JP2000243444A - Nonaqueous electrolytic solution and secondary battery using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution excellent in charge/ discharge characteristics, load characteristics, and low-temperature characteristics, and a secondary battery using the same. SOLUTION: This nonaqueous electrolytic solution is composed of a nonaqueous solvent containing a compound including a cyanoethyl group expressed by a general expression [1] and an electrolyte. The expression [1] is RO(R'O)nCH2CH2CN. In the expression [1], R is hydrogen, a hydrocarbon group of 1C to 10C, or a cyanoethyl group, R' is an alkylene group of 1C to 4C, and (n) is an integer of 0 to 30.

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 charge / discharge characteristics and a secondary battery using the same. More specifically, the present invention relates to a non-aqueous electrolyte suitable for a lithium secondary battery containing a compound containing a cyanoethyl group, and a secondary battery using the same.

[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. Carbonate compounds having a high dielectric constant are known as non-aqueous solvents used for such a purpose, and the use of various carbonate compounds has been proposed. As an electrolytic solution, LiBF ₄ , LiPF ₆ , LiPF ₆ , a mixed solvent of the high dielectric constant carbonate compound solvent such as propylene carbonate and ethylene carbonate, and a low viscosity solvent such as diethyl carbonate.
A solution in which an electrolyte such as LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , or Li ₂ SiF ₆ is mixed is used.

[0004] On the other hand, research on electrodes has been promoted with the aim of increasing the capacity of batteries, and carbon materials capable of occluding and releasing 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 or 1,1, which is a high dielectric constant solvent having a low freezing point, is used as a non-aqueous solvent for the electrolytic solution.
When 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, the first charge / discharge efficiency is extremely reduced.

[0006] Therefore, as a non-aqueous solvent having a high dielectric constant, which is used in the electrolytic solution, ethylene carbonate, which is solid at room temperature but hardly undergoes a reductive decomposition reaction, is mixed with propylene carbonate to form a non-aqueous solvent. Attempts have been made to suppress the reductive decomposition reaction of the 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. These measures have improved the charge / discharge characteristics and low-temperature characteristics of the battery, but at present there is a demand for a higher-performance electrolytic solution.

[0007]

SUMMARY OF THE INVENTION In order to meet the above demand, the present invention suppresses the reductive decomposition reaction of a solvent even when a highly crystalline carbon such as graphite is used for a negative electrode, and is excellent in batteries. It is an object of the present invention to provide a non-aqueous electrolyte that provides improved charge / discharge efficiency, load characteristics and low-temperature characteristics. Another object is to provide a secondary battery including the non-aqueous electrolyte.

[0008]

Means for Solving the Problems The non-aqueous electrolyte according to the present invention relates to a non-aqueous electrolyte comprising a non-aqueous solvent containing a compound containing a cyanoethyl group represented by the following general formula [1] and an electrolyte. . RO (R'O) _n CH ₂ CH ₂ CN [1]

(In the formula [1], R is hydrogen and has 1 to 10 carbon atoms.
Wherein R 'is an alkylene group having 1 to 4 carbon atoms, and n is an integer of 0 to 30. )

Further, the non-aqueous solvent comprises a compound having a cyanoethyl group represented by the general formula [1] and a cyclic carbonate and / or a chain represented by the following general formula [2a] or [2b]. And a non-aqueous electrolyte solution comprising a non-aqueous electrolyte.

Embedded image (In the formula [2a] or [2b], R1 and R2 represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R1 and R2 may be the same or different.)

Further, if these non-aqueous electrolytes are non-aqueous electrolytes in which a lithium salt as an electrolyte is dissolved, they can be effectively used as electrolytes for primary batteries or secondary batteries.

The present invention also relates to a method for doping lithium metal, a lithium-containing alloy, and lithium ion as a negative electrode active material.
A negative electrode including any of the undoped carbon materials, a positive electrode including any of a composite oxide of lithium and a transition metal as the positive electrode active material, a carbon material or a mixture thereof, and the nonaqueous electrolyte Related to secondary batteries.

[0013]

Next, the non-aqueous electrolyte according to the present invention and a non-aqueous electrolyte secondary battery using this non-aqueous electrolyte will be described in detail. The non-aqueous electrolyte according to the present invention comprises a non-aqueous solvent containing a compound containing a cyanoethyl group and an electrolyte, and each will be described in detail.

Compound Containing a Cyanoethyl Group As the compound containing a cyanoethyl group to be contained in the non-aqueous solvent in the present invention, a compound represented by the following general formula [1] is used. In the present invention, a cyanoethyl group is defined as -C
H ₂ CH ₂ CN is shown. RO (R′O) _n CH ₂ CH ₂ CN [1] (In the formula [1], R is hydrogen, a hydrocarbon group having 1 to 10 carbon atoms or a cyanoethyl group, and n is 0 to 30.
Is an integer. )

R is specifically hydrogen, a methyl group,
Ethyl group, vinyl group, propyl group, isopropyl group, 1-
Propenyl group, 2-propenyl group, methacryl group, 1-propynyl group, 2-propynyl group, butyl group, isobutyl group,
sec-butyl group, t-butyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 2-methyl-2-propenyl group, 1-methylenepropyl group, 1-methyl-2-propenyl group, 1 , 2-dimethylvinyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group, pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-methyl-2-methylpropyl group, Examples thereof include a 2,2-dimethylpropyl group, a linear or branched alkyl group having 1 to 10 carbon atoms such as a hexyl group, an octyl group, a nonyl group, and a decyl group, and a cyanoethyl group.

R 'is an alkylene group having 1 to 4 carbon atoms, and specific examples include a methylene group, an ethylene group, a propylene group and a butylene group.

As a specific compound represented by the general formula [1], there can be mentioned a compound represented by the following formula. CH ₃ OCH ₂ CH ₂ CN NCCH ₂ CH ₂ OCH ₂ CH ₂ CN CH ₃ CH ₂ OCH ₂ CH ₂ CN CH ₃ OCH ₂ CH ₂ OCH ₂ CH ₂ CN NCCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ CN

Among these, particularly preferred compounds are
Is CH_ThreeOCH_TwoCH_TwoOCH_TwoCH _TwoCN. this
Containing a cyanoethyl group represented by the above general formula [1].
Compounds undergo reductive decomposition of non-aqueous solvents during charging.
And has the effect of improving charge and discharge efficiency.

Non- Aqueous Solvent In the non-aqueous electrolyte according to the present invention, a non-aqueous solvent containing a compound having a cyanoethyl group represented by the above general formula [1] is used. The compound containing a cyanoethyl group can be used as an additive to a commonly used non-aqueous solvent or as a solvent constituting a non-aqueous solvent. The compound containing a cyanoethyl group is 0.00% of the total amount of the nonaqueous solvent (the total amount of the compound containing a cyanoethyl group and the nonaqueous solvent).
1% by weight or more, preferably 0.01 to 99.5% by weight,
More preferably, it is contained in an amount of 0.01 to 70% by weight, particularly preferably 0.05 to 30% by weight. In the present invention, it is particularly desirable to use a non-aqueous solvent containing the above-mentioned compound containing a cyanoethyl group and a cyclic carbonate and / or a chain carbonate represented by the following general formula [2a] or [2b].

Examples of the non-aqueous solvent that can be used include cyclic carbonates and / or chain carbonates represented by the following general formula [2a] or [2b].

Embedded image In the formula [2a] or [2b], R1 and R2 represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R1 and R2 may be the same or different. Among them, the alkyl group is preferably an alkyl group having 1 to 3 carbon atoms, and specific examples include a methyl group, an ethyl group, and an n-propyl group.

Specific examples of the cyclic carbonate represented by the general formula [2a] or [2b] include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate and the like. In particular, propylene carbonate having a high dielectric constant, a low viscosity and a low freezing point is preferably used. These cyclic carbonates may be used as a mixture of two or more kinds.

Specific 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, it is possible to improve the charge / discharge efficiency of the battery and low-temperature characteristics such as, for example, the charge / discharge efficiency at low temperatures and the load characteristics at low temperatures.

When the cyclic carbonate and / or chain carbonate represented by the general formula [2a] or [2b] is used as the non-aqueous solvent, it contains a cyanoethyl group represented by the general formula [1]. The compound may be a non-aqueous solvent containing the compound (a compound containing a cyanoethyl group represented by the general formula [1] and a cyclic carbonate and / or a chain compound represented by the general formula [2a] or [2b]). 0.001% by weight or more, preferably 0.01 to 99.5% by weight, more preferably 0.01 to 70% by weight, particularly preferably 0.05 to 30% by weight based on the total amount with the carbonate ester).
Desirably, it is included in an amount of weight percent.

When the compound containing a cyanoethyl group represented by the above general formula [1] is contained in the entire nonaqueous solvent containing the compound at such a mixing ratio, the reductive decomposition reaction of the solvent that occurs during charging is suppressed to a low level. As a result, the charge / discharge efficiency of the battery and the low-temperature characteristics can be improved. Further, in a non-aqueous solvent, the above-mentioned general formula [2a] or [2b]
The mixing ratio of the cyclic carbonate and the chain carbonate represented by the formula is represented by weight ratio, and the ratio of the cyclic carbonate: chain carbonate is 0: 100 to 100: 0, preferably 5:95 to 95: 5, particularly preferably 20:80 to 8
5:15.

Accordingly, a preferred non-aqueous solvent according to the present invention is a compound containing a cyanoethyl group represented by the general formula [1], a cyclic carbonate represented by the general formula [2a] or [2b] and And / or contains the chain carbonate. In addition, it is also possible to further mix and use a solvent widely used as a non-aqueous solvent for batteries. Specific examples of usable solvents include chain esters such as methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate and ethyl propionate; phosphate esters such as trimethyl phosphate Linear ethers such as tetrahydrofuran; amides such as dimethylformamide; linear carbamates such as methyl-N, N-dimethylcarbamate; cyclic esters such as γ-butyrolactone; cyclic sulfones such as sulfolane; Cyclic carbamates such as -methyloxazolidinone; cyclic amides such as N-methylpyrrolidone; cyclic ureas such as N, N-dimethylimidazolidinone; 4,4-dimethyl-5-methyleneethylene carbonate, 4-methyl-4-ethyl- 5-methylene ethylene 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- Methylene ethylene carbonate, 4-ethyl-4-butyl-5-methyleneethylene carbonate, 4,4-dipropyl-5-methyleneethylene carbonate, 4-propyl-4-butyl-5-methyleneethylene 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, 4,4-dibutyl-5-ethylidene ethylene carbonate, 4-methyl-4-vinyl-5-methyleneethylene carbonate, 4-methyl-4-allyl-5-methyleneethylene carbonate, 4-methyl-4-methoxymethyl-5-methyleneethylene carbonate, 4-methyl-4-acryl Cyclic carbonates such as oxymethyl-5-methyleneethylene carbonate, 4-methyl-4-allyloxymethyl-5-methyleneethylene carbonate; 4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-
Vinylethylene carbonate derivatives such as divinylethylene carbonate; 4-vinyl-4-methylethylene carbonate, 4-vinyl-5-methylethylene carbonate,
Vinyl-4,5-dimethylethylene carbonate, 4-vinyl-
5,5-dimethylethylene carbonate, 4-vinyl-4,5,5-
Alkyl-substituted vinylethylene carbonate derivatives such as trimethylethylene carbonate; allyloxymethylethylene carbonate derivatives such as 4-allyloxymethylethylene carbonate and 4,5-diallyloxymethylethylene carbonate; 4-methyl-4-allyloxymethylethylene carbonate; Alkyl-substituted allyloxymethylethylene carbonate derivatives such as 4-methyl-5-allyloxymethylethylene carbonate; acryloxymethylethylene carbonate derivatives such as 4-acryloxymethylethylene carbonate and 4,5-acryloxymethylethylene carbonate; 4- Alkyl-substituted acryloxymethyl ethylene such as methyl-4-acryloxymethylethylene carbonate and 4-methyl-5-acryloxymethylethylene carbonate Carbonate derivatives; and the like and a compound represented by the following general formula can be exemplified. HO (CH ₂ CH ₂ O) _a H, HO ｛C
H ₂ CH (CH ₃ ) O｝ _bH , CH ₃ O (CH ₂ CH ₂ O) _c
H, CH ₃ O ｛CH ₂ CH (CH ₃ ) O｝ _d H, CH ₃ O
(CH ₂ CH ₂ O) _e CH ₃ , CH ₃ O ｛CH ₂ CH (C
H ₃ ) O｝ _f CH ₃ , C ₉ H ₁₉ PhO (CH ₂ CH ₂ O) _g
{CH (CH ₃ ) O} _h CH ₃ (Ph is a phenyl group), C
H ₃ O ｛CH ₂ CH (CH ₃ ) O｝ _i CO ｛O (CH ₃ ) C
HCH ₂ ｝ _j OCH ₃ (where a to f are from 5 to 250
And g to j are integers of 2 to 249, and 5 ≦ g + h ≦ 25.
0, 5 ≦ i + j ≦ 250. )

The non-aqueous electrolytic solution The non-aqueous electrolyte solution of the present invention is formed of a non-aqueous solvent containing a compound containing a specific cyanoethyl groups described above as the electrolyte, a compound containing a particular cyanoethyl group, for example the above-mentioned Is obtained by dissolving an electrolyte in a non-aqueous solvent containing As the electrolyte to be used, any electrolyte which is usually used as an electrolyte for a non-aqueous electrolyte can be used.

Specific examples of the electrolyte include LiPF ₆ , Li
BF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiC ₄ F
Lithium salts such as ₉ SO ₃ and LiC ₈ F ₁₇ SO ₃ are exemplified. Further, a lithium salt represented by the following general formula can also be used. 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 ) (here, R 3 to R ¹⁰ may be the same or different, and may have 1 to 6 carbon atoms.
Is a perfluoroalkyl group). These lithium salts may be used alone or as a mixture of two or more.

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 contains a non-aqueous solvent containing the above-mentioned compound containing a specific cyanoethyl group and an electrolyte as essential components, but may contain other additives if necessary. Good.

The non-aqueous electrolyte according to the present invention as described above comprises:
Not only is it suitable as a non-aqueous electrolyte for lithium ion secondary batteries, but it can also be used as a non-aqueous electrolyte for primary batteries.

The non-aqueous electrolyte secondary battery according to the secondary batteries present invention, a negative electrode, a positive electrode,
The non-aqueous electrolyte is basically configured to include,
Usually, a separator is provided between the negative electrode and the positive electrode.

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, a carbon material capable of doving / de-doping lithium ions is preferable. Such a carbon material may be graphite or amorphous carbon, and activated carbon, carbon fiber, carbon black, mesocarbon microbeads and the like are used.

As the negative electrode active material, the (002) plane spacing (d002) measured by X-ray analysis was 0.340 nm.
The following carbon materials are preferable, and the density is 1.70 g / cm ³
The graphite described above or a highly crystalline carbon material having properties similar thereto is desirable. When such a carbon material is used, the energy density of the battery can be increased.

As the positive electrode active material constituting the positive electrode, Mo is used.
Transition metal oxides or 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 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 a positive electrode,
A mixture of a composite oxide of lithium and a transition metal and a carbon material can also be used.

The separator is a porous membrane, 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 severator in 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.

[0041]

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.

[0042]

Example 1 <Preparation of non-aqueous electrolyte> Propylene carbonate (PC) and diethyl carbonate (DEC) were
After mixing at a ratio of PC: DEC = 55: 45 (weight ratio), bis (2-cyanoethyl) ether (2CE-E) represented by the following formula was added to 99 parts by weight of the mixed solvent.
A non-aqueous solvent was prepared so that the amount of 2CE-E was 1% by weight based on the total amount of the non-aqueous solvent (the total amount of PC, DEC and 2CE-E). Next, the electrolyte, LiPF
₆ was dissolved in a non-aqueous solvent to prepare a non-aqueous electrolyte so that the electrolyte concentration was 1.0 mol / liter. NCCH ₂ CH ₂ OCH ₂ CH ₂ CN

<Preparation of Negative Electrode> Mesocarbon microbeads (trade name: MCMB6-28, d, manufactured by Osaka Gas Co., Ltd.)
002 = 0.337 nm, 90 parts by weight of carbon powder having a density of 2.17 g / cm ³ ) and 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder were mixed, and N-
The paste was dispersed in methylpyrrolidone to prepare a paste-like negative electrode mixture slurry. Next, this negative electrode mixture slurry was applied to a negative electrode current collector made of a 20-μm-thick strip-shaped copper foil, and dried to obtain a strip-shaped carbon negative electrode. The thickness of the negative electrode mixture after drying is 2
It was 5 μm. Furthermore, this strip electrode is 15 mm in diameter.
, And compression molded to form a negative electrode.

<Preparation of Positive Electrode> L manufactured by Honjo Chemical Co., Ltd.
iCoO ₂ (product name: HLC-21, average particle size 8 μm)
91 parts by weight of fine particles, 6 parts by weight of graphite as a conductive material, and polyvinylidene fluoride (PVD) as a binder
F) was mixed with 3 parts by weight 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 the positive electrode mixture after drying was 40 μm.
Thereafter, the strip-shaped electrode was punched into a disk having a diameter of 15 mm to obtain a positive electrode.

<Preparation of Battery> A disk-shaped negative electrode and a disk-shaped positive electrode thus obtained, and a separator made of a microporous polypropylene film having a thickness of 25 μm and a diameter of 19 mm were prepared. After each of the negative electrode, the separator, and the positive electrode were laminated in the order of a 2032-sized stainless steel battery can, the nonaqueous electrolyte was injected into the separator.
Then, a stainless steel plate (2.4 m thick) was placed in the battery can.
m, diameter 15.4 mm), and the battery can (lid) was caulked via a gasket made of polypropylene.
As a result, the airtightness in the battery can be maintained, the diameter is 20 mm,
A button-type nonaqueous electrolyte secondary battery having a height of 3.2 mm was obtained.

<Measurement of Discharge Capacity> The discharge capacity of the secondary battery thus obtained was measured at room temperature by the following method.
In this example, the current direction in which the negative electrode was doped with Li ions was defined as charging, and the current direction in which undoping was performed was defined as discharging. 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. The discharge was performed at a constant current of 1 mA, and ended when the voltage reached 2.7 V. From the charge capacity and the discharge capacity in this charge / discharge cycle, the charge / discharge efficiency was calculated by the following equation, and the results are shown in Table 1. Charge / discharge efficiency (%) = {discharge capacity (mAh / g)} / {charge capacity (mAh / g)} × 100

[0047]

Example 2 In the same manner as in Example 1, except that bis (2-cyanoethoxy) ethane (2CE-EG) represented by the following formula was used instead of bis (2-cyanoethyl) ether. A non-aqueous electrolyte solution was prepared and a battery was prepared, and the charge and discharge efficiency of the battery was evaluated in the same manner as in Example 1. The results are shown in Table 1. NCCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ CN

[0048]

Example 3 In Example 1, instead of bis (2-cyanoethyl) ether, methyl-2- represented by the following formula was used.
A non-aqueous electrolyte solution was prepared and a battery was prepared in the same manner as in Example 1 except that cyanoethyl ether (1CE-MOH) was used, and the charge and discharge efficiency of the battery was evaluated in the same manner as in Example 1. The results are shown in Table 1. CH ₃ OCH ₂ CH ₂ CN

[0049]

Example 4 In Example 1, instead of bis (2-cyanoethyl) ether, ethyl-2- represented by the following formula was used.
A non-aqueous electrolyte solution was prepared and a battery was prepared in the same manner as in Example 1 except that cyanoethyl ether (1CE-EOH) was used, and the charge and discharge efficiency of the battery was evaluated in the same manner as in Example 1. The results are shown in Table 1. CH ₃ CH ₂ OCH ₂ CH ₂ CN

[0050]

Example 5 In Example 1, methoxy-2 represented by the following formula was used instead of bis (2-cyanoethyl) ether.
Preparation of a non-aqueous electrolyte and fabrication of a battery were performed in the same manner as in Example 1 except that -cyanoethoxyethane (1CE-MC) was used, and the charge / discharge efficiency of the battery was evaluated in the same manner as in Example 1. . The results are shown in Table 1. CH ₃ OCH ₂ CH ₂ OCH ₂ CH ₂ CN

[0051]

Comparative Example 1 A non-aqueous electrolyte solution and a battery were prepared in the same manner as in Example 1 except that bis (2-cyanoethyl) ether was not added. Similarly, the charge / discharge efficiency of the battery was evaluated. The results are shown in Table 1.

[0052]

[Table 1]

[0053]

The non-aqueous electrolyte of the present invention can suppress 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, a secondary battery using this non-aqueous electrolyte has excellent charge / discharge characteristics, load characteristics, and low-temperature battery characteristics. Therefore, this non-aqueous electrolyte is particularly suitable as a non-aqueous electrolyte for a lithium ion secondary battery.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H003 AA01 BB01 BB02 BB05 BC06 BD00 5H029 AJ02 AK02 AK03 AL06 AL07 AL08 AL12 AM02 AM07 BJ03 DJ09 EJ12 HJ01 HJ13

Claims (10)

[Claims] 1. A non-aqueous electrolyte comprising a non-aqueous solvent containing a compound containing a cyanoethyl group represented by the general formula [1] and an electrolyte. RO (R′O) _n CH ₂ CH ₂ CN [1] (In the formula [1], R is hydrogen, a hydrocarbon group having 1 to 10 carbon atoms or a cyanoethyl group, and R ′ is a group having 1 to 4 carbon atoms. An alkylene group, and n is an integer of 0 to 30) 2. The non-aqueous electrolyte according to claim 1, wherein the compound represented by the general formula [1] is any compound represented by the following chemical formula. CH ₃ OCH ₂ CH ₂ CN NCCH ₂ CH ₂ OCH ₂ CH ₂ CN CH ₃ CH ₂ OCH ₂ CH ₂ CN CH ₃ OCH ₂ CH ₂ OCH ₂ CH ₂ CN NCCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ CN 3. The non-aqueous solvent comprises a cyanoethyl derivative represented by the general formula [1] and a cyclic carbonate and / or a chain carbonate represented by the general formula [2a] or [2b]. The non-aqueous electrolyte solution according to claim 1, comprising: Embedded image (In the formula [2a] or [2b], R1 and R2 represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R1 and R2 may be the same or different.) 4. The non-aqueous electrolyte according to claim 3, wherein the cyclic carbonate represented by the general formula [2a] or [2b] is propylene carbonate or butylene carbonate. 5. The non-aqueous electrolyte according to claim 3, wherein the chain carbonate is one of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. 6. The non-aqueous solvent contains at least 0.001% by weight of a cyanoethyl derivative represented by the general formula [1].
The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte is contained. 7. The non-aqueous electrolyte according to claim 1, wherein the electrolyte is a lithium salt. 8. A secondary battery comprising the non-aqueous electrolyte according to claim 1. 9. 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 as a positive electrode active material, carbon A lithium ion secondary battery comprising: a positive electrode containing any of the materials or a mixture thereof; and the non-aqueous electrolyte according to claim 1. 10. The carbon material capable of doping / dedoping lithium ions was measured by X-ray analysis (00
2) The plane distance (d002) on the plane is 0.340.
10. The lithium ion secondary battery according to claim 9, wherein the thickness is not more than nm.