JP2001057237A - Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery with superior charging and discharging efficiency, load characteristic and low temperature characteristic by using a non-aqueous electrolytic solution composed of a non-aqueous solvent including a compound having (metallic element, P or B)-O-Si bond, and an electrolyte. SOLUTION: A non-aqueous solvent is preferably prepared by adding 0.1-15 wt.% of a compound having silyloxy group represented by a formula I (M is metallic element, P or B, R1 is 1-11C alkyloxy group or silyloxy group, R2-R4 are each 1-11C alkyl group, alkenyl group, aryl group or alkyloxy group, in is the number (oxidation number of M-1) of R1 bonded to M to the total non- aqueous solvent, and mixing the same with at least one kind of cyclic carbonic ester and/or chained carbonic ester represented by a formula II and a formula III (R5-R8 are each H or 1-6C alkyl group). A lithium ion secondary battery consists of non-aqueous electrolytic solution composed of lithium salt and the non-aqueous solvent, a negative electrode active material such as a carbon material or the like capable of doping and depoding a lithium ion, and a positive electrode active material such as transition metal or the like.

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, (metal element, phosphorus or boron)-(oxygen)-
(Si) bond (hereinafter referred to as (metal element, P or B)-(0)
The present invention relates to a non-aqueous electrolyte suitable for a lithium secondary battery containing a non-aqueous solvent containing a compound having-(Si)) and an electrolyte, 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 1,2-butylene carbonate which is a high dielectric constant solvent having a low freezing point is used as a non-aqueous solvent for an electrolyte for a lithium secondary battery. When used, the reductive decomposition reaction of the solvent occurs during charging, and the insertion reaction of lithium, which is an active material, into graphite hardly progresses, and the function of the electrolytic solution is reduced. As a result, the initial charge / discharge efficiency is extremely low. To decline.

For this reason, as a non-aqueous solvent having a high dielectric constant used as an electrolyte, ethylene carbonate, which is solid at room temperature but hardly undergoes reductive decomposition reaction continuously, 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.However, furthermore, for example, when the high-temperature storage and charge-discharge cycles are repeated, the battery life caused by minute reductive decomposition reaction is reduced. There is a need for an electrolyte solution that can be improved and further improved low-temperature characteristics.

[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, thereby shortening the battery life. It is an object of the present invention to provide a non-aqueous electrolyte for a lithium secondary battery that improves the charge / discharge efficiency, load characteristics, and low-temperature characteristics of the battery. Another object of the present invention is to provide a lithium secondary battery including the non-aqueous electrolyte.

[0008]

Means for Solving the Problems The present invention relates to (metal elements,
A non-aqueous electrolyte for a lithium secondary battery comprising a non-aqueous solvent containing a compound having a (P or B)-(0)-(Si) bond and an electrolyte, and a lithium secondary battery using the same. The following is the invention. (1) A non-aqueous electrolyte for a lithium secondary battery, comprising a non-aqueous solvent containing a compound represented by the general formula [1] and an electrolyte.

Embedded image (Here, M represents a metal element, phosphorus or boron.
R ¹ is an alkyloxy group having 1 to 11 carbon atoms, or
Represents a silyloxy group, and when n is 2 or more, R ¹ may be the same or different. R ² , R ³ and R ⁴ may be the same or different and represent an alkyl group, alkenyl group, aryl group or alkyloxy group having 1 to 11 carbon atoms. n represents the number of R ¹ bonded to M, and is the oxidation number of M−1. (2) In the compound represented by the general formula [1], R
¹ is a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a phenoxy group, or a trimethylsilyloxy group, and R ² , R ³ , and R ⁴ are a methyl group, an ethyl group,
Methoxy, ethoxy, phenyl, phenoxy,
The non-aqueous electrolyte according to (1), which is any one of a vinyl group. (3) The non-aqueous solvent is a compound represented by the general formula [1], at least one of cyclic carbonates represented by the general formula [2a] or [2b] and / or chain carbonic acid 3. The non-aqueous electrolyte according to claim 1, further comprising an ester.

Embedded image (In the formula [2a] or [2b], R ^{5 to} R ⁸ may be the same or different from each other and are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.) (4) (3) The cyclic carbonate represented by the general formula [2a] or [2b] is any one of ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate.
Non-aqueous electrolyte. (5) The non-aqueous electrolyte according to (4), wherein the chain carbonate is any of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. (6) The compound according to (1) to (5), wherein the compound represented by the general formula [1] is contained in an amount of 0.1 to 15% by weight based on the whole nonaqueous solvent. Water electrolyte. (7) The above general formula [2a] or [2b] in a non-aqueous solvent
Wherein the weight ratio of at least one cyclic carbonate to the chain carbonate is from 15:85 to 55:45. (8) The non-aqueous electrolyte according to any one of (1) to (7), wherein the electrolyte is a lithium salt. (9) A lithium ion secondary battery including the nonaqueous electrolyte according to any one of (1) to (8). (10) Metallic lithium, lithium-containing alloy, or carbon material capable of doping and undoping lithium ions as a negative electrode active material tin oxide capable of doping and undoping lithium ions, capable of doping and undoping lithium ions Negative electrode containing either titanium oxide or silicon capable of doping / dedoping lithium ions, transition metal oxides, transition metal sulfides, composite oxides of lithium and transition metals, conductive polymers as positive electrode active materials A positive electrode containing any one of a material, a carbon material, and a mixture thereof;
(9) A lithium ion secondary battery comprising any one of the nonaqueous electrolytes described in (9). (11) 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. ).
In addition, as a lithium secondary battery in this invention, there exists a lithium ion secondary battery, for example.

[0009]

Next, the nonaqueous electrolyte for a lithium secondary battery according to the present invention and a nonaqueous electrolyte secondary battery using this nonaqueous electrolyte will be described in detail. The non-aqueous electrolyte solution for a lithium secondary battery according to the present invention comprises (metal or P,
B) It comprises a non-aqueous solvent containing a compound having a-(0)-(Si) bond, and an electrolyte, each of which will be described in detail.

(Metal or P, B)-(0)-(Si)
Compound having a bond As the compound having a (metal element, P or B)-(0)-(Si) bond contained in the non-aqueous solvent in the present invention, a compound represented by the general formula [1] is used.

Embedded image (Here, M represents a metal element or boron or phosphorus.
R ¹ is an alkyloxy group having 1 to 11 carbon atoms, or
Represents a silyloxy group, and when n is 2 or more, R ¹ may be the same or different. R ² , R ³ and R ⁴ may be the same or different and represent an alkyl group, alkenyl group, aryl group or alkyloxy group having 1 to 11 carbon atoms. n represents the number of R ¹ bonded to M, and is the oxidation number of M−1. )

Specific examples of M include magnesium, boron, aluminum, silicon, phosphorus, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, germanium, tin, yttrium, zirconium, and niobium. Is exemplified. Of these, aluminum, boron, phosphorus, titanium, and zirconium Specific examples of preferred R ¹ include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a normal butoxy group, a sec-butoxy group, a tert-butoxy group, a pentoxy group, a hexyloxy group, a phenoxy group,
Examples include a trimethylsilyloxy group, a triethylsilyloxy group, a trimethoxysilyloxy group, and a triethoxysilyloxy group. Among these, a methoxy group, an ethoxy group, a propoxypropoxy group, an isopropoxy group, a normal butoxy group, and a trimethylsilyloxy group are preferred. Specific examples of R ² , R ³ , and R ⁴ include a methyl group, an ethyl group, a vinyl group, a propyl group, an isopropyl group, a 1-propenyl group, a 2-propenyl group, a 1-propynyl group, a 2-propynyl group, and a butyl group. 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, 2,2-dimethylpropyl group, phenyl group, methylphenyl group, ethylphenyl group, pentamethylphenyl group, methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butoxy group, sec-butoxy Group, tert-butoxy group, pentoxy group, hexyloxy group, phenoxy group and the like. In the present invention, from the viewpoint of solubility of the additive in the electrolytic solution, R ^{1 to} R ⁴ desirably have 4 or less carbon atoms, specifically, methyl, ethyl, propyl, isopropyl, normal butyl, isobutyl, Preferred are sec-butyl, methoxy, ethoxy, propoxy, isopropoxy, normal butoxy, isobutoxy and sec-butoxy groups.

Specific examples of the compound represented by the general formula [1] include the following compounds. Magnesium di (trimethylsiloxide), tri (trimethylsilyl) borate, tri (trimethoxysilyl) borate, tri (triethylsilyl) borate, tri (triethoxysilyl) borate, tri (dimethylvinylsilyl) borate, Tri (diethylvinylsilyl) borate, aluminum tri (trimethylsiloxide), dimethoxyaluminoxytrimethylsilane, dimethoxyaluminoxytrimethoxysilane, diethoxyaluminoxytrimethylsilane, diethoxyaluminoxytriethoxysilane, dipropoxyoxyaluminoxy Trimethylsilane, dibutoxyaluminoxytrimethylsilane, dibutoxyaluminoxytrimethoxysilane, dibutoxyaluminoxytriethylsilane, dibutoxyaluminoxytriethoxysilane, zip Poxyaluminoxytriethoxysilane, dibutoxyaluminoxytripropylsilane, dibutoxyaluminoxytrimethoxysilane, dibutoxyaluminoxytriethoxysilane, dibutoxyaluminoxytripropoxyloxysilane, dibutoxyaluminoxytriphenoxysilane, phosphoric acid Tri (trimethylsilyl), tri (triethylsilyl) phosphate,
Tri (tripropylsilyl) phosphate, tri (triphenylsilyl) phosphate, tri (trimethoxysilyl) phosphate, tri (triethoxysilyl) phosphate, tri (triphenoxysilyl) phosphate, tri (dimethylsilyl phosphate) Vinylsilyl), tri (diethylvinylsilyl) phosphate, scandium tri (trimethylsiloxide), titanium tetra (trimethylsiloxide), titanium tetra (triethylsiloxide), titanium tetra (trimethoxysiloxide), titanium oxydi (trimethylsiloxy) ), Vanadium oxytri (trimethylsiloxide), zinc di (trimethylsiloxide), germanium tetra (trimethylsiloxide), tin tetra (trimethylsiloxide), yttrium tri (trimethylsiloxide), zirconium tetra (trimethylsiloxide) Chirushirokishido), and the like Niobupenta (trimethyl siloxide). Among these, particularly preferred compounds are tri (trimethylsilyl) borate, tri (trimethoxysilyl) borate, phosphoric acid (trimethylsilyl) phosphate (trimethoxysilyl), dimethoxyaluminoxytrimethoxysilane, diethoxyaluminoxytriethoxy. Silane, dipropoxyaluminoxytriethoxysilane, dibutoxyaluminoxytrimethoxysilane, dibutoxyaluminoxytriethoxysilane, titanium tetra (trimethylsiloxide) and titanium tetra (triethylsiloxide).

The compound represented by the general formula [1] has an effect of suppressing the reductive decomposition reaction of the non-aqueous solvent during charging.

Non-aqueous solvent The non-aqueous electrolyte according to the present invention contains a compound having a (metal element, P or B)-(0)-(Si) bond represented by the above general formula [1]. A non-aqueous solvent is used. The compound having the (metal element, P or B)-(0)-(Si) bond can be used as an additive to a commonly used non-aqueous solvent.

The content of the compound having a (metallic element or B)-(0)-(Si) bond represented by the general formula [1] in the non-aqueous solvent is determined based on the content of the non-aqueous solvent containing the compound. (Metal or P, B)-(oxygen)-represented by the formula [1]
(Total amount of the compound having the (Si) bond and the other non-aqueous solvent) is 0.001% by weight or more, preferably 0.01% by weight.
It is desirable to be in the range of 1 to 15% by weight, more preferably 0.1 to 10% by weight, particularly preferably 0.2 to 5% by weight. When the compound having the (metal or P, B)-(0)-(Si) bond represented by the general formula [1] is contained in such a proportion in the entire non-aqueous solvent containing the compound, the charge The occasional reductive decomposition reaction of the solvent can be suppressed low, so that the battery life such as high-temperature storage characteristics and cycle characteristics can be improved, the charge / discharge efficiency of the battery can be improved, and the low-temperature characteristics can be improved. In the present invention, from the viewpoint of improving battery characteristics (particularly, battery life and load characteristics and low-temperature characteristics),
(The above metal or a compound having a P, B)-(0)-(Si) bond and at least one of cyclic carbonates represented by the following general formula [2a] or [2b] and / or chain carbonates It is desirable to use a non-aqueous solvent containing

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

Embedded image (In the formula [2a] or [2b], R ^{5 to} R ⁸ may be the same or different and are each a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.) The 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,
Examples thereof include 2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. In particular, ethylene carbonate and propylene carbonate having a high dielectric constant are preferably used. When the improvement of the battery life is particularly intended, ethylene carbonate is particularly preferable. 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. In particular, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate having low viscosity are preferably used. These chain carbonates may be used as a mixture of two or more.

Specific examples of the combination of the cyclic carbonate and the chain carbonate of the non-aqueous solvent include ethylene carbonate and dimethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, and propylene carbonate. And methyl ethyl carbonate, propylene carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate, ethylene carbonate and propylene carbonate and methyl ethyl carbonate,
Ethylene carbonate and propylene carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate Diethyl carbonate and the like.

When such a chain carbonate is contained in a non-aqueous solvent, the viscosity of the non-aqueous electrolyte can be lowered, 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, low-temperature characteristics such as load characteristics at low temperatures of the battery can be improved.

In the present invention, the above (metal or P, B)-
A compound having a (0)-(Si) bond and a compound represented by the following general formula [2
When a non-aqueous solvent comprising at least one of the cyclic carbonates represented by a) or [2b] and / or a chain carbonate is used, represented by the general formula [1] (metal or P, The content of the compound having a (B)-(0)-(Si) bond in the non-aqueous solvent is determined based on the total amount of the non-aqueous solvent including the compound (represented by the general formula [1] (metal or P
B) The total amount of the compound having a-(0)-(Si) bond and at least one of the cyclic carbonates represented by the general formula [2a] or [2b] and / or the chain carbonate) 0.001% by weight or more, preferably 0.01 to 15% by weight, more preferably 0.1 to
It is preferably in the range of 10% by weight, particularly preferably 0.2 to 5% by weight. No.

In a non-aqueous solvent, the above-mentioned general formula [2a]
Alternatively, the mixing ratio of at least one of the cyclic carbonates represented by [2b] and the chain carbonate is represented by a weight ratio, and the cyclic carbonate represented by the above general formula [2a] or [2b] At least one of the following: a chain carbonate is 0: 100 to 100: 0, preferably 5: 9
5 to 80:20, more preferably 10:90 to 70:
30, particularly preferably 15:85 to 55:45.
With such a ratio, the increase in the viscosity of the electrolyte can be suppressed, and the degree of dissociation of the electrolyte can be increased. Therefore, the conductivity of the electrolyte relating to the charge / discharge characteristics of the battery can be increased.

Therefore, a preferred non-aqueous solvent according to the present invention is represented by the above general formula [1] (metal or P,
B) A compound containing a compound having a-(0)-(Si) bond and at least one of the cyclic carbonates represented by the general formula [2a] or [2b] and / or the chain carbonate.

In the non-aqueous electrolyte according to the present invention, (Metal or P, B)-(0)-(S
i) When a compound having a bond and another non-aqueous solvent are used as a mixture, the other non-aqueous solvent is replaced with the above-mentioned solvent (cyclic and / or chain carbonate) or the above-mentioned solvent (cyclic and / or cyclic carbonate). And / or chain carbonate), other solvents that are widely used as non-aqueous solvents for batteries may be used. As the other solvents, specifically,
Methyl formate, ethyl formate, propyl formate, methyl acetate,
Chain esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and methyl valerate; phosphate esters such as trimethyl phosphate;
2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether, dimethyl ether, methyl ethyl ether,
Chain ethers such as dipropyl ether; 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolan, 2-
Cyclic ethers such as methyl-1,3-dioxolane; amides such as dimethylformamide; linear carbamates such as methyl-N, N-dimethylcarbamate; γ-butyrolactone, γ-valerolactone, 3-methyl-γ-butyrolactone, 2 Cyclic esters such as -methyl-γ-butyrolactone;
Cyclic sulfones such as sulfolane; cyclic carbamates such as N-methyloxazolidinone; cyclic amides such as N-methylpyrrolidone; cyclic ureas such as N, N-dimethylimidazolidinone; 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-methylene Ethylene 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, 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-methylene ethylene carbonate, 4-methyl-4-acryloxymethyl-5-methylene ethylene carbonate, 4-
Cyclic carbonates such as 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; Alkyl-substituted acryloxymethyl ethylene carbonate such as methyl-4-acryloxymethylethylene carbonate and -methyl-5-acryloxymethylethylene carbonate -Carbonate derivatives; sulfur-containing compounds such as sulfolane and dimethyl sulfate;
Phosphorus-containing compounds such as trimethylphosphoric acid and triethylphosphoric acid; and compounds represented by the following general formula. HO (CH ₂ CH ₂ O) aH, HO ｛CH ₂
CH (CH ₃ ) O｝ b H, 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) eCH 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｝ iCO ｛O (CH ₃ ) C
HCH ₂ ｝ jOCH 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, the above-mentioned (metal element, P, or B) - consist (Si) non-aqueous solvent containing a compound having a bond with an electrolyte - (0) For example, it is obtained by dissolving an electrolyte in a non-aqueous solvent containing a compound having a (metal element, P or B)-(0)-(Si) bond described above. As the electrolyte to be used, any electrolyte which is usually used as an electrolyte used in a non-aqueous electrolyte for a lithium ion secondary battery 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. In addition, a lithium salt represented by the following general formula is also used.
be able to. LiOSO_TwoR₈, Lin (SO_TwoR₉) (S
O_TwoR_Ten), LiC (SO_TwoR₁₁) (SO_TwoR₁₂) (SO_Two
R₁₃), LiN (SO_TwoOR₁₄) (SO_TwoOR_Fifteen)(here
And R₈~ R_FifteenAre the same but different
And a perfluoroalkyl group having 1 to 6 carbon atoms.
). These lithium salts may be used alone or
Or two or more of them may be used in combination.

Among these, in particular, LiPF ₆ , LiB
F ₄ , LiOSO ₂ R ₈ , LiN (SO ₂ R ₉ ) (SO
_{2 R 10), LiC (SO} 2 R 11) (SO 2 R 12) (SO 2 R
₁₃ ), and LiN (SO ₂ OR ₁₄ ) (SO ₂ OR ₁₅ ) are 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 according to the present invention is represented by the above general formula [1] (metal or P, B)-(0)-(S
i) A non-aqueous solvent containing a compound having a bond and an electrolyte are included as essential components, but other additives and the like may be added as necessary.

Lithium secondary battery The lithium secondary battery according to the present invention basically includes a negative electrode, a positive electrode, and the above-mentioned nonaqueous electrolyte, and usually has a separator between the negative electrode and the positive electrode. Is provided.

As the negative electrode active material constituting the negative electrode, metallic lithium, a lithium alloy, a carbon material capable of doping and undoping lithium ions, tin oxide capable of doping and undoping lithium ions, and oxides Any of niobium, vanadium oxide, titanium oxide, and silicon capable of being doped with and dedoped with 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, natural graphite 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
_{O4, LiNiO 2, LiNiXCo (1} -X) lithium and a composite oxide comprising a transition metal such as O _2, polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, a conductive polymer material such as dimercaptothiadiazole / polyaniline complex And the like. 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.
Further, 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 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 obtained 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 disc-shaped negative electrode, a separator, a disc-shaped positive electrode, and a stainless steel or aluminum plate are housed in a coin-shaped battery can in a state of being stacked in this order.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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.

[0039]

Example 1 <Preparation of non-aqueous electrolyte for lithium secondary battery>
Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed with EC: DMC = 40: 60 (weight ratio).
After mixing at a ratio of 99.5 parts by weight of the mixed solvent, the additive [(metal or P, B)-(0)-(S
i) Compound having a bond], 0.5 parts by weight of tri (trimethylsilyl) borate was added to prepare a non-aqueous solvent.
Next, LiPF6 as an electrolyte was dissolved in a non-aqueous solvent to prepare a non-aqueous electrolyte so that the electrolyte concentration was 1.0 mol / L. The leakage current of the battery using this non-aqueous electrolyte was measured by the following method, and the results are shown in Table 1. .

<Preparation of Negative Electrode> Natural graphite (LF made of Chuetsu graphite)
-18A) 87 parts by weight and 13 parts by weight of polyvinylidene fluoride (PVDF) as a binder were mixed and dispersed in N-methylpyrrolidinone as a solvent to prepare a natural graphite mixture slurry. Next, this negative electrode mixture slurry was applied to a 18-μm-thick negative electrode current collector made of strip-shaped copper foil, dried, compression-molded, and punched out into a 14 mm disk shape to form a coin-shaped natural graphite. An electrode was obtained. The thickness of this natural graphite electrode mixture is 1
10 microns, weight was 20 mg / Φ14 mm.

<Production of Battery> A coin-type battery shown in FIG. 1 was produced. 14mm diameter natural graphite electrode 14, diameter 16
A metal lithium foil 13 having a thickness of 0.3 mm and a separator 15 made of a microporous polypropylene film having a thickness of 25 μm and a diameter of 19 mm were made of stainless steel 20.
The lithium metal foil 13, the separator 15, and the natural graphite electrode 14 were stacked in the order of 32 in a 32-size battery can 16.
Thereafter, 0.05 ml of the non-aqueous electrolyte was poured into the separator, and a stainless steel plate 17 (thickness 1.2 mm, diameter 1
5.5 mm and the spring 20 were stored. Finally, a battery can lid 19 is inserted through a gasket 18 made of polypropylene.
By caulking, a coin-type Li-natural graphite battery having a diameter of 20 mm and a height of 3.2 mm was produced while maintaining the airtightness in the battery.

<Measurement of Amount of Electrolysis on Natural Graphite Electrode (Measurement of Leakage Current)> The amount of electrolysis of the electrolytic solution on the natural graphite electrode was measured by measuring a leakage current described below. First, the coin-type Li-natural graphite battery is 1 m
Discharge for a total of 10 hours under the condition of A constant current 0V constant voltage,
Next, charging was performed for 10 hours under the conditions of a constant current of 1 mA and a constant voltage of 1.2 V. Subsequently, a discharge was performed for a total of 5 hours under the condition of a constant current of 2 mA and a constant voltage of 0 V.
Assuming that charging for a total of 5 hours under the condition of V constant voltage was one cycle, two cycles of discharging and charging were performed. Further, discharge was performed for 10 hours under the condition of a constant current of 2 mA and a constant voltage of 0.01 V. Thereafter, the temperature of the battery was raised to 60 ° C., and a total of 2
The discharge was continued for 5 hours, and the change in the current flowing at this time was tracked. This current value rapidly attenuates immediately after the start of discharge at 60 ° C., and becomes substantially constant after 15 hours or more. The current that continues to flow by this fixed amount corresponds to the amount of electrolysis of the electrolytic solution on the natural graphite electrode, and the current value measured at 25 hours was defined as “leakage current”. The value of the leakage current was normalized by the weight of the natural graphite used for the measurement.

Examples 2 to 4 Additive [(metal or P, B)-
(0)-(Si) bond-containing compound], a non-aqueous electrolyte solution for a lithium secondary battery was prepared in the same manner as in Example 1 except that the compounds shown in Table 1 below were used. The leak current was measured in the same manner. The results are shown in Table 1. . Comparative Example 1 As an electrolytic solution, ethylene carbonate (E
C) and dimethyl carbonate (DMC) by EC: D
After mixing at a ratio of MC = 40: 60 (weight ratio), LiPF6 as an electrolyte was added to the mixed solvent at an electrolyte concentration of 1.
Leakage current was measured in the same manner as in Example 1 using a solution dissolved to 0 mol / liter.
The results are shown in Table 1.

[Table 1] As described above, in the electrolytic solution of the present invention, the leakage current indicating the amount of electrolysis of the electrolytic solution on natural graphite is small, indicating that the electrolysis of the electrolytic solution is suppressed.

[0043]

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 is excellent in battery life such as high-temperature storage characteristics and cycle characteristics, charge / discharge characteristics, load characteristics, and battery characteristics at low temperatures. Therefore, this non-aqueous electrolyte is particularly suitable as a non-aqueous electrolyte for a lithium ion secondary battery.

Claims (11)

[Claims] 1. A non-aqueous electrolyte for a lithium secondary battery, comprising a non-aqueous solvent containing a compound represented by the general formula [1] and an electrolyte. Embedded image (Here, M represents a metal element, phosphorus or boron.
R ¹ has 1 to 11 carbon atoms Represents an alkyloxy group or a silyloxy group, and when n is 2 or more, R1s may be the same or different. R ² , R ³ and R ⁴ may be the same or different from each other, and represent an alkyl group, an alkenyl group, an aryl group or an alkyloxy group having 1 to 11 carbon atoms. n represents the number of R ¹ bonded to M;
The oxidation number of M is -1. ) 2. A compound represented by the general formula [1], R ¹ is a methoxy group, an ethoxy group, propyloxy group, butoxy group, a phenoxy group, or a trimethylsilyloxy group, R ^2, R ³ , R ⁴ is a methyl group,
2. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte is any one of an ethyl group, a methoxy group, an ethoxy group, a phenyl group, a phenoxy group, and a vinyl group. 3. The non-aqueous solvent according to the above general formula [1]
The compound represented by the formula (1) and at least one cyclic carbonate represented by the general formula [2a] or [2b] and / or a linear carbonate. Non-aqueous electrolyte. Embedded image (In the formula [2a] or [2b], R ^{5 to} R ⁸ may be the same or different from each other, and are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.) 4. The cyclic carbonate represented by the general formula [2a] or [2b] is ethylene carbonate,
The non-aqueous electrolyte according to claim 3, wherein the non-aqueous electrolyte is one of propylene carbonate, butylene carbonate, and vinylene 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 solution according to claim 1, wherein the compound represented by the general formula [1] is contained in an amount of 0.1 to 15% by weight based on the whole non-aqueous solvent. Water electrolyte. 7. The weight ratio of at least one cyclic carbonate represented by the general formula [2a] or [2b] to a chain carbonate in a non-aqueous solvent is 15: 85-5.
The non-aqueous electrolyte according to claim 4, wherein the ratio is 5:45. 8. The non-aqueous electrolyte according to claim 1, wherein the electrolyte is a lithium salt. 9. A lithium secondary battery comprising the non-aqueous electrolyte according to claim 1. 10. A negative electrode active material such as metallic lithium, a lithium-containing alloy, a carbon material capable of doping and undoping lithium ions, a tin oxide capable of doping and undoping lithium ions, and a doping and undoping of lithium ions A negative electrode containing any of titanium oxide, niobium oxide, vanadium oxide or silicon capable of doping and undoping lithium ions, and a transition metal oxide, a transition metal sulfide, and a mixture of lithium and a transition metal as a positive electrode active material. A lithium secondary battery comprising: a positive electrode containing any one of a composite oxide, a conductive polymer material, a carbon material, and a mixture thereof; and the nonaqueous electrolyte according to any one of claims 1 to 8. . 11. The carbon material capable of doping / dedoping lithium ions is measured by X-ray analysis.
2) The plane distance (d002) on the plane is 0.340
11. The lithium secondary battery according to claim 10, wherein the thickness is equal to or less than nm.