US 6,713,217 B2 · Nonaqueous electrolyte secondary battery with a polyolefin microporous membrane separator

Abstract

The present invention relates to a nonaqueous electrolyte secondary battery, and more particularly to its separator, and it is an object thereof to prevent electrolyte leakage accident due to elevation of cell internal pressure even if the cell is exposed to high temperature without sacrificing the cell capacity. To achieve the object, by using the polyolefin group separator large in endothermic calorie per unit area by the heat of fusion in a temperature range of 70 to 150° C., and selecting appropriate graphite powder for negative electrode and organic solvent in nonaqueous electrolyte, the electrolyte leakage accident can be successfully eliminated by suppressing the reaction between the cell active substance and organic solvent, thereby suppressing elevation of cell internal pressure.

Claims12

Dependent claims

A nonaqueous electrolyte secondary battery comprising:

a positive electrode comprising a positive active substance;
a separator comprising a polyolefin group microporous membrane of 15 to 30 μm in thickness, with an endothermic calorie per unit area by the heat of fusion of at least 0.07 cal/cm2 in a temperature range of 70 to 150° C.;
and
a negative electrode comprising a carbon material which is at least one of artificial graphite powder or natural graphite powder, the carbon material having a plane interval (d002) of (002) plane by X-ray diffraction of less than 3.380 A and a specific surface area by BET method of 2.0 m2/g or more and less than 8.0 m2/g;
wherein said separator absorbs heat generated by said negative electrode.

2 more elements

Dependencies are inferred from the claim text.

Nonaqueous electrolyte secondary battery with a polyolefin microporous membrane separator

Life of this patent

Nonaqueous electrolyte secondary battery with a polyolefin microporous membrane separator

Life of this patent

Abstract

Claims12