coke, etc. are contained as a conductive agent, and thus electrical resistance is achieved. And reducing. One of these may be used alone, or two or more of these may be used in any combination and ratio. When added as a conductive agent, 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, it may be difficult to obtain the effect of conductivity improvement. If exceeded, it may lead to an increase in initial irreversible capacity.

(13) Production of electrode Production of the electrode may be performed according to a conventional method. For example, a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler and the like are added to the negative electrode active material to form a slurry, which is applied to a current collector, dried and pressed. Can. The thickness of the negative electrode active material layer per one side immediately before the electrolyte injection step 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 usually 150 μm or less, preferably It is 120 μm or less, more preferably 100 μm or less. If this range is exceeded, the electrolyte may not easily penetrate to the vicinity of the current collector interface, and the high current density charge / discharge characteristics may be degraded. In addition, if it is below this range, the volume ratio of the current collector to the negative electrode active material may increase, and the capacity of the battery 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. As the current collector of the negative electrode, metal materials such as copper, nickel, stainless steel, nickel plated steel and the like can be mentioned. Among them, copper is particularly preferable in view of easiness 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, punched metal, foamed metal and the like. Among them, preferably a metal thin film, more preferably a copper foil, more preferably a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method, both of which can be used as a current collector. When the thickness of the copper foil is thinner 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.

  The current collector made of copper foil manufactured by the rolling method is hard to be broken even if the negative electrode is tightly rounded or rounded at an acute angle because the copper crystals are aligned in the rolling direction, and it is suitably used for small cylindrical batteries be able to. In the electrolytic copper foil, for example, a metal drum is immersed in an electrolytic solution in which copper ions are dissolved, and current is supplied while rotating this to deposit copper on the surface of the drum and peel it off. It is obtained. Copper may be deposited on the surface of the above-mentioned rolled copper foil by an electrolytic method. Roughening treatment or surface treatment (for example, chromate treatment with a thickness of several nm to about 1 μm, base treatment with Ti, etc.) may be performed on one side or both sides of the copper foil.

The following physical properties are further desired for the current collector substrate.
(1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material thin film-formed surface of the current collector substrate specified by the method described in JIS B 0601-1994 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, and particularly preferably 1.0 μm or less.

  By setting the average surface roughness (Ra) of the current collector substrate in the range between the lower limit and the upper limit described above, good charge / discharge cycle characteristics can be expected. By setting it as the said lower limit or more, the area of an interface with a negative electrode active material thin film becomes large, and adhesiveness with a negative electrode active material thin film improves. The upper limit value 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 a foil 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, particularly preferably 500 N / mm ² It is above.

  The tensile strength is a value obtained by dividing the maximum tensile force required for a test specimen to a break by the cross-sectional area of the test specimen. 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 high tensile strength, cracks in the current collector substrate due to expansion and contraction of the negative electrode active material thin film accompanying charging and 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 load required to give 0.2% plastic (permanent) strain, and 0.2% deformation occurs even after unloading with this magnitude of load. Is meant to be 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 and contraction of the negative electrode active material thin film accompanying charging and discharging can be suppressed, and good cycle characteristics can be obtained. Can.

  The thickness of the metal thin film is optional, but is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. The upper limit is usually 1 mm or less, preferably 100 μm or less, and more preferably 30 μm or less. If the thickness is less than 1 μm, the strength may be reduced, which may make application difficult. Moreover, when it becomes thicker than 100 micrometers, the shape of electrodes, such as winding, may be changed. The metal thin film may be in the form of mesh.

(15) Ratio of Thickness of Current Collector to Active Material Layer Although the ratio of thickness of the current collector to the active material layer is not particularly limited, ((active material layer thickness on one side immediately before pouring of electrolyte)) / The (thickness of the current collector) 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 Preferably it is one or more ranges. If this range is exceeded, the current collector may generate Joule heat during high current density charge and discharge. Below this range, the volume ratio of the current collector to the negative electrode active material may increase, and the capacity of the battery may decrease.

(16) Electrode Density The electrode structure when making the negative electrode active material 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 more preferably 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 The range is more preferably 1.7 g / cm ³ or less. If this range is exceeded, the active material particles may be destroyed, which may lead to an increase in initial irreversible capacity and a deterioration in high current density charge / discharge characteristics due to a decrease in the permeability of the electrolyte to the vicinity of the current collector / active material interface. On the other hand, if it is lower than that, the conductivity between the active materials may be reduced, the battery resistance may be increased, and the capacity per unit volume may be reduced.

(17) Binder The binder for binding the active material is not particularly limited as long as it is a material stable to the solvent used in the production of the electrolytic solution and the electrode. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, etc .; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR ( Rubber-like polymers such as acrylonitrile-butadiene rubber), ethylene-propylene rubber, etc .; styrene-butadiene-styrene block copolymer or its hydrogenated substance; EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-ethylene Thermoplastic elastomeric polymers such as butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or their hydrogenated products; Syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinegar Soft resinous polymers such as vinyl copolymers and propylene / α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymers Examples of such a polymer composition include molecules and ion conductivity of alkali metal ions (particularly lithium ions). One of these may be used alone, or two or more of these may be used in any combination and ratio.

The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive agent used as needed. Instead, either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methyl pyrrolidone (NMP), dimethylformamide, dimethyl acetamide, methyl acetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyl triamine, N , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphaamide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like. .
In particular, in the case of using an aqueous solvent, a dispersant or the like is added to the above-mentioned thickener together with the above-mentioned thickener, and a slurry such as SBR is used. 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 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 usually 20% by mass or less, preferably Is in the range of 15% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less. If this range is exceeded, the proportion of the binder that is a component that does not contribute to the battery capacity in the negative electrode active material layer may be excessive, which may lead to a decrease in battery capacity. If it is lower than that, the strength of the negative electrode may be reduced. In particular, when the main component contains a rubbery polymer represented 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, more preferably 0. The upper limit is 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the main component contains a fluorine-based polymer represented by polyvinylidene fluoride, the ratio to the active material is 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more, The upper limit is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

  Thickeners are usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. One of these may be used alone, or two or more of these may be used in any combination and 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, and the upper limit The amount of H is as follows: 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. Below this range, the coatability may be significantly reduced. If it exceeds, the proportion of the active material in the negative electrode active material layer may be reduced, which may cause a problem of a decrease in battery capacity or an increase in resistance between the negative electrode active materials.

(18) Polar plate orientation ratio The polar plate 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 the theoretical value of 0.67 or less. Below this range, the high density charge and discharge characteristics may be degraded.
The measurement of the plate orientation ratio is as follows. With respect to the negative electrode after pressing to a target density, the active material orientation ratio of the electrode is measured by X-ray diffraction. Although the specific method is not particularly limited, as a standard method, peak separation is performed by fitting peaks of (110) diffraction and (004) diffraction of carbon by X-ray diffraction using asymmetric Pearson VII as a profile function And calculate the integrated intensities of the (110) and (004) diffraction peaks, respectively. From the obtained integrated intensity, a ratio represented by (110) diffracted integrated intensity / (004) diffracted integrated intensity is calculated. The active material orientation ratio of the electrode calculated by the measurement is defined as an 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: Divergent slit = 1 degree, light 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 Adjustment: Fix the electrode with a 0.1 mm thick double-sided tape on the glass plate

(19) Impedance The resistance of the negative electrode when charged to 60% of the nominal capacity from the discharged state is preferably 100 Ω or less, particularly preferably 50 Ω or less, more preferably 20 Ω or less, and / or the double layer capacity is 1 × 10 ^−6. It is preferably F or more, particularly preferably 1 × 10 ⁻⁵ F or more, and more preferably 1 × 10 ⁻⁴ F or more. 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 charge a nominal capacity in 5 hours, then maintained without charge / discharge for 20 minutes, and then discharged at a current value that can discharge the nominal capacity in 1 hour Use one that has a capacity of at least 80% of the nominal capacity. With respect to the lithium ion secondary battery in the discharged state described above, the nominal capacity is charged to 60% of the nominal capacity at a current value capable of charging in 5 hours, and the lithium ion secondary battery is immediately transferred into a glove box under an argon gas atmosphere. Here, the lithium ion secondary battery is quickly disassembled and taken out in a state where the negative electrode does not discharge or short-circuit, and in the case of 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 sheets of the electrode are punched out to 12.5 mm in diameter, and they are opposed via a separator so that the active material surface does not shift. 60 μL of an electrolytic solution used in the battery is dropped between the separator and the negative electrodes to be in close contact, and a state in which the electrolyte is not in contact with the outside air is maintained. The measurement is performed at a temperature of 25 ° C. and complex impedance measurement in a frequency band of 10 ^-2 to 10 ⁵ Hz, and the arc of the negative electrode resistance component of the determined Cole-Cole plot is approximated by a semicircle to obtain surface resistance (R). And the double layer capacity (Cdl) is determined.

  Although the area of the negative electrode plate is not particularly limited, it is designed to be slightly larger than the facing positive electrode plate so that the positive electrode plate does not protrude from the negative electrode plate. From the viewpoint of suppressing cycle life after repeated charging and discharging and deterioration due to high-temperature storage, it is preferable to bring the area as close as possible to the positive electrode as much as possible, since the electrode ratio working more uniformly and effectively is improved and the characteristics are improved. The design of this electrode area is important especially when used at high current.

  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 material layer obtained by subtracting the metal foil thickness of the core material is usually 15 μm or more The upper limit is usually 150 μm or less, preferably 120 μm or less, and more preferably 100 μm or less.

[Separator]
The separator used in the non-aqueous electrolytic solution secondary battery of the present invention has a predetermined mechanical strength to electrically insulate between both electrodes, has a high ion permeability, and the oxidizing property and the negative electrode on the side in contact with the positive electrode It is not particularly limited as long as it has resistance to reducibility on the side. Resin, an inorganic substance, glass fiber etc. are used as a material of the separator which has such a required characteristic. As the resin, an olefin-based polymer, a fluorine-based polymer, a cellulose-based polymer, a polyimide, a nylon or the like is used. Specifically, it is preferable to select from materials which are stable to the electrolytic solution and excellent in liquid retention, and it is preferable to use a porous sheet or non-woven fabric made of polyolefin such as polyethylene and polypropylene as a raw material.

  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 in the form of particles or fibers are used. As the form, a thin film such as a non-woven fabric, a woven fabric and a microporous film is used. In the thin film form, one having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is suitably used. In addition to the above-described independent thin film shape, a separator can be used in which a composite porous layer containing particles of the inorganic substance is formed on the surface layer of a positive electrode and / or a negative electrode using a resin binder. For example, alumina particles having a 90% particle diameter of less than 1 μm may be formed as porous layers on both sides of the positive electrode using a fluorine resin binder.

[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate described above are interposed with the separator described above, or a structure in which the positive electrode plate and the negative electrode plate described above are spirally wound with the separator interposed therebetween. Any may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is preferably 40% to 90%, and more preferably 50% to 80%. If the electrode group occupancy rate is less than 40%, the battery capacity is small, and if it is 90% or more, the void space is small, and the temperature of the battery becomes high to cause the members to expand and the vapor pressure of the liquid component of the electrolyte is high. As a result, the internal pressure rises, which may lower various characteristics such as charge and discharge repetition performance as a battery and high temperature storage, or the gas release valve may release the internal pressure to the outside.

[Current collection structure]
The current collecting structure is not particularly limited, but in order to more effectively realize the improvement of the low temperature discharge characteristics by the non-aqueous electrolyte solution of the present invention, it is necessary to make the structure of reducing the resistance of the wiring portion and the bonding portion There is. When the internal resistance is small, the effect of using the non-aqueous electrolyte solution of the present invention is particularly well exhibited. When the electrode group has the above-described laminated structure, a structure in which the metal core portions of the respective electrode layers are bundled and welded to the terminal is preferably used. When the area of one electrode increases, the internal resistance increases, so it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the above-described wound structure, the internal resistance can be lowered by providing a plurality of lead structures on the positive electrode and the negative electrode respectively and bundling them in the terminals.

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

  The non-aqueous electrolytic solution of the present invention is effective in reducing the reaction resistance involved in the removal and insertion of lithium from the electrode active material, and it is considered that this is a factor which can realize good low temperature discharge characteristics. However, it has been found that in a normal battery in which the direct current resistance is greater than 10 mΩ, the effect of reducing the reaction resistance can not be reflected 100% on the low temperature discharge characteristics due to the inhibition by the direct current resistance. By preparing a battery with a small direct current resistance component, this can be improved and the effects of the non-aqueous electrolyte solution of the present invention can be sufficiently exhibited. In addition, from the viewpoint of drawing out the effect of the non-aqueous electrolyte and producing a high-power battery, the electric capacity of the battery element contained in one of the battery sheaths of the above-described secondary battery and this requirement It is particularly preferred to simultaneously satisfy the requirement that the electrical capacity when discharged from the fully charged state to the discharged state is 3 amp-hours (Ah) or more.

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

In the outer case using the metals, the metals are welded together by laser welding, resistance welding, ultrasonic welding to form a hermetically sealed structure, or a caulking structure using the metals through a resin gasket. The ones that
In the outer case using the laminate film, those having a sealing and sealing structure by thermally fusing the resin layers to each other may be mentioned. A resin different from the resin used for the laminate film may be interposed between the resin layers in order to improve the sealability. In particular, in the case where the resin layer is heat-sealed through the current collection terminal to form a sealed structure, the metal and the resin are joined, and therefore, a resin having a polar group or a modification having a polar group introduced as an intervening resin Resin is preferably used.

[Protective element]
As the above-mentioned protective element, PTC (Positive Temperature Coefficient), which has an increase in resistance when abnormal heat generation or excessive current flows, thermal fuse, thermistor, current flowing in the circuit due to rapid increase in internal pressure of battery or internal temperature at abnormal heat generation. Valve (current cut-off valve) etc. which cut off. The protective element is preferably selected under conditions which do not operate under normal use of a high current, and from the viewpoint of high output, it is more preferable to design it not to lead to abnormal heat generation or thermal runaway without a protective element.

EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples and comparative examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.
<Fabrication of secondary battery>
[Production of positive electrode]
90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, 5% by mass of polyvinylidene fluoride (PVdF) as a binder, N-methylpyrrolidone solvent The mixture was mixed and slurried. The obtained slurry is applied on both sides of a 15 μm thick aluminum foil, dried, and rolled to a thickness of 80 μm with a press, and the size of the active material layer is 100 mm wide, 100 mm long and 30 mm wide uncoated It cut out to the shape which has an operation part, and was set as the positive electrode.

[Fabrication of negative electrode]
100 parts by weight of an aqueous dispersion of carboxymethylcellulose sodium (concentration of 1% by mass of sodium carboxymethylcellulose) as a thickener and a binder in 98 parts by weight of artificial graphite powder KS-44 (trade name of Timcal) Then, 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber (the concentration of 50% by mass of styrene-butadiene rubber) was added and mixed by a disperser to make a slurry. The obtained slurry was applied on both sides of a 10 μm thick copper foil, dried, and rolled to a thickness of 75 μm with a press, and the size of the active material layer was 104 mm wide, 104 mm long and 30 mm wide uncoated. It cut out in the shape which has an operation part, and was set as the negative electrode.

[Assembly of battery]
32 positive electrodes and 33 negative electrodes were alternately arranged, and laminated so that a porous polyethylene sheet separator (25 μm in thickness) was sandwiched between the electrodes. Under the present circumstances, it was made to face so that the positive electrode active material surface might not remove | deviate from the inside of a negative electrode active material surface. The uncoated parts of each of the positive electrode and the negative electrode were welded to produce a current collecting tab, and the electrode group was sealed in a battery can (outside size: 120 × 110 × 10 mm). Thereafter, 20 mL of a non-aqueous electrolytic solution was injected into a battery can in which the electrode group was loaded, and the electrode was sufficiently impregnated with the non-aqueous electrolytic solution, and the battery was sealed to prepare a square battery. The rated discharge capacity of this battery is about 6 Ah and the direct current resistance measured by the 10 kHz alternating current method is about 5 milliohms.

[Evaluation of battery]
(Measurement method of initial capacity)
With respect to the new battery which has not been charged / discharged, 5 cycles initial charge / discharge was performed at 25 ° C. and 25 ° C. in a voltage range of 4.1 V to 3.0 V (voltage range of 4.1 V to 3.0 V). The initial capacity is the fifth cycle 0.2 C at this time (the current value for discharging the rated capacity by the discharge capacity at an hourly rate in 1 hour is 1 C, and so forth).

(Measurement method of low temperature output)
Charge for 150 minutes at a constant current of 0.2 C in a 25 ° C. environment, and discharge for 10 seconds at 0.1 C, 0.3 C, 1.0 C, 3.0 C, 5.0 C in a −30 ° C. environment, The voltage at that 10 second was measured. The area of a triangle surrounded by the current-voltage straight line and the lower limit voltage (3 V) was taken as the output (W).

Example 1
In a dry argon atmosphere, add 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) to a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 15: 85) and dissolve it, An amount of 0.3% by mass of hexamethylcyclotrisiloxane was mixed with the mixed solution to prepare a non-aqueous electrolytic solution. A battery was produced by the above-mentioned method using this non-aqueous electrolytic solution, and the low temperature output was measured. The results are shown in Table 1.

Example 2
In Example 1, a battery was produced using a non-aqueous electrolytic solution prepared at a volume ratio of EC: EMC of 20:80, and the low-temperature output was measured. The results are shown in Table 1.

Example 3
In Example 1, a battery was prepared using a non-aqueous electrolyte prepared by changing to a mixture of EC, dimethyl carbonate (DMC), and EMC (volume ratio 15:40:45) as a non-aqueous solvent, and low temperature output was obtained. It was measured. The results are shown in Table 1.

Example 4
In Example 1, a battery was produced using a non-aqueous electrolytic solution in which phenyldimethylfluorosilane was mixed instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Example 5
In Example 1, a battery was produced using a non-aqueous electrolytic solution in which hexamethyldisiloxane was mixed instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Example 6
In Example 1, a battery was produced using a non-aqueous electrolyte prepared by mixing trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Example 7
In Example 1, a battery was produced using a non-aqueous electrolytic solution in which methyl fluorosulfonate was mixed instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Example 8
In Example 1, lithium nitrate was mixed instead of hexamethylcyclotrisiloxane, and a battery was manufactured using a non-aqueous electrolytic solution stored for 3 days, and the low temperature output was measured. The results are shown in Table 1.

Example 9
In Example 1, lithium difluorophosphate prepared according to the method described in pages 581 to 582 of Inorganic Nuclear Chemistry Letters (1969), 5 (7) as a non-aqueous electrolytic solution in place of hexamethylcyclotrisiloxane. The battery was manufactured using the non-aqueous electrolyte mixed with the above, and the low temperature output was measured. The results are shown in Table 1.

Example 10
In Example 9, a battery is manufactured using a non-aqueous electrolytic solution in which the mixing amount of lithium difluorophosphate is changed to an amount of 0.08 mass% with respect to the mixed solution of non-aqueous solvent and lithium hexafluorophosphate. And the low temperature output was measured. The results are shown in Table 1.

Example 11
In Example 1, lithium acetate was mixed instead of hexamethylcyclotrisiloxane, and a battery was manufactured using a non-aqueous electrolytic solution stored for 3 days, and the low-temperature output was measured. The results are shown in Table 1.

Example 12
<Fabrication of secondary battery-2>
[Production of positive electrode]
90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, 5% by mass of polyvinylidene fluoride (PVdF) as a binder, N-methylpyrrolidone solvent The mixture was mixed and slurried. The obtained slurry was applied onto both sides of a 20 μm thick aluminum foil, dried, and rolled to a thickness of 80 μm with a press, and cut into 52 mm wide and 830 mm long, and used as a positive electrode. However, a 50 mm non-coated portion is provided in the longitudinal direction on both the front and back, and the length of the active material layer is 780 mm.

[Fabrication of negative electrode]
100 parts by weight of an aqueous dispersion of carboxymethylcellulose sodium (concentration of 1% by mass of sodium carboxymethylcellulose) as a thickener and a binder in 98 parts by weight of artificial graphite powder KS-44 (trade name of Timcal) Then, 2 parts by weight of an aqueous dispersion of styrene-butadiene rubber (the concentration of 50% by mass of styrene-butadiene rubber) was added and mixed by a disperser to make a slurry. The obtained slurry is uniformly coated on both sides of a 18 μm-thick copper foil as a negative electrode current collector, dried, and then rolled to a thickness of 85 μm with a press and cut into a width of 56 mm and a length of 850 mm. It was a negative electrode. However, a non-coated portion of 30 mm is provided in the longitudinal direction on both the front and back.

[Preparation of electrolyte solution]
A non-aqueous electrolytic solution similar to that of Example 1 was produced.
[Assembly of battery]
The positive electrode and the negative electrode were stacked together and wound with a polyethylene separator so that the positive electrode and the negative electrode were not in direct contact with each other, and used as an electrode body. The terminals of the positive and negative electrodes were housed outside the battery can. Subsequently, 5 mL of an electrolytic solution to be described later was injected into this, and then caulking was performed to fabricate an 18650 type cylindrical battery. The rated discharge capacity of this battery was about 0.7 amp-hours (Ah), and the direct current resistance measured by the 10 kHz AC method was about 35 milliohms (mΩ). Moreover, the sum total of the electrode area of the said positive electrode with respect to the surface area of the exterior of this secondary battery is 19.4 times in area ratio. In the above-mentioned battery, the low temperature output was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
In Example 1, a battery was produced using a non-aqueous electrolyte prepared without mixing hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative example 2
In Example 2, a battery was produced using a non-aqueous electrolyte prepared without mixing hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative example 3
In Example 3, a battery was produced using a non-aqueous electrolytic solution prepared without mixing hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative example 4
Lithium hexafluorophosphate (LiPF ₆ ) is added to a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 4: 6) in a dry argon atmosphere so as to be 1 mol / L, and this mixed solution is dissolved. A non-aqueous electrolytic solution was prepared by mixing 0.3% by mass of hexamethylcyclotrisiloxane.
A battery was produced using this non-aqueous electrolytic solution, and the low temperature output was measured. The results are shown in Table 1.

Comparative example 5
In Comparative Example 4, a battery was produced using a non-aqueous electrolytic solution in which phenyldimethyl fluorosilane was mixed instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative example 6
In Comparative Example 4, a battery was produced using a non-aqueous electrolytic solution in which hexamethyldisiloxane was mixed instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative example 7
In Comparative Example 4, a battery was produced using a non-aqueous electrolyte prepared by mixing trimethylsilyl methanesulfonate instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative Example 8
In Comparative Example 4, a battery was produced using a non-aqueous electrolyte in which methyl fluorosulfonate was mixed instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative Example 9
In Comparative Example 4, lithium nitrate was mixed instead of hexamethylcyclotrisiloxane, and a battery was manufactured using a non-aqueous electrolytic solution stored for 3 days, and the low-temperature output was measured. The results are shown in Table 1.

Comparative example 10
In Comparative Example 4, a battery was produced using a non-aqueous electrolytic solution in which lithium difluorophosphate was mixed instead of hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative example 11
In Comparative Example 4, lithium acetate was mixed instead of hexamethylcyclotrisiloxane, and a battery was produced using a non-aqueous electrolytic solution stored for 3 days, and the low-temperature output was measured. The results are shown in Table 1.

Comparative Example 12
In Comparative Example 4, a battery was produced using a non-aqueous electrolytic solution prepared without mixing hexamethylcyclotrisiloxane, and the low-temperature output was measured. The results are shown in Table 1.

Comparative Example 13
In Example 12, a battery was produced using the non-aqueous electrolyte solution as in Comparative Example 1, and the low-temperature output was measured. The results are shown in Table 1.

  As apparent from Table 1, the lithium secondary batteries of Examples 1 to 11 containing specific amounts of EC and specific compounds in a non-aqueous electrolyte contain excess amounts of EC and do not contain specific compounds. Not only the lithium secondary battery of Example 12, but the lithium amount of Comparative Examples 1 to 3 in which the EC amount falls within the specific range but does not contain the specific compound, and lithium in Comparative Examples 4 to 11 in which the EC is excessive in the one containing the specific compound It was found that the low temperature output characteristics were improved as compared with the second ground. In addition, the lithium secondary battery of Example 12 containing a specific amount of EC and a specific compound in a non-aqueous electrolyte solution has the amount of EC falling within the specific range, but the lithium secondary battery of Comparative Example 13 containing no specific compound. It was found that the low temperature output characteristics were improved compared to the ground.

  Also, this effect is not a simple combination of the two, and the effect is clearly amplified by satisfying both conditions. Table 1 shows the increase rate of low-temperature output when using a non-aqueous electrolyte containing the specific compound (with the same composition except for the non-aqueous electrolyte containing no specific compound). This value is larger in Examples 1 to 12 than in Comparative Examples 4 to 11 in which the amount of EC is excessive, and the magnitude of the effect of the present invention can be understood.

  Moreover, although the output increase rate of Example 12 with respect to Comparative Example 13 is 20.8%, the output improvement rate with respect to Comparative Example 1 of Example 1 in which the battery structure is different although the same material is used is 26.4% It can be seen that the structure of the battery affects the magnitude of the effect of the non-aqueous electrolyte solution of the present invention. That is, the effect of the present invention is particularly great for high capacity batteries and batteries with small DC resistance.

  Furthermore, although not described in the table, in the case of using an electrolytic solution having an EC content of less than 1% by volume, the initial capacity is slightly lower than in Example 1, and the output characteristics and cycle characteristics at normal temperature are It was inferior to.

  As described above, the nonaqueous electrolytic solution of the present invention, that is, a mixed solvent containing at least ethylene carbonate, wherein the ratio of ethylene carbonate to the total amount of nonaqueous solvents is 1% by volume or more and 25% by volume or less Cyclic siloxane compound represented by the general formula (1), fluorosilane compound represented by the general formula (2), compound represented by the general formula (3), compound having S-F bond in the molecule, nitrate Characterized in that at least one or more compounds selected from the group consisting of nitrite, monofluorophosphate, difluorophosphate, acetate and propionate are contained in an amount of 10 ppm or more in the whole non-aqueous electrolytic solution By using the non-aqueous electrolyte solution for secondary batteries, it has become possible to exhibit very large low-temperature output characteristics.

  Furthermore, the effect can be more remarkably exhibited in the battery structure as in Example 1, that is, in the high capacity battery and the battery with small DC resistance, as compared with the battery structure as in Example 12. The

  The applications of the non-aqueous electrolyte solution for a secondary battery of the present invention and the non-aqueous electrolyte secondary battery are not particularly limited, and can be used for various known applications. Examples include laptops, pen-based PCs, mobile PCs, e-book players, mobile phones, mobile faxes, mobile copying, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini discs, transceivers , Electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorbikes, motorbikes, bicycles, lighting fixtures, toys, game machines, watches, electric tools, strobes, cameras, etc. Can. In particular, since the non-aqueous electrolyte secondary battery of the present invention has good cycle characteristics and high low-temperature characteristics, it is particularly effective when used in applications where the temperature difference is severe. It is widely used in such a field.

Claims (5)

  In the non-aqueous electrolyte solution for a secondary battery comprising a non-aqueous solvent and a lithium salt, the non-aqueous solvent is a mixed solvent containing at least ethylene carbonate and linear carbonates, and ethylene carbonate relative to the total amount of non-aqueous solvent. The total content of ethylene carbonate and linear carbonates in the non-aqueous solvent is 80% by volume or more, and the S--F bond in the molecule is more than 1% by volume and 25% by volume or less. And a compound having sulfonyl fluorides or fluorosulfonic acid esters in a total amount of 10 ppm or more and 5% by mass or less in total of the non-aqueous electrolytic solution, or a secondary Nonaqueous electrolyte for batteries.   The nonaqueous electrolytic solution for a secondary battery according to claim 1, wherein the ratio of ethylene carbonate to the total amount of the nonaqueous solvent is 20% by volume or less.   The nonaqueous electrolytic solution for a secondary battery according to claim 1 or 2, wherein the ratio of ethylene carbonate to the total amount of the nonaqueous solvent is 15% by volume or less.   A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte solution, a negative electrode capable of inserting and extracting lithium ions, and a positive electrode, wherein the non-aqueous electrolyte solution is any one of claims 1 to 3. A non-aqueous electrolyte secondary battery characterized by being a non-aqueous electrolyte for a secondary battery. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte solution, a negative electrode capable of inserting and extracting lithium ions, and a positive electrode, wherein the non-aqueous electrolyte solution is any one of claims 1 to 4. 3. A non-aqueous electrolyte secondary battery comprising: a non-aqueous electrolyte for a secondary battery, and having the following properties (1), (2) and / or (3):
(1) The sum of the electrode area of the positive electrode and the surface area of the exterior of the secondary battery is 20 times or more in area ratio.
(2) The DC resistance component of the secondary battery is 10 milliohms (mΩ) or less.
(3) The electric capacity of the battery element housed in one battery outer case of the secondary battery is 3 amperes-hour (Ah) or more.