LAUSR

Abstract 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.