Abstract:

To enhance the long-term stability and safety of lithium-ion batteries, a study on potential safety hazards caused by over-discharge was conducted. Aiming at the over-discharge/recharge phenomenon that the lithium-ion batteries may encounter in practical applications such as new energy electric vehicles and electrochemical energy storage, ternary lithium-ion batteries were examined. Through cycle tests and Hybrid Pulse Power Characteristic(HPPC) tests, adiabatic accelerating rate calorimetry was employed to investigate thermal runaway. The effects of over-discharge/recharge cycles on electrical characteristics—such as discharge capacity, DC internal resistance, and incremental capacity—as well as on the thermal runaway characteristic parameters under adiabatic conditions, were analyzed. The results show that over-discharge cycling accelerates battery capacity decay and increases internal resistance, with a particularly notable rise in DC internal resistance in the low state-of-charge region. However, after short-term cycling, prolonged resting allows partial capacity recovery. Over-discharge cycles also reduce the thermal stability of batteries, lower the self-heating onset temperature, and shorten the thermal runaway time compared to fresh batteries and normally cycled batteries, although the maximum thermal runaway temperature is relatively lower.

Key words: lithium-ion batteries, over-discharge cycles, thermal stability, discharge capacity(DC), thermal runaway