Research on Self-Heating and Fast Charging Coupling Method of Lithium-Ion Batteries at Low Temperatures

Lithium-ion batteries (LIBs) are susceptible to lithium dendrite formation during fast charging at low temperatures, which poses a risk of thermal runaway. To address the challenge of fast charging LIBs in low-temperature environments, this paper proposes a self-heating and charging coupling circuit topology and a corresponding charging strategy. The paper systematically investigates the charging speed, energy conversion efficiency, and cycle life during charging processes. Using the control variable method, the effects of initial state of charge (SOC), pulse frequency, and charging current on the low-temperature charging performance of LIBs are analyzed. Furthermore, the advantages of the proposed coupling method are validated through a comparison with the preheating before charging method. The results show that the charging speed and energy conversion efficiency are negatively correlated with the initial SOC, positively correlated with the charging current, and are optimized at medium frequencies. Compared to the preheating method, the coupling method achieves a 41.8% increase in charging speed on average. Additionally, low-temperature charging cycle experiments demonstrate that the coupling method has a minimal impact on battery capacity and is less prone to polarization, with an average state of health (SOH) decrease of only 2%.