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 2200 F g−1 at 5 A g−1 with unusual rate capability and extraordinary cyclic stability over 20 000 cycles with little capacitance decay. Aqueous asymmetric supercapacitors fabricated with this composite cathode demonstrated a high energy density of 51.3 Wh kg−1 at a relatively large power density of 421.6 W kg−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.