N-functionalization and defect engineering in ZnCo2O4 nanosheets boosted the performance of Zn-ion hybrid supercapacitor

Transition-metal oxides are a class of promising pseudocapacitive materials for high energy density supercapacitors, while their low intrinsic conductivity and remarkable volume expansion deteriorate the electrochemical properties. Herein, we develop a binder-free mesoporous architecture supported on a carbon cloth (CC) substrate based on the nitrogen (N)-doped and oxygen vacancy (Ov)-rich zinc cobalt oxide nanosheets (denoted by N-Ov-ZCO@CC). Because of the instructive synergy of doping, defect, and surface engineering achieved by N-functionalization, the N-Ov-ZCO@CC exhibits significantly enhanced electrochemical properties. The N-Ov-ZCO@CC single electrode exhibited a high capacitance of 2166.4 F/g at 1 A/g with superb rate-capability (91.2% at 20 A/g) and superior cycling stability of 98.99% up to 5,000 cycles. In addition, a zinc-ion hybrid supercapacitor (ZHSC) device, assembled with the N-Ov-ZCO@CC as the cathode and Zn-foil as the anode, shows a high energy density of 95.35 Wh/kg at the power density of 10,008 W/kg, superior to most state-of-the-art ZHSCs. This work provides an effective strategy for constructing multifunctional electrochemical energy materials for ZHSCs.