| abstract |
(57) [Summary] [PROBLEMS] Lithium-ion secondary batteries may run out of heat in abnormal conditions. Particularly, when thermal decomposition of the positive electrode active material starts due to an increase in battery temperature, the release of oxygen accompanying the decomposition causes the battery to run out of power. There is a problem that thermal runaway is promoted. SOLUTION: The safety in an abnormal state can be secured by selecting a positive electrode active material having an exothermic peak attributed to thermal decomposition of 270 ° C. or higher by DSC measurement. |