N-doped and oxygen vacancy-rich NiCo2O4 nanograss for supercapacitor electrode

Transition-metal oxides are a class of promising pseudo-capacitive materials for high energy density supercapacitors, while their low intrinsic conductivity, limited electrochemical sites and remarkable volume expansion deteriorate the electrochemical properties. Herein, we develop a facile synchronization strategy to prepare a N-doped and oxygen vacancy-rich NiCo2O4 microporous nanograss (N-Ov-NCO MiNG), with adjustable superficial nanoporous architecture and electronic structure. Because of the instructive synergy of doping, defect, and surface-engineering achieved by one-step plasma activation, the optimum electrode (N-Ov-NCO MiNG-15) for supercapacitors exhibits significantly enhanced electrochemical properties, like an ultra-high specific capacitance of 2986.25F g-1 at 1 mA cm-2 and outstanding cyclic stability with a capacitance retention of 96.5% after cycling for 12,000 times. In addition, an aqueous asymmetric supercapacitor (ASC) device, assembled with the N-Ov-NCO MiNG-15 as the cathode and commercial activated carbon (AC) as the anode, shows an extremely high energy density of 103.2 Wh kg- 1 at the power density of 748.3 W kg-1, superior to most state-of-the-art supercapacitors and thus exhibiting a great potential in practical applications.

Automated summary

Through one-step plasma activation, a NiCo2O4 microporous nanograss with nitrogen doping and oxygen vacancy-rich was successfully prepared as a high-performance electrode for supercapacitors. The electrode showed excellent cyclic stability and high specific capacitance, leading to a significantly enhanced energy density. It can also be used in aqueous asymmetric supercapacitor devices, demonstrating extremely high energy density and power density.