Capacity Fading Mechanisms of Submicron-Sized Silicon Negative Electrode for Lithium Ion Batteries

Silicon, due to its large specific capacity, is regarded as one of the most promising negative electrode materials for lithium ion batteries despite critical drawbacks associated with large volume change upon lithiation/de-lithiation. Although nano-sized silicon particles have been employed to mitigate the failures and related techniques have achieved considerable improvements, current materials do not meet the demand of commercial applications. Thus, a systematical approach to elucidating failure mechanisms is necessary to further improve electrochemical performances of the silicon electrode. Here, the evolution of voltage profiles recorded during cycling was thoroughly analyzed and thereby the failure mechanisms are proposed. The main failure mechanism of the silicon electrode is related to an inability to fully de-lithiate due to resistance increases during discharging, which are mostly contact and SEI resistance. The capacity retention was significantly improved by lowering discharge cut-off voltage and by introducing electrolyte additives, in which reduce the resistances during discharging.