1. INTRODUCTION
LIBs have played a significant role in electric vehicles (EVs) and become the first choice due to their high energy density, less pollution, and low self-discharge. Accompanying the development of EVs and the wild utilization of LIBs, researchers have devoted themselves to the battery management system (BMS), such as battery pack equalizers [1], fault diagnostics [2], and fast charging. Moreover, fast charging is considered an important technology of EVs. Whereas, the long charging time of LIBs hinders the further development of EVs [3]. For further development and more widely applied, it is essential to reduce charging time, with the same or even larger energy density. Currently, the widespread charging method is the constant-current constant-voltage (CC-CV) charging protocol [4], where con- stant current ranges from 0.5C to 2C. Depending on the value of constant current, the charging time varies from 50 mins to 120 mins. Through the effect of various researchers, many fast-charging methods have been proposed, such as multi-stage current charging (MSCC) protocol [6]. D. Ji et al. [7] compared differences in battery performance under different charging strategies and selected three optimal charging strategies with significant advantages over conventional charging strategies. Meanwhile, Yang et al. [8], came up with the extreme fast charging (XFC), where they preheated LIBs to 60°C and set the charging current at 6C. The LIB can be fully charged within 10 mins. But this method requires a special battery structure and the LIB may be in a dangerous situation without heat dissipation equipment and conditions with good performance.