Thermal regulation and electrochemical safety optimization of lithium-ion batteries during low-temperature fast charging

Low-temperature fast charging of lithium-ion batteries (LIBs) is limited by the coupled evolution of internal heat generation, temperature recovery, electrochemical polarization, and lithium-plating risk. To address this issue, this paper proposes a thermally regulated fast-charging strategy based on an electrochemical-thermal coupled (ETC) model and a lithium-plating suppression criterion. In the ETC model, the heat generated by polarization, ohmic resistance, and reversible entropy effects is calculated from the electrochemical processes and coupled with a three-dimensional thermal model to describe the transient thermal response. Based on the anode-potential criterion, temperature- and state of charge (SOC)-dependent safe current boundaries are established for bidirectional pulse heating and multi-stage constant-current (MSCC) charging. A cyclic heating-charging strategy is then developed to improve low-temperature current acceptance while maintaining electrochemical safety. The effects of switching temperature and the number of heating stages on charging time, energy consumption, temperature evolution, and maximum achievable SOC are systematically investigated. Furthermore, a hybrid particle swarm optimization-genetic algorithm (PSO-GA) is employed to optimize the switching thresholds. The optimized single-stage heating strategy increases the battery SOC from 10 % to 96.5 % within 42.78 min with an energy consumption of 15.57 Wh, while the optimized two-stage heating strategy reaches 95.2 % SOC within 51.59 min with an energy consumption of 15.28 Wh. These results provide a thermally guided pathway for safe and efficient low-temperature fast charging of LIBs.