Investigation of novel pulse preheating strategies for lithium-ion batteries at subzero temperature based on a multi-level CFD platform

Warming up lithium-ion batteries from cold environments to room temperature rapidly and safely is the key to popularizing battery electric vehicles in cold regions. Pulse preheating technology is an effective internal heating method while facing challenges such as low heating rate, high energy consumption, and risk of over-charging or discharging. Here, for the first time, a multi-level electrochemical-thermal coupling model is developed on an open-source CFD platform. Based on this model, we perform comprehensive simulations for the pulse heating process with various parameters and strategies from plate level to cell level to module level. In addition, two innovative heating strategies, namely varied rate pulse and hybrid pulse, are proposed, where the latter integrates the pulse heating and electric heating. Our main results show that the proposed hybrid pulse strategy can provide cells with an over 2.5 times faster heating rate from -20 degrees C to 0 degrees C and save nearly 60 % energy consumption compared to the single pulse heating at 6 C-rate, exhibiting a great prospect in circumventing the low-temperature effect. Besides, the internal temperature difference can be controlled. A high pulse frequency is suggested to achieve better temperature consistency within cells and avoid noticeable changes in the cell internal physical fields.