Binderless synthesis of hierarchical, marigold flower-like NiCo2O4 films for high-performance symmetric supercapacitor

Abstract

The facile and cost-effective chemical bath deposition method is employed for the binder-free synthesis of NiCo2O4 marigold flower-like nanostructures on a flexible stainless-steel substrate. Binderless and surfactant-free synthesis of NiCo2O4 films for supercapacitor application is a crucial part of this synthesis process. The effect of reaction times on the deposition of NiCo2O4 nanostructured films has been discussed briefly based on the electrochemical performance and surface morphology of films. The reaction time is varied as 2, 4, 6, and 8 h. The prepared films were analyzed by structural and morphological characterizations. The time-dependent significant change in morphology of NiCo2O4 films is discussed in detail. The development of the Marigold-like flowers from wheat grain-like nanostructures has been observed for increasing reaction time. The film deposited at 6 h reaction time (NCO-6 electrode) showed better specific capacitance of 1277 F/g at 5 mA/cm2, which retained about 95 % after 10,000 cycles. The NiCo2O4 film exhibited a 0.7 V potential window with the maximum energy and power density of 86 Wh/kg and 2333 W/kg, respectively. The fabricated aqueous symmetric device i.e., NCO//NCO showed energy density and power density of 16.4 Wh/kg and 275.5 W/kg, respectively. The fabricated device shows 90.5 % retention in performance after 5000 cycles. These results revealed that NiCo2O4 can be a better electrode material for energy storage devices.