A study of the capacity fade of a LiCoO2/graphite battery during the temperature storage process at 45 °C under different SOCs.

Abstract

Lithium-ion batteries with lithium cobalt oxide (LiCoO2) as a cathode and graphite as an anode are promising energy storage systems. However, the high-temperature storage mechanism under different states of charge (SOCs) conditions in batteries remains inadequately elucidated, and a clear storage policy has yet to be established. This study investigates and compares the capacity decay mechanism of a 63 mA h LiCoO2/graphite battery at 45 °C under various SOCs (100%, 75%, 50%, 30%, 0%), while also analysing the underlying reasons for this decay. The exhibited capacity recovery rates under 30% SOC and 100% SOC were significantly higher compared with those of the 50% and 75% SOC levels. Additionally, an analysis was conducted on battery storage under 0% SOC conditions, revealing its unsuitability for storage. By disassembling and analysing the batteries after storage, it was found that the dead lithium (Li) and cobalt (Co) in the anode gradually increased with the extension of storage time when stored under the same SOC. Finally, storage schemes under different SOCs are proposed, providing valuable suggestions for battery storage.