The fast-charging properties of micro lithium-ion batteries for smart devices

Nowadays fast charging has become an important characteristic of lithium-ion batteries (LIBs), so is of great significance to study the fast charging of LIBs. However, previous research of fast charging has focused more on high energy density LIBs, due to the growing demand for electric vehicles. Herein, the fast-charging properties under ambient temperature and high temperature for (60 mAh LiCoO₂/graphite batteries) micro-LIBs are firstly investigated. The electrochemical test results reveal that this kind of battery possesses 4C fast-charging capability. Further increase in charging rate will accelerate battery capacity decay without reducing charging time. Although high temperature increases the fast-charging capacity and shortens the fast-charging time to 10 min at 6C under 65 °C, increase of side reactions resulted from high temperature also exacerbates the performance of battery. Post-mortem analysis further demonstrates the structural changes of cathode and anode materials, residual lithium deposits, peeling of graphite and the incrassation of the solid electrolyte interphase (SEI), especially under high temperature, which lead to fast -charging performance degradation. This work reveals the possible causes of micro battery performance deterioration during fast charging under ambient and high temperature and provides some reference for designing micro-LIBs with fast -charging properties.