JP2007220670A - Lithium-ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery that has a combination of a superior life and a high output. <P>SOLUTION: The lithium ion secondary battery has a non-aqueous electrolytic solution which contains compounds expressed by formulae (1), (2), (3), compounds having S-F bond in the molecule, nitrate, nitrite, mono-fluoro-phosphoric acid salt, di-fluoro-phosphoric acid salt, acetate, and/or propionate, and a negative electrode which has a negative electrode active material that has a tap density of 0.1 g/cm<SP>3</SP>or more, and pore volume of 0.01 mL/g or more, or a negative electrode that has a reaction resistance of 500 Ω or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lithium ion secondary battery, and more particularly to a lithium ion secondary battery using a specific non-aqueous electrolyte and a specific negative electrode.

  In the fields of information-related equipment and communication equipment, along with the downsizing of personal computers, video cameras, mobile phones, etc., lithium-ion secondary batteries have been put to practical use because of their high energy density as the power source used for these equipment. It has become widespread.

  In recent years, in addition to the above fields, in the field of automobiles, lithium ion secondary batteries have been developed mainly for use as power sources for electric vehicles, which are urgently developed against the background of environmental and resource problems. Is being considered.

  Among lithium secondary batteries, secondary batteries using metal lithium as a negative electrode have been actively studied since long ago as batteries capable of achieving high capacity. However, these batteries have a problem that metallic lithium grows in a dendrite shape by repeated charging and discharging, eventually reaches the positive electrode, and a short circuit occurs inside the battery, and this problem is a metallic lithium secondary battery. Has become the biggest technical challenge when putting to practical use.

  Therefore, a nonaqueous electrolyte secondary battery using a carbonaceous material capable of occluding and releasing lithium ions such as coke, artificial graphite, and natural graphite has been proposed for the negative electrode. In such a non-aqueous electrolyte secondary battery, since lithium does not exist in a metal state, formation of dendrites is suppressed, and battery life and safety can be improved. In particular, graphite-based carbonaceous materials such as artificial graphite and natural graphite are expected as materials capable of improving the energy density per unit volume.

  However, lithium primary batteries are generally preferred as non-aqueous electrolyte secondary batteries using various graphite-based electrode materials alone or mixed with other negative electrode materials capable of occluding and releasing lithium as negative electrodes. When a non-aqueous electrolyte containing propylene carbonate used as a main solvent is used, the decomposition reaction of the solvent proceeds vigorously on the surface of the graphite electrode, making it impossible to smoothly occlude and release lithium into the graphite electrode. On the other hand, ethylene carbonate is often used as the main solvent of the electrolyte of non-aqueous electrolyte secondary batteries because of such a small amount of decomposition. However, even when ethylene carbonate is used as the main solvent, the surface of the electrode is charged and discharged. Since the electrolytic solution is decomposed, there is a problem that the charge / discharge efficiency and the cycle maintenance ratio are reduced.

  Although it is mainly used with a comparatively small battery such as a cellular phone which has been used so far, it is expected that a lithium ion secondary battery will be further used as a power source for electric vehicles in the future. In such a large battery, output and life are particularly required, and simply increasing the size of a conventional small battery is not sufficient as performance.

  Thus, as a means for improving the input / output characteristics of a lithium ion secondary battery, many techniques have been studied for various battery components including positive and negative active materials.

  As a technique related to the negative electrode active material, a method of changing the configuration of the negative electrode has been studied. For example, in Patent Document 1, by using a negative electrode active material in which only the vicinity of the surface is a low crystalline carbonaceous carbon material and the inside thereof is crystalline graphite, the relative discharge capacity is hardly reduced even at high temperatures. Although there is a description of a lithium ion secondary battery having an excellent cycle maintenance rate, even if this method is used, the cycle maintenance rate that is the capacity after the charge / discharge cycle test with respect to the initial capacity and the output after the cycle test are sufficient. I could not say.

  As a technique related to the non-aqueous electrolyte solution, Patent Document 2 discloses that in a non-aqueous electrolyte secondary battery, when lithium monofluorophosphate or lithium difluorophosphate is added to the non-aqueous electrolyte solution, a good film is formed at the electrode interface. As a result, it is described that the decomposition of the electrolytic solution is suppressed and a battery having improved storage characteristics can be obtained.

However, even with these methods, the cycle retention rate and the output after the cycle were not sufficient.
WO2003 / 034518 Japanese Patent Application Laid-Open No. 11-067270

  This invention is made | formed in view of this background art, The subject is providing the lithium ion secondary battery which had favorable lifetime and high output, even when a battery was enlarged. is there.

  As a result of intensive studies in view of the above problems, the present inventor has a negative electrode containing a specific compound in a non-aqueous electrolyte and a negative electrode active material having specific physical properties and / or specific physical properties. By using the negative electrode, the present inventors have found that a lithium ion secondary battery having a good life and high output can be obtained even when the battery is made larger, and the present invention has been completed.

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

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

［一般式（３）中、Ｒ^６〜Ｒ^８は互いに同一であっても異なっていてもよい炭素数１〜１２の有機基を表し、ＡはＨ、Ｃ、Ｎ、Ｏ、Ｆ、Ｓ、Ｓｉ及び／又はＰから構成される基を表す。］ That is, the present invention is a lithium ion secondary battery having a nonaqueous electrolytic solution containing a nonaqueous solvent and a lithium salt, a positive electrode containing a positive electrode active material, and a negative electrode containing a negative electrode active material, the nonaqueous electrolyte The liquid is a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), a compound having an SF bond in the molecule. Containing at least 10 ppm of at least one compound selected from the group consisting of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate in the whole non-aqueous electrolyte , and the and the negative electrode, a tap density of 0.1 g / cm ³ or more and, in the mercury porosimetry, the pore volume of the particles corresponding to the range of diameters 0.01Myuemu～1myuemu 0.01 m There is provided a lithium ion secondary battery, characterized in that those containing a negative electrode active material is / g or more (embodiment A).

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

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

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

  The present invention also relates to a lithium ion secondary battery having a nonaqueous electrolyte containing a nonaqueous solvent and a lithium salt, a positive electrode containing a positive electrode active material, and a negative electrode containing a negative electrode active material, the nonaqueous electrolyte solution Is a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), a compound having an SF bond in the molecule, It contains at least 10 ppm of at least one compound selected from the group consisting of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate in the whole non-aqueous electrolyte. In addition, the present invention provides a lithium ion secondary battery characterized in that the reaction resistance of the negative electrode facing cell when charged to 60% of the nominal capacity of the negative electrode is 500Ω or less ( Like B).

  According to the present invention, even if the battery is made larger, the cycle retention rate is large, a good battery life can be achieved, a high output can be achieved even after the charge / discharge cycle test, and a lithium ion secondary that combines both A battery can be provided. In the present invention, the “cycle maintenance ratio” is defined as the value measured by the method described in the examples.

  Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these specific contents. However, various modifications can be made within the scope of the gist.

The present invention comprises the above (Aspect A) and (Aspect B). Aspect A defines the negative electrode used in the present invention by the physical properties of the negative electrode active material, and Aspect B defines the negative electrode used in the present invention by the configuration or physical properties of the negative electrode itself. Compared to the prior art, it has the same technical feature that “the good life and high output are improved at the same time even if it is large”.
(Aspect A) A lithium ion secondary battery having a non-aqueous electrolyte solution containing a specific compound and a negative electrode containing a negative electrode active material having specific physical properties.
(Aspect B) A lithium ion secondary battery having a nonaqueous electrolytic solution containing a specific compound and a negative electrode having a specific configuration or physical properties.

<Non-aqueous electrolyte>
The non-aqueous electrolyte used for the lithium ion secondary battery of the present invention contains at least a lithium salt and a non-aqueous solvent that dissolves the lithium salt. The following description regarding the non-aqueous electrolyte is common to the aspects A and B of the present invention.

[Lithium salt]
The lithium salt is not particularly limited as long as it is known to be used as an electrolyte of a non-aqueous electrolyte solution for a lithium ion secondary battery, and examples thereof include the following.

Inorganic lithium salt:
Inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ ; perhalogenates such as LiClO ₄ , LiBrO ₄ , LiIO ₄ ; inorganic chloride salts such as LiAlCl ₄ .
Fluorine-containing organic lithium salt:
Perfluoroalkane sulfonates 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 salt; Perfluoroalkanesulfonylmethide salt 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 ].
Oxalatoborate salt:
Lithium difluorooxalatoborate, lithium bis (oxalato) borate and the like.

These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. Among these, when comprehensively judging solubility in a non-aqueous solvent, charge / discharge characteristics in the case of a secondary battery, output characteristics, cycle maintenance ratio, etc., LiPF ₆ , LiBF _{4 and the} like are preferable, and LiPF ₆ is particularly preferable. preferable.

  The concentration of the lithium salt in the nonaqueous electrolytic solution is not particularly limited, but is usually 0.3 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.7 mol / L or more. Moreover, the upper limit is 2 mol / L or less normally, Preferably it is 1.8 mol / L or less, More preferably, it is 1.7 mol / L or less. If the concentration is too low, the electrical conductivity of the non-aqueous electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity. Performance may be degraded.

  The non-aqueous electrolyte preferably contains a fluorine-containing lithium salt as the lithium salt, and the concentration of the fluorine-containing lithium salt in the non-aqueous electrolyte is not particularly limited, but is 0.5 mol / L or more. The amount is particularly preferably 0.7 mol / L or more. Moreover, the upper limit is preferably 2 mol / L or less, particularly preferably 1.7 mol / L or less. If the concentration is too low, the electrical conductivity of the non-aqueous electrolyte solution may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity decreases due to an increase in viscosity, and the performance of the lithium ion secondary battery May decrease.

Lithium salts may be used singly or in combination of two or more in any combination and ratio. Preferred examples when two or more lithium salts are used are LiPF ₆ and LiBF _4. In this case, the proportion of LiBF _{4 in} the total of both is particularly preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 5% by mass. More preferably, it is as follows. Another preferred example is the combined use of an inorganic fluoride salt and a perfluoroalkanesulfonylimide salt. In this case, the proportion of the inorganic fluoride salt in the total of both is 70% by mass or more and 99% by mass. % Or less, particularly preferably 80% by mass or more and 98% by mass or less. The combined use of both has the effect of suppressing deterioration due to high temperature storage.

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

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

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

  Specific examples of preferred combinations of cyclic carbonates and chain carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination. In the case of 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.

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

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

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

[Specific compounds]
The non-aqueous electrolyte used for the lithium ion secondary battery of the present invention is represented by the cyclic siloxane compound represented by the general formula (1), the fluorosilane compound represented by the general formula (2), and the general formula (3). A compound having an SF bond in the molecule, at least one compound selected from the group consisting of nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate, and propionate (Hereinafter, these may be abbreviated as “specific compounds”) 10 ppm or more is essential.

  By combining a non-aqueous electrolyte containing such a specific compound with a negative electrode containing a negative electrode active material having specific physical properties, which will be described later as a negative electrode active material, and / or a negative electrode having specific physical properties or composition, A lithium ion secondary battery having both life and high output can be provided.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  The ratio of these specific compounds in the non-aqueous electrolyte solution is essential to be 10 ppm or more (0.001 mass% or more) in total with respect to the total non-aqueous electrolyte solution, but is preferably 0.01 mass% or more. Preferably it is 0.05 mass% or more, More preferably, it is 0.1 mass% or more. The upper limit is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less. If the concentration of the specific compound is too low, the cycle retention rate, which is the ratio of the capacity after the charge / discharge cycle test to the initial capacity, may be small when the battery is enlarged (the battery life may be shortened). ) High output may not be obtained after cycle test. On the other hand, if the concentration is too high, the charge / discharge efficiency may be reduced.

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

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

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

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

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

<Negative electrode>
Below, the negative electrode used for the lithium ion secondary battery of this invention is demonstrated.

<< About Aspect A >>
Aspect A of the present invention defines the negative electrode used in the present invention in terms of the physical properties of the negative electrode active material contained therein. The non-aqueous electrolyte solution containing the above specific compound and the following specific physical properties The present invention relates to a lithium ion secondary battery having a negative electrode containing the negative electrode active material. Hereinafter, embodiment A of the present invention will be described.

[Negative electrode active material]
In the aspect A of the present invention, as the negative electrode active material contained in the negative electrode, a material capable of electrochemically occluding and releasing lithium ions is used, and at least the following requirements (a) and (b) It is essential to satisfy.
(A) The tap density is 0.1 g / cm ³ or more.
(B) The pore volume in the range of 0.01 μm to 1 μm in mercury porosimetry is 0.01 mL / g or more.

[[Tap density]]
The tap density of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is preferably 0.1 g / cm ³ or more, more preferably 0.5 g / cm ³ or more, and still more preferably 0.7 g / cm. cm ³ or more, particularly preferably 0.9 g / cm ³ or more. The upper limit is preferably 2 g / cm ³ or less, more preferably 1.8 g / cm ³ or less, and particularly preferably 1.6 g / cm ³ or less. When the tap density is below this range, a high output effect cannot be achieved. On the other hand, if this range is exceeded, the voids between the particles in the electrode may become too small, and the output itself may decrease due to a decrease in the flow path of the non-aqueous electrolyte.

In the present invention, the tap density is measured by passing a sieve having a mesh size of 300 μm, dropping the sample onto a 20 cm ³ tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, Seishin Enterprise Co., Ltd.). Using a tap denser), tapping with a stroke length of 10 mm is performed 1000 times, the density is calculated from the volume and weight at that time, and defined as the tap density.

[[Pore volume]]
The pore volume of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is a void or particle in a particle corresponding to a diameter of 0.01 μm or more and 1 μm or less determined by mercury porosimetry (mercury intrusion method). The amount of irregularities due to surface steps (hereinafter abbreviated as “pore volume”) is 0.01 mL / g or more, preferably 0.05 mL / g or more, more preferably 0.1 mL / g or more, and 0 as the upper limit. 0.6 mL / g or less, preferably 0.4 mL / g or less, more preferably 0.3 mL / g or less. If it exceeds this range, a large amount of binder may be required when forming an electrode plate. On the other hand, below this range, long life and high output cannot be achieved.

  The total pore volume 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, and the upper limit is usually 10 mL / g or less, preferably 5 mL. / G or less, more preferably 2 mL / g or less. If this range is exceeded, a large amount of binder may be required during electrode plate formation. If it is less than that, it may not be possible to obtain the effect of dispersing the thickener or the binder during the electrode plate formation. Here, the “total pore volume” refers to the sum of the pore volumes measured over the entire range under the following measurement conditions.

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

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

  The lithium ion secondary battery of aspect A of the present invention can exhibit the above-described effects of the present invention as long as the negative electrode active material satisfies the above requirements (a) and (b). However, it is preferable that the negative electrode active material simultaneously satisfies one or more of the following physical properties. In addition, regarding the negative electrode, it is particularly preferable that any one or a plurality of terms of the physical properties or the configuration of the negative electrode in aspect B to be described later is simultaneously satisfied.

[[BET specific surface area]]
Anode active BET method specific surface area measured by using the material contained in the negative electrode of a lithium ion secondary battery of the present invention is preferably 0.1 m ² / g or more, particularly preferably 0.7 m ² / g or more, more preferably 1 m ² / g or more, still more preferably 1.5 m ² / g or more. The upper limit is preferably 100 m ² / g or less, particularly preferably 50 m ² / g or less, more preferably 25 m ² / g or less, and further preferably 15 m ² / g or less. If the value of the BET specific surface area is less than this range, the acceptability of lithium is likely to deteriorate during charging when used as a negative electrode material, lithium may easily precipitate on the electrode surface, or high output may not be obtained. is there. On the other hand, if it exceeds this range, when used as a negative electrode material, the reactivity with the non-aqueous electrolyte increases, gas generation tends to increase, and a preferable battery may be difficult to obtain.

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

[[Volume average particle size]]
The volume average particle diameter of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is defined by a volume-based average particle diameter (median diameter) determined by a laser diffraction / scattering method, and is preferably 1 μm or more. Particularly preferably, it is 3 μm or more, more preferably 5 μm or more, and further preferably 7 μm or more. Moreover, an upper limit is 50 micrometers or less normally, Preferably it is 40 micrometers or less, More preferably, it is 30 micrometers or less, More preferably, it is 25 micrometers or less. If it falls below the above range, the irreversible capacity may increase, leading to loss of the initial battery capacity. On the other hand, if the ratio exceeds the above range, a non-uniform coating surface tends to be formed at the time of forming an electrode plate, which may be undesirable in the battery manufacturing process.

  In the present invention, the volume-based average particle size is determined by dispersing carbon powder in a 0.2% by mass aqueous solution (about 1 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and a laser diffraction particle size distribution analyzer. It is defined by the median diameter measured using (for example, LA-700 manufactured by Horiba, Ltd.).

[[Circularity]]
The circularity of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is usually 0.1 or more, preferably 0.5 or more, particularly preferably 0.8 or more, more preferably 0.85 or more, Especially preferably, it is 0.9 or more. The upper limit is a theoretical sphere when the circularity is 1. Below this range, problems such as streaking may occur during electrode formation.

The circularity referred to in the present invention is defined by the following equation.
Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  As the circularity value, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) was used, and about 0.2 g of a sample was added to a polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, in an amount of 0. Dispersed in a 2% by weight aqueous solution (about 50 mL), irradiated with 28 kHz ultrasonic waves at 60 W output for 1 minute, specified a detection range of 0.6 to 400 μm, and measured particles with a particle size in the range of 3 to 40 μm Use the value obtained.

[[Surface spacing (d002)]]
The interplanar spacing (d002) of the (002) plane by the wide-angle X-ray diffraction method of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is usually 0.38 nm or less, preferably 0.36 nm or less. It is preferably 0.35 nm or less, more preferably 0.345 nm or less, and the lower limit is 0.335 nm or more, which is the theoretical value of graphite. Beyond this range, crystallinity may be significantly reduced and irreversible capacity may increase.

  In the present invention, the (002) plane spacing (d002) by the wide angle X-ray diffraction method is the d value (interlayer distance) of the lattice plane (002 plane) obtained by the X-ray diffraction by the Gakushin method.

[[Crystallite size (Lc)]]
The crystallite size (Lc) of the negative electrode active material determined by X-ray diffraction by the Gakushin method is not particularly limited, but is usually 0.1 nm or more, preferably 0.5 nm or more, more preferably 1 nm or more. is there. Below this range, crystallinity may be significantly reduced and irreversible capacity may increase.

[[True density]]
The true density of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is usually 1.5 g / cm ³ or more, preferably 1.7 g / cm ³ or more, more preferably 1.8 g / cm ^3. or more, more preferably 1.85 g / cm ³ or more, the upper limit is 2.26 g / cm ³ or less. The upper limit is the theoretical value of graphite. Below this range, the crystallinity of the carbon is too low and the irreversible capacity may increase.
In the present invention, the true density is defined by a value measured by a liquid phase substitution method (pycnometer method) using butanol.

[[Raman R value]]
The Raman R value of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is usually 0.01 or higher, preferably 0.03 or higher, more preferably 0.1 or higher. As an upper limit, Preferably it is 1.5 or less, Especially preferably, it is 1.2 or less, More preferably, it is 0.5 or less. If the Raman R value is below this range, the crystallinity of the particle surface becomes too high, and the output itself may decrease as the charge / discharge sites decrease. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, and the irreversible capacity may increase.

The Raman spectrum is measured using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation), and the sample is naturally dropped into the measurement cell, and the sample is filled with argon ion laser light on the sample surface in the cell. , While rotating the cell in a plane perpendicular to the laser beam. The obtained Raman spectrum, the intensity I _A of the peak P _A in the 1580 cm ^-1, and measuring the intensity I _B of a peak P _B of 1360 cm ^-1, the intensity ratio R of the (R = I _B / I _A) This is calculated and defined as the Raman R value of the negative electrode active material. Further, the half width of the peak P _{A at} 1580 cm ⁻¹ of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the negative electrode active material.

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

Moreover, the Raman half-value width of 1580 cm ⁻¹ of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, Usually, it is 150 cm ⁻¹ or less, preferably 100 cm ⁻¹ or less, more preferably 60 cm ⁻¹ or less. When the Raman half width is less than this range, the crystallinity of the particle surface becomes too high, and the output itself may decrease as the charge / discharge sites decrease. On the other hand, if it exceeds this range, the crystallinity of the particle surface will decrease, and the irreversible capacity may increase.

[[ash]]
The ash content of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is preferably 1% by mass or less, particularly preferably 0.5% by mass or less, and further preferably 0.1% by mass or less. Moreover, as a minimum, it is preferable that it is 1 ppm or more. When the above range is exceeded, deterioration in battery performance due to reaction with the non-aqueous electrolyte during charge / discharge cannot be ignored, and the cycle maintenance ratio may be reduced. On the other hand, if it falls below this range, a great amount of time, energy and equipment for preventing contamination may be required for production, which may increase costs.

[[aspect ratio]]
The aspect ratio of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is theoretically 1 or more, and the upper limit is usually 10 or less, preferably 8 or less, more preferably 5 or less. If the upper limit is exceeded, streaking of the active material during the production of the negative electrode or a uniform coated surface may not be obtained, and the high current density charge / discharge characteristics may deteriorate.

  The aspect ratio is expressed as A / B when the diameter is the longest diameter A when observed three-dimensionally and the shortest diameter B is perpendicular to the diameter. The particles are observed with a scanning electron microscope capable of magnifying observation. Select 50 arbitrary particles fixed to the end face of a metal with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed, measure A and B, and average A / B Ask for.

[[Orientation ratio]]
The orientation ratio of the negative electrode active material contained in the negative electrode of the lithium ion secondary battery of the present invention is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and the upper limit is theoretically 0.67 or less. Below this range, the high-density charge / discharge characteristics may deteriorate.

  The orientation ratio is measured by X-ray diffraction. The peaks of (110) and (004) diffraction are integrated by fitting the peaks of (110) and (004) diffraction of carbon by X-ray diffraction using asymmetric Pearson VII as a profile function. Each intensity is calculated. From the obtained integrated intensity, a ratio represented by (110) integrated diffraction intensity / (004) integrated diffraction intensity is calculated and defined as the orientation ratio of the negative electrode active material.

The X-ray diffraction measurement conditions here are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree ・ Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds (004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds

<< About Aspect B >>
Aspect B of the present invention defines the negative electrode used in the present invention by the physical properties and / or configuration of the negative electrode itself, and includes a non-aqueous electrolyte solution containing the above specific compound, the following specific physical properties and / or Alternatively, the present invention relates to a lithium ion secondary battery having a negative electrode having a configuration. Hereinafter, aspect B of the present invention will be described.

[Physical properties and structure of negative electrode]
Below, the physical property and structure of the negative electrode used for the lithium ion secondary battery of aspect B are demonstrated. The negative electrode has a negative electrode active material layer on a current collector.

[[Reaction resistance]]
The reaction resistance of the negative electrode used in the embodiment B of the present invention, which is obtained by measuring the opposing impedance, is essentially 500Ω or less, preferably 100Ω or less, more preferably 50Ω or less. There is no particular lower limit. When exceeding this range, when it is set as a lithium ion secondary battery, the output characteristic before and after a cycle test will fall. In addition, the cycle maintenance ratio may decrease due to the high resistance.

  A method for measuring the counter impedance is described below. In general, when measuring the impedance of a lithium ion secondary battery, an AC impedance measurement is performed between the positive electrode terminal and the negative electrode terminal of the battery. It cannot be uniquely determined whether it is due to positive or negative polarity. Therefore, in the present invention, the reaction resistance due to the counter cell with only the negative electrode is measured. The method for measuring reaction resistance in the present invention will be described below.

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

  The lithium ion secondary battery of aspect B of the present invention can exhibit the above-described effects of the present invention and exhibit sufficient performance as long as the reaction resistance of the negative electrode facing the negative cell satisfies the above requirements. However, it is preferable that one or more of the following physical properties or configurations of the negative electrode are simultaneously satisfied. Further, it is particularly preferable that the negative electrode active material also satisfies any one or more of the physical properties of the negative electrode active material described in the section of the embodiment A at the same time.

[[Double layer capacity (Cdl)]]
The double layer capacity (Cdl) obtained by measuring the opposing impedance of the negative electrode used in the present invention is preferably 1 × 10 ⁻⁶ F or more, particularly preferably 1 × 10 ⁻⁵ F or more, more preferably 3 × 10. ^-5 F or more. Below this range, the area that can be reacted decreases, and as a result, the output may decrease.

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

  The ratio of the binder to the whole negative electrode active material layer is usually 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 usually 20% by mass or less. Preferably it is 15 mass% or less, More preferably, it is 10 mass% or less, More preferably, it is the range of 8 mass% or less. If it exceeds this range, the proportion of the binder that does not contribute to the battery capacity will increase, so the battery capacity may be reduced, or the surface of the negative electrode active material may be covered with the binder, and high output may not be obtained. On the other hand, if it is less, the strength of the negative electrode is reduced, which may be undesirable in the battery production process. In particular, when the main component contains a rubbery polymer typified by SBR, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably The upper limit is usually 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 typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more. The upper limit is usually 15% by mass or less, preferably 10% by mass or less, more preferably 8% by mass or less.

[[Electrode production]]
The negative electrode may be manufactured by a conventional method. For example, a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc., are added to the negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed to obtain a negative electrode active material. A material layer can be formed. The thickness of the negative electrode active material layer per side in the stage immediately before the electrolyte solution 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 150 μm or less, preferably 120 μm or less. More preferably, it is 100 μm or less. If it exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may deteriorate. On the other hand, below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Alternatively, 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.

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

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

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

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

Moreover, the following physical properties are desired for the current collector.
(1) Average surface roughness (Ra)
The average surface roughness (Ra) of the negative electrode active material thin film forming surface of the current collector defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.01 μm or more, preferably 0.03 μm or more, usually It is 1.5 μm or less, preferably 1.3 μm or less, particularly preferably 1.0 μm or less. By setting the average surface roughness (Ra) of the current collector within the range between the lower limit and the upper limit, a good cycle maintenance rate can be expected. By setting it to the above lower limit or more, the area of the interface with the negative electrode active material thin film is increased, and the adhesion with the negative electrode active material thin film is improved. 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. There is a case.

(2) Tensile strength The tensile strength of the current collector is not particularly limited, but is usually 50 N / mm ² or more, preferably 100 N / mm ² or more, more preferably 150 N / mm ² or more. The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same apparatus and method as the elongation rate. If the current collector has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and a good cycle retention rate can be obtained.

(3) 0.2% proof stress of 0.2% proof stress current collector is not particularly limited, normally 30 N / mm ² or more, preferably 100 N / mm ² or more, particularly preferably 150 N / mm ² or more. The 0.2% proof stress is the magnitude of the load necessary to give a plastic (permanent) strain of 0.2%. It means that The 0.2% proof stress in the present invention is measured by the same apparatus and method as the elongation rate. If the current collector has a high 0.2% proof stress, plastic deformation of the current collector due to expansion / contraction of the negative electrode active material thin film accompanying charging / discharging can be suppressed, and a good cycle retention rate can be obtained. it can. Although the thickness of a metal thin film is arbitrary, it is 1 micrometer or more normally, Preferably it is 3 micrometers or more, More preferably, it is 5 micrometers or more. Moreover, an upper limit is 1 mm or less normally, Preferably it is 100 micrometers or less, More preferably, it is 30 micrometers or less. If the thickness is less than 1 μm, the strength may be reduced, and application may be difficult. If it is thicker than 100 μm, it may be difficult to deform it into a desired electrode shape by winding or the like. The metal thin film may be mesh.

[[Ratio of current collector to negative electrode active material layer thickness]]
Ratio of the thickness of the current collector and the negative electrode active material layer (thickness of the negative electrode active material layer on one side immediately before the nonaqueous electrolyte injection), that is, [(thickness of negative electrode active material layer on one side) / (collection The thickness of the electric body)] is usually 150 or less, preferably 20 or less, more preferably 10 or less, and the lower limit is usually 0.1 or more, preferably 0.4 or more, more preferably 1 or more. It is a range. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the negative electrode active material increases and the battery capacity may decrease.

[[Negative electrode active material layer density]]
The density of the negative electrode active material layer when the negative electrode active material is converted into an electrode is preferably 1 g / cm ³ or more, more preferably 1.2 g / cm ³ or more, and further preferably 1.3 g / cm ³ or more. as is usually 2 g / cm ³ or less, preferably 1.85 g / cm ³ or less, more preferably 1.8 g / cm ³ or less, more preferably 1.7 g / cm ³ or less. If it exceeds this range, the negative electrode active material particles are destroyed, the initial irreversible capacity is increased, the permeability of the non-aqueous electrolyte solution near the current collector / negative electrode active material interface is lowered, and the output may be lowered. On the other hand, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

[[Plate orientation ratio]]
The electrode plate orientation ratio is usually 0.001 or more, preferably 0.005 or more, more preferably 0.01 or more, and the upper limit is 0.67 or less, which is a theoretical value. Below this range, the output may decrease.

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

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

<Positive electrode>
The positive electrode used for the lithium ion secondary battery of this invention is demonstrated below. The following description is common to Aspects A and B of the present invention.

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

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

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

[[Surface coating]]
In addition, a material in which a material having a composition different from that of the material constituting the positive electrode active material is attached to the surface of the positive electrode active material can be used. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

  These surface adhering substances are, for example, a method of dissolving or suspending in a solvent and impregnating and drying the positive electrode active material, and a method of dissolving or suspending a surface adhering substance precursor in a solvent and impregnating and adding to the positive electrode active material, followed by heating. It can be made to adhere to the positive electrode active material surface by the method of making it react by the method etc., the method of adding to a positive electrode active material precursor, and baking simultaneously. In addition, when attaching carbon, the method of attaching carbonaceous material later, for example in the form of activated carbon etc. can also be used.

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

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

[[[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. . If the tap density of the positive electrode active material is lower than the lower limit, the amount of the required dispersion medium increases when the positive electrode active material layer is formed, and the necessary amount of the conductive material and the binder increases. In some cases, the filling rate of the substance is limited, and the battery capacity is limited. By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as large as possible, but there is no particular upper limit. However, if the tap density is too large, diffusion of lithium ions using the non-aqueous electrolyte solution as a medium in the positive electrode active material layer becomes rate-determining, and load characteristics may be likely to deteriorate. Usually, it is 2.5 g / cm ³ or less, preferably 2.4 g / cm ³ or less. The tap density of the positive electrode active material is also measured and defined by the same method as that described in the section of the negative electrode active material.

[[[Median diameter d ₅₀ ]]]
The median diameter d _{50 of the} particles (when the 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. If the lower limit is not reached, a high tap density product may not be obtained. If the upper limit is exceeded, it takes time for the diffusion of lithium in the particles. When an active material, a conductive material, a binder, or the like is slurried with a solvent and applied as a thin film, problems such as streaking may occur. Here, by mixing two or more types of positive electrode active materials having different median diameters d ₅₀ , the filling property at the time of forming the positive electrode can be further improved.

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

[[[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, more preferably 0.08 μm or more, Most preferably, it is 0.1 μm or more, and the upper limit is usually 3 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and most preferably 0.6 μm or less. When the above upper limit is exceeded, it is difficult to form spherical secondary particles, which adversely affects the powder filling property, or the BET specific surface area is greatly reduced, so that there is a high possibility that the battery performance such as output characteristics will deteriorate. There is. On the other hand, when the value falls below the lower limit, there is a case where problems such as inferior reversibility of charge / discharge are usually caused because crystals are not developed.

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

[[[BET specific surface area]]]
The BET specific surface area of the positive electrode active material used for 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 .0m ² / g or less, preferably 2.5 m ² / g or less, still more preferably not more than 1.5 m ² / g. If the BET specific surface area is smaller than this range, the battery performance tends to be lowered, and if the BET specific surface area is larger, the tap density is difficult to increase, and there may be a problem in applicability when forming the positive electrode active material.

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

[[[Production method of positive electrode active material]]]
As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. Various methods are conceivable in particular for producing a spherical or elliptical positive electrode active material. For example, a transition metal source material such as transition metal nitrate or transition metal sulfate, and a source material of other elements as required. It is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , LiNO ₃ A method of obtaining a positive electrode active material by adding a Li source such as, a transition metal source material such as transition metal nitrate, transition metal sulfate, transition metal hydroxide, transition metal oxide, etc. The raw material of the element is dissolved or pulverized and dispersed in a solvent such as water, and then dried and molded with a spray drier or the like to obtain a spherical or elliptical precursor, and LiOH, Li ₂ CO ₃ , LiNO _3, etc. Add Li source And a method of obtaining a positive electrode active material by baking at a high temperature, and transition metal raw materials such as transition metal nitrates, transition metal sulfates, transition metal hydroxides, transition metal oxides, and LiOH, Li ₂ CO ₃ , LiNO Li source such as ₃ and raw materials of other elements as necessary are dissolved or pulverized and dispersed in a solvent such as water, and then dried and molded with a spray dryer or the like to form a spherical or elliptical precursor, Examples thereof include a method of firing this at a high temperature to obtain a positive electrode active material.

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

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

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

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

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

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

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

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

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

[[[Consolidation]]]
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. Density of the positive electrode active material layer, preferably as a lower limit 1.5 g / cm ³ or more, more preferably 2 g / cm ³ or more, still more preferably 2.2 g / cm ³ or more, the upper limit is preferably 3. The range is 5 g / cm ³ or less, more preferably 3 g / cm ³ or less, and still more preferably 2.8 g / cm ³ or less. If this range is exceeded, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / positive electrode active material interface may decrease, and the charge / discharge characteristics at a high current density may decrease. On the other hand, if it is lower, the conductivity between the positive electrode active materials may be lowered, and the battery resistance may be increased.

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

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

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

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

[[[Discharge capacity]]]
In the present invention, when a non-aqueous electrolyte solution containing a specific compound is used, the electric capacity (battery discharged from a fully charged state to a discharged state) of a battery element housed in one battery exterior of a lithium ion secondary battery When the electrical capacity is 3 ampere hours (Ah) or more, the contact area with the peripheral member is increased, which is preferable from the viewpoint of improving thermal conductivity. Therefore, the positive electrode plate is preferably designed so that the discharge capacity is fully charged and is 3 ampere hours (Ah) or more and 20 Ah or less, and more preferably 4 Ah or more and 10 Ah or less. If it is less than 3 Ah, the voltage drop due to the electrode reaction resistance becomes large when taking out a large current, and the power efficiency may deteriorate. If it is larger than 20 Ah, the electrode reaction resistance is reduced and the power efficiency is improved, but the temperature distribution due to the internal heat generation of the battery during pulse charge / discharge is large, the durability of repeated charge / discharge is inferior, and overcharge, internal short circuit, etc. The heat dissipation efficiency deteriorates due to sudden heat generation at the time of abnormality, and the probability that the internal pressure rises and the gas release valve operates (valve operation), and the battery contents erupt violently (explosion) increases. There is a case.

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

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

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

In the bottomed square shape, the ratio between the area S of the largest surface (the product of the width and height of the outer dimensions excluding the terminal portion, unit cm ² ) and the thickness T (unit cm) of the battery outer shape The 2S / T value is preferably 100 or more, and more preferably 200 or more. By increasing the maximum surface, it is possible to improve the cycle maintenance rate even for batteries with high output and large capacity, and increase the heat dissipation efficiency in the event of abnormal heat generation, which is a dangerous condition such as `` valve operation '' or `` rupture '' Can be suppressed.

<Battery configuration>
A chargeable / dischargeable lithium ion secondary battery according to the present invention includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, the non-aqueous electrolyte, a separator disposed between the positive electrode and the negative electrode, a current collecting terminal, and an exterior. It is configured at least by a case or the like. Further, if necessary, a protective element may be mounted inside the battery and / or outside the battery.

[Separator]
The separator used in the present invention has a predetermined mechanical strength that electrically insulates both electrodes, has a high ion permeability, and has resistance to oxidation on the side in contact with the positive electrode and reduction on the negative electrode side. There is no particular limitation as long as it has both. As a material for the separator having such required characteristics, a resin, an inorganic material, glass fiber, or the like is used. As the resin, olefin polymer, fluorine polymer, cellulose polymer, polyimide, nylon and the like are used. Specifically, it is preferable to select from materials that are stable with respect to the electrolytic solution and have excellent liquid retention properties, and it is preferable to use a porous sheet or nonwoven fabric made of a polyolefin such as polyethylene or polypropylene.

  Examples of the inorganic material include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate, and those having a particle shape or fiber shape are used. As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, it is possible to form alumina particles having a 90% particle diameter of 1 μm or less on both surfaces of the positive electrode in a porous layer using a fluororesin as a binder.

[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either may be used.

  The ratio of the volume of the electrode group to the battery internal volume (hereinafter referred to as electrode group occupancy) is preferably 40% to 90%, and more preferably 50% to 80%. When the electrode group occupancy is less than 40%, the battery capacity is small, and when it is more than 90%, the void space is small, the member expands when the battery becomes high temperature, and the vapor pressure of the liquid component of the electrolyte increases. In some cases, the internal pressure rises due to an increase in the pressure, which deteriorates various characteristics such as charge / discharge repetition performance and high-temperature storage as a battery, and further, a gas release valve that releases the internal pressure to the outside may operate.

[Current collection structure]
The current collecting structure is not particularly limited, but in order to more effectively realize the output recovery by the temperature adaptation according to the present invention, it is necessary to have a structure that reduces the resistance of the wiring portion and the junction portion. When such an internal resistance is small, the effect of using a non-aqueous electrolyte solution containing a specific compound in combination with a negative electrode active material or a negative electrode is exhibited particularly well.

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

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

  The non-aqueous electrolyte containing the specific compound used in the present invention is effective in reducing the reaction resistance related to the desorption / insertion of lithium with respect to the electrode active material, which is a factor that can realize a long life and high output. it is conceivable that. However, it was found that a battery having a large direct current resistance is inhibited by the direct current resistance, and the effect of reducing the reaction resistance cannot be reflected 100% on the cycle maintenance rate or output. This can be improved by using a battery having a small DC resistance component, and the effect of the non-aqueous electrolyte solution of the present invention can be sufficiently exhibited.

  From the viewpoint of drawing out the effect of the non-aqueous electrolyte containing the specific compound and producing a battery having a long life and high output, this requirement and the above-described secondary battery are housed in one battery exterior. It is particularly preferable to satisfy the requirement that the electric capacity of the battery element (electric capacity when the battery is discharged from the fully charged state to the discharged state) is 3 ampere hours (Ah) or more at the same time.

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

  In the exterior case using the above metals, a laser-sealed, resistance-welded, ultrasonic welding is used to weld the metals together to form a sealed sealed structure, or a caulking structure using the above-mentioned metals via a resin gasket To do.

  Examples of the outer case using the laminate film include those having a sealed and sealed structure by heat-sealing resin layers. In order to improve the sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

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

<Action and principle>
By combining “a non-aqueous electrolyte containing a specific compound” and “a negative electrode active material having a tap density of 0.1 g / cm ³ or more and a pore volume of 0.01 mL / g or more” In this case, the action / principle for obtaining a lithium ion secondary battery having a good life and high output is not clear, but the present invention is not limited by the action / principle. By using a negative electrode active material having a certain degree of micropores and a certain tap density, a flow path through which lithium ions move within the electrode plate is secured, and contains a negative electrode active material and a specific compound. It is presumed that the above-mentioned effect is exhibited by improving two points, that is, the movement of lithium ions at the interface with the non-aqueous electrolyte becomes faster. In addition, by combining the “non-aqueous electrolyte containing a specific compound” with the “negative electrode having a reaction resistance of 500 Ω or less by the opposed cell”, it has a good life and high output even when it is made large. The action / principle for obtaining a lithium ion secondary battery is not clear, but the present invention is not limited by the action / principle, but the resistance of the film produced by the reaction between the specific compound and the negative electrode is small. It is presumed that in addition to the output improvement, the high cycle resistance ratio improves the cycle maintenance ratio that has deteriorated due to the occurrence of overvoltage.

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

(Preparation of negative electrode active material 1)
Highly purified scale-like natural graphite having a median diameter of about 150 μm (d002: 0.336 nm, Lc: 100 nm or more, Raman R value: 0.11, true density: 2.27 g / cm ³ , ash content 0.05 mass %) Using a spheroidizing apparatus (hybridization system manufactured by Nara Machinery Co., Ltd.) for 5 minutes at a rotational speed of 6500 rpm, and further using a wind classifier (OMC-100 manufactured by Seishin Enterprise Co., Ltd.). 45% by mass fine powder was removed to obtain a carbonaceous material (A).

(Preparation of negative electrode active material 2)
The carbonaceous material (A) prepared in (Preparation of negative electrode active material 1) is packed in a graphite crucible and heat-treated at 3000 ° C. for 5 hours under an inert atmosphere using a direct current furnace, and the carbonaceous material (B) is subjected to heat treatment. Obtained.

(Preparation of negative electrode active material 3)
The carbonaceous material (A) prepared in (Preparation of negative electrode active material 1) is mixed with petroleum heavy oil obtained at the time of naphtha pyrolysis, carbonized at 1300 ° C. in an inert gas, and then sintered. By classifying the material, a carbonaceous material having carbonaceous materials having different crystallinity on the surface of the carbonaceous material (A) particles was obtained. In classifying treatment, in order to prevent the inclusion of coarse particles, ASTM 400 mesh sieving was repeated 5 times to obtain a carbonaceous material (C). From the residual carbon ratio, it was confirmed that the obtained negative electrode active material powder was coated with carbonaceous matter derived from 5 parts by weight of petroleum heavy oil with respect to 95 parts by weight of graphite.

(Preparation of negative electrode active material 4)
A coal tar pitch having a quinoline insoluble content of 0.05% by mass or less was heat-treated in a reaction furnace at 460 ° C. for 10 hours to obtain a meltable bulk carbonized precursor having a softening point of 385 ° C. The obtained bulk carbonized precursor was packed in a metal container and heat-treated at 1000 ° C. for 2 hours in a box-shaped electric furnace under nitrogen gas flow. The obtained amorphous mass was pulverized with a crusher (Roll jaw crusher manufactured by Yoshida Seisakusho), and further pulverized with a fine pulverizer (Turbo Mill manufactured by Matsubo) to obtain an amorphous powder having a volume standard average diameter of 17 μm. Got. In order to prevent mixing of coarse particles in the obtained powder, ASTM 400 mesh sieving was repeated 5 times. The negative electrode active material obtained here was a carbonaceous material (D).

About the produced carbonaceous material (A), carbonaceous material (B), carbonaceous material (C), and carbonaceous material (D), the shape and physical property were measured by the above-mentioned method. The results are shown in Table 1.

[Production of battery]
<< Preparation of positive electrode 1 >>
90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder, an N-methylpyrrolidone solvent Mixed in to a slurry. The obtained slurry was applied to both sides of an aluminum foil having a thickness of 15 μm, dried, and rolled to a thickness of 80 μm with a press, and the positive electrode active material layer had a size of 100 mm in width, 100 mm in length, and 30 mm in width. A positive electrode was cut out into a shape having a coating part. The density of the positive electrode active material layer of the positive electrode at this time was 2.35 g / cm ³ .

<< Preparation of negative electrode 1 >>
98 parts by weight of the negative electrode active material, 100 parts by weight of an aqueous dispersion of sodium carboxymethyl cellulose (concentration of 1% by weight of sodium carboxymethyl cellulose) as a thickener and binder, and an aqueous dispersion of styrene-butadiene rubber (styrene) -2 parts by weight of a butadiene rubber concentration of 50 mass%) was added and mixed with a disperser to form a slurry. The obtained slurry was applied to both sides of a rolled copper foil having a thickness of 10 μm as a current collector, dried, and rolled to a thickness of 75 μm with a press, and the size of the negative electrode active material layer was 104 mm wide and long. A negative electrode was cut into a shape having an uncoated part with a thickness of 104 mm and a width of 30 mm.

The density of the negative electrode active material layer of the negative electrode at this time was in the range of 1.33 to 1.36 g / cm ³ (respectively shown in the rightmost column of Table 2). From the above, the content of the styrene-butadiene rubber that is the binder of the negative electrode active material layer is 1% by mass with respect to the entire negative electrode active material layer. The value of [(thickness of negative electrode active material layer on one side) / (thickness of current collector)] is 75 μm / 10 μm = 7.5.

<< Preparation of non-aqueous electrolyte 1 >>
Under a dry argon atmosphere, a well-dried hexafluorophosphorus at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3: 3: 4) Lithium acid (LiPF ₆ ) was dissolved. Furthermore, lithium difluorophosphate (LiPO ₂ F ₂ ) was contained so as to be 0.3% by mass.

<< Preparation of non-aqueous electrolyte 2 >>
Under a dry argon atmosphere, a well-dried hexafluorophosphorus at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3: 3: 4) Lithium acid (LiPF ₆ ) was dissolved. Furthermore, trimethylsilyl methanesulfonate was contained so as to be 0.3% by mass.

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

<< Preparation of non-aqueous electrolyte solution 4 >>
Under a dry argon atmosphere, a well-dried hexafluorophosphorus at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (volume ratio 3: 3: 4) Lithium acid (LiPF ₆ ) was dissolved.

<< Production of Battery 1 >>
The 32 positive electrodes and 33 negative electrodes were alternately arranged, and the porous polyethylene sheet separator (thickness 25 μm) was laminated between each electrode. At this time, the positive electrode active material surface was faced so as not to deviate from the negative electrode active material surface. The uncoated portions of each of the positive electrode and the negative electrode were welded together to produce a current collecting tab, and an electrode group was enclosed in a battery can (outside dimension: 120 × 110 × 10 mm). Thereafter, 20 mL of a non-aqueous electrolyte solution was injected into a battery can loaded with the electrode group, sufficiently infiltrated into the electrode, and sealed to produce a prismatic battery. The rated discharge capacity of this battery is about 6 ampere hours (Ah), and the DC resistance component measured by the 10 kHz AC method is about 5 milliohms (mΩ). The ratio of the total electrode area of the positive electrode to the sum of the outer surface areas of the batteries was 20.6.

Example 1
The negative electrode prepared as the carbonaceous material (A) as the negative electrode active material in the section << Negative Electrode Preparation 1 >>, the positive electrode prepared in the section << Preparation of Positive Electrode 1 >>, A battery was prepared using the aqueous electrolyte solution by the method described in the section <Preparation of battery 1>. This battery was measured by the method described in the section <Battery evaluation> below. The results are shown in Table 2.

Example 2
A battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte solution of Example 1 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte Solution 2”. Evaluation was performed. The results are shown in Table 2.

Example 3
A battery was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte solution of Example 1 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte 3”. Evaluation was performed. The results are shown in Table 2.

Comparative Example 1
A battery was prepared in the same manner as in Example 1, except that the non-aqueous electrolyte solution of Example 1 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte Solution 4”. Evaluation was performed. The results are shown in Table 2.

Example 4
A battery was prepared in the same manner as in Example 1 except that the carbonaceous material (B) was used as the negative electrode active material in the section “Preparation of Negative Electrode 1” in Example 1, and evaluation was performed in the same manner. The results are shown in Table 2.

Example 5
A battery was prepared in the same manner as in Example 4, except that the non-aqueous electrolyte solution of Example 4 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte Solution 2”. Evaluation was performed. The results are shown in Table 2.

Example 6
A battery was prepared in the same manner as in Example 4 except that the non-aqueous electrolyte solution of Example 4 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte 3”. Evaluation was performed. The results are shown in Table 2.

Comparative Example 2
A battery was prepared in the same manner as in Example 4, except that the non-aqueous electrolyte solution of Example 4 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte Solution 4”. Evaluation was performed. The results are shown in Table 2.

Example 7
A battery was prepared in the same manner as in Example 1 except that the carbonaceous material (C) was used as the negative electrode active material in the section “Preparation of Negative Electrode 1” in Example 1, and evaluation was performed in the same manner. The results are shown in Table 2.

Example 8
A battery was prepared in the same manner as in Example 7, except that the non-aqueous electrolyte solution of Example 7 was replaced with the non-aqueous electrolyte solution prepared in the section << Preparation of Non-Aqueous Electrolyte Solution 2 >>. Evaluation was performed. The results are shown in Table 2.

Example 9
A battery was prepared in the same manner as in Example 7 except that the non-aqueous electrolyte solution of Example 7 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte 3”. Evaluation was performed. The results are shown in Table 2.

Comparative Example 3
A battery was prepared in the same manner as in Example 7 except that the non-aqueous electrolyte solution of Example 7 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte 4”. Evaluation was performed. The results are shown in Table 2.

Example 10
A battery was prepared in the same manner as in Example 1 except that the carbonaceous material (D) was used as the negative electrode active material in the section “Preparation of negative electrode 1”, and a battery was prepared in the same manner as in Example 1. Evaluation was performed. The results are shown in Table 2.

Example 11
A battery was prepared in the same manner as in Example 10 except that the non-aqueous electrolyte solution of Example 10 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte Solution 2”. Evaluation was performed. The results are shown in Table 2.

Example 12
A battery was prepared in the same manner as in Example 10 except that the non-aqueous electrolyte solution of Example 10 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte 3”. Evaluation was performed. The results are shown in Table 2.

Comparative Example 4
A battery was prepared in the same manner as in Example 10 except that the non-aqueous electrolyte solution of Example 10 was replaced with the non-aqueous electrolyte solution prepared in the section “Preparation of Non-Aqueous Electrolyte 4”. Evaluation was performed. The results are shown in Table 2.

<Battery evaluation>
(Capacity measurement)
For a battery that has not undergone a charge / discharge cycle, a voltage range of 4.2 V to 3.0 V and a current value of 0.2 C at 25 ° C. The same applies to the following, and the initial charge / discharge of 5 cycles was performed. The discharge capacity at the 5th cycle at this time was defined as the initial capacity. Next, the following output measurement was performed.

(Output measurement)
In a 25 ° C. environment, the battery is charged with a constant current of 0.2 C for 150 minutes, discharged at 0.1 C, 0.3 C, 1.0 C, 3.0 C, and 10.0 C, respectively, for 10 seconds. The voltage was measured. The area of the triangle surrounded by the current-voltage line and the lower limit voltage (3 V) was defined as output (W). The output before the cycle test was defined as “initial output”.

(Cycle test)
The cycle test was performed in a high temperature environment of 60 ° C., which is regarded as the actual use upper limit temperature of the lithium ion secondary battery. After charging with a constant current constant voltage method of 2C to a charge upper limit voltage of 4.2V, a charge / discharge cycle for discharging with a constant current of 2C to a discharge end voltage of 3.0V was defined as one cycle, and this cycle was repeated up to 500 cycles. The battery after the end of the cycle test was charged and discharged for 3 cycles under an environment of 25 ° C., and the 0.2 C discharge capacity of the third cycle was defined as the capacity after the cycle test. From the initial capacity measured prior to the cycle test and the post-cycle test capacity measured after the end of the cycle test, the cycle retention rate was determined by the following formula.
Cycle maintenance ratio (%) = 100 × capacity after cycle test / initial capacity

  For the battery after the end of the cycle test, the output measurement described in the above section (Output measurement) was performed, and the obtained value was defined as “output after cycle test”. The output measurement results, capacity measurement results, cycle maintenance ratios, and reaction resistance and double layer capacity measurement results obtained by the above-described counter impedance measurement for the lithium ion secondary batteries of the above Examples and Comparative Examples are collectively shown. It is shown in 2.

  As can be seen from the results in Table 2, the non-aqueous electrolyte contains a specific compound such as lithium difluorophosphate, trimethylsilyl methanesulfonate, hexamethylcyclotrisiloxane, and the tap density is 0.1 or more. In addition, by containing a negative electrode active material having a pore volume in the range of 0.01 μm to 1 μm in mercury porosimetry of 0.01 mL / g or more in the negative electrode, even for a large battery, after a high cycle It has been found that it is possible to provide a lithium ion secondary battery that can achieve an output and a high cycle retention ratio and has both a high output and a long life.

  In addition, by containing a specific compound in the non-aqueous electrolyte solution and having a reaction resistance of 500 Ω or less by the opposing cell of the negative electrode, a high post-cycle output and a high cycle retention rate can be achieved even for large batteries. It can be achieved and has been found to have both high output and good lifetime.

  The use of the lithium ion secondary battery of the present invention is not particularly limited, and can be used for various known uses. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorbikes, bicycles, lighting equipment, toys, game equipment, watches, electric tools, strobes, cameras, etc. Can do. In particular, since the lithium ion secondary battery of the present invention has a good cycle maintenance ratio and output, it can be widely used as a lithium ion secondary battery for high capacity and high output.

Claims (18)

A lithium ion secondary battery having a non-aqueous electrolyte containing a non-aqueous solvent and a lithium salt, a positive electrode containing a positive electrode active material, and a negative electrode containing a negative electrode active material, wherein the non-aqueous electrolyte comprises a general formula ( 1) a cyclic siloxane compound represented by formula (2), a fluorosilane compound represented by formula (2), a compound represented by formula (3), a compound having an SF bond in the molecule, a nitrate, a nitrite, And containing at least 10 ppm of at least one compound selected from the group consisting of monofluorophosphate, difluorophosphate, acetate and propionate in the whole non-aqueous electrolyte solution, and negative electrode, a tap density of 0.1 g / cm ³ or more, and, the negative electrode in mercury porosimetry, pore volume of particles corresponding to the range of diameters 0.01μm~1μm is 0.01 mL / g or more Lithium-ion secondary battery, characterized in that those containing substances.

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

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

[In General Formula (3), R ^{6 to} R ⁸ represent an organic group having 1 to 12 carbon atoms which may be the same as or different from each other, and A represents H, C, N, O, F, S, Represents a group composed of Si and / or P; ] The lithium ion secondary battery according to claim 1, wherein the negative electrode active material has a BET specific surface area of 0.1 m ² / g or more and 100 m ² / g or less.   3. The lithium ion secondary battery according to claim 1, wherein the negative electrode active material has a volume average particle diameter of 1 μm or more and 50 μm or less.   The lithium ion secondary battery according to any one of claims 1 to 3, wherein the negative electrode active material has a circularity of 0.1 or more.   5. The negative electrode active material according to claim 1, wherein a surface spacing (d002) of (002) planes by a wide-angle X-ray diffraction method is 0.335 nm or more and 0.38 nm or less. Lithium ion secondary battery. The lithium ion secondary battery according to any one of claims 1 to 5, wherein a true density of the negative electrode active material is 1.5 g / cm ³ or more. Raman R value, defined as the ratio of the peak intensity of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the argon ion laser Raman spectroscopy of the negative electrode active material, 0.01 or more, according to claim 1 is 1.5 or less The lithium ion secondary battery according to any one of claims 6 to 6.   The lithium ion secondary battery according to any one of claims 1 to 7, wherein an aspect ratio of the negative electrode active material is 1 or more and 10 or less.   The lithium ion secondary battery according to any one of claims 1 to 8, wherein an ash content of the negative electrode active material is 1 ppm or more and 1 mass% or less. A lithium ion secondary battery having a non-aqueous electrolyte containing a non-aqueous solvent and a lithium salt, a positive electrode containing a positive electrode active material, and a negative electrode containing a negative electrode active material, wherein the non-aqueous electrolyte comprises a general formula ( 1) a cyclic siloxane compound represented by formula (2), a fluorosilane compound represented by formula (2), a compound represented by formula (3), a compound having an SF bond in the molecule, a nitrate, a nitrite, And containing at least 10 ppm of at least one compound selected from the group consisting of monofluorophosphate, difluorophosphate, acetate and propionate in the whole non-aqueous electrolyte solution, and A lithium ion secondary battery having a reaction resistance of 500 Ω or less when the negative electrode is charged to 60% of the nominal capacity of the negative electrode.

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

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

[In General Formula (3), R ^{6 to} R ⁸ represent an organic group having 1 to 12 carbon atoms which may be the same as or different from each other, and A represents H, C, N, O, F, S, Represents a group composed of Si and / or P; ]   The negative electrode has a negative electrode active material layer on a current collector, and the content ratio of the binder in the negative electrode active material layer is 15% by mass or less with respect to the entire negative electrode active material layer. The lithium ion secondary battery according to any one of claims 1 to 10.   The lithium ion secondary battery according to any one of claims 1 to 11, wherein the current collector of the negative electrode contains copper, nickel, stainless steel, nickel-plated steel, or aluminum.   Ratio of thickness of negative electrode active material layer and current collector of negative electrode, [(thickness of negative electrode active material layer on one side) / (thickness of current collector)] is 0.1 or more and 150 or less The lithium ion secondary battery according to any one of claims 1 to 12, wherein The density of the negative electrode active material layer, 1 g / cm ³ or more, any one of a lithium ion secondary battery of claim of 1.85 g / cm ³ or less is claims 1 to 13.   The non-aqueous electrolyte includes a cyclic siloxane compound represented by the general formula (1), a fluorosilane compound represented by the general formula (2), a compound represented by the general formula (3), and an SF bond in the molecule. At least one compound selected from the group consisting of a compound having a salt, nitrate, nitrite, monofluorophosphate, difluorophosphate, acetate and propionate in the entire non-aqueous electrolyte solution. The lithium ion secondary battery according to any one of claims 1 to 14, wherein the lithium ion secondary battery is contained in an amount of 01 mass% or more and 5 mass% or less.   The lithium ion secondary battery according to any one of claims 1 to 15, wherein the total area of the positive electrode area with respect to the surface area of the exterior of the secondary battery is 20 times or more in terms of area ratio.   The lithium ion secondary battery according to any one of claims 1 to 16, wherein a DC resistance component of the secondary battery is 10 milliohms (mΩ) or less.   The lithium ion secondary according to any one of claims 1 to 17, wherein an electric capacity of a battery element housed in one battery exterior of the secondary battery is 3 ampere hours (Ah) or more. battery.