Impact of cation substitution in NiCo2O4 spinel on morphology and electrochemical performance

Nanostructured NiCo2O4 spinel is the most appealing candidate to be used as the electrode for supercapacitors due to its significant merits such as eco-friendliness, low cost and easy availability. Introduction of a secondary metal cation into the host NiCo2O4 could provide more electroactive sites with rich redox chemistry. Herein we report the influence of cation (Zn/Mn) doping on the physicochemical and electrochemical properties of easily synthesized NiCo2O4 spinel. After being doped with Zn/Mn the morphology of NiCo2O4 was notably changed and specific capacitance of NiCo2O4 was greatly enhanced. Mn doped NiCo2O4 nanorod bundles store more internal surface charge than Zn doped NiCo2O4 flowers. A maximum specific capacitance of 1494 F/g was delivered by Mn doped NiCo2O4 nanorod bundles with a good rate capability (capacity retention of 64 % from 1 to 20 A/g) and excellent cycling stability (88.6% of initial value after the completion of 5000 cycles). An asymmetric device fabricated using Mn substituted NiCo2O4 as the positive electrode achieved an energy density of 12 Wh/kg at a power density of 427 W/kg and could efficiently light up a light emitting diode.