Compound self-heating strategies and multi-objective optimization for lithium-ion batteries at low temperature

Rapid and effective battery preheating for thermal management is particularly significant to overcome the performance limitation of batteries and guarantee the efficient operation of electric vehicles in cold environments. A low-temperature compound self-heating (CSH) strategy integrating the inner-battery direct-current heating and outer-battery electric heating is proposed to enhance heating efficiency and shorten heating duration without the requirement of extra power supplies. Computationally efficient distributed thermal equivalent circuit models, to capture the temperature distribution within batteries, are developed and experimentally validated with good accuracy. Four typical CSH methods are systematically discussed and compared in terms of the heating rate, temperature uniformity, energy consumption, capacity fade, and fabrication and safety challenge. The CSH method with electric heaters installed on the largest battery surfaces is found preferable due to its relatively easy implementation and low safety risk, and slightly small temperature gradient within the battery. Three crucial yet competing objectives, the heating time, temperature gradient, and capacity fade, are formulated for the favorable CSH method, and the Pareto front is obtained using the multi-objective optimization algorithm. An optimal low-temperature CSH method is thus proposed, where the battery is heated from −30 °C to 2 °C within 62.1 s. Compared with the direct-current heating method, the proposed optimal CSH method strengthens the heating rate by 60.8%, reduces energy consumption by 54.8%, and relieves battery degradation by 45.2%.