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[0015] It is hence an object of the invention to provide a nonaqueous electrolyte secondary battery excellent in output characteristic such as larg
Problems solved by technology
However, when plural current collecting leads are connected to the electrodes as disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 11-317218 and 11-339758, the assembly procedure is complicated, and consequently, productivity of batteries is lowered.
In addition, when the battery is designed by reducing the thickness of the electrodes as in Jpn. Pat. Appln. KOKAI Publication No. 2002-110254, the occupying rate of current collectors in electrodes is larger, and the quantity of reaction substances such as active materials of electrodes is inevitably decreased.
This is significantly disadvantageous in terms of advance of larger
Method used
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EXAMPLE 1
[0154] A slurry was prepared by dissolving 91 wt. % of powder of lithium cobalt oxide (LiXCoO2; X being in a range of 03 in density.
[0155] A carbonaceous matter was prepared as powder of mesophase pitch carbon fiber heated at 3000° C. {the fiber diameter was 8 μm, the average fiber length was 20 μm, the aspect ratio was 0.4, the plane interval (d002) of (002) plane determined by powder X-ray diffraction was 0.3360 nm, and the specific surface area by a BET method was 1 m2 / g}. A slurry was prepared by dissolving 93 wt. % of the carbonaceous matter and 7 wt. % of polyvinylidene fluoride (PVdF) as a binder in N-methyl-2-pyrrolidone (NMP) as a solvent. The slurry was applied on both sides of a current collector composed of a copper foil of 12 μm in thickness, dried and pressed to thereby fabricate a negative electrode of 1.35 g / cm3 in filling density.
[0156] A separator was prepared by using a polyethylene porous film having thickness of 25 μm, heat shrinkage of 20% in 1 hour...
Example
EXAMPLES 2 to 9
[0161] Eight types of cylindrical lithium ion secondary batteries were manufactured in the same manner as in Example 1, except the PCT element having the shape, depth, width, and opening area of the notch shown in Table 1 was used.
Example
COMPARATIVE EXAMPLES 1, 2
[0162] Two types of cylindrical lithium ion secondary batteries were manufactured in the same manner as in example 1, except that the PCT element having the shape, depth, width, and opening area of the notch shown in Table 1 was used.
[0163] The obtained secondary batteries in Examples 1 to 9 and Comparative examples 1 and 2 were charged at a charging current of 2100 mAh up to 4.2V in 3 hours, and discharged to 3V at 2100 mA, and the battery capacity (1 C capacity) was measured. Then, after charging at a charging current of 2100 mAh up to 4.2V in 3 hours, and discharging to 3V at 8400 mA, the battery capacity was measured, and the capacity ratio to 1 C capacity (capacity retaining rate) was calculated.
[0164] Further, five cells of each secondary battery were prepared, the secondary batteries were evaluated by oven test in a thermostatic oven, by charging at charging current of 2100 mAh up to 4.2V in 3 hours, and heating to 200° C. at a heating speed of 10°...
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Abstract
The invention provides a nonaqueous electrolyte secondary battery excellent in output characteristic such as large current discharge or pulse discharge in ordinary use, high in safety by preventing destruction due to suppression of current in an abnormality such as external short-circuiting, and further large in capacity. The nonaqueous electrolyte secondary battery comprises an external can opened at one end thereof, an electrode assembly contained in the external can, and comprising a negative electrode, a separator and a positive electrode, a nonaqueous electrolyte contained in the external can, and a sealing lid group tightly sealed at the opening of the external can by way of an insulating member, wherein the sealing lid group includes an intact plate-like PTC element having a fragile portion to be easily broken due to elevation of internal pressure by gas generation.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This is a Continuation Application of PCT Application No. PCT / JP2004 / 004846, filed Apr. 2, 2004, which was published under PCT Article 21(2) in Japanese. [0002] This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-102021, filed Apr. 4, 2003, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to a nonaqueous electrolyte secondary battery. [0005] 2. Description of the Related Art [0006] Recently, along with a downsizing trend of electronic appliances such as cellular phones and portable personal computers and an increase in demand for them, there is a mounting demand for higher performance in secondary batteries used as a power source of these electronic appliances. To meet such a demand, nonaqueous electrolyte batteries using a material, such as a carbon material, c...
Claims
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