Abstract: Lithium-ion batteries working at low temperatures will inevitably experience cyclic aging, resulting in performance declines such as reduced battery capacity and increased impedance, which will exacerbate the risk of thermal runaway of the battery. In this study, a thermal runaway experiment platform was built to study the thermal runaway characteristics of lithium-ion batteries after cyclic aging at low temperature, and the effects of different aging degrees, charging states and coupling conditions on the thermal runaway characteristics of lithium-ion batteries were analyzed. It is found that under -10 ℃ low temperature environment, the time of thermal runaway explosion is advanced, the injection is more intense, and the temperature rise rate of the battery is more obvious, but the temperature on the upper part of the battery surface (near the pressure relief valve) decreases with the increase of the number of cycles. Since there is no jet port in the lower part of the battery, the heat accumulation causes the lower part of the battery to be slightly warmer than the upper part. At the same time, the evolution law of voltage and mass loss of the battery under different aging degree and charged state is given. This work helps to improve the understanding of thermal runaway characteristics of aging lithium-ion batteries, and provides theoretical basis and data support for the safety of lithium-ion batteries operating in low temperature environment.

Key words: lithium-ion battery, low-temperature environment, thermal runaway, charge-discharge rate, state of charge