Theoretical and numerical analysis for thermal runaway propagation within a single cell

Abstract

In this work, a coupled reaction-heat conduction model is developed to describe battery thermal runaway propagation within a single cell. By nondimensionalizing the governing equation and exploiting the largeness of a dimensionless parameter β, analytical solutions for the reaction front propagation speed are obtained based on asymptotic analysis, as a function of both β and dimensionless temperature θu. Numerical solution of the model is obtained using the phase portrait and the heteroclinic orbit to further justify the analytical results, where satisfactory agreement is achieved specially for large β. This solution can be applied to a wide range of battery system parameters, including thermal diffusivity, exothermicity, activation energy, reaction order as well as the ambient temperature. It is shown that the thermal runaway propagation speed decreases with increasing β, and increases with battery temperature. Also, thermal structure of reaction front is compared among different β and θu, showing thinner reaction front for faster propagation waves with smaller β and larger θu. Lastly, by adopting battery parameters from the literature in the analytical formula, thermal runaway propagation speed is estimated in a typical condition. The results can provide useful insights into battery thermal runaway propagation and its prediction.