Structure-engineering of core-shell ZnCo2O4@NiO composites for high-performance asymmetric supercapacitors

The implementation of a structure-designed strategy to construct hierarchical architectures of multicomponent metal oxide-based electrode materials for energy storage devices is in the limelight. Herein, we report NiO nanoflakes impregnated on ZnCo2O4 nanorod arrays as ZnCo2O4@NiO core-shell structures on a flexible stainless-steel mesh substrate, fabricated by a simple, cost-effective and environmentally friendly reflux condensation method. The core-shell structure of ZnCo2O4@NiO is used as an electrode material in a supercapacitor as it provides a high specific surface area (134.79 m(2) g(-1)) offering high electroactive sites for a redox reaction, reduces the electron and ion diffusion path, and promotes an efficient contact between the electroactive material and electrolyte. The binder-free ZnCo2O4@NiO electrode delivers a high specific capacitance of 882 F g(-1) at 4 mA cm(-2) current density and exhibits remarkable cycling stability (similar to 85% initial capacitance retention after 5000 charge-discharge cycles at 10 mA cm(-2)). The asymmetric supercapacitor device ZnCo2O4@NiO//rGO delivered a maximum energy density of 46.66 W h kg(-1) at a power density of 800 W kg(-1). The device exhibited 90.20% capacitance retention after 4000 cycles. These results indicate that the ZnCo2O4@NiO architecture electrode is a promising functional material for energy storage devices.

Automated summary

The core-shell structured electrode material ZnCo2O4@NiO, fabricated through a cost-effective method, shows high specific capacitance and cycling stability in a supercapacitor, indicating its promising application in energy storage devices.