Numerical modeling on thermal runaway triggered by local overheating for lithium iron phosphate battery

Abstract

The popularization of electric vehicles is no longer a speculation thanks to the advancement of the lithium-ion battery. However, safety issues prevent a larger-scale application of lithium-ion batteries. In energy storage industry, thermal runaway is the direct cause of fire and explosions. The thermal runaway numerical model attempts to unveil the mechanism of thermal runaway triggered by local overheating in this work, which is distinct from accelerating rate calorimeter tests or oven tests. The model is based on the energy conservation equation, and the source term of which is modeled by the empirical Arrhenius equations. Further on, the results of the numerical model are validated by experiments. Based on the calculated analysis on the heat contribution to the thermal runaway, the heat contribution of anode-electrolyte reaction is up to 63.8% of the total heat, and internal short circuit is responsible for a little proportion of total heat generation during thermal runaway which is contrary to the general thoughts, yet still a crucial inducement of chain reactions. The results also confirm the conclusion that enhancement of heat dissipation condition of battery can retard thermal runaway progress and reduce the maximum thermal runaway temperature. In addition, interior dynamic temperature distribution of the battery can be achieved, and characteristics of local overheating are compared with those of oven tests, noteworthy temperature difference in local overheating occasion is highlighted.