Nanostructured Fe-substituted NiCo2O4@NiMnCo-LDH ternary composite as an electrode material for high-performance supercapacitors

An essential challenge faced by pseudocapacitive electrode materials is insufficient charge storage capability with high intrinsic electrical resistance and structural instability. With an exponential increase in the demand for a pollutant-free environment, ternary metal compounds are being extensively explored as an attractive solution to these problems. Herein, we have addressed a solution to the above-listed issues by synthesizing novel and binder-free NiMnCo layered double hydroxide (NiMnCo-LDH) nanosheets on Fe-substituted NiCo2O4 (FexNi1-xCo2O4) nanorods supported on nickel foam via a facile hydrothermal method followed by chemical bath deposition. The highly defined and well-distributed porous Fe-substituted NiCo2O4 nanorod structure integrated with the ternary NiMnCo-LDH nanosheets provide ultra-fast kinetics of charge transfer, increased charge storage capacity, and high structural stability. The nanocomposite electrode delivers a high specific capacity of 281 mAh/g at a scan rate of 5 mV/s (265 mAh/g at 1 A/g) with a capacitance retention of 92% after 5000 cycles at 2 A/g. The effect of Fe in NiCo2O4 is further validated by performing density-functional theory (DFT) calculations to obtain atomic insights on electrical conductivity using the density of states (DOS) and band structures. Finally, a symmetric supercapacitor based on FexNi1-xCo2O4@NiMnCo LDH was assembled which delivered an impressive energy density of 105 Wh/kg and a power density of 1112 W/kg, proving FexNi1-xCo2O4@NiMnCo-LDH as an electrode material to be used for applications of energy storage.