Rational Design of Ni Nanoparticles on N-Rich Ultrathin Carbon Nanosheets for High-Performance Supercapacitor Materials: Embedded-Versus Anchored-Type Dispersion

Highly dispersed Ni nanoparticles (NPs) and abundant functional N-species were integrated into ultrathin carbon nanosheets by using a facile and economical sol-gel route. Embedded- and anchored-type configurations were achieved for the dispersion of Ni NPs in/on N-rich carbon nanosheets. The anchored-type composite exhibited outstanding pseudocapacitance of 2200Fg(-1) at 5Ag(-1) with unusual rate capability and extraordinary cyclic stability over 20000 cycles with little capacitance decay. Aqueous asymmetric supercapacitors fabricated with this composite cathode demonstrated a high energy density of 51.3Whkg(-1) at a relatively large power density of 421.6Wkg(-1), along with outstanding cyclic stability. This approach opens an attractive direction for enhancing the electrochemical performances of metal-based supercapacitors and can be generalized to design high-performance energy-storage devices.