JP6915955B2 - Non-aqueous electrolyte solution and non-aqueous electrolyte solution secondary battery using it - Google Patents

Description

The present invention relates to a non-aqueous electrolyte solution and a non-aqueous electrolyte 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. Has been done.

The electrolyte used in a non-aqueous electrolyte battery is generally composed mainly of an electrolyte and a non-aqueous solvent. As the electrolytic solution of the lithium ion secondary battery, an electrolyte such as LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ is used, a high dielectric constant solvent such as ethylene carbonate or propylene carbonate, and dimethyl carbonate, diethyl carbonate, or ethyl. A non-aqueous electrolyte solution dissolved in a mixed solvent with a low-viscosity solvent such as methyl carbonate is used.

When a lithium ion secondary battery is repeatedly charged and discharged, the electrolyte decomposes on the electrodes and the materials constituting the battery deteriorate, resulting in a decrease in the capacity of the battery. In some cases, the safety against swelling, ignition, explosion, etc. of the battery may be reduced.

So far, a method of improving the battery characteristics of a lithium ion secondary battery by incorporating a specific additive in a non-aqueous electrolytic solution has been proposed. For example, Patent Document 1 reports effects such as improvement of initial charge / discharge efficiency, suppression of leakage current, and improvement of load characteristics after high-temperature storage by containing an isocyanuric acid derivative in the electrolytic solution. Further, in Patent Documents 2 and 3, by containing a compound that becomes poorly soluble in the electrolytic solution when it is electrochemically decomposed in the electrolytic solution, leakage current is suppressed and the capacity residual rate after high temperature storage is improved. The effect has been reported.

Japanese Unexamined Patent Publication No. 2000-348765 Japanese Unexamined Patent Publication No. 2001-057234 Japanese Unexamined Patent Publication No. 2001-057235

In the present invention, in a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte using a non-aqueous electrolyte capable of producing a battery with low gas generation and excellent cycle characteristics, and a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte can be used. The challenge is to provide.

Patent Documents 1 to 3 certainly contribute to the improvement of various characteristics, but gas generation, which is particularly important for battery safety, has not been solved at all, and the cycle characteristics, which are important for battery characteristics, are further improved. That was not proven.

As a result of various studies to solve the above problems, the present inventor has found that the above problems can be solved when a compound having a specific structure (compound of formula 1) and a compound having a specific solvent composition or characteristics are combined. , The present invention has been completed.

（Ｒ^１、Ｒ^２、Ｒ^３は、それぞれ独立に有機基を表し、Ｒ^１、Ｒ^２、Ｒ^３の少なくとも１つは不飽和結合を有する有機基を表す。）
（b） 前記（ａ）において
０．１＜Ｘ／Ｙ＜１．０であることを特徴とする非水系電解液。
（c） 前記（ａ）〜（ｂ）において
０．１５＜Ｘ／Ｙ＜０．６であることを特徴とする非水系電解液。
（d） 前記（ａ）〜（ｃ）において
１０＜Ｘ＋Ｙ＜４０であることを特徴とする非水系電解液。
（e） 前記（ａ）〜（ｄ）において
１５＜Ｘ＋Ｙ＜３５であることを特徴とする非水系電解液。
（f） 前記（ａ）〜（ｅ）において
フッ素化環状カーボネート、Ｓ＝Ｏ結合を有する環状化合物またはニトリル化合物の少なくとも１種をさらに含有することを特徴とする非水系電解液。
（g） 金属イオンを吸蔵・放出しうる正極活物質を有する正極と、金属イオンを吸蔵・放出しうる負極活物質を有する負極とを備える非水系電解液二次電池に用いられる非水系電解液であって、
下記一般式（１）で表される化合物を含有し、
さらにフッ素化環状カーボネート、Ｓ＝Ｏ結合を有する環状化合物またはニトリル化合物の少なくとも１種をさらに含有することを特徴とする非水系電解液。

（Ｒ^１、Ｒ^２、Ｒ^３は、それぞれ独立に有機基を表し、Ｒ^１、Ｒ^２、Ｒ^３の少なくとも１つは不飽和結合を有する有機基を表す。）
（h） 前記（ｆ）〜（ｇ）に記載のフッ素化環状カーボネートがフルオロエチレンカーボネートであり、Ｓ＝Ｏ結合を有する環状化合物が１，３−プロパンスルトン、１，４−ブタンスルトン、１，３−プロペンスルトン、硫酸エチレンのうち少なくとも１種であり、ニトリル化合物がブチロニトリル、ラウロニトリル、クロトノニトリル、スクシノニトリル、アジポニトリル、ピメロニトリル、セバコニトリルのうち少なくとも１種であることを特徴とする非水系電解液。
（i） 前記（ａ）〜（ｈ）において、（１）式で表される化合物が、いかに示す化合物であることを特徴とする、非水系電解液。

（j） 金属イオンを吸蔵・放出しうる正極活物質を有する正極と、金属イオンを吸蔵・放出しうる負極活物質を有する負極とを備える非水系電解液二次電池であって、
前記（ａ）〜（ｉ）のいずれかに記載の非水系電解液を用いることを特徴とする非水系電解液二次電池。
That is, the gist of the present invention is
(A) Non-aqueous electrolyte solution having a positive electrode having a positive electrode active material capable of storing and releasing metal ions and a negative electrode having a negative electrode active material capable of storing and releasing metal ions Non-aqueous electrolyte solution used in a secondary battery And
Contains the compound represented by the following general formula (1),
The non-aqueous solvent contains both ethylene carbonate and propylene carbonate, and is characterized by 0 <X / Y <1.5 when the volume% of ethylene carbonate is X and the volume % of propylene carbonate is Y. Non-aqueous electrolyte.

(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.)
(B) A non-aqueous electrolyte solution having 0.1 <X / Y <1.0 in (a) above.
(C) A non-aqueous electrolyte solution having 0.15 <X / Y <0.6 in the above (a) to (b).
(D) A non-aqueous electrolyte solution having 10 <X + Y <40 in the above (a) to (c).
(E) A non-aqueous electrolyte solution having 15 <X + Y <35 in the above (a) to (d).
(F) A non-aqueous electrolytic solution further containing at least one of the fluorinated cyclic carbonate, the cyclic compound having an S = O bond, or the nitrile compound in the above (a) to (e).
(G) Non-aqueous electrolyte solution having a positive electrode having a positive electrode active material capable of storing and releasing metal ions and a negative electrode having a negative electrode active material capable of storing and releasing metal ions Non-aqueous electrolyte solution used for a secondary battery And
Contains the compound represented by the following general formula (1),
A non-aqueous electrolyte solution further containing at least one of a fluorinated cyclic carbonate, a cyclic compound having an S = O bond, or a nitrile compound.

(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.)
(H) The fluorinated cyclic carbonate according to (f) to (g) above is a fluoroethylene carbonate, and the cyclic compounds having an S = O bond are 1,3-propane sultone, 1,4-butan sultone, and 1,3. -Non-aqueous electrolysis characterized in that it is at least one of propensultone and ethylene sulfate, and the nitrile compound is at least one of butyronitrile, lauronitrile, crotononitrile, succinonitrile, adiponitrile, pimeronitrile, and sebaconitrile. liquid.
(I) A non-aqueous electrolyte solution, characterized in that the compound represented by the formula (1) in the above (a) to (h) is a compound represented by the above.

(J) A non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of storing and releasing metal ions and a negative electrode having a negative electrode active material capable of storing and releasing metal ions.
A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte solution according to any one of (a) to (i).

According to the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery that generates less gas and has excellent cycle characteristics.

It is a figure which shows the relationship between the battery of Examples 1-5 and the comparative example 1-3 and the amount of gas generated. It is a figure which shows the relationship between the battery of Example 2-1-2-3 and Comparative Example 2-1 and the cycle capacity retention rate. It is a figure which shows the relationship between the battery of Examples 3-1 to 3-2 and Comparative Example 3-1 and a cycle capacity retention rate.

Hereinafter, embodiments for carrying out the present invention will be described 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 as long as the gist described in the claims is not exceeded.

（Ｒ^１、Ｒ^２、Ｒ^３は、それぞれ独立に有機基を表し、Ｒ^１、Ｒ^２、Ｒ^３の少なくとも１つは不飽和結合を有する有機基を表す。）
[1. Non-aqueous electrolyte solution]
The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, similar to a general non-aqueous electrolyte solution.
Contains the compound represented by the following general formula (1),
The non-aqueous solvent contains both ethylene carbonate and propylene carbonate, and is characterized by 0 <X / Y <1.5 when the volume% of ethylene carbonate is X and the volume % of propylene carbonate is Y. or,
Contains the compound represented by the following general formula (1),
Further, it further contains at least one of a fluorinated cyclic carbonate, a cyclic compound having an S = O bond, or a nitrile compound.

(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.)

（Ｒ^１、Ｒ^２、Ｒ^３は、それぞれ独立に有機基を表し、Ｒ^１、Ｒ^２、Ｒ^３の少なくとも１つは不飽和結合を有する有機基を表す。） The non-aqueous electrolyte solution of the present invention contains a compound represented by the following general formula (1) and contains a compound represented by the following general formula (1).
Further, it is characterized by further containing at least one of a fluorinated cyclic carbonate, a cyclic compound having an S = O bond, or a nitrile compound.

(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.)

[1-1. Compound of formula (1)]
^{R 1} , R ² , and R ³ in the formula (1) according to claim 1 each independently represent an organic group, and ^{at least one of R 1} , R ² , and R ³ is an organic group having an unsaturated bond. Represents.

Specific examples of the above-mentioned organic group include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, and a group in which they have an organic functional group.

Specific examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, amyl group, t-amyl group, 2-ethylhexyl group and the like. Can be mentioned.

Specific examples of the fluorinated alkyl group include fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2-fluoroethyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group and pentafluoro. Ethyl group and the like can be mentioned.

Specific examples of the alkyl group having an organic functional group include a methoxymethyl group, an ethoxymethyl group, a methoxyethyl group, an ethoxyethyl group, a methoxycarbonylmethyl group, an ethoxycarbonylmethyl group, a methoxycarbonylethyl group, an ethoxycarbonylethyl group, and 2 -Acryloyloxymethyl group, 2-methacryloyloxymethyl group, 2-acryloyloxyethyl group, 2-methacryloyloxyethyl group and the like can be mentioned.

Specific examples of the alkenyl group include a vinyl group, an allyl group, a 2-butenyl group, a metharyl group and the like.

Specific examples of the alkynyl group include an ethynyl group and a propargyl group.

Specific examples of the aryl group include a phenyl group, a 2-tolyl group, a 3-tolyl group, a 4-tolyl group, a 2-t-butylphenyl group, a 3-t-butylphenyl group, and a 4-t-butylphenyl group. Groups, 2-t-amylphenyl group, 3-t-amylphenyl group, 4-t-amylphenyl group and the like.

Specific examples of the compound of the formula (1) include the following compounds.

Among the above compounds, it is preferable to use the following compounds.

Since these compounds are relatively easy to obtain and manufacture and have appropriate reactivity, they have a great effect of improving battery characteristics.

The non-aqueous electrolyte solution of the present invention is characterized by containing the compound of the formula (1), but the compound of the formula (1) contained may be used alone or in combination of a plurality of types. May be good.

The content of the compound of the formula (1) (total amount when a plurality of types are used in combination) is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.01% by mass or more, based on the total amount of the non-aqueous electrolyte solution. Is 0.1% by mass or more, more preferably 0.2% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and most preferably 1% by mass or less. Is. Within the above range, not only a stable film can be formed, but also an increase in resistance can be suppressed, so that it can be expected that the battery characteristics are particularly improved.

1-1. Cyclic carbonate compound having a fluorine atom Examples of the cyclic carbonate compound having a fluorine atom include 1,1,2-trifluoroethylene carbonate, tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, and 1-fluoro-1. -Methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate and the like can be mentioned. Of these, 1-fluoro-2-methylethylene carbonate is 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 non-aqueous electrolyte solution contains a cyclic carbonate compound having a fluorine atom, the content in the non-aqueous electrolyte solution is usually 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.3. It is 0% by mass or more, more preferably 0.5% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less. However, fluoroethylene carbonate may be used as a solvent, and in that case, the content is not limited to the above.

1-2. Cyclic compounds having an S = O bond Examples of the cyclic compound having an S = O bond include cyclic sulfite esters such as ethylene sulphite and propylene sulphite, 1,3-propane sultone, 1,4-butane sultone, and 1,3-propen. Examples thereof include cyclic sulfonic acid esters such as sultone and 1,4-butene sultone, cyclic sulfones such as sulfolane, 3-sulfolene and 2-sulfolene, cyclic sulfate esters such as ethylene sulfate, propylene sulfate, butylene sulfate and ethylene propyl sulfate.
Of these, 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, and ethylene sulfate 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 a cyclic compound having an S = O bond is contained, the content in the non-aqueous electrolyte solution is usually 0.001% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more. It is more preferably 0.5% by mass or more, usually 10% by mass or less, preferably 5% by mass or less, more preferably 4% by mass or less, still more preferably 3% by mass or less.

1-3. Nitrile compound The nitrile compound is not limited as long as it has a nitrile group (CN group), but the following are preferably used.

1) Mononitrile acetonitrile, propionitrile, butyronitrile, pentannitrile, hexanenitrile, heptanenitrile, octanenitrile, nonanenitrile, decannitrile, dodecanenitrile (lauronitrile), tridecanenitrile, tetradecanenitrile (myristonitrile), hexadecane Nitrile, pentadecanenitrile, heptadecanenitrile, octadecanenitrile (steanonitrile), nonadecannitrile, icosannitrile, acrylonitrile, crotononitrile, methacrylonitrile, cinnamonitrile, 3-methoxyacrylonitrile, 3-ethoxyacrylonitrile, 3 − Methoxypropionitrile, etc.

2) Dinitrile Marononitrile, Succinonitrile, Glutaronitrile, Adiponitrile, Pimeronitrile, Suberonitrile, Azelanitrile, Sevaconitrile, Undecandinitrile, Dodecandinitrile, Methylmalononitrile, Ethylmalononitrile, Isopropylmalononitrile, tert-butylmalononitrile, Methyl Succinonitrile, 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, trimethylsuccinonitrile, tetramethylsuccinonitrile, 2-methylglutaronitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, 3,3'-(ethylenedioxy) dipropionitrile, 3,3'-(ethylenedithio) dipropionitrile, fumalonitrile, etc.

3) Compounds having 3 or more nitrile groups 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, 1,2,3-tris (2-cyanoethoxy) propane, tris (2) -Cyanoethyl) amine, etc.

Among the above, butyronitrile, lauronitrile, crotononitrile, succinonitrile, adiponitrile, pimeronitrile, and sebaconitrile are preferable. These nitriles are preferable when used in combination with the formula (1) of the present invention because the battery characteristics are particularly improved.

When the non-aqueous electrolyte solution of the present invention contains nitrile, one type of nitrile may be used alone, or a plurality of types may be used in combination.

The nitrile content (total amount when a plurality of types are used in combination) is 0.01% by mass or more and less than 10% by mass with respect to the total amount of the non-aqueous electrolyte solution, and is preferably 0.1% by mass as the lower limit. % Or more, more preferably 0.5% by mass or more, and the upper limit value is preferably 8% by mass or less, more preferably 5% by mass or less, and most preferably 3% by mass or less. Within the above range, it can be expected that the battery characteristics are particularly improved without impairing the effect of the compound of the formula (1).

[1-3. Electrolytes〕
There is no limitation on the electrolyte used for the non-aqueous electrolyte solution of the present invention, and any known electrolyte can be used as long as it is used as an electrolyte in the target non-aqueous electrolyte secondary battery. When the non-aqueous electrolyte solution of the present invention is used in a lithium secondary battery, a lithium salt is usually 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, and 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-hexafluoropropanedisulfonylimide, Lithium cyclic 1,2-tetrafluoroethanedisulfonylimide, 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 and} other fluorine-containing organic lithium salts;
Examples thereof include dicarboxylic acid complex lithium salts containing lithium bis (oxalat) borate, lithium difluorooxalat borate, lithium tris (oxalat) phosphate, lithium difluorobis (oxalat) phosphate, lithium tetrafluoro (oxalat) phosphate and the like.

Of these, LiPF ₆ , LiBF ₄ , LiSO ₃ F, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) ( CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium bis (oxalate) borate, Lithium difluorooxalate borate, Lithium tris (oxalate) phosphate, Lithium difluorobis ( Oxalato) phosphate and lithium tetrafluoro (oxalat) phosphate are preferable, and LiPF ₆ and LiBF ₄ are particularly preferable.

In addition, one type of electrolyte may be used alone, or two or more types may be used in any combination and ratio. Among them, when two kinds of specific inorganic lithium salts are used in combination, or when an inorganic lithium salt and a fluorine-containing organic lithium salt are used in combination, gas generation during trickle charging is suppressed and deterioration after high temperature storage is suppressed. Therefore, it is preferable. In particular, the combined use of _{LiPF 6} and LiBF ₄ , the use of inorganic lithium salts such as _{LiPF 6} and LiBF _{4 , and LiCF 3} SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _2, etc. It is preferable to use it in combination with a fluorine-containing organolithium salt.

Further, when LiPF ₆ and LiBF ₄ are used in combination, _{it is preferable that LiBF 4} is usually contained 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, and 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 can be 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 and LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F) ₅ SO ₂ ) ₂ , Lithium cyclic 1,3-hexafluoropropanedisulfonylimide, Lithium cyclic 1,2-tetrafluoroethanedisulfonylimide, 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 ( Fluorine-containing organic lithium salts such as 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, and lithium bis (oxalate).} Use in combination with a dicarboxylic acid complex lithium salt such as borate, lithium tris (oxalat) phosphate, lithium difluorooxalat borate, lithium tri (oxalat) phosphate, lithium difluorobis (oxalat) phosphate, lithium tetrafluoro (oxalat) phosphate, etc. In this case, the ratio of the inorganic lithium salt to the total 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 or less, preferably 95% by mass or less. ..

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 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. Further, 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 further preferably 1.6 mol / L or less. When the concentration of the lithium salt is within the above range, the electric conductivity of the non-aqueous electrolyte solution becomes sufficient, and the electric conductivity decreases due to the increase in viscosity. Suppresses deterioration of the performance of the next battery.

[1-4. Non-aqueous solvent]
As the non-aqueous solvent contained in the non-aqueous electrolyte solution of the present invention, a solvent of a conventionally known non-aqueous electrolyte solution can be appropriately selected and used.
Examples of commonly used non-aqueous solvents include cyclic carbonates, chain carbonates, chain and cyclic carboxylic acid esters, chain and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, aromatic fluorine-containing solvents and the like. Can be mentioned.

Examples of the cyclic carbonate include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, and the cyclic carbonate usually has 3 or more and 6 or less carbon atoms. Among these, ethylene carbonate and propylene carbonate are preferable because they have a high dielectric constant, so that the electrolyte is easily dissolved, and the cycle characteristics are good when a non-aqueous electrolyte secondary battery is used. The present invention is characterized in that it has been found that when the compound of the formula (1) is present when ethylene carbonate and propylene carbonate are used in combination at a specific ratio, the characteristics of the solvent as described above can be maximized. Further, the above-mentioned fluorinated cyclic carbonate can also be used as a solvent. Examples of the cyclic carbonate substituted with fluorine include fluoroethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, tetrafluoroethylene carbonate, and 1-fluoro-2. Fluorine such as −methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate Examples thereof include cyclic carbonates having 3 to 5 carbon atoms substituted with, and among these, fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and trifluoromethylethylene carbonate are preferable.

Examples of the chain carbonate include chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate. The number of carbon atoms is preferably 1 or more and 5 or less, and particularly preferably 1 or more and 4 or less. Of these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable from the viewpoint of improving battery characteristics. In addition, chain carbonates in which a part of hydrogen of the alkyl group is replaced with fluorine can also be mentioned. Chain carbonates substituted with fluorine include bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) carbonate, bis (2-fluoroethyl) carbonate, and bis (2,2-difluoroethyl). Examples thereof include carbonate, bis (2,2,2-trifluoroethyl) carbonate, 2-fluoroethylmethyl carbonate, 2,2-difluoroethylmethyl carbonate, 2,2,2-trifluoroethylmethyl carbonate and the like.

Examples of the chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and propionic acid. Chains in which isopropyl, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, ethyl pivalate, etc. and some of the hydrogens of these compounds are replaced with fluorine. State carboxylic acid ester can be mentioned. Examples of the chain carboxylic acid ester substituted with fluorine include methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetic acid. Among these, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, methyl pentanoate, methyl isobutyrate, ethyl isobutyrate, and methyl pivalate are batteries. It is preferable from the viewpoint of improving the characteristics.
Examples of the cyclic carboxylic acid ester include γ-butyrolactone, γ-valerolactone, and the like, and cyclic carboxylic acid esters in which a part of hydrogen of these compounds is replaced with fluorine. Of these, γ-butyrolactone is more preferable.

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

Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran and the like, and cyclic ether in which a part of hydrogen of these compounds is replaced with fluorine.

Examples of the phosphorus-containing organic solvent include trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, and triethyl phosphite. Examples thereof include triphenyl phosphite, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide and the like, and phosphorus-containing organic solvents in which a part of hydrogen of these compounds is replaced with fluorine. Examples of the phosphorus-containing organic solvent substituted with fluorine include tris phosphate (2,2,2-trifluoroethyl) and tris phosphate (2,2,3,3,3-pentafluoropropyl).

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

Among the above non-aqueous solvents, in the present invention, both ethylene carbonate and propylene carbonate, which are cyclic carbonates, are used, but the combined use of these and chain carbonates provides high conductivity and low viscosity of the electrolytic solution. It is preferable from the viewpoint of compatibility.

In the present invention, one invention is that it contains both ethylene carbonate and propylene carbonate, and 0 <X / Y <1.5 when the volume% of ethylene carbonate is X and the volume % of propylene carbonate is Y. Is. X / Y is preferably 0.05 <X / Y <1.0, more preferably 0.1 <X / Y <0.8, and even more preferably 0.15 <X / Y <. It is 0.6, and particularly preferably 0.2 <X / Y <0.5. This is because gas generation can be effectively suppressed by using a solvent that satisfies such a value. Further, X + Y is preferably 10 <X + Y <40, more preferably 12 <X + Y <38, and most preferably 15 <X + Y <35. This is because, in such a range, the conductivity of the electrolytic solution is high and the viscosity can be kept low.

One type of non-aqueous solvent may be used alone, or two or more types may be used in any combination and ratio. When two or more kinds are used in combination, for example, when a cyclic carbonate and a chain carbonate are used in combination, the preferable content of the chain carbonate in the non-aqueous solvent is usually 20% by volume or more, preferably 40% by volume or more. Further, it is usually 95% by volume or less, preferably 90% by volume or less. On the other hand, the preferable 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 ratio of the chain carbonate is in the above range, the increase in the viscosity of the non-aqueous electrolyte solution is suppressed, and the decrease in the electrical conductivity of the non-aqueous electrolyte solution due to the decrease in the dissociation degree of the lithium salt which is the electrolyte is suppressed. However, the fluoroethylene carbonate may be used as a solvent or an additive, and in that case, the content is not limited to the above.

In this specification, the volume of the non-aqueous solvent is a measured value at 25 ° C., but for a solid at 25 ° C. such as ethylene carbonate, the measured value at the melting point is used.

[1-5. Other additives]
The non-aqueous electrolyte solution of the present invention may contain various additives as long as the effects of the present invention are not significantly impaired. As the additive, conventionally known additives can be arbitrarily used. As the additive, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

(Cyclic carbonate compound with unsaturated bond)
Examples of the cyclic carbonate compound having an unsaturated bond include vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, 1,2-dimethylvinylene carbonate, 1,2-diethylvinylene carbonate, fluorovinylene carbonate, trifluoromethylvinylene carbonate and the like. Vinylene carbonate compounds; vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, 1-n-propyl-2-vinylethylene carbonate, 1-methyl-2-vinylethylene Vinyl ethylene carbonate compounds such as carbonate, 1,1-divinylethylene carbonate, 1,2-divinylethylene carbonate; 1,1-dimethyl-2-methyleneethylene carbonate, 1,1-diethyl-2-methyleneethylene carbonate and the like. Methyleneethylene carbonate compounds and the like can be mentioned. These may be used alone or in combination of two or more.

When a cyclic carbonate compound having an unsaturated bond is contained, the content in the non-aqueous electrolyte solution is usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.3% by mass or more. Yes, usually 10% by mass or less, preferably 8% by mass or less, more preferably 6% by mass or less. When the content of the cyclic carbonate compound having a carbon-carbon unsaturated bond is within the above range, the effect of improving the cycle characteristics of the battery and the capacity maintenance characteristics after high temperature storage is sufficiently exhibited, and at the time of high temperature storage. Suppresses the increase in the amount of gas generated.

(Overcharge inhibitor)
Specific examples of the overcharge inhibitor include alkylbiphenyls such as 2-methylbiphenyl and 2-ethylbiphenyl, terphenyl, and partially hydrides of terphenyl, cyclopentylbenzene, cis-1-propyl-4-phenylcyclohexane, and 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, Aromatic compounds such as triphenyl phosphate, tritril phosphate, tri (t-butylphenyl) phosphate, methylphenyl carbonate, diphenyl carbonate; 2-fluorobiphenyl, 3-fluorobiphenyl, 4-fluorobiphenyl, 4,4'-difluoro Partial fluorides of aromatic compounds such as biphenyl, 2,4-difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole , Fluorine-containing anisole compounds such as 3,5-difluoroanisole and the like.

The content of these overcharge inhibitors in the non-aqueous electrolyte 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. It is 5% by mass or less, usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the concentration is in the above range, the desired effect of the overcharge inhibitor is likely to be exhibited, and deterioration of battery characteristics such as high temperature storage characteristics is suppressed. By containing an overcharge inhibitor in the non-aqueous electrolyte solution, it is possible to suppress the explosion and ignition of the non-aqueous electrolyte secondary battery due to overcharging, and the safety of the non-aqueous electrolyte secondary battery is improved. preferable.

Other auxiliaries include carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate, methoxyethyl-ethyl carbonate, ethoxyethyl-methyl carbonate, ethoxyethyl-ethyl carbonate; dimethyl succinate. , Diethyl succinate, diallyl succinate, dimethyl maleate, diethyl maleate, diallyl maleate, dipropyl maleate, dibutyl maleate, bis maleate (trifluoromethyl), bis maleate (pentafluoroethyl), 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- Spiro compounds such as tetraoxaspiro [5.5] undecane; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and Nitrogen-containing compounds such as N-methylsucciimide; hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane, methylcyclohexane, ethylcyclohexane, propylcyclohexane, n-butylcyclohexane, t-butylcyclohexane, dicyclohexyl; methyl Dimethylphosphinate, ethyldimethylphosphinate, ethyldiethylphosphinate, trimethylphosphonoformate, triethylphosphonoformate, trimethylphosphonoacetate, triethylphosphonoacetate, trimethyl-3-phosphonopropionate, triethyl-3-3 Phosnopropionate and other phosphorus-containing compounds, isocyanatomethane, isocyanatoetane, 1-isocyanatopropane, 1-isocyanatobutane, 1-isocyanatopentane, 1-isocyanatohexane, 1-isocyanatoheptane, 1 -Isocyanatooctane, 1-Isocyanatononan, 1-Isocyanatodecane, Isocyanatocyclohexane,
Methoxycarbonyl isocyanate, ethoxycarbonyl isocyanate, propoxycarbonyl isocyanate, butoxycarbonyl isocyanate, methoxysulfonyl isocyanate, ethoxysulfonyl isocyanate, propoxysulfonyl isocyanate, butoxysulfonyl isocyanate, fluorosulfonyl isocyanate,
1,4-Diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanatooctane, 1,9-di Isocyanatononan, 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-octamethylene diisocyanate, 1,3,5-triisocyanatemethyl Benzene, 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-isocyanatohexa-1-yl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2,4,4-trimethylhexamethylenediisocyanate, 2 , 2,4-trimethylhexamethylene diisocyanate, 4- (isocyanatomethyl) octamethylene = diisocyanate and other isocyanato compounds, lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, monofluorophosphorus Monofluorophosphates such as tetramethylammonium acid, tetraethylammonium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, tetramethylammonium difluorophosphate, tetraethylammonium difluorophosphate, and difluorophosphate. Salt is mentioned. Among these, isocyanato compounds such as 1,6-diisocyanatohexane and 1,3-bis (isocyanatomethyl) cyclohexane and lithium difluorophosphate are preferable from the viewpoint of improving battery characteristics after high temperature storage. These may be used in combination of 2 or more types.

The content of these auxiliaries 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. It is usually 8% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less. It is preferable to add these auxiliaries from the viewpoint of improving the capacity retention characteristics and cycle characteristics after high temperature storage. When this concentration is in the above range, the effect of the auxiliary agent is likely to be exhibited, and deterioration of battery characteristics such as high load discharge characteristics is suppressed.

[4-2. 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 occlude and release lithium ions. Specific examples include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like. One of these may be used alone, or two or more thereof may be arbitrarily combined and used in combination.

<Negative electrode active material>
Examples of the negative electrode active material include carbonaceous materials, alloy-based materials, lithium-containing metal composite oxide materials, and the like.

Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. ..

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

As the device used for the spheroidizing process, for example, a device that repeatedly applies mechanical actions such as compression, friction, and shear force, including the interaction of particles mainly with impact force, to the particles can be used. Specifically, it has a rotor with a large number of blades installed inside the casing, and by rotating the rotor at high speed, mechanical actions such as impact compression, friction, and shearing force are applied to the carbon material introduced inside. , And a device that performs the spheroidizing process is preferable. Further, it is preferable that the carbon material has a mechanism for repeatedly giving a mechanical action by circulating the carbon material.

For example, in the case of sphericalizing using the above-mentioned device, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and 50 to 100 m / sec. It is more preferable to do so. Further, although the treatment can be carried out simply by passing a carbonaceous material, it is preferable to circulate or retain in the apparatus for 30 seconds or more, and to circulate or retain in the apparatus for 1 minute or more. More preferred.

(2) As artificial graphite, coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, etc. Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene silfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin are usually used in the range of 2500 ° C or higher and usually 3200 ° C or lower. Examples thereof include those produced by graphitization at temperature, crushing and / or classifying as necessary. At this time, a silicon-containing compound, a boron-containing compound, or the like can also be used as a graphitization catalyst. In addition, artificial graphite obtained by graphitizing mesocarbon microbeads separated in a pitch heat treatment process can be mentioned. Further, artificial graphite of granulated particles composed of primary particles can also be mentioned. For example, by mixing mesocarbon microbeads, graphitizable carbon material powder such as coke with graphitizable binder such as tar and pitch, and graphitizing catalyst, graphitizing and pulverizing if necessary. Examples thereof include graphite particles obtained by assembling or bonding a plurality of flat particles so that the orientation planes are non-parallel.

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

(4) The carbon-coated graphite can be obtained by mixing natural graphite and / or artificial graphite with a carbon precursor which is an organic compound such as tar, pitch or resin, and heat-treating it once or more in the range of 400 to 2300 ° C. Examples thereof include a carbon graphite composite in which natural graphite and / or artificial graphite is used as nuclear graphite and amorphous carbon is coated on the nuclear graphite. The form of the composite may be a coating of the entire surface or a part thereof, or a composite of a plurality of primary particles using carbon derived from the carbon precursor as a binder. Carbon can also be deposited (CVD) on the surface of graphite by reacting natural graphite and / or artificial graphite with hydrocarbon gases such as benzene, toluene, methane, propane, and aromatic volatiles at high temperatures. A graphite composite can also be obtained.

(5) As the graphite-coated graphite, natural graphite and / or artificial graphite is mixed with a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin, and once in the range of about 2400 to 3200 ° C. Examples thereof include graphite-coated graphite in which natural graphite and / or artificial graphite obtained by the above heat treatment is used as nuclear graphite, and graphite is coated on the entire or a part of the surface of the nuclear graphite.

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

Further, as the carbonaceous materials (1) to (6), one type may be used alone, or two or more types may be used in combination in any combination and ratio.

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

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

As an alloy-based material used as a negative electrode active material, if lithium can be occluded and released, lithium alone, a single metal and alloy forming a lithium alloy, or their oxides, carbides, nitrides, silicides, and sulfides. It may be either a substance or a compound such as a phosphate, and is not particularly limited. The elemental metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / semi-metal elements (that is, excluding carbon), and more preferably elemental metals of aluminum, silicon and tin, and elemental metals of aluminum, silicon and tin. An alloy or compound containing these atoms. One of these may be used alone, or two or more thereof may be used in any combination and ratio.

<Physical characteristics of carbonaceous materials>
When a carbonaceous material is used as the negative electrode active material, it is desirable that the material has the following physical properties.

(X-ray parameter)
The d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction of a carbonaceous material is usually 0.335 nm or more, and usually 0.360 nm or less, 0.350 nm. The following is 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 size of the carbonaceous material is the volume-based average particle size (median diameter) determined by the laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and 7 μm. The above is particularly preferable, and usually 100 μm or less, 50 μm or less is preferable, 40 μm or less is more preferable, 30 μm or less is further preferable, and 25 μm or less is particularly preferable.

If the volume-based average particle size falls below the above range, the irreversible capacity may increase, resulting in a loss of initial battery capacity. On the other hand, if it exceeds the above range, a non-uniform coating surface is likely to occur when the electrode is produced by coating, which may not be desirable in the battery manufacturing process.

The volume-based average particle size is measured by laser diffraction / scattering particle size distribution in which carbon powder is dispersed in a 0.2 mass% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant. This is performed using a meter (for example, LA-700 manufactured by HORIBA, Ltd.). The median diameter obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

(Raman R value)
The Raman R value of the carbonaceous material is a value measured by the laser Raman spectral 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.

If the Raman R value is less than the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li enters between layers may decrease due to charging and discharging. That is, the charge acceptability may decrease. Further, when the negative electrode is densified by pressing after being applied to the current collector, the crystals are likely to be oriented in the direction parallel to the electrode plate, which may lead to deterioration of the load characteristics.

On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte solution is increased, and the efficiency may be lowered and the gas generation may be increased.

For the measurement of the Raman spectrum, a Raman spectroscope (for example, a Raman spectroscope manufactured by Nippon Spectrometer Co., Ltd.) is used to naturally drop the sample into the measurement cell and fill it, and the surface of the sample in the cell is filled with argon ion laser light (or semiconductor). This is performed by rotating the cell in a plane perpendicular to the laser beam while irradiating the cell with 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) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention.

The Raman measurement conditions described above 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 more preferably less, ^{10 m} 2 · ^{g -1} or less are especially preferred.

If the value of the BET specific surface area is less than this range, the acceptability of lithium tends to deteriorate during charging when used as a negative electrode material, and lithium tends to precipitate on the electrode surface, which may reduce stability. On the other hand, if it exceeds this range, the reactivity with the non-aqueous electrolyte solution increases when used as the negative electrode material, gas generation tends to increase, and it may be difficult to obtain a preferable battery.

To measure the specific surface area by the BET method, a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken) is used to pre-dry the sample at 350 ° C. for 15 minutes under nitrogen flow, and then to atmospheric pressure. Using a nitrogen helium mixed gas accurately adjusted so that the relative pressure value of nitrogen is 0.3, the nitrogen adsorption BET 1-point method by the gas flow method is used.

(Circularity)
When the circularity is measured as the degree of sphere of the carbonaceous material, it is preferably within the following range. The circularity is defined by "circularity = (perimeter of a corresponding circle having the same area as the particle projection shape) / (actual circumference of the particle projection shape)", and is theoretical when the circularity is 1. Become a true sphere.

The circularity of the particles in which the particle size of the carbonaceous material is in the range of 3 to 40 μm is preferably as close to 1 as it is, preferably 0.1 or more, particularly 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 particularly preferable. The high current density charge / discharge characteristics improve as the circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between the particles is increased, and the high current density charge / discharge characteristics for a short time may be lowered.

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

The method for improving the circularity is not particularly limited, but a sphere-shaped one is preferable because the shape of the interparticle voids when the electrode body is formed is adjusted. Examples of the spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, and a mechanical / physical treatment method of granulating a plurality of fine particles by a binder or the adhesive force of the particles themselves. 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. It is particularly preferable, 2 g · cm ^-3 or less is preferable, 1.8 g · cm ^-3 or less is further preferable, and 1.6 g · cm ^-3 or less is particularly preferable. If the tap density is lower than the above range, the filling density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds the above range, the voids between the particles in the electrode become too small, it becomes difficult to secure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

To measure the tap density, pass through a sieve with a mesh size of 300 μm, ^{drop the sample into a tapping cell of 20 cm 3} to fill the sample up to the upper end surface of the cell, and then use a powder density measuring device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser), tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample.

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

The orientation ratio is measured by X-ray diffraction after pressure molding the sample. A molded product obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm ^{and compressing it with 58.8 MN · m-2} was set using clay so as to be flush with the surface of the sample holder for measurement. Measure X-ray diffraction. From the peak intensities of (110) diffraction and (004) diffraction of the obtained carbon, the ratio expressed by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated.
The X-ray diffraction measurement conditions are as follows. In addition, "2θ" indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degrees Light receiving slit = 0.15 mm
Scattering slit = 0.5 degrees ・ Measurement range and step angle / measurement time:
(110) Surface: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree / 60 seconds (004) Surface: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree / 60 seconds

(Aspect ratio (powder))
The aspect ratio of the carbonaceous material is usually 1 or more, usually 10 or less, preferably 8 or less, and even more preferably 5 or less. If the aspect ratio exceeds the above range, streaks or a uniform coated surface cannot be obtained at the time of electrode plate formation, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.

The aspect ratio is measured by magnifying and observing the particles of the carbonaceous material with a scanning electron microscope. Arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted for each of them, and the carbonaceous material particles are observed three-dimensionally. The longest diameter A and the shortest diameter B orthogonal to the diameter A are measured, and the average value of A / B is obtained.

<Construction and manufacturing method of negative electrode>
Any known method can be used for producing the electrode as long as the effect of the present invention is 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 a negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed to form a slurry. Can be done.

When an alloy-based material is used, a method of forming a thin film layer (negative electrode active material layer) containing the above-mentioned negative electrode active material by a method such as a vapor deposition method, a sputtering method, or a plating method is also used.

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

[4-3. Positive electrode]
<Positive electrode active material>
The positive electrode active material (lithium transition metal compound) used for the positive electrode will be described below.

<Lithium transition metal compound>
The lithium transition metal compound is a compound having a structure capable of desorbing and inserting Li ions, and examples thereof include sulfides, phosphate compounds, and lithium transition metal composite oxides. As the sulfide, a compound having a two-dimensional layered structure such as _{TiS 2} or MoS _{2 or a strong substance represented by the general formula Me x} Mo ₆ S ₈ (Me is various transition metals including Pb, Ag, Cu). Examples thereof include a sulphide compound having a three-dimensional skeletal structure. Examples of the phosphate compound include those belonging to the olivine structure, which are generally represented by LiMePO ₄ (Me is at least one transition metal), and specifically, LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , Examples thereof include _{LiMnPO 4.} Examples of the lithium transition metal composite oxide include those belonging to a spinel structure capable of three-dimensional diffusion and a layered structure capable of two-dimensional diffusion of lithium ions. 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 , LiCo MnO ₄ , LiNi _0.5 Mn _1.5 O. ₄ , LiCoVO _{4 and the} like can be mentioned. Those having a layered structure are generally represented as LiMeO ₂ (Me is at least one transition metal). 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, such as LiMnO ₂ and the like.

(composition)
Further, the lithium-containing transition metal compound may be, for example, a lithium transition metal compound represented by the 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. The rich portion of Li represented by x may be replaced with 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 there may be some non-stoichiometric ratio. Further, x in the above composition formula is a charged composition at the production stage of the lithium transition metal compound. Batteries on the market are usually aged after the batteries are assembled. Therefore, the amount of Li in the positive electrode may be missing due to charging and discharging. In that case, in composition analysis, x when discharged to 3 V may be measured to be −0.65 or more and 1 or less.

Further, the lithium transition metal-based compound is excellent in battery characteristics when it is fired by performing high-temperature firing in an oxygen-containing gas atmosphere in order to enhance the crystallinity of the positive electrode active material.

Further, the lithium transition metal compound represented by the composition formula (A) may be a solid solution with _{Li 2} MO _{3 called a 213 layer as shown in the general formula (A') below.}
αLi ₂ MO ₃・ (1-α) LiM'O ₂ ... (A')

In the general formula, α is a number satisfying 0 <α <1.
M is at least one metallic element average oxidation number of 4 ^+, specifically, at least one metal element Mn, Zr, Ti, Ru, selected from the group consisting of Re and Pt.

M 'is at least one metallic element average oxidation number of 3 ^+, preferably, V, Mn, Fe, at least one metallic element selected from the group consisting of Co and Ni, more preferably , Mn, Co and Ni, at least one metal element selected from the group.

2) In the case of a lithium transition metal compound represented by the following general formula (B) Li [Li _a M _b Mn _2-ba ] 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.
When the value of b is in this range, the energy density per unit weight of the lithium transition metal compound is high.

Further, the value of a is usually 0 or more and 0.3 or less. Further, a in the above composition formula is a charged composition at the production stage of the lithium transition metal compound. Batteries on the market are usually aged after the batteries are assembled. Therefore, the amount of Li in the positive electrode may be missing due to charging and discharging. In that case, in composition analysis, a when discharged to 3 V may be measured to be −0.65 or more and 1 or less.

When the value of a is in this range, the energy density per unit weight of the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.

Further, the value of δ is usually in the range of ± 0.5.
When 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 by using this lithium transition metal compound are good.

Here, the chemical meaning of the lithium composition in the lithium nickel-manganese-based composite oxide, which is the composition of the lithium transition metal-based compound, will be described in more detail below.

To determine the composition formulas a and b of the lithium transition metal compound, each transition metal and lithium are analyzed by an inductively coupled plasma emission spectrophotometer (ICP-AES) to determine the ratio of Li / Ni / Mn. It is calculated by.

From a structural point of view, it is considered that the lithium related to a is replaced with the same transition metal site. Here, due to the lithium related to a, the average valence of M and manganese becomes larger than 3.5 valence due to the principle of charge neutrality.

Further, the 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 having the above composition include, 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 Examples _{include Ni 0.5} O _{4 and the} like. These lithium transition metal compounds may be used alone or in combination of two or more.

(Introduction of different elements)
Further, a foreign element may be introduced into the lithium transition metal compound. Different elements include 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, Pb, Sb, Si and Sn. These different elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a simple substance or a compound on the particle surface or grain boundaries thereof. It may be unevenly distributed.

<Construction and manufacturing method of positive electrode for lithium secondary battery>
The positive electrode for a lithium secondary battery is formed by forming a positive electrode active material layer containing the above-mentioned lithium transition metal compound powder for a positive electrode material for a lithium secondary battery and a binder on a current collector.
As the positive electrode active material layer, a positive electrode material, a binder, a conductive material and a thickener, which are usually used as needed, and the like are mixed in a dry manner to form a sheet, which is then pressure-bonded 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 the material of the positive electrode current collector, a metal material such as aluminum, stainless steel, nickel plating, titanium, or tantalum, or a carbon material such as carbon cloth or carbon paper is usually used. As for the shape, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon column. And so on. The thin film may be formed in a mesh shape as appropriate.

When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but it is usually preferably in the range of 1 μm or more and 100 mm or less. If it 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 in the production of 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 in the production of the electrode may be used. Resin-based 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 polymer such as propylene rubber, styrene-butadiene-styrene block copolymer and its hydrogen additive, EPDM (ethylene-propylene-diene ternary copolymer), styrene-ethylene-butadiene-ethylene copolymer, Thermoplastic elastomeric polymers such as styrene / isoprene styrene block copolymer and its hydrogenated additives, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin Soft resinous polymers such as polymers, fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, and alkali metal ions (particularly lithium ions) Examples thereof include a polymer composition having ionic conductivity. In addition, as these substances, 1 type may be used alone, and 2 or more types may be used together in arbitrary combinations and ratios.

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

The positive electrode active material layer usually contains a conductive material in order to increase conductivity. The type is not particularly limited, but specific examples include metallic materials such as copper and nickel, graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. Carbon material and the like can be mentioned. In addition, as these substances, 1 type may be used alone, and 2 or more types may be used together in arbitrary combinations and ratios. The ratio 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 conversely, if it is too high, the battery capacity may decrease.

As the liquid medium for forming the slurry, a lithium transition metal compound powder as a positive electrode material, a binder, and a conductive material and a thickener used as needed can be dissolved or dispersed. The type of solvent is not particularly limited, and either an aqueous solvent or an organic solvent may be used. Examples of aqueous solvents include water and alcohol, and examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N. , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a latex such as SBR is used to make a slurry. As these solvents, one type may be used alone, or two or more types may be used in any combination and ratio.

The content ratio of the lithium transition metal 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. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if 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 electrode density of the positive electrode after pressing is usually 2.2 g / cm ³ or more and 4.2 g / cm ³ or less.

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

[4-4. Separator]
A separator is usually interposed between the positive electrode and the negative electrode to prevent a short circuit. In this case, the non-aqueous electrolyte solution 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 separator can be used as long as the effects of the present invention are not significantly impaired. Among them, resins, glass fibers, inorganic substances and the like formed of a material stable to the non-aqueous electrolyte solution of the present invention are used, and a porous sheet or a non-woven fabric-like material having excellent liquid retention property is used. Is preferable.

As the material of the resin and the glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyether sulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferable, and polyolefins are more preferable. 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, further preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, further preferably 30 μm or less. If the separator is too thin than the above range, the insulating property and mechanical strength may decrease. Further, if it is too thick than the above range, not only the battery performance such as rate characteristics may be deteriorated, but also the energy density of the non-aqueous electrolyte secondary battery as a whole may be lowered.

Further, when a porous material such as a porous sheet or a non-woven fabric is used as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, still more preferably 45% or more. Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too small than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. On the other hand, if it is larger than the above range, the mechanical strength of the separator tends to decrease, and the insulating property tends to decrease.

The average pore size of the separator is also arbitrary, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore diameter exceeds the above range, a short circuit is likely to occur. Further, if it falls below the above range, 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 a fiber shape are used. Used.

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

The characteristics of the separator in the non-electrolyte liquid secondary battery can be grasped by the galley value. The gullet value indicates the difficulty of passing air in the film thickness direction, and is represented by the number of seconds required for 100 ml of air to pass through the film. Therefore, the smaller the value, the easier it is to pass through, and the larger the value. It means that it is harder 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 poor the communication in the thickness direction of the film. The communication property is the degree of connection of holes in the film thickness direction. If the galley value of the separator of the present invention is low, it can be used for various purposes. For example, when used as a separator for a non-aqueous lithium secondary battery, a low galley value means that lithium ions can be easily transferred, which is preferable because the battery performance is excellent. The galley value of the separator is arbitrary, but is preferably 10 to 1000 seconds / 100 ml, more preferably 15 to 800 seconds / 100 ml, and even more preferably 20 to 500 seconds / 100 ml. When the galley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.

[4-5. Battery design]
<Electrode group>
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are formed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are spirally wound through the separator. Either may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. ..

When the electrode group occupancy rate is less than the above range, the battery capacity becomes small. Further, if it exceeds the above range, the void space is small, and the internal pressure rises due to the expansion of the member due to the high temperature of the battery and the increase of the vapor pressure of the liquid component of the electrolyte, and the charge / discharge repeatability as a battery is repeated. In some cases, various characteristics such as high temperature storage may be deteriorated, and a gas discharge valve that releases internal pressure to the outside may operate.

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

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

<Protective element>
As a protective element, PTC (Positive Temperature Coafficient), which increases resistance when abnormal heat generation or excessive current flows, a thermal fuse, thermistor, and cuts off the current flowing in the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation. A valve (current cutoff valve) or the like can be used. It is preferable to select the protective element under conditions that do not operate under normal use with a high current, and it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually configured by accommodating the above-mentioned non-aqueous electrolyte, negative electrode, positive electrode, separator and the like inside the exterior. The exterior body is not particularly limited, and any known exterior body can be used as long as the effects of the present invention are not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.

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

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

<Preparation of non-aqueous electrolyte solution>
[Examples 1 to 5, Comparative Examples 1 to 3]
Under a dry argon atmosphere, ethylene carbonate (hereinafter EC), propylene carbonate (hereinafter PC), ethyl methyl carbonate (hereinafter EMC) and diethyl carbonate (hereinafter DEC) were added in an amount of 15% by volume, 15% by volume, 40% by volume and 30% by volume, respectively. _{LiPF 6} was dissolved at 1.2 M in a non-aqueous solvent mixed so as to be. To this, 2% by mass of vinylene carbonate (hereinafter referred to as VC) and 1% by mass of adiponitrile were added, and 0.3% by mass of trichloroisocyanurate (2-acryloyloxyethyl) as a compound of the formula (1) was added thereto for non-aqueous electrolysis. The liquid was adjusted.

In Examples 2 to 5 and Comparative Examples 1 to 3, the non-aqueous electrolyte solution having the composition shown in Table 1 below was prepared in the same manner as in Example 1.

<Manufacturing of negative electrode>
To 98 parts by mass of graphite powder as a negative electrode active material, 1 part by mass of an aqueous dispersion of sodium carboxymethyl cellulose and 1 part by mass of an aqueous dispersion of styrene-butadiene rubber were 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 prepare a negative electrode. The prepared negative electrode was dried under reduced pressure at 60 ° C. for 12 hours before use.

<Preparation of positive electrode>
To 96.8 parts by mass of lithium cobalt oxide 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 with a disperser to form a slurry. The obtained slurry was applied to both sides of the aluminum foil, dried and pressed to prepare a positive electrode. The prepared positive electrode was dried under reduced pressure at 80 ° C. for 12 hours before use.

<Battery production>
The above positive electrode, negative electrode, and polyethylene separator were laminated in this order of negative electrode, separator, positive electrode, separator, and negative electrode to prepare a battery element. After inserting this battery element into a bag made of a laminated film in which both sides of aluminum (thickness 40 μm) are coated with a resin layer while projecting the positive and negative electrode terminals, 0.4 mL of non-aqueous electrolyte solution is placed in the bag. It was injected and vacuum-sealed to prepare a sheet-shaped battery. Further, in order to improve the adhesion between the electrodes, a sheet-shaped battery was sandwiched between glass plates and pressurized.

<Characteristic evaluation test>
The battery prepared as described above was charged to 4.35 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. Then, the battery was stored at 60 ° C. for 14 days in a state of being charged to 4.35 V, and the amount of gas generated was measured. The results of the experiment are shown in FIG.

As is clear from FIG. 1, by using the electrolytic solution of the present invention, it is possible to specifically suppress the generation of gas. That is, with respect to Examples 1 to 5 in which the value of X / Y is 0 <X / Y <1.5, Comparative Examples 1 to 1 in which the value of X / Y is not 0 <X / Y <1.5. In No. 3, the amount of gas generated was large even if the compound of the formula (1) was contained. This is done by specifying the value of X / Y, that is, by specifying the amount ratio of ethylene carbonate and propylene carbonate, and by containing the compound of formula (1), EC, PC, and the compound of formula (1). However, it is considered that such an effect was exhibited because the film formed on the electrode surface became the optimum form.

[Examples 2-1 to 2-3, Comparative Example 2-1]
Under a dry argon atmosphere, a non-aqueous electrolyte solution having the composition shown in Table 2 below was prepared.

The method for preparing the electrolytic solution is the same as in Example 1, and the compound of the formula (1) is trisocyanurate (2-acryloyloxyethyl).
Was used.

<Preparation of electrodes and manufacture of batteries>
The preparation of the electrodes and the preparation of the battery are the same as in the first embodiment.

<Characteristic evaluation test>
The battery prepared as described above was charged to 4.35 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. After that, FIG. 2 shows the capacity retention rate when 4.35 V charge and -3 V discharge are set as one cycle and 300 cycles are performed at 45 ° C.

The following can be said from FIG. In Examples 2-1 to 2-3 using the electrolytic solution of the present invention, the cycle capacity retention rate was improved as compared with Comparative Example 2-1. This is because it contains both EC and PC, the value of the ratio X / Y of both is a specific value, and contains the compound of formula (1), so that the compound of EC, PC, and formula (1) is an electrode. It is considered that such an effect was exhibited because the film formed on the surface became the optimum form.

[Examples 3-1 to 2-3, Comparative Example 3-1]
Under a dry argon atmosphere, a non-aqueous electrolyte solution having the composition shown in Table 3 below was prepared.
The method for preparing the electrolytic solution was the same as in Example 1, and trichloroisocyanurate (2-acryloyloxyethyl) was used as the compound of the formula (1).

Compound A is 1,3-bis (isocyanatomethyl) cyclohexane.

<Preparation of electrodes and manufacture of batteries>
The preparation of the electrodes and the preparation of the battery are the same as in the first embodiment.

<Characteristic evaluation test>
The battery prepared as described above was charged to 4.35 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. After that, the capacity retention rate when 4.35 V charge-3 V discharge is set as one cycle and 100 cycles are performed at 25 ° C. is shown in FIG.

The following can be said from FIG. In Examples 3-1 to 3-2 using the electrolytic solution of the present invention, the cycle capacity retention rate was improved as compared with Comparative Example 3-1. This is because it contains both EC and PC, the value of the ratio X / Y of both is a specific value, and contains the compound of formula (1), so that the compound of EC, PC, and formula (1) is an electrode. It is considered that such an effect was exhibited because the film formed on the surface became the optimum form.

[Example 4-1 and Comparative Examples 4-1 to 4-3]
_{Under a dry argon atmosphere, LiPF 6} was dissolved at 1.2 M in a non-aqueous solvent in which EC, EMC and DEC were mixed so as to be 30% by volume, 40% by volume and 30% by volume, respectively. A non-aqueous electrolyte solution was prepared by adding 2% by mass of VC and 1% by mass of adiponitrile. This is designated as the reference electrolytic solution 4.

In Example 4-1 based on the reference electrolyte 4, 0.3% by mass of trichloroisocyanurate (2-acryloyloxyethyl) and 3% by mass of PS (1,3-propanesulton) were used as the compounds of the formula (1). The added electrolyte was used. In Comparative Example 4-1 the reference electrolytic solution 4 was used as it was. In Comparative Example 4-2, an electrolytic solution obtained by adding 0.3% by mass of trichloroisocyanurate (2-acryloyloxyethyl) to the reference electrolytic solution 4 was used. In Comparative Example 4-3, an electrolytic solution obtained by adding 3% by mass of PS (1,3-propane sultone) to the reference electrolytic solution 4 was used.

<Preparation of electrodes and manufacture of batteries>
The preparation of the electrodes and the preparation of the battery are the same as in the first embodiment.

<Characteristic evaluation test>
The battery prepared as described above was charged to 4.35 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. Then, a storage test was carried out at 60 ° C. for 14 days in a state of being charged at 4.35 V. The capacity residual rate at this time (capacity after storage test / capacity before storage test × 100) was measured.

As a result of the test, the volume residual ratio of Comparative Example 4-1 (using the reference electrolyte 4) was 83.12%, whereas that of Comparative Example 4-2 (using only the compound of the formula (1)) A decrease in the capacity residual rate was observed at 82.51%. On the other hand, the volume residual rate of Comparative Example 4-3 (using only PS) was 85.16%, whereas that of Example 4-1 (using the compound of formula (1) and PS) was 85. An improvement in the capacity remaining rate was observed at 29%. This is because when the X / Y value does not fall within the scope of the present invention, good results cannot be obtained only with the compound of formula (1), but the characteristics can be improved by combining with a specific compound such as PS. It shows that. This is because even if the X / Y value does not fall within the scope of the present invention, the optimum form is a film formed on the electrode surface by combining the compound of formula (1) with a specific compound such as PS. Therefore, it is considered that such an effect was exhibited.

As described above, by using the compound of the formula (1) under specific conditions as in the present invention, a specific effect that could not be assumed by the knowledge so far is exhibited, and a cycle is exhibited. It is possible to obtain an electrolytic solution having excellent characteristics, gas suppression, and high temperature characteristics, and a battery using the same.

<Preparation of non-aqueous electrolyte solution>
[Example 5-1 and Comparative Examples 5-1 to 5-2]
_{In a dry argon atmosphere, LiPF 6} is 1.2 M with respect to a non-aqueous solvent in which EC, PC, EMC and DEC are mixed so as to be 5% by volume, 25% by volume, 40% by volume and 30% by volume, respectively. Was dissolved in. To this, 2% by mass of VC and 2% by mass of FEC were added, and 0.5% by mass of trichloroisocyanurate (2-acryloyloxyethyl) as a compound of the formula (1) was added thereto, and the non-aqueous system of Example 5-1 was added. The electrolyte was adjusted.
_{In Comparative Example 5-1, LiPF 6} was added to a non-aqueous solvent in which EC, PC, EMC, and DEC were mixed so as to be 30% by volume, 0% by volume, 40% by volume, and 30% by volume, respectively, under a dry argon atmosphere. Was dissolved to 1.2 M. A non-aqueous electrolyte solution was prepared by adding 2% by mass of VC and 2% by mass of FEC.
_{In Comparative Example 5-2, LiPF 6} was added to a non-aqueous solvent in which EC, PC, EMC, and DEC were mixed so as to be 5% by volume, 25% by volume, 40% by volume, and 30% by volume, respectively, under a dry argon atmosphere. Was dissolved to 1.2 M. A non-aqueous electrolyte solution was prepared by adding 2% by mass of VC and 2% by mass of FEC.

<Preparation of electrodes and manufacture of batteries>
The preparation of the electrodes and the preparation of the battery are the same as in the first embodiment.

<Characteristic evaluation test>
The battery prepared as described above was charged to 4.4 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. Then, a continuous charging test was carried out at 60 ° C. for 14 days in a state of being charged at 4.4 V. The continuous charge test is a test for continuing low-voltage charging of 4.4 V. The amount of gas generated at this time was measured.

As a result of the test, the gas generation amount of Comparative Example 5-1 was 3.92 mL, whereas that of Comparative Example 5-2 was 4.14 mL, which was an increase in the gas generation amount. On the other hand, in Example 5-1, a decrease in gas generation amount of 3.16 mL was observed. This is because even if the value of X / Y falls within the range of the present invention, good results cannot be obtained when the compound of the formula (1) is not used, but the value of X / Y falls within the range of the present invention. However, it can be said that this is a specific effect when the compound of the formula (1) is used.

<Preparation of non-aqueous electrolyte solution>
[Example 6-1 and Comparative Example 6-1]
_{In a dry argon atmosphere, LiPF 6} is 1.2 M with respect to a non-aqueous solvent in which EC, PC, EMC and DEC are mixed so as to be 5% by volume, 25% by volume, 40% by volume and 30% by volume, respectively. Was dissolved in. The non-aqueous electrolyte solution of Example 6-1 was prepared by adding 2% by mass of VC and 1% by mass of trichloroisocyanurate (2-acryloyloxyethyl) as the compound of the formula (1).
_{In Comparative Example 6-1, LiPF 6} was added to a non-aqueous solvent in which EC, PC, EMC, and DEC were mixed so as to be 5% by volume, 25% by volume, 40% by volume, and 30% by volume, respectively, under a dry argon atmosphere. Was dissolved to 1.2 M. 2% by mass of VC was added thereto to prepare a non-aqueous electrolyte solution.

<Preparation of electrodes and manufacture of batteries>
The preparation of the electrodes and the preparation of the battery are the same as in the first embodiment.

<Characteristic evaluation test>
The battery prepared as described above was charged to 4.4 V at 25 ° C., discharged to 3 V, and conditioned until the capacity became stable. Then, a cycle test was carried out in which 4.4 V charge and 3 V discharge were repeated 700 times at 45 ° C., and the cycle capacity retention rate (%) at this time was determined.

As a result of the test, the cycle capacity retention rate was 54.5% in Comparative Example 6-1 and the cycle capacity retention rate was 57.9% in Example 6-1, showing an improvement effect.

From these experimental results, it was possible to obtain a battery having excellent characteristics such as suppression of gas generation and low resistance by using the non-aqueous electrolyte solution of the present invention.

According to the non-aqueous electrolyte solution of the present invention, decomposition of the electrolyte solution of the non-aqueous electrolyte secondary battery is suppressed, gas generation and deterioration of the battery are suppressed when the battery is used in a high temperature environment, and high energy density is suppressed. Non-aqueous electrolyte secondary battery can be manufactured. Therefore, it can be suitably used in various fields such as electronic devices in which a non-aqueous electrolyte secondary battery is used.

The application of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and it can be used in various known applications. Specific examples include laptops, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copies, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini disks, transceivers. , Electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, bikes, motorized bicycles, bicycles, lighting equipment, toys, game machines, watches, power tools, strobes, cameras, large households A storage battery and the like can be mentioned.

Claims (10)

A non-aqueous electrolyte solution having a positive electrode having a positive electrode active material capable of storing and releasing metal ions and a negative electrode having a negative electrode active material capable of storing and releasing metal ions A non-aqueous electrolyte solution used in a secondary battery. ,
The following formula:

It contains trisocyanurate (2-acryloyloxyethyl) represented by, and the content of trisocyanurate (2-acryloyloxyethyl) is 0.01% by mass or more and 1% by mass or less with respect to the total amount of the non-aqueous electrolyte solution. And
The non-aqueous solvent contains both ethylene carbonate and propylene carbonate, and when the volume% of ethylene carbonate is X and the volume% of propylene carbonate is Y, 0 <X / Y <1.5 and 15 <X + Y <. A non-aqueous electrolyte solution characterized by being 35. The non-aqueous electrolyte solution according to claim 1, wherein 0.1 <X / Y <1.0. A non-aqueous electrolyte solution according to claim 1 or 2, wherein 0.15 <X / Y <0.6. A non-aqueous electrolytic solution further containing at least one of a fluorinated cyclic carbonate, a cyclic compound having an S = O bond, or a nitrile compound according to any one of claims 1 to 3. A non-aqueous electrolyte solution having a positive electrode having a positive electrode active material capable of storing and releasing metal ions and a negative electrode having a negative electrode active material capable of storing and releasing metal ions A non-aqueous electrolyte solution used in a secondary battery. ,
The following formula:

It contains trisocyanurate (2-acryloyloxyethyl) represented by, and the content of trisocyanurate (2-acryloyloxyethyl) is 0.01% by mass or more and 1% by mass or less with respect to the total amount of the non-aqueous electrolyte solution. And
A non-aqueous electrolyte solution further containing a cyclic compound having an S = O bond. The fluorinated cyclic carbonate according to claim 4 is a fluoroethylene carbonate, and the cyclic compound having an S = O bond is among 1,3-propanesulton, 1,4-butansulton, 1,3-propensulton, and ethylene sulfate. A non-aqueous electrolyte solution, which is at least one kind, and the nitrile compound is at least one kind out of butyronitrile, lauronitrile, crotononitrile, succinonitrile, adiponitrile, pimeronitrile, and sebaconitrile. The non-cyclic compound having an S = O bond according to claim 5 is at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propensultone, and ethylene sulfate. Aqueous electrolyte. The non-aqueous electrolyte solution according to any one of claims 1 to 7 , further containing a chain carbonate which is at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. The non-aqueous electrolyte solution according to any one of claims 1 to 8 , wherein the cyclic carbonate compound having an unsaturated bond is contained in the non-aqueous electrolyte solution in an amount of 0.1% by mass or more and 8% by mass or less. A non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material capable of storing and releasing metal ions and a negative electrode having a negative electrode active material capable of storing and releasing metal ions.
A non-aqueous electrolyte secondary battery according to any one of claims 1 to 9 , wherein the non-aqueous electrolyte solution is used.

Images