NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

摘要

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.