The Characteristics of Thermal Runaway and Its Propagation in Large-Format LiFePO4 Batteries under Overcharging and Overheating Conditions

Abstract

Abstract LFP batteries are widely used in energy storage stations and electric vehicles, but their related fire incidents have not been remediated. In this paper, the TR/TRP characteristics of LFP batteries/modules under different heat dissipation conditions are investigated through experiments and simulations. In addition, the TRP behaviour of large-capacity prismatic LFP modules under different SOCs and TR trigger modes is investigated in detail. It is found that the heat dissipation significantly affects the maximum TR temperature of the LFP single battery under overheating and whether TR occurs under overcharging. Besides, whether improving the convection coefficient can prolong the TRP time of the LFP module under overheating is influenced by the thermal resistance value between adjacent batteries. Furthermore, the TRP behaviour of the LFP module is significantly influenced by the SOC and TR trigger mode. 100% SOC LFP modules have the most intense TRP behaviour under overheating, with the TRP time increasing from 140 s to 644 s as the battery SOC drops from 100% to 80%, and TRP being blocked as the battery SOC drops to 50%. The LFP module however does not undergo TRP under overcharging even in an open environment at 80 °C.