Study on Safety Characteristics of External Short-circuit for Power Lithium-ion Battery

The abuse behavior of external short-circuit are researched based on the cylindrical power lithium-ion batteries with high specific energy in this paper. The effect of SOC(State of Charge), aging degree and electrical connection on the safety characteristics are considered through tests and discussions. And short-circuit current, terminal voltage and temperature characteristics are used to compare and study the impact on above factors. Short-circuit current rises sharply and terminal voltage decreases rapidly at the moment of external short-circuit. Moreover, the rate of temperature change and temperature go up quickly at tens of seconds after the occurrence of external shortcircuit. The temperature of positive electrode is the highest among the three measure points of temperature. Although the external short circuit does not cause thermal runaway, several phenomena such as spark sputtering, electrolyte leakage, and little release of smoke are observed. The safety characteristics of external shortcircuit do not depend on SOC and the samples with lower SOC exhibit higher temperature. Temperature and rate of temperature change are determined by both of short-circuit current and its duration time. The duration time of short-circuit current increases significantly and the maximum temperature of battery surface rises as the increase of aging degree. The short-circuit current of battery module with parallel connection is obviously larger than cell and battery module with serial connection, but its duration time of short-circuit current is relatively smaller. The temperature of battery module with serial connection changes more severely so that it shows weaker thermal safety. The external short-circuit behavior of battery will result in heat accumulation in the environment with poor heat dissipation for actual battery pack, which may lead to risk of thermal runaway.