JP2002083629A - Nonaqueous electrolytic solution and secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution which has superior wettability with respect to a separator, without lowering a flash point of the whole electrolytic solution and which is improved in safety, and to provide a lithium secondary battery containing the solution. SOLUTION: This nonaqueous electrolytic solution has a nonaqueous solvent as a main solvent, whose flash point is not less than 70 deg.C, and that is composed of a mixed solvent, containing aliphatic carbonate ester expressed by formula (1) R1-(OA)m-OCOO-(BO)n-R2 and Li salt electrolyte, where the content of aliphatic carbonate ester is 0.1 to 20 wt.% to the total nonaqueous solvent (the total amount of the aliphatic carbonate ester and other nonaqueous solvents), and a lithium secondary battery containing the solution. In the formula, R1 and R2 are hydrocarbon groups of 1-12C and may have branches, and A and B are hydrocarbons of -CH2CH2-, -CH2CH(CH3)- or -CH(CH3)CH2-, and the sum total of carbon number and oxygen number of R1-(OA)m- group and/or R2-(OB)n- group is not less than 4, and m and n are integers of 0 to 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte having excellent safety and a secondary battery using the same. More specifically, the present invention provides a non-aqueous electrolytic solution showing excellent battery characteristics even when a high flash point solvent is used as a main solvent by using a specific chain carbonate, and a non-aqueous electrolytic solution using the same. The present invention relates to a liquid secondary battery.

[0002]

BACKGROUND OF THE INVENTION A battery using a non-aqueous electrolyte has a high voltage, a high energy density, and a high reliability such as storability, so that it is widely used as a power source for consumer electronic devices. Have been.

As such a battery, there is a non-aqueous electrolyte secondary battery, a typical example of which is a lithium ion secondary battery. As the non-aqueous solvent used for the compound, the solubility of the lithium salt, high ion dissociation, and, from the viewpoint of safety, a carbonate compound having a high dielectric constant and a high flash point, such as a cyclic ester, a cyclic amide, and a cyclic imide. Use has been proposed. In addition, LiBF ₄ , LiP
F ₆ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li ₂
SiF _{6 and the} like are known. However, if only a (dielectric) solvent having a high dielectric constant is used, the wettability to the separator is poor, and the battery does not operate. Then, it is mixed with a low dielectric constant solvent such as dimethyl carbonate, and LiBF ₄ , LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiAs
It has been proposed that an electrolyte such as CF ₃ SO ₃ or Li ₂ SiF _{6 be} mixed and used as an electrolyte.

However, an electrolytic solution containing a large amount of a linear carbonic acid ester having a small number of carbon atoms, such as dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate, is not always satisfactory from the viewpoint of obtaining an electrolytic solution having a high flash point. .

[0005] The present inventors consider the above points,
The present invention has been achieved as a result of intensive efforts to develop an electrolyte having good characteristics while maintaining a high flash point of the entire electrolyte.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-aqueous electrolyte having improved safety, which has good wettability to a separator without lowering the flash point of the entire electrolyte. . It is another object of the present invention to provide a secondary battery containing the non-aqueous electrolyte, particularly a lithium secondary battery.

[0007]

According to the present invention, a flash point of 70 is provided.
A non-aqueous solvent containing a non-aqueous solvent of at least 1 ° C. as a main solvent, at least one chain carbonate represented by the following general formula (1), and a non-aqueous electrolyte solution containing a Li salt electrolyte; The content of the linear carbonate is 0.1 to 2 with respect to the total nonaqueous solvent (total amount of the chain carbonate and the other nonaqueous solvent).
Provide a non-aqueous electrolyte that is 0% by weight. R ^1- (OA) _m -OCOO- (BO) _n -R ² (1) (In the formula (1), R ¹ and R ² may be the same or different, and may have a branch. Good carbon number 1-12
Of a hydrocarbon group, A, B, which may be different from one another the _{same, -CH 2 CH 2 -, -} CH 2 CH (C
A hydrocarbon group selected from the group consisting of H ₃ ) — and CH (CH ₃ ) CH ₂ —; a group represented by R ¹ — (OA) _m — and / or a group represented by R ² — (OB) _n — The total number of carbon atoms and oxygen atoms contained in the group represented is 4 or more, and m and n are each independently an integer of 0 to 4)

Di-n-butyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone,
At least one flash point selected from the group consisting of δ-valerolactone contains, as a main component, all other non-aqueous solvents having a temperature of 70 ° C. or higher, and di-n-butyl carbonate is used as a non-aqueous solvent (di-n-butyl). The non-aqueous solvent containing the non-aqueous solvent contained at a concentration of 0.5 to 10% by weight with respect to the total amount of carbonate and other solvents) and the non-aqueous electrolyte composed of the lithium salt electrolyte correspond to specific embodiments of the present invention. This is an example.

Further, the present invention provides a secondary battery containing the above non-aqueous electrolyte.

Further, the present invention provides a method of doping lithium metal, a lithium-containing alloy, and lithium ion as a negative electrode active material.
A negative electrode containing any of the undoped carbon materials, a positive electrode containing any of a composite oxide of lithium and a transition metal, a carbon material or a mixture thereof as a positive electrode active material, and a lithium secondary battery containing the above non-aqueous electrolyte Provide the next battery.

[0011]

Next, the nonaqueous electrolyte according to the present invention and a secondary battery using the nonaqueous electrolyte will be described in detail.

The non-aqueous electrolyte of the present invention comprises a non-aqueous solvent having a flash point of 70 ° C. or higher as a main solvent, and a mixed solvent containing at least one chain carbonate represented by the following general formula (1):
A non-aqueous electrolyte containing a Li salt electrolyte, wherein the content of the chain carbonate is 0.1% with respect to the total non-aqueous solvent (the total amount of the chain carbonate and other non-aqueous solvents). Non-aqueous electrolyte solution characterized by being in the range of 20 to 20% by weight. R ^1- (OA) _m -OCOO- (BO) _n -R ² (1)

(In the formula (1), R ¹ and R ² may be the same or different from each other and may be a hydrocarbon group having 1 to 12 carbon atoms which may have a branch; May be the same or different, and —CH ₂ CH ₂ —, —C
_{H 2 CH (CH 3) -} , CH (CH 3) CH 2 - is a hydrocarbon group selected from the group consisting _{^{of, R 1 - (OA) m}} - group represented by and / or R ² - (OB The total number of carbon atoms and oxygen atoms contained in the group represented by _n- is 4 or more, and m and n are each independently an integer of 0 to 4.)

Chain Carbonate Esters The chain carbonate esters used in the present invention are represented by the above formula (1)
It is a compound represented by these.

R ¹ and R ² in the formula (1) are a hydrocarbon group having 1 to 12 carbon atoms which may have a branch. Specifically, methyl group, ethyl group, propyl group, is
o-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, n
-Hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group and the like. Among them, hydrocarbon groups having 1 to 4 carbon atoms such as methyl group, ethyl group, n-propyl group and n-butyl group are preferable, and methyl group, ethyl group and n-butyl group are particularly preferable.

In the formula (1), m and n are each independently an integer of 0 to 4. Among them, 0, 1 or 2 is preferable.

In the formula (1), R¹− (O
A)_mA group represented by-and / or R ^Two-(OB)_n−
The total number of carbon and oxygen contained in the group represented by is 4 or more
It is. Therefore, when both m and n are 0,
Is R¹And R^TwoHas at least one of 4 carbon atoms
These are the hydrocarbon groups.

Specific examples of the compound represented by the above formula (1)
And CH_Three-OCOO-C_FourH₉, C_TwoH_Five-OCOO-
C_FourH₉, C_FourH₉-OCOO-C_FourH₉, CH_Three-OCOO
− (CH_TwoCH_TwoO) -CH_Three, C_TwoH_Five-OCOO- (C
H_TwoCH_TwoO) -CH_Three, C_FourH₉-OCOO- (CH_TwoCH
_TwoO) -CH_Three, C_TwoH_Five-OCOO- (CH_TwoCH_TwoO)-
C_TwoH_Five, C_TwoH_Five-OCOO- (CH_TwoCH_TwoO) -C
_FourH₉, CH_Three− (OCH_TwoCH_Two) -OCOO- (CH_TwoC
H_TwoO) -CH_Three, CH_Three− (OCH_TwoCH_Two) -OCOO
− (CH_TwoCH_TwoO) -C_TwoH_Five, CH_Three− (OCH_TwoC
H_Two) -OCOO- (CH_TwoCH_TwoO) -C_FourH₉, C_TwoH_Five
− (OCH_TwoCH_Two) -OCOO- (CH_TwoCH_TwoO) -C
_TwoH_Five, C_TwoH_Five− (OCH_TwoCH_Two) -OCOO- (CH_Two
CH_TwoO) -C_FourH₉, CH_Three-OCOO- (CH_TwoCH
(CH_Three) O) -CH_Three, CH_Three-OCOO- (CH (C
H_Three) CH_TwoO) -CH_Three, C_TwoH_Five-OCOO- (CH_TwoC
H (CH_Three) O) -CH_Three, C_FourH₉-OCOO- (CH_Two
CH (CH_Three) O) -CH_Three, C_TwoH_Five-OCOO- (CH
(CH_Three) CH_TwoO) -CH_Three, C_FourH₉-OCOO- (C
H (CH_Three) CH_TwoO) -CH_Three, CH_Three-(OCH (CH
_Three) CH_Two) -OCOO- (CH_TwoCH (CH_Three) O) -C
H_Three, C_TwoH_Five-(OCH (CH_Three) CH_Two) -OCOO-
(CH_TwoCH (CH_Three) O) -CH_Three, C_FourH₉− (OCH
(CH_Three) CH_Two) -OCOO- (CH_TwoCH (CH_Three)
O) -CH_Three, CH_Three-(OCH (CH_Three) CH_Two) -OC
OO- (CH (CH_Three) CH_TwoO) -CH_Three, CH_Three− (O
CH_TwoCH (CH_Three))-OCOO- (CH (CH_Three) C
H_TwoO) -CH_Three, C_TwoH_Five− (OCH_TwoCH (CH_Three))-
OCOO- (CH (CH_Three) CH_TwoO) -CH_Three, C_FourH₉
− (OCH_TwoCH (CH_Three))-OCOO- (CH (CH
_Three) CH_TwoO) -CH_Three, CH_Three-OCOO- (CH_TwoCH_Two
O)_Two-CH_Three, C_TwoH_Five-OCOO- (CH_TwoCH_TwoO)_Two
-CH_Three, C _FourH₉-OCOO- (CH_TwoCH_TwoO)_Two-CH
_Three, C_TwoH_Five-OCOO- (CH_TwoCH_TwoO)_Two-C_TwoH_Five, C
_TwoH_Five-OCOO- (CH_TwoCH_TwoO)_Two-C_FourH₉, CH_Three−
(OCH_TwoCH_Two)_Two-OCOO- (CH_TwoCH_TwoO)_Two-C
H_Three, CH_Three− (OCH_TwoCH_Two)_Two-OCOO- (CH_TwoC
H_TwoO)_Two-C_TwoH_Five, CH_Three− (OCH_TwoCH_Two)_Two-OCO
O- (CH_TwoCH_TwoO)_Two-C_FourH₉, C_TwoH_Five− (OCH_TwoC
H_Two)_Two-OCOO- (CH_TwoCH_TwoO)_Two-C_TwoH_Five, C_FourH
₉− (OCH_TwoCH_Two)_Two-OCOO- (CH_TwoCH_TwoO)_Two
-C_FourH₉And the like.

Among them, preferred is CH_Three
-OCOO-C_FourH₉, C_TwoH_Five-OCOO-C_FourH₉, C_Four
H₉-OCOO-C_FourH₉, CH_Three-OCOO- (CH_TwoC
H_TwoO) -CH_Three, C_TwoH_Five-OCOO- (CH_TwoCH_TwoO)
-CH_Three, C_TwoH_Five-OCOO- (CH_TwoCH_TwoO) -C_TwoH
_Five, CH_Three− (OCH_TwoCH_Two) -OCOO- (CH_TwoCH _Two
O) -CH_Three, C_TwoH_Five− (OCH_TwoCH_Two) -OCOO-
(CH_TwoCH_TwoO) -C_TwoH_FiveCan be mentioned.

More preferably, CH ₃ —OCO
_{O-C 4 H 9, C} 2 H 5 -OCOO-C 4 H 9, C 4 H 9 -OC
It can be exemplified OO-C ₄ H _9. Among them, particularly preferred is CH ₃ CH ₂ CH ₂ CH ₂ —OCOO—CH ₂ CH ₂
Di-n-butyl carbonate represented by CH ₂ CH ₃ .

The chain carbonate of the present invention may be used alone or in combination of two or more.

The chain carbonate of the present invention is used in an amount of 0.1% by weight or more and 20% by weight or less, preferably 0.1% by weight, based on the total amount of the nonaqueous solvent (the total amount of the chain carbonate and other nonaqueous solvents). It is desirable that it be contained at a concentration of not less than 10% by weight, more preferably not less than 10% by weight.

When the specific chain carbonate represented by the above formula (1) of the present invention is contained in a non-aqueous solvent,
A battery using a non-aqueous electrolyte obtained even when a non-aqueous solvent having a flash point of 70 ° C. or more is used as a main solvent because the wettability of the separator is significantly improved while minimizing the decrease in the flash point. And excellent battery characteristics. Further, by using the specific chain carbonate represented by the formula (1), excellent battery characteristics are exhibited even when a high flash point solvent is used as a main solvent, and thus a non-aqueous electrolyte having a high flash point is obtained. Can be provided.

Non-aqueous solvent having a flash point of 70 ° C. or higher Specific examples of the non-aqueous solvent having a flash point of 70 ° C. or higher include ethylene carbonate, propylene carbonate,
Butylene carbonate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, N, N-dimethylacetamide, N, N-diethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, N-methyloxazolidinone, N-ethyloxazolidinone , N, N '
-Dimethylimidazolidinone, N, N'-diethylimidazolidinone, sulfolane, 3-methylsulfolane. Among them, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and δ-valerolactone are preferable, and particularly, ethylene carbonate, propylene carbonate, and γ-butyrolactone are preferable.
These cyclic carbonates may be used as a mixture of two or more kinds.

Non-aqueous Solvent Containing Chain Carbonate The non-aqueous solvent according to the present invention is a non-aqueous solvent having a flash point of 70 ° C. or more and at least one chain carbonate represented by the above formula (1). Containing non-aqueous solvent. The non-aqueous solvent of the present invention contains the chain carbonate and another non-aqueous solvent as main components. The chain carbonate is contained in an amount of 0.1% by weight or more and 20% by weight or less, preferably 0.1% by weight, based on the total amount of the nonaqueous solvent (the total amount of the chain carbonate and other nonaqueous solvents).
1% by weight or more and 10% by weight or less, more preferably 0.5% by weight or less.
It is desirable that the content be contained in a concentration of not less than 10% by weight and not more than 10% by weight.

The preferred combinations of the present invention are shown below from the above specific examples as the chain carbonate and nonaqueous solvent having a flash point of 70 ° C. or higher constituting the nonaqueous solvent of the present invention. Things can be mentioned. In these combinations, a nonaqueous solvent having a flash point of 70 ° C. or higher is used as a main solvent, and a specific amount of the chain carbonate represented by the formula (1) is included.

Therefore, the non-aqueous solvent according to the present invention is:
A non-aqueous solvent having a flash point of 70 ° C. or higher is used as a main solvent, and a specific amount of the chain carbonate represented by the general formula (1) is contained. Of these combinations, particularly preferred examples are specifically described as (ethylene carbonate (E
C), propylene carbonate (PC), methyl-n-butyl carbonate (MNBC)), (EC, γ-butyrolactone (GBL), MNBC), (PC, GBL, M
(NBC), (EC, PC, GBL, MNBC); (E
C, PC, ethyl-n-butyl carbonate (ENB
C)), (EC, GBL, ENBC), (PC, GB
L, ENBC), (EC, PC, GBL, ENBC);
(EC, PC, di-n-butyl carbonate (DNB
C)), (EC, GBL, DNBC), (PC, GB
L, DNBC), (EC, PC, GBL, DNBC). Among them, the most preferable example is (EC, P
C, DNBC), (EC, GBL, DNBC), (P
C, GBL, DNBC), (EC, PC, GBL, DN
BC).

Non-Aqueous Electrolyte The non-aqueous electrolyte of the present invention comprises the above-mentioned chain carbonate represented by the above formula (1) and another non-aqueous solvent, preferably another non-aqueous solvent having a flash point of 70 ° C. or more. It comprises a non-aqueous solvent containing an aqueous solvent and a lithium salt electrolyte. As the lithium salt electrolyte to be used, any one which is usually used as an electrolyte for a non-aqueous electrolyte can be used.

As a specific example of the electrolyte, LiPF₆, Li
BF_Four, LiClO_Four, LiAsF₆, Li _TwoSiF₆, LiC_FourF
₉SO_Three, LiC₈F₁₇SO_ThreeLithium salts such as
You. Also, the following general formula LiOSO_TwoR^Three, LiN (SO_TwoR^Four)
(SO_TwoR^Five), LiC (SO_TwoR⁶) (SO_TwoR⁷) (SO_TwoR⁸)Also
Or LiN (SO_TwoOR⁹) (SO_TwoOR^Ten) (Where R^Three
~ R^TenMay be the same or different from each other,
A perfluoroalkyl group having 1 to 6 carbon atoms)
Lithium salts can also be used. These litchi
Um salts may be used alone or as a mixture of two or more.
May be used.

Of these, LiPF ₆ , LiBF ₄ ,
LiOSO ₂ R ³ , LiN (SO ₂ R ⁴ ) (SO ₂ R ⁵ ), LiC (S
O ₂ R ⁶ ) (SO ₂ R ⁷ ) (SO ₂ R ⁸ ), LiN (SO ₂ OR ⁹ ) (S
O ₂ OR ¹⁰ ) is preferred.

It is desirable that such an electrolyte is usually contained in the non-aqueous electrolyte at a concentration of 0.1 to 3 mol / l, preferably 0.5 to 2 mol / l.

The non-aqueous electrolyte in the present invention essentially comprises another non-aqueous solvent containing a specific amount of the above-mentioned specific chain carbonate, preferably a non-aqueous solvent having a flash point of 70 ° C. or higher, and a lithium salt electrolyte. Although it is contained as a component, other additives and the like may be added as necessary.

The non-aqueous electrolyte in the present invention has a flash point of 70
The mixture contains a non-aqueous solvent at a temperature of at least 0 ° C. or higher, a mixed solvent containing a specific amount of the specific chain carbonate described above, and a lithium salt electrolyte as essential constituents. However, other additives may be added as necessary.

[0034] Additives that may be added include olefins, acetylenes (triple bond-containing compounds), carboxylic acids, acid anhydrides, sultones, and sulfones, which have an effect of maintaining capacity and / or load characteristics during storage at high temperatures. Examples include sulfur-containing compounds such as acids, sulfonic esters, and sulfonic anhydrides. Examples of additives that may be added include carbamate, (halogen-substituted) biphenyl, (halogen-substituted) terphenyl, halogenated benzene, and halogenated toluene, which have an overcharge preventing effect. In addition, a boric acid ester having an effect of suppressing gas generation during high-temperature storage or the like may be added as an additive to which the compound may be added. One or more of these additives may be added as a mixture.

Specific examples of such additives include:
Vinylene carbonate, vinyl ethylene carbonate, divinyl carbonate, tris (2-
(Carboxyethyl) isocyanurate, maleic anhydride, norbornene dicarponic anhydride, 1,3-propane sultone, divinyl sulfide, sulfobenzoic anhydride and phenyl sulfone.

Examples of the additive having an overcharge preventing effect include biphenyl-N, N-diethyl carbonate, cyclohexyl-N, N-diethyl carbonate, isopropyl-N, N-diethyl carbonate, methyl-N , N-dimethyl carbonate, ethyl-N, N
-Diethyl carbonate, methyl-N, N-diethyl carbonate, trifluoroether-N, N-dietercarbonate, trifluoroethyl-N, N-dimethylcarbonate, biphenyl, 4-fluorobiphenyl,
Examples include o-terphenyl, biphenyl ether, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, chlorobenzene, and fluorobenzene.

The non-aqueous electrolyte according to the present invention as described above
It is suitable as a non-aqueous electrolyte for a secondary battery, particularly for a lithium ion secondary battery.

Secondary Battery The non-aqueous electrolyte secondary battery according to the present invention basically comprises a negative electrode, a positive electrode, and the above-mentioned non-aqueous electrolyte, and usually comprises a negative electrode and a positive electrode. Is provided with a separator.

As the negative electrode active material constituting the negative electrode, any of lithium metal, a lithium alloy, and a carbon material capable of doping / de-doping lithium ions can be used. Among these, lithium ion
Carbon materials that can be de-dove are preferred. Such a carbon material may be graphite or amorphous carbon, activated carbon, carbon fiber, carbon black,
Mesocarbon microbeads and the like are used.

The nonaqueous electrolyte comprising the specific carbamate compound of the present invention, a nonaqueous solvent in which a cyclic carbonate and a nonaqueous solvent having a polar group are mixed at a specific ratio, and a lithium salt electrolyte constitutes a negative electrode. It is preferable that the negative electrode active material is a carbon material capable of doping / de-doping lithium ions, since the effect of preventing rapid heat generation and breakage of the battery due to overcharging is remarkably exhibited.

As the positive electrode active material constituting the positive electrode, Mo is used.
Transition metal oxide or transition metal sulfide such as S ₂ , TiS ₂ , MnO ₂ , V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , L
Composite oxides composed of lithium and a transition metal such as iMn ₂ O ₄ and LiNiO ₂ are given. Among these, a composite oxide composed of lithium and a transition metal is particularly preferable. When the negative electrode is a lithium metal or lithium alloy, a carbon material can be used as the positive electrode. Also,
As the positive electrode, a mixture of a composite oxide of lithium and a transition metal and a carbon material can be used.

The separator is a porous film, and usually a microporous polymer film is suitably used. In particular, a porous polyolefin film is preferable, and specific examples thereof include a porous polyethylene film, a porous polypropylene film, and a multilayer film of a porous polyethylene film and polypropylene.

Such a non-aqueous electrolyte secondary battery can be formed in a cylindrical shape, a coin shape, a square shape, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be changed according to the purpose. Next, the structures of the cylindrical and coin type batteries will be described. The negative electrode active material, the positive electrode active material, and the separator constituting each battery are commonly used.

For example, in the case of a cylindrical non-aqueous electrolyte secondary battery, a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector,
A positive electrode formed by applying a positive electrode active material to a positive electrode current collector is wound through a separator into which a non-aqueous electrolyte is injected, and is housed in a battery can with an insulating plate placed above and below the wound body. ing.

The non-aqueous electrolyte secondary battery according to the present invention can be applied to a coin-type non-aqueous electrolyte secondary battery. In a coin-type battery, a disk-shaped negative electrode, a separator, a disk-shaped positive electrode, and a stainless steel plate are housed in a coin-type battery can in a state of being stacked in this order. Further, the non-aqueous electrolyte secondary battery according to the present invention can also be applied to a rectangular non-aqueous secondary battery whose exterior is made of aluminum laminate.

[0046]

According to the present invention, the separator has good wettability to the separator without lowering the flash point of the entire electrolytic solution, that is, while maintaining the high flash point of the entire electrolytic solution. A water electrolyte is provided. The nonaqueous electrolyte according to the present invention is suitable as a nonaqueous electrolyte for a secondary battery, particularly for a lithium ion secondary battery.

[0047]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 <Preparation of Nonaqueous Electrolyte> Ethylene carbonate (EC, flash point: 160 ° C.) and γ-BL (GBL, flash point: 98 ° C.) were mixed with EC: GBL = 1: 1 (capacity). Ratio), 0.5 part by weight of di-n-butyl carbonate (flash point: 92 ° C., sometimes abbreviated as DNBC) was added to 99.5 parts by weight of the mixed solvent, and DNBC was added. Was adjusted to 0.5% by weight with respect to the total amount of the nonaqueous solvent (the total amount of EC, GBL, and DNBC). Next, LiPF ₆ as an electrolyte was dissolved in a non-aqueous solvent, and a non-aqueous electrolyte was prepared so that the electrolyte concentration was 1.0 mol / L.

<Measurement of Wettability to Separator> The non-aqueous electrolyte obtained in this manner was placed on a glass plate and placed on a 16 mm
100 μl was dropped on a φ PP separator, and the time until the electrolyte was impregnated into the separator and the separator stuck to the glass plate was measured. The results are shown in Table 1.

(Embodiment 2) In the embodiment 1, the DNBC
Was added, and the amount of DNBC was adjusted to the whole non-aqueous solvent (EC
And a nonaqueous solvent was prepared so as to be 3% by weight based on the total amount of GBL and DNBC), and a nonaqueous electrolytic solution was prepared in the same manner as in Example 1 to evaluate wettability to a separator. did. The results are shown in Table 1.

(Embodiment 3) In Embodiment 1, the DNBC
Was added, and the amount of DNBC was adjusted to the whole non-aqueous solvent (EC
And a nonaqueous solvent was prepared so as to be 5% by weight with respect to the total amount of GBL and DNBC), and a nonaqueous electrolyte solution was prepared in the same manner as in the example to evaluate wettability to the separator. . The results are shown in Table 1.

(Embodiment 4) In the embodiment 1, the DNBC
Was added, and the amount of DNBC was adjusted to the whole non-aqueous solvent (E
10% by weight based on the total amount of C, GBL and DNBC)
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that a non-aqueous solvent was prepared so that the wettability to the separator was evaluated. The results are shown in Table 1.

(Example 5) In Example 1, EC and propylene carbonate (PC) were mixed at a ratio of 1: 1 (weight ratio).
, And 5 parts by weight of di-n-butyl carbonate was added to 95 parts by weight of the mixed solvent, and DNB was added.
A non-aqueous electrolyte solution was prepared in the same manner as in Example 1 except that the non-aqueous solvent was prepared so that the amount of C was 5% by weight based on the whole non-aqueous solvent (the total amount of EC, PC, and DNBC). After the preparation, the wettability to the separator was evaluated. The results are shown in Table 1.

(Embodiment 6) In Embodiment 1, EC and P
After C and GBL were mixed at a ratio of EC: PC: GBL = 2: 1: 4 (weight ratio), 5 parts by weight of di-n-butyl carbonate was added to 95 parts by weight of the mixed solvent, and D was added.
When the amount of NBC is in the whole non-aqueous solvent (EC, PC, GBL, DN
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the non-aqueous solvent was prepared so as to be 5% by weight based on the total amount with BC, and the wettability to the separator was evaluated. The results are shown in Table 1.

(Embodiment 7) In Embodiment 1, EC and G
BL was mixed at a ratio of EC: GBL = 1: 2 (weight ratio), 5 parts by weight of di-n-butyl carbonate was added to 95 parts by weight of the mixed solvent, and the amount of DNBC was changed to a nonaqueous solvent. A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the non-aqueous solvent was prepared so as to be 5% by weight with respect to the whole (the total amount of EC, GBL, and DNBC), and wetted to the separator. The sex was evaluated. The results are shown in Table 1.

(Embodiment 8) In Embodiment 1, EC and G
BL was mixed at a ratio of EC: GBL = 1: 2 (weight ratio), 5 parts by weight of di-n-butyl carbonate was added to 95 parts by weight of the mixed solvent, and the amount of DNBC was changed to a nonaqueous solvent. After preparing a non-aqueous solvent to be 5% by weight with respect to the whole (the total amount of EC, GBL and DNBC), LiBF ₄ as an electrolyte was dissolved in the non-aqueous solvent, and the electrolyte concentration was 1.
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the non-aqueous electrolyte was prepared to be 0 mol / liter, and wettability to a separator was evaluated. The results are shown in Table 1.

(Comparative Example 1) In Example 1, the DNBC
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that was not added, and the wettability to the separator was evaluated. The results are shown in Table 1.

(Comparative Example 2) In Example 5, the DNBC
A non-aqueous electrolyte was prepared in the same manner as in Example 5 except that was not added, and the wettability to the separator was evaluated. The results are shown in Table 1.

(Comparative Example 3) In Example 6, the DNBC
A non-aqueous electrolyte was prepared in the same manner as in Example 6 except that was not added, and the wettability to the separator was evaluated. The results are shown in Table 1.

(Comparative Example 4) In Example 7, DNBC
A non-aqueous electrolyte was prepared in the same manner as in Example 7 except that was not added, and the wettability to the separator was evaluated. The results are shown in Table 1.

(Comparative Example 5) In Example 8, DNBC
A non-aqueous electrolyte was prepared in the same manner as in Example 8 except that was not added, and the wettability to the separator was evaluated. The results are shown in Table 1.

[0062]

[Table 1]

[Procedure amendment]

[Submission date] July 12, 2001 (2001.7.1)
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0062

[Correction method] Change

[Correction contents]

[0062]

[Table 1]

Claims (10)

[Claims] 1. A non-aqueous solvent having a flash point of 70 ° C. or higher as a main solvent, a mixed solvent containing at least one chain carbonate represented by the following general formula (1), and a non-aqueous solvent containing a Li salt electrolyte. An aqueous electrolyte, wherein the content of the chain carbonate is 0.1 to 20% by weight based on the total amount of the nonaqueous solvent (the total amount of the chain carbonate and other nonaqueous solvents). Non-aqueous electrolyte solution characterized by the above-mentioned. R ^1- (OA) _m -OCOO- (BO) _n -R ² (1) (In the formula (1), R ¹ and R ² may be the same or different, and may have a branch. Carbon number 1-12
Of a hydrocarbon group, A, B, which may be different from one another the _{same, -CH 2 CH 2 -, -} CH 2 CH (C
A hydrocarbon group selected from the group consisting of H ₃ ) — and CH (CH ₃ ) CH ₂ —; a group represented by R ¹ — (OA) _m — and / or a group represented by R ² — (OB) _n — The total number of carbon atoms and oxygen atoms contained in the group represented is 4 or more, and m and n are each independently an integer of 0 to 4) 2. The non-aqueous solvent having a flash point of 70 ° C. or higher is at least one kind selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, and δ-valerolactone. 2. The non-aqueous electrolyte according to claim 1, which is a solvent. 3. The method according to claim 2, wherein the non-aqueous solvent having a flash point of 70 ° C. or higher is at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, and γ-butyrolactone. Non-aqueous electrolyte. 4. The chain carbonate represented by the general formula (1) may be the same as the formula (1), wherein R ¹ and R ² may be the same or different from each other, and may be a carbon atom which may have a branch. A hydrocarbon group of the formulas 1 to 4, wherein m and n are independently 0
And the sum of the number of carbon atoms and the number of oxygen atoms contained in the group represented by R ^1- (OA) _m- and / or the group represented by R ^2- (OB) _n- is 4 or more. The non-aqueous electrolytic solution according to claim 3, wherein the non-aqueous electrolytic solution is at least one compound and has a content of 0.1 to 20% by weight. 5. The non-aqueous electrolyte according to claim 4, wherein the content of the chain carbonate represented by the general formula (1) is 0.5 to 10% by weight. 6. The chain carbonate represented by the general formula (1) is methyl-n-butyl carbonate, ethyl-n
The non-aqueous electrolyte according to claim 3, wherein the non-aqueous electrolyte is at least one selected from -butyl carbonate and di-n-butyl carbonate, and the content thereof is 0.5 to 10% by weight. 7. The chain carbonate represented by the general formula (1) is di-n-butyl carbonate, and the content thereof is 0.5 to 10% by weight. Item 4. The non-aqueous electrolyte according to Item 3. 8. The method according to claim 1, wherein the lithium salt electrolyte is LiPF ₆ , L
iBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , L
iC ₄ F ₉ SO ₃ , LiC ₈ F ₁₇ SO ₃ , or a lithium salt represented by the following general formula LiOSO ₂ R ³ , LiN (SO ₂
R ⁴ ) (SO ₂ R ⁵ ), LiC (SO ₂ R ⁶ ) (SO ₂ R ⁷ ) (SO ₂ R
⁸ ), LiN (SO ₂ OR ⁹ ) (SO ₂ OR ¹⁰ ) (where R ^3-
R ¹⁰ may be the same or different and are at least one member selected from the group consisting of perfluoroalkyl groups having 1 to 6 carbon atoms, and the concentration thereof is 0.1 to 3
The non-aqueous electrolyte according to any one of claims 1 to 7, wherein the non-aqueous electrolyte is contained in the non-aqueous electrolyte at a concentration of 0.5 mol / liter, preferably 0.5 to 2 mol / liter. 9. A secondary battery comprising the non-aqueous electrolyte according to claim 1. 10. A negative electrode containing any of lithium metal, a lithium-containing alloy, and a carbon material capable of doping / dedoping lithium ions as a negative electrode active material, a composite oxide of lithium and a transition metal, a carbon material as a positive electrode active material A lithium secondary battery comprising: a positive electrode containing any of these mixtures; and the non-aqueous electrolyte according to claim 1.