A facile strategy for the synthesis of graphene/V 2 O 5 nanospheres and graphene/VN nanospheres derived from a single graphene oxide-wrapped VO x 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/V 2 O 5 nanospheres positive electrode materials) for hybrid supercapacitors. The conformally wrapped graphene has a significant influence on the electrochemical performance of VN and V 2 O 5 , 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/V 2 O 5 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/V 2 O 5 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.