JP3444243B2 - Nonaqueous electrolyte and lithium secondary battery using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte capable of providing a lithium secondary battery having excellent battery characteristics such as cycle characteristics, electric capacity, and storage characteristics, and a lithium using the same. Regarding secondary batteries.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries have been widely used as driving power sources for small electronic devices and the like. A lithium secondary battery is mainly composed of a positive electrode, a non-aqueous electrolytic solution and a negative electrode. In particular, a lithium secondary battery using a lithium composite oxide such as LiCoO ₂ as a positive electrode and a carbon material or a lithium metal as a negative electrode is a lithium secondary battery. It is preferably used. Then, as the non-aqueous electrolyte for the lithium secondary battery, ethylene carbonate (EC), propylene carbonate (P
Carbonates such as C) are preferably used.

[0003]

However, regarding the battery cycle characteristics and battery characteristics such as electric capacity,
There is a demand for secondary batteries having even more excellent characteristics.
As the positive electrode, for example, LiCoO ₂ , LiMn ₂ O ₄ , Li
In a lithium secondary battery using NiO ₂ or the like, a solvent in a non-aqueous electrolyte is partially oxidatively decomposed during charging, and the decomposed product inhibits a desired electrochemical reaction of the battery. This results in poor performance. This is probably due to the electrochemical oxidation of the solvent at the interface between the positive electrode material and the non-aqueous electrolyte. Further, for example, a lithium secondary battery using a highly crystallized carbon material such as natural graphite or artificial graphite as a negative electrode, the solvent in the non-aqueous electrolytic solution is reductively decomposed on the surface of the negative electrode during charging, and as a non-aqueous electrolytic solution solvent. Even in the generally widely used EC, a part of reductive decomposition occurs during repeated charging and discharging, resulting in deterioration of battery performance. Therefore, at present, the battery cycle characteristics and battery characteristics such as electric capacity are not always satisfactory.

The present invention solves the problems relating to the non-aqueous electrolyte for a lithium secondary battery as described above, is excellent in battery cycle characteristics, and is also excellent in battery characteristics such as electric capacity and storage characteristics in a charged state. Another object of the present invention is to provide a non-aqueous electrolyte solution for a lithium secondary battery, which can form a lithium secondary battery, and a lithium secondary battery using the same.

[0005]

The present invention provides a non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, wherein the following formula (I) is contained in the non-aqueous electrolytic solution.

[0006]

[Chemical 5] (However, X ¹ and X ² are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, and 2 to 2 carbon atoms.
An alkynyl group having 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms,
An aryl group, an acyl group having 2 to 7 carbon atoms, an alkanesulfonyl group having 1 to 7 carbon atoms, an arylsulfonyl group having 6 to 10 carbon atoms, and an ester group having 2 to 7 carbon atoms are shown. ) A disulfide derivative containing oxygen as a substituent represented by the following formula, and the following formula (II)

[0007]

[Chemical 6] (However, X ³ , X ⁴ are independently F, Cl, B
r, I, CF ₃ , CCl ₃ , and CBr ₃ are shown. And a disulfide derivative containing halogen in the substituent represented by (4) is contained in an amount of 0.01 to 5% by weight. Further, in a lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, the following formula (I) is contained in the non-aqueous electrolytic solution.

[0008]

[Chemical 7] (However, X ¹ and X ² are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, and 2 to 2 carbon atoms.
An alkynyl group having 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms,
An aryl group, an acyl group having 2 to 7 carbon atoms, an alkanesulfonyl group having 1 to 7 carbon atoms, an arylsulfonyl group having 6 to 10 carbon atoms, and an ester group having 2 to 7 carbon atoms are shown. ) A disulfide derivative containing oxygen as a substituent represented by the following formula, and the following formula (II)

[0009]

[Chemical 8] (However, X ³ , X ⁴ are independently F, Cl, B
r, I, CF ₃ , CCl ₃ , and CBr ₃ are shown. The present invention relates to a lithium secondary battery containing 0.01 to 5% by weight of a disulfide derivative containing halogen as a substituent represented by the formula (1).

The non-aqueous electrolytic solution of the present invention is used as a constituent member of a lithium secondary battery. The constituent members other than the non-aqueous electrolyte that constitute the secondary battery are not particularly limited, and various conventionally used constituent members can be used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the disulfide derivative represented by the above formula (I) contained in an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, X ¹ and X ² are a methyl group, an ethyl group,
An alkyl group having 1 to 6 carbon atoms such as a propyl group, a butyl group, a pentyl group and a hexyl group is preferable. The alkyl group may be a branched alkyl group such as an isopropyl group, an isobutyl group and an isopentyl group, or a cycloalkyl group such as a cyclopropyl group and a cyclohexyl group. Also,
It may be an alkenyl group such as a vinyl group, a 1-propenyl group or an allyl group, or an alkynyl group such as an ethynyl group or a 2-propynyl group. Further, an aryl group such as a phenyl group or a p-tolyl group may be used. Further, it may be an acyl group such as an acetyl group, a propionyl group, an acryloyl group and a benzoyl group, or a sulfonyl group such as a methanesulfonyl group, an ethanesulfonyl group and a benzenesulfonyl group. Further, an ester group such as a methoxycarbonyl group, an ethoxycarbonyl group, a phenoxycarbonyl group, a benzyloxycarbonyl group may be used. In addition, the above formula (I
In the disulfide derivative represented by I), X ³ , X ⁴
Is preferably a halogen atom such as F, Cl, Br or I, or a substituent containing a halogen atom such as CF ₃ , CCl ₃ or CBr ₃ .

Specific examples of the disulfide derivative represented by the general formula (I) include bis (4-methoxyphenyl) disulfide [X ¹ , X ² = methyl group] and bis (3-methoxyphenyl) disulfide. [X ¹ , X ² = methyl group], bis (2-methoxyphenyl) disulfide [X ¹ , X ² = methyl group], bis (4-ethoxyphenyl) disulfide [X ¹ , X ² = ethyl group], bis (4-
Isopropoxyphenyl) disulfide [X ¹ , X ² = isopropyl group], bis (4-cyclohexyloxyphenyl) disulfide [X ¹ , X ² = cyclohexyl group],
Bis (4-allyloxyphenyl) disulfide [X ¹ , X ² = allyl group], bis [4- (2-propynyloxy) phenyl] disulfide [X ¹ , X ² = 2-propynyl group], bis (4- Phenoxyphenyl) disulfide [X ¹ , X ² = phenyl group], bis (4-acetoxyphenyl) disulfide [X ¹ , X ² = acetyl group], bis (4-benzoyloxyphenyl) disulfide [X
¹ , X ² = benzoyl group], bis (4-methanesulfonyloxyphenyl) disulfide [X ¹ , X ² = methanesulfonyl group], bis (4-benzenesulfonyloxyphenyl) disulfide [X ¹ , X ² = benzenesulfonyl Group], bis (4-methoxycarbonyloxyphenyl)
And disulfide [X ¹ , X ² = methoxycarbonyl group], bis (4-phenoxycarbonyloxyphenyl) disulfide [X ¹ , X ² = phenoxycarbonyl group] and the like. Specific examples of the disulfide derivative represented by the general formula (II) are, for example, bis (4-fluorophenyl) disulfide [X ^3, X ⁴ = F], bis (4-chlorophenyl) disulfide [X ³ , X ⁴ = C
l], bis (4-bromophenyl) disulfide [X ³ , X ⁴ = Br], bis (4-iodophenyl) disulfide [X ³ , X ⁴ = I], bis (4-trifluoromethylphenyl) disulfide [ X ³ , X ⁴ = CF ₃ ], bis (4-trichloromethylphenyl) disulfide [X
³ , X ⁴ = CCl ₃ ], bis (4-tribromomethylphenyl) disulfide [X ³ , X ⁴ = CBr ₃ ].

If the content of the disulfide derivative containing oxygen as a substituent represented by the formula (I) contained in the non-aqueous electrolyte is excessively large, the battery performance may be deteriorated. If it is too small, the expected battery performance will not be obtained. Therefore, the content is preferably in the range of 0.01 to 5% by weight with respect to the weight of the non-aqueous electrolyte, because the cycle characteristics are improved.

The non-aqueous solvent used in the present invention is preferably a solvent composed of a high dielectric constant solvent and a low viscosity solvent. Preferable examples of the high dielectric constant solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC). These high dielectric constant solvents may be used alone or in combination of two or more.

Examples of the low-viscosity solvent include dimethyl carbonate (DMC) and methyl ethyl carbonate (M
EC), chain carbonates such as diethyl carbonate (DEC), tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane And ethers, lactones such as γ-butyrolactone, nitriles such as acetonitrile, esters such as methyl propionate, and amides such as dimethylformamide. These low-viscosity solvents may be used alone or in combination of two or more. The high dielectric constant solvent and the low viscosity solvent are arbitrarily selected and used in combination. The high dielectric constant solvent and the low viscosity solvent are usually used in a volume ratio (high dielectric constant solvent: low viscosity solvent) of 1: 9 to 4: 1, preferably 1: 4 to 7: 3. It

Examples of the electrolyte used in the present invention include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN (S
O ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂
CF ₃ ) _{3 and the} like. These electrolytes may be used alone or in combination of two or more. These electrolytes are usually added to the above non-aqueous solvent in an amount of 0.1 to 0.1%.
It is used by being dissolved at a concentration of 3M, preferably 0.5 to 1.5M.

The non-aqueous electrolytic solution of the present invention is prepared by, for example, mixing the above-mentioned high dielectric constant solvent or low-viscosity solvent, dissolving the above electrolyte therein, and adding oxygen to the substituent represented by the above formula (I). It is obtained by dissolving a disulfide derivative containing

For example, as the positive electrode active material, a composite metal oxide of at least one metal selected from the group consisting of cobalt, manganese, nickel, chromium, iron and vanadium and lithium is used. Examples of such complex metal oxides include LiCoO ₂ , LiMn ₂ O ₄ ,
Examples thereof include LiNiO ₂ .

The positive electrode is prepared by kneading the above positive electrode active material with a conductive agent such as acetylene black or carbon black, a binder such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), and a solvent to mix the positive electrode. Then, this positive electrode material is applied to an aluminum foil or a stainless steel lath plate as a current collector, dried, pressure-molded, and then heat-treated under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. It is produced by

As the negative electrode active material, lithium metal or lithium alloy, and a carbon material having a graphite type crystal structure capable of inserting and extracting lithium [pyrolytic carbons, cokes,
Materials such as graphites (artificial graphite, natural graphite, etc.), organic polymer compound combustors, carbon fibers] and complex tin oxides are used. In particular, the interplanar spacing (d) of the lattice plane (002)
It is preferable to use a carbon material having a graphite type crystal structure in which ₀₀₂ ) is 0.335 to 0.340 nm (nanometer). A powder material such as a carbon material is kneaded with a binder such as ethylene propylene diene terpolymer (EPDM), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF) to be used as a negative electrode mixture.

The structure of the lithium secondary battery is not particularly limited, and a coin type battery having a positive electrode, a negative electrode and a single-layer or multi-layer separator, and a cylindrical battery having a positive electrode, a negative electrode and a roll-shaped separator. An example is a square battery or the like. As the separator, a well-known polyolefin microporous film, woven fabric, non-woven fabric, or the like is used.

[0022]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Example 1 [Preparation of non-aqueous electrolyte] EC: DMC (volume ratio) = 1: 2
Of non-aqueous solvent was prepared and LiPF ₆ was dissolved therein to a concentration of 1 M to prepare a non-aqueous electrolytic solution, and then bis (4-methoxyphenyl) disulfide [X ¹ , X ² =
Methyl group] was added to the non-aqueous electrolytic solution so as to be 0.1% by weight.

[Preparation of Lithium Secondary Battery and Measurement of Battery Characteristics] 80% by weight of LiCoO ₂ (positive electrode active material), 10% by weight of acetylene black (conductive agent), and 10% by weight of polyvinylidene fluoride (binder). %, And a mixture of 1-methyl-2-pyrrolidone solvent added and mixed was applied onto an aluminum foil, dried, pressure-molded, and heat-treated to prepare a positive electrode. 90% by weight of natural graphite (negative electrode active material) and 10% by weight of polyvinylidene fluoride (binder) were mixed, 1-methyl-2-pyrrolidone solvent was added thereto, and the mixture was mixed on a copper foil. Apply to, dry
A negative electrode was prepared by pressure molding and heat treatment. Then, using a polypropylene microporous film separator, the above-mentioned non-aqueous electrolyte was injected and a coin battery (diameter 20 mm,
A thickness of 3.2 mm) was produced. Using this coin battery, it was charged at a constant current and a constant voltage of 0.8 mA at room temperature (20 ° C.) to a final voltage of 4.2 V for 5 hours, and then 0.8 m.
Under the constant current of A, the battery was discharged to a final voltage of 2.7 V, and this charging / discharging was repeated. The initial charge / discharge capacity is EC-DMC (1
/ 2) was used as a non-aqueous electrolyte (Comparative Example 1), and the battery characteristics after 60 cycles were measured. As a result, the discharge capacity retention ratio was 93 when the initial discharge capacity was 100%. It was 0.5%. The low temperature characteristics were also good. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 2 As an additive, bis (4-methoxyphenyl) disulfide [X ¹ , X ² = methyl group] was added to the non-aqueous electrolyte solution in an amount of 0.
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the amount of the used battery was 05% by weight, and a coin battery was prepared. After 60 cycles, the battery characteristics were measured. The discharge capacity retention rate was 92.1%. . Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 3 As an additive, bis (4-methoxyphenyl) disulfide [X ¹ , X ² = methyl group] was added to the nonaqueous electrolytic solution in an amount of 0.
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that 2% by weight was used, and a coin battery was prepared. After 60 cycles, the battery characteristics were measured. The discharge capacity retention rate was 92.4%. . Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 4 Same as Example ¹ except that bis (4-acetoxyphenyl) disulfide [X ¹ , X ² = acetyl group] was used as an additive in an amount of 0.1% by weight based on the non-aqueous electrolyte. A non-aqueous electrolyte solution was prepared to prepare a coin battery, and the battery characteristics after 60 cycles were measured. The discharge capacity retention rate was 91.2%.
Met. Table 1 shows the coin battery manufacturing conditions and battery characteristics.
Shown in.

Example 5 As an additive, bis (4-methanesulfonyloxyphenyl) disulfide [X ¹ , X ² = methanesulfonyl group]
Was used in the same manner as in Example 1 except that 0.1% by weight was used with respect to the non-aqueous electrolytic solution to prepare a coin battery, and the battery characteristics after 60 cycles were measured. The maintenance rate was 92.9%. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 6 Bis (4-methoxycarbonyloxyphenyl) disulfide [X ¹ , X ² = methoxycarbonyl group] was used as an additive in an amount of 0.1% by weight based on the non-aqueous electrolyte. A non-aqueous electrolyte was prepared in the same manner as in No. 1 to prepare a coin battery, and the battery characteristics after 60 cycles were measured, whereupon the discharge capacity retention rate was 92.7%. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 7 Similar to Example 1 except that bis (4-fluorophenyl) disulfide [X ³ , X ⁴ = F] was used as an additive in an amount of 0.1% by weight based on the non-aqueous electrolyte. When a non-aqueous electrolyte was prepared to prepare a coin battery and the battery characteristics after 60 cycles were measured, the discharge capacity retention rate was 92.8%.
Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 8 Similar to Example 1, except that bis (4-chlorophenyl) disulfide [X ³ , X ⁴ = Cl] was used as an additive in an amount of 0.1% by weight based on the non-aqueous electrolyte. A water battery was prepared to prepare a coin battery, and the battery characteristics after 60 cycles were measured, whereupon the discharge capacity retention ratio was 91.6%.
Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 9 Example 1 except that bis (4-trifluoromethylphenyl) disulfide [X ³ , X ⁴ = CF ₃ ] was used as an additive in an amount of 0.1% by weight based on the non-aqueous electrolyte. A non-aqueous electrolyte was prepared in the same manner as in 1. to produce a coin battery, and the battery characteristics after 60 cycles were measured.
It was 2.5%. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 10 A non-aqueous solvent of EC: PC: DMC (volume ratio) = 1: 1: 2 was prepared, and LiPF ₆ was dissolved therein to a concentration of 1 M to prepare a non-aqueous electrolytic solution. And then bis (4-methoxyphenyl) disulfide [X ¹ , X ² = methyl group]
Was added so as to be 0.1% by weight with respect to the non-aqueous electrolyte. Using this non-aqueous electrolyte, a coin battery was prepared in the same manner as in Example 1 and the battery characteristics were measured. As a result, the initial discharge capacity was EC-DMC (capacity ratio 1/2) only as the non-aqueous electrolyte. When the battery characteristics after 60 cycles were measured, the discharge capacity retention ratio was 93.0% when the initial discharge capacity was 100%. The low temperature characteristics were also good. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 11 As a negative electrode active material, a non-aqueous electrolyte was prepared in the same manner as in Example 1 except that artificial graphite was used in place of natural graphite to prepare a coin battery, and the battery characteristics after 60 cycles were evaluated. When measured, the discharge capacity retention rate was 90.3%. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 12 As a positive electrode active material, LiMn ₂ O ₄ was used instead of LiCoO _2.
A coin battery was prepared by preparing a non-aqueous electrolyte solution in the same manner as in Example 1 except that was used, and the battery characteristics after 60 cycles were measured. The discharge capacity retention rate was 94.5%.
Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Comparative Example 1 A non-aqueous solvent of EC: DMC (volume ratio) = 1: 2 was prepared,
LiPF ₆ was dissolved in this to a concentration of 1M.
At this time, disulfide was not added at all. Using this non-aqueous electrolytic solution, a coin battery was produced in the same manner as in Example 1 and the battery characteristics were measured. The discharge capacity retention ratio after 60 cycles was 83.8% with respect to the initial discharge capacity. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Comparative Example 2 A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that 0.1% by weight of diphenyldisulfide [X ³ , X ⁴ = none] was used as an additive with respect to the nonaqueous electrolytic solution. Then, a coin battery was produced, and the battery characteristics after 60 cycles were measured, whereupon the discharge capacity retention rate was 88.7%. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery. As described above, when the electrolytic solution containing the additive of the present invention was used, the cycle characteristics were dramatically improved as compared with the system without addition. It is considered that this is because the additive is oxidatively decomposed on the positive electrode during charging and forms a film that improves the reversibility of the battery. Also,
With the additive of the present invention, even better cycle characteristics were obtained compared to the diphenyl disulfide addition system in which the benzene ring does not contain a substituent. The reason for this is that the benzene ring is replaced by an atom having many unshared electron pairs such as oxygen or halogen, and electrons flow from these atoms to the positive electrode during charging, resulting in a smoother oxidation reaction. I think that the. In addition to the cycle characteristics, the additive of the present invention had better solubility in an electrolytic solution than diphenyl disulfide. It is considered that this is because having a substituent on the benzene ring increases the polarity. Further, the additive of the present invention has less odor peculiar to the disulfide compound than the diphenyl disulfide. This is also likely to be due to the substituents on the benzene ring. As described above, the additive of the present invention has not only cycle characteristics but also solubility in an electrolytic solution and handling in terms of less bad odor as compared with diphenyl disulfide having no substituent in the benzene ring. Because of its superiority, it can be said that it is a better additive for the electrolyte.

The present invention is not limited to the embodiments described above, and various combinations that can be easily inferred from the spirit of the invention are possible. In particular, the combination of solvents in the above examples is not limited. Furthermore, although the above embodiments relate to coin batteries, the present invention is also applicable to cylindrical and prismatic batteries.

[0038]

[Table 1]

[0039]

According to the present invention, the cycle characteristics of the battery,
A lithium secondary battery having excellent battery characteristics such as electric capacity and storage characteristics can be provided.

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-7-320779 (JP, A) JP-A-6-36797 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/40

Claims (4)

(57) [Claims] 1. A non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution has the following formula (I): (However, X ¹ and X ² are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, and 2 to 2 carbon atoms.
An alkynyl group having 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms,
An aryl group, an acyl group having 2 to 7 carbon atoms, an alkanesulfonyl group having 1 to 7 carbon atoms, an arylsulfonyl group having 6 to 10 carbon atoms, and an ester group having 2 to 7 carbon atoms are shown. ) Is a disulfide derivative containing oxygen as a substituent.
Lithium, characterized in that 01-5 are contained wt%
Non-aqueous electrolyte for secondary batteries . 2. A non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution has the following formula (II): (However, X ³ , X ⁴ are independently F, Cl, B
r, I, CF ₃ , CCl ₃ , and CBr ₃ are shown. Li that) disulfide derivatives containing a halogen substituent represented by is characterized in that it is 0.01 to 5 wt%
A non-aqueous electrolyte for a rechargeable lithium battery . 3. A lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution has the following formula (I): (However, X ¹ and X ² are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, and 2 to 2 carbon atoms.
An alkynyl group having 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms,
An aryl group, an acyl group having 2 to 7 carbon atoms, an alkanesulfonyl group having 1 to 7 carbon atoms, an arylsulfonyl group having 6 to 10 carbon atoms, and an ester group having 2 to 7 carbon atoms are shown. ) Is a disulfide derivative containing oxygen as a substituent.
A lithium secondary battery characterized by being contained in an amount of 01 to 5% by weight. 4. A lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution has the following formula (II): (However, X ³ , X ⁴ are independently F, Cl, B
r, I, CF ₃ , CCl ₃ , and CBr ₃ are shown. ) A lithium secondary battery containing 0.01 to 5% by weight of a disulfide derivative containing a halogen as a substituent.