JP2008204923A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery containing above nonaqueous electrolyte - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide nonaqueous electrolyte with electrode expansion restrained and having excellent charge/discharge cycle life, and a nonaqueous electrolyte secondary battery. <P>SOLUTION: The nonaqueous electrolyte contains a compound (A) expressed in a formula given. In the formula, X is hydrogen, a halogen, an isocyanate group, a hydrocarbon group which may contain a hetero element, a halogenated hydrocarbon group, and a base compound itself of the compound (A). Y is a substituent selected from an oxy group, a carbonyl group, an oxycarbonyl group, a carbonate group, a sulfide group, a sulfonyl group, a sulfite group, a phosphate group, a boric acid ester group, an amide group, or the like, m is 0 or 1, n is an integer from 0 to 5, and R1, R2 express hydrogen, a hydrocarbon group, or a fluoroalkyl group, at least either being a fluoroalkyl group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery that includes the non-aqueous electrolyte and is used mainly as a power source for portable electronic devices such as video cameras, mobile computers, and mobile phones.

A battery containing a non-aqueous electrolyte is widely used as a power source for consumer electronic devices because it has a high voltage, a high energy density, and high reliability such as storage stability.
As a typical example of a battery containing a nonaqueous electrolyte, a lithium battery and a lithium ion secondary battery can be given. These batteries include a negative electrode made of metal lithium or an active material capable of occluding and releasing lithium, a positive electrode made of transition metal oxide, fluorinated graphite, a composite oxide of lithium and transition metal, and the like. A water electrolyte.
The non-aqueous electrolyte is LiBF ₄ , LiPF ₆ , LiClO ₄ , LiA in an aprotic organic solvent.
It is a solution obtained by mixing a Li electrolyte such as sF ₆ , LiCF ₃ SO ₃ , Li ₂ SiF ₆ or the like.

In the nonaqueous electrolyte secondary battery, the nonaqueous electrolyte transfers ions between the positive electrode and the negative electrode. In order to improve the charge / discharge characteristics of the battery, it is necessary to increase the ion transfer speed between the positive electrode and the negative electrode as much as possible, increase the ionic conductivity of the electrolyte, decrease the viscosity of the electrolyte, It is necessary to facilitate mass transfer due to diffusion. In addition, the non-aqueous electrolyte needs to be stable with respect to the positive electrode and the negative electrode that are chemically and electrochemically reactive in order to improve the storage stability of the battery and the cycle stability when charging and discharging are repeated. is there.
As an electrolyte satisfying such requirements, Non-Patent Document 1 includes a high dielectric constant carbonate solvent such as propylene carbonate and ethylene carbonate, a low viscosity carbonate solvent such as diethyl carbonate, methyl ethyl carbonate, and dimethyl carbonate, and lithium such as LiPF _6. The salt dissolved is shown.

With the increase in energy density of non-aqueous electrolyte secondary batteries, the amount of electrolyte contained in the battery becomes relatively small. Therefore, even if the electrolyte as described above is used, it is chemically and electrochemically used. There was a problem that the stability with respect to the electrode having high reactivity was insufficient, and the storage stability of the battery and the charge / discharge cycle characteristics such as the charge / discharge cycle life characteristics became insufficient.
In order to improve these performances, an additive having a function of stabilizing the electrode surface is added to the nonaqueous electrolyte. As such additives, carbonate compounds having a carbon-carbon unsaturated bond such as vinylene carbonate, and sulfate compounds such as 1,3-propane sultone, ethylene sulfite, and ethylene sulfate are disclosed in Patent Documents 1 to 3. .
Jean Paul, edited by Gabano “Lithium Battery”, ACADEMIC PRESS, 1983 Japanese Patent Application Laid-Open No. 08-045545 JP 2002-329528 A JP-A-10-189042

  However, with the recent increase in energy density of non-aqueous electrolyte secondary batteries, there has been a problem that even if the additive is contained in the non-aqueous electrolyte, the storage stability and charge / discharge cycle characteristics of the battery are insufficient. It was. In particular, when charging / discharging is repeated at a low temperature or at a normal temperature, the battery thickness increases, the battery mounting property to the electronic device used deteriorates, or the capacity retention rate of the charging / discharging cycle decreases, that is, charging / discharging. There was a problem that the cycle life was shortened.

  The present invention has been made in view of such circumstances, and even when the non-aqueous electrolyte secondary battery is produced by containing the compound (A) of the following chemical formula 1, even if the battery has a high energy density, An object of the present invention is to provide a non-aqueous electrolyte in which swelling of an electrode when charging / discharging is repeated at low temperature and normal temperature is suppressed and charge / discharge cycle life characteristics are good.

  Further, in the present invention, when the non-aqueous electrolyte secondary battery is produced by containing 0.001% by mass to 5% by mass of the compound (A) with respect to the total mass, charging and discharging are performed at a low temperature and a normal temperature. An object of the present invention is to provide a nonaqueous electrolyte in which the swelling of the electrode when the above is repeated is further suppressed, and the charge / discharge cycle life characteristics are further improved.

  And this invention is charging / discharging at normal temperature, when a nonaqueous electrolyte secondary battery is produced by further containing the carbonic acid ester compound (B) which has a carbon-carbon unsaturated bond in addition to the said compound (A). An object of the present invention is to provide a nonaqueous electrolyte in which the swelling of the electrode when the above is repeated is further suppressed, and the charge / discharge cycle life characteristics are further improved.

  Furthermore, in the present invention, when a nonaqueous electrolyte secondary battery was produced by further containing a sulfate ester compound (C) in addition to the compound (A), charging and discharging were repeated at room temperature. An object of the present invention is to provide a non-aqueous electrolyte in which the swelling of the electrode is further suppressed and the charge / discharge cycle life characteristics are further improved.

  In addition, since the present invention contains any of the above non-aqueous electrolytes, the battery has good storage stability and charge / discharge cycle characteristics, in particular, good charge / discharge cycle life characteristics at low temperatures and normal temperatures, and swelling. An object of the present invention is to provide a non-aqueous electrolyte secondary battery that is suppressed from being deteriorated and is less likely to be attached to an electronic device.

As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by using a non-aqueous electrolyte containing the following compound, and has completed the present invention.
That is, the nonaqueous electrolyte according to the first invention is characterized by containing the compound (A) represented by the following chemical formula (1).

(In the formula, X represents hydrogen, a halogen group, an isocyanate group, a hydrocarbon group that may contain a hetero element, and a halogenated hydrocarbon group, and also includes the mother compound itself of the compound (A). , Oxy group, carbonyl group, carbonyloxy group, carbonate group, sulfide group, sulfinyl group, sulfonyl group, sulfonyloxy group, sulfite group, sulfate group, phosphate group, borate group, and amide group It is a substituent selected from the group, m is 0 or 1. n is an integer of 0 to 5. When n is 2 or more, Xs may be the same or different.
Furthermore, R1 and R2 represent hydrogen, a hydrocarbon group, or a fluoroalkyl group, and at least one is a fluoroalkyl group. )

In the present invention, since the compound (A) is added to the non-aqueous electrolyte, when a non-aqueous electrolyte secondary battery is produced using this non-aqueous electrolyte, when charging and discharging are repeated at low and normal temperatures The increase in the electrode thickness is suppressed, the charge / discharge cycle life characteristics are good, and even in a battery with a high energy density, the mounting property to an electronic device is deteriorated or the life of the battery is shortened. It is suppressed.
Although the detailed reason why such an effect is obtained is unknown, since the compound (A) acts on the surface of the electrode, the interface resistance between the electrode and the electrolyte is reduced, and the generation of precipitates in the negative electrode is reduced. It is considered that the capacity retention ratio is improved, the amount of deposits in the negative electrode is reduced, the swelling of the negative electrode plate is reduced, and the increase in battery thickness is suppressed. This effect is first manifested by the addition of compound (A).

  The non-aqueous electrolyte according to the second invention is characterized in that, in the first invention, the compound (A) is contained in an amount of 0.001% by mass to 5% by mass with respect to the total mass.

  In the present invention, since the compound (A) is contained in an amount of 0.001% by mass to 5% by mass with respect to the total mass of the nonaqueous electrolyte, a nonaqueous electrolyte secondary battery is produced using this nonaqueous electrolyte. Further, the effect of suppressing the swelling of the electrode when charging / discharging is repeated at low temperature and normal temperature is better, and the charge / discharge cycle life characteristics are even better.

  The nonaqueous electrolyte according to the third invention is characterized in that, in the first or second invention, the nonaqueous electrolyte further contains a carbonic acid ester compound (B) having a carbon-carbon unsaturated bond.

  In the present invention, the carbonic acid ester compound (B) is added to the nonaqueous electrolyte in addition to the compound (A), and when a nonaqueous electrolyte secondary battery is produced using this nonaqueous electrolyte, When the charging and discharging are repeated, the swelling of the electrode is further suppressed, and the charge / discharge cycle life characteristics are further improved.

  The nonaqueous electrolyte according to the fourth invention is characterized in that in any one of the first to third inventions, the non-aqueous electrolyte further contains a sulfate ester compound (C).

In the present invention, in addition to the compound (A), the sulfate ester compound (C) is added to the non-aqueous electrolyte, and when a non-aqueous electrolyte secondary battery is produced using this non-aqueous electrolyte, at room temperature. When the charge / discharge is repeated, the swelling of the electrode is further suppressed, and the charge / discharge cycle life characteristics are further improved.
In addition, in addition to the compound (A) in addition to the compound (A), when the carbonate ester compound (B) and the sulfate ester compound (C) are added in combination, a nonaqueous electrolyte secondary battery is manufactured using this nonaqueous electrolyte. When produced, the charge / discharge cycle life characteristics at room temperature are further improved.

  A nonaqueous electrolyte secondary battery according to a fifth invention includes the nonaqueous electrolyte according to any one of the first to fourth inventions.

  In the present invention, since the nonaqueous electrolyte according to any one of the first to fourth inventions is included, the storage stability and charge / discharge cycle characteristics of the battery are good, and in particular, the charge / discharge cycle life characteristics at low temperature or normal temperature are good. Yes, swelling is suppressed, and deterioration of the mounting property to the used electronic device is suppressed.

  According to the non-aqueous electrolyte of the present invention, when a non-aqueous electrolyte secondary battery is produced using this non-aqueous electrolyte, an increase in the thickness of the electrode during the charge / discharge cycle at a low temperature and a normal temperature is suppressed, and the charge / discharge cycle A non-aqueous electrolyte secondary battery having good life characteristics can be obtained.

  According to the nonaqueous electrolyte secondary battery of the present invention, the increase in battery thickness is suppressed during the charge / discharge cycle at low temperature and room temperature, and the charge / discharge cycle life characteristics are good.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
The nonaqueous electrolyte secondary battery (hereinafter referred to as a battery) of the present invention has a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte.

(1) Nonaqueous electrolyte The nonaqueous electrolyte which concerns on this invention contains the compound (A) shown by the said Chemical formula 1.
In the compound (A), examples of the hydrocarbon groups of R1 and R2 include alkyl groups such as methyl, ethyl, propyl, butyl, and hexyl groups, and aromatic hydrocarbon groups such as phenyl and tolyl groups. Is done. As the fluoroalkyl group, a trifluoromethyl group, a difluoromethyl group, a fluoromethyl group, a pentafluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, a 2,2,2-trifluoroethyl group, 2, Examples include 2-difluoroethyl group, 2-fluoroethyl group, heptafluoropropyl group and the like.
Among these, from the viewpoint of good expression of the effect of the present invention and chemical stability to the negative electrode, both R1 and R2 are preferably a fluoroalkyl group, and more preferably a trifluoromethyl group.

  From the viewpoint of good expression of the effect of the present invention and solubility of the compound (A) in the electrolyte, n is preferably 0 to 2, and n is more preferably 1.

In the compound (A), X— (Y) _m may include all substituents that can be bonded to the aromatic ring. Specific examples of X include hydrogen, halogen groups (fluorine, chlorine, bromine, iodine), isocyanate groups, hydrocarbon groups that may contain heteroelements, and halogenated hydrocarbon groups. Also, compound (A) The parent compound itself is also included.
Y is a linking group between X and the aromatic ring of the mother compound, and is an oxy group (—O—), a carbonyl group (—C (═O) —), or a carbonyloxy group (—OC (═O) —). , Carbonate group (—OC (═O) O—), sulfide group (—S—), sulfinyl group (—S (═O) —), sulfonyl group (—S (═O) ₂ —), sulfonyloxy group _{(-OS (= O) 2 -} ), sulfurous ester group (-OS (= O) O-) , sulfate group _{(-OS (= O) 2 O-} ), phosphoric acid ester group (-
O (XO) P (═O) O—), a borate group (—O (XO) BO—), and an amide group (—N (X) C (═O) —) A substituent can be mentioned. In the formula, X is the same as X. m is 0 or 1.
Specific examples _{X- (Y) m, HO-,} F-, CH 3 -, CF 3 -, C 6 H 5 -, C 6 H 4
_{F-, CH 3 O-, HOC (} = O) -, CH 3 OC (= O) -, CH 3 C (= O) O-, C
H ₃ OC (═O) O—, HS—, CH ₃ S—, CH ₃ S (═O) —, CH ₃ S (═O) ₂ —,
CH ₃ S (═O) ₂ O—, CH ₃ OS (═O) ₂ —, CH ₃ OS (═O) ₂ O—, (CH ₃ O) ₂ P (═O) O—, (CH ₃ O ) ₂ BO—, (CH ₃ ) ₂ NC (═O) —, CH ₃ C (═O) N
(CH ₃ ) —, (HO) C (CF ₃ ) ₂ C ₆ H ₅ —. Also exemplified are those in which CH ₃ (methyl group) exemplified above is replaced with trifluoromethyl group, ethyl group, vinyl group, propargyl group, phenyl group or (HO) C (CF ₃ ) ₂ C ₆ H ₅ —. Is done.
Among the exemplified substituents, the compound (A) is preferably a compound (A) that has a good effect on the positive electrode from the viewpoint of good expression of the effect of the present invention, and carbon carbon such as alkyloxy group, alkenyl group, and alkynyl group. An electron donating group such as a hydrocarbon group having an unsaturated bond is preferable, not only suppressing the increase in electrode thickness when charging and discharging are repeated at low and normal temperatures, but also increasing the thickness of electrodes when charging and discharging are repeated at high temperatures. Since it contributes also to suppression of carbon, it is more preferably a hydrocarbon group having a carbon-carbon unsaturated bond such as vinyl group, propenyl group, ethynyl group, propargyl group or allyl group, and particularly preferably a vinyl group.

  The compound (A) is specifically exemplified below. In addition, the compound 14, the compound 15, the compound 21, and the compound 22 are illustrations of the structure where X is the mother compound itself of the compound (A). Compound 14 corresponds to a structure in which X is the mother compound itself of compound A and m = 0, and compound 15 corresponds to a structure in which X is the mother compound itself of compound A and Y is an oxy group. 21 corresponds to a structure in which X is the mother compound itself of compound A and Y is a sulfonyl group, and compound 22 corresponds to a structure in which X is the mother compound itself of compound A and Y is a carbonate group.

  Among the compounds exemplified above, from the viewpoint that the effects of the present invention are well expressed and from the viewpoint of cost, compounds 1, 9, 10, and 11 are preferable, compounds 1 and 11 are more preferable, and compound 11 is particularly preferable. preferable.

The content of the compound (A) in the nonaqueous electrolyte is preferably 0.001% by mass or more and 5% by mass or less. Furthermore, it is preferable that it is 0.002 mass% or more and 3 mass% or less.
When the addition amount exceeds 5% by mass, the capacity retention rate of the charge / discharge cycle test at low temperature and normal temperature becomes small.
When the addition amount is less than 0.001% by mass, the effects of the present invention may not be achieved.
The conventional additive tends to exhibit the effect most effectively at an addition amount of about 1% by mass, but the compound (A) used in the present invention has a very small addition amount compared to the conventional additive. From the standpoint that the effect is exhibited and better performance is exhibited, the addition amount is particularly preferably 0.005% by mass or more and 0.5% by mass or less.

The nonaqueous electrolyte according to the present invention preferably contains a carbonate ester compound (B) having a carbon-carbon unsaturated bond.
By including the carbonate ester compound (B) in the non-aqueous electrolyte, there is an effect of increasing the stability of the electrolyte, particularly in the negative electrode. However, in the non-aqueous electrolyte secondary battery with an increased energy density, during the charge / discharge cycle at a low temperature There was a problem that the thickness of the electrode increased.
However, when used in combination with the compound (A) of the present invention, the increase in the thickness of the electrode is greatly suppressed, the capacity retention rate of the charge / discharge cycle at low temperature is improved, and the stability of the electrolyte in the negative electrode and the thickness of the electrode are improved. A non-aqueous electrolyte excellent in charge / discharge cycle characteristics from a low temperature to a normal temperature can be obtained, which is compatible with increase suppression.

Examples of the carbonate compound (B) having at least one carbon-carbon unsaturated bond include vinylene carbonate, dimethyl vinylene carbonate, vinyl ethylene carbonate, divinyl ethylene carbonate and the like. These compounds may be added alone or in combination of two or more.
Of these, carbonate compounds having a carbon-carbon unsaturated bond in the ring such as vinylene carbonate and dimethyl vinylene carbonate are preferred.
The content of the carbonate ester compound (B) is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass with respect to the total mass of the nonaqueous electrolyte.

The non-aqueous electrolyte according to the present invention preferably further contains a sulfate ester compound (C). By containing the sulfate ester compound (C) in the non-aqueous electrolyte, there is an effect of increasing the stability of the non-aqueous electrolyte particularly in the positive electrode. However, in the non-aqueous electrolyte secondary battery having an increased energy density, charging / discharging at normal temperature is performed. There was a problem that the thickness of the electrode during the cycle was increased.
However, by using the compound (A) used in the present invention in combination, the increase in the thickness of the electrode is greatly suppressed, the capacity retention rate of the charge / discharge cycle at low temperature is improved, and the stability of the electrolyte in the positive electrode and the electrode Thus, a nonaqueous electrolyte excellent in cycle charge / discharge characteristics from low temperature to room temperature can be obtained.

As the sulfate ester compound (C), 1,3-propane sultone, 1,4-butane sultone, 1,3-prop-1-ene sultone, 1-methyl-1,3-prop-1-ene sultone, ethylene sulfite, sulfurous acid Examples include propylene, ethylene sulfate, propylene sulfate, butene sulfate, hexene sulfate, vinylene sulfate, 3-sulfolene, divinyl sulfone, dimethyl sulfate, and diethyl sulfate. These compounds may be added alone or in combination of two or more. Of these, 1,3-prop-1-ene sultone, ethylene sulfate, propylene sulfate, butene sulfate, and hexene sulfate are preferable.
The content of the sulfate ester compound (C) is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass with respect to the total mass of the nonaqueous electrolyte.

The nonaqueous solvent used in the nonaqueous electrolyte of the present invention preferably contains at least a cyclic aprotic solvent and / or a chain aprotic solvent.
Examples of the cyclic aprotic solvent include cyclic carbonates such as ethylene carbonate, cyclic esters such as γ-butyrolactone, cyclic sulfones such as sulfolane, and cyclic ethers such as dioxolane.
Examples of the chain aprotic solvent include chain carbonates such as dimethyl carbonate, chain carboxylic acid esters such as methyl propionate, and chain ethers such as dimethoxyethane.

In particular, when the load characteristics and low temperature characteristics of the battery are intended to be improved, the non-aqueous solvent is preferably a mixture of a cyclic aprotic solvent and a chain aprotic solvent. Furthermore, when importance is attached to the electrochemical stability of the electrolyte, it is preferable to use a cyclic carbonate as the cyclic aprotic solvent and a chain carbonate as the chain aprotic solvent.
Specific examples of cyclic carbonates include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, trans Examples include -2,3-pentylene carbonate, cis-2,3-pentylene carbonate, trifluoromethylethylene carbonate, fluoroethylene carbonate, 4,5-difluoroethylene carbonate.
Of these, ethylene carbonate and propylene carbonate having a high dielectric constant are preferable. When graphite is used for the negative electrode active material, it is more preferable to use ethylene carbonate. Moreover, you may use these cyclic carbonates in mixture of 2 or more types.

  Specific examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, and methyl trifluoroethyl carbonate. Can be mentioned. Of these, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate having low viscosity are preferable. These chain carbonates may be used in combination of two or more.

  The mixing ratio of the cyclic carbonate and the chain carbonate is such that the cyclic carbonate: chain carbonate (volume ratio) is preferably 1:99 to 80:20, more preferably 5:95 to 70:30, particularly Preferably it is 10: 90-60: 40. By setting such a ratio, an increase in the viscosity of the electrolyte can be suppressed and the degree of dissociation of the electrolyte can be increased, so that the conductivity of the electrolyte contributing to the charge / discharge characteristics of the battery can be increased.

  In the non-aqueous electrolyte according to the present invention, other compounds than the above may be contained in the non-aqueous solvent as long as the object of the present invention is not hindered. Specific examples of the other compounds include dimethylformamide and the like. Amides, chain carbamates such as methyl-N, N-dimethylcarbamate, cyclic amides such as N-methylpyrrolidone, cyclic ureas such as N, N-dimethylimidazolidinone, trimethylborate, triethylborate , Borate esters such as tributyl borate, trioctyl borate, tri (trimethylsilyl) borate, phosphate esters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tri (trimethylsilyl) phosphate , Ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, polyethylene group Carbon-carbon unsaturated bonds such as ethylene glycol derivatives such as coal dimethyl ether, aromatic hydrocarbons such as biphenyl, fluorobiphenyl, o-terphenyl, toluene, ethylbenzene and fluorobenzene, and maleic anhydride and norbornene dicarboxylic acid anhydride. The carboxylic anhydride which has can be mentioned. Of these, when a carboxylic acid anhydride having a carbon-carbon unsaturated bond is included, the stability of the electrolyte in the negative electrode is further enhanced, and an increase in the thickness of the electrode is greatly suppressed, which is desirable.

As the lithium salt used in the non-aqueous electrolyte of the present invention, any lithium salt that is used as a normal non-aqueous electrolyte can be used.
Specific examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF _6.
, Li ₂ SiF ₆ , LiOSO ₂ C _k F _{(2k + 1)} (k = 1 to 8), LiN (SO ₂ C _{k
F (2k + 1)) 2} (k = 1~8 _{integer), LiPF n (C k F} (2k + 1)) (6-n) (n = 1~5,
k = 1 to 8), LiBF _n (C _k F _{(2k + 1)} (n = 1 to 3, k = 1 to 8), L
iB (C ₂ O ₂ ) ₂ (lithium bisoxalyl borate), LiBF ₂ (C ₂ O ₂ ) (lithium difluorooxalyl borate), LiPF ₃ (C ₂ O ₂ ) (lithium trifluorooxalyl phosphate) Is mentioned. As the lithium salt used in the non-aqueous electrolyte of the present invention, any lithium salt that is used as a normal non-aqueous electrolyte can be used.
Moreover, the lithium salt shown by the following general formula can also be used.
LiC (SO ₂ R ¹¹ ) (SO ₂ R ¹² ) (SO ₂ R ¹³ )
LiN (SO ₂ OR ¹⁴ ) (SO ₂ OR ¹⁵ )
LiN (SO ₂ R ¹⁶ ) (SO ₂ OR ¹⁷ )
(In formula, R < ¹¹ > -R < ¹⁷ > may mutually be same or different, and is a C1-C8 perfluoroalkyl group).
These lithium salts may be used alone or in combination of two or more.
Of these, LiPF ₆ , LiBF ₄ , and LiN (SO ₂ C _k F _{(2k + 1)} ) ₂ (k = 1 to 8) are particularly preferable.

  The above electrolyte is preferably contained in the nonaqueous electrolyte at a concentration of 0.1 to 3 mol / liter, more preferably 0.5 to 2 mol / liter.

(2) Positive electrode As the positive electrode active material used in the battery of the present invention, a composition formula Li _x MO ₂ , Li _y M ₂ O ₄ (where M is selected from transition metals), which is a compound capable of inserting and extracting lithium. Or a composite oxide represented by 0 ≦ x ≦ 1, 0 ≦ y ≦ 2), a metal chalcogenide or a metal oxide having a tunnel structure and a layered structure can be used. Specific examples thereof include LiCoO ₂ , LiCo _x Ni _1-x O ₂ , LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ , MnO ₂ , FeO ₂ , V _{2.
O 5, V 6 O 13,} TiO 2, TiS 2 and the like.
Examples of the organic compound include conductive polymers such as polyaniline.
Furthermore, regardless of an inorganic compound or an organic compound, the above various active materials may be mixed and used.
When a granular positive electrode active material is used, the positive electrode is produced, for example, by forming a mixture of positive electrode active material particles, a conductive additive and a binder on a metal current collector such as aluminum. .

(3) Negative electrode As the negative electrode active material of the present invention, all generally known materials such as metallic lithium, lithium alloys, and carbon materials capable of occluding and releasing lithium can be used. Examples of the negative electrode active material include Al, Si, Pb, Sn, Zn, Cd and lithium alloys, LiFe ₂ O ₃ ,
Metal oxides such as WO ₂ , MoO ₂ , SiO, and CuO, carbonaceous materials such as graphite and carbon, lithium nitride such as Li ₃ N, or lithium metal, or a mixture thereof can be used.

(4) Separator As the separator of the present invention, a woven fabric, a nonwoven fabric, a synthetic resin microporous membrane, or the like can be used, and a synthetic resin microporous membrane can be suitably used. Among these, a microporous membrane made of polyethylene and polypropylene, or a polyolefin microporous membrane such as a microporous membrane composed of these is preferably used in terms of thickness, membrane strength, membrane resistance, and the like.
Moreover, it can also serve as a separator by using solid electrolytes, such as a polymer solid electrolyte.
Further, a synthetic resin microporous membrane and a polymer solid electrolyte may be used in combination. In this case, a porous polymer solid electrolyte membrane may be used as the polymer solid electrolyte, and the polymer solid electrolyte may further contain an electrolytic solution.

The shape of the battery of the present invention is not particularly limited, and can be applied to non-aqueous electrolyte secondary batteries having various shapes such as a square, a long cylinder, a coin, a button, a sheet, and a cylindrical battery. Although it is possible, the effect is satisfactorily exhibited in a battery in which the battery case is easily deformed, such as a square, long cylindrical, coin, button, and sheet.

  Hereinafter, the present invention will be described with reference to preferred embodiments. However, the present invention is not limited to the embodiments in any way, and can be implemented with appropriate modifications within a range not changing the gist thereof. .

(Example 1)
FIG. 1 is a cross-sectional view showing a nonaqueous electrolyte secondary battery according to the present invention. In FIG. 1, 1 is a rectangular nonaqueous electrolyte secondary battery (hereinafter referred to as a battery), 2 is an electrode group, 3 is a negative electrode, 4 is a positive electrode, 5 is a separator, 6 is a battery case, 7 is a battery lid, 8 Is a safety valve, 9 is a negative electrode terminal, and 10 is a negative electrode lead. The electrode group 2 is obtained by winding the negative electrode 3 and the positive electrode 4 in a flat shape with the separator 5 interposed therebetween. The electrode group 2 and the electrolyte are housed in a battery case 6, and the opening of the battery case 6 is sealed by laser welding a battery lid 7 provided with a safety valve 8. The negative electrode terminal 9 is connected to the negative electrode 3 through the negative electrode lead 10, and the positive electrode 4 is connected to the inner surface of the battery case 6.

The positive electrode 4 was produced as follows.
90% by mass of LiCoO ₂ as a positive electrode active material, 5% by mass of acetylene black as a conductive additive, and 5% by mass of polyvinylidene fluoride (PVDF) as a binder are mixed to form a positive electrode mixture. A paste was obtained by dispersing in N-methyl-2-pyrrolidone. This paste was uniformly applied to an aluminum current collector with a thickness of 20 μm and dried, and then compression molding was performed with a roll press to obtain the positive electrode 4.

The negative electrode 3 was produced as follows.
A slurry was prepared by mixing 97% by mass of graphite as a negative electrode active material, 1.5% by mass of carboxymethyl cellulose and 1.5% by mass of styrene butadiene rubber as a binder, and adding and dispersing distilled water as appropriate. . This slurry was uniformly applied to a 15 μm thick copper current collector, dried, dried at 100 ° C. for 5 hours, and then the density of the negative electrode active material layer composed of the binder and the active material was 1.40 g / cm ³ . Thus, the negative electrode 3 was obtained by compression molding with a roll press.

As the separator, a microporous polyethylene film having a thickness of 20 μm was used. As an electrolyte, 1.1 mol / L of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate in a volume ratio of 3: 3: 3, and the total mass of the electrolyte was further increased. On the other hand, a compound added with 0.001% by mass of the compound 1 represented by the chemical formula 2 was used. The design capacity of the battery is 800 mAh.

(Example 2)
A battery was fabricated in the same manner as in Example 1 except that 0.002% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 3)
A battery was fabricated in the same manner as in Example 1 except that 0.005 mass% of Compound 1 was added to the total mass of the electrolyte.
Example 4
A battery was fabricated in the same manner as in Example 1 except that 0.01% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 5)
A battery was fabricated in the same manner as in Example 1 except that 0.02% by mass of Compound 1 was added to the total mass of the electrolyte.

(Example 6)
A battery was fabricated in the same manner as in Example 1 except that 0.05% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 7)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 8)
A battery was fabricated in the same manner as in Example 1 except that 0.2% by mass of Compound 1 was added to the total mass of the electrolyte.
Example 9
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 10)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of Compound 1 was added to the total mass of the electrolyte.

(Example 11)
A battery was prepared in the same manner as in Example 1 except that 2% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 12)
A battery was prepared in the same manner as in Example 1 except that 3% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 13)
A battery was fabricated in the same manner as in Example 1 except that 5% by mass of Compound 1 was added to the total mass of the electrolyte.
(Example 14)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 2 was added to the total mass of the electrolyte.
(Example 15)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 7 was added to the total mass of the electrolyte.

(Example 16)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 8 was added to the total mass of the electrolyte.
(Example 17)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 9 was added based on the total mass of the electrolyte.
(Example 18)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 10 was added based on the total mass of the electrolyte.
(Example 19)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 11 was added based on the total mass of the electrolyte.
(Example 20)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 14 was added to the total mass of the electrolyte.

(Example 21)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of vinylene carbonate (VC) were added to the total mass of the electrolyte.
(Example 22)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of vinylethylenelene carbonate (VEC) were added to the total mass of the electrolyte.
(Example 23)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of divinylethylene carbonate (DVEC) were added to the total mass of the electrolyte.
(Example 24)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of dimethyl vinylene carbonate (DMVC) were added to the total mass of the electrolyte.
(Example 25)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of 1,3-prop-1-ene sultone (PRS) were added to the total mass of the electrolyte.

(Example 26)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of 1,3-propane sultone (PS) were added to the total mass of the electrolyte.
(Example 27)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of ethylene sulfate (GLST) were added to the total mass of the electrolyte.
(Example 28)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1 and 1% by mass of propylene sulfate (PGLST) were added to the total mass of the electrolyte.
(Example 29)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VC, and 0.5% by mass of VEC were added to the total mass of the electrolyte.
(Example 30)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VC, and 0.5% by mass of DVEC were added to the total mass of the electrolyte.

(Example 31)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VC, and 0.5% by mass of DMVC were added to the total mass of the electrolyte.
(Example 32)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VC, and 0.5% by mass of PRS were added to the total mass of the electrolyte.
(Example 33)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VC, and 0.5% by mass of PS were added to the total mass of the electrolyte.
(Example 34)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VC, and 0.5% by mass of GLST were added to the total mass of the electrolyte.
(Example 35)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VC, and 0.5% by mass of PGLST were added to the total mass of the electrolyte.

(Example 36)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VEC, and 0.5% by mass of DVEC were added to the total mass of the electrolyte.
(Example 37)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VEC, and 0.5% by mass of DMVC were added to the total mass of the electrolyte.
(Example 38)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VEC, and 0.5% by mass of PRS were added to the total mass of the electrolyte.
(Example 39)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VEC, and 0.5% by mass of PS were added to the total mass of the electrolyte.
(Example 40)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VEC, and 0.5% by mass of GLST were added to the total mass of the electrolyte.

(Example 41)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of VEC, and 0.5% by mass of PGLST were added to the total mass of the electrolyte.
(Example 42)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DVEC, and 0.5% by mass of DMVC were added to the total mass of the electrolyte.
(Example 43)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DVEC, and 0.5% by mass of PRS were added to the total mass of the electrolyte.
(Example 44)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DVEC, and 0.5% by mass of PS were added to the total mass of the electrolyte.
(Example 45)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DVEC, and 0.5% by mass of GLST were added to the total mass of the electrolyte.

(Example 46)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DVEC, and 0.5% by mass of PGLST were added to the total mass of the electrolyte.
(Example 47)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DMVC, and 0.5% by mass of PRS were added to the total mass of the electrolyte.
(Example 48)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DMVC, and 0.5% by mass of PS were added to the total mass of the electrolyte.
(Example 49)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DMVC, and 0.5% by mass of GLST were added to the total mass of the electrolyte.
(Example 50)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of DMVC, and 0.5% by mass of PGLST were added to the total mass of the electrolyte.

(Example 51)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of PRS, and 0.5% by mass of PS were added to the total mass of the electrolyte.
(Example 52)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of PRS, and 0.5% by mass of GLST were added to the total mass of the electrolyte.
(Example 53)
A battery was fabricated in the same manner as in Example 1 except that 0.1% by mass of Compound 1, 0.5% by mass of PRS, and 0.5% by mass of PGLST were added to the total mass of the electrolyte.

(Comparative Example 1)
A battery was fabricated in the same manner as in Example 1 except that no additive was added to the electrolyte.
(Comparative Example 2)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of VC was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.
(Comparative Example 3)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of VEC was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.
(Comparative Example 4)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of DVEC was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.
(Comparative Example 5)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of DMVC was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.

(Comparative Example 6)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of PRS was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.
(Comparative Example 7)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of PS was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.
(Comparative Example 8)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of GLST was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.
(Comparative Example 9)
A battery was fabricated in the same manner as in Example 1 except that 1% by mass of PGLST was added to the total mass of the electrolyte without adding the compound (A) to the electrolyte.
(Comparative Example 10)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of VC and 0.5% by mass of VEC were added to the electrolyte without adding the compound (A) to the electrolyte. .

(Comparative Example 11)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of VC and 0.5% by mass of DVEC were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 12)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of VC and 0.5% by mass of DMVC were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 13)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of VC and 0.5% by mass of PRS were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 14)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of VC and 0.5% by mass of PS were added to the total mass of the electrolyte. .
(Comparative Example 15)
Without adding the compound (A) to the electrolyte, VC is 0.5% by mass with respect to the total mass of the electrolyte, GL
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of ST was added.

(Comparative Example 16)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of VC and 0.5% by mass of PGLST were added to the total mass of the electrolyte. .
(Comparative Example 17)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of VEC and 0.5% by mass of DVEC were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 18)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, 0.5% by mass of VEC and 0.5% by mass of DMVC were added to the total mass of the electrolyte. .
(Comparative Example 19)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of VEC and 0.5% by mass of PRS were added to the total mass of the electrolyte. .
(Comparative Example 20)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of VEC and 0.5% by mass of PS were added to the total mass of the electrolyte. .

(Comparative Example 21)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of VEC and 0.5% by mass of GLST were added to the total mass of the electrolyte. .
(Comparative Example 22)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of VEC and 0.5% by mass of PGLST were added to the total mass of the electrolyte. .
(Comparative Example 23)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by weight of DVEC and 0.5% by weight of DMVC were added to the total weight of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 24)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of DVEC and 0.5% by mass of PRS were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 25)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of DVEC and 0.5% by mass of PS were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .

(Comparative Example 26)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of DVEC and 0.5% by mass of GLST were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 27)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of DVEC and 0.5% by mass of PGLST were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 28)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of DMVC and 0.5% by mass of PRS were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .
(Comparative Example 29)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of DMVC and 0.5% by mass of PS were added to the total mass of the electrolyte. .
(Comparative Example 30)
A battery was fabricated in the same manner as in Example 1 except that 0.5% by mass of DMVC and 0.5% by mass of GLST were added to the total mass of the electrolyte without adding the compound (A) to the electrolyte. .

(Comparative Example 31)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5% by mass of DMVC and 0.5% by mass of PGLST were added to the total mass of the electrolyte. .
(Comparative Example 32)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5 mass% of PRS and 0.5 mass% of PS were added to the total mass of the electrolyte. .
(Comparative Example 33)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5 mass% of PRS and 0.5 mass% of GLST were added to the total mass of the electrolyte. .
(Comparative Example 34)
A battery was fabricated in the same manner as in Example 1 except that the compound (A) was not added to the electrolyte, and 0.5 mass% of PRS and 0.5 mass% of PGLST were added to the total mass of the electrolyte. .

[Initial capacity check test]
The initial capacity (mAh) and the initial battery thickness (mm) were measured for the batteries of the above-described examples and comparative examples. The batteries of each Example and each Comparative Example were prepared in 5 cells, and each battery was charged at a constant current and a constant voltage for 3 hours up to 4.2 V at a current of 800 mA, and then discharged to 3 V at a current of 800 mA. The discharge capacity (initial capacity) and battery thickness (initial battery thickness) were measured, and the average value of 5 cells was determined.

[Low-temperature charge / discharge cycle test]
Moreover, the capacity retention rate (%) of the low-temperature charge / discharge cycle test and the difference in battery thickness before and after the test (battery thickness increment) were measured for each battery.
The low temperature charge / discharge cycle test was performed under the following conditions.
The battery after the initial capacity confirmation test was repeated in a constant temperature bath at -10 ° C. under the same conditions as the measurement of the initial capacity for 50 cycles, and then the battery was left at 25 ° C. for 5 hours to obtain the initial capacity. The discharge capacity was measured under the same conditions as the above, and the capacity retention rate at the 50th cycle with respect to the initial capacity (= measured discharge capacity / initial capacity × 100) was obtained. Further, the battery thickness before and after the test was measured, and the difference in battery thickness before and after the test (battery thickness increment) was also obtained.

[Room temperature charge / discharge cycle test]
The room temperature charge / discharge cycle test was performed under the following conditions.
The battery after the initial capacity confirmation test was repeated 500 cycles of charge / discharge cycles under the same conditions as the measurement of the initial capacity in a constant temperature bath at 25 ° C., and then the capacity retention rate at the 500th cycle relative to the initial capacity (= 500 cycles). The discharge capacity of the eye ÷ initial capacity × 100) was determined. Moreover, the battery thickness before and after the test was measured, and the difference (thickness increment) in the battery thickness before and after the test was also obtained.

  Tables 1-1 to 1-4 below show the results of the initial capacity confirmation test, the low temperature charge / discharge cycle test, and the room temperature charge / discharge cycle test.

In Examples 1-13, the addition amount of the compound 1 with respect to a nonaqueous electrolyte is changed in 0.001-5 mass%.
In Examples 1 to 13 in which Compound 1 was added to the electrolyte in the range of 0.001 to 5 mass%, the capacity retention rate in the low-temperature charge and discharge cycle test was 80 to 91%, and the battery thickness increment was 0.34 to 0.00. Compared with the battery of Comparative Example 1 in which the capacity retention of the normal temperature charge / discharge cycle test is 66 to 87%, the battery thickness increment is 0.40 to 0.51 mm, and no compound 1 is added. The performance has been greatly improved.
And in Examples 2-12 whose addition amount is 0.002-3 mass%, since the capacity | capacitance retention of a normal temperature charging / discharging cycle test is 81% or more, and the thickness increment of a battery is less than 0.50 mm. The addition amount is more preferably 0.002 to 3% by mass. Moreover, it is especially preferable that it is 0.005-0.5 mass% from a viewpoint that an initial stage capacity | capacitance is large.

In Example 7, 14-20, 0.1 mass% of compounds 1, 2, 7, 8, 9, 10, 11 and 14 are added with respect to the nonaqueous electrolyte, respectively.
In Example 14 to which compound 2 was added, the irreversible capacity during initial charge / discharge increased and the initial capacity decreased due to decomposition of compound 2 on the negative electrode. However, compared with the comparative example 1, the increase in battery thickness was suppressed in the low temperature charge / discharge cycle test and the room temperature charge / discharge cycle test, the capacity retention of the low temperature charge / discharge cycle test was improved, and the compound 1 was added. From Example 7, the increase in battery thickness is suppressed in both cycle tests.

Compound 7 and Compound 8 differ in the position of the 2-hydroxy-1,1,1,3,3,3-hexafluoro-2propyl group.
When Examples 15 and 16 to which Compound 7 and Compound 8 were added respectively were compared, the coordinate position of the 2-hydroxy-1,1,1,3,3,3-hexafluoro-2propyl group was 1,4. In Example 15, which is a higher position, the effect of improving the capacity retention rate of the low-temperature charge / discharge cycle test is larger than that of Example 16 coordinated in the first and third positions, and the effect on the room temperature charge / discharge cycle test is unchanged. It was.

Compound 9 has a methyl group, compound 10 has a methoxy group, and compound 11 has a vinyl group. Example 18 to which Compound 10 was added showed the same performance as Example 7 to which Compound 1 was added, and Example 19 to which Compound 11 was added had improved performance over Example 7, in particular vinyl groups. It has been found that the compound 11 is preferable. This is considered to be because the stability of the film formed when the compound 11 having a vinyl group is reduced at the negative electrode.
In Example 17 to which Compound 9 was added, the low-temperature charge / discharge cycle characteristics were slightly better than Example 7. This is considered to be because when the compound 9 is used, the film resistance of the negative electrode is lowered.

Compound 14 has the parent compound itself of Compound 1 as a substituent.
In Example 20 using Compound 14, the capacity retention rate and the battery thickness suppression effect in the room temperature charge / discharge cycle test are slightly improved as compared to Example 7 using Compound 1.

  In Example 21 to Example 53, compound 1 is added as compound (A), and at least one of carbonate ester compound (B) having a carbon-carbon unsaturated bond and sulfate ester compound (C) is added. It is added. In Comparative Examples 2-34, Compound 1 is not added, and at least one of the carbonate ester compound (B) and the sulfate ester compound (C) is added corresponding to each of Examples 21-53.

In Examples 21-24, 29-31, 36, 37, 42, the carbonate ester compound (B) is added to the nonaqueous electrolyte, and in Comparative Examples 2-5, 10-12, 17, 18, 23. Corresponding to each example, the same kind and the same amount of carbonate compound (B) is added.
When the carbonic acid ester compound (B) having a carbon-carbon unsaturated bond is added to the non-aqueous electrolyte,
Since the formed negative electrode film suppresses decomposition of the electrolytic solution, as shown in Comparative Examples 2 to 5, 10 to 12, 17, 18, and 23, the capacity retention rate of the room temperature charge / discharge cycle test is increased, and the battery However, the capacity retention in the low-temperature charge / discharge cycle test is lowered, and the battery thickness is increased. However, as shown in Examples 21 to 24, 29 to 31, 36, 37, and 42, the addition of Compound 1 increases the capacity retention rate of the low-temperature charge / discharge cycle test and decreases the battery thickness.
And when Examples 21-24, 29-31, 36, 37, and 42 are compared with Example 7, in the normal temperature charge / discharge cycle test, the capacity retention rate is all improved, and the swelling of the battery is suppressed. I understand that.

In Examples 25-28 and 51-53, the sulfate ester compound (C) is added to the non-aqueous electrolyte, and in Comparative Examples 6-9 and 32-34, the same kind and the same amount correspond to each Example. The sulfuric ester compound (C) is added.
As shown in Comparative Examples 6 to 9 and 32 to 34, when the sulfate ester compound (C) is added to the nonaqueous electrolyte, the capacity retention rate of the room temperature charge / discharge cycle test is increased, but the battery thickness is increased. Moreover, although there are few adverse effects than the carbonic acid ester compound (B) which has a carbon-carbon unsaturated bond, the capacity retention rate of a low-temperature charging / discharging cycle test becomes low, and battery thickness becomes large.
However, as shown in Examples 25-28 and 51-53, the addition of Compound 1 increases the capacity retention rate of the low-temperature charge / discharge cycle test, after the low-temperature charge / discharge cycle test, and at the room temperature charge / discharge cycle. The swelling of the battery after the test is suppressed.
And when Examples 25-28 and 51-53 are compared with Example 7, in the room temperature charge / discharge cycle test, Example 26 is slightly reduced, but the capacity retention rate of other Examples is improved, It can be seen that all the effects of suppressing the swelling of the battery are larger than those of Example 7.

In Examples 32-35, 38-41, 43-50, the carbonate ester compound (B) and the sulfate ester compound (C) were added in combination to the nonaqueous electrolyte, and Comparative Examples 13-16, 19-22, 24 In 31, the same kind and the same amount of the carbonic acid ester compound (B) and the sulfuric acid ester compound (C) are added corresponding to each Example.
When the carbonate compound (B) and the sulfate ester compound (C) are mixed, the capacity retention rate of the room temperature charge / discharge cycle test is increased due to a synergistic effect, but the capacity retention rate of the low temperature charge / discharge cycle test is remarkably reduced. Further, the swelling of the battery after the low temperature charge / discharge cycle test and after the room temperature charge / discharge cycle test also increases. However, as shown in Examples 32-35, 38-41, 43-50, the addition of Compound 1 improves the capacity retention of the low temperature charge / discharge cycle test, after the low temperature charge / discharge cycle test, and The swelling of the battery after the room temperature charge / discharge cycle test is greatly reduced.
And when Examples 32-35, 38-41, 43-50 and Example 7 are compared, it turns out that the capacity | capacitance retention of a normal temperature charging / discharging cycle test is improving.

It is sectional drawing which shows the nonaqueous electrolyte secondary battery which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte secondary battery 2 Electrode group 3 Negative electrode 4 Positive electrode 5 Separator 6 Battery case 7 Battery cover 8 Safety valve 9 Negative electrode terminal 10 Negative electrode lead

Claims (5)

A nonaqueous electrolyte comprising a compound (A) represented by the following chemical formula 1:

(In the formula, X represents hydrogen, a halogen group, an isocyanate group, a hydrocarbon group that may contain a hetero element, and a halogenated hydrocarbon group, and also includes the mother compound itself of the compound (A). , Oxy group, carbonyl group, carbonyloxy group, carbonate group, sulfide group, sulfinyl group, sulfonyl group, sulfonyloxy group, sulfite group, sulfate group, phosphate group, borate group, and amide group It is a substituent selected from the group, m is 0 or 1. n is an integer of 0 to 5. When n is 2 or more, Xs may be the same or different.
Furthermore, R1 and R2 represent hydrogen, a hydrocarbon group, or a fluoroalkyl group, and at least one is a fluoroalkyl group. )   The nonaqueous electrolyte according to claim 1, wherein the compound (A) is contained in an amount of 0.001% by mass to 5% by mass with respect to the total mass.   The nonaqueous electrolyte according to claim 1 or 2, further comprising a carbonic acid ester compound (B) having a carbon-carbon unsaturated bond.   The nonaqueous electrolyte according to any one of claims 1 to 3, further comprising a sulfate ester compound (C).   A nonaqueous electrolyte secondary battery comprising the nonaqueous electrolyte according to claim 1.

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