Segmented bi-material electrodes of activated carbon and LiMn2O4 for electrochemical hybrid storage devices: Effect of mass ratio and C-rate on current sharing

The performance of segmented bi-material electrodes consisting of an activated carbon and LiMn2O4 was investigated as a function of the relative amount of the components for full slow discharge at C/5. By means of a segmented current collector the contribution of each component to the overall current has been monitored. The potential profiles for the constant current discharges showed a monotonous transition from pure capacitive behavior of the activated carbon to battery behavior of pure LiMn2O4 for increasing amounts of LiMn2O4 in the segmented bi-material electrode. Correspondingly, the current sharing measurements have shown a decreased contribution of the activated carbon to the overall current. The effect of the C-rate up to 20C and pulse discharge at 25C was investigated for a segmented bi-material electrode with a relative amount of activated carbon of 72% by weight. The current sharing showed an increased contribution of the activated carbon to the overall current at high C-rate and during pulse discharge. Moreover it could be demonstrated that the battery material recharges the capacitive material subsequent to the discharge pulse.