SUMMARY

Electrochemical energy storage devices are critical to the development of Electric Vehicles (EVs) and sustainable transportation. Electrochemical Capacitor (EC) is one of the potential energy sources for EVs due to its high power density and excellent cycling stability. However, ECs suffers from low energy density due to the surface-limited charge storage mechanism. In contrast, Lithium-ion batteries (LIBs) has high energy density but low power density and poor cycling stability. Therefore, research efforts have focused on developing electrode materials that have both high-enegy and high-power with cycling stability. In this thesis, we demonstrated the possibility of bridging the performance gap between the ECs and LIBs with redox-active organic molecule functionalized graphene electrode. We tested the functionalized graphene electrodes in both aqueous and gel electrolyte, showing high specific capacitance in both electrolytes. The electrode also showed good cycling stability in gel electrolyte. We also tested several quinone group molecule functionalized graphene electrodes, exhibiting the excellent specific capacitance of 511 F/g and great cycling stability in aqueous electrolyte.