JP2003132944A - Nonaqueous system electrolytic solution for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery of nonaqueous system electrolytic solution which is superior in charge and discharge efficiency and storage characteristics even at a high temperature, and nonaqueous system electrolytic solution used in the battery. SOLUTION: The nonaqueous system electrolytic solution in which lithium salt is dissolved in a nonaqueous solvent includes a sulfolane compound. The nonaqueous solvent includes the sulfolane compound wherein at least one hydrogen atom linked with a carbon atom constituting a sulfolane ring is substituted by a fluorine atom. The battery employs the solution.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery using the same. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery having improved charge / discharge efficiency at large currents and excellent charge / discharge efficiency and retention characteristics even at high temperatures, and a non-aqueous electrolyte that provides the same.

[0002]

2. Description of the Related Art With the recent lightening and miniaturization of electric products, development of lithium secondary batteries having a high energy density has been desired more than ever, and the application fields of lithium secondary batteries are expanding. Accordingly, improvement of battery characteristics is also demanded. Currently, LiCoO ₂ , LiMn ₂ O are used for the positive electrode.
₄ , a metal oxide salt such as LiNiO ₂ occludes and absorbs lithium ions such as carbonaceous materials such as coke, artificial graphite and natural graphite, and metal oxide materials such as Sn and Si in the negative electrode. A non-aqueous electrolyte secondary battery using a compound capable of being released has been proposed.

However, in these lithium secondary batteries, it is known that decomposition of the solvent in the electrolytic solution on the surface of the electrode occurs to some extent on the positive electrode and / or the negative electrode. This is a cause of deterioration of discharge efficiency and retention characteristics. Taking a non-aqueous electrolyte secondary battery as a negative electrode by using various graphite-based electrode materials alone or by mixing with other negative electrode materials capable of absorbing and releasing lithium, a lithium primary battery In the case of using an electrolyte solution containing propylene carbonate as a main solvent, which is generally preferred in, the decomposition reaction of the solvent progresses violently on the surface of the graphite electrode, making it impossible to smoothly occlude and release lithium in the graphite electrode. Become.

On the other hand, ethylene carbonate is often used as the main solvent of the electrolytic solution of the non-aqueous electrolytic solution secondary battery because it is less likely to decompose. However, even when ethylene carbonate is used as a main solvent, there is a problem that the charge / discharge efficiency is lowered because the electrolytic solution is decomposed little by little on the electrode surface during the charge / discharge process. Further, there is still a problem in the affinity between the positive electrode material and the negative electrode material and the electrolytic solution, and there is a problem that when the discharge current is increased, the discharge capacity is remarkably reduced as compared with the case where the discharge is performed with a small current. It was

[0005]

DISCLOSURE OF THE INVENTION The present invention aims to minimize the decomposition of the electrolyte solution of a non-aqueous electrolyte secondary battery, to achieve high charge / discharge efficiency, excellent storage characteristics even at high temperatures, and high discharge current. It is an object of the present invention to provide a high energy density non-aqueous electrolyte secondary battery having a large discharge capacity.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that an electrolyte containing a specific sulfolane compound is used as an electrolyte for a non-aqueous electrolyte secondary battery. By using, the affinity between the positive electrode and / or the negative electrode and the electrolytic solution is improved from the initial charging,
Moreover, it was found that a lithium ion-permeable and stable coating is efficiently formed on the surface of the positive electrode and / or the negative electrode, and the excessive decomposition of the electrolytic solution is suppressed, so that the charge / discharge efficiency and the storage characteristic are improved. The present invention has been completed based on the findings.

That is, the gist of the present invention is a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent, wherein the non-aqueous solvent has at least one hydrogen atom bonded to a carbon atom constituting a sulfolane ring. A non-aqueous electrolyte solution for a lithium secondary battery, which contains a sulfolane compound substituted with a fluorine atom (hereinafter referred to as a fluorinated sulfolane compound).

Another aspect of the present invention is metallic lithium,
A negative electrode containing a lithium alloy or a material capable of occluding and releasing lithium, a positive electrode containing a material capable of occluding and releasing lithium, and a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent A lithium secondary battery comprising: a lithium secondary battery, wherein the non-aqueous solvent contains a fluorinated sulfolane compound.
Exist in.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. Examples of the non-aqueous solvent used in the non-aqueous electrolyte solution for a lithium secondary battery of the present invention include cyclic carbonates, chain carbonates, lactone compounds (cyclic esters), chain esters, cyclic ethers, chain ethers. And sulfur-containing organic solvents. Among these, lactone compounds, chain esters, cyclic carbonates, chain carbonates and chain ethers each having 3 to 9 carbon atoms are preferable.

These solvents may be used alone or in combination of two or more. Specific examples of the cyclic carbonate, the lactone compound, the chain carbonate, the carboxylic acid ester and the chain ether each having 3 to 9 carbon atoms include the following. (1) Cyclic carbonate having 3 to 9 carbon atoms: ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate and the like. Among these, ethylene carbonate and propylene carbonate are more preferable. (2) Lactone compound having 3 to 9 carbon atoms: γ-butyrolactone, γ-valerolactone, δ-valerolactone and the like can be mentioned, and among these, γ-butyrolactone is more preferable.

(3) Chain carbonate having 3 to 9 carbon atoms: dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, di-n
-Butyl carbonate, diisopropyl carbonate,
Di-t-butyl carbonate, n-butyl isobutyl carbonate, n-butyl-t-butyl carbonate, isobutyl-t-butyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate, n-butyl-n-propyl carbonate, isobutyl-n-propyl carbonate, t-butyl-n −
Propyl carbonate, n-butyl isopropyl carbonate, isobutyl isopropyl carbonate, t-butyl isopropyl carbonate, etc. can be mentioned. Of these, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferred. (4) Carboxylic acid ester having 3 to 9 carbon atoms: methyl acetate, ethyl acetate, acetic acid-n-propyl acetate, isopropyl acetate, acetic acid-n-butyl acetate, isobutyl acetate, acetic acid-t-butyl, methyl propionate, ethyl propionate , -N-propyl propionate, isopropyl propionate,
-N-butyl propionate, isobutyl propionate,
Mention may be made of t-butyl propionate. Among these, ethyl acetate, methyl propionate and ethyl propionate are more preferable. (5) C3-C6 chain ethers: dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, ethoxymethoxyethane and the like can be mentioned. Among these, dimethoxyethane and diethoxyethane are more preferable.

In the present invention, the non-aqueous solvent in the non-aqueous electrolyte is selected from the group consisting of lactone compounds having 3 to 9 carbon atoms, cyclic carbonates, chain carbonates, chain ethers and chain carboxylic acid esters. It is preferable that the content of at least 70% by volume of the above-mentioned one or more kinds is 20% by volume or more of the non-aqueous solvent, and that one or more kinds selected from the group consisting of a lactone compound having 3 to 9 carbon atoms and a cyclic carbonate.

The solute used in the non-aqueous electrolyte of the present invention
Then, a lithium salt is used. About lithium salt
Is not particularly limited as long as it can be used as a solute.
Absent. For example, the following are examples.
You can (1) Inorganic lithium salt: LiPF₆, LiAsF₆, L
iBF_Four, LiAlF _FourInorganic fluoride salts such as LiCl
O_Four, LiBrO_Four, LiIO_FourPerhalogenates such as.

(2) Organolithium salt: LiCF₃SO₃
Organic sulfonates such as LiN (CF₃SO₂)₂, L
iN (C₂F_FiveSO₂)₂, LiN (CF₃SO₂)
(C_FourF₉SO₂) Etc. perfluoroalkyl sulfone
Acid imide salt, LiC (CF₃SO₂)₃Etc. perfluo
Low alkyl sulfonic acid methide salt, LiPF (C
F₃)_Five, LiPF₂(CF₃)_Four, LiPF₃(CF
₃)₃, LiPF₂(C₂F_Five) _Four, LiPF₃(C₂
F_Five)₃, LiPF (n-C₃F₇)_Five, LiPF
₂(N-C₃F₇)_Four, LiPF₃(N-C
₃F₇)₃, LiPF (iso-C₃F₇)_Five, LiP
F₂(Iso-C₃F₇)_Four  , LiPF₃(Iso-
C₃F₇)₃ , LiB (CF₃)_Four, LiBF (C
F₃)₃, LiBF₂(CF₃)₂, LiBF₃(CF
₃), LiB (C₂F_Five)_Four, LiBF (C
₂F_Five)₃, LiBF₂(C₂F_Five)₂, LiBF
₃(C₂F_Five), LiB (n-C₃F₇)_Four, LiBF
(N-C₃F₇)₃, LiBF₂(N-C₃F₇)₂,
LiBF₃(N-C₃F₇), LiB (iso-C₃F
₇)_Four, LiBF (iso-C₃F₇)₃, LiBF₂
(Iso-C₃F₇)₂, LiBF₃(Iso-C₃F
₇) Etc., some of the fluorine atoms of the inorganic fluoride salt
Examples include salts substituted with an oloalkyl group.

Among these, LiPF ₆ , LiBF ₄ ,
_{LiCF 3 SO 3, LiN (CF} 3 SO 2) 2, LiN
(C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄
F ₉ SO ₂ ), LiPF ₃ (CF ₃ ) ₃ , LiPF
₃ (C ₂ F ₅ ) ₃ , LiBF ₂ (CF ₃ ) ₂ , LiBF
₂ (C ₂ F ₅ ) ₂ is more preferable. These solutes may be used as a mixture of two or more.

The concentration of solute lithium salt in the non-aqueous electrolyte is preferably 0.5 to 3 mol / liter.
If the concentration is too low, the electrical conductivity of the electrolyte is insufficient due to an absolute lack of concentration, while if the concentration is too high, the electrical conductivity decreases due to an increase in viscosity, and precipitation at low temperature occurs. This is not preferable because the performance of the battery deteriorates because it becomes easier.

In the present invention, the non-aqueous solvent contains a sulfolane compound in which one or more hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with fluorine atoms, that is, a fluorinated sulfolane compound. The sulfolane fluoride compound is
You may have a substituent in the range which does not obstruct the desired effect of this invention excessively. Specifically, the following may be mentioned.

(1) Fluorosulfolane compound having no substituent: 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,
5-difluorosulfolane, 3,4-difluorosulfolane, 2,2,3-trifluorosulfolane, 2,2
3-trifluorosulfolane, 2,3,3-trifluorosulfolane, 2,2,4-trifluorosulfolane,
2,2,5-trifluorosulfolane, 2,3,4-trifluorosulfolane, 2,3,5-trifluorosulfolane, 2,4,4-trifluorosulfolane, 2,
2,3,3-tetrafluorosulfolane, 2,2,3
4-tetrafluorosulfolane, 2,2,4,4-tetrafluorosulfolane, 2,2,5,5-tetrafluorosulfolane, 2,3,3,4-tetrafluorosulfolane, 2,3,3,5- Tetrafluorosulfolane,
2,3,4,4-tetrafluorosulfolane, 2,3
4,5-tetrafluorosulfolane, 2,2,3,3
4-pentafluorosulfolane, 2,2,3,3,5-
Tetrafluorosulfolane, 2,2,3,4,4-tetrafluorosulfolane, 2,2,3,4,5-tetrafluorosulfolane, 2,3,3,4,4-tetrafluorosulfolane, 2,3 3,4,5-Tetrafluorosulfolane, 2,2,3,3,4,4-hexafluorosulfolane, 2,2,3,3,4,5-hexafluorosulfolane, 2,2,3,3 , 5,5-hexafluorosulfolane, 2,2,3,4,5,5-hexafluorosulfolane, 2,2,3,3,4,5, heptafluorosulfolane, 2,2,3,3 , 4,5,5-heptafluorosulfolane, octafluorosulfolane.

(2) Fluorosulfolane compound having an alkyl substituent: 2-fluoro-3-methylsulfolane,
2-fluoro-2-methylsulfolane, 3-fluoro-
3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methylsulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoro-2,4-dimethylsulfolane, 3-
Fluoro-2,4-dimethylsulfolane, 4-fluoro-2,4-dimethylsulfolane, 5-fluoro-2,4
-Dimethylsulfolane, 2,2-difluoro-3-methylsulfolane, 2,3-difluoro-3-methylsulfolane, 2,4-difluoro-3-methylsulfolane,
2,5-difluoro-3-methylsulfolane, 3,4-
Difluoro-3-methylsulfolane, 3,5-difluoro-3-methylsulfolane, 4,4-difluoro-3-
Methylsulfolane, 4,5-difluoro-3-methylsulfolane, 5,5-difluoro-3-methylsulfolane, 2,2,3-trifluoro-3-methylsulfolane, 2,2,4-trifluoro-3- Methylsulfolane, 2,2,5-trifluoro-3-methylsulfolane, 2,3,4-trifluoro-3-methylsulfolane, 2,3,5-trifluoro-3-methylsulfolane, 2,4,4 -Trifluoro-3-methylsulfolane, 2,4,5-trifluoro-3-methylsulfolane, 2,5,5-trifluoro-3-methylsulfolane, 3,4,4-trifluoro-3-methylsulfolane , 3,4,5-trifluoro-3-methylsulfolane, 4,4,5-trifluoro-3-methylsulfolane, 4,5,5-trifluoro-3-methyl Luforane, 2,2,3,4-tetrafluoro-3-methylsulfolane, 2,2,3,5-tetrafluoro-3-methylsulfolane, 2,2,4,4-tetrafluoro-3-methylsulfolane, 2,2,4,5-tetrafluoro-3
-Methylsulfolane, 2,2,5,5-tetrafluoro-3-methylsulfolane, 2,3,4,4-tetrafluoro-3-methylsulfolane, 2,3,4,5-tetrafluoro-3-methyl Sulfolane, 2,3,5,5-tetrafluoro-3-methylsulfolane, 3,4,4,5
-Tetrafluoro-3-methylsulfolane, 3,4
5,5-tetrafluoro-3-methylsulfolane, 4,
4,5,5-tetrafluoro-3-methylsulfolane,
2,2,3,4,4-pentafluoro-3-methylsulfolane, 2,2,3,4,5-pentafluoro-3-methylsulfolane, 2,2,3,5,5-pentafluoro-3 -Methylsulfolane, 2,3,4,5,5-pentafluoro-3-methylsulfolane, 2,3,4,5,5
-Pentafluoro-3-methylsulfolane, 2,2
3,4,4,5-hexafluoro-3-methylsulfolane, 2,2,3,4,5,5-hexafluoro-3-methylsulfolane, 2,3,4,4,5,5-hexafluoro -3-Methylsulfolane, heptafluoro-3-methylsulfolane.

(3) Fluorinated sulfolane compound having a monofluoroalkyl substituent: 2-fluoro-3- (fluoromethyl) sulfolane, 3-fluoro-3- (fluoromethyl) sulfolane, 4-fluoro-3- (fluoro) Methyl) sulfolane, 5-fluoro-3- (fluoromethyl) sulfolane, 2,2-difluoro-3- (fluoromethyl) sulfolane, 2,3-difluoro-3- (fluoromethyl) sulfolane, 2,4-difluoro- 3-
(Fluoromethyl) sulfolane, 2,5-difluoro-
3- (fluoromethyl) sulfolane, 3,4-difluoro-3- (fluoromethyl) sulfolane, 3,5-difluoro-3- (fluoromethyl) sulfolane, 4,4-
Difluoro-3- (fluoromethyl) sulfolane, 4,
5-difluoro-3- (fluoromethyl) sulfolane,
5,5-difluoro-3- (fluoromethyl) sulfolane, 2,2,3-trifluoro-3- (fluoromethyl) sulfolane, 2,2,4-trifluoro-3- (fluoromethyl) sulfolane, 2, 2,5-trifluoro-3- (fluoromethyl) sulfolane, 2,3,4-trifluoro-3- (fluoromethyl) sulfolane, 2,
3,5-trifluoro-3- (fluoromethyl) sulfolane, 2,4,4-trifluoro-3- (fluoromethyl) sulfolane, 2,4,5-trifluoro-3- (fluoromethyl) sulfolane, 2 , 5,5-Trifluoro-3- (fluoromethyl) sulfolane, 3,4,4-trifluoro-3- (fluoromethyl) sulfolane, 3,
4,5-trifluoro-3- (fluoromethyl) sulfolane, 4,5-trifluoro-3- (fluoromethyl) sulfolane, 4,5,5-trifluoro-3- (fluoromethyl) sulfolane, 2 , 2,3,4-Tetrafluoro-3- (fluoromethyl) sulfolane, 2,2
3,5-tetrafluoro-3- (fluoromethyl) sulfolane, 2,2,4,4-tetrafluoro-3- (fluoromethyl) sulfolane, 2,2,4,5-tetrafluoro-3- (fluoromethyl) ) Sulfolane, 2,2
5,5-tetrafluoro-3- (fluoromethyl) sulfolane, 2,3,4,4-tetrafluoro-3- (fluoromethyl) sulfolane, 2,3,4,5-tetrafluoro-3- (fluoromethyl) ) Sulfolane, 2, 3,
5,5-tetrafluoro-3- (fluoromethyl) sulfolane, 3,4,5,5-tetrafluoro-3- (fluoromethyl) sulfolane, 3,4,5,5-tetrafluoro-3- (fluoromethyl) ) Sulfolane, 4, 4,
5,5-tetrafluoro-3- (fluoromethyl) sulfolane, 2,2,3,4,4-pentafluoro-3-
(Fluoromethyl) sulfolane, 2,2,3,4,5-
Pentafluoro-3- (fluoromethyl) sulfolane,
2,2,3,5,5-pentafluoro-3- (fluoromethyl) sulfolane, 2,3,4,5,5-pentafluoro-3- (fluoromethyl) sulfolane, 2,3,3
4,5,5-pentafluoro-3- (fluoromethyl)
Sulfolane, 2,2,3,4,4,5-hexafluoro-3- (fluoromethyl) sulfolane, 2,2,3
4,5,5-hexafluoro-3- (fluoromethyl)
Sulfolane, 2,3,4,4,5,5-hexafluoro-3- (fluoromethyl) sulfolane, heptafluoro-3- (fluoromethyl) sulfolane.

(4) Fluorinated sulfolane compound having a difluoroalkyl substituent: 2-fluoro-3- (difluoromethyl) sulfolane, 3-fluoro-3- (difluoromethyl) sulfolane, 4-fluoro-3- (difluoromethyl) ) Sulfolane, 5-fluoro-3- (difluoromethyl) sulfolane, 2,2-difluoro-3-
(Difluoromethyl) sulfolane, 2,3-difluoro-3- (difluoromethyl) sulfolane, 2,4-difluoro-3- (difluoromethyl) sulfolane, 2,5
-Difluoro-3- (difluoromethyl) sulfolane,
3,4-difluoro-3- (difluoromethyl) sulfolane, 3,5-difluoro-3- (difluoromethyl)
Sulfolane, 4,4-difluoro-3- (difluoromethyl) sulfolane, 4,5-difluoro-3- (difluoromethyl) sulfolane, 5,5-difluoro-3-
(Difluoromethyl) sulfolane, 2,2,3-trifluoro-3- (difluoromethyl) sulfolane, 2,
2,4-trifluoro-3- (difluoromethyl) sulfolane, 2,2,5-trifluoro-3- (difluoromethyl) sulfolane, 2,3,4-trifluoro-3-
(Difluoromethyl) sulfolane, 2,3,5-trifluoro-3- (difluoromethyl) sulfolane, 2,
4,4-trifluoro-3- (difluoromethyl) sulfolane, 2,4,5-trifluoro-3- (difluoromethyl) sulfolane, 2,5,5-trifluoro-3-
(Difluoromethyl) sulfolane, 3,4,4-trifluoro-3- (difluoromethyl) sulfolane, 3,
4,5-trifluoro-3- (difluoromethyl) sulfolane, 4,5-trifluoro-3- (difluoromethyl) sulfolane, 4,5,5-trifluoro-3-
(Difluoromethyl) sulfolane, 2,2,3,4-tetrafluoro-3- (difluoromethyl) sulfolane,
2,2,3,5-tetrafluoro-3- (difluoromethyl) sulfolane, 2,2,4,4-tetrafluoro-
3- (difluoromethyl) sulfolane, 2,2,4,5
-Tetrafluoro-3- (difluoromethyl) sulfolane, 2,2,5,5-tetrafluoro-3- (difluoromethyl) sulfolane, 2,3,4,4-tetrafluoro-3- (difluoromethyl) sulfolane, 2, 3,
4,5-Tetrafluoro-3- (difluoromethyl) sulfolane, 2,3,5,5-tetrafluoro-3- (difluoromethyl) sulfolane, 3,4,5,5-tetrafluoro-3- (difluoromethyl) ) Sulfolane, 3,
4,5,5-tetrafluoro-3- (difluoromethyl) sulfolane, 4,4,5,5-tetrafluoro-3
-(Difluoromethyl) sulfolane, 2,2,3,4
4-pentafluoro-3- (difluoromethyl) sulfolane, 2,2,3,4,5-pentafluoro-3- (difluoromethyl) sulfolane, 2,2,3,5,5-pentafluoro-3- ( Difluoromethyl) sulfolane,
2,3,4,5,5-pentafluoro-3- (difluoromethyl) sulfolane, 2,3,4,5,5-pentafluoro-3- (difluoromethyl) sulfolane, 2,
2,3,4,5,5-hexafluoro-3- (difluoromethyl) sulfolane, 2,2,3,4,5,5-hexafluoro-3- (difluoromethyl) sulfolane,
2,3,4,4,5,5-hexafluoro-3- (difluoromethyl) sulfolane, heptafluoro-3- (difluoromethyl) sulfolane.

(5) Fluorosulfolane compounds having trifluoroalkyl substituents: 2-fluoro-3- (trifluoromethyl) sulfolane, 3-fluoro-3- (trifluoromethyl) sulfolane, 4-fluoro-3-
(Trifluoromethyl) sulfolane, 5-fluoro-3
-(Trifluoromethyl) sulfolane, 2,2-difluoro-3- (trifluoromethyl) sulfolane, 2,3
-Difluoro-3- (trifluoromethyl) sulfolane, 2,4-difluoro-3- (trifluoromethyl)
Sulfolane, 2,5-difluoro-3- (trifluoromethyl) sulfolane, 3,4-difluoro-3- (trifluoromethyl) sulfolane, 3,5-difluoro-3
-(Trifluoromethyl) sulfolane, 4,4-difluoro-3- (trifluoromethyl) sulfolane, 4,5
-Difluoro-3- (trifluoromethyl) sulfolane, 5,5-difluoro-3- (trifluoromethyl)
Sulfolane, 2,2,3-trifluoro-3- (trifluoromethyl) sulfolane, 2,2,4-trifluoro-3- (trifluoromethyl) sulfolane, 2,2,5
-Trifluoro-3- (trifluoromethyl) sulfolane, 2,3,4-trifluoro-3- (trifluoromethyl) sulfolane, 2,3,5-trifluoro-3-
(Trifluoromethyl) sulfolane, 2,4,4-trifluoro-3- (trifluoromethyl) sulfolane,
2,4,5-Trifluoro-3- (trifluoromethyl) sulfolane, 2,5,5-trifluoro-3- (trifluoromethyl) sulfolane, 3,4,5-trifluoro-3- (trifluoro) Methyl) sulfolane, 3,
4,5-trifluoro-3- (trifluoromethyl) sulfolane, 4,5-trifluoro-3- (trifluoromethyl) sulfolane, 4,5,5-trifluoro-
3- (trifluoromethyl) sulfolane, 2,2,3
4-tetrafluoro-3- (trifluoromethyl) sulfolane, 2,2,3,5-tetrafluoro-3- (trifluoromethyl) sulfolane, 2,2,4,4-tetrafluoro-3- (trifluoro Methyl) sulfolane,
2,2,4,5-tetrafluoro-3- (trifluoromethyl) sulfolane, 2,2,5,5-tetrafluoro-3- (trifluoromethyl) sulfolane, 2,3
4,4-tetrafluoro-3- (trifluoromethyl)
Sulfolane, 2,3,4,5-tetrafluoro-3-
(Trifluoromethyl) sulfolane, 2,3,5,5-
Tetrafluoro-3- (trifluoromethyl) sulfolane, 3,4,5,5-tetrafluoro-3- (trifluoromethyl) sulfolane, 3,4,5,5-tetrafluoro-3- (trifluoromethyl) Sulfolane, 4,
4,5,5-tetrafluoro-3- (trifluoromethyl) sulfolane, 2,2,3,4,4-pentafluoro-3- (trifluoromethyl) sulfolane, 2,2
3,4,5-pentafluoro-3- (trifluoromethyl) sulfolane, 2,2,3,5,5-pentafluoro-3- (trifluoromethyl) sulfolane, 2,3,3
4,4,5-pentafluoro-3- (trifluoromethyl) sulfolane, 2,3,4,5,5-pentafluoro-3- (trifluoromethyl) sulfolane, 2,2
3,4,5,5-hexafluoro-3- (trifluoromethyl) sulfolane, 2,2,3,4,5,5-hexafluoro-3- (trifluoromethyl) sulfolane,
2,3,4,4,5,5-hexafluoro-3- (trifluoromethyl) sulfolane, heptafluoro-3-
(Trifluoromethyl) sulfolane.

The fluorinated sulfolane compound can be produced, for example, by contacting sulfolane or a sulfolane having a substituent (hereinafter collectively referred to as sulfolanes) with fluorine gas to cause a reaction. As the sulfolane having a substituent, for example, sulfolane having an alkyl group is used. Since the fluorine gas used in the above reaction has extremely high reactivity, it is preferable to use one diluted with a gas inert to the fluorine gas in order to prevent the reaction from running away. As such an inert gas, nitrogen, helium, hydrogen fluoride or a perfluoroalkane having 4 or less carbon atoms is used. The concentration of fluorine gas in the inert gas is usually 1 to 50% by volume, preferably 5 to
It is 30% by volume. The charging molar ratio of fluorine gas (F ₂ ) to sulfolane is usually 0.01 to 10, but more preferably 0.1 to 2.

The reaction of sulfolane with fluorine gas is usually carried out by introducing diluted fluorine gas into liquid phase sulfolane, but the reaction is carried out in the presence of a solvent inert to fluorine gas. May be. The reaction temperature is usually -80.
C. to 100.degree. C., preferably -30.degree. C. to 80.degree. The reaction pressure is usually atmospheric pressure, but in some cases it may be carried out under reduced pressure or increased pressure. The reaction time varies depending on the type of sulfolane, the type of solvent, the reaction temperature, the target compound, etc., but is usually 1 to 500 hours.

During the above reaction, a fluoride salt such as sodium fluoride may be added to the reaction system in order to absorb hydrogen fluoride produced by the reaction. It is also possible to vaporize the sulfolane and carry out it in a gas phase reaction with fluorine gas. Also in this case, it is necessary to dilute with an inert gas in order to prevent runaway of the reaction. The reaction temperature may be 30 to 250 ° C., but 50
It is preferable to carry out in the range of to 150 ° C.

The reaction system may be a batch system, a semi-batch system, or a flow system, and a microreactor whose heat transfer can be easily controlled can also be used. As the fluorinated sulfolane compound obtained by the reaction, various substitution products from mono-substitution products, di-substitution products to perfluoro-substitution products are considered. By adjusting the reaction conditions, the desired substitution product can be obtained in a higher yield. However, if excessive fluorination is carried out, the obtained fluorinated sulfolane compound tends to be unstable, and production and separation from isomers become difficult. Furthermore, if perfluorination is carried out, separation from isomers is unnecessary. However, caution is required because the solubility of the product tends to decrease.

Suitable fluorinated sulfolane compounds include:
2-fluorosulfolane, 3-fluorosulfolane, 2
-Fluoro-3-methylsulfolane, 3-fluoro-3
-Methylsulfolane, 4-fluoro-3-methylsulfolane, 5-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-2-methylsulfolane,
5-fluoro-2-methylsulfolane, 2-fluoro-
2,4-dimethylsulfolane, 3-fluoro-2,4-
Examples thereof include monofluorosulfolane such as dimethylsulfolane, 4-fluoro-2,4-dimethylsulfolane, 5-fluoro-2,4-dimethylsulfolane, and more preferably 2-fluorosulfolane, 3-fluorosulfolane, 2-fluoro. Examples include -3-methylsulfolane, 3-fluoro-3-methylsulfolane, 4-fluoro-3-methylsulfolane, and 5-fluoro-3-methylsulfolane.

The fluorinated sulfolane compound may be used alone or as a mixture of two or more kinds, and may be used without separating the isomers which are difficult to separate during the production. Also, known compounds that can be added to the electrolytic solution of the lithium secondary battery,
For example, it may be used as a mixture with a film forming agent, an overcharge preventing agent, a dehydrating agent, a deoxidizing agent and the like. The compounding amount of the fluorinated sulfolane compound is preferably 0.01 to 10% by weight, more preferably 0.1 to 6% by weight, based on the weight of the non-aqueous electrolyte solution. If the blending amount is too large, battery characteristics such as charge / discharge efficiency and storage characteristics may deteriorate.

The material of the negative electrode constituting the lithium secondary battery of the present invention is not particularly limited as long as it contains a material capable of inserting and extracting lithium. Specific examples thereof include various thermal decomposition conditions. Examples thereof include thermal decomposition products of organic substances, carbon materials such as artificial graphite and natural graphite, metal oxide materials, lithium metal, and various lithium alloys.

Of these, the carbon material is preferably a seed.
By high temperature heat treatment of graphitizable pitch obtained from various raw materials
Manufactured artificial graphite and purified natural graphite or their black
Examples of materials include lead that has been subjected to various surface treatments including pitch.
Be done. These carbon materials were obtained by X-ray diffraction using the Gakushin method.
The d value (interlayer distance) of the lattice plane (002) plane is 0.335.
~ 0.34 nm, more preferably 0.335 to 0.33
It is preferably 7 nm. These carbon materials are ash
Is 1% by weight or less, more preferably 0.5% by weight or less,
X-rays by 0.1% by weight or less and Gakshin method
The crystallite size (Lc) determined by diffraction is 30 nm or more.
Preferably. Crystallite size (Lc) is 50 nm
The above is more preferable, and 100 nm or more is more preferable.
Is preferred. Also, the median diameter is laser diffraction / scattering.
The median diameter by the method is 1 to 100 μm, preferably 3
-50 μm, more preferably 5-40 μm, and even more preferably
The thickness is 7 to 30 μm. The BET specific surface area is
Normally 0.5-25.0m ²/ G, preferably
0.5-20.0m²/ G, more preferably 0.6-1
5.0 m²/ G, more preferably 0.6-10.0 m²
/ G. In addition, argon ion laser light was used
1580 to 1620 cm in Raman spectrum analysis
^-1Peak P in the range of_A(Peak intensity I_A) And 1350
1370 cm^-1Range peak P_B(Peak intensity I_B)
Intensity ratio R = I_B/ I_AIs 0 to 0.5, 1580 to 1
620 cm^-1The peak half-width of the range is 26 cm^-1Since
Below, further 25 cm^-1The following is more preferable.

It is also possible to mix these carbonaceous materials with a metal compound capable of absorbing and releasing lithium. Examples of metal compounds other than carbonaceous materials capable of inserting and extracting lithium include Ag, Zn, Al, Ga, In and S.
i, Ge, Sn, Pb, P, Sb, Bi, Cu, Ni,
Examples thereof include alloys of metals such as Sr and Ba and Li, metal oxides of these metals, and lithium metal, but Sn oxide, Si oxide, Al oxide, Sn, Si are preferable.
And lithium alloys of Al and metallic lithium.

These negative electrode materials may be used as a mixture of two or more kinds. The method for producing a negative electrode using these negative electrode materials is not particularly limited. For example, a negative electrode can be manufactured by adding a binder, a thickener, a conductive material, a solvent and the like to the negative electrode material to form a slurry, applying the slurry to the substrate of the current collector, and drying. Alternatively, the negative electrode material may be roll-formed as it is to form a sheet electrode, or compression molding may be performed to form a pellet electrode.

When the binder is used, it is not particularly limited as long as it is a stable material with respect to the solvent and the electrolytic solution used at the time of manufacturing the electrode, and other materials used at the time of using the battery. Specific examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, isoprene rubber and butadiene rubber. When using a thickener, the solvent or electrolyte used during electrode production,
There is no particular limitation as long as it is a material that is stable with respect to other materials used when using the battery. Specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch and casein.

Further, when the conductive material is used, it is not particularly limited as long as it is a stable material with respect to the solvent and the electrolytic solution used in manufacturing the electrode and other materials used in the battery. Specific examples thereof include metal materials such as copper and nickel, and carbon materials such as graphite and carbon black. As the material of the negative electrode current collector, a metal such as copper, nickel or stainless steel is used, and among these, a copper foil is preferable from the viewpoints of being easily processed into a thin film and cost.

The material of the positive electrode constituting the lithium secondary battery of the present invention is capable of inserting and extracting lithium such as lithium transition metal composite oxide such as lithium cobalt oxide, lithium nickel oxide and lithium manganese oxide. Materials can be used. The manufacturing method of the positive electrode is not particularly limited, and the positive electrode can be manufactured according to the above-described manufacturing method of the negative electrode. Regarding the shape, a binder, a conductive material, a solvent, etc. are added to the positive electrode material as needed and mixed, and then applied to the substrate of the current collector to form a sheet electrode, or press-molded to form a pellet electrode. Can be

As the material of the positive electrode current collector, a metal such as aluminum, titanium or tantalum or an alloy thereof is used.
Among these, aluminum or its alloy is lightweight and therefore desirable in terms of energy density. The material and shape of the separator used in the battery of the present invention are not particularly limited. However, it is preferable to select from materials that are stable to the electrolytic solution and have excellent liquid retaining properties, and it is preferable to use a porous sheet or nonwoven fabric made of polyolefin such as polyethylene or polypropylene as a raw material.

The method for producing the lithium secondary battery of the present invention provided with the negative electrode, the positive electrode and the non-aqueous electrolyte solution is not particularly limited, and can be appropriately selected from the commonly used methods. In addition, the shape of the battery is not particularly limited, and a cylinder type in which a sheet electrode and a separator are formed in a spiral shape, a cylinder type of an inside-out structure in which a pellet electrode and a separator are combined, and a coin type in which a pellet electrode and a separator are stacked are used. It is possible.

[0038]

EXAMPLES Hereinafter, specific embodiments of the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. [Production of Positive Electrode] As a positive electrode active material, 85% by weight of LiCoO ₂ was mixed with 6% by weight of carbon black and 9% by weight of polyvinylidene fluoride (Kureha Chemical Co., Ltd., trade name: KF-1000), and mixed to obtain N-methyl- Disperse with 2-pyrrolidone,
The thickness of the slurry is 20 μm, which is the positive electrode current collector.
1 aluminum foil is evenly coated and dried, then diameter 1
It was punched into a 2.5 mm disk shape to obtain a positive electrode.

[Preparation of Negative Electrode] Lattice plane in X-ray diffraction
The d value of (002 plane) is 0.336 nm, and the crystallite size (L
c) is 100 nm or more (264 nm), ash content is 0.0
4% by weight, median diameter by laser diffraction / scattering method is 1
7 μm, BET specific surface area 8.9 m²/ G, argon
Raman spectrum analysis using ion laser light
1580 to 1620 cm^-1Range peak P_A(Pee
Strength I_A) And 1350-1370 cm ^-1Range of pea
Ku P_B(Peak intensity I_B) And intensity ratio R = I_B/ I_ABut
0.15, 1580-1620 cm^-1Range of peaks
Full width at half maximum is 22.2 cm^-1Artificial graphite powder (Timuka
Manufactured by Le Co., trade name: KS-44) 94% by weight with distilled water
Solid styrene-butadiene rubber (SBR)
At 6% by weight and mixed with a disperser
Then, a slurry-like material having a thickness of 18
Uniformly applied on a copper foil of μm, dried and then 12.5m in diameter
m punched into a disk shape to make an electrode and use it as the negative electrode
It was

[Fabrication of coin type cell] Using the above positive electrode, negative electrode and non-aqueous electrolyte solution, the positive electrode was housed in a stainless steel can which also serves as the positive electrode conductor, and the electrolytic solution was impregnated on the positive electrode. The negative electrode was placed via a polyethylene separator. The can body and the sealing plate which also serves as the negative electrode conductor were caulked and sealed via an insulating gasket to produce a coin cell.

[Evaluation of coin type cell] At 25 ° C.
0.5 at charge end voltage of 4.2V and discharge end voltage of 2.5V
A charge / discharge test was conducted at a constant current of mA, and a value obtained by dividing the discharge capacity at the second cycle by the charge capacity at the second cycle was defined as the charge / discharge efficiency at the second cycle. Also, after charging under the same conditions after 4 cycles, as the 5th cycle, after charging with a constant current of 0.5 mA, a discharge test was performed at a constant current of 5 mA, and the value divided by the discharge capacity of the 4th cycle was discharged with a large current. Characterized.

Further, after the fifth cycle of discharge, a further 0.
It is discharged at a constant current of 5 mA, and it is charged again for 7 hours at 85 ° C.
After storing for 2 hours, the battery was discharged, and then the 7th cycle was charged and discharged. A value obtained by dividing the discharge capacity at the 7th cycle by the charge capacity at the 7th cycle was defined as the storage characteristic. [Example 1] Ethylene carbonate and diethyl carbonate in a weight ratio of 1: lithium hexafluorophosphate was thoroughly dried under a dry argon atmosphere mixed solvent to 1 (LiPF ₆₎ of 1 mol / liter as a solute Dissolve in a proportion, further dissolve 3-fluorosulfolane in a proportion of 2% by weight with respect to the weight of the electrolytic solution, to prepare a coin-type cell by the above method, the initial charge-discharge efficiency, storage characteristics
An evaluation was performed.

Example 2 L was added to a solvent prepared by mixing ethylene carbonate and diethyl carbonate in a weight ratio of 1: 1.
iPF ₆ was dissolved at a ratio of 1 mol / liter, and further 2-
Evaluation was carried out in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving fluorosulfolane in a ratio of 2% by weight with respect to the weight of the electrolytic solution was used.

[Example 3] L was added to a solvent prepared by mixing ethylene carbonate and diethyl carbonate at a weight ratio of 1: 1.
Example 1 except that iPF ₆ was dissolved at a rate of 1 mol / liter and 2-fluoro-3-methylsulfolane was dissolved at a rate of 2% by weight with respect to the weight of the electrolytic solution to prepare an electrolytic solution. Evaluation was carried out in the same manner as.

Example 4 L was added to a solvent prepared by mixing ethylene carbonate and diethyl carbonate at a weight ratio of 1: 1.
iPF ₆ was dissolved at a ratio of 1 mol / liter, and further 2-
Evaluation was performed in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving a mixture of fluorosulfolane: 3-fluorosulfolane in a molar ratio of 2: 8 at a ratio of 2% by weight based on the weight of the electrolytic solution was used. I did.

[Embodiment 5] Lithium tetrafluoroborate (LiBF ₄ ) was added in an amount of 1 mol / mol in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a weight ratio of 1: 1.
Evaluation was performed in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving 3 fluorosulfolane at a ratio of 2% by weight with respect to the weight of the electrolytic solution was used.

[Example 6] γ-butyrolactone was added to LiP
The same procedure as in Example 1 was carried out except that F ₆ was dissolved at a ratio of 1 mol / liter, and 3-fluorosulfolane was dissolved at a ratio of 2% by weight based on the weight of the electrolytic solution. And evaluated. [Comparative Example 1] Example 1 except that an electrolytic solution prepared by dissolving LiPF ₆ at a ratio of 1 mol / liter in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a weight ratio of 1: 1 was used. It evaluated similarly.

Comparative Example 2 A solvent prepared by mixing ethylene carbonate and diethyl carbonate in a weight ratio of 1: 1 was added.
Evaluation was performed in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving LiBF ₄ at a rate of 1 mol / liter was used. Comparative Example 3 Evaluation was performed in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving LiPF _{6 in} γ-butyrolactone at a ratio of 1 mol / liter was used.

The results of these evaluations are shown in Table 1.

[0050]

[Table 1]

[0051]

By using the non-aqueous electrolyte solution of the present invention, a non-aqueous electrolyte secondary battery having improved charge / discharge efficiency and storage characteristics even at high temperatures can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 4/58 C07D 307/32 E (72) Inventor Makoto Ue 3rd, Chuo 8-chome, Ami-cho, Inashiki-gun, Ibaraki No. 1 Mitsubishi Chemical Co., Ltd. F-term (reference) 4C037 EA20 LA03 5H029 AJ02 AJ03 AJ07 AK03 AL02 AL06 AL07 AL12 AL18 AM03 AM04 AM05 AM07 CJ08 HJ01 HJ02 HJ07 HJ13 5H050 AA02 AA08 AA10 AA13 BA15 CA08 HA01 CB02 CB02 CB02 CB02 CB02 CB02 CB02 CB02 HA07 HA10 HA13

Claims (9)

[Claims] 1. A non-aqueous electrolyte solution comprising a lithium salt dissolved in a non-aqueous solvent, wherein the non-aqueous solvent has at least one hydrogen atom bonded to a carbon atom constituting a sulfolane ring substituted with a fluorine atom. A non-aqueous electrolyte solution for a lithium secondary battery, which contains a sulfolane compound (hereinafter referred to as a fluorinated sulfolane compound). 2. The fluorinated sulfolane compound is 2-fluorosulfolane, 3-fluorosulfolane, 2-fluoro-3-methylsulfolane, 3-fluoro-3-methylsulfolane, 4-fluoro-3-methylsulfolane and 5
The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, which is at least one compound selected from the group consisting of -fluoro-3-methylsulfolane. 3. The non-aqueous electrolyte solution for a lithium secondary battery according to claim 1, which contains a fluorinated sulfolane compound in an amount of 0.01 to 10% by weight based on the weight of the electrolyte solution. 4. 70% by volume or more of the non-aqueous solvent is at least one selected from the group consisting of a lactone compound having 3 to 9 carbon atoms, a cyclic carbonate, a chain carbonate, a chain ether and a chain carboxylic acid ester. The organic solvent, and 20% by volume or more of the non-aqueous solvent is at least one organic solvent selected from the group consisting of a lactone compound having 3 to 9 carbon atoms and a cyclic carbonate, respectively. The non-aqueous electrolyte solution for a lithium secondary battery according to. 5. The lithium salt is LiPF₆, LiB
F_Four, LiCF₃SO₃, LiN (CF₃SO₂)₂, L
iN (CF₃CF₂SO₂)₂, LiN (CF ₃S
O₂) (C_FourF₉SO₂), LiPF₃(CF₃)₃,
LiPF₃  (C₂F_Five)₃, LiBF₂(CF₃)₂Over
And LiBF₂(C₂F_Five)₂Selected from the group consisting of
Any one of claims 1 to 4, which is at least one of thium salts.
A non-aqueous electrolyte solution for a lithium secondary battery according to any one of the above. 6. A negative electrode containing metallic lithium, a lithium alloy, or a material capable of inserting and extracting lithium,
A lithium secondary battery comprising a positive electrode containing a material capable of inserting and extracting lithium, and a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte solution is 5. A lithium secondary battery, which is the non-aqueous electrolyte for a lithium secondary battery according to any one of 5 above. 7. The negative electrode has a lattice plane (00) in X-ray diffraction.
The lithium secondary battery according to claim 6, which contains a carbon material having a surface d value of 0.335 to 0.34 nm. 8. The lithium secondary battery according to claim 6, wherein the positive electrode contains a lithium transition metal composite oxide. 9. The lithium secondary battery according to claim 8, wherein the positive electrode contains at least one lithium-transition metal composite oxide selected from the group consisting of lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide. Next battery.