JP2000021381A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery hardly degrading capacity by a charge/ discharge cycle at a high temperature by using lithium manganese composite oxide as a positive electrode active material, by using a material by adding a cation exchange resin to a material mainly composed of a polyolefine resin as a separator. SOLUTION: Lithmum manganese composite oxide having the average particle size 10 μm as a positive electrode active material, carbon powder as a conductive assistant and polyvinylidene fluoride as a binding agent are mixed in wt.% of (82:12:6). N-methyl-2-pyrolidone is inputted/mixed there to manufacture a slurry-like solution to be applied to Al foil, and after being dried, it is rolled and cut. A carbon material capable of storing/releasing a lithium ion is used as a negative electrode active material. 90 wt.% the carbon material and 10 wt.% of the polyvinylidene fluoride as a binding agent are mixed, and the N-methyl-2-pyrolidone is inputted/mixed to manufacture a slurry-like solution to be applied to both surface of copper foil, and after being dried, it is rolled and cut.

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 secondary battery using a lithium manganese composite oxide for a positive electrode.

[0002]

2. Description of the Related Art Mobile phones, cordless phones, video equipment such as video cameras, office equipment such as personal computers,
There is a strong demand for a lithium ion secondary battery that can be used for a long time as a main power supply or a backup power supply for home appliances and electric vehicles. In addition, as a positive electrode active material used in these lithium ion secondary batteries,
Lithium cobalt composite oxide, lithium nickel composite oxide, lithium manganese composite oxide, etc. are used. Among them, lithium manganese composite oxide using manganese as a raw material, which is abundant and inexpensive as a raw material, is attracting attention. .

[0003] The lithium manganese composite oxide has a spinel structure that easily absorbs and releases lithium.
However, when the lithium manganese composite oxide is used for the positive electrode active material, although the initial charge / discharge characteristics can be satisfied to some extent, the discharge capacity deteriorates as the charge / discharge cycle progresses and the leaving period becomes longer. The reason for this is that manganese in the positive electrode active material becomes ions and elutes into the electrolyte,
The eluted manganese ions precipitate on the active material surface of the negative electrode,
It has been clarified that this is because the absorption and release of lithium ions of the negative electrode active material are inhibited. At a high temperature of 50 ° C. or higher, this tendency is remarkable, and there is a problem that the charge / discharge cycle life is rapidly shortened.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-aqueous electrolyte secondary battery using a lithium manganese composite oxide as a positive electrode active material and having a small capacity deterioration due to charge and discharge cycles at high temperatures. Is what you do.

[0005]

According to the present invention, a lithium manganese composite oxide having a spinel structure in a positive electrode and doping and undoping of lithium ions in a negative electrode by charging and discharging can be achieved. A nonaqueous electrolyte secondary battery using a carbon material is characterized in that the separator is made of a material mainly composed of a polyolefin-based resin and to which a cation exchange resin is added.

[0006]

Embodiments of the present invention will be described below. However, the present invention is not limited to these. 1. Positive electrode As a positive electrode active material, a lithium manganese composite oxide having an average particle size of 10 μm, a carbon powder as a conductive aid, polyvinylidene fluoride as a binder (trade name: KF1120, manufactured by Kureha Chemical Industry Co., Ltd .; hereinafter, PVdF) 82):
Mix at 12: 6% by weight. There, N-methyl-2
-Add and mix pyrrolidone to make a slurry solution. This mixed solution was applied to both sides of a 20 μm-thick aluminum foil with this slurry, the solvent was dried, and then rolled with a roller press to produce a positive electrode mixture electrode.
A short and narrow positive electrode was prepared by cutting into a width of 450 mm and a length of 450 mm.

[0007] 2. Negative electrode A commonly used carbon material capable of occluding and releasing lithium ions was used as a negative electrode active material. Carbon material 90
wt. %, Polyvinylidene fluoride (brand name: KF1120, manufactured by Kureha Chemical Industry Co., Ltd.) 10 wt.
%, And N-methyl-2-pyrrolidone is added and mixed to prepare a slurry-like solution. This slurry-like solution was applied to both sides of a copper foil having a thickness of 10 μm, and after drying the solvent, the resultant was rolled with a roller press, and cut into a width of 56 mm and a length of 500 mm to prepare a strip-shaped negative electrode. .

[0008] 3. Battery The positive electrode and the negative electrode produced by the above-described method are wound via a separator made of a microporous polyethylene film having a thickness of 40 µm and a width of 58 mm, which will be described later, to produce a spiral wound group. The wound group is inserted into a battery can, and a nickel tab terminal previously welded to the copper foil of the negative electrode current collector is welded to the bottom of the battery can. Next, LiPF ₆ was added to a solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 1.
Was dissolved at a concentration of 1 mol / l in a battery container.
ml was injected. Next, an aluminum tab terminal previously welded to the aluminum foil of the positive electrode current collector was welded to the lid, and the lid was placed on the top of the battery can via an insulating gasket,
This part is caulked and sealed, diameter 18mm, height 65m
m was manufactured.

4. Initial charge / discharge test and cycle test The prepared battery was allowed to stand at 25 ° C. for 24 hours, and a constant voltage of 4.
After charging for 3 hours at 2 V (however, 900 mA of limiting current), discharging to 450 V of discharge current to 2.7 V for 10 cycles was performed. The battery subjected to the initial charge / discharge test has a charging current of 450 mA at 50 ° C. (charging end voltage 4.2 V, charging for a maximum of 4 hours), and a discharging current of 900 m.
A charge / discharge cycle test was performed under the condition of A (discharge end voltage 2.7 V). Then, the number of cycles when the capacity reached 80% or less of the initial discharge capacity was determined as the life of the battery.

[0010]

EXAMPLES (Examples 1 to 8) The present invention uses a separator containing polyethylene as a main component to which various cation exchange resins are added. That is, phenolsulfonic acid resin,
As shown in Table 1, polystyrene sulfonic acid, sulfonated styrene resin, and resorcin resin were added to the above-described separator in an amount of 0.5% by weight or 10% by weight, respectively. Other electrode and battery fabrication conditions and life test methods are as described above.

(Comparative Example 1) A separator mainly containing polyethylene to which no cation exchange resin was added as Comparative Example 1 was subjected to a life test under the above-mentioned conditions, and the influence thereof was measured. Other conditions for manufacturing the electrode and the battery are as described above.

Table 1 shows the results of a life test of these batteries by the method described above. As is clear from Table 1, Examples 1 to 4 using the separator to which the cation exchange resin was added.
Sample No. 8 has a service life that is 3 to 4 times longer than that of Comparative Example 1, and shows excellent characteristics.

[0013]

[Table 1]

[0014]

As described above, the nonaqueous electrolyte secondary battery according to the present invention uses a lithium manganese composite oxide having a spinel structure for the positive electrode, and a cation exchange resin is added to the separator. As a result, the life characteristics can be significantly improved. In Examples 1 to 8, a battery using a separator to which phenolsulfonic acid resin, polystyrene sulfonic acid, sulfonated styrene resin, and resorcinol resin were added was shown. However, the same effect can be obtained for other cation exchange resins. I got it.

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Claims (1)

[Claims] 1. A non-aqueous electrolyte secondary battery using a lithium manganese composite oxide having a spinel structure in a positive electrode and a carbon material capable of doping and undoping lithium ions by charging and discharging in a negative electrode. A non-aqueous electrolyte secondary battery characterized by using a material comprising a polyolefin resin as a main component and a cation exchange resin added thereto.