A facile strategy for the synthesis of graphene/V2O5 nanospheres and graphene/VN nanospheres derived from a single graphene oxide-wrapped VOx nanosphere precursor for hybrid supercapacitors

It remains a challenge to develop a facile approach to prepare positive and negative electrode materials with good electrochemical performance for application in hybrid supercapacitors. In this study, based on a facile strategy, a single graphene oxide-wrapped VO_x nanosphere precursor is transformed into both electrodes through different thermal treatments (i.e., graphene/VN nanospheres negative electrode materials and graphene/V₂O₅ nanospheres positive electrode materials) for hybrid supercapacitors. The conformally wrapped graphene has a significant influence on the electrochemical performance of VN and V₂O₅, deriving from the simultaneous improvements in electronic conductivity, structural stability, and electrolyte transport. Benefitting from these merits, the as-prepared graphene/VN nanospheres and graphene/V₂O₅ nanospheres exhibit excellent electrochemical performance for HSCs with high specific capacitance (83 F g⁻¹) and good long cycle life (90% specific capacitance retained after 7000 cycles). Furthermore, graphene/VN nanospheres//graphene/V₂O₅ nanosphere HSCs can deliver a high energy density of 35.2 W h kg⁻¹ at 0.4 kW kg⁻¹ and maintain about 70% high energy density even at a high power density of 8 kW kg⁻¹. Such impressive results of the hybrid supercapacitors show great potential in vanadium-based electrode materials for promising applications in high performance energy storage systems.

It remains a challenge to develop a facile approach to prepare positive and negative electrode materials with good electrochemical performance for application in hybrid supercapacitors.