Facile Fabrication of Multivalent VO_x/Graphene Nanocomposite Electrodes for High-Energy-Density Symmetric Supercapacitors

摘要

Supercapacitors have emerged as one of the leading energy-storage technologies due to their short charge/discharge time and exceptional cycling stability; however, the state-of-the-art energy density is relatively low. Hybrid electrodes based on transition metal oxides and carbon-based materials are considered to be promising candidates to overcome this limitation. Herein, a rational design of graphene/VOx electrodes is proposed that incorporates vanadium oxides with multiple oxidation states onto highly conductive graphene scaffolds synthesized via a facile laser-scribing process. The graphene/VOx electrodes exhibit a large potential window with a high three-electrode specific capacitance of 1110 F g(-1). The aqueous graphene/VOx symmetric supercapacitors (SSCs) can reach a high energy density of 54 Wh kg(-1) with virtually no capacitance loss after 20 000 cycles. Moreover, the flexible quasi-solid-state graphene/VOx SSCs can reach a very high energy density of 72 Wh kg(-1), or 7.7 mWh cm(-3), outperforming many commercial devices. With R-ct 0.02 Omega and Coulombic efficiency close to 100%, these gel graphene/VOx SSCs can retain 92% of their capacitance after 20 000 cycles. The process enables the direct fabrication of redox-active electrodes that can be integrated with essentially any substrate including silicon wafers and flexible substrates, showing great promise for next-generation large-area flexible displays and wearable electronic devices.