LAUSR

The rational design of composite electrodes that may take full advantage of pseudocapacitive metal oxides and graphene is still challenging. Herein, nickel cobaltate (NiCo2O4) nanoparticle-anchored crumpled graphene microspheres (CGMs) were fabricated through a simple spray-assisted self-assembly process and used as a composite electrode for aqueous supercapacitors. Due to the porous spherical architecture and well-dispersed NiCo2O4 nanoparticles on graphene, the NiCo2O4/CGM electrode displays ideal electrochemical performance, including a specific capacitance of 369.8 F g-1 (at 1 A g-1), good rate performance of 85% capacitance retention even at 10 A g-1 and intriguing cycling stability. An aqueous asymmetric supercapacitor (ASC) with an operating voltage of 1.6 V was then assembled using the NiCo2O4/CGM composite and nitrogen-doped CGM (N-CGM) as the positive and negative electrodes in KOH electrolyte, respectively. The ASC device exhibited an excellent energy density of 24.7 W h kg-1 at a power density of 799.6 W kg-1, and an ultralong cycling life with a capacitance retention of 85% after 50 000 cycles. The satisfactory electrochemical performance and ultralong cycling stability indicate that the NiCo2O4/CGM electrode has promising applications in advanced supercapacitors.