Degradation and safety performance of lithium-ion cells under high-rate charging/discharging scenarios

Given the increasing popularity of high-rate charging and discharging for lithium-ion cells, this research aims to investigate the degradation and safety performance of these cells under high-rate scenarios. The study considers high rates including 4C, 6C, 8C, and 10C. The results show that high-rate charging and discharging leads to significant degradation of the cells, with the degradation rate linearly declining with the charging/discharging rate. Furthermore, cells that undergo long-term high-rate charging and discharging exhibit worsened safety performance at elevated temperatures, and this severity increases with the charging/discharging rate. It is also found that charging and discharging have different effects on the thermal runaway behaviour of cells when subjected to over-heating. Charging causes thermal runaway to occur much earlier than discharging, likely due to the difference in stored energy. Additionally, the intensity of thermal runaway is more severe during charging. Compared to the reference, high-rate charging deteriorates the safety features of cells, while high-rate discharging suppresses thermal runaway. Discharging has a more noticeable impact on thermal runaway. Eventually, cell’s state of charge is proved to be an especially vital factor determining the thermal runaway characteristics of cells.