JP6507677B2 - Nonaqueous Electrolyte, and Nonaqueous Electrolyte Secondary Battery Using the Same - Google Patents

Description

  The present invention relates to a non-aqueous electrolytic solution and a non-aqueous electrolytic solution secondary battery using the same.

With the rapid progress of electronic devices, the demand for higher capacity for secondary batteries is increasing, and non-aqueous electrolyte batteries such as lithium ion secondary batteries with high energy density are widely used and actively researched It is done.
In general, an electrolyte used in a non-aqueous electrolyte battery is mainly composed of an electrolyte and a non-aqueous solvent. As an electrolyte solution of a lithium ion secondary battery, a non-aqueous electrolyte solution in which an electrolyte such as LiPF ₆ is dissolved in a mixed solvent of a high dielectric constant solvent such as cyclic carbonate and a low viscosity solvent such as chain carbonate is used. It is done.

In the lithium ion secondary battery, when charge and discharge are repeated, the electrolyte is decomposed on the electrode, deterioration of materials constituting the battery, and the like occur, and the capacity of the battery decreases. In addition, in some cases, the safety against battery swelling, ignition and explosion may be reduced.
Until now, the method of improving the battery characteristic of a lithium ion secondary battery is proposed by containing a specific additive in a non-aqueous electrolyte. For example, in Patent Document 1, the positive electrode is a material containing lithium composite oxide, the negative electrode is a material containing graphite, the non-aqueous solvent contains cyclic carbonate and chain carbonate as main components, and 0. It is reported that the capacity retention after 50 cycles at room temperature is improved by using an electrolyte containing 1% by weight to 4% by weight of 1,3-propanesultone and / or 1,4-butanesultone. It is done. A solvent containing a carbonate derivative containing a Patent Document 2 halogen _{atoms, [B (C i H 2} (i-2) O 4) (C j H 2 (j-2) O 4)] - ( wherein , I and j each represents an integer of 2 or more) and a second anion other than the first anion
It is reported that the cycle characteristics in a 4.2 V, 25 ° C. environment and the low temperature characteristics in a −20 ° C. environment are improved by using an electrolyte containing the following In Patent Document 3, among the Cu affinity compounds, among a nitrile compound having two nitrile groups, a trinitrile compound having three nitrile groups, and a thiodialkyl nitrile compound having two nitrile groups and having a thioether group in the molecule It has been reported that the use of an electrolyte containing one or more species improves the overdischarge characteristics.

JP 2000-003724 A JP 2005-228565 A JP, 2006-73513, A

  The present invention relates to a non-aqueous electrolytic solution capable of producing a battery which is low in gas generation under high temperature conditions, excellent in cycle characteristics and excellent in high-rate discharge characteristics in a non-aqueous electrolytic solution secondary battery, and non-aqueous electrolysis using the same. It is an object to provide a liquid secondary battery.

Although Patent Documents 1 to 3 certainly contribute to the improvement of various properties, they have not solved at all the gas generation particularly important for battery safety, and further high temperature cycle characteristics and high which are important for battery characteristics. It has not been demonstrated that the rate discharge characteristics improve.
As a result of repeating various studies in order to solve the above problems, the present inventors have found that the above problems can be solved when specific compounds are combined in a predetermined amount, and have completed the present invention.

That is, the gist of the present invention is
<1> A non-aqueous electrolytic solution used in a non-aqueous electrolytic solution secondary battery comprising a positive electrode having a positive electrode active material capable of absorbing and releasing metal ions, and a negative electrode having a negative electrode active material capable of absorbing and releasing metal ions And
The content of cyclic carbonate having unsaturated bond is X (mass%),
The content of cyclic carbonate having a halogen atom is Y (mass%),
The content of at least one compound selected from sultone compounds and nitrile compounds is Z (mass%),
Containing at least one compound selected from a compound having an isocyanato group (NNCCO group), a compound represented by the following formula (1), and a compound having two or more of an acrylic group or a methacryl group in the molecule Amount A (mass%),

(R ¹ , R ² and R ³ each independently represent an organic group, and at least one of R ¹ , R ² and R ³ represents an organic group having an unsaturated bond.)
And a non-aqueous electrolytic solution characterized by satisfying all of the following formulas.
0 ≦ X ≦ 0.5
0.5 ≦ Y ≦ 8.0
0.8 ≦ Z ≦ 6.0
0.8 ≦ A ≦ 5.0
However, the content refers to the ratio (% by mass) of each compound to the total weight of the non-aqueous electrolyte, and when two or more compounds are contained, X, Y, Z, and A indicate the total amount thereof.
<2> The Z (mass%) is the content of the sultone compound, and 1.0 ≦ Z ≦ 4.0
The non-aqueous electrolytic solution described in <1>, wherein the non-aqueous electrolytic solution described in <1> is satisfied.
<3> The Z (mass%) is the content of the dinitrile compound, and 1.0 ≦ Z ≦ 4.0
The non-aqueous electrolytic solution described in <1>, wherein the non-aqueous electrolytic solution described in <1> is satisfied.
<4> A non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of absorbing and releasing metal ions, and a negative electrode having a negative electrode active material capable of absorbing and releasing metal ions,
The non-aqueous electrolyte secondary battery using the non-aqueous electrolyte as described in any one of <1>-<3>.

  According to the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery which is low in gas generation and excellent in cycle characteristics and high-rate discharge characteristics.

  Below, the form for implementing this invention is demonstrated in detail. However, the description described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents unless exceeding the gist of the claims.

[1. Non-aqueous electrolyte solution]
The non-aqueous electrolytic solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the same, as a general non-aqueous electrolytic solution,
The content of cyclic carbonate having unsaturated bond is X (mass%),
The content of cyclic carbonate having a halogen atom is Y (mass%),
The content of at least one compound selected from sultone compounds and nitrile compounds is Z (mass%),
Containing at least one compound selected from a compound having an isocyanato group (NNCCO group), a compound represented by the following formula (1), and a compound having two or more of an acrylic group or a methacryl group in the molecule Amount A (mass%),

(R ¹ , R ² and R ³ each independently represent an organic group, and at least one of R ¹ , R ² and R ³ represents an organic group having an unsaturated bond.)
And the following equations are all satisfied.
0 ≦ X ≦ 0.5
0.5 ≦ Y ≦ 8.0
0.8 ≦ Z ≦ 6.0
0.8 ≦ A ≦ 5.0
However, the content refers to the ratio (% by mass) of each compound to the total weight of the non-aqueous electrolyte, and when two or more compounds are contained, X, Y, Z, and A indicate the total amount thereof.

[1-1. Cyclic carbonate having unsaturated bond]
The cyclic carbonate having an unsaturated bond described in the claims is not particularly limited, and examples thereof include the following.
For example, vinylene carbonate compounds such as vinylene carbonate (VC), methylvinylene carbonate, ethylvinylene carbonate, 1,2-dimethylvinylene carbonate, 1,2-diethylvinylene carbonate, fluorovinylene carbonate, trifluoromethylvinylene carbonate; vinyl ethylene Carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, 1-n-propyl-2-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1,1-divinylethylene Carbonates, vinyl ethylene carbonate compounds such as 1,2-divinyl ethylene carbonate; 1,1-dimethyl-2-methylene ethylene carbonate, 1,1-diethyl- - methylene ethylene carbonate compounds such as methylene ethylene carbonate, and ethynyl ethylene carbonate and the like.

Among these, vinylene carbonate, vinyl ethylene carbonate and ethynyl ethylene carbonate are preferable from the viewpoint of improving cycle characteristics and capacity retention characteristics after high temperature storage, among which vinylene carbonate and vinyl ethylene carbonate are more preferable, and vinylene carbonate is particularly preferable. These may be used alone or in combination of two or more. When using 2 or more types together, it is preferable to use vinylene carbonate and vinyl ethylene carbonate together.

The content of the cyclic carbonate having a unsaturated bond is, when the content with respect to the weight of the whole non-aqueous electrolyte is X (mass%),
0 ≦ X ≦ 0.5
Meet. Among them, the upper limit of the content X is more preferably 0.3 or less, and further preferably 0.2 or less. Under such conditions, generation of a high temperature storage gas can be suppressed in combination with other additives, and an increase in resistance is suppressed, so that high temperature cycle characteristics and high-rate discharge characteristics are also excellent.

[1-2. Cyclic carbonate having halogen atom]
Although there is no restriction | limiting in particular as a cyclic carbonate which has a halogen atom as described in a claim, The following is mentioned as an example.
As a halogen atom of cyclic carbonate which has a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, Among these, a fluorine atom and a chlorine atom are preferable, and a fluorine atom is particularly preferable.

  As the cyclic carbonate having a fluorine atom, for example, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, tetrafluoroethylene carbonate, 1-fluoro -2- methyl ethylene carbonate, 1-fluoro 1-methyl ethylene carbonate, 1, 2-difluoro 1-methyl ethylene carbonate, 1, 1, 2-trifluoro 2-methyl ethylene carbonate, trifluoromethyl ethylene carbonate, etc. Can be mentioned.

Among these, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and 1-fluoro-2-methylethylene carbonate are preferable from the viewpoint of improving cycle characteristics and high-temperature storage characteristics. These may be used alone or in combination of two or more.
When the content of cyclic carbonate having a halogen atom is Y (mass%) based on the total weight of the non-aqueous electrolyte,
0.5 ≦ Y ≦ 8.0
Meet. Above all, the upper limit of the content Y is more preferably 7.0 or less, further preferably 6.0 or less, and particularly preferably 5.0 or less. The lower limit of the content Y is more preferably 0.8 or more, and still more preferably 1.0 or more. Under such conditions, in combination with other additives, generation of high temperature storage gas can be suppressed, and high temperature cycle characteristics are improved.

[1-3. Sultone compounds and nitrile compounds]
Although there is no restriction | limiting in particular as a sultone compound and a nitrile compound which are described in the claim, The following are mentioned as an example.
As a sultone compound, for example,
There may be mentioned 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, and 1,4-butene sultone. Among these, 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone are preferable, and 1,3-propane sultone and 1,3-propene sultone are particularly preferable in order to obtain excellent cycle characteristics. . These may be used alone or in combination of two or more.

As a nitrile compound, for example,
Acetonitrile, propionitrile, butyronitrile, valeronitrile, hexane nitrile, heptane nitrile, octane nitrile, nonane nitrile, nonane nitrile, decane nitrile, lauronitrile, tridecane nitrile, tetradecane nitrile, hexadecane nitrile, pentadecane nitrile, heptadecane nitrile, octadecane nitrile, nona nitrile Mononitriles such as decanenitrile, icosanenitrile, crotononitrile, methacrylonitrile, acrylonitrile and methoxyacrylonitrile; malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, suberonitrile, azela nitrile, sebaconitrile, undecane dinitrile, dodecane Nitrile, methyl malononitrile, ethyl malononitrile, isopropylmer Nononitrile, tert-butyl malononitrile, methyl succinonitrile, 2,2-dimethyl succinonitrile, 2,3-dimethyl succinonitrile, trimethyl succinonitrile, tetramethyl succinonitrile, 3,3'-oxydipropio Dinitriles such as nitrile, 3,3'-thiodipropionitrile, 3,3 '-(ethylenedioxy) dipiponitrile, 3,3'-(ethylenedithio) dipropionitrile, 1,
Trinitriles such as 2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-tris (2-cyanoethoxy) propane, tris (2-cyanoethyl) amine and the like .

  Among these, valeronitrile, octane nitrile, decane nitrile, lauronitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, suberonitrile, crotononitrile are preferable, and valeronitrile, octane nitrile, decane nitrile, lauronitrile, sk Sinonitrile, adiponitrile, pimeronitrile and suberonitrile are preferable because they have a large effect of suppressing gas generation inside the battery. These may be used alone or in combination of two or more.

The content of the at least one or more compounds selected from the sultone compounds and the nitrile compounds is represented as Z (mass%) based on the total weight of the non-aqueous electrolytic solution,
0.8 ≦ Z ≦ 6.0
Meet. Among them, the upper limit of the content Z is more preferably 5.5 or less, and further preferably 5.0 or less. As a lower limit of the content Z, 1.0 or more is more preferable. Within such a range, the increase in resistance inside the battery is not too large, and the effect of suppressing gas generation can also be sufficiently obtained.

Further, when the content of the sultone compound is Z (S), it is preferable that 1.0 ≦ Z (S) ≦ 4.0, and 1.0 ≦ Z (S) ≦ 3.5. More preferable. When the content of the dinitrile compound is Z (N), it is preferable that 1.0 ≦ Z (N) ≦ 4.0, and 1.0 ≦ Z (N) ≦ 3.5. More preferable.
[1-4. Compound Having Isocyanato Group (N = C = O Group), Compound Represented by Formula (1), and Compound Having Two or More Acryl Groups or Methacryl Groups in Molecule]
The compound having an isocyanato group (N = C = O group), the compound represented by the formula (1) and the compound having two or more acryl groups or methacryl groups in the molecule are not particularly limited. The ones of

Examples of the compound having an isocyanato group (N = C = O group) include isocyanatomethane, isocyanatoethane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1 -Isocyanatoheptane, 1-isocyanatooctane, 1-isocyanatononane, 1-isocyanatodecane, isocyanatocyclohexane,
Methoxy carbonyl isocyanate, ethoxy carbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxy sulfonyl isocyanate, ethoxy sulfonyl isocyanate, propoxy sulfonyl isocyanate, butoxy sulfonyl isocyanate, fluoro sulfonyl isocyanate,
1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanatooctane, 1,9-di Isocyanatononane, 1,10-diisocyanatodecane,
1,3-diisocyanatopropene, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3-difluorobutane, 1,5-diisocyanato-2 -Pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato -3,4-difluorohexane,
Toluene diisocyanate, xylene diisocyanate, tolylene diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,2- Diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-1,1′-diisocyanate, dicyclohexylmethane-2,2′-diisocyanate, dicyclohexylmethane-3,3 ′ Diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,6,11-triisocyanatoundecane, 4-isocyanatomethyl-1,8-octamethylenediisocyanate And 1,3,5-triisocyanatomethylbenzene, bicyclo [2.2.1] heptane-2,5-diylbis (methyl isocyanate), bicyclo [2.2.1] heptane-2,6-diylbis (Methyl = isocyanate), 1,3,5-tris (6-isocyanatohex-1-yl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2, 4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 4- (isocyanatomethyl) octamethylene diisocyanate and the like.

Among these, t-butyl isocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bisbis (Isocyanatomethyl) cyclohexane is preferred, and more preferably hexamethylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane. These are preferable from the point of the cycle characteristic improvement and the high temperature storage characteristic improvement. These may be used alone or in combination of two or more.
Examples of the compound represented by the following formula (1) include the following compounds.

(R ¹ , R ² and R ³ each independently represent an organic group, and at least one of R ¹ , R ² and R ³ represents an organic group having an unsaturated bond.)
For example, trivinyl isocyanurate, tri (1-propenyl) isocyanurate, triallyl isocyanurate, trimethallyl isocyanurate, methyl diallyl isocyanurate, ethyl diallyl isocyanurate, diethyl allyl isocyanurate, diethyl vinyl isocyanurate, diethyl vinyl isocyanurate, tri (propargyl) Isocyanurate, tris (2-acryloxymethyl) isocyanurate, tris (2-acryloxyethyl) isocyanurate, tris (2-methacryloxymethyl) isocyanurate, tris (2-methacryloxyethyl) isocyanurate, ε-caprolactone Modified tris- (2-acryloxyethyl) isocyanurate etc. are mentioned.

  Among them, triallyl isocyanurate, trimethallyl isocyanurate, tris (2-acryloxyethyl) isocyanurate, tris (2-methacryloxyethyl) isocyanurate and ε-caprolactone modified tris- (2-acryloxyethyl) isocyanurate are preferable. Triarylisocyanurate and tris (2-acryloxyethyl) isocyanurate are particularly preferable because they have a large effect of improving the cycle characteristics. These may be used alone or in combination of two or more.

The compound having two or more acryl groups or methacryl groups in the molecule is not particularly limited, and the following may be mentioned as an example.
For example, 2-hydroxy-3-acryloyloxypropyl methacrylate, tetraethylene glycol diacrylate, nona ethylene glycol diacrylate, propoxylated ethoxylated bisphenol A diacrylate, propoxylated ethoxylated bisphenol A diacrylate, 9,9-bis [ 4- (2-acryloyloxyethoxy) phenyl] fluorene, tricyclodecanedimethanol diacrylate, 1,10-decanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, dipropylene Glycol diacrylate, tripropylene glycol diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentae Slititol tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol polymethacrylate, tetraethylene glycol dimethacrylate, nona ethylene glycol dimethacrylate, propoxylated ethoxylated Bisphenol A dimethacrylate, propoxylated ethoxylated bisphenol A dimethacrylate, 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene, tricyclodecanedimethanol dimethacrylate, 1,10-decanediol dimethacrylate, 1,6-Hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, dipropylene glycol di Methacrylate, tripropylene glycol dimethacrylate, pentaerythritol trimethacrylate, trimethylolpropane trimethacrylate, ditrimethylolpropane tetramethacrylate, ethoxylated pentaerythritol tetramethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol pentamethacrylate, dimethacrylate Pentaerythritol hexamethacrylate, dipentaerythritol polymethacrylate, tetramethylol methane tetraacrylate and the like can be mentioned.

Among these, tetraethylene glycol diacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, and tetramethylol methane tetraacrylate are preferable because they have a large effect of improving cycle characteristics and gas suppression.
At least one compound selected from a compound having an isocyanato group (N = C = O group), a compound represented by the following formula (1), and a compound having two or more of an acryl group or a methacryl group in a molecule When the content relative to the total weight of the non-aqueous electrolyte is A (mass%),
0.8 ≦ A ≦ 5.0
Meet. Among them, the upper limit of the content A is more preferably 4.0 or less, and further preferably 3.0 or less. The lower limit of the content A is more preferably 1.0 or more. Under such conditions, in combination with other additives, the effect of improving the cycle characteristics is large, and the increase in resistance is suppressed, so the high-rate discharge characteristics are also excellent.

In addition, in the above contents, when each compound contains two or more kinds, X, Y, Z and A indicate the total amount thereof.
In the present invention, a battery having balanced characteristics which can not be achieved by using specific compounds in specific amounts in combination and adding them to the electrolyte alone or in an amount deviating from a specific range. The obtained electrolytic solution can be obtained. Although the details of the reason why such an effect appears are not known, it is considered as follows. That is, in the present invention, the amount of the cyclic carbonate having unsaturated bonds is limited to a certain amount or less, and the resistance of the film formed on the negative electrode surface is suppressed by using the cyclic carbonate having a halogen atom. Furthermore, at least one compound selected from sultone compounds and nitrile compounds, a compound having an isocyanato group (N = C = O group), a compound represented by the following formula (1), and an acryl group or a methacryl group When at least one compound selected from compounds having two or more in the molecule is present at a constant content, the stability of the film formed on the negative electrode surface is improved, and as a result, cycle characteristics, storage characteristics, etc. are obtained. It is considered that various battery characteristics are improved.

[1-5. Electrolytes〕
There is no restriction | limiting in the electrolyte used for the non-aqueous electrolyte solution of this invention, A well-known thing can be employ | adopted arbitrarily, as long as it is used as an electrolyte in the target non-aqueous electrolyte secondary battery. When using the non-aqueous electrolyte solution of the present invention for a lithium secondary battery, usually, a lithium salt is used as the electrolyte.

Specific examples of the electrolyte include inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiSO ₃ F, LiN (FSO ₂ ) ₂ ;
LiCF ₃ SO ₃ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,3-hexafluoropropane disulfonyl imide, lithium cyclic 1,2-tetrafluoroethane _{disulfonylimide, LiN (CF 3 SO 2)} (C 4 F 9 SO 2), LiC (CF 3 SO 2) 3, LiPF 4 (CF 3) 2, LiPF 4 (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₂ ) Fluorine-containing organic lithium salts such as ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) _{2 and the} like;
Examples thereof include lithium salts of dicarboxylic acid-containing complexes such as lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate.

Among them, LiPF ₆ , LiBF ₄ , LiSO ₃ F, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (LiSO ₆ ), LiF ₃ , LiSO ₃ F, LiN (FSO ₂ ) ₂ from the viewpoint of solubility and dissociation in nonaqueous solvents, electrical conductivity and obtained cell characteristics. CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium bis (oxalato) borate, lithium difluoro oxalato borate, lithium tris (oxalato) phosphate, lithium difluoro bis ( Oxalato) phosphate and lithium tetrafluoro (oxalato) phosphate are preferred, and in particular LiPF ₆ and LiBF ₄ are preferred.

Moreover, an electrolyte may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Above all, when two types of specific inorganic lithium salts are used in combination or an inorganic lithium salt and a fluorine-containing organic lithium salt are used in combination, gas generation during trickle charge is suppressed, and deterioration after high temperature storage is suppressed. It is preferable because In particular, the combination and the LiPF ₆ and LiBF _4, and an inorganic lithium salt such as _{LiPF 6, LiBF 4, LiCF 3} SO 3, LiN (CF
It is preferable to use in combination with a fluorine-containing organic lithium salt such as ₃ SO ₂ ) ₂ or LiN (C ₂ F ₅ SO ₂ ) ₂ .

Furthermore, in the case of using LiPF ₆ and LiBF ₄ in combination, it is preferable that LiBF ₄ is contained usually in a ratio of 0.01% by mass or more and 50% by mass or less with respect to the entire electrolyte. The above ratio is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, while preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less Most preferably, it is 3% by mass or less. When the ratio is in the above range, the desired effect is easily obtained, and the low dissociation degree of LiBF ₄ suppresses the increase in the resistance of the electrolytic solution.

On the other hand, inorganic lithium salts such as LiPF ₆ and LiBF ₄ , inorganic lithium salts such as LiSO ₃ F and LiN (FSO ₂ ) ₂ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F) ₅ SO ₂ ) ₂ , lithium cyclic 1,3-hexafluoropropane disulfonyl imide, lithium cyclic 1,2-tetrafluoroethane disulfonyl imide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC ( CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF _{2 CF 3) 2, LiBF 2 (} C 2 F 5) 2, LiBF 2 (CF 3 SO 2) 2, LiBF 2 (C 2 F 5 SO 2) ₂ or the like containing Fluorine organic lithium salt, lithium bis (oxalato) borate, lithium tris (oxalato) phosphate, lithium difluoro oxalato borate, lithium tri (oxalato) phosphate, lithium difluoro bis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate and the like The ratio of the inorganic lithium salt in the whole electrolyte is usually 70% by mass or more, preferably 80% by mass or more, more preferably 85% by mass or more, and usually 99% by mass. It is not more than mass%, preferably not more than 95 mass%.

  The concentration of the lithium salt in the non-aqueous electrolyte solution of the present invention is arbitrary as long as the gist of the present invention is not impaired, but it is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0. It is 8 mol / L or more. Also, it is usually in the range of 3 mol / L or less, preferably 2 mol / L or less, more preferably 1.8 mol / L or less, and still more preferably 1.6 mol / L or less. When the concentration of the lithium salt is in the above range, the electric conductivity of the non-aqueous electrolytic solution becomes sufficient, and the electric conductivity decreases due to the increase in viscosity, and the non-aqueous electrolytic solution 2 using the non-aqueous electrolytic solution of the present invention Suppress the decrease in performance of the secondary battery.

[1-6. Non-aqueous solvent]
As a non-aqueous solvent which the non-aqueous electrolyte solution of this invention contains, it can select suitably from what is conventionally known as a solvent of non-aqueous electrolyte, and can be used.
Examples of non-aqueous solvents that are usually used include cyclic carbonates, linear carbonates, linear and cyclic carboxylic acid esters, linear and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, aromatic fluorine-containing solvents, etc. It can be mentioned.

  As cyclic carbonate, cyclic carbonates, such as ethylene carbonate, a propylene carbonate, butylene carbonate, are mentioned, Carbon number of cyclic carbonate is 3 or more and 6 or less normally. Among these, ethylene carbonate and propylene carbonate are preferable because they have a high dielectric constant and thus the electrolyte is easily dissolved, and the non-aqueous electrolyte secondary battery has good cycle characteristics.

Examples of linear carbonates include linear carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, etc. The carbon number is preferably 1 or more and 5 or less, and particularly preferably 1 or more and 4 or less. Among them, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferable from the viewpoint of improving the battery characteristics. Further, chain carbonates in which a part of hydrogen of the alkyl group is substituted with fluorine may also be mentioned. As fluorine-substituted chain carbonate, bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) carbonate, bis (2-fluoroethyl) carbonate, bis (2,2-difluoroethyl) Carbonate, bis (2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, 2,2,2-trifluoroethyl methyl carbonate and the like can be mentioned.

  As linear carboxylic acid esters, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, ethyl propionate, propionic acid Isopropyl, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, ethyl pivalate etc. and a chain in which part of hydrogen of these compounds is substituted with fluorine Like carboxylic acid esters. Examples of fluorine-substituted chain carboxylic acid esters include methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, 2,2,2-trifluoroethyl trifluoroacetate and the like. Among these, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, methyl valerate, methyl isobutyrate, ethyl isobutyrate, methyl pivalate are batteries. It is preferable from the point of characteristic improvement.

Examples of cyclic carboxylic acid esters include γ-butyrolactone, γ-valerolactone and the like, and cyclic carboxylic acid esters in which part of hydrogen of these compounds is substituted with fluorine. Among these, γ-butyrolactone is more preferable.
As a chain ether, dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1 -Ethoxymethoxyethane, 1,2-ethoxymethoxyethane and the like and chain ethers in which part of hydrogen of these compounds is substituted with fluorine are mentioned. As fluorine-substituted chain ethers, bis (trifluoroethoxy) ethane, ethoxytrifluoroethoxyethane, methoxytrifluoroethoxyethane, 1,1,1,2,2,3,4,5,5,5-deca Fluoro-3-methoxy-4-trifluoromethyl-pentane, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-ethoxy-4-trifluoromethyl-pentane, 1 1,1,1,2,2,3,4,5,5,5-decafluoro-3-propoxy-4-trifluoromethyl-pentane, 1,1,2,2-tetrafluoroethyl-2,2,2, Examples include 3,3-tetrafluoropropyl ether, 2,2-difluoroethyl-2,2,3,3-tetrafluoropropyl ether and the like. Among these, 1,2-dimethoxyethane and 1,2-diethoxyethane are more preferable.

Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran and the like, and cyclic ethers in which part of hydrogen of these compounds is substituted with fluorine.
As the phosphorus-containing organic solvent, trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, Examples thereof include triphenyl phosphite, trimethyl phosphine oxide, triethyl phosphine oxide, triphenyl phosphine oxide and the like, and phosphorus-containing organic solvents in which part of hydrogen of these compounds is substituted with fluorine. Examples of fluorine-substituted phosphorus-containing organic solvents include tris (2,2,2-trifluoroethyl) phosphate and tris (2,2,3,3,3-pentafluoropropyl) phosphate.

  Examples of sulfur-containing organic solvents include sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethylsulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate Ethyl ethane sulfonate, dimethyl sulfate, diethyl sulfate, dibutyl sulfate and the like, and sulfur-containing organic solvents in which part of hydrogen of these compounds is substituted with fluorine are mentioned.

Examples of the aromatic fluorine-containing solvent include fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, benzotrifluoride and the like.
Among the above non-aqueous solvents, it is preferable to use ethylene carbonate and / or propylene carbonate which is a cyclic carbonate, and the combined use of these and a linear carbonate can further achieve both the high conductivity and low viscosity of the electrolyte. It is preferable from

  A non-aqueous solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. When using 2 or more types together, for example, when using cyclic carbonate and chain carbonate together, suitable content of chain carbonate occupied in non-aqueous solvent is usually 20 volume% or more, preferably 40 volume% or more, Also, it is usually 95% by volume or less, preferably 90% by volume or less. On the other hand, the suitable content of the cyclic carbonate in the non-aqueous solvent is usually 5% by volume or more, preferably 10% by volume or more, and usually 80% by volume or less, preferably 60% by volume or less. When the proportion of the linear carbonate is in the above range, the increase in viscosity of the non-aqueous electrolytic solution is suppressed, and the decrease in electric conductivity of the non-aqueous electrolytic solution due to the decrease in the degree of dissociation of the lithium salt as the electrolyte is suppressed. In addition, in this specification, although the volume of a non-aqueous solvent is a measured value at 25 degreeC, what is a solid at 25 degreeC like ethylene carbonate uses the measured value in melting | fusing point.

[1-7. Other additives]
The non-aqueous electrolytic solution of the present invention may contain various additives as long as the effects of the present invention are not significantly impaired. As the additives, conventionally known ones can be optionally used. In addition, an additive may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

(Overcharge inhibitor)
Specific examples of the overcharge inhibitor include alkylbiphenyl such as 2-methylbiphenyl and 2-ethylbiphenyl, terphenyl, a partially hydrogenated terphenyl, cyclopentylbenzene, cis-1-propyl-4-phenylcyclohexane, trans -1-propyl-4-phenylcyclohexane, cis-1-butyl-4-phenylcyclohexane, trans-1-butyl-4-phenylcyclohexane, diphenyl ether, dibenzofuran, ethylphenyl carbonate, tris (2-t-amylphenyl) phosphate , Tris (3-
t-Amylphenyl) phosphate, tris (4-t-amylphenyl) phosphate, tris (2-cyclohexylphenyl) phosphate, tris (3-cyclohexylphenyl) phosphate, tris (4-cyclohexylphenyl) phosphate, triphenylphosphate, tri Aromatic compounds such as tolyl phosphate, tri (t-butylphenyl) phosphate, methylphenyl carbonate, diphenyl carbonate, etc .; 2-fluorobiphenyl, 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4'-difluorobiphenyl, 2,4 Partially fluorinated compounds of aromatic compounds such as difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, etc .; 2,4-difluoroanisole, 2,5-difluoroanisole And fluorine-containing anisole compounds such as 2,6-difluoroanisole and 3,5-difluoroanisole.

The content of these overcharge inhibitors in the non-aqueous electrolytic solution is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5 The content is usually at least 5% by mass, preferably at most 3% by mass, more preferably at most 2% by mass. When the concentration is in the above-mentioned range, the desired effect of the overcharge preventing agent is easily exhibited, and deterioration of battery characteristics such as high-temperature storage characteristics is suppressed. By including the overcharge inhibitor in the non-aqueous electrolytic solution, it is possible to suppress the explosion and ignition of the non-aqueous electrolytic solution secondary battery due to the overcharge, and the safety of the non-aqueous electrolytic solution secondary battery is improved. preferable.

  Other auxiliary agents include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate, methoxyethyl-ethyl carbonate, ethoxyethyl-methyl carbonate, ethoxyethyl-ethyl carbonate, etc .; dimethyl succinate , Diethyl succinate, diallyl succinate, dimethyl maleate, diethyl maleate, diallyl maleate, dipropyl maleate, dibutyl maleate, bis (trifluoromethyl) maleate, bis (pentafluoroethyl) maleate, bis maleate Dicarboxylic acid diester compounds such as (2,2,2-trifluoroethyl); 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10- Tetraoxaspi [5.5] spiro compounds such as undecane; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methyl Nitrogen-containing compounds such as succinimide, etc. Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, t-butylcyclohexane, dicyclohexyl and the like; methyl dimethyl phosphinate Ethyldimethylphosphinate, Ethyldiethylphosphinate, Trimethylphosphonoformate, Triethylphosphonoformate, Trimethylphosphonoacetate, Triethylphosphonoacetate, Trimethyl-3-phosphonopropionate And phosphorus-containing compounds such as triethyl-3-phosphonopropionate, ethylene sulfite, propylene sulfite, methyl methane sulfonate, ethyl methane sulfonate, methyl-methoxy methane sulfonate, methyl 2-methoxy ethane sulfonate, busulfan, diethylene glycol Dimethanesulfonate, 1,2-ethanediol bis (2,2,2-trifluoroethanesulfonate), 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate), sulfolane, 3-sulfolene, 2-sulfolene, dimethyl sulfone, diethyl sulfone, divinyl sulfone, diphenyl sulfone, bis (methylsulfonyl) methane, bis (methylsulfonyl) ethane, bis (ethylsulfonyl) methane, bis (ethyl ethane) Sulfur-containing compounds such as sulfonyl) ethane, bis (vinylsulfonyl) methane, bis (vinylsulfonyl) ethane, etc., lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, tetramethyl ammonium monofluorophosphate Monofluorophosphates such as tetraethylammonium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, tetramethylammonium difluorophosphate, tetraethylammonium difluorophosphate and the like, difluorophosphate, and succinate Acid, methylsuccinic anhydride, 4,4-dimethylsuccinic anhydride, 4,5-dimethylsuccinic anhydride, maleic anhydride, citraconic anhydride, dimethylmaleic anhydride, phenylmaleic anhydride, Eniru maleic anhydride, phthalic anhydride, cyclohexane 1,2-dicarboxylic acid anhydride, acetic anhydride, propionic anhydride, acrylic anhydride include acid anhydride such as methacrylic acid. Among these, succinic anhydride, maleic anhydride, methacrylic anhydride, and lithium difluorophosphate are preferable from the viewpoint of improving cycle characteristics and high-temperature storage characteristics. These may be used alone or in combination of two or more.

The content of these assistants in the non-aqueous electrolyte solution is not particularly limited, but is usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass or more, Usually, it is 8% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 2% by mass or less. It is preferable to add these assistants in terms of improving capacity retention characteristics and cycle characteristics after high temperature storage. When the concentration is in the above range, the effect of the auxiliary agent is easily exhibited, and the deterioration of the characteristics of the battery such as the high rate charge and discharge characteristics is suppressed.

[2. Negative electrode]
The negative electrode active material used for the negative electrode will be described below. The negative electrode active material is not particularly limited as long as it can electrochemically store and release lithium ions. Specific examples thereof include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. One of these may be used alone, or two or more of these may be used in combination as desired.

[2-1. Negative electrode active material]
Examples of the negative electrode active material include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like.
Examples of carbonaceous materials include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, (6) resin-coated graphite, etc. .

(1) Examples of natural graphite include scale-like graphite, scale-like graphite, soil graphite and / or graphite particles obtained by subjecting such graphite to a treatment such as spheroidization or densification. Among these, spherical or ellipsoidal graphite having a spheroidizing treatment is particularly preferable from the viewpoint of particle filling property and charge / discharge rate characteristics.
As an apparatus used for the spheroidizing process, for example, an apparatus which repeatedly gives mechanical action such as compression, friction, shear force and the like including impact force and particle interaction can be used. Specifically, it has a rotor having a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, and shear force is performed on the carbon material introduced inside. And a device for performing the spheronization process is preferred. In addition, it is preferable to have a mechanism in which the mechanical action is repeatedly given by circulating the carbon material.

  For example, when spheroidizing treatment is performed using the above-mentioned apparatus, the peripheral velocity of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and further preferably 50 to 100 m / sec. It is more preferable to do. Also, the treatment can be carried out simply by passing the carbonaceous matter, but it is preferable to treat by circulating or staying in the device for 30 seconds or more, and it is preferable to treat by circulating or staying in the device for 1 minute or more. More preferable.

  (2) As artificial graphite, coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are generally in the range of 2500 ° C. or more, usually 3200 ° C. or less What is graphitized at temperature, and grind | pulverized and / or classified as needed, and what is manufactured is mentioned. Under the present circumstances, a silicon containing compound, a boron containing compound, etc. can also be used as a graphitization catalyst. In addition, artificial graphite obtained by graphitizing mesocarbon microbeads separated in the heat treatment process of pitch may be mentioned. Furthermore, artificial graphite of granulated particles consisting of primary particles can also be mentioned. For example, by mixing mesograph microbeads, graphitizable carbonaceous material powder such as coke, graphitizable binder such as tar and pitch, and graphitization catalyst, graphitizing, and grinding as necessary A plurality of flat particles can be obtained, and graphite particles assembled or combined such that the orientation planes are not parallel may be mentioned.

(3) Amorphous carbon which is heat-treated once or more in a non-graphitizing temperature range (range of 400 to 2200 ° C.) using a graphitizable carbon precursor such as tar or pitch as a raw material as the amorphous carbon Non-graphitizable carbon precursors such as particles and resins may be used as the raw material to heat-treat amorphous carbon particles.
(4) As carbon-coated graphite, it can be obtained by mixing natural graphite and / or artificial graphite and a carbon precursor which is an organic compound such as tar, pitch or resin, and heat-treating at a temperature of 400 to 2300 ° C. once or more. Examples thereof include carbon-graphite composites in which natural graphite and / or artificial graphite are core graphite and amorphous carbon covers the core graphite. The form of the composite may be a whole or a part of the surface, or a plurality of primary particles composited with carbon derived from the carbon precursor as a binder. Also, carbon can be deposited (CVD) on the surface of graphite by reacting natural graphite and / or artificial graphite with hydrocarbon-based gas such as benzene, toluene, methane, propane, volatiles of aromatic series at high temperature, etc. Graphite composites can also be obtained.

(5) Graphite-coated graphite is prepared by mixing natural graphite and / or artificial graphite and a carbon precursor of a graphitizable organic compound such as tar or pitch, resin, etc., once in the range of about 2400 to 3200 ° C. The graphite coated graphite which makes natural graphite and / or artificial graphite which are obtained by heat processing above and / or artificial graphite as core graphite, and the graphitization coats the whole surface or a part of core graphite is mentioned.
(6) As the resin-coated graphite, natural graphite and / or artificial graphite are mixed with a resin etc. and dried at a temperature of less than 400 ° C. Natural graphite and / or artificial graphite obtained as core graphite are used as the resin. Resin-coated graphite which is coated with

Moreover, the carbonaceous material of (1)-(6) may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
As organic compounds such as tar, pitch and resin used in the above (2) to (5), coal-based heavy oil, direct current-based heavy oil, cracking-based petroleum heavy oil, aromatic hydrocarbon, N-ring compound And S-ring compounds, polyphenylenes, organic synthetic polymers, natural polymers, thermoplastic resins, and carbonizable organic compounds selected from the group consisting of thermosetting resins and the like. Moreover, in order to adjust the viscosity at the time of mixing, the raw material organic compound may be dissolved in a low molecular weight organic solvent and used.

Moreover, as natural graphite used as a raw material of nuclear graphite and / or artificial graphite, natural graphite subjected to a spheroidizing treatment is preferable.
As an alloy-based material used as a negative electrode active material, lithium alone, lithium single metal and alloy forming lithium alloy, or oxides, carbides, nitrides, silicides, sulfide thereof as long as lithium can be absorbed and released It may be any of compounds or compounds such as phosphides and is not particularly limited.

  The single metal and alloy forming the lithium alloy is preferably a material containing Group 13 and Group 14 metal / metalloid elements (ie excluding carbon), more preferably a single metal of aluminum, silicon and tin and It is an alloy or a compound containing these atoms. One of these may be used alone, or two or more of these may be used in any combination and ratio.

<Physical properties of carbonaceous materials>
When using a carbonaceous material as the negative electrode active material, it is desirable to have the following physical properties.

(X-ray parameters)
The d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction according to the Gakushin method of the carbonaceous material is usually 0.335 nm or more, and usually 0.360 nm or less, 0.350 nm The following are preferable, and 0.345 nm or less is more preferable. The crystallite size (Lc) of the carbonaceous material determined by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

(Volume-based average particle size)
The volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) determined by laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, 7 μm The above is particularly preferable, and usually, it is 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less.

If the volume-based average particle size is less than the above range, the irreversible capacity may increase, which may lead to the loss of the initial battery capacity. Moreover, when the said range is exceeded, when producing an electrode by application | coating, it will be easy to become a non-uniform coated surface, and it may be undesirable in the battery manufacture process.
In the measurement of the volume-based average particle size, a carbon powder is dispersed in a 0.2 mass% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate which is a surfactant, and laser diffraction / scattering type particle size distribution (For example, LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle size of the carbonaceous material of the present invention.

(Raman R value)
The Raman R value of the carbonaceous material is a value measured using a laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1. It is 5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

When the Raman R value is below the above range, the crystallinity of the particle surface may be too high, and the sites at which Li may enter into the layer may decrease as charge and discharge occur. That is, the chargeability may be reduced. In addition, when the negative electrode is densified by pressing after being applied to the current collector, crystals may be easily oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics.
On the other hand, if the above range is exceeded, the crystallinity of the particle surface may be reduced, the reactivity with the non-aqueous electrolyte solution may be increased, and the efficiency may be decreased or gas generation may be increased.

The measurement of the Raman spectrum is carried out by naturally dropping the sample into the measurement cell and filling it using a Raman spectrometer (for example, Raman spectrometer made by JASCO Corporation), and argon ion laser light (or semiconductor) on the sample surface in the cell It is carried out by rotating the cell in a plane perpendicular to the laser beam while irradiating the laser beam. The resulting Raman spectrum, the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and measuring the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) Calculate The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention.

Moreover, said Raman measurement conditions are as follows.
Laser wavelength: Ar ion laser 514.5 nm (semiconductor laser 532 nm)
・ Measurement range: 1100 cm ^{-1 to} 1730 cm ^-1
・ Raman R value: background processing,
・ Smoothing processing: Simple average, convolution 5 points

(BET specific surface area)
BET specific surface area of the carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m ² · ^{g -1} or more, 0.7 m ² · ^{g -1} or more, 1. 0 m ² · ^{g -1} or more, and particularly preferably 1.5 m ² · ^{g -1} or more, generally not more than 100 m ² · ^{g -1,} preferably ^{25 m} 2 · ^{g -1} or less, 15 m ² · g ^-1 or less is further preferable, and 10 m ² · g ^-1 or less is particularly preferable.

When the value of the BET specific surface area falls below this range, the acceptability of lithium at the time of charging when used as a negative electrode material tends to be poor, lithium is likely to be deposited on the electrode surface, and the stability may be reduced. On the other hand, if it exceeds this range, the reactivity with the non-aqueous electrolyte solution increases when used as a negative electrode material, gas generation tends to be large, and a preferable battery may be difficult to obtain.

  Measurement of the specific surface area by the BET method is carried out by predrying the sample at 350 ° C. for 15 minutes under flowing nitrogen using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken) and then measuring the atmospheric pressure. It is carried out by the nitrogen adsorption BET one-point method according to the gas flow method, using a nitrogen-helium mixed gas which is accurately adjusted so that the value of the relative pressure of nitrogen is 0.3.

(Roundness)
When the degree of circularity is measured as the degree of spherical shape of the carbonaceous material, it is preferable to fall within the following range. The circularity is defined as "circularity = (peripheral length of equivalent circle having the same area as the particle projection shape) / (actual peripheral length of the particle projection shape)", and when the circularity is 1, it is theoretical It becomes a true sphere.

  The circularity of particles having a particle diameter of the carbonaceous material in the range of 3 to 40 μm is preferably as close to 1 as possible, preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more. 0.85 or more is more preferable, and 0.9 or more is especially preferable. The high current density charge / discharge characteristics improve as the degree of circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material may be reduced, the resistance between particles may be increased, and the high current density charge / discharge characteristics may be deteriorated for a short time.

  The measurement of the degree of circularity is performed using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample is dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate which is a surfactant, and irradiated with ultrasonic waves of 28 kHz for 1 minute at a power of 60 W The detection range is specified to 0.6 to 400 μm, and measurement is performed on particles having a particle size in the range of 3 to 40 μm.

  The method for improving the degree of circularity is not particularly limited, but it is preferable to use a sphericization treatment to make it spherical since the shape of the interparticle voids when the electrode body is formed can be obtained. As an example of the spheroidizing process, a mechanical force or a mechanical processing method in which a plurality of fine particles are granulated by a binder or the adhesive force of the particles themselves by mechanically applying a shear force or a compressive force to a spherical shape Can be mentioned.

(Tap density)
The tap density of the carbonaceous material is usually 0.1 g · cm ⁻³ or more, preferably 0.5 g · cm ⁻³ or more, more preferably 0.7 g · cm ⁻³ or more, and 1 g · cm ⁻³ or more. In particular, 2 g · cm ³ or less is preferable, 1.8 g · cm ³ or less is more preferable, and 1.6 g · cm ³ or less is particularly preferable. When the tap density is lower than the above range, the packing density may not be easily increased when used as a negative electrode, and a high capacity battery may not be obtained. Moreover, when the said range is exceeded, the space | gap between particle | grains in an electrode will decrease too much, it will become difficult to ensure the conductivity between particle | grains, and it may be difficult to acquire a preferable battery characteristic.

The tap density is measured by passing the sample through a 300 μm mesh screen and dropping the sample into a 20 cm ³ tapping cell to fill the sample to the top end face of the cell, and then using a powder density measuring instrument (eg, Seishin Enterprise Co., Ltd.) Tap tapping is performed 1000 times using a stroke length of 10 mm, and the tap density is calculated from the volume at that time and the mass of the sample.

(Alignment ratio)
The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is below the above range, the high density charge and discharge characteristics may be degraded. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. A molded body obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm and compressing it at 58.8 MN · m ⁻² is set using clay to be flush with the surface of the sample holder for measurement. Measure X-ray diffraction. From the obtained peak intensities of (110) diffraction and (004) diffraction of carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated.

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

(Aspect ratio (powder))
The aspect ratio of the carbonaceous material is usually 1 or more, and usually 10 or less, preferably 8 or less, and more preferably 5 or less. When the aspect ratio exceeds the above range, streaking during electrode plate formation and a uniform coated surface can not be obtained, and the high current density charge / discharge characteristics may be degraded. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.

  The measurement of the aspect ratio is performed by magnifying and observing particles of the carbonaceous material with a scanning electron microscope. Carbon material material particles when selecting arbitrary 50 graphite particles fixed to the end face of metal having a thickness of 50 μm or less, rotating and tilting the stage on which the sample is fixed for each, and observing it three-dimensionally The longest diameter A and the shortest diameter B orthogonal to that are measured, and the average value of A / B is determined.

[2-2. Configuration and manufacturing method of negative electrode]
For production of the electrode, any known method can be used as long as the effects of the present invention are not significantly impaired. For example, a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler and the like are added to the negative electrode active material to form a slurry, which is applied to a current collector, dried and pressed. Can.
In addition, in the case of using an alloy-based material, a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a method such as vapor deposition method, sputtering method, plating method is also used.

(Electrode density)
The electrode structure when making the negative electrode active material into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g · cm ⁻³ or more Is more preferable, 1.3 g · cm ⁻³ or more is particularly preferable, and 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 More preferably, 1.9 g · cm ⁻³ or less is particularly preferable. When the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity increases, or the non-aqueous system near the current collector / negative electrode active material interface In some cases, the high current density charge / discharge characteristics may be deteriorated due to the decrease in the permeability of the electrolyte solution. If the above range is exceeded, the conductivity between the negative electrode active materials may be reduced, the battery resistance may be increased, and the capacity per unit volume may be reduced.

[3. Positive electrode]
[3-1. Positive electrode active material]
The positive electrode active material (lithium transition metal based compound) used for the positive electrode will be described below.
<Lithium transition metal compounds>
The lithium transition metal-based compound is a compound having a structure capable of releasing and inserting Li ions, and examples thereof include a sulfide, a phosphate compound, and a lithium transition metal composite oxide. The sulfide, and compounds having a two-dimensional layered structure, such as TiS ₂ and MoS _2, strong (in Me which various transition metals including Pb, Ag, and Cu) general formula _Me x _Mo 6 _S 8 represented by Compounds and the like having a three-dimensional skeletal structure. The phosphate compounds include those having an olivine structure, and are generally represented by LiMePO ₄ (Me is at least one transition metal), and specifically, LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , such as LiMnPO _4, and the like. As lithium transition metal complex oxide, what belongs to the spinel structure in which three-dimensional diffusion is possible, and the thing which belongs to the layered structure which enables two-dimensional diffusion of lithium ion is mentioned. Those having a spinel structure are generally represented as LiMe ₂ O ₄ (Me is at least one transition metal), and specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O ₄ and LiCoVO ₄ etc. Those having a layered structure are generally represented as LiMeO ₂ (Me is at least one or more transition metals). Specifically, LiCoO ₂ , LiNiO ₂ , LiNi _1-x Co _x O ₂ , LiNi _1-x-y Co _x Mn _y O ₂ , LiNi _0.5 Mn _0.5 O ₂ , Li _1.2 Cr _{0. 4} Mn _0.4 O ₂ , Li _1.2 Cr _0.4 Ti _0.4 O ₂ , LiMnO _{2 and the} like.

(composition)
Moreover, it is mentioned that a lithium containing transition metal compound is a lithium transition metal type-compound shown, for example by a following composition formula (A) or (B).
1) In the case of a lithium transition metal compound represented by the following composition formula (A) Li _{1 + x} MO ₂ (A)
However, x is usually 0 or more and 0.5 or less. M is an element composed of Ni and Mn, or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less. The Ni / M molar ratio is usually 0 or more and 0.5 or less. The Co / M molar ratio is usually 0 or more and 0.5 or less. In addition, the rich part of Li represented by x may be substituted by the transition metal site M.

  In the above composition formula (A), the atomic ratio of the amount of oxygen is described as 2 for convenience, but it may have some nonstoichiometry. Further, x in the above composition formula is a preparation composition at the production stage of the lithium transition metal based compound. Usually, batteries in the market are aged after the batteries are assembled. Therefore, the amount of Li in the positive electrode may be lost as a result of charge and discharge. In that case, x may be measured as −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

Further, the lithium transition metal-based compound is obtained by firing at a high temperature under an oxygen-containing gas atmosphere to improve crystallinity of the positive electrode active material, and the material is excellent in battery characteristics.
Furthermore, the lithium transition metal-based compound represented by the composition formula (A) may be a solid solution with Li ₂ MO ₃ called 213 layer as the following general formula (A ′).
α Li ₂ MO ₃ · (1-α) Li M'O ₂ (A ')
In the general formula, α is a number that satisfies 0 <α <1.

M is at least one metal element having an average oxidation number of 4 ⁺ , and more specifically, at least one metal element selected from the group consisting of Mn, Zr, Ti, Ru, Re, and Pt.
M ′ is at least one metal element having an average oxidation number of 3 ⁺ , preferably V,
It is at least one metal element selected from the group consisting of Mn, Fe, Co and Ni, more preferably at least one metal element selected from the group consisting of Mn, Co and Ni.

2) In the case of a lithium transition metal compound represented by the following general formula (B): Li [Li _a M _b Mn _{2-b a} ] O _{4 + δ} (B)
However, M is an element composed of at least one of transition metals selected from Ni, Cr, Fe, Co, Cu, Zr, Al and Mg.
The value of b is usually 0.4 or more and 0.6 or less.

If the value of b is in this range, the energy density per unit weight in the lithium transition metal based compound is high.
The value of a is usually 0 or more and 0.3 or less. Further, a in the above composition formula is a feed composition at the production stage of the lithium transition metal based compound. Usually, batteries in the market are aged after the batteries are assembled. Therefore, the amount of Li in the positive electrode may be lost as a result of charge and discharge. In that case, a may be measured at −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

If the value of a is in this range, good load characteristics can be obtained without significantly impairing the energy density per unit weight of the lithium transition metal based compound.
Furthermore, the value of δ is usually in the range of ± 0.5.
If the value of δ is in this range, the stability as a crystal structure is high, and the cycle characteristics and high temperature storage of a battery having an electrode manufactured using this lithium transition metal based compound are good.

Here, the chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal based compound, will be described in more detail below.
In order to obtain a and b of the composition formula of the lithium transition metal based compound, each transition metal and lithium are analyzed by inductively coupled plasma emission spectrometry (ICP-AES) to obtain the ratio of Li / Ni / Mn. Calculated by

From a structural point of view, it is considered that the lithium relating to a is substituted into the same transition metal site. Here, due to the lithium according to a, the average valence of M and manganese becomes larger than 3.5 according to the principle of charge neutrality.
Further, the above lithium transition metal-based compound may be fluorine-substituted and is described as LiMn ₂ O _4-x F _2x .

(blend)
Specific examples of the lithium transition metal-based compound of the above composition, for _{example, Li 1 + x Ni 0.5 Mn} 0.5 O 2, Li 1 + x Ni 0.85 Co 0.10 Al 0.05 O 2, Li 1 + x Ni _0.33 Mn _0.33 Co _0.33 O ₂ , Li _{1 + x} Ni _0.45 Mn _0.45 Co _0.1 O ₂ , Li _{1 + x} Mn _1.8 Al _0.2 O ₄ , Li _{1 + x} Mn _1.5 Ni _0.5 O ₄ etc. are mentioned. One of these lithium transition metal-based compounds may be used alone, or two or more thereof may be blended and used.

(Introduction of different elements)
In addition, different elements may be introduced into the lithium transition metal based compound. As different elements, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, I, As, Ge, P,
It is selected from any one or more of Pb, Sb, Si and Sn. These different elements may be incorporated into the crystal structure of the lithium transition metal based compound, or not incorporated into the crystal structure of the lithium transition metal based compound, either alone or as a compound on the particle surface or grain boundary. It may be unevenly distributed.

[3-2. Constitution and production method of positive electrode for lithium secondary battery]
The positive electrode for a lithium secondary battery is obtained by forming a positive electrode active material layer containing the above-mentioned lithium transition metal based compound powder for lithium secondary battery positive electrode material and a binder on a current collector.
In the positive electrode active material layer, a positive electrode material, a binder, and a conductive material, a thickener, etc., which are optionally used, are mixed in a dry state to form a sheet, and is pressed to the positive electrode current collector Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to a positive electrode current collector and dried.

  As a material of the positive electrode current collector, usually, a metal material such as aluminum, stainless steel, nickel plating, titanium, tantalum or the like, or a carbon material such as carbon cloth or carbon paper is used. Further, as the shape, in the case of metal material, metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal etc., in the case of carbon material, carbon plate, carbon thin film, carbon cylinder Etc. The thin film may be formed in a mesh shape as appropriate.

When a thin film is used as the positive electrode current collector, the thickness thereof is arbitrary, but a range of 1 μm to 100 mm is usually preferable. If the thickness is thinner than the above range, the strength required for the current collector may be insufficient, while if it is thicker than the above range, the handleability may be impaired.
The binder used to manufacture the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that is stable to the liquid medium used at the time of electrode manufacture may be used. Specific examples include polyethylene, Resin polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene・ Rubber-like polymers such as propylene rubber, styrene / butadiene / styrene block copolymers and hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymers), styrene / ethylene / butadiene / ethylene copolymers, Styrene · Isoprene Styrene Bro Thermoplastic elastomeric polymers such as co-polymers and their hydrogenated products, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefin copolymers, etc. Ion conductivity of soft polymer, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene, fluorinated polymer such as polytetrafluoroethylene-ethylene copolymer, alkali metal ion (especially lithium ion) The polymer composition etc. which it has are mentioned. These substances may be used alone or in any combination of two or more with any proportion.

The proportion of the binder in the positive electrode active material layer is usually 0.1% by mass or more and 80% by mass or less. When the proportion of the binder is too low, the positive electrode active material can not be sufficiently retained, the mechanical strength of the positive electrode is insufficient, and battery performance such as cycle characteristics may be deteriorated. It may lead to a decrease in battery capacity and conductivity.
The positive electrode active material layer usually contains a conductive material to enhance the conductivity. The type is not particularly limited, but specific examples thereof include metal materials such as copper and nickel, graphite such as natural graphite, artificial graphite and the like, carbon black such as acetylene black, amorphous carbon such as needle coke and the like And carbon materials of the These substances may be used alone or in any combination of two or more with any proportion. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by mass or more and 50% by mass or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and if too high, the battery capacity may decrease.

  As a liquid medium for forming a slurry, it is possible to dissolve or disperse a lithium transition metal based compound powder which is a positive electrode material, a binder, and a conductive material and a thickener which are optionally used. The type of the solvent is not particularly limited, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methyl pyrrolidone (NMP), dimethylformamide, dimethyl acetamide, methyl acetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyl triamine, N , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethyl acetamide, hexamethyl phosphaamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methyl naphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, a dispersant is added to the thickener together with the thickener, and a slurry such as SBR is used. In addition, one of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.

The content ratio of the lithium transition metal based compound powder as the positive electrode material in the positive electrode active material layer is usually 10% by mass or more and 99.9% by mass or less. When the proportion of the lithium transition metal based compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and when it is too small, the capacity may be insufficient.
The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

The density of the positive electrode after pressing is usually 2.2 g / cm ³ or more and 4.2 g / cm ³ or less.
In order to increase the packing density of the positive electrode active material, the positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like.

[4. Separator]
In order to prevent a short circuit, a separator is usually interposed between the positive electrode and the negative electrode. In this case, the non-aqueous electrolytic solution of the present invention is usually used by impregnating this separator.
The material and shape of the separator are not particularly limited, and any known ones can be adopted as long as the effects of the present invention are not significantly impaired. Among them, resins, glass fibers, inorganic substances, etc., which are made of a material stable to the non-aqueous electrolyte solution of the present invention, are used, and porous sheet or non-woven fabric-like articles etc. excellent in liquid retention are used. Is preferred.
As a material of resin and a glass fiber separator, polyolefins, such as polyethylene and a polypropylene, aromatic polyamide, polytetrafluoroethylene, polyether sulfone, a glass filter etc. can be used, for example. Among them, preferred are glass filters and polyolefins, and more preferred are polyolefins. One of these materials may be used alone, or two or more of these materials may be used in any combination and ratio.

  The thickness of the separator is arbitrary but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less. If the separator is thinner than the above range, the insulation and mechanical strength may be reduced. When the thickness is more than the above range, not only the battery performance such as rate characteristics may be degraded, but also the energy density of the whole non-aqueous electrolyte secondary battery may be degraded.

Furthermore, when a porous sheet such as a porous sheet or non-woven fabric is used as the separator, the porosity of the separator is optional, but is usually 20% or more, preferably 35% or more, and more preferably 45% or more, Also, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. When the porosity is smaller than the above range, the film resistance tends to be increased and the rate characteristic tends to be deteriorated. Moreover, when it is larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

The average pore diameter of the separator is also optional, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. When the average pore size exceeds the above range, a short circuit is likely to occur. If the above range is exceeded, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used, and those having a particle shape or fiber shape are used. Used.

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

  The characteristics of the non-electrolyte secondary battery of the separator can be grasped by the Gurley value. The Gurley value indicates the difficulty of air passing through in the film thickness direction, and since 100 ml of air is represented by the number of seconds required to pass through the film, smaller numbers are easier to pass through and larger numbers are larger. It means that one is more difficult to pass through. That is, the smaller the value, the better the communication in the thickness direction of the film, and the larger the value, the worse the communication in the thickness direction of the film. The communication property is the degree of connection of the holes in the film thickness direction. If the Gurley value of the separator of the present invention is low, it can be used in various applications. For example, when it is used as a separator of a non-aqueous lithium secondary battery, a low Gurley value means that lithium ions can be easily moved, which is preferable because the battery performance is excellent. The Gurley value of the separator is optionally but preferably 10 to 1000 seconds / 100 ml, more preferably 15 to 800 seconds / 100 ml, and still more preferably 20 to 500 seconds / 100 ml. If the Gurley value is 1000 seconds / 100 ml or less, the electric resistance is substantially low and it is preferable as a separator.

[5. Battery design]
<Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate described above are intervened by the separator, and a structure in which the positive electrode plate and the negative electrode plate are spirally wound through the separator. Any one 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, preferably 80% or less .

  When the electrode group occupancy rate falls below the above range, the battery capacity decreases. Further, when the above range is exceeded, the void space is small, the battery becomes high temperature, the members expand, the vapor pressure of the liquid component of the electrolyte becomes high, and the internal pressure rises, and the charge and discharge repetition performance as the battery Or, the characteristics such as high temperature storage may be lowered, and furthermore, a gas release valve may be actuated to release the internal pressure to the outside.

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

  In the outer case using metals, the metals are welded to form a hermetically sealed structure by laser welding, resistance welding, ultrasonic welding, or a caulking structure is formed using the above metals via a resin gasket. The thing is mentioned. In the outer case using the above-mentioned laminated film, those having a sealing and sealing structure by thermally fusing the resin layers to each other may be mentioned. 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, in the case where the resin layer is heat-sealed through the current collection terminal to form a sealed structure, the metal and the resin are joined, and therefore, a resin having a polar group or a modification having a polar group introduced as an intervening resin Resin is preferably used.

<Protective element>
As a protection element, PTC (Positive Temperature Coefficient), whose resistance increases when abnormal heat generation or excessive current flows, thermal fuse, thermistor, interrupt the current flowing in the circuit due to rapid increase of internal pressure of battery and internal temperature at abnormal heat generation. Valve (current shutoff valve) etc. can be used. The protective element is preferably selected under conditions which do not operate under normal use of high current, and it is more preferable to design it so as not to lead to abnormal heat generation or thermal runaway without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually constructed by housing the above-described non-aqueous electrolyte, negative electrode, positive electrode, separator and the like in an outer package. The outer package is not particularly limited, and any known one can be adopted as long as the effects of the present invention are not significantly impaired. Specifically, the material of the outer package is optional, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium or the like is used.

  The shape of the outer package is also arbitrary, and may be, for example, cylindrical, square, laminate, coin or large size.

  EXAMPLES Hereinafter, the present invention will be more specifically described by way of examples and comparative examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

[Examples 1 to 14, Comparative Examples 1 to 8]
<Preparation of Nonaqueous Electrolyte>
Non-aqueous solvent mixed with ethylene carbonate (hereinafter EC), ethyl methyl carbonate (hereinafter EMC) and diethyl carbonate (hereinafter DEC) in a dry argon atmosphere so as to be 30% by volume, 40% by volume and 30% by volume respectively On the other hand, LiPF ₆ was dissolved to be 1.2 M. The additives described in “Table 1” were added thereto to prepare a non-aqueous electrolytic solution. Each abbreviation in the table indicates the following.

VC: vinylene carbonate,
FEC: fluoro ethylene carbonate,
Compound Z1: 1,3-propane sultone,
Compound Z2: Adiponitrile,
Compound Z3: lauronitrile,
Compound Z4: Octanenitrile,
Compound A1: 1,3-bis (isocyanatomethyl) cyclohexane,
Compound A2: triallyl isocyanurate,
Compound A3: Tris (2-acryloxyethyl) isocyanurate,
Compound A4: tetramethylolmethane tetraacrylate.

<Fabrication of negative electrode>
To 98 parts by mass of a graphite powder as a negative electrode active material, 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose and 1 part by mass of an aqueous dispersion of styrene-butadiene rubber are added as a thickener and a binder, respectively, and mixed with a disperser And made into a slurry. The obtained slurry was applied to one side of a copper foil, dried and pressed to form a negative electrode. The produced negative electrode was used after drying under reduced pressure at 60 ° C. for 12 hours.

<Fabrication of positive electrode>
To 96.8 parts by mass of lithium cobaltate as a positive electrode active material, 1.6 parts by mass of a conductive additive and 1.6 parts by mass of a binder (pVDF) were added and mixed by a disperser to form a slurry. The obtained slurry was applied to both sides of an aluminum foil, dried and pressed to form a positive electrode. The produced positive electrode was used after drying under reduced pressure at 80 ° C. for 12 hours.

<Fabrication of battery>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode to produce a battery element. The 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, with the positive and negative terminals protruding, and then the non-aqueous electrolyte 0.4 mL in the bag It injected | poured and vacuum-sealed, and produced the sheet-like battery. Furthermore, in order to enhance the adhesion between the electrodes, the sheet battery was sandwiched between the glass plates and pressurized.

<Characteristics evaluation test 1>
1. Cycle Test The battery produced as described above was charged to 4.35 V at 25 ° C., discharged to 3 V, and conditioned until the capacity was stabilized. Thereafter, a cycle test in which charging to 4.35 V and discharging to 3 V were repeated in an environment of 45 ° C. was performed at a current value of 0.5 C for 200 cycles. Here, 0.5 C is a current value that takes 2 hours to charge or discharge. The ratio of the discharge capacity at the 200th cycle to the discharge capacity at the first cycle is summarized in “Table 1” as “cycle capacity retention ratio (%)”.

2. High-Temperature Storage Test The battery produced as described above was charged to 4.35 V at 25 ° C., discharged to 3 V, and conditioned until the capacity was stabilized. Thereafter, the battery charged to 4.35 V was left for 3 days under an environment of 80 ° C. The amount of gas generation (mL) at this time was measured by the Archimedes method, and the ratio (%) to 0.1 (mL) was summarized in “Table 1” as “high temperature storage gas amount (%)”.

3. High Rate Discharge Test The battery produced as described above was charged to 4.35 V at 25 ° C., discharged to 3 V, and conditioned until the capacity was stabilized. After that, when the battery charged to 4.35 V is discharged to 3 V at a current value of 0.2 C under an environment of 25 ° C., the capacity is 0.2 C and the battery charged again to 4.35 V is 25 ° C. Assuming that the capacity when discharged to 3 V at a current value of 1.0 C under the environment is 1.0 C capacity, the ratio (%) of the 1.0 C capacity to the 0.2 C capacity is “high rate discharge rate (%) As ", it put together in" Table 1 ".

  In the results shown in "Table 1", as reference for each characteristic, the cycle capacity retention rate (%) is 85 or less, the high temperature storage gas amount (%) is 100 or more, and the high rate discharge rate (%) is 90 or less (*) Marked. As apparent from this, in the embodiment using the electrolytic solution of the present invention, all the characteristics are performances above the standard, while any one of X, Y, Z, A deviates from the range. When an electrolytic solution not included in the invention is used, one or more of the cycle capacity retention rate, the amount of high-temperature storage gas, and the high rate discharge rate become lower than the standard, and all the properties can not be satisfied. Recognize. For example, the content A of the comparative example 1 is 0.5, which deviates from the range of A, so that the cycle capacity retention rate and the high rate discharge rate were low. In Comparative Examples 2 and 3, the content Y is 0 and deviates from the range of Y, so the cycle capacity retention rate is low, and in Comparative Example 2, the high rate discharge rate is also low. Similarly, also in Comparative Example 4, since the content Y is 10, the amount of high-temperature storage gas becomes very large. In Comparative Example 5, since the content X was 1 and deviated from the range of X, the cycle capacity retention rate and the high-rate discharge rate decreased, and the amount of high-temperature storage gas increased. In Comparative Examples 6 and 7, since the content Z is out of the range, the cycle capacity retention rate is low, and the amount of high-temperature storage gas is large.

[Examples 15 to 18, Comparative Examples 9 to 11]
<Characteristics evaluation test 2>
1. Cycle Test The battery produced as described above was charged to 4.4 V at 25 ° C., discharged to 3 V, and conditioned until the capacity was stabilized. After that, 4.4V at 45 ° C
A cycle test of repeating charging to 3 V and discharging to 3 V was performed at a current value of 0.7 C for 500 cycles. The ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle is summarized in Table 2 as a cycle capacity retention rate (%).

2. High-Temperature Storage Test The battery produced as described above was charged to 4.4 V at 25 ° C., discharged to 3 V, and conditioned until the capacity was stabilized. Thereafter, the battery charged to 4.4 V was left for 3 days under an environment of 80 ° C. The amount of gas generation (mL) at this time was measured by the Archimedes method, and the ratio (%) to 0.1 (mL) was summarized in “Table 2” as the amount of high-temperature storage gas (%).

  In the results shown in "Table 2", those with a cycle capacity retention rate (%) of 70 or less and a high temperature storage gas amount (%) of 100 or more were marked with an asterisk (*). As apparent from this, in the embodiment using the electrolytic solution of the present invention, all the characteristics are performances above the standard, while any one or more of X, Y, Z and A deviate from the range. It can be seen that when the electrolytic solution not included in the present invention is used, any one or more of the cycle capacity retention rate and the amount of high temperature storage gas, or a plurality of characteristics become lower than the standard and all characteristics can not be satisfied.

According to the non-aqueous electrolytic solution of the present invention, the decomposition of the electrolytic solution of the non-aqueous electrolytic solution secondary battery is suppressed, and when the battery is used in a high temperature environment, gas generation and deterioration of the battery are suppressed and high energy density The non-aqueous electrolyte secondary battery can be manufactured. Moreover, it can utilize suitably also in electrolytic capacitors, such as a lithium ion capacitor which uses a non-aqueous electrolyte solution.
The application of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various known applications. Examples include laptops, pen-based PCs, mobile PCs, e-book players, mobile phones, mobile faxes, mobile copying, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini discs, transceivers Electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, motor, car, bike, motorized bicycle, bicycle, lighting equipment, toy, game machine, watch, electric tool, strobe, camera, large size for home use A storage battery etc. can be mentioned.

Claims (4)

A non-aqueous electrolyte solution for use in a non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of absorbing and desorbing metal ions and a negative electrode having a negative electrode active material capable of absorbing and desorbing metal ions ,
The content of vinylene carbonate is X (mass%),
The content of fluoroethylene carbonate is Y (mass%),
The content of at least one compound selected from 1,3-propane sultone, adiponitrile, lauronitrile and octane nitrile is Z (% by mass),
1,3-bis (isocyanatomethyl) cyclohexane, triallyl isocyanurate,
Tris (2-acryloxyethyl) isocyanurate and tetramethylol methanete
The content of at least one compound selected from La acrylate A (wt%), and then when there was <br/>, nonaqueous electrolyte, characterized in that all of the following equation.
0 ≦ X ≦ 0.5
0.5 ≦ Y ≦ 8.0
0.8 ≦ Z ≦ 6.0
0.8 ≦ A ≦ 5.0
However, the content refers to the ratio (% by mass) of each compound to the total weight of the non-aqueous electrolyte, and when two or more compounds are contained, X, Y, Z, and A indicate the total amount thereof. Said Z (mass%) is content of said 1, 3- propane sultone , 1.0 <= Z <= 4.0
The nonaqueous electrolytic solution according to claim 1, wherein the nonaqueous electrolytic solution contains Said Z (mass%) is content of an adiponitrile , 1.0 <= Z <= 4.0
The nonaqueous electrolytic solution according to claim 1, wherein the nonaqueous electrolytic solution contains A non-aqueous electrolyte secondary battery comprising: a positive electrode having a positive electrode active material capable of absorbing and desorbing metal ions; and a negative electrode having a negative electrode active material capable of absorbing and desorbing metal ions, A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte according to any one of the items.