Crystalline flower-like nickel cobaltite nanosheets coated with amorphous titanium nitride layer as binder-free electrodes for supercapacitor application

Abstract

Fabrication of high-performance supercapacitors involves a three-step strategy - selection of suitable electrode material, optimized morphology, and efficient synthesis approach. For the first time, an integrated synthesis approach using the facile hydrothermal technique (for growing NiCo2O4 nanosheets) followed by vacuum cathodic arc deposition (for depositing thin TiN layers) is used to improve the electrochemical stability of pristine nickel cobaltite (NiCo2O4). The hierarchical flower-like NiCo2O4@TiN nanosheets grown on nickel foam as binder-free electrode shows a high specific capacity of 402.57 Cg−1 at 1 Ag−1, excellent rate capability of 82.8% when current density increases from 1 Ag−1 to 20 Ag−1, and cycling stability of 90% over 2000 charge-discharge cycles. The remarkable electrochemical performance of NiCo2O4@TiN-220/Ni signifies its ample potential for the fabrication of a supercapacitor device. A coin-cell symmetric supercapacitor (CR2032) is assembled using the NiCo2O4@TiN-220/Ni electrodes, which exhibits remarkable electrochemical performance, including a specific capacitance of 178 Fg−1, an energy density of 46.4 Wh kg−1 at a power density of 1363 W kg−1, and a capacitance retention of 129.4% after running 3500 cycles. The enhanced performance can be attributed to the porous morphology with core/shell flower-like nanosheet structure of NiCo2O4@TiN grown on nickel foam. The study also emphasizes a good tuning of crystalline metal oxide (NiCo2O4) with amorphous metal nitride (TiN) as high performing electrode for supercapacitor application.