JP2021119560A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide: a nonaqueous electrolyte which can achieve a low input resistance in a nonaqueous electrolyte secondary battery having a positive electrode high in Ni content; and a nonaqueous electrolyte secondary battery arranged by use of such a nonaqueous electrolyte, including a positive electrode of high Ni content, and having a low input resistance.SOLUTION: A nonaqueous electrolyte hereof is to be used for a nonaqueous electrolyte secondary battery having: a positive electrode containing a transition metal oxide capable of occluding and releasing metal ions and including at least Ni and Co, in which Ni accounts for 40 mol% or more of the transition metal; a negative electrode containing a carbon-based material capable of occluding and releasing metal ions; and a nonaqueous electrolyte containing a nonaqueous solvent, and an electrolyte dissolved in the nonaqueous solvent. The nonaqueous electrolyte comprises at least one isocyanate compound selected from a compound represented by the general formula (1) below, and a compound represented by the general formula (2) below. In the formula (1), n≥2; and in the formula (2), p≥1 and s≥1.SELECTED DRAWING: None

Description

The present invention relates to a non-aqueous electrolyte solution and a non-aqueous electrolyte solution secondary battery.

Non-aqueous electrolyte secondary batteries such as lithium secondary batteries in a wide range of applications such as power supplies for mobile phones such as smartphones and so-called consumer small devices such as laptop computers, and in-vehicle power supplies for driving such as electric vehicles. Has been put into practical use.

As a means for improving the battery characteristics of a non-aqueous electrolyte battery, many studies have been made in the fields of positive electrode and negative electrode active materials and non-aqueous electrolyte solution additives.

For example, Patent Document 1 provides a non-aqueous electrolyte solution having excellent battery life and a secondary battery using the non-aqueous electrolyte solution, which comprises a non-aqueous solvent containing an isocyanato group-containing compound and an electrolyte. Liquids and secondary batteries using this electrolyte are disclosed. In the examples, LiCoO ₂ electrode was mixed as the positive electrode, graphite was mixed as the negative electrode, and ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed as the electrolytic solution at a ratio of EC: MEC = 4: 6 (weight ratio). , Isocyanato group-containing compounds 1,3-diisocyanato-4-methylbenzene (Examples 1 to 3), di (isocyanatonorbornyl) uretidine-2,4-dione (Examples 4 to 6) or di Disclosed about the load characteristics of a non-aqueous electrolyte secondary battery using (isocyanatonorbornyl) 1,3,5-oxadiazine-2,4,6-trione (Examples 7 to 9) after high temperature storage. There is.
Patent Document 2 aims to provide a non-aqueous electrolyte battery that generates less gas and has excellent battery characteristics, and has a positive electrode provided with a positive electrode active material and a lithium occlusion / release potential of 1.0 V (vs L).
In a non-aqueous electrolyte battery having a negative electrode having a negative electrode active material more noble than i / Li ⁺ ) and a non-aqueous electrolyte, a non-aqueous electrolyte battery in which an organic compound having an isocyanato group is added to the non-aqueous electrolyte. It is disclosed. _{In the example, for a non-aqueous electrolyte secondary battery using a positive electrode containing LiMn 2} O ₄ as a positive electrode active material, a non-aqueous electrolyte solution containing 1,6-diisosianatohexane was used, and the amount of gas generated and the high rate were used. The characteristics and residual capacity ratio have been examined.
Patent Document 3 describes a non-aqueous electrolyte battery provided with a positive electrode, a negative electrode, an electrolyte, and a separator for the purpose of providing a battery having improved battery characteristics during a high temperature cycle by suppressing decomposition of a solvent and deformation of the battery. It is disclosed that the positive electrode contains 1000 ppm to 50 ppm of water, and the electrolyte contains a specific isocyanate compound and a specific aromatic compound. In the embodiment, for a non-aqueous electrolyte battery using a positive electrode containing lithium cobalt oxide as the positive electrode active material, the water concentration in the positive electrode active material layer and the type and content of the isocyanate compound are changed to maintain the high temperature storage capacity. It is being considered.

JP-A-2002-8719 Japanese Unexamined Patent Publication No. 2009-54319 Japanese Unexamined Patent Publication No. 2011-288860

In recent years, there has been an even greater demand for higher capacity lithium batteries for in-vehicle power supplies for electric vehicles, power supplies for mobile phones such as smartphones, and the like. As a high-capacity positive electrode active material, a transition metal oxide positive electrode having a high Ni content has attracted attention. However, the present inventors have input that a positive electrode having a high Ni content undergoes a surface reaction with an electrolytic solution during charging. We found that there was a problem that the characteristics deteriorated.

In view of the above, the present invention uses a positive electrode containing a transition metal oxide, a positive electrode in which the positive electrode contains at least Ni and Co and 40 mol% or more of the transition metal is Ni, and a negative electrode containing a carbon-based material. In a non-aqueous electrolyte secondary battery using The subject is to provide the next battery.

As a result of diligent studies to solve the above problems, the present inventor is a transition metal oxide capable of storing and releasing metal ions, which contains at least Ni and Co, and 40 mol% or more of the transition metal is Ni. It includes a positive electrode containing a transition metal oxide, a negative electrode containing a carbon-based material capable of storing and releasing metal ions, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. Non-aqueous electrolyte solution By using a non-aqueous electrolyte solution containing at least one compound selected from the compound represented by the general formula (1) and the isocyanate compound represented by the general formula (2) in the secondary battery. The present invention was completed with the idea that a low input resistance of a non-aqueous electrolyte secondary battery could be realized.

（式（１）中、ｍ、ｎはｍ＋ｎ＝６を満たす整数であり、ｎ≧２である。Ｘは単結合、又は互いに同一でも異なっていてもよいヘテロ原子を有していてもよい炭素数１〜１０の２価の有機基を表す。Ｙは水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭素数１〜１０の１価の有機基を表す。）

（式（２）中、ｐ、ｑ、ｒ、ｓはｐ＋ｑ＝５、ｒ＋ｓ＝５を満たす整数であり、ｐ≧１、ｓ≧１である。Ｒは互いに同一でも異なっていてもよい水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭素数１〜１０の有機基を表す。Ｘ’は単結合、又はヘテロ原子を有していてもよい炭素数１〜１０の２価の有機基を表す。）
＜２＞ 前記非水系電解液が前記式（１）で示される化合物を含有し、前記式（１）中、ｎが２である、＜１＞に記載の非水系電解液。
＜３＞ 前記非水系電解液が前記式（１）で示される化合物を含有し、前記式（１）中、
Ｘがメチレン基又はジメチルメチレン基である、＜１＞又は＜２＞に記載の非水系電解液。
＜４＞前記非水系電解液が前記式（２）で示される化合物を含有し、前記式（２）中、ｓ＝ｐ＝１である、＜１＞に記載の非水系電解液。
＜５＞前記非水系電解液が、Ｐ−Ｆ結合を有する化合物、及びＳＯ_２構造を有する化合物の少なくとも１種を含む、＜１＞〜＜４＞のいずれかに記載の非水系電解液。
＜６＞金属イオンを吸蔵および放出可能な正極と、金属イオンを吸蔵および放出可能な炭素系材料を含有する負極と、非水溶媒と該非水溶媒に溶解される電解質を含む非水系電解液と、
を備える非水系電解液二次電池であって、
該正極が、遷移金属酸化物を含有し、かつ遷移金属として少なくともＮｉ及びＣｏを含有し、遷移金属のうち４０モル％以上がＮｉであり、
該非水系電解液が、＜１＞〜＜５＞のいずれかに記載の非水系電解液である、非水系電解液二次電池。 The present invention provides the following aspects and the like.
<1> A transition metal oxide capable of occluding and releasing metal ions, which contains at least Ni and Co and contains a transition metal oxide in which 40 mol% or more of the transition metal is Ni.
A non-aqueous electrolyte solution used in a non-aqueous electrolyte secondary battery comprising a negative electrode containing a carbon-based material capable of occluding and releasing metal ions, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. It is an aqueous electrolyte
A non-aqueous electrolytic solution containing at least one of an isocyanate compound selected from the compound represented by the following general formula (1) and the compound represented by the general formula (2).

(In the formula (1), m and n are integers satisfying m + n = 6, and n ≧ 2. X is a single bond or a carbon which may have a heteroatom which may be the same or different from each other. It represents a divalent organic group of numbers 1 to 10. Y represents a monovalent organic group of carbon numbers 1 to 10 which may have a hydrogen atom, a halogen atom, or a hetero atom.)

(In equation (2), p, q, r, s are integers satisfying p + q = 5, r + s = 5, and p ≧ 1, s ≧ 1. R is a hydrogen atom which may be the same or different from each other. , A halogen atom, or an organic group having 1 to 10 carbon atoms which may have a hetero atom. X'is a single bond or a divalent group having 1 to 10 carbon atoms which may have a hetero atom. Represents an organic group.)
<2> The non-aqueous electrolyte solution according to <1>, wherein the non-aqueous electrolyte solution contains the compound represented by the formula (1), and n is 2 in the formula (1).
<3> The non-aqueous electrolyte solution contains the compound represented by the formula (1), and in the formula (1),
The non-aqueous electrolyte solution according to <1> or <2>, wherein X is a methylene group or a dimethylmethylene group.
<4> The non-aqueous electrolyte solution according to <1>, wherein the non-aqueous electrolyte solution contains the compound represented by the formula (2), and s = p = 1 in the formula (2).
<5> The non-aqueous electrolyte solution according to any one of <1> to <4>, wherein the non-aqueous electrolyte solution contains at least one compound having a _{PF bond and a compound having an SO 2 structure.}
<6> A positive electrode capable of occluding and releasing metal ions, a negative electrode containing a carbon-based material capable of occluding and releasing metal ions, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. ,
It is a non-aqueous electrolyte secondary battery equipped with
The positive electrode contains a transition metal oxide and at least Ni and Co as a transition metal, and 40 mol% or more of the transition metal is Ni.
A non-aqueous electrolyte secondary battery in which the non-aqueous electrolyte solution is the non-aqueous electrolyte solution according to any one of <1> to <5>.

According to the present invention, there is provided a non-aqueous electrolyte secondary battery provided with a positive electrode having a high Ni content, which can realize a low input resistance. Further, a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte solution and having a positive electrode having a low input resistance and a high Ni content is provided.

Hereinafter, embodiments of the present invention will be described in detail. The following embodiments are examples (representative examples) of the present invention, and the present invention is not limited thereto. Further, the present invention can be arbitrarily modified and implemented without departing from the gist thereof.

（式（１）中、ｍ、ｎはｍ＋ｎ＝６を満たす整数であり、ｎ≧２である。Ｘは単結合、又は互いに同一でも異なっていてもよいヘテロ原子を有していてもよい炭素数１〜１０の２価の有機基を表す。Ｙは水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭素数１〜１０の１価の有機基を表す。）

（式（２）中、ｐ、ｑ、ｒ、ｓはｐ＋ｑ＝５、ｒ＋ｓ＝５を満たす整数であり、ｐ≧１、ｓ≧１である。Ｒは互いに同一でも異なっていてもよい水素原子、ハロゲン原子、又はヘ
テロ原子を有していてもよい炭素数１〜１０の１価の有機基を表す。Ｘ’は単結合、又はヘテロ原子を有していてもよい炭素数１〜１０の２価の有機基を表す。） <1. Non-aqueous electrolyte solution>
The non-aqueous electrolyte solution according to the present embodiment is a transition metal oxide capable of storing and releasing metal ions, containing at least Ni and Co, and 40 mol% or more of the transition metal is Ni. A non-aqueous electrolyte solution comprising a positive electrode containing a substance, a negative electrode containing a carbon-based material capable of storing and releasing metal ions, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. It is a non-aqueous electrolyte solution used for a secondary battery, and is characterized by containing at least one of an isocyanate compound selected from the compound represented by the following general formula (1) and the compound represented by the general formula (2). And.

(In the formula (1), m and n are integers satisfying m + n = 6, and n ≧ 2. X is a single bond or a carbon which may have a heteroatom which may be the same or different from each other. It represents a divalent organic group of numbers 1 to 10. Y represents a monovalent organic group of carbon numbers 1 to 10 which may have a hydrogen atom, a halogen atom, or a hetero atom.)

(In equation (2), p, q, r, s are integers satisfying p + q = 5, r + s = 5, and p ≧ 1, s ≧ 1. R is a hydrogen atom which may be the same or different from each other. , A halogen atom, or a monovalent organic group having 1 to 10 carbon atoms which may have a hetero atom. X'is a single bond or has 1 to 10 carbon atoms which may have a hetero atom. Represents a divalent organic group.)

A transition capable of storing and releasing metal ions by using a non-aqueous electrolyte solution containing at least one isocyanate compound selected from the compound represented by the general formula (1) and the compound represented by the general formula (2). A non-aqueous electrolyte secondary battery having a positive electrode containing a transition metal oxide containing at least Ni and Co and 40 mol% or more of the transition metal being Ni is defined as a metal oxide having a low input resistance. The mechanism is not clear, but it is speculated as follows.
Among the positive electrode materials, Mn, Co, and Fe, which are typical transition metals used for the positive electrode active material, have a valence change of +1 during charging. On the other hand, in the Ni-containing positive electrode, the valence of Ni changes from +2 to +4 during charging, but as the proportion of Ni contained increases, the unstable +3 valence increases. Since the trivalent value of Ni is unstable, a surface reaction with the electrolytic solution occurs, and it is presumed that the input characteristics deteriorate due to the deactivation of the Li insertion point on the surface. The present inventors have come up with the idea of reducing the surface activity of unstable Ni, which is abundant in a positive electrode having a high Ni content. In the present embodiment, by including the compound containing an aromatic ring in the electrolytic solution, the aromatic ring π electron and the unstable Ni existing on the surface interact with each other to preferentially adsorb and stabilize the active point. It is expected to be. Further, the compound represented by the formula (1) or the formula (2) has two or more isocyanate (NCO) groups, so that the NCO groups are polymerized from each other starting from the nucleophile contained in the electrolytic solution and added. It is presumed that the active site coating effect of the agent becomes stronger and the effect of the present invention is exhibited. At this time, the nucleophile contained in the electrolytic solution is produced by reducing the electrolytic solution component, and in the present invention, the negative electrode material (represented by a carbon-based material) having a potential at which the electrolytic solution component can be reduced. To be) is used.
Further, it is presumed that by using an isocyanate compound in which the NCO group is not directly linked to the aromatic ring and the hydrocarbon group is used, the effect of protecting the active site can be easily exerted while suppressing the decomposition of the compound itself.

<1-1. Isocyanate compound>
The non-aqueous electrolyte solution according to the embodiment of the present invention contains at least one isocyanate compound selected from the compound represented by the following general formula (1) and the compound represented by the following general formula (2). It is a feature.

（式（１）中、ｍ、ｎはｍ＋ｎ＝６を満たす整数であり、ｎ≧２である。Ｘは単結合、又は互いに同一でも異なっていてもよいヘテロ原子を有していてもよい炭素数１〜１０の２価の有機基を表す。Ｙは水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭素数１〜１０の１価の有機基を表す。） <1-1-1. Compound represented by general formula (1)>

(In the formula (1), m and n are integers satisfying m + n = 6, and n ≧ 2. X is a single bond or a carbon which may have a heteroatom which may be the same or different from each other. It represents a divalent organic group of numbers 1 to 10. Y represents a monovalent organic group of carbon numbers 1 to 10 which may have a hydrogen atom, a halogen atom, or a hetero atom.)

X according to the general formula (1) represents a single bond or a divalent organic group having 1 to 10 carbon atoms which may have heteroatoms which may be the same or different from each other.
Examples of the divalent organic group having 1 to 10 carbon atoms which may have a hetero atom include a hydrocarbon group having 10 or less carbon atoms and which may have a substituent; a carbonyl group; or 2 or more. Is selected from a hydrocarbon group which may have a substituent and an oxygen atom (-O-), a sulfur atom (-S-), a carbonyl group (-CO-) and an amino group (-NH-). A group consisting of at least one group;

Such groups include an ether group consisting of a hydrocarbon group which may have a substituent and an oxygen atom (-O-); a hydrocarbon group which may have a substituent and an oxygen atom (-O-). An ester group consisting of an O-) and a carbonyl group (-CO-); a thioether group consisting of a hydrocarbon group which may have a substituent and a sulfur atom (-S-); a substituent. Examples thereof include an amide group consisting of a good hydrocarbon group, an amino group (-NH-) and a carbonyl group (-CO-).

Specific examples of the hydrocarbon group include an alkylene group having 1 to 10 carbon atoms such as methylene, ethylene, propylene and butylene; an alkenylene group having 2 to 10 carbon atoms such as vinylene; and an ethynylene group having 2 carbon atoms. Examples thereof include alkynylene groups of 10 to 10; cycloalkenylene groups such as cyclopentylene and cyclohexylene groups; and arylene groups having 6 to 10 carbon atoms such as phenylene groups;
Of these, a divalent hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent, is preferable from the viewpoint of the input resistance of the battery. When the hydrocarbon group has a substituent, the number of carbons contained in the substituent is not included in this number of carbon atoms.
More preferably, it is a divalent linear or branched aliphatic hydrocarbon group having 1 to 6 carbon atoms, which may have a substituent, and more preferably, a divalent linear chain having 1 to 4 carbon atoms. Alternatively, it is a branched aliphatic hydrocarbon group. Preferred examples of such a hydrocarbon group include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylmethylene group, a dimethylene group, a trimethylene group and a tetramethylene group.

Here, examples of the hetero atom include a halogen atom, a phosphorus atom, a silicon atom, an oxygen atom and a sulfur atom. Among them, a fluorine atom from the viewpoint of lowering the input resistance of the battery and having few electrochemical side reactions. Is preferable.
The heteroatom may be substituted with a carbon atom of a hydrocarbon group or may be substituted with a hydrogen atom of a hydrocarbon group.

Here, the substituents include a cyano group, an isocyanato group, an acyl group (-(C = O) -R ^a ), an acyloxy group (-O (C = O) -R ^a ), and an alkoxycarbonyl group (-(). C = O) O-R ^a ), sulfonyl group (-SO _2- R ^a ), sulfonyloxy group (-O (SO ₂ ) -R ^a ), alkoxysulfonyl group (-(SO ₂ ) -O-R ^a) ), Alkoxysulfonyloxy group (-O- (SO ₂ ) -O-R ^a ), Alkoxycarbonyloxy group (-O- (C = O) -O-R ^a ), Alkoxy group (-O-R ^a ) , Halogen atom (preferably fluorine atom), trifluoromethyl group and the like. ^Ra represents an alkyl group having 1 to 10 carbon atoms, an alkylene group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms. When ^Ra is an alkylene group, it may be bonded to a part of the substituted hydrocarbon group to form a ring.
Among the above substituents, a cyano group, an isocyanato group, an acyloxy group (-O (C = O) -R a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group, more preferably , isocyanato group, an acyloxy group ^{(-O (C = O) -R} a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group, particularly preferably an acyloxy group (-O (C = O) -R ^a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group.

X according to the general formula (1) is more preferably a single bond, a methylene group or a dimethylmethylene group, which has a shorter distance between the aromatic ring and the NCO group, from the viewpoint of increasing the coating density on the positive electrode surface, and the general formula (1). ), The methylene group and the dimethylmethylene group are particularly preferable from the viewpoint of the protective effect on the active site while suppressing the decomposition of the compound itself.
X according to the general formula (1) may be the same or different, but it is preferable that they are the same in that the compound can be easily synthesized.
From the viewpoint of sufficiently lowering the input resistance of the non-aqueous electrolyte secondary battery, the diisocyanate compound having n of 2 in the formula (1) is particularly preferable.

Y according to the general formula (1) represents a monovalent organic group having 1 to 10 carbon atoms which may have a hydrogen atom, a halogen atom, or a hetero atom.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is preferable from the viewpoint of having few electrochemical side reactions.
Examples of the monovalent organic group having 1 to 10 carbon atoms which may have a hetero atom include a hydrocarbon group which may have a substituent, and more specifically, a substituent may be used. Examples include linear or branched aliphatic hydrocarbon groups which may have, as well as aromatic hydrocarbon groups which may have substituents.
The hydrocarbon group having 1 to 10 carbon atoms is preferably a hydrocarbon group having 1 to 6 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 4 carbon atoms.
Specific examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group and an aryl group.

Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a tert-butyl group, an n-pentyl group, a hexyl group, a heptyl group, an octyl group and a nonyl group. , Decyl group and the like. Of these, methyl group, ethyl group, n-propyl group, n-butyl group, tert-butyl group, n-pentyl group and hexyl group are preferable, and methyl group, ethyl group, n-propyl group and n-butyl group are more preferable. Groups, tert-butyl group, n-pentyl group, particularly preferably methyl group, ethyl group, n-butyl group, tert-butyl group can be mentioned. The above-mentioned alkyl group is preferable because the compound represented by the general formula (A) tends to be localized near the surface of the positive electrode active material and / or the negative electrode active material.

Specific examples of the alkenyl group include a vinyl group, an allyl group, a metallicyl group, a 2-butenyl group, a 3-methyl2-butenyl group, a 3-butenyl group, a 4-pentenyl group and the like. Of these, a vinyl group, an allyl group, a metalyl group, a 2-butenyl group, more preferably a vinyl group, an allyl group, a metalyl group, and particularly preferably a vinyl group or an allyl group can be mentioned. The above-mentioned alkenyl group is preferable because the compound represented by the general formula (1) tends to be localized near the surface of the positive electrode active material.

Specific examples of the alkynyl group include an ethynyl group, a 2-propynyl group, a 2-butynyl group, a 3-butynyl group, a 4-pentynyl group, a 5-hexynyl group and the like. Of these, ethynyl group, 2-propynyl group, 2-butynyl group, 3-butynyl group are more preferable, 2-propynyl group and 3-butynyl group are more preferable, and 2-propynyl group is particularly preferable. The above-mentioned alkynyl group is preferable because the compound represented by the general formula (1) tends to be localized near the surface of the positive electrode active material and / or the negative electrode active material.

Specific examples of the aryl group include a phenyl group, a tolyl group, a benzyl group, a phenethyl group and the like. Of these, a phenyl group is preferable from the viewpoint that the compound represented by the general formula (1) tends to be localized near the surface of the positive electrode active material.
Examples of the hetero atom include a halogen atom, a phosphorus atom, a silicon atom, an oxygen atom and a sulfur atom, and among them, a fluorine atom is preferable from the viewpoint of few electrochemical side reactions.
The heteroatom may be substituted with a carbon atom of a hydrocarbon group or may be substituted with a hydrogen atom of a hydrocarbon group.
Here, the substituents include a cyano group, an isocyanato group, an acyl group (-(C = O) -R ^a ), an acyloxy group (-O (C = O) -R ^a ), and an alkoxycarbonyl group (-(). C = O) O-R ^a ), sulfonyl group (-SO _2- R ^a ), sulfonyloxy group (-O (SO ₂ ) -R ^a ), alkoxysulfonyl group (-(SO ₂ ) -O-R ^a) ), Alkoxysulfonyloxy group (-O- (SO ₂ ) -O-R ^a ), Alkoxycarbonyloxy group (-O- (C = O) -O-R ^a ), Alkoxy group (-O-R ^a ) , Halogen atom (preferably fluorine atom), trifluoromethyl group and the like. ^Ra represents an alkyl group having 1 to 10 carbon atoms, an alkylene group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms. When ^Ra is an alkylene group, it may be bonded to a part of the substituted hydrocarbon group to form a ring.
Among the above substituents, a cyano group, an isocyanato group, an acyloxy group (-O (C = O) -R a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group, more preferably , isocyanato group, an acyloxy group ^{(-O (C = O) -R} a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group, particularly preferably an acyloxy group (-O (C = O) -R ^a), halogen (preferably fluorine atom), a trifluoromethyl group.
Y is preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably a hydrogen atom or a methyl group, from the viewpoint of sufficiently lowering the input resistance of the non-aqueous electrolyte secondary battery.

Specific examples of the compound represented by the formula (1) include 1,3-xylylene diisocyanate, 1,3-bis (2-isocyanato-2-propyl) benzene, toluene diisocyanate, and phenylenedi isocyanate. Of these, 1,3-xylylene diisocyanate, 1,3-bis (2-isocyanato-2-propyl) benzene, and toluene diisocyanate are preferable from the viewpoint of lowering the input resistance of the battery. In addition, 1,3-xylylene diisocyanate and 1,3-bis (2-isocyanato-2-propyl) benzene are more likely to exert a protective effect on the active site while suppressing the decomposition of the compound itself. preferable.

（式（２）中、ｐ、ｑ、ｒ、ｓはｐ＋ｑ＝５、ｒ＋ｓ＝５を満たす整数であり、ｐ≧１、ｓ≧１である。Ｒは互いに同一でも異なっていてもよい水素原子、ハロゲン原子、又はヘテロ原子を有していてもよい炭素数１〜１０の有機基を表す。Ｘ’は単結合、又はヘテロ原子を有していてもよい炭素数１〜１０の２価の有機基を表す。） <1-1-2. Compound represented by general formula (2)>

(In equation (2), p, q, r, s are integers satisfying p + q = 5, r + s = 5, and p ≧ 1, s ≧ 1. R is a hydrogen atom which may be the same or different from each other. , A halogen atom, or an organic group having 1 to 10 carbon atoms which may have a hetero atom. X'is a single bond or a divalent group having 1 to 10 carbon atoms which may have a hetero atom. Represents an organic group.)

In the general formula (2), R represents an organic group having 1 to 10 carbon atoms which may have a hydrogen atom, a halogen atom, or a hetero atom which may be the same or different from each other.
Examples of the halogen atom include a fluorine atom, a chlorine atom and a bromine atom. Preferably, it is a fluorine atom in terms of having few electrochemical side reactions.
Examples of the heteroatom of the organic group having 1 to 10 carbon atoms which may have a heteroatom include a halogen atom, a phosphorus atom, a silicon atom, an oxygen atom and a sulfur atom.
The organic group having 1 to 10 carbon atoms which may have a heteroatom may have, for example, a hydrocarbon group having 1 to 10 carbon atoms which may have a substituent and a substituent. Examples thereof include an alkoxy group having 1 to 10 carbon atoms, an amino group and an amide group.
Among them, a hydrocarbon group having 1 to 10 carbon atoms which may have a substituent or an alkoxy group having 1 to 10 carbon atoms which may have a substituent is preferable. When the hydrocarbon group has a substituent, the number of carbons contained in the substituent is also included in this number of carbons.
The hydrocarbon group may be a hydrocarbon group having a carbon-carbon unsaturated bond and having 2 to 10 carbon atoms. Examples of the hydrocarbon group having 2 to 10 carbon atoms having a carbon-carbon unsaturated bond include an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and an aryl group having 6 to 10 carbon atoms, which will be described later. Be done.
When a plurality of Rs according to the general formula (2) are present, they may be the same or different, but the same is preferable in that the compound can be easily synthesized.
The hydrocarbon group having 1 to 10 carbon atoms is preferably a hydrocarbon group having 1 to 6 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 4 carbon atoms.
Specific examples of the hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group and an aryl group.
Specific examples of the alkyl group include groups similar to those exemplified in the description of the compound represented by the formula (1). Preferably methyl group, ethyl group, n-propyl group, n-butyl group, tert-butyl group, n-pentyl group, hexyl group, more preferably methyl group, ethyl group, n-propyl group, n-butyl group. , Tert-Butyl group, n-pentyl group, particularly preferably methyl group, ethyl group, n-butyl group, tert-butyl group.

Specific examples of the alkenyl group include groups similar to those exemplified in the description of the compound represented by the formula (1). Of these, a vinyl group, an allyl group, a metalyl group, a 2-butenyl group, more preferably a vinyl group, an allyl group, a metalyl group, and particularly preferably a vinyl group or an allyl group can be mentioned. The above-mentioned alkenyl group is preferable because the compound represented by the general formula (2) tends to be localized near the surface of the positive electrode active material.

Specific examples of the alkynyl group include groups similar to those exemplified in the description of the compound represented by the formula (1). Of these, ethynyl group, 2-propynyl group, 2-butynyl group, 3-butynyl group are more preferable, 2-propynyl group and 3-butynyl group are more preferable, and 2-propynyl group is particularly preferable. The above-mentioned alkynyl group is preferable because the compound represented by the general formula (2) tends to be localized near the surface of the positive electrode active material.

Specific examples of the aryl group include a group similar to the group exemplified in the description of the compound represented by the formula (1). Of these, a phenyl group is preferable from the viewpoint that the compound represented by the general formula (2) tends to be localized near the surface of the positive electrode active material.
The alkoxy group having 1 to 10 carbon atoms is preferably an alkoxy group having 1 to 6 carbon atoms, and particularly preferably an alkoxy group having 1 to 4 carbon atoms.
Specific examples of the alkoxy group having 1 to 10 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, an isopropoxy group, a methoxyethoxy group and the like. Of these, the methoxy group and the ethoxy group are preferable in that the compound represented by the general formula (1) has less steric hindrance and is suitably concentrated on the surface of the active material.

Here, the substituents include a cyano group, an isocyanato group, an acyl group (-(C = O) -R ^a ), an acyloxy group (-O (C = O) -R ^a ), and an alkoxycarbonyl group (-(). C = O) O-R ^a ), sulfonyl group (-SO _2- R ^a ), sulfonyloxy group (-O (SO ₂ ) -R ^a ), alkoxysulfonyl group (-(SO ₂ ) -O-R ^a) ), Alkoxysulfonyloxy group (-O- (SO ₂ ) -O-R ^a ), Alkoxycarbonyloxy group (-O- (C = O) -O-R ^a ), Alkoxy group (-O-R ^a ) , Halogen atom (preferably fluorine atom), trifluoromethyl group and the like. ^Ra represents an alkyl group having 1 to 10 carbon atoms, an alkylene group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms. When ^Ra is an alkylene group, it may be bonded to a part of the substituted hydrocarbon group to form a ring.
Among the above substituents, a cyano group, an isocyanato group, an acyloxy group (-O (C = O) -R a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group, more preferably , isocyanato group, an acyloxy group ^{(-O (C = O) -R} a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group, particularly preferably an acyloxy group (-O (C = O) -R ^a), a halogen atom (preferably, fluorine atom), a trifluoromethyl group.
Specific examples of the compound represented by the formula (2) include 4,4'-diphenylmethane diisocyanate and bis (4-isocyanatophenyl) dimethylmethane. From the viewpoint of lowering the input resistance of the battery, 4,4'-diphenylmethane diisocyanate is preferable.

The total content of the compound represented by the general formula (1) and the isocyanate compound represented by the formula (2) with respect to the total amount of the non-aqueous electrolyte solution according to the embodiment of the present invention is usually 0.001% by mass or more. It is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and usually 10% by mass or less, preferably 8% by mass or less, more preferably. It is 6.0% by mass or less, more preferably 4.0% by mass or less, particularly preferably 3.0% by mass or less, particularly preferably 2.0% by mass or less, and most preferably 1.0% by mass or less. be.
When the total content of the isocyanate compounds represented by the general formula (1) or (2) with respect to the total amount of the non-aqueous electrolyte solution is within the above range, the polymerization of the NCO group proceeds favorably and the activity on the positive electrode is active. A non-aqueous electrolyte secondary battery with a sufficient point coating effect and low input resistance can be manufactured.
The method of incorporating the compound represented by the general formula (1) or the compound represented by the formula (2) into the electrolytic solution of the present invention is not particularly limited. In addition to the method of directly adding the compound to the electrolytic solution, a method of generating the compound in a battery or an electrolytic solution can be mentioned.

<1-2. Electrolyte>
The non-aqueous electrolyte solution of the present embodiment usually contains an electrolyte as a component thereof, like a general non-aqueous electrolyte solution. The electrolyte used in the non-aqueous electrolyte solution of the present embodiment is not particularly limited, and known electrolytes can be used. Hereinafter, specific examples of the electrolyte will be described in detail.

<1-2-1. Lithium salt>
When the non-aqueous electrolyte secondary battery in which the non-aqueous electrolyte solution according to the present embodiment is used is a lithium ion secondary battery, a lithium salt is usually used as the electrolyte. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any one or more lithium salts can be used, and specific examples thereof include the following.

For example, inorganic lithium salts _{such as LiBF 4} , LiClO ₄ , _{LiAlF 4} , LiSbF ₆ , LiTaF ₆ , LiWF _7;
Lithium fluorophosphates such as LiPF _6;
Lithium tungstic acid salts such as LiWOF _5;
Lithium carboxylic acid salts such as CF ₃ CO _{2 Li;}
Lithium sulfonic acid salts such as CH ₃ SO _{3 Li;}
Lithium imide salts such as LiN (FSO ₂ ) ₂ and LiN (CF ₃ SO ₂ ) _2;
LiC (FSO ₂ ) ₃ etc. lithium methide salts;
Lithium oxalate salts such as lithium bisoxalatoborate and lithium difluorooxalatoborate;
In addition, fluorine-containing organic lithium salts such as _{LiPF 4} (CF ₃ ) _2;
And so on.

In addition to the effect of improving durability obtained by the present invention, the effect of improving charge / discharge rate characteristics and impedance characteristics is further enhanced. Salts are preferably selected, and inorganic lithium salts, lithium imide salts, and lithium oxalate salts are more preferable from the viewpoint of improving charge / discharge characteristics.

The total concentration of these electrolytes in the non-aqueous electrolyte solution is not particularly limited as long as the effects of the present invention are not significantly impaired, but is preferably 0.5 mol / L or more with respect to the total amount of the non-aqueous electrolyte solution. More preferably 0.6 mol / L or more, still more preferably 0.7 mol / L or more, while preferably 3 mol / L or less, more preferably 2 mol / L or less, still more preferably 1. It is 8 mol / L or less. When the content of the lithium salt is within the above range, the ionic conductivity can be appropriately increased.
When the total concentration of the electrolyte is within the above range, the electrical conductivity becomes appropriate for battery operation, so that sufficient output characteristics tend to be obtained.
The method for measuring the content of the lithium salt described above is not particularly limited, and a known method can be arbitrarily used. Examples of such a method include ion chromatography, nuclear magnetic resonance spectroscopy, and the like.

<1-3. Non-aqueous solvent>
Like a general non-aqueous electrolyte solution, the non-aqueous electrolyte solution used in the present embodiment usually contains a non-aqueous solvent that dissolves an electrolyte described later as its main component. The non-aqueous solvent used here is not particularly limited, and a known organic solvent can be used. The organic solvent preferably includes, but is not limited to, at least one selected from saturated cyclic carbonates, chain carbonates, chain carboxylic acid esters, cyclic carboxylic acid esters, ether compounds, and sulfone compounds. .. These can be used individually by 1 type or in combination of 2 or more types.

<1-3-1. Saturated cyclic carbonate>
Examples of the saturated cyclic carbonate include those having an alkylene group having 2 to 4 carbon atoms. Specifically, examples of the saturated cyclic carbonate having 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Of these, ethylene carbonate and propylene carbonate are preferable from the viewpoint of improving battery characteristics due to the improvement in the degree of lithium ion dissociation. As the saturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but the lower limit is usually 3% by volume or more, preferably 5% by volume or more in 100% by volume of the non-aqueous solvent. Is. By setting this range, it is possible to avoid a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte solution, and to improve the large current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the non-aqueous electrolyte secondary battery. It will be easier to set the range. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting this range, the viscosity of the non-aqueous electrolyte solution can be set to an appropriate range, the decrease in ionic conductivity can be suppressed, and the input / output characteristics of the non-aqueous electrolyte secondary battery can be further improved, and the cycle characteristics and storage can be achieved. It is preferable because durability such as characteristics can be further improved.

<1-3-2. Chain carbonate>
The chain carbonate preferably has 3 to 7 carbon atoms. Specifically, examples of the chain carbonate having 3 to 7 carbon atoms include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propylisopropyl carbonate, ethylmethyl carbonate, methyl-n-propyl carbonate, and the like. Examples thereof include n-butylmethyl carbonate, isobutylmethyl carbonate, t-butylmethyl carbonate, ethyl-n-propyl carbonate, n-butylethyl carbonate, isobutylethyl carbonate, t-butylethyl carbonate and the like. Among these, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate and methyl-n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are particularly preferable. preferable.

Further, chain carbonates having a fluorine atom (hereinafter, may be abbreviated as "fluorinated chain carbonate") can also be preferably used. The number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.

As the chain carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more in 100% by volume of the non-aqueous solvent. Further, it is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting the content of the chain carbonate in the above range, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, the decrease in ionic conductivity is suppressed, and the input / output characteristics and charging / discharging of the non-aqueous electrolyte secondary battery are suppressed. It is easy to set the rate characteristics in a good range. In addition, the decrease in electrical conductivity due to the decrease in the dielectric constant of the non-aqueous electrolyte solution can be avoided, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery can be easily set in a good range.

<1-3-3. Chain Carboxylic Acid Ester>
Examples of the chain carboxylic acid ester include those having a total carbon number of 3 to 7 in the structural formula. Specifically, methyl acetate, ethyl acetate, -n-propyl acetate, isopropyl acetate, -n-butyl acetate, isobutyl acetate, -t-butyl acetate, methyl propionate, ethyl propionate, -n-propyl propionate, Isopropyl propionate, -n-butyl propionate, isobutyl propionate, -t-butyl propionate, methyl butyrate, ethyl butyrate, -n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, -n-isobutyrate Examples thereof include propyl and isopropyl isobutyrate. Among these, methyl acetate, ethyl acetate, -n-propyl acetate, -n-butyl acetate, methyl propionate, ethyl propionate, -n-propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate and the like have viscosities. It is preferable from the viewpoint of improving the ionic conductivity due to the decrease and suppressing the battery swelling during the durability test such as cycle and storage. The content of the chain carboxylic acid ester as the non-aqueous solvent is not particularly limited, but is usually 5% by volume or more, usually 50% by volume or less, preferably 30% by volume or less in 100% by volume of the non-aqueous solvent. More preferably, it is 20% by volume or less. The chain carboxylic acid ester can also be used as an additive in an amount of less than 5% by volume in 100% by volume of the non-aqueous solvent.

<1-3-4. Cyclic carboxylic acid ester>
Examples of the cyclic carboxylic acid ester include those having a total carbon atom number of 3 to 12 in the structural formula. Specific examples thereof include gamma-butyrolactone, gamma valerolactone, gamma caprolactone, and epsilon caprolactone. Among these, gamma-butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation. The content of the cyclic carboxylic acid ester as the non-aqueous solvent is not particularly limited, but is usually 5% by volume or more, usually 50% by volume or less, preferably 30% by volume or less, based on 100% by volume of the non-aqueous solvent. It is preferably 20% by volume or less. The cyclic carboxylic acid ester can also be used as an additive in an amount of less than 5% by volume in 100% by volume of the non-aqueous solvent.

<1-3-5. Ether compounds>
As the ether compound, a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferable.

Examples of the chain ether having 3 to 10 carbon atoms include diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, and ethyl. (2-Fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2) -Trifluoroethyl) ether, (2-fluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetrafluoro) Ethyl) ether, ethyl-n-propyl ether, ethyl (3-fluoro-n-propyl) ether, ethyl (3,3,3-trifluoro-n-propyl) ether, ethyl (2,2,3,3- Tetrafluoro-n-propyl) ether, ethyl (2,2,3,3,3-pentafluoro-n-propyl) ether, 2-fluoroethyl-n-propyl ether, (2-fluoroethyl) (3-fluoro) -N-propyl) ether, (2-fluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ) Ether, (2-fluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, 2,2,2-trifluoroethyl-n-propyl ether, (2,2,2) -Trifluoroethyl) (3-fluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2,2,2- Trifluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ) Ether, 1,1,2,2-tetrafluoroethyl-n-propyl ether, (1,1,2,2-tetrafluoroethyl) (3-fluoro-n-propyl) ether, (1,1,2) , 2-Tetrafluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (1,1,2,2-Tetrafluoroethyl) (2,2,3,3-tetrafluoro-n-) (Propyl) ether, (1,1,2,2-tetrafluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-propyl Ether, (n-propyl) (3-fluoro-n-propyl) ether, (n-propyl) (3,3,3-trifluoro-n-propyl) ether, (n-propyl) (2,2,3) , 3-Tetrafluoro-n-propyl) ether, (n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3-fluoro-n-propyl) ether, ( 3-Fluoro-n-propyl) (3,3,3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether , (3-Fluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3,3,3-trifluoro-n-propyl) ether, (3,3 3,3-Trifluoro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3) 3,3-Pentafluoro-n-propyl) ether, di (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (2) , 2,3,3,3-pentafluoro-n-propyl) ether, di (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxy Methoxy, methoxy (2-fluoroethoxy) methane, methoxy (2,2,2-trifluoroethoxy) methanemethoxy (1,1,2,2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fluoroethoxy) ) Methoxy, ethoxy (2,2,2-trifluoroethoxy) methane, ethoxy (1,1,2,2-tetrafluoroethoxy) methane, di (2-fluoroethoxy) methane, (2-fluoroethoxy) (2) , 2,2-Trifluoroethoxy) methane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methanedi (2,2,2-trifluoroethoxy) methane, (2,2,2) -Trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methane, di (1,1,2,2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxyethane, methoxy (2-fluoroethoxy) Etan, methoxy (2,2,2-trifluoroethoxy) ethane, methoxy (1,1,2,2-tetrafluoroethane) Xi) ethane, diethoxyethane, ethoxy (2-fluoroethoxy) ethane, ethoxy (2,2,2-trifluoroethoxy) ethane, ethoxy (1,1,2,2-tetrafluoroethoxy) ethane, di (2) -Fluoroethoxy) ethane, (2-fluoroethoxy) (2,2,2-trifluoroethoxy) ethane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (2,2) 2,2-Trifluoroethoxy) ethane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (1,1,2,2-tetrafluoroethoxy) Examples thereof include ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether and diethylene glycol dimethyl ether.

Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1,4-dioxane and the like. And these fluorinated compounds. Among these, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvation ability to lithium ions and are lithium ion dissociable. It is preferable in terms of improving. Particularly preferred are dimethoxymethane, diethoxymethane, and ethoxymethoxymethane because of their low viscosity and high ionic conductivity.
The content of the cyclic ether as the non-aqueous solvent is not particularly limited, but is usually 5% by volume or more in 100% by volume of the non-aqueous solvent, and is usually 50% by volume or less, preferably 30% by volume or less, more preferably. It is 20% by volume or less. The cyclic ether can also be used as an additive in an amount of less than 5% by volume in 100% by volume of the non-aqueous solvent.

<1-3-6. Sulfone compounds>
As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.

Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones, which are monosulfone compounds; and trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones, which are disulfone compounds. Among these, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable, from the viewpoint of dielectric constant and viscosity.

As the sulfolanes, sulfolanes and / or sulfolane derivatives (hereinafter, sulfolanes may be abbreviated as "sulfolanes") are preferable. The sulfolane derivative is preferably one in which one or more hydrogen atoms bonded on the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group.

Among these, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorolane Sulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3 -Methyl sulfolane, 4-fluoro-2-methyl sulfolane, 5-fluoro-3-methyl sulfolane, 5-fluoro-2-methyl sulfolane, 2-fluoromethyl sulfolane, 3-fluoromethyl sulfolane, 2-difluoromethyl sulfolane,
3-Difluoromethyl sulfolane, 2-trifluoromethyl sulfolane, 3-trifluoromethyl sulfolane, 2-fluoro-3- (trifluoromethyl) sulfolane, 3-fluoro-3- (trifluoromethyl) sulfolane, 4-fluoro- 3- (Trifluoromethyl) sulfolane, 5-fluoro-3- (trifluoromethyl) sulfolane and the like are preferable because they have high ionic conductivity and high input / output.

Examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, and n-. Butylmethylsulfone, n-butylethylsulfone, t-butylmethylsulfone, t-butylethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, monofluoroethylmethylsulfone, difluoroethylmethylsulfone, Trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di (tri) Fluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl-n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone , Trifluoroethyl-n-propyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl-t-butyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl-n-propyl sulfone, pentafluoroethyl isopropyl sulfone, tri Fluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, pentafluoroethyl-n-butyl sulfone, pentafluoroethyl-t-butyl sulfone and the like can be mentioned.

Among these, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl. Methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl Pentafluoroethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl -T-Butyl sulfone or the like is preferable because it has high ionic conductivity and high input / output.

The content of the sulfone compound as the non-aqueous solvent is not particularly limited, but is usually 10% by volume or more in 100% by volume of the non-aqueous solvent, and is usually 50% by volume or less, preferably 30% by volume or less, more preferably. Is 20% by volume or less. The sulfone compound can also be used as an additive in an amount of less than 10% by volume in 100% by volume of the non-aqueous solvent.

<1-4. Additives>
In addition to the various compounds listed above, the non-aqueous electrolyte solution used in this embodiment may be used in addition to the various compounds listed above.
Unsaturated cyclic carbonates such as vinylene carbonate, vinylethylene carbonate or ethynylethylene carbonate;
Fluorinated cyclic carbonates such as monofluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,5-difluoroethylene carbonate and 4,5-difluoro-4,5-dimethylethylene carbonate;
Carbonate compounds such as methoxyethyl-methyl carbonate;
Spiro compounds such as methyl-2-propynyl oxalate;
Isocyanate compounds such as diisocyanates having a cycloalkylene group such as 1,3-bis (isocyanatomethyl) cyclohexane;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone;
Hydrocarbon compounds such as cycloheptane;
Fluoro-containing aromatic compounds such as fluorobenzene;
Silane compounds such as tris borate (trimethylsilyl), tris phosphate (trimethylsilyl), tetravinylsilane;
Ester compounds such as 2-propynyl 2- (methanesulfonyloxy) propionic acid;
Lithium salts such as lithium ethyl methyloxycarbonylphosphonate;
Isocyanic acid esters such as triallyl isocyanurate;
Compounds with cyano groups such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, suberonitrile, azelanitrile, sebaconitrile, undecandinitrile, dodecandinitrile, and hexanetricarbonitrile;
Acrylic acid anhydride, 2-methylacrylic acid anhydride, 3-methylacrylic acid anhydride, benzoic acid anhydride, 2-methylbenzoic acid anhydride, 4-methylbenzoic acid anhydride, 4-tert-butyl benzoic acid anhydride Phosphoric acid anhydrides such as 4-fluorobenzoic acid anhydride, 2,3,4,5,6-pentafluorobenzoic acid anhydride, methoxycirate anhydride, ethoxygeic acid anhydride, succinic anhydride, maleic anhydride and the like. Compound;
_{SO 2} structures such as fluorosulfonic acid lithium salt (LiFSO ₃ ), lithium bis (fluorosulfonyl) imide (LiN (FSO ₂ ) ₂ ), methyl methanesulfonate, 1,3-propanesulton, dimethyl sulfate, ethylene sulfate, etc. Compounds;
Compounds having a PF bond such as lithium difluorophosphate; etc. may be added. However, although the lithium difluorophosphate mentioned here corresponds to a lithium salt, it is not treated as an electrolyte from the viewpoint of the degree of ionization with respect to the non-aqueous solvent used in the non-aqueous electrolyte solution, and is positioned as an additive. .. Further, as an overcharge inhibitor, various additives such as cyclohexylbenzene, t-butylbenzene, t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, a partially hydride of terphenyl, diphenyl ether, dibenzofuran and the like are effective in the present invention. Can be blended within a range that does not significantly impair. These compounds may be used in combination as appropriate.

In the non-aqueous electrolyte solution used in the present embodiment, as a particularly preferable additive having a particularly high addition effect and synergistically exerting the effect, (A) a compound having a PF bond and (B) SO ₂ structure are used. Examples include compounds having. It is considered that these are incorporated in the polymerization process of the isocyanate compound represented by the formula (1) or the formula (2) to further suppress the side reaction at the positive electrode while suppressing the input resistance and improve the initial charge / discharge efficiency. Be done.

<1-4-1. (A) Compound having PF bond>
The compound (A) having a PF bond is not particularly limited as long as it has a PF bond in the molecule, and any compound can be used as long as the effect of the present invention is not significantly impaired. Among them, a phosphate having a PF bond is preferable. The counter cation of the phosphate having a PF bond is not particularly limited, but lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR ¹³ R ¹⁴ R ¹⁵ R ¹⁶ (in the formula, Examples of R ^{13 to} R ¹⁶ include ammonium represented by a hydrogen atom or an organic group having 1 to 12 carbon atoms independently. Among them, lithium is particularly preferable. Moreover, since the oxidation potential increases, the number of PF bonds contained in the molecule is preferably 2 or more. Specifically, lithium difluorobis (oxalate) phosphate and lithium difluorophosphate are particularly preferable.
As the compound having a PF bond, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the compound having a PF bond is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.001% by mass or more in 100% by mass of the non-aqueous electrolyte solution. It is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less. Most preferably, it is 1% by mass or less.
When the content of the compound having a PF bond is within this range, it is possible to increase the initial charge / discharge efficiency while suppressing the input resistance of the non-aqueous electrolyte secondary battery.

<1-4-2. (B) Compound having _{SO 2 structure>}
The compound having a (B) SO ₂ structure is not particularly limited as long as it is a compound having a SO ₂ structure in the molecule, unless significantly impairing the effects of the present invention, may be any ones. Among them, a lithium salt having _{an SO 2} structure or an ester compound having an _{SO 2 structure is preferable.}
As a lithium salt having an _{SO 2 structure,}
Fluorosulfuric acid lithium salt (LiFSO ₃ );
Lithium bis (fluorosulfonyl) imide _{(LiN (FSO 2) 2)} , LiN (F S O 2) (CF 3 SO 2), fluorosulfonyl imide salts such as _{LiN (CF 3 SO 2) 2} ;
Fluorosulfonyl methidolithium salts such as LiC (FSO ₂ ) _3;
Fluorosulfonylborate lithiums such as LiBF ₃ (FSO ₃ ) and LiB (FSO ₂ ) ₄ ; and the like.
Further, _{among the compounds having an SO 2} structure, a Li salt having an FS bond is preferable. _{Among them, LiFSO 3} and LiN (FSO ₂ ) ₂ are particularly preferable because they have a small molecular structure and can easily approach the vicinity of the positive electrode.
As an ester having an _{SO 2 structure,}
Chain sulfonic acid esters such as methyl methanesulfonate and ethyl methanesulfonate;
Cyclic sulfonic acid esters such as 1,3-propane sultone and 1-propene 1,3-sultone;
Chain sulfate esters such as dimethyl sulfate and diethyl sulfate;
Cyclic sulfate esters such as ethylene sulfate and propylene sulfate; and the like.
Among the compounds having an SO ₂ structure, those having 2 to 10 carbon atoms are preferable, and further, since the molecular structure is small and it is easy to approach the vicinity of the positive electrode, a chain sulfonic acid ester having 2 to 4 carbon atoms, From the viewpoint of structural stability, a chain sulfate ester having 2 to 4 carbon atoms, a cyclic sulfonic acid ester having 3 to 4 carbon atoms, and a cyclic sulfate ester having 2 to 3 carbon atoms are particularly preferable. More preferably, it is a cyclic sulfonic acid ester having 3 to 4 carbon atoms and a cyclic sulfate ester having 2 to 3 carbon atoms, and specifically, 1,3-propanesulton and ethylene sulfate.
As the _{compound having an SO 2} structure, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the compound having an SO ₂ structure is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.001% by mass or more, preferably 0.001% by mass or more in 100% by mass of the non-aqueous electrolyte solution. 0.01% by mass or more, more preferably 0.1% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, most preferably 1% by mass or less. be.
When _{the content of the compound having the SO 2} structure is within this range, it is possible to increase the initial charge / discharge efficiency while suppressing the input resistance of the non-aqueous electrolyte secondary battery.
However, LiN (FSO ₂ ) ₂ may be used as the main salt, and in that case, the content is not limited to the above. Further, for example, a compound having an SO ₂ structure such as a sulfone compound may be used as a non-aqueous solvent, and in that case, the content is not limited to the above.

As described above, the non-aqueous electrolyte solution according to the present embodiment _{preferably contains at least one of (A) a compound having a PF bond and (B) a compound having an SO 2} structure, and (A) P-. A compound having an F bond and a compound having a (B) SO ₂ structure may be used in combination of two or more. When a compound having at least one kind of (A) PF bond and a compound having at least one kind of (B) SO ₂ structure are combined, the effect of increasing the initial charge / discharge efficiency of the non-aqueous electrolyte battery is more remarkable. It is preferable because it becomes a simple compound.
Further, in the non-aqueous electrolyte solution according to the present embodiment, by using one or more selected from unsaturated cyclic carbonates and cyclic carbonates having a fluorine atom in combination, gas generation during initial conditioning is further suppressed and swelling is less likely to occur. It is preferable in that a battery can be obtained.
Hereinafter, the "unsaturated cyclic carbonate" and the "fluorinated cyclic carbonate" will be described in detail.

<1-4-3. Unsaturated cyclic carbonate>
As used herein, the "unsaturated cyclic carbonate" is a cyclic carbonate having a carbon-carbon unsaturated bond, and is a carbonate having a carbon-carbon unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond. If there is, any unsaturated cyclic carbonate can be used without particular limitation.
Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with a substituent having a carbon-carbon unsaturated bond, and the like.
Specific examples of vinylene carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate and the like.
Specific examples of ethylene carbonates substituted with a substituent having a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinylethylene carbonate, ethynylethylene carbonate, propargylethylene carbonate and the like.
Of these, vinylene carbonate, vinylethylene carbonate, and ethynylethylene carbonate are preferable, and vinylene carbonate in particular can contribute to the formation of a stable film-like structure and is more preferably used.
The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. Within this range, the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolyte solution can be easily ensured, and the effect of the present invention can be sufficiently exhibited.
As the unsaturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but the content of the unsaturated cyclic carbonate is usually 0 in 100% by mass of the non-aqueous electrolyte solution. .001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and usually 10% by mass or less. , It is preferably 8% by mass or less, and more preferably 5% by mass or less. When the content of the unsaturated cyclic carbonate is within the above range, the non-aqueous electrolyte secondary battery tends to exhibit sufficient high-temperature storage characteristics and cycle characteristic improving effects.

<1-4-4. Fluorinated cyclic carbonate>
As used herein, the term "fluorinated cyclic carbonate" is a cyclic carbonate having a fluorine atom.
Examples of the fluorinated cyclic carbonate include derivatives of cyclic carbonate having an alkylene group having 2 to 6 carbon atoms, and examples thereof are ethylene carbonate derivatives. Examples of the ethylene carbonate derivative include ethylene carbonate or a fluorinated product of ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms), and among them, those having 1 to 8 fluorine atoms. Is preferable.
Specifically, monofluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4- Fluoro-
5-Methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate, 4 -(Fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethylethylene carbonate , 4,4-Difluoro-5,5-dimethylethylene carbonate and the like.
Among them, at least one selected from the group consisting of monofluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,5-difluoroethylene carbonate and 4,5-difluoro-4,5-dimethylethylene carbonate is highly ionic conductive. It is more preferable in that it imparts properties and preferably forms an interface protective film.
As the fluorinated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.
The fluorinated cyclic carbonate may be used as an additive for a non-aqueous electrolyte solution or as a non-aqueous solvent. The content of the fluorinated cyclic carbonate when used as a non-aqueous solvent is usually 8% by mass or more, preferably 10% by mass or more, and more preferably 12% by mass or more in 100% by mass of the non-aqueous electrolyte solution. Yes, it is usually 85% by mass or less, preferably 80% by mass or less, and more preferably 75% by mass or less. Within this range, the non-aqueous electrolyte secondary battery tends to exhibit a sufficient effect of improving the cycle characteristics, and it is easy to avoid a decrease in the discharge capacity retention rate. The content of the fluorinated cyclic carbonate when used as an additive is usually 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably 0.1% by mass in 100% by mass of the non-aqueous electrolyte solution. % Or more, more preferably 0.2% by mass or more, and usually 10% by mass or less, preferably 8% by mass or less, and more preferably 5% by mass or less. When the content of the fluorinated cyclic carbonate is within the above range, the non-aqueous electrolyte secondary battery tends to exhibit sufficient high-temperature storage characteristics and cycle characteristic improving effects.
In the non-aqueous electrolyte solution according to the embodiment of the present invention, the unsaturated cyclic carbonate or the fluorinated cyclic carbonate is at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, ethynylethylene carbonate, and fluoroethylene carbonate. It is preferably a seed.

As the fluorinated cyclic carbonate, a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter, may be abbreviated as "fluorinated unsaturated cyclic carbonate") can be used. The fluorinated unsaturated cyclic carbonate is not particularly limited. Of these, those having one or two fluorine atoms are preferable. The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected for production.
Examples of the fluorinated unsaturated cyclic carbonate include a vinylene carbonate derivative, an ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon unsaturated bond, and the like.
Examples of the vinylene carbonate derivative include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4,5-difluoroethylene carbonate and the like.
Examples of the ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon unsaturated bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, and 4,4-difluoro-4. -Vinylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4-fluoro-4-phenyl Examples thereof include ethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate and the like.
The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. Is. Within this range, it is easy to secure the solubility of the fluorinated cyclic carbonate in the non-aqueous electrolyte solution, and the effect of the present invention is likely to be exhibited.
As the fluorinated unsaturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The amount of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by mass or more, preferably 0.01% by mass or more in 100% by mass of the non-aqueous electrolyte solution. Is 0.1% by mass or more, more preferably 0.2% by mass or more, and usually 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less. Within this range, the non-aqueous electrolyte secondary battery tends to exhibit a sufficient effect of improving cycle characteristics.

The content of additives other than (A) a compound having an PF bond, (B) _{a compound having an SO 2} structure, an unsaturated cyclic carbonate and a fluorinated cyclic carbonate is not particularly limited, and the effect of the present invention is remarkably enhanced. It is optional as long as it is not impaired, but is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and usually, with respect to the total amount of the non-aqueous electrolyte solution. It is 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. Within this range, the effects of other additives are likely to be sufficiently exhibited, and high-temperature storage stability tends to be improved. When two or more additives other than (A) a compound having an PF bond, (B) _{a compound having an SO 2} structure, an unsaturated cyclic carbonate and a fluorinated cyclic carbonate are used in combination, the total amount of these additives Should satisfy the above range.

In the present specification, the composition of the non-aqueous electrolyte solution means the composition at the time of producing the non-aqueous electrolyte solution, at the time of injecting the non-aqueous electrolyte solution into the battery, or at the time of shipment as the battery.
That is, the non-aqueous electrolyte solution may be mixed so that the ratio of each component is a predetermined composition when the non-aqueous electrolyte solution is prepared. Further, after preparing the non-aqueous electrolyte solution, the non-aqueous electrolyte solution itself can be subjected to analysis to confirm the composition. Further, the non-aqueous electrolyte solution may be recovered from the completed non-aqueous electrolyte solution secondary battery and used for analysis. Examples of the method for recovering the non-aqueous electrolyte solution include a method of collecting the electrolytic solution by opening a part or all of the battery container or providing a hole in the battery container. The opened battery container may be centrifuged to recover the electrolytic solution, or an extraction solvent (for example, acetonitrile dehydrated to a water content of 10 ppm or less is preferable) is placed in the opened battery container or extracted into a battery element. The electrolytic solution may be extracted by contacting the solvent. The non-aqueous electrolyte solution recovered by such a method can be used for analysis. Further, the recovered non-aqueous electrolyte solution may be diluted and subjected to analysis in order to make the conditions suitable for analysis.

Specific examples of the method for analyzing a non-aqueous electrolyte solution include analysis by nuclear magnetic resonance (hereinafter, may be abbreviated as NMR), liquid chromatography such as gas chromatography and ion chromatography, and the like. Hereinafter, the analysis method by NMR will be described. Under an inert atmosphere, the non-aqueous electrolyte solution is dissolved in a deuterated solvent dehydrated to 10 ppm or less, placed in an NMR tube, and NMR measurement is performed. Further, a double tube may be used as the NMR tube, a non-aqueous electrolyte solution may be put in one, and a deuterated solvent may be put in the other to perform NMR measurement. Examples of the deuter solvent include diacetonitrile and deuterated dimethyl sulfoxide. When determining the concentration of a component of a non-aqueous electrolyte solution, a specified amount of a standard substance can be dissolved in a deuterated solvent, and the concentration of each component can be calculated from the ratio of the spectrum. Further, the concentration of one or more of the components constituting the non-aqueous electrolyte solution is obtained in advance by another analysis method such as gas chromatography, and the concentration is calculated from the spectral ratio of the component having a known concentration and the other components. You can also do it. The nuclear magnetic resonance analyzer used is preferably one having a magnetic field of 400 MHz or more. Examples of the nuclide to be measured include ¹ H, ³¹ P, ¹⁹ F and the like.
One type of these analysis methods may be used alone, or two or more types may be used in combination.

<2. Non-aqueous electrolyte secondary battery ＞
The non-aqueous electrolyte secondary battery according to an embodiment of the present invention is dissolved in a positive electrode capable of storing and releasing metal ions, a negative electrode capable of storing and releasing metal ions, a non-aqueous solvent, and the non-aqueous solvent. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte solution containing an electrolyte, wherein the positive electrode contains a transition metal oxide and at least Ni and Co are contained as transition metals, and among the transition metals. 40 mol% or more is Ni, the negative electrode contains a carbon-based material, and the non-aqueous electrolyte solution is selected from the compound represented by the above general formula (1) and the compound represented by the general formula (2). Contains at least one isocyanate compound.

<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery of the present embodiment is the same as the conventionally known non-aqueous electrolyte secondary battery except for the above-mentioned non-aqueous electrolyte and the positive electrode and the negative electrode. Usually, the positive electrode and the negative electrode are laminated via a porous film (separator) impregnated with the above-mentioned non-aqueous electrolyte solution, and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery of the present embodiment is not particularly limited, and may be any of a cylindrical type, a square type, a laminated type, a coin type, a large size, and the like.

<2-2. Non-aqueous electrolyte solution>
As the non-aqueous electrolyte solution, the non-aqueous electrolyte solution according to the above-described embodiment of the present invention is used. It is also possible to mix and use another non-aqueous electrolyte solution with the above non-aqueous electrolyte solution as long as the gist of the present invention is not deviated.

<2-3. Positive electrode>
In one embodiment of the present invention, the positive electrode has a current collector and a positive electrode active material layer provided on the current collector.
The positive electrode used in the non-aqueous electrolyte secondary battery of the present embodiment will be described in detail below.

<2-3-1. Positive electrode active material>
The positive electrode active material used for the positive electrode will be described below.
(1) Composition The positive electrode active material is a transition metal oxide capable of occluding and releasing metal ions, and contains at least Ni and Co as the transition metal, and 40 mol% or more of the transition metal is Ni. For example, it is preferable that lithium ions can be occluded and released electrochemically, and it is preferable that lithium, at least Ni and Co are contained, and 50 mol% or more of the transition metal is Ni, and 60 mol% or more is Ni. Is more preferable. This is because Ni and Co have a redox potential suitable for use as a positive electrode material for a secondary battery and are suitable for high-capacity applications.

The transition metal component of the lithium transition metal oxide includes Ni and Co as essential elements, but other metals include Mn, V, Ti, Cr, Fe, Cu, Al, Mg, Zr, Er and the like. Mn, Ti, Fe, Al, Mg, Zr and the like are preferable. Specific examples of the lithium transition metal oxide include LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.80 Co _0.15 Al _0.05 O ₂ , and LiNi _0.8 Co _{0. 1} Mn _0.1 O _2, LiNi _0.7 Co _0.15 Mn _0.15 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O _2, LiNi _0.5 Co _0.2 Mn _{0 .3} O ₂ , LiNi _0.5 Co _0.3 Mn _0.2 O ₂ , Li _1.05 Ni _0.50 Co _0.21 Mn _0.29 O ₂ , LiNi _0.5 Co _0.3 Mn _0. Examples thereof include ₂ O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O _2.

Above all, the aspect of the transition metal oxide represented by the following composition formula (α) is preferable.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ ... (α)
(In the above formula (α), a1, b1, c1 and d1 satisfy 0.90 ≦ a1 ≦ 1.10, 0.4 ≦ b1 <1.0, b1 + c1 + d1 = 1. M is Mn, Al, Mg. , Zr, Fe, Ti and Er represents at least one element selected from the group.
In the composition formula (α), it is preferable to show a value of 0.10 ≦ d1 <0.40. Further, it is preferable to show a numerical value of 0.50 ≦ b1 ≦ 0.96.
Since Ni and Co are the main components and the composition ratio of Ni is larger than the composition ratio of Co, it is possible to take out a stable and high capacity when used as a positive electrode of a non-aqueous electrolyte battery. Because it becomes.

Above all, the embodiment of the transition metal oxide represented by the following composition formula (β) is preferable.
Li _a2 Ni _b2 Co _c2 M _d2 O ₂ ... (β)
(In the formula (β), the numerical values of 0.90 ≦ a2 ≦ 1.10, 0.50 ≦ b2 ≦ 0.94, 0.05 ≦ c2 ≦ 0.2, and 0.01 ≦ d2 ≦ 0.3 are shown. , B2 + c2 + d2 = 1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
In the composition formula (β), it is preferable to show a numerical value of 0.10 ≦ d2 ≦ 0.3.
This is because the above composition makes it possible to take out a particularly high capacity when used as a positive electrode of a non-aqueous electrolyte secondary battery.

Further, two or more of the above-mentioned positive electrode active materials may be mixed and used. Similarly, at least one or more of the above positive electrode active materials may be mixed and used with other positive electrode active materials. Examples of other positive electrode active materials include transition metal oxides, transition metal phosphoric acid compounds, transition metal silicic acid compounds, and transition metal boric acid compounds not listed above.
Of these, a lithium manganese composite oxide having a spinel-type structure and a lithium-containing transition metal phosphoric acid compound having an olivine-type structure are preferable. Specific examples of the lithium manganese composite oxide having a spinel-type structure include LiMn ₂ O ₄ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4, and the} like. This is because the structure is the most stable, oxygen is not easily released even when the non-aqueous electrolyte battery is abnormal, and the safety is excellent.
The transition metal of the lithium-containing transition metal phosphoric acid compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples thereof include LiFePO ₄ and Li ₃ Fe ₂ (PO _4). ) ₃ , Iron phosphates such as _{LiFeP 2} O ₇ , cobalt phosphates such as _{LiCoPO 4 , manganese phosphates such as LiMnPO 4} , and some of the transition metal atoms that are the main constituents of these lithium transition metal phosphoric acid compounds are Al and Ti. , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and the like.
Of these, a lithium iron phosphoric acid compound is preferable. This is because iron is an extremely inexpensive metal with abundant resources and is less harmful. That is, among the above specific examples, LiFePO ₄ can be mentioned as a more preferable specific example.

In one embodiment of the present invention, the positive electrode is an NMC positive electrode, and the nickel element content in the NMC positive electrode is 40 mol% or more and 50 mol% or more. It is more preferable from the viewpoint of increasing the capacity.
Here, in the present specification, the NMC positive electrode means a positive electrode in which the positive electrode active material contains nickel, manganese, and cobalt (NMC) and is a material represented by the following formula (I).
Li _a Ni _b Co _c Mn _d O ₂ ... (I)
(In the above formula (I), a, b, c and d satisfy 0.90 ≦ a ≦ 1.10, 0.40 ≦ b <1.0, b + c + d = 1.)

(2) Surface Coating A substance having a composition different from that of the substance constituting the main positive electrode active material (hereinafter, appropriately referred to as “surface adhering substance”) may be used on the surface of the above-mentioned positive electrode active material. .. Examples of surface adhering substances include oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, etc. Sulfates such as calcium sulfate and aluminum sulfate; carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate; carbon and the like can be mentioned.

These surface-adhering substances are, for example, dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and then dried, or the surface-adhering substance precursor is dissolved or suspended in the solvent and impregnated and added to the positive electrode active material. After that, it can be adhered to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing at the same time, or the like. When carbon is attached, a method of mechanically attaching the carbon substance later in the form of activated carbon or the like can also be used.

The mass of the surface-adhering substance adhering to the surface of the positive electrode active material is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, based on the mass of the positive electrode active material. Further, it is preferably 20% or less, more preferably 10% or less, still more preferably 5% 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. Further, when the amount of adhesion is within the above range, the effect can be sufficiently exhibited, and the resistance is less likely to increase without hindering the inflow and outflow of lithium ions.

(3) Shape As the shape of the positive electrode active material particles, a lump, a polyhedral shape, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a columnar shape, or the like, which are conventionally used, are used. Further, the primary particles may be aggregated to form secondary particles, and the shape of the secondary particles may be spherical or elliptical spherical.

(4) Method for Producing Positive Electrode Active Material The method for producing the positive electrode active material is not particularly limited as long as it does not exceed the gist of the present invention, but some methods are mentioned and are general as a method for producing an inorganic compound. The method is used.
In particular, various methods can be considered for producing spherical or elliptical spherical active materials. For example, one example thereof is a transition metal raw material such as transition metal nitrate or sulfate, and if necessary, a raw material of other elements. Is dissolved or pulverized and dispersed in a solvent such as water, the pH is adjusted while stirring to prepare and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , Li NO. Examples thereof include a method of adding a Li source such as _{3 and firing at a high temperature to obtain an active material.}

Further, as an example of another method, a transition metal raw material such as a transition metal nitrate, a sulfate, a hydroxide, or an oxide and, if necessary, a raw material of another element are dissolved or pulverized and dispersed in a solvent such as water. Then, it is dried and molded with a spray dryer or the like to form a spherical or elliptical spherical precursor, to which _{a Li source such as LiOH, Li 2} CO ₃ or LiNO ₃ is added and fired at a high temperature to obtain an active material. Can be mentioned.

As an example of yet another method, a transition metal raw material such as a transition metal nitrate, a sulfate, a hydroxide, an oxide, _{a Li source such as LiOH, Li 2} CO ₃ , or LiNO ₃ , and other elements as required. Is a method of dissolving or pulverizing and dispersing the raw material of the above in a solvent such as water, drying and molding it with a spray dryer or the like to obtain a spherical or elliptical spherical precursor, and firing this at a high temperature to obtain an active material. Can be mentioned.

<2-3-2. Positive electrode structure and manufacturing method>
Hereinafter, the configuration of the positive electrode used in the present invention and the method for producing the same will be described.
(Method of manufacturing positive electrode)
The positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. The positive electrode using the positive electrode active material can be produced by any known method. For example, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener are mixed in a dry manner to form a sheet, which is then pressure-bonded to the positive electrode current collector, or these materials are applied to a liquid medium. 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.

The content of the positive electrode active material in the positive electrode active material layer is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and preferably 99.9% by mass or less. Yes, 99% by mass or less is more preferable. When the content of the positive electrode active material is within the above range, a sufficient electric capacity can be secured. Further, the strength of the positive electrode is also sufficient. The positive electrode active material powder in the present invention may contain at least Ni and Co as a transition metal, and if a positive electrode in which 40 mol% or more of the transition metal is Ni is produced, one type may be used alone. Often, two or more kinds having different compositions or different powder physical properties may be used in any combination and ratio.

<Conductive material>
As the conductive material, a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbon-based materials such as amorphous carbon such as needle coke. It should be noted that one of these may be used alone, or two or more thereof may be used in any combination and ratio.

The content of the conductive material in the positive electrode active material layer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 1% by mass or more, and preferably 50% by mass or less. It is more preferably 30% by mass or less, and further preferably 15% by mass or less. When the content of the conductive material is within the above range, sufficient conductivity can be ensured. Furthermore, it is easy to prevent a decrease in battery capacity.

<Binder>
The binder used in the production of the positive electrode active material layer is not particularly limited as long as it is a material stable to the non-aqueous electrolyte solution and the solvent used in the production of the electrode.
In the case of the coating method, the material is not particularly limited as long as it is a material that is dissolved or dispersed in the liquid medium used at the time of electrode production, but specific examples thereof include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, and cellulose. , Resin-based polymer such as nitrocellulose; rubber-like polymer such as SBR (styrene / butadiene rubber), NBR (acrylonitrile / butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene / propylene rubber; styrene / butadiene / Styrene block copolymer or hydrogen additive thereof, EPDM (ethylene / propylene / diene ternary copolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogen additive thereof Thermoplastic elastomeric polymers such as syndiotactic-1,2-polybutadiene, polyvinylacetate, ethylene / vinyl acetate copolymer, soft resinous polymer such as propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, tetrafluoroethylene / ethylene copolymer and other fluoropolymers; polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions); and the like. In addition, as these substances, 1 type may be used alone, and 2 or more types may be used together in arbitrary combinations and ratios.

The content of the binder in the positive electrode active material layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, further preferably 3% by mass or more, and preferably 80% by mass or less. Yes, 60% by mass or less is more preferable, 40% by mass or less is further preferable, and 10% by mass or less is particularly preferable. When the ratio of the binder is within the above range, the positive electrode active material can be sufficiently retained and the mechanical strength of the positive electrode can be ensured, so that the battery performance such as cycle characteristics is improved. Furthermore, it also leads to avoiding a decrease in battery capacity and conductivity.

<Liquid medium>
As the liquid medium used for preparing the slurry for forming the positive electrode active material layer, the positive electrode active material, the conductive material, the binder, and the thickener used as needed can be dissolved or dispersed. The type of solvent is not particularly limited, 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 organic media 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, methylethylketone and cyclohexanone. Classes; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine, N, N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP), dimethylformamide. , Amides such as dimethylacetamide; aprotonic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide can be mentioned. It should be noted that one of these may be used alone, or two or more thereof may be used in any combination and ratio.

<Thickener>
When an aqueous medium is used as the liquid medium for forming the slurry, it is preferable to use a thickener and a latex such as styrene-butadiene rubber (SBR) to form a slurry. Thickeners are commonly used to adjust the viscosity of the slurry.
The thickener is not limited as long as the effect of the present invention is not significantly limited, but specifically, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. And so on. These may be used alone or in any combination and ratio of two or more.

When a thickener is used, the ratio of the thickener to the positive electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 0.6% by mass or more. It is preferable, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less. When the ratio of the thickener to the positive electrode active material is within the above range, the coating property of the slurry is good, and the ratio of the active material to the positive electrode active material layer is sufficient, so that the capacity of the battery is reduced. It becomes easy to avoid the problem of increasing the resistance between the positive electrode active materials and the problem of increasing the resistance between the positive electrode active materials.

<Consolidation>
The positive electrode active material layer obtained by applying and drying the slurry to the current collector 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. The density of the positive electrode active material layer ^{is preferably 1 g · cm -3} or more, more preferably 1.5 g · cm ^-3 or more, further preferably 2 g · cm ^-3 or more, and preferably 4 g · cm ^-3 or less. 3.5 g · cm ^-3 or less is more preferable, and 3 g · cm ^-3 or less is further preferable.
When the density of the positive electrode active material layer is within the above range, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface does not decrease, and the charge / discharge characteristics are particularly good at a high current density. Become. Further, the conductivity between the active materials is less likely to decrease, and the battery resistance is less likely to increase.

<Current collector>
The material of the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; carbon-based materials such as carbon cloth and carbon paper; and the like. Of these, metal materials, especially aluminum, are preferable.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foamed metal, etc. in the case of metal material, and carbon plate in the case of carbon-based material. Examples include a carbon thin film and a carbon column. Of these, a metal thin film is preferable. The thin film may be formed in a mesh shape as appropriate.
The thickness of the current collector is arbitrary, but is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, and preferably 1 mm or less, more preferably 100 μm or less, further preferably 50 μm or less. preferable. When the thickness of the current collector is within the above range, sufficient strength required for the current collector can be secured. Further, the handleability is also good.

The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but (thickness of the active material layer on one side immediately before the injection of the non-aqueous electrolyte solution) / (thickness of the current collector) is preferable. It is 150 or less, more preferably 20 or less, particularly preferably 10 or less, and preferably 0.1 or more, more preferably 0.4 or more, and particularly preferably 1 or more.
When the ratio of the thickness of the current collector to the positive electrode active material layer is within the above range, the current collector is less likely to generate heat due to Joule heat during high current density charging / discharging. Further, the volume ratio of the current collector to the positive electrode active material is unlikely to increase, and a decrease in battery capacity can be prevented.

<Electrode area>
From the viewpoint of improving the stability at high output and high temperature, the area of the positive electrode active material layer is preferably large with respect to the outer surface area of the battery outer case. Specifically, the total area of the electrodes of the positive electrode with respect to the surface area of the exterior of the non-aqueous electrolyte battery is preferably 20 times or more, and more preferably 40 times or more in terms of area ratio. The outer surface area of the outer case means the total area calculated 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 the 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 a structure in which the positive electrode mixture layer is formed on both sides via a current collector foil. , Refers to the sum of the areas calculated separately for each surface.

<Discharge capacity>
When the above non-aqueous electrolyte solution is used, the electric capacity (electrical capacity when the battery is discharged from a fully charged state to a discharged state) of the battery element housed in one battery exterior of the non-aqueous electrolyte battery is determined. When it is 1 amper hour (Ah) or more, the effect of improving the low temperature discharge characteristics becomes large, which is preferable. Therefore, the positive electrode (also referred to as “positive electrode plate”) has a fully charged discharge capacity, preferably 3 Ah (ampere hour) or more, more preferably 4 Ah or more, and preferably 100 Ah or less, more preferably 100 Ah or less. It is designed to be 70 Ah or less, particularly preferably 50 Ah or less.

Within the above range, the voltage drop due to the electrode reaction resistance does not become too large when a large current is taken out, and deterioration of power efficiency can be prevented. Furthermore, the temperature distribution due to internal heat generation of the battery during pulse charging / discharging does not become too large, the durability of repeated charging / discharging is inferior, and the heat dissipation efficiency is poor against sudden heat generation at the time of abnormalities such as overcharging and internal short circuit. It is possible to avoid the phenomenon of becoming.

<Thickness of positive electrode plate>
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity, high output, and high rate characteristics, the thickness of the positive electrode active material layer obtained by subtracting the thickness of the current collector from the positive electrode plate is the thickness of the current collector. With respect to one side, 10 μm or more is preferable, 20 μm or more is more preferable, 200 μm or less is preferable, and 100 μm or less is more preferable.

<2-4. Negative electrode ＞
In one embodiment of the present invention, the negative electrode has a current collector and a negative electrode active material layer provided on the current collector.
The negative electrode used in the non-aqueous electrolyte secondary battery of the present embodiment will be described in detail below.

<2-4-1. Negative electrode active material>
The negative electrode active material used for the negative electrode will be described below. The negative electrode active material includes a carbon-based material that can electrochemically occlude and release metal ions. One type of negative electrode active material may be used alone, or two or more types may be used in any combination.

<Carbon-based material>
Examples of the carbon-based material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. Be done.

(1) Examples of natural graphite include scaly graphite, scaly graphite, soil graphite and / or graphite particles obtained by subjecting these graphites to a treatment such as spheroidization or densification. Among these, spherical or ellipsoidal graphite that has been subjected to a spheroidizing treatment is particularly preferable from the viewpoint of particle packing property and charge / discharge rate characteristics.

As the device used for the spheroidizing process, for example, a device that repeatedly applies mechanical actions such as compression, friction, and shearing force to the particles, including the interaction of the particles mainly with an impact force, can be used.

Specifically, it has a rotor with a large number of blades installed inside the casing, and by rotating the rotor at high speed, impact compression, friction, and shearing force are applied to the raw material of natural graphite (1) introduced inside. A device that gives a mechanical action such as, etc. to perform the spheroidizing process is preferable. Further, an apparatus having a mechanism for repeatedly giving a mechanical action by circulating a raw material is preferable.

For example, in the case of sphericalizing using the above-mentioned device, the peripheral speed of the rotating rotor is preferably set to 30 to 100 m / sec, more preferably 40 to 100 m / sec, and 50 to 100 m / sec. It is even more preferable to set it to seconds. Further, the spheroidizing treatment can be performed by simply passing the raw material through the device, but it is preferable to circulate or retain the inside of the device for 30 seconds or more, and to circulate or stay in the device for 1 minute or more. Is more preferable.

(2) As artificial graphite, coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, etc. Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene silfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin are usually used in the range of 2500 ° C or higher and usually 3200 ° C or lower. Examples thereof include those produced by graphitization at temperature, crushing and / or classifying as necessary.

At this time, a silicon-containing compound, a boron-containing compound, or the like can also be used as a graphitization catalyst. In addition, artificial graphite obtained by graphitizing mesocarbon microbeads separated in a pitch heat treatment process can be mentioned. Further, artificial graphite of granulated particles composed of primary particles can also be mentioned. For example, mesocarbon microbeads, graphitizable carbon-based material powder such as coke, graphitizable binder such as tar and pitch, and graphitization catalyst are mixed, graphitized, and pulverized if necessary. Examples thereof include graphite particles obtained by assembling or bonding a plurality of flat particles so that the orientation planes are non-parallel.

(3) As the amorphous carbon, an easily graphitizable carbon precursor such as tar or pitch is used as a raw material, and the amorphous carbon is heat-treated at least once in a temperature range (range of 400 to 2200 ° C.) where graphitization does not occur. Examples thereof include particles and amorphous carbon particles heat-treated using a non-graphitizable carbon precursor such as a resin as a raw material.

(4) Examples of the carbon-coated graphite include those obtained as follows. Natural graphite and / or artificial graphite is mixed with a carbon precursor which is an organic compound such as tar, pitch or resin, and heat-treated at least once in the range of 400 to 2300 ° C. The obtained natural graphite and / or artificial graphite is used as nuclear graphite, and this is coated with amorphous carbon to obtain a carbon graphite composite. This carbon-graphite composite is mentioned as carbon-coated graphite (4).

Further, the composite form is a form in which a plurality of primary particles are composited using carbon derived from the carbon precursor as a binder even when the entire surface or a part of the surface of nuclear graphite is coated with amorphous carbon. You may. It is also possible to react natural graphite and / or artificial graphite with a hydrocarbon gas such as benzene, toluene, methane, propane, or an aromatic volatile matter at a high temperature to deposit carbon on the graphite surface (CVD). The carbon graphite composite can be obtained.

(5) As the graphite-coated graphite, those obtained as follows can be mentioned. Natural graphite and / or artificial graphite is mixed with a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin, and heat-treated at least once in the range of about 2400 to 3200 ° C. The obtained natural graphite and / or artificial graphite is used as nuclear graphite, and the whole or part of the surface of the nuclear graphite is coated with graphite to obtain graphite-coated graphite (5).

(6) As the resin-coated graphite, for example, natural graphite and / or artificial graphite obtained by mixing natural graphite and / or artificial graphite with a resin or the like and drying at a temperature of less than 400 ° C. is used as nuclear graphite, and the resin or the like is used. It is obtained by coating the nuclear graphite with.

Further, the carbon-based materials (1) to (6) described above may be used alone or in any combination and ratio of two or more.

Examples of the organic compounds such as tar, pitch and resin used for the carbon-based materials (2) to (5) above include coal-based heavy oil, DC-based heavy oil, decomposition-based petroleum heavy oil, and aromatic hydrocarbons. , N-ring compounds, S-ring compounds, polyphenylenes, synthetic organic polymers, natural polymers, thermoplastic resins, thermosetting resins and the like, which are carbonizable organic compounds selected from the group. Further, the raw material organic compound may be used by being dissolved in a small molecule organic solvent in order to adjust the viscosity at the time of mixing.

Further, as the natural graphite and / or the artificial graphite which is a raw material of the nuclear graphite, the natural graphite which has been subjected to the spheroidizing treatment is preferable.

<Negative electrode active material containing metal particles and graphite particles that can be alloyed with Li>
The negative electrode active material may contain metal particles that can be alloyed with Li and graphite particles. In the present specification, the "metal particles that can be alloyed with Li" are "particles containing a metal element and / or a metalloid element that can be alloyed with Li", as is clear from the specifically exemplified materials. Means. The negative electrode active material containing Li and alloyable metal particles and graphite particles may be a mixture in which Li and alloyable metal particles and graphite particles are mixed in the state of mutually independent particles, or Li. It may be a composite in which metal particles that can be alloyed with are present on the surface and / or inside of the graphite particles.

The composite of the metal particles that can be alloyed with Li and the graphite particles (also referred to as composite particles) is not particularly limited as long as the particles contain the metal particles that can be alloyed with Li and the graphite particles. , Preferably, the metal particles and graphite particles that can be alloyed with Li are integrated by physical and / or chemical bonding. In a more preferable form, the metal particles and graphite particles that can be alloyed with Li are present in the particles in a dispersed manner so that the metal particles and graphite particles are present at least on the surface of the composite particles and inside the bulk. It is in the form in which graphite particles are present to unite them by physical and / or chemical bonding. A more specific preferred form is a composite material composed of at least Li and alloyable metal particles and graphite particles, in which the graphite particles, preferably natural graphite, have a curved structure and have a folded structure. In addition, it is a composite material (negative electrode active material) characterized in that metal particles that can be alloyed with Li are present in the gaps in the structure. Further, the gap may be a void, and a substance such as amorphous carbon, a graphitic substance, or a resin that buffers the expansion and contraction of metal particles that can be alloyed with Li exists in the gap. You may.

(Content ratio of metal particles that can be alloyed with Li)
The content ratio of the metal particles that can be alloyed with Li to the total of the metal particles that can be alloyed with Li and the metal particles that can be alloyed with Li is usually 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 1. It is 0% by mass or more, more preferably 2.0% by mass or more. Further, it is usually 99% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 25% by mass or less, still more preferably 20% by mass or less, particularly. It is preferably 15% by mass or less, and most preferably 10% by mass or less. Within this range, side reactions on the Si surface can be controlled, and a sufficient capacity can be obtained in a non-aqueous electrolyte battery, which is preferable.

<Metal particles that can be alloyed with Li>
Alloy-based materials include lithium alone, single metals and alloys forming lithium alloys, or oxides, carbides, nitrides, silicides, sulfides, phosphates, etc. of them, as long as they can store and release lithium ions. It may be any of the compounds and is not particularly limited. The elemental metals and alloys forming the lithium alloy are preferably materials containing group 13 and group 14 metal / semi-metal elements (that is, excluding carbon), more preferably elemental metals of aluminum, silicon and tin, and these. It is an alloy or compound containing an atom, and more preferably, it has silicon or tin as a constituent element, such as a simple substance metal of silicon and tin and an alloy or compound containing these atoms.
One of these may be used alone, or two or more thereof may be used in any combination and ratio.

When a single metal and alloy forming a lithium alloy, or a compound such as an oxide, carbide, nitride, silicide, sulfide or phosphate thereof is used as a negative electrode active material, the metal that can be alloyed with Li is It is in particle form. Examples of the particle morphology include agglomerates, polyhedra, spheres, elliptical spheres, plates, needles, and columns. Further, the primary particles may be aggregated to form secondary particles, and the shape of the secondary particles may be spherical or elliptical spherical. Methods for confirming that the metal particles are metal particles that can be alloyed with Li include identification of the metal particle phase by X-ray diffraction, observation and elemental analysis of the particle structure by an electron microscope, and elements by fluorescent X-ray. Analysis etc. can be mentioned.

As the metal particles that can be alloyed with Li, any conventionally known metal particles can be used, but from the viewpoint of the capacity and cycle life of the non-aqueous electrolyte battery, the metal particles are, for example, Fe, Co, Sb. , Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, As, Nb, Mo, Cu, Zn, Ge, In, Ti and W. It is preferably a metal or a compound thereof. When the metal particles that can be alloyed with Li contain two or more kinds of metals, the particles may be alloy particles made of an alloy of these metals. Among these, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or a metal compound thereof is preferable.

Examples of the metal compound that can be alloyed with Li include metal oxides, metal nitrides, and metal carbides. Further, the compound may contain two or more kinds of metals that can be alloyed with Li.

Among the metal particles that can be alloyed with Li, Si or a Si-containing compound is preferable. Si or a Si-containing compound is preferable in terms of increasing the capacity of the battery. In the present specification, Si or Si-containing compounds are collectively referred to as Si compounds. The Si compound, _{specifically, SiO x, SiN x, SiC} x, SiZ x O y (Z = C, N) , and the like. As the Si compound, Si oxide (SiO _x ) is preferable because it has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals facilitate the entry and exit of alkali ions such as lithium ions. , It is preferable in that a high capacity can be obtained.

This general formula SiO _x is obtained by using silicon dioxide (SiO ₂ ) and metal Si (Si) as raw materials, and x is usually 0 <x <2, more preferably 0.2 or more and 1.8 or less. More preferably, it is 0.4 or more and 1.6 or less, and particularly preferably 0.6 or more and 1.4 or less. Within this range, the battery has a high capacity, and at the same time, the irreversible capacity due to the combination of Li and oxygen can be reduced.

(Oxygen content of metal particles that can be alloyed with Li)
The oxygen content of the metal particles that can be alloyed with Li is not particularly limited, but is usually 0.01% by mass or more and 8% by mass or less, and preferably 0.05% by mass or more and 5% by mass or less. The oxygen distribution state in the particle may be present near the surface, inside the particle, or uniformly present in the particle, but it is particularly preferable that the oxygen is present near the surface. When the amount of oxygen contained in the metal particles that can be alloyed with Li is within the above range, the strong bond between the metal particles and O (oxygen atom) suppresses the volume expansion due to the secondary charge / discharge of the non-aqueous electrolyte solution. It is preferable because it has excellent cycle characteristics.

<Coverage>
In the present embodiment, the negative electrode active material may be coated with a carbonaceous material or a graphite material. Of these, coating with an amorphous carbonaceous material is preferable from the viewpoint of lithium ion acceptability. This coverage is usually 0.5% or more and 30% or less, preferably 1% or more and 25% or less, and more preferably 2% or more and 20% or less. The upper limit of the coverage is from the viewpoint of reversible capacity when the battery is assembled, and the lower limit of the coverage is from the viewpoint that the core carbon-based material is uniformly coated with amorphous carbon to achieve strong granulation. From the viewpoint of the particle size of the particles obtained when pulverized after firing, the above range is preferable.

The finally obtained coverage (content) of carbides derived from the organic compound of the negative electrode active material is the amount of the negative electrode active material, the amount of the organic compound, and the balance measured by the micro method based on JIS K 2270. It can be calculated by the following formula from the coal ratio.

Formula: Coverage of carbides derived from organic compounds (%) = (mass of organic compounds x residual coal ratio x 100) / {mass of negative electrode active material + (mass of organic compounds x residual carbon ratio)}

<Internal porosity>
The internal porosity of the negative electrode active material is usually 1% or more, preferably 3% or more, more preferably 5% or more, still more preferably 7% or more. Further, it is usually less than 50%, preferably 40% or less, more preferably 30% or less, still more preferably 20% or less. If this internal porosity is too small, the amount of liquid in the particles of the negative electrode active material tends to decrease in the non-aqueous electrolyte battery. On the other hand, if the internal porosity is too large, the interparticle gap tends to decrease when the electrode is used. The lower limit of the internal porosity is preferably in the above range from the viewpoint of charge / discharge characteristics, and the upper limit is preferably in the above range from the viewpoint of diffusion of the non-aqueous electrolyte solution. Further, as described above, the gap may be a void, and a substance such as amorphous carbon, a graphite material, a resin, or the like that buffers the expansion or contraction of metal particles that can be alloyed with Li is a gap. The presence or gap in it may be filled with these.

<2-4-2. Negative electrode configuration and manufacturing method>
Any known method can be used for producing the negative electrode (hereinafter, also referred to as “negative electrode plate”) as long as the effect of the present invention is not significantly impaired. For example, it is formed by adding a binder, a solvent, and if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed. can do.

Further, the negative electrode made of an alloy-based material can be produced by any known method. Specifically, as a method for manufacturing a negative electrode, for example, a method in which a binder, a conductive material, or the like is added to the above-mentioned negative electrode active material is directly rolled to form a sheet electrode, or compression molding is performed to form a pellet electrode. However, usually, the above-mentioned negative electrode is used by a coating method, a vapor deposition method, a sputtering method, a plating method, or the like on a current collector for a negative electrode (hereinafter, may be referred to as a “negative electrode current collector”). A method of forming a thin film layer (negative electrode active material layer) containing an active material is used. In this case, a binder, a thickener, a conductive material, a solvent, etc. are added to the above-mentioned negative electrode active material to form a slurry, which is applied to the negative electrode current collector, dried, and then pressed to increase the density. , A negative electrode active material layer is formed on the negative electrode current collector.

Examples of the material of the negative electrode current collector include steel, copper, copper alloy, nickel, nickel alloy, stainless steel and the like. Of these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost.

The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire non-aqueous electrolyte battery may be reduced too much, and conversely, if it is too thin, handling may be difficult.

In addition, in order to improve the binding effect with the negative electrode active material layer formed on the surface, it is preferable that the surface of these negative electrode current collectors is roughened in advance. Surface roughening methods include blasting, rolling with a rough surface roll, a polishing cloth with abrasive particles fixed, a grindstone, emeri buff, a wire brush equipped with a steel wire, etc. to polish the surface of the current collector. Specific polishing method, electrolytic polishing method, chemical polishing method and the like can be mentioned.

Further, in order to reduce the mass of the negative electrode current collector and improve the energy density per mass of the battery, a perforated type negative electrode current collector such as expanded metal or punching metal can also be used. The mass of this type of negative electrode current collector can be freely changed by changing the aperture ratio. Further, when the negative electrode active material layers are formed on both sides of this type of negative electrode current collector, the negative electrode active material layer is less likely to be peeled off due to the rivet effect through the holes. However, when the aperture ratio becomes too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, so that the adhesive strength may be rather low.

The slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener, or the like to the negative electrode material. The term "negative electrode material" as used herein refers to a material that is a combination of the negative electrode active material and the conductive material.

The content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, preferably 75% by mass or more, and usually 97% by mass or less, preferably 95% by mass or less. If the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient, and if it is too large, the content of the conductive material is relatively insufficient, resulting in electricity as the negative electrode. It tends to be difficult to secure conductivity. When two or more negative electrode active materials are used in combination, the total amount of the negative electrode active materials may satisfy the above range.

Examples of the conductive material used for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. One of these may be used alone, or two or more thereof may be used in any combination and ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material also acts as an active material. The content of the conductive material in the negative electrode material is usually 3% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, preferably 25% by mass or less. If the content of the conductive material is too small, the conductivity tends to be insufficient, and if it is too large, the content of the negative electrode active material or the like is relatively insufficient, so that the battery capacity and strength tend to decrease. When two or more conductive materials are used in combination, the total amount of the conductive materials may satisfy the above range.

As the binder used for the negative electrode, any binder can be used as long as it is a material that is safe for the solvent and electrolytic solution used in the production of the electrode. Examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber / isoprene rubber, butadiene rubber, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer and the like. One of these may be used alone, or two or more thereof may be used in any combination and ratio. The content of the binder is usually 0.5 parts by mass or more, preferably 1 part by mass or more, usually 10 parts by mass or less, and preferably 8 parts by mass or less with respect to 100 parts by mass of the negative electrode material. .. If the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient, and if it is too large, the content of the negative electrode active material or the like is relatively insufficient, so that the battery capacity and conductivity tend to be insufficient. It becomes. When two or more binders are used in combination, the total amount of the binders may satisfy the above range.

Examples of the thickener used for the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and the like. One of these may be used alone, or two or more thereof may be used in any combination and ratio. The thickener may be used as needed, but when used, the content of the thickener in the negative electrode active material layer is usually in the range of 0.5% by mass or more and 5% by mass or less. Is preferable.

The slurry for forming the negative electrode active material layer is prepared by mixing the negative electrode active material with a conductive material, a binder, and a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. NS. Water is usually used as the aqueous solvent, but alcohols such as ethanol and organic solvents such as cyclic amides such as N-methylpyrrolidone are used in combination with water in a range of 30% by mass or less. You can also. Examples of the organic solvent include cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic hydrocarbons such as anisole, toluene and xylene. , Butanol, cyclohexanol and the like, and among them, cyclic amides such as N-methylpyrrolidone and linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. Any one of these may be used alone, or two or more thereof may be used in any combination and ratio.

The obtained slurry is applied onto the above-mentioned negative electrode current collector, dried, and then pressed to form a negative electrode active material layer, whereby a negative electrode is obtained. The method of application is not particularly limited, and a method known per se can be used. The drying method is not particularly limited, and known methods such as natural drying, heat drying, and vacuum drying can be used.

<Electrode density>
The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material layer existing on the current collector ^{is preferably 1 g · cm -3} or more, preferably 1.2 g · cm ^-3. The above is more preferable, 1.3 g · cm ^-3 or more is particularly preferable, 2.2 g · cm ^-3 or less is preferable, 2.1 g · cm ^-3 or less is more preferable, and 2.0 g · cm ^-3 or less. Is more preferable, and 1.9 g · cm ^-3 or less is particularly preferable. If the density of the negative electrode active material layer existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, the initial irreversible capacity of the non-aqueous electrolyte battery increases, and the current collector / negative electrode activity High current density charge / discharge characteristics may deteriorate due to a decrease in the permeability of the non-aqueous electrolyte solution near the material interface. On the other hand, if it falls below the above range, the conductivity between the negative electrode active materials may decrease, the battery resistance may increase, and the capacity per unit volume may decrease.

<Average action potential>
As described above, it is presumed that the effect of the present invention is exhibited by the progress of the reaction that brings about a higher resistance reducing effect, starting from the nucleophile generated by the reduction of the electrolytic solution component on the negative electrode. ^{Therefore, the average operating potential (vs. Li /} Li +) of the negative electrode is preferably 1 V or less in order to sufficiently proceed with the reduction of the electrolytic solution component.

<2-5. Separator>
A separator is usually interposed between the positive electrode and the negative electrode to prevent a short circuit. In this case, the non-aqueous electrolyte solution is usually used by impregnating this separator.

(material)
The material of the separator is not particularly limited as long as it is a material stable to a non-aqueous electrolyte solution, but preferably oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, barium sulfate and the like. Examples thereof include sulfates such as calcium sulfate, inorganic substances such as glass filters made of glass fibers; resins such as polyolefin; and the like, more preferably polyolefin, and particularly preferably polyethylene or polypropylene. One of these materials may be used alone, or two or more of these materials may be used. Further, the above materials may be laminated and used.

(Thickness)
The thickness of the separator is arbitrary, but is usually 1 μm or more and 50 μm or less.

(form)
As the form, a thin film such as a non-woven fabric, a woven fabric, or a microporous film is preferably used. As the thin film shape, a thin film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder may be used. A separator made of a microporous film or a non-woven fabric is preferable because it has excellent liquid retention.

(Porosity)
When a porous sheet such as a porous sheet or a non-woven fabric is used as the separator, the porosity of the separator is arbitrary, but is usually 20% or more and 90% or less.

(Air permeability)
The air permeability of the separator can be grasped by the galley value. The gullet value indicates the difficulty of passing air in the film thickness direction, and is expressed by the number of seconds required for 100 mL of air to pass through the film. The galley value of the separator is arbitrary, but is usually 10 to 1000 seconds / 100 mL.

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure in which the above-mentioned positive electrode plate and the negative electrode plate are formed by the above-mentioned separator, and a structure in which the above-mentioned positive electrode plate and the negative electrode plate are spirally wound through the above-mentioned separator. Either may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, 80% or less. preferable. The lower limit of the electrode group occupancy rate is preferably in the above range from the viewpoint of battery capacity. In addition, the upper limit of the electrode group occupancy rate is to secure a gap space from the viewpoint of various characteristics such as charge / discharge repetition performance as a battery and high temperature storage, and from the viewpoint of avoiding the operation of the gas discharge valve that releases the internal pressure to the outside. It is preferably in the above range. If the gap space is too small, the temperature of the battery will increase, causing the members to expand and the vapor pressure of the liquid component of the electrolyte to increase, resulting in an increase in internal pressure. In some cases, the gas release valve that reduces various characteristics and releases the internal pressure to the outside is activated.

[Current collector structure]
The current collecting structure is not particularly limited, but in order to more effectively improve the discharge characteristics of the non-aqueous electrolyte solution, it is preferable to use a structure that reduces the resistance of the wiring portion and the joint portion. .. When the internal resistance is reduced in this way, the effect of using the above-mentioned non-aqueous electrolyte solution is particularly well exhibited.

When the electrode group has the above-mentioned laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to the terminals is preferably used. When the area of one electrode becomes large, the internal resistance becomes large. Therefore, it is also preferably used to reduce the resistance by providing a plurality of terminals in the electrode. In the case where the electrode group has the above-mentioned wound structure, the internal resistance can be reduced by providing a plurality of lead structures on the positive electrode and the negative electrode and bundling them in the terminals.

[Protective element]
As a protective element, a PTC (Positive Temperature Coafficient) element whose resistance increases with heat generation due to excessive current, etc., a thermal fuse, a thermistor, and a valve that shuts off the current flowing through the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation. (Current cutoff valve) and the like. It is preferable to select the protective element under conditions that do not operate under normal use of high current, and 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.

[Exterior body]
The non-aqueous electrolyte battery of the present embodiment is usually configured by storing the above-mentioned non-aqueous electrolyte, negative electrode, positive electrode, separator and the like in an exterior body (exterior case). There is no limitation on this exterior body, and a known one can be arbitrarily adopted as long as the effect of the present invention is not significantly impaired.

The material of the outer case is not particularly limited as long as it is a substance stable to the non-aqueous electrolyte solution used. Specifically, nickel-plated steel plates, stainless steel, aluminum or aluminum alloys, magnesium alloys, metals such as nickel and titanium, or laminated films (laminated films) of resins and aluminum foil are preferably used.

In the outer case using the above metals, the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed and sealed structure, or the above metals are used to caulk the structure via a resin gasket. There are things to do. Examples of the outer case using the above-mentioned laminated film include a case in which resin layers are heat-sealed to form a sealed and sealed structure. In order to improve the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed via the current collecting terminal to form a closed structure, the metal and the resin are bonded to each other. Resin is preferably used.

Further, the shape of the exterior body is also arbitrary, and may be any of, for example, a cylindrical type, a square type, a laminated type, a coin type, and a large size.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded.

The compounds used in this example and comparative examples are shown below.

<Examples 1 to 7, Comparative Examples 10 to 13>
[Preparation of positive electrode]
90 parts by mass of lithium-nickel-cobalt-manganese composite oxide (Li _1.0 Ni _0.5 Co _0.2 Mn _0.3 O ₂ ) as a positive electrode active material, and 7 parts by mass of acetylene black as a conductive material. 3 parts by mass of polyvinylidene fluoride (PVdF) as a coating agent was mixed with a disperser in an N-methylpyrrolidone solvent to form a slurry. This was uniformly applied to both sides of an aluminum foil having a thickness of 15 μm, dried, and then pressed to obtain a positive electrode.

<Comparative Examples 1 to 3>
[Preparation of positive electrode]
The same method as in Example 1 except that 90 parts by mass of a lithium-nickel-cobalt-manganese composite oxide (Li _1.0 Ni _1/3 Co _1/3 Mn _1/3 O _{2) was used as the positive electrode active material.} The positive electrodes of Comparative Examples 1 to 3 were prepared in the above.

<Comparative Examples 4 to 6>
The positive electrodes of Comparative Examples 4 to 6 were prepared in the same manner as in Example 11 except that 90 parts by mass of lithium cobalt composite oxide (LiCoO _{2) was used as the positive electrode active material.}

<Comparative Examples 7-9>
The positive electrodes of Comparative Examples 7 to 9 were prepared in the same manner as in Example 1 except that 90 parts by mass of lithium manganese composite oxide (LiMn ₂ O _{4) was used as the positive electrode active material.}

[Preparation of negative electrode]
98 parts by mass of natural graphite, 1 part by mass of aqueous dispersion of sodium carboxymethyl cellulose (concentration of sodium carboxymethyl cellulose 1% by mass) and aqueous dispersion of styrene-butadiene rubber (styrene-butadiene rubber) as a thickener and binder 1 part by mass was added, and the mixture was mixed with a disperser to form a slurry. The obtained slurry was applied to one side of a copper foil having a thickness of 10 μm, dried, and then pressed to obtain a negative electrode.

[Preparation of non-aqueous electrolyte solution]
LiPF sufficiently dried as an electrolyte in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) (volume ratio EC: DMC: EMC = 3: 3: 4) under a dry argon atmosphere. ₆ was dissolved in 1.0 mol / L (12.3% by volume, as a concentration in the non-aqueous electrolyte solution) (hereinafter, this is referred to as reference electrolyte solution 1). Compounds 1 to 8 were added to the reference electrolytic solution 1 so as to have the contents shown in Table 1 below to prepare non-aqueous electrolytic solutions of Examples 1 to 7 and Comparative Examples 1 to 13. The "content (% by mass)" in the table is the content when the total amount of each non-aqueous electrolyte solution is 100% by mass.

[Manufacturing of non-aqueous electrolyte batteries]
The above positive electrode, negative electrode and polyethylene separator were laminated in this order of negative electrode, separator and positive electrode to prepare a battery element. This battery element is inserted into a bag made of a laminated film in which both sides of aluminum (thickness 40 μm) are coated with a resin layer so that the positive electrode and negative electrode terminals project from each other, and then the prepared non-aqueous electrolyte solution is applied. It was injected into a bag and vacuum-sealed to prepare a laminated non-aqueous electrolyte battery.

<Evaluation of non-aqueous electrolyte batteries>
[Initial conditioning]
In a constant temperature bath at 25 ° C., the battery was charged to 3.72 V with a current corresponding to 0.05 C, and then discharged to 2.8 V at 0.2 C. It was charged to 4.1 V at 0.2 C. Then, aging was carried out under the conditions of 60 ° C. and 12 hours. Then, the battery was discharged to 2.8 V at 0.2 C at 25 ° C. to stabilize the laminated battery. Further, after charging to 4.3 V at 0.2 C, it was discharged to 2.8 V at 0.2 C to perform initial conditioning.
[Measurement of input resistance]
The input resistance of the non-aqueous electrolyte battery subjected to the initial conditioning by the above method in a constant temperature bath at 25 ° C. was measured as follows. The non-aqueous electrolyte battery after the initial conditioning was charged to 3.72 V at 0.2 C. This was charged at 25 ° C. at 25 mA, 50 mA, and 100 mA, and the voltage at 10 seconds was measured. The input resistance value (Ω) was obtained from the slope of the obtained current-voltage straight line.

From Table 1, as shown in Examples 1 to 7, a non-aqueous electrolyte solution containing a specific aromatic isocyanate compound and at least Ni and Co as transition metals are contained, and 40 mol% or more of the transition metals are Ni. Non-aqueous electrolyte secondary batteries having a positive electrode having a certain transition metal oxide include Comparative Examples 1 to 9 (providing a non-aqueous electrolyte solution containing a specific aromatic isocyanate compound, but containing a specific transition metal oxide. Non-aqueous electrolyte secondary battery including a positive electrode) and Comparative Examples 10 to 13 (the positive electrode contains a specific transition metal oxide but is not a specific aromatic isocyanate compound, and includes a non-aqueous electrolyte solution containing diisocyanate. It can be seen that the input resistance was significantly reduced as compared with the non-aqueous electrolyte secondary battery).

<Examples 8 to 15>
In Example 2, a battery was produced in the same manner as in Example 2 except that compounds 9 to 13 were further added to the non-aqueous electrolytic solution as shown in Table 2, and the above input resistance value and the initial charge / discharge efficiency described later were described. Was measured. The results are shown in Table 2.

[Measurement of initial charge / discharge efficiency]
In the above initial conditioning, (first discharge capacity) / (first charge capacity) x 1
The initial charge / discharge efficiency (%) was obtained from 00.

<Examples 16 to 17>
In Example 5, a battery was produced in the same manner as in Example 5 except that Compound 9 or 13 was further added to the non-aqueous electrolyte solution as shown in Table 2, and the above-mentioned input resistance value and initial charge / discharge efficiency were measured. did. The results are shown in Table 2.

From Table 2, as shown in Examples 8 to 17, a transition with a non-aqueous electrolyte solution containing at least one compound having a _{PF bond and a compound having an SO 2 structure in a specific aromatic isocyanate compound.} A non-aqueous electrolyte secondary battery having a positive electrode containing a transition metal oxide containing at least Ni and Co as a metal and 40 mol% or more of the transition metal being Ni has only the effect of significantly reducing the input resistance. It can be seen that it has the effect of improving the initial charge / discharge efficiency.

According to the non-aqueous electrolyte solution according to the present invention, the input resistance of the non-aqueous electrolyte secondary battery can be lowered, and the deterioration of the battery having a high capacity can be improved, which is useful.
Further, the non-aqueous electrolyte solution according to the present invention and the non-aqueous electrolyte secondary battery using the non-aqueous electrolyte solution can be used for various known applications in which the non-aqueous electrolyte secondary battery is used. Specific examples include, for example, laptop computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile fax machines, mobile copy machines, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, and mini discs. , Transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, bikes, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, watches, power tools, strobes, cameras, household backups Examples include a power source, a backup power source for business establishments, a power source for load leveling, and a natural energy storage power source.

Claims (6)

A transition metal oxide capable of occluding and releasing metal ions, which contains at least Ni and Co and contains a transition metal oxide in which 40 mol% or more of the transition metal is Ni.
A non-aqueous electrolyte solution used in a non-aqueous electrolyte secondary battery comprising a negative electrode containing a carbon-based material capable of occluding and releasing metal ions, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. It is an aqueous electrolyte
A non-aqueous electrolytic solution containing at least one of an isocyanate compound selected from the compound represented by the following general formula (1) and the compound represented by the general formula (2).

(In the formula (1), m and n are integers satisfying m + n = 6, and n ≧ 2. X is a single bond or a carbon which may have a heteroatom which may be the same or different from each other. It represents a divalent organic group of numbers 1 to 10. Y represents a monovalent organic group of carbon numbers 1 to 10 which may have a hydrogen atom, a halogen atom, or a hetero atom.)

(In equation (2), p, q, r, s are integers satisfying p + q = 5, r + s = 5, and p ≧ 1, s ≧ 1. R is a hydrogen atom which may be the same or different from each other. , A halogen atom, or an organic group having 1 to 10 carbon atoms which may have a hetero atom. X'is a single bond or a divalent group having 1 to 10 carbon atoms which may have a hetero atom. Represents an organic group.) The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous electrolyte solution contains the compound represented by the formula (1), and n is 2 in the formula (1). The non-aqueous electrolyte solution according to claim 1 or 2, wherein the non-aqueous electrolyte solution contains a compound represented by the formula (1), and X is a methylene group or a dimethyl methylene group in the formula (1). The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous electrolyte solution contains the compound represented by the formula (2), and s = p = 1 in the formula (2). The non-aqueous electrolyte solution according to any one of claims 1 to 4, _{wherein the non-aqueous electrolyte solution contains at least one compound having a PF bond and a compound having an SO 2 structure.} It includes a positive electrode capable of occluding and releasing metal ions, a negative electrode containing a carbon-based material capable of occluding and releasing metal ions, and a non-aqueous electrolyte solution containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. It is a non-aqueous electrolyte secondary battery,
The positive electrode contains a transition metal oxide and at least Ni and Co as a transition metal, and 40 mol% or more of the transition metal is Ni.
A non-aqueous electrolyte secondary battery in which the non-aqueous electrolyte solution is the non-aqueous electrolyte solution according to any one of claims 1 to 5.