Nest-like V3O7 self-assembled by porous nanowires as an anode supercapacitor material and its performance optimization through bonding with N-doped carbon

Abstract

Vanadium oxides (such as V 2 O 5 , V 2 O 3 and VO 2 ) hold great promise as electrode materials for energy storage due to their high electrochemical activity, low cost and environmental benignity. However, V 3 O 7 is rarely investigated as a supercapacitor material. Herein, nest-like V 3 O 7 self-assembled by porous V 3 O 7 nanowires was fabricated. The energy storage mechanism of V 3 O 7 was investigated at different reaction potentials. It was found that V 3 O 7 was converted to V 6 O 13 at a potential of -0.6 V, and became V 2 O 5 at 0.2 V. Additionally, an in situ photopolymerization method was introduced to synthesize V 3 O 7 @polypyrrole (PPy) and then, V 3 O 7 nanowires coated with a layer of N-doped carbon were obtained after calcination to enhance the performance in terms of capacitance and stability. This unique N-doped carbon coated nest-like V 3 O 7 (NC-V 3 O 7 ) exhibited a high specific capacitance of 660.63 F g -1 at a current density of 0.5 A g -1 and even reached 187.72 F g -1 at a high current density of 50 A g -1 . According to this investigation, the superior performance of NC-V 3 O 7 is attributed to the synergy between N-doped carbon and V 3 O 7 , that is, the unique three layer structure (C bonded both to V and N) stabilized V 3 O 7 and supported high-speed ionic and electronic transmission channels. Finally, full symmetric (NC-V 3 O 7 //NC-V 3 O 7 ) and asymmetric (MnO 2 nanosheets//NV-V 3 O 7 ) supercapacitor devices were assembled and showed higher power and energy density than those of related reports