Silicon Graphite Composite Anode Degradation: Effects of Silicon Ratio, Current Density, and Temperature

Recently, a graphite–silicone (GrSi) composite anode has attracted a lot of attention due to its enhanced capacity and stability over pure Si anode. Herein, the abnormal behaviors and the degradation of the composite electrode during the repeated charging/discharging cycles are investigated. At each cycle, the capacity retention, Coulombic efficiency, irreversible, and differential capacity are analyzed to examine the contribution of each Gr and Si on the capacity. Generally, the composite electrodes are found to show a rapid initial decrease in capacity as the silicon ratio increases, indicating that silicone is the major contributor of the initial drop. Also, the capacity contribution of the graphite can also decrease rapidly for some conditions such as low temperature and high rate due to higher charge transfer resistance of the graphite. Interestingly, at certain conditions, the capacity decreases initially and recovers; differential capacity analysis revealed that this was due to the initial loss and recovery of graphite reactions. The degree of recovery decreased with increasing Si partly due to the higher resistivity of Si. Our findings could be useful for designing and operating composite electrodes with higher performance and stability.