Ultra-high rate capability of nanoporous carbon network@V2O5 sub-micron bricks composite as a novel cathode material for asymmetric supercapacitors
A green biomass-derived nanoporous carbon network (NCN) is prepared and integrated with V2O5 sub-micron bricks (SMBs). The large surface area and high pore volume of NCN not only can provide abundant sites for electrochemical reactions, but also stabilizes the structure of V2O5 SMBs. The NCN@V2O5 SMBs composite, acting as a novel cathode material, delivers a high areal capacitance of 786 mF cm‒2 at 0.2 mA cm‒2 and superior cycle stability with an 89.5% capacitance retention after 5000 cycles. Besides, the electrode achieves an ultra-high rate capability (82% capacitance retention as the current density increases from 0.2 to 5 mA cm‒2) since the contribution from non-diffusion-controlled process is estimated as high as 95.5%–98.5% according to the kinetic analysis. Besides, the micropores are more favorable than the mesopores at lower current densities (0.2‒2 mA cm‒2), while the contribution of external surface area becomes more significant for current densities higher than 2 mA cm‒2. Moreover, an asymmetric supercapacitor assembled using this cathode and the NCN anode shows superior electrochemical properties, such as wide operating voltage, long cycle life and large energy density (72.2 μWh cm−2). The excellent electrochemical features and good eco-friendliness confirm the potential of NCN@V2O5 SMBs for supercapacitors.