Electrodeposition of Ni(OH)2 Nanosheets on Activated Carbon-NiO Composites for Supercapacitor Applications

The growing electric automobile and portable electronics industries have stimulated increasing demand and boosted the consumption of high-performance energy storage materials. Herein, a precipitation-pyrolysis method was used to synthesize activated carbon (AC) supported NiO composites that serve as a substrate for the formation of Ni(OH)2 nanosheets (with a thickness of 13–20 nm) by electrodeposition for supercapacitor electrodes. It was found that pretreatment of the AC (or using graphite or another AC as an alternative) greatly affected the as-prepared electrode performance. The well-designed AC-NiO/Ni(OH)2 composite exhibits a high specific capacity of 748.8 C/g at 1 A/g and good cyclic stability (with a capacity retention ratio of 87.6% after 5000 charge–discharge cycles) in a three-electrode system, thanks to the unique structure and components involving a porous carbon skeleton, Ni0 and NiO species, and Ni(OH)2 nanosheets. The assembled asymmetric capacitor possesses a potential window of 1.45 V, an energy density of 30.0 Wh/kg at a power density of 145 W/kg (or 15.5 Wh/kg at 2000 W/kg), and good cyclic stability (with a capacity retention ratio of 92.6% after 5000 charge–discharge cycles at 2 A/g). The presented work provides a potential pathway for the rational design of high-performance electrode materials for electrochemical capacitors and/or energy storage devices.