JP2000021442A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the high temperature service life characteristic of a secondary battery by using LiMn2O4 of a spineal structure as a positive electrode active material, using a carbon material as a negative electrode, and using an organic solvent containing lithium salt and a vinylen carbonate or oligoethylene oxypolyphosphazene as a nonaqueous electrolyte. SOLUTION: A nonaqueous electrolyte secondary battery is obtained by using a positive electrode using Mn2O4 powder, having a spinel structure as a positive electrode active material, a negative electrode using a carbon material and a nonaqueous electrolyte by dissolving lithium salt of one kind of LiPF6 and LiBF4 in an organic solvent. One kind of a vinylen carbonate and oligoethylene oxypolyphosphazene is also included by 0.1 to 10 wt.% in this electrolyte. A ethylen carbonate, a propylene carbonate, a dimethyl or diethyle carbonate, a methyl ethyle carbonate, 1,2-dimethoxyethane, a methyl propylene carbonate, γ-butyrolactone, methyl propionate and ethyl propionate and the like are desirable as the organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nonaqueous electrolyte secondary battery using lithium manganate having a spinel structure as a positive electrode active material.

[0002]

2. Description of the Related Art Conventionally, in the case of a nonaqueous electrolyte secondary battery using a lithium manganate having a spinel structure as a positive electrode active material, a carbon material as a negative electrode, and a nonaqueous electrolyte in which a lithium salt is dissolved in an organic solvent. At high temperatures of 50 ° C. or higher, manganese elutes from the positive electrode active material, and this manganese ion reaches the negative electrode through the electrolytic solution and precipitates on the negative electrode to cause capacity deterioration.
The cycle life performance was impaired.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to improve the high-temperature life characteristics of a nonaqueous electrolyte secondary battery using lithium manganate having a spinel structure as a positive electrode active material.

[0004]

According to the present invention, a lithium manganate having a spinel structure as a positive electrode active material, a carbon material as a negative electrode, and at least one lithium salt of LiPF ₆ or LiBF ₄ dissolved in an organic solvent. A non-aqueous electrolyte secondary battery using an aqueous electrolyte, wherein vinylene carbonate is contained in the non-aqueous electrolyte.
Wherein the vinylene carbonate comprises at least one kind of oligoethyleneoxy polyphosphazene;
At least one of oligoethyleneoxy polyphosphazenes
The content of the seed is 0.1 to 10% by weight, and the organic solvent is ethylene carbonate, propylene carbonate.
Dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane,
Methyl propylene carbonate, r-butyrolactone,
It is characterized in that it is at least one selected from methyl propionate and ethyl propionate.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A positive electrode has a spinel structure and lithium manganate having an average particle size of 10 μm and an average particle size of 3 μm.
Of carbon powder and polyvinylidene fluoride (PV
DF) and N-methyl-2-pyrrolidone (NM
P) and mix to form a slurry-like solution.
This slurry is applied to both sides of a 20 μm thick aluminum foil as a positive electrode current collector, dried and pressed to be integrated.
Then, it cut | disconnected to width 54mm and length 450mm, and produced the strip-shaped positive electrode. The negative electrode was prepared by adding amorphous carbon having an average particle diameter of 20 μm and polyvinylidene fluoride (PVDF) as a binder to N-methyl-2-pyrrolidone (NMP) as a solvent and mixing the resulting mixture to form a slurry-like solution. Is prepared. This slurry is applied to both surfaces of a 10 μm thick copper foil as a negative electrode current collector, dried and pressed to be integrated. After that, width 56m
m, and cut into a length of 500 mm to produce a strip-shaped negative electrode. The prepared positive electrode and negative electrode are combined and wound through a separator made of a polyethylene porous film having a thickness of 40 μm and a width of 58 mm to form a wound group. This wound group is inserted into a battery can, connected to the upper lid and the can, respectively, of the positive electrode and the negative electrode, and 5 ml of an electrolyte is injected. After that, the upper lid was swaged via packing and sealed, and the diameter was 18 mm and the height was 65 mm.
Was manufactured.

[0006]

EXAMPLES Non-aqueous electrolyte secondary batteries of Examples and Comparative Examples of the present invention were prepared and initially charged at a current value of 0.5 CmA, and then discharged in a 50 ° C. constant temperature bath at a current value of 1 C.
CmA, 2.7V final voltage and 0.5CmA-4.2 charge
A high-temperature life test in which V constant voltage charging and 4 hours were repeated was performed, and the results are shown in Table 1. The cycle number of the high-temperature life was represented by the number of cycles in which the charge / discharge cycle was repeated and reduced to 80% of the initial capacity.

[0007] The lithium salt of the electrolyte solution in which the high-temperature life test is LiPF _6, solvent of the electrolytic solution, Echirenka - Boneito + Jimechiruka - BONNET - Application: a (1 2 (vol%)) .

[0008]

[Table 1]

As is clear from Table 1, Examples 1 to 8 in which vinylene carbonate and oligoethyleneoxy polyphosphazene are added to the electrolytic solution have better high-temperature life characteristics than Comparative Examples. In this example, LiPF ₆ was used as the lithium salt in the non-aqueous electrolyte, but the same result was obtained with LiBF ₄ . However, LiPF ₆ , LiBF ₄
Other lithium salts such as LiClO ₄ and LiCF ₃ SO ₃ had no effect.

[0010]

The non-aqueous electrolyte secondary battery according to the present invention is characterized in that vinylene carbonate or oligoethyleneoxy polyphosphazene is added to the electrolyte so that manganese ions eluted from the cathode at high temperatures can be applied to the anode. Can be suppressed, and the high-temperature life characteristics can be significantly improved.

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Claims (3)

[Claims] 1. A non-aqueous electrolyte using a non-aqueous electrolyte in which lithium manganate having a spinel structure is used as a positive electrode active material, a carbon material is used as a negative electrode, and at least one lithium salt of LiPF ₆ or LiBF ₄ is dissolved in an organic solvent. An electrolyte secondary battery, wherein the nonaqueous electrolyte contains at least one of vinylene carbonate and oligoethyleneoxy polyphosphazene. 2. The method according to claim 1, wherein the content of at least one of vinylene carbonate and oligoethyleneoxy polyphosphazene is 0.1 to 10% by weight.
The non-aqueous electrolyte secondary battery according to the above. 3. The method according to claim 1, wherein the organic solvent is ethylene carbonate,
Propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2
-Dimethoxyethane, methyl propylene carbonate,
The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the non-aqueous electrolyte secondary battery is at least one selected from r-butyrolactone, methyl propionate, and ethyl propionate.