In situ synthesis of core-shell vanadium nitride@N-doped carbon microsheet sponges as high-performance anode materials for solid-state supercapacitors.

Vanadium nitride (VN) with high conductivity exhibits the potential promising as anode materials for supercapacitors, but VN suffered the obvious performance fading due to the dissolution of VN in aqueous electrolyte. In this work, we solve these problems through realizing 3D structural VN microsheets shelled with N-doped carbon layer (VN@NC) by introducing melamine as nitrogen source and PVP as carbon source. The as-prepared VN@NC electrode display high capacitance of 368 F g-1 and good rate property. A solid-state asymmetric supercapacitor (ASC) with NiCo2O4 nanowires as cathode materials and VN@NC as anode materials was fabricated. The ASC device exhibits the high energy density of 65.3 W h kg-1, and good cycling stability (92% capacitance retention) after 4000 cycles. Moreover, the ASC device shows good mechanical flexibility with negligible capacitance loss after 1000 bending cycles.