Abstract: To explore the thermal safety issues of lithium ion battery under the condition of overcharge, 18650 type ternary lithium ion battery was used as the research object, and the thermal safety comparative experiment of batteries with different SOC of single and cyclic overcharged under the same conditions was conducted. The thermal stability and the severity of the consequences of the single and cyclic overcharged battery were analyzed by the time of battery to reach the initial burst and thermal runaway, the surface temperature of two nodes, and the battery surface temperature peak. The research was to provide evaluation indicators for evaluating the thermal safety of lithium ion batteries under overcharge conditions, and provide technical support for the inspection management of equipment using lithium ion batteries in civil air transportation and the standardized development of the industry. The result showed that, compared with cyclic overcharged batteries, the initial burst time of single overcharged batteries is 20% earlier and the temperature rises by 8%, and thermal runaway time is 15% ahead. After comprehensive analysis of battery thermal runaway phenomenon, maximum temperature and mass loss, it is concluded that the thermal stability of lithium ion battery after cyclic overcharged is better than that of single overcharged battery, but the consequences of thermal runaway are more serious.

Key words: lithium ion battery, single overcharged, cyclic overcharged, thermal safety