Ultrahigh Specific Capacitances for Supercapacitors Achieved by Nickel Cobaltite/Carbon Aerogel Composites

Nickel cobaltite, a low cost and an environmentally friendly supercapacitive material, is deposited as a thin nanostructure of 3–5 nm nanocrystals into carbon aerogels, a mesoporous host template of high specific surface areas and high electric conductivities, with a two‐step wet chemistry process. This nickel cobaltite/carbon aerogel composite shows ultrahigh specific capacitances of around 1700 F g^?1 at a scan rate of 25 mV s^?1 within a potential window of ?0.05 to 0.5 V in 1 M NaOH solutions. The composite also possesses an excellent high rate capability manifested by maintaining specific capacitances above 800 F g^?1 at a high scan rate of 500 mV s^?1, and an outstanding cycling stability demonstrated by a negligible 2.4% decay in specific capacitances after 2000 cycles. The success is attributable to the fuller utilization of nickel cobaltite for pseudocapacitance generation, made possible by the composite structure enabling well exposed nickel cobaltite to the electrolyte and easy transport of charge carriers, ions, and electrons, within the composite electrode.