Templating synthesis of nickel cobaltite nanoflakes and their nanocomposites for making high-performance symmetric supercapacitors

Nickel cobaltite is one of the most popular pseudocapacitance materials for creating high-performance energy-storage devices because of its low cost, high electric conductivity, excellent electrochemical properties, and environmental friendliness. In this study, nickel cobaltite with nanoneedle morphology was synthesized by adopting the hydrothermal method. Change in the nickel cobaltite from nanoneedle to nanoflake morphology was induced by a template of the surface of a self-assembly graphene oxide (GO)/multiwall carbon nanotube (MWCNT) three-dimensional block matrix. Electrodes fabricated from the nanoflake nickel cobaltite, GO, and MWCNT composite exhibited high specific capacitance of 1525 F g⁻¹ at a current density of 1 A g⁻¹ and 1081 F g⁻¹ at a high current density of 100 A g⁻¹. When these composite electrodes were used as both the anode and cathode to assemble a symmetric supercapacitor with a 6 M KOH electrolyte, the supercapacitor exhibited a maximum energy density of 25.2 Wh kg⁻¹ and maximum power density of 5151 W kg⁻¹. Moreover, it maintained an excellent cycling stability of 99.6% of the initial capacitance value after 7000 charge–discharge cycles, demonstrating its remarkable potential for application in energy-storage and conversion devices.