The battery is the primary reason that hampers a mass adoption of electric vehicles (EVs). Although lithium ion battery (LIB) is a preferred power source for EV, there is still a plenty of room to be improved for the cost, life and safety of the LIB in EV applications. Another important issue to be overcome for the EV battery is searching for an appropriate fast charge protocol to alleviate “range anxiety” for the driver of passenger EV and thus to enable a rapid growth of EV market. A short charge time is, however, reported to be achieved always at the expense of cycle life regardless of the charge techniques. It is, therefore, essential to find an optimized fast charge protocol that can balance fast charge and healthy cycling for the LIBs.

In this work, the thermal behaviors of LIB cell under various fast charge protocols are analyzed based on the two-dimensional modeling of the nonuniform temperature distribution in LIB cell during fast charge. The thermal modeling during fast charge is validated by the comparison of the modelling results with the experimental measurements using IR thermal images and thermocouples. The fast charge protocols are evaluated based on the peak temperature of LIB cell and the thermal imbalance within LIB cell during fast charge.

The maximum, average, and minimum temperatures obtained from the experimental measurements are compared with those predicted by the model in Fig. 1. The maximum, average, and minimum temperatures obtained from the experiment and modelling are in good agreement with each other at charge rate of 5C during CC-CV charging. Fig. 2 shows the temperature distributions based on the experimental IR image and the modeling for a 14.6 Ah LIB at an environmental temperature of 25℃ at charge time of 180, 480, 1140 s during CC-CV charging with CC charge at 5C. The overall temperature distributions obtained from the experiment agree well with those from the modeling in Fig. 2.