Low-temperature heating method for lithium-ion batteries using alternating current: balancing temperature rise rate and capacity degradation

Lithium-ion batteries suffer from severe performance degradation in low-temperature environments, driving an urgent need for the advancement of efficient low-temperature heating technologies in battery systems. This study proposes a bidirectional alternating current (AC) heating strategy to enable rapid low-temperature preheating of lithium-ion batteries while mitigating capacity degradation. Firstly, an electrochemical-thermal coupling model, incorporating anode solid electrolyte interphase (SEI) growth and lithium deposition mechanisms, is developed and experimentally validated. Subsequently, the effects of waveform type, current effective value (I _RMS), and frequency on heating performance are systematically investigated, along with their effects on the battery capacity degradation caused by SEI growth and lithium deposition. Based on the above research, an asymmetric AC heating strategy with a specific charging-discharging current ratio (β _ratio) is proposed and experimentally validated. The results demonstrate that the proposed strategy outperforms the symmetric heating method in both temperature rise rate and capacity degradation suppression. At SOC = 50 %, the proposed strategy with a β _ratio of 1:9 increases the temperature rise rate by 67 % and reduces capacity degradation by 29 % compared to the symmetric method (i.e., β _ratio = 5:5). Further verification through min–max normalization confirms that the composite score index (CSI) for the asymmetric heating strategy (β _ratio = 1:9) reaches 0.928, significantly higher than the conventional symmetric method (which scores 0.03). Moreover, compared with other four typical heating methods based on excitation currents, this strategy still maintains the highest CSI, providing universal insights for the development of battery low-temperature heating technologies.