JP2000058122A - Nonaqueous electrolytic solution for secondary battery and nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic solution suppressing the reducing decomposition of a solvent and giving superior charge/discharge efficiency, load characteristic and low-temperature characteristic to a battery by forming the electrolytic solution with a nonaqueous solvent containing cyclic carbonic ester and an electrolyte. SOLUTION: A nonaqueous solvent containing cyclic carbonic ester expressed by the formula is used for a nonaqueous electrolytic solution for a secondary battery, where R1 and R2 may be the same or different and indicate 1-7C alkyl group, -CH2OR5 or -CH2OCOR6, and R3 and R4 may be the same or different and indicate hydrogen atom, the 2-7C hydrocarbon group, -CH2OR5 or -CH2 OCOR6. R5 and R6 indicate 1-7C alkyl group or 2-7C hydrocarbon group of and containing unsaturated bonds. When chain carbonic ester is contained in the nonaqueous solvent, the viscosity of the nonaqueous electrolytic solution can be reduced, and the solubility of an electrolyte is further enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel non-aqueous electrolyte having excellent charge / discharge characteristics and a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte.

[0002]

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

As such a battery, there is a non-aqueous electrolyte secondary battery, a typical example of which is a lithium ion secondary battery. In such a non-aqueous electrolyte secondary battery, a carbonate having a high dielectric constant is known as a non-aqueous solvent for the non-aqueous electrolyte, and various carbonates have been proposed. As an electrolyte for such a non-aqueous electrolyte secondary battery, a mixed solvent of a high-dielectric solvent such as propylene carbonate and ethylene carbonate and a low-viscosity solvent such as diethyl carbonate is usually used in a mixture of LiBF ₄ , LiPF ₆ and LiClO _4. , LiAsF ₆ , Li
A mixture of electrolytes such as CF ₃ SO ₃ and LiSiF ₆ is used. On the other hand, research on electrodes is also being pursued with the aim of increasing the capacity of batteries, and carbon materials capable of inserting and extracting lithium are used as negative electrodes of lithium ion secondary batteries. In particular, highly crystalline carbon such as graphite has characteristics such as a flat discharge potential, and is therefore used as most negative electrodes of currently commercially available lithium ion secondary batteries.

However, when highly crystalline carbon such as graphite is used for the negative electrode, propylene carbonate which is a high dielectric constant solvent having a low freezing point as a non-aqueous solvent for a non-aqueous electrolyte,
When 1,2-butylene carbonate is used, a reductive decomposition reaction of the solvent occurs at the time of charging, and an insertion reaction of lithium ions, which is an active material, into graphite hardly progresses, so that the function of the electrolytic solution is not fulfilled. As a result, there is a problem that the charge / discharge efficiency of the first time becomes extremely poor.

[0005] Therefore, in addition to propylene carbonate as a non-aqueous solvent used in the electrolytic solution, ethylene carbonate as a high dielectric constant solvent which is solid at room temperature but hardly undergoes reductive decomposition reaction continuously is mixed. Attempts have been made to suppress the reductive decomposition reaction of the non-aqueous solvent. Furthermore, in order to improve the viscosity characteristics of the non-aqueous solvent in addition to suppressing the reductive decomposition reaction, devising a combination with a low-viscosity solvent, adding various additives, and reducing the content of propylene carbonate in the electrolytic solution. Restrictions have been proposed. As a result, the charge / discharge characteristics and low-temperature characteristics of the battery have been improved, but they have not always been satisfactory.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. Even when a highly crystalline carbon such as graphite is used for a negative electrode, reductive decomposition of a solvent is suppressed,
Aims to provide a non-aqueous electrolyte that gives the battery excellent charge / discharge efficiency, load characteristics and low-temperature characteristics,
It is an object to provide a secondary battery including the non-aqueous electrolyte.

[0007]

The non-aqueous electrolyte according to the present invention comprises a non-aqueous solvent containing a cyclic carbonate represented by the following general formula (1) and an electrolyte.

[0008]

Embedded image

In the formula (1), R ¹ and R ² may be the same or different from each other, and may have an alkyl group having 1 to 7 carbon atoms or 2 to 7 carbon atoms including an unsaturated bond. A hydrocarbon group of —CH ₂ OR ⁵ or —CH ₂ OCOR ⁶ [R ⁵ , R ⁶
Represents an alkyl group having 1 to 7 carbon atoms or a hydrocarbon group having 2 to 7 carbon atoms containing an unsaturated bond], and R ³ and R ⁴ are different from each other even if they are the same. A hydrogen atom, an alkyl group having 1 to 7 carbon atoms, a hydrocarbon group having 2 to 7 carbon atoms containing an unsaturated bond, -CH
₂ OR ⁵ or —CH ₂ OCOR ⁶ [R ⁵ and R ^{6 each} represent an alkyl group having 1 to 7 carbon atoms or a hydrocarbon group having 2 to 7 carbon atoms including an unsaturated bond] .

The cyclic carbonate represented by the general formula (1) has an alkyl group having 1 to 7 carbon atoms in R ¹ and R ² , and hydrogen or carbon atoms in R ³ and R ^4. It preferably has 1 to 7 alkyl groups.

The cyclic carbonate represented by the general formula (1) has an alkyl group having 1 to 4 carbon atoms at R ¹ and R ² , and at least one of R ³ and R ⁴ has hydrogen. Is particularly preferable.

Furthermore, the cyclic carbonate represented by the above general formula (1) is most preferably a compound having a methyl group or an ethyl group at R ¹ and R ² and having hydrogen at R ³ and R ⁴ .
The present invention also provides a non-aqueous electrolyte, wherein the non-aqueous solvent further contains a carbonate represented by the following general formula (2).

[0013]

Embedded image

In the formula, R ⁵ is a hydrogen atom or a group having 1 to 3 carbon atoms.
R ⁶ represents an alkyl group having 1 to 3 carbon atoms. Further, the present invention provides a non-aqueous electrolyte in which the electrolyte contained in these non-aqueous electrolytes is a lithium salt.

Furthermore, the present invention provides 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, and a lithium and transition metal material as a positive electrode active material. A non-aqueous electrolyte secondary battery comprising: a positive electrode containing any of a composite oxide, a carbon material, or a mixture thereof; and the above-mentioned non-aqueous electrolyte as an electrolyte.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The non-aqueous electrolyte according to the present invention and a non-aqueous electrolyte secondary battery using this non-aqueous electrolyte will be specifically described below.

The non-aqueous electrolyte according to the present invention comprises a non-aqueous solvent containing a specific cyclic carbonate and an electrolyte. Cyclic Carbonate As the cyclic carbonate used in the present invention, those represented by the following general formula (1) are used.

[0018]

Embedded image

In the formula (1), R ¹ and R ² may be the same or different from each other, and may have an alkyl group having 1 to 7 carbon atoms or 2 to 7 carbon atoms including an unsaturated bond. A hydrocarbon group of —CH ₂ OR ⁵ or —CH ₂ OCOR ⁶ [R ⁵ , R ⁶
Represents an alkyl group having 1 to 7 carbon atoms or a hydrocarbon group having 2 to 7 carbon atoms containing an unsaturated bond], and R ³ and R ⁴ are different from each other even if they are the same. A hydrogen atom, an alkyl group having 1 to 7 carbon atoms, a hydrocarbon group having 2 to 7 carbon atoms containing an unsaturated bond, -CH
₂ OR ⁵ or —CH ₂ OCOR ⁶ [R ⁵ and R ^{6 each} represent an alkyl group having 1 to 7 carbon atoms or a hydrocarbon group having 2 to 7 carbon atoms including an unsaturated bond] .

In the present invention, the above-mentioned general formula (1)
R ¹ and R ² each have an alkyl group having 1 to 7 carbon atoms, and R ³ and R ^{4 each} have a hydrogen atom or an alkyl group having 1 to 7 carbon atoms. Is preferred.

The cyclic carbonate represented by the general formula (1) has an alkyl group having 1 to 4 carbon atoms at R ¹ and R ² , and at least one of R ³ and R ⁴ has hydrogen. Is particularly preferable.

Further, the cyclic carbonate represented by the above general formula (1) most preferably has a methyl group or an ethyl group at R ¹ and R ² and has hydrogen at R ³ and R ⁴ .
Examples of the cyclic carbonate represented by the formula (1) include 4,4-dimethyl, 5-methyleneethylene carbonate,
-Methyl, 4-ethyl, 5-methyleneethylene carbonate, 4
-Methyl, 4-propyl, 5-methyleneethylene carbonate, 4-methyl, 4-butyl, 5-methyleneethylene carbonate, 4,4-diethyl, 5-methyleneethylene carbonate, 4
-Ethyl, 4-propyl, 5-methyleneethylene carbonate, 4-ethyl, 4-butyl, 5-methyleneethylene carbonate, 4,4-dipropyl, 5-methyleneethylene carbonate, 4-propyl, 4-butyl, 5-methylene Ethylene carbonate, 4,4-dibutyl, 5-methylene ethylene carbonate, 4,4-dimethyl, 5-ethylidene ethylene carbonate, 4-methyl, 4-ethyl, 5-ethylidene ethylene carbonate, 4-methyl, 4-propyl, 5 -Ethylidene ethylene carbonate, 4-methyl, 4-butyl, 5-ethylidene ethylene carbonate, 4,4-diethyl, 5-ethylidene ethylene carbonate, 4-ethyl, 4-propyl, 5-ethylidene ethylene carbonate, 4-ethyl, 4 -Butyl, 5-ethylidene ethylene carbonate, 4,4-dipropyl, 5-ethylidene ethylene carbonate, 4-propyl, 4-butyl, 5-ethylidene ethylene carbonate G, 4,4-dibutyl, 5-ethylidene ethylene carbonate, 4-methyl, 4-vinyl, 5-methylene ethylene carbonate, 4-methyl, 4-allyl, 5-methylene ethylene carbonate, 4-methyl, 4-methoxymethyl , 5-methyleneethylene carbonate, 4-methyl, 4-acryloxymethyl, 5-methyleneethylene carbonate, 4-methyl, 4-allyloxymethyl, 5-methyleneethylene carbonate, and the like.

Particularly preferred compounds are 4,4-dimethyl, 5-methyleneethylene carbonate (the following formula (3)) and 4-methyl, 4-ethyl, 5-methyleneethylene carbonate (the following formula (4)). is there.

Embedded image

Such a cyclic carbonate has the effect of suppressing the reduction reaction of the non-aqueous solvent during charging and improving the charge / discharge efficiency. Non-aqueous solvent In the non-aqueous electrolyte for a secondary battery according to the present invention, a non-aqueous solvent containing a cyclic carbonate represented by the above formula (1) is used.

The cyclic carbonate represented by the above formula (1) is preferably used as a mixture with another non-aqueous solvent. The cyclic carbonate represented by the above formula (1) is at least 0.001% by weight, preferably 0.01% by weight, based on the whole non-aqueous solvent.
It is desirable that it be contained in an amount of from 50 to 50% by weight, more preferably from 0.1 to 20% by weight. When the non-aqueous solvent contains the cyclic carbonate represented by the general formula (1) in such an amount, the reductive decomposition reaction of the solvent that occurs during charging can be kept low.

The non-aqueous solvent in the present invention is represented by the above formula (1)
And a cyclic carbonate and / or a linear carbonate represented by the following general formula (2).

[0027]

Embedded image

In the formula, R ⁵ is a hydrogen atom or a group having 1 to 3 carbon atoms.
R ⁶ represents an alkyl group having 1 to 3 carbon atoms. Examples of the cyclic carbonate represented by the formula (2) include propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and the like. Is mentioned. Among them, propylene carbonate having a low viscosity and a low freezing point is preferably used. Also,
These cyclic carbonates may be used as a mixture of two or more kinds.

Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate and the like. These chain carbonates may be used as a mixture of two or more.

When such a chain carbonate is contained in a non-aqueous solvent, the viscosity of the non-aqueous electrolyte can be reduced, the solubility of the electrolyte can be further increased, and the electric conductivity at normal temperature or low temperature can be improved. It is possible to obtain an electrolytic solution having excellent properties.
Therefore, the charge / discharge efficiency and load characteristics of the battery can be improved.

Therefore, preferred non-aqueous solvents of the present invention include a cyclic carbonate represented by the general formula (1) and a cyclic carbonate represented by the general formula (2) and / or the chain carbonate described above. It is a thing. However, this does not exclude the presence of other compounds described below. As described above, the cyclic carbonate represented by the above formula (1) is required to improve the battery characteristics, for example, the charge / discharge efficiency of the battery and the load characteristics.
It is desirable that it be contained in an amount of 1% by weight or more, preferably 0.01 to 50% by weight, more preferably 0.1 to 20% by weight. The remaining amount is preferably occupied by the cyclic carbonate represented by the general formula (2) and / or the chain carbonate, and among them, the cyclic carbonate represented by the general formula (2) or the general formula (2) More preferably, the cyclic carbonate represented by 2) and the chain carbonate are occupied. That is, the total amount of the cyclic carbonate represented by the general formula (2) and the chain carbonate is:
99.999% by weight or less of the total amount of the non-aqueous solvent, preferably 5%
0-99.99% by weight, more preferably 80-9%
Desirably, it is 9.9% by weight. In the nonaqueous solvent, the quantitative ratio of the cyclic carbonate represented by the general formula (2) to the chain carbonate (cyclic carbonate: chain carbonate represented by the general formula (2)) is 0: 100-100: 0,
Preferably from 5:95 to 95: 5, particularly preferably from 20:
80 to 85:15 (all by weight).

Further, in the present invention, as the compound present in addition to the above-mentioned cyclic carbonate and chain carbonate, it is possible to use a solvent which is generally widely used as a non-aqueous solvent for batteries. Specifically, cyclic esters having a double bond in the ring, such as vinylene carbonate, and linear esters such as methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, methyl propionate, and the like. , Phosphate esters such as trimethyl phosphate, chain ethers such as dimethoxyethane, cyclic ethers such as tetrahydrofuran, amides such as dimethylformamide,
Chain carbamates such as methyl-N, N-dimethyl carbamate; cyclic esters such as γ-butyrolactone;
Cyclic sulfones such as sulfolane; cyclic carbamates such as N-methyloxazolidinone; cyclic amides such as N-methylpyrrolidone; and cyclic ureas such as N, N-dimethylimidazolidone.

Other compounds which may be present in addition to the above-mentioned cyclic carbonate and chain carbonate include a cyclic carbonate represented by the general formula (1), a cyclic carbonate represented by the general formula (2) and a chain 20 to the total amount of
Desirably, it is used in an amount of not more than% by weight.

Electrolyte The electrolyte used in the present invention is not particularly limited as long as it is generally used as an electrolyte for a non-aqueous electrolyte.

Specifically, LiPF ₆ , LiBF ₄ , LiCl
_{O 4, LiAsF 6, LiOSO 2} R 1 1, LiN (SO 2 R 1 2)
^{_{(SO 2 R 1 3),}} LiC (SO 2 R 1 4) (SO 2 R 1 5) (SO
^{_{2 R 1 6), LiN (}} SO 2 OR 1 7) (SO 2 OR 1 8) [ In the formula, R ^1
1 to R ^{1 8} may be the being the same or different, is a perfluoroalkyl group having 1 to 6 carbon atoms,
Lithium salts such as LiSiF ₆ , LiC ₄ F ₉ SO ₃ and LiC ₈ F ₁₇ SO ₃ are preferably used. These lithium salts may be used alone or as a mixture of two or more.

Of these, in particular, LiPF₆, LiB
F_Four, LiOSO_TwoR^{1 1}, LiN (SO_TwoR^{1 Two}) (SO_TwoR^{1 Three}),
LiC (SO_TwoR^{1 Four}) (SO_TwoR^{1 Five}) (SO_TwoR^{1 6}), LiN (SO
_TwoOR^{1 7}) (SO_TwoOR^{1 8}) Is preferred.

In particular, such electrolytes are usually 0.1 to
It is desirable that it is contained in the non-aqueous electrolyte at a concentration of 3 mol / l, preferably 0.5 to 2 mol / l.
The non-aqueous electrolyte for a secondary battery according to the present invention as described above is suitable as a non-aqueous electrolyte for a lithium ion secondary battery. The non-aqueous electrolyte of the present invention can also be used as a non-aqueous electrolyte for a primary battery.

Non-Aqueous Electrolyte Secondary Battery The non-aqueous electrolyte secondary battery according to the present invention comprises a negative electrode, a positive electrode,
It comprises the non-aqueous electrolyte described above. Usually, a separator is used in addition to this.

As a preferred non-aqueous electrolyte secondary battery of the present invention, a negative electrode containing any of lithium metal, a lithium-containing alloy, and a carbon material capable of doping and dedoping lithium ions as a negative electrode active material; A non-aqueous electrolyte secondary battery comprising a positive electrode containing any of a composite oxide of lithium and a transition metal, a carbon material, or a mixture thereof, a separator, and the non-aqueous electrolyte described above. it can.

Such a non-aqueous electrolyte secondary battery can be applied to, for example, a cylindrical non-aqueous electrolyte secondary battery. As shown in FIG. 1, a cylindrical nonaqueous electrolyte secondary battery has a negative electrode 1 formed by applying a negative electrode active material to a negative electrode current collector 9 and a positive electrode formed by applying a positive electrode active material to a positive electrode current collector 10. And 2 are wound through a separator 3 into which a non-aqueous electrolyte is injected, and are housed in a battery can 5 with an insulating plate 4 placed above and below the wound body. A battery lid 7 is attached to the battery can 5 by caulking through a sealing gasket 6, and a negative electrode lead 1
It is electrically connected to negative electrode 1 or positive electrode 2 via 1 and positive electrode lead 12, and is configured to function as the negative electrode or positive electrode of the battery. The separator is a porous film, and a microporous polymer film is preferably used, and among them, a porous polyolefin film is preferable. As the porous polyolefin film, a porous polyethylene film, a porous polypropylene film,
Alternatively, a multilayer film of a porous polyethylene film and polypropylene can be exemplified.

In a lithium ion secondary battery, as a means for securing the safety of the battery, a separator having a shutdown property is used for the lithium ion secondary battery,
Devices such as elements, protection circuits, current cutoff mechanisms, safety valves, etc. have been proposed or adopted.

In this battery, the positive electrode lead 12 may be electrically connected to the battery lid 7 via the current interrupting thin plate 8. In such a battery, when the pressure inside the battery rises, the current interrupting thin plate 8 is pushed up and deformed, and the positive electrode lead 12 is cut leaving a portion welded to the thin plate 8, thereby interrupting the current. ing.

As the negative electrode active material constituting such a negative electrode 1, any of lithium metal, a lithium alloy, and a carbon material capable of doping and dedoping lithium ions can be used. It is preferable to use a carbon material which can dove / de-do lithium ions. Such a carbon material may be graphite or amorphous carbon, and any carbon material such as activated carbon, carbon fiber, carbon black, and mesocarbon microbeads is used.

In the present invention, as the negative electrode active material, a carbon material having a (002)) plane spacing (d002) of 0.340 nm or less measured by X-ray analysis is particularly preferable, and a density of 1.70 g / cm is particularly preferable. It is desirable to use graphite having a value of ³ or more or a highly crystalline carbon material having properties close thereto, and use of such a carbon material can increase the energy density of a battery.

The positive electrode active material constituting the positive electrode 2 is Mo
Transition metal oxides and sulfides such as S ₂ , TiS ₂ , MnO ₂ , V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , LiMn ₂
A composite oxide composed of lithium and a transition metal such as O ₄ and LiNiO ₂ can be used. Among them, a composite oxide composed of lithium and a transition metal is particularly preferable. When the negative electrode is made of lithium metal or a lithium alloy, a carbon material can be used as the positive electrode. Furthermore, a mixture of a composite oxide of lithium and a transition metal and a carbon material can be used as the positive electrode.

The non-aqueous electrolyte secondary battery according to the present invention can also be applied to a coin-type non-aqueous electrolyte secondary battery as shown in FIG. In the coin-type non-aqueous electrolyte secondary battery of FIG. 2, a disc-shaped negative electrode 13, a disc-shaped positive electrode 14,
The stainless steel plate 17 is stored in the battery can 16 in a state where the negative electrode 13, the separator 15, the positive electrode 14, and the stainless steel plate 17 are stacked in this order, and the battery can (lid) 19 is swaged via the gasket 18. It is attached by that. As the negative electrode 13, the separator 15, and the positive electrode 14, the same as those described above are used. The battery can 16 and the battery can (lid) 19 are made of a material such as stainless steel that is not easily corroded by an electrolytic solution.

The non-aqueous electrolyte secondary battery according to the present invention includes the non-aqueous electrolyte described above as an electrolyte, and the shape of the battery is limited to those shown in FIGS. 1 and 2. Instead, it may be square or the like.

[0048]

The nonaqueous electrolyte of the present invention suppresses the reductive decomposition reaction of the solvent which occurs when highly crystalline carbon such as graphite is used for the negative electrode. As a result, the nonaqueous electrolyte using the nonaqueous electrolyte of the present invention is reduced. A water electrolyte secondary battery has excellent charge / discharge characteristics and excellent battery characteristics at low temperatures. Further, the non-aqueous electrolyte for a secondary battery according to the present invention is particularly suitable as a non-aqueous electrolyte for a lithium ion secondary battery.

[0049]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

[0050]

Example 1 <Preparation of non-aqueous electrolyte> After mixing propylene carbonate (PC) and diethyl carbonate (DEC) (mixing weight ratio PC: DEC = 55: 45), 4,4-
Dimethyl, 5-methyleneethylene carbonate (DMM
C) with respect to 99 parts by weight of a mixed solvent of PC and DEC,
Part by weight (1% by weight) was added to prepare a mixed solvent. Next, 15.2 g (100 mmol) of LiPF ₆ was dissolved in the mixed solvent to prepare a non-aqueous electrolyte solution so that the electrolyte concentration was 1.0 mol / l. .

<Preparation of Negative Electrode> The negative electrode 13 was prepared as follows. 90 parts by weight of carbon powder of mesocarbon microbeads (MCMB, sintering temperature 2800 ° C) manufactured by Osaka Gas Co., Ltd. and 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder are mixed, and N-methylpyrrolidone as a solvent is mixed. To prepare a negative electrode mixture slurry (paste).

This negative electrode mixture slurry was applied to a 20 μm-thick negative electrode current collector made of a strip-shaped copper foil, and dried to obtain a strip-shaped carbon negative electrode. The thickness of such a negative electrode mixture is 25 μm
Met. Further, after punching out this strip-shaped electrode into a disk shape having a diameter of 15 mm, compression molding was performed to obtain a negative electrode 13. <Production of Positive Electrode> The positive electrode 14 was produced as follows.

91 parts by weight of fine particles of LiCoO ₂ (product name: HLC-21, average particle size 8 μm) manufactured by Honjo Chemical Co., Ltd., 6 parts by weight of graphite as a conductive material, and 3 parts by weight of polyvinylidene fluoride as a binder Was mixed to prepare a positive electrode mixture, and dispersed in N-methylpyrrolidone to obtain a positive electrode mixture slurry.

This slurry was applied to a 20-μm-thick aluminum foil positive electrode current collector, dried, and compression-molded to obtain a belt-shaped positive electrode. The thickness of such a positive electrode mixture is 40
μm. Further, this strip-shaped electrode was punched out into a disk shape having a diameter of 15 mm to obtain a positive electrode 14. <Preparation of battery> Disc-shaped negative electrode 13 thus obtained,
Disc-shaped positive electrode 14 and separator 15 (thickness 25 μm, diameter
As shown in FIG. 2, a 19-mm microporous polypropylene film is laminated on a 2032 stainless steel battery can 16 in the order of the negative electrode 13, the separator 15, and the positive electrode 14. Injected. After that, the stainless steel plate 17 (thickness 2.4 mm, diameter 15.4 mm) is stored, and the battery can (lid) 19 is swaged via the polypropylene gasket 18 to maintain the airtightness in the battery. Then, a button-type nonaqueous electrolyte secondary battery having a diameter of 20 mm and a height of 3.2 mm was produced. <Measurement of Discharge Capacity> The discharge capacity of the non-aqueous electrolyte secondary battery thus obtained was measured at room temperature. In the present embodiment, the current direction in which the negative electrode is doped with Li + is charged, and the current direction in which the negative electrode is undoped is discharge. Charging was performed by a 4.1 V, 1 mA constant current, constant voltage charging method, and was terminated when the charging current became 50 μA or less. From the charge capacity and the discharge capacity in this charge / discharge cycle, the charge / discharge efficiency was calculated by the following equation. Table 1 shows the results.

[0055]

(Equation 1)

[0056]

Example 2 In Example 1, the weight ratio P of the mixed solvent was
C: DEC is 55:45, and 4-ethyl, 4-methyl, instead of 4,4-dimethyl, 5-methyleneethylene carbonate
The charge / discharge efficiency of the battery was evaluated in the same manner as in Example 1 except that 5-methyleneethylene carbonate (EMMC) was used. Table 1 shows the results.

[0057]

Example 3 In Example 1, the addition amount of 4,4-dimethyl, 5-methyleneethylene carbonate was 0.5 parts by weight (0.5% by weight) based on 99.5 parts by weight of the total of PC and DEC. ), And the charge and discharge efficiency of the battery was evaluated in the same manner as in Example 1. Table 1 shows the results.

[0058]

Example 4 Example 4 was repeated except that the amount of 4,4-dimethyl, 5-methyleneethylene carbonate was changed to 5 parts by weight (5% by weight) with respect to 95 parts by weight of the total of PC and DEC. In the same manner as in Example 1, the charge / discharge efficiency of the battery was evaluated. Table 1 shows the results.

[0059]

Comparative Example 1 A battery was evaluated for charge and discharge efficiency in the same manner as in Example 1 except that 4,4-dimethyl, 5-methyleneethylene carbonate was not added. Table 1 shows the results.

[0060]

[Table 1]

[0061]

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a cylindrical battery showing one embodiment of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a schematic sectional view of a coin battery showing one embodiment of the non-aqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

 1,13 ・ ・ ・ ・ Negative electrode 2,14 ・ ・ ・ ・ Positive electrode 3,15 ・ ・ ・ ・ ・ ・ Separator 4,11 ・ ・ ・ ・ Insulating plate 5,16 ・ ・ ・ ・ Battery can 6 ・ ・ ・ ・ Sealing gasket 7 ··· Battery cover 8 ··· Thin plate for interrupting current 9 ··· Negative electrode current collector 10 ··· Positive electrode current collector 11 ··· Negative electrode lead 12 ···・ ・ Stainless steel plate 18 ・ ・ ・ ・ Gasket 19 ・ ・ ・ ・ Battery can (lid)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoko Mita 580-32, Takuji, Nagaura-shi, Sodegaura-shi, Chiba Inside Mitsui Chemicals, Inc. 32 Mitsui Chemicals Co., Ltd. F-term (reference) 5H029 AJ02 AJ07 AK02 AK03 AK05 AL06 AL07 AL08 AL12 AM02 AM03 AM04 AM05 AM07 DJ04 EJ12 HJ02 HJ13

Claims (11)

[Claims] 1. A non-aqueous electrolyte comprising a non-aqueous solvent containing a cyclic carbonate represented by the following general formula (1) and an electrolyte. Embedded image (In formula (1), R ¹ and R ² may be the same or different from each other, and may be an alkyl group having 1 to 7 carbon atoms or a carbon atom having 2 to 7 carbon atoms including an unsaturated bond. Hydrogen group, -CH
₂ OR ⁵ or —CH ₂ OCOR ⁶ [R ⁵ and R ^{6 each} represent an alkyl group having 1 to 7 carbon atoms or a hydrocarbon group having 2 to 7 carbon atoms including an unsaturated bond] And R ³
And R ⁴ may be the same or different from each other, and include a hydrogen atom, an alkyl group having 1 to 7 carbon atoms, a hydrocarbon group having 2 to 7 carbon atoms including an unsaturated bond, —CH ₂ O
R ⁵ or —CH ₂ OCOR ⁶ [R ⁵ and R ^{6 each} represent an alkyl group having 1 to 7 carbon atoms or a hydrocarbon group having 2 to 7 carbon atoms including an unsaturated bond] is there. ) 2. The cyclic carbonate represented by the general formula (1) has an alkyl group having 1 to 7 carbon atoms in R ¹ and R ² , and hydrogen or carbon atom in R ³ and R ^4. 2. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte has 1 to 7 alkyl groups. 3. The cyclic carbonate represented by the general formula (1) has an alkyl group having 1 to 4 carbon atoms at R ¹ and R ² , and at least one of R ³ and R ⁴ has hydrogen. The non-aqueous electrolyte according to claim 2, comprising: 4. The cyclic carbonate represented by the general formula (1) has a methyl group or an ethyl group in R ¹ and R ² ,
The non-aqueous electrolyte according to claim 3, wherein R ³ and R ⁴ have hydrogen. 5. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous solvent further contains a cyclic carbonate represented by the following general formula (2). Embedded image (In the formula, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ⁶ represents an alkyl group having 1 to 3 carbon atoms.) 6. The non-aqueous electrolyte according to claim 1, wherein the electrolyte is a lithium salt. 7. The non-aqueous electrolyte for a secondary battery according to claim 1, wherein the non-aqueous electrolyte is an electrolyte for a lithium ion secondary battery. 8. 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 non-aqueous electrolyte secondary battery comprising: a positive electrode containing any of the materials or a mixture thereof; and the non-aqueous electrolyte according to claim 1 as an electrolyte. 9. The non-aqueous electrolyte secondary battery according to claim 8, further comprising a separator. 10. The carbon material capable of doping / dedoping lithium ions has a plane distance (d002) on the (002) plane measured by X-ray analysis of 0.340 nm or less. The non-aqueous electrolyte secondary battery according to claim 8. 11. The non-aqueous electrolyte secondary battery according to claim 8, wherein the separator is a porous polyolefin film.