A model for the heat generation rate of lithium-ion battery for electric vehicles

Firstly with consideration of the spatial variation of parameters such as reaction current density and active material concentration in the electrodes of Li-ion battery, a mathematical model for the heat generation rate inside battery is established. Then a simulation on heat generation rate under different charge and discharge currents and SOCs is conducted. The results indicate that both generation rates of reversible heat (RH) and irreversible heat (IH) increase with the increase in charge and discharge currents. And the SOC change mainly affects the generation rate of RH but has no significant influence on the generation rate of IH. Under the same SOC and current, the generation rate of IH during charge and discharge are same with both releasing heat; while for RH, the generation rates are also equal in charging and discharging, but it absorbs heat during charging and releases heat during discharging. Finally, the transient temperatures of battery during constant current charging, constant current discharging and alternate charging-discharging are measured on Arbin bench and compared with corresponding simulated data. The results show that the model for heat generation rate can well reflect the dynamic change of battery temperatures. The RH has larger effects on battery temperatures during sustained charging or discharging, in particular, with smaller current rate; but it has no apparent effects on battery temperatures during alternate charging and discharging around certain SOC.