Defect-rich carbon nanosheets promoting power density of lithium-ion capacitors in redox electrolyte system

The introduction of redox additives, for example lithium iodide into the catholyte of lithium-ion capacitors can achieve capacity matching between the cathode and anode through the additional capacity provided by the redox reaction. However, the relatively slow redox reaction rate exacerbates the issue of kinetic imbalance between the cathode and anode during charging and discharging process, resulting in reduced coulombic efficiency and power density of lithium-ion capacitors. Herein, we doped carbon nanosheets with NH 3 followed by high temperature treatment to obtain carbon nanosheets with rich defects. Theoretical calculations show that defect sites have a mild adsorption effect on iodide. Moreover, the electrochemical evaluation reveals that the defect structure can promote the redox reaction kinetics, thus increasing the electrochemical performance, especially power density of lithium-ion capacitors in the redox electrolyte system.