Research on the Improvement of Lithium-Ion Battery Performance at Low Temperatures Based on Electromagnetic Induction Heating Technology

As the major power source for electric vehicles (EVs), lithium-ion batteries (LiBs) suffer from the degradation of technical performance and safety at low temperatures, which restricts the popularization of EVs in frigid regions. Thus, this study developed an extremely fast electromagnetic induction heating system in order to improve the poor performance of LiBs in cold weather. An electrochemical–thermal coupling model (ETCM), validated against the experimental results of charge and discharge, which successfully predicted LiB voltage, temperature, and other physical characteristics at various ambient temperatures, was established in COMSOL Multiphysics 6.0 as a development tool for evaluating the heating effect of the system. When the copper coil is subjected to a SAC (sinusoidal alternating current) of 8 A and 50 Hz, the LiB can be heated from 243.15 to 293.15 K within 6 min with an instantaneous temperature increase rate of 0.263 K/s and a homogeneous temperature distribution. The results of the capacity calibration, cyclable lithium detection, and HPPC simulation show that the heating method can visibly increase the Li+ concentration inside the active particle, and there was only a tiny concentration gradient on the surface of the particle. In addition, the internal resistance was approximately a quarter of that without heating; therefore, both the discharge energy and specific power boost were two times higher than the original level. Compared to the normal charge–discharge cycles at 293.15 K, the capacity retention of the LiB only decreased by 0.23% after 60 consecutive heating cycles, so the heating method can balance the temperature rise, work capacity, and LiB health. Furthermore, the improvements in the thermal insulation condition and material thermal conductivity are two feasible ways to optimize the temperature-increase effect.