Transient thermal behavior of internal Short-circuit in Lithium Iron Phosphate Battery

Thermal safety is the most important issue in Lithium Iron Phosphate (LiFePO₄) battery applications because of the large amount of energy stored inside them and also because of their great sensitivity to the conditions in which these batteries are used. A large part of thermal damages caused by LiFePO₄ battery is associated with short circuit. In this paper, a Multi-Scale Multi-Domain model, which has a high calculation speed and relatively accurate results to quickly respond to the instantaneous thermal abuse condition, is developed to predict internal short circuit (ISC) thermal behaviors of commercial LiFePO₄ battery during a discharging process. An 8-order polynomial fitting parameter for function U and a 5-order one for function Y are employed in this model. Also, cell pouch of the LiFePO₄ battery as a thickness thermal resistance which has a natural convection boundary condition is taken into account. Simulation results on positive electrode voltage and temperature performances show good agreement with the experimental data. The influences of short-circuit position, short-circuit resistance and discharge rate on the maximum temperature of the battery cell shortly after short circuit are investigated, respectively. The duration time right after short circuit happens to reach the maximum temperature on the short-circuit location and the value of the maximum temperature are focused on, respectively. The simulation results show that, the location of short-circuit does affect the value of maximum temperature, but this effect is not obvious; however, the short-circuit resistance has obvious influence on the time and the value of the maximum temperature at the short-circuit spot; additionally, the effect of discharge rate on the value of maximum temperature shows a linear downward trend, the smaller the short-circuit resistance value is, the greater the slope of the curve is.