Reagent-assisted hydrothermal synthesis of NiCo2O4 nanomaterials as electrodes for high-performance asymmetric supercapacitors

Abstract

In this study, mesoporous nickel cobaltate (NiCo₂O₄) nanomaterials were loaded onto nickel foam through a simple and environment-friendly reagent assisted hydrothermal method. The impacts of reagents on the micro-morphology and electrochemical capacitive properties were studied. The NiCo₂O₄ nanoneedle arrays prepared with cetyltrimethylammonium bromide (CTAB) as the auxiliary reagent exhibited a relatively higher specific surface area, convenient charge transport channel, excellent specific capacitance (1153.2 F g⁻¹ at a current density of 1 A g⁻¹), remarkable rate performance (10 A g⁻¹, 812 F g⁻¹) and good cycling stability (75% of the initial value is retained at 10 A g⁻¹ after 1000 cycles). The asymmetric supercapacitor assembled by the optimized NiCo₂O₄ nanomaterial as the positive electrode and activated carbon as the negative electrode provides an energy density of 22.5 W h kg⁻¹ at 800 W kg⁻¹, and displays an excellent cycle performance of 97.1% after 1000 cycles at 1 A g⁻¹. It is suggested that the CTAB-assisted nanoneedle array-structured NiCo₂O₄ electrode material could be a potential candidate for supercapacitors.