The Power-Energy Coupling Effect of Mixed Hard-Carbon/Graphite Anode

Abstract

As the anode materials of lithium-ion battery, the hard carbon has the higher power performance while the graphite has the higher energy performance, respectively. In this work, novel mixed hard carbon/graphite anodes are presented showing the coupling effect of power and mixed anodes was investigated at the varying charging rates, showing the tunable behaviors dependent on the hard carbon/graphite ratios. By studying the specific capacity evolution in different split potential ranges, we found that the mixed anodes with a higher proportion of hard carbon were advantageous when working in the cut-off potential greater than 0.10 V. The electrochemical impedance spectroscopy was measured at various anode potentials, which depicted the evolution of cell resistance with the state of charge. With the aid of electrochemical impedance spectroscopy, we found that the capacity evolution with mixed ratio is attributed to the lithiation-level induced difference of charge transfer resistance and Warburg resistance. A coupling effect was discovered showing a great potential in balancing the power-energy performance of mixed anode by simply controlling the ratio of hard-carbon/graphite.