Redox Additive Electrolyte Study of Metal-Organic Framework Derived Nickel Phosphide/Carbon Composite for Supercapacitors

Abstract

The performance and operation of an energy storage device are significantly influenced by the electrolyte and electrode materials. Therefore, it is crucial to create an electrode material with a rational design and ensure that it is compatible with the electrolyte. In this study, we prepare nickel phosphides/carbon (NP@C) nanostructure from Nickel metal-organic framework (Ni-MOF) using one-step phosphidation technique for supercapacitor applications. This method aims to produce a distinctive structure with more redox-active sites as well as improved conductivity and a high-polarized surface that will speed up ion migration between the electrolyte and the surface. In order to further enhance the redox additive sites and thus the charge transport, we have employed redox additive electrolyte (0.2M K3[Fe(CN)6] in 1M Na2SO4). Using three electrode electrochemical system, NP@C electrode obtained a phenomenal specific capacitance of 2136.3 F/g at 3A/g with a specific capacitance retention rate of 90.6% after 5000 cycles. Furthermore, a symmetric supercapacitor device is assembled using two NP@C electrodes and redox additive electrolyte that renders a high energy density of 52.5 Wh/kg at a power density of 750 W/kg along with a long cycle life of ~93% after 10000 cycles. Hence, this study demonstrates how NP@C and redox additive electrolyte work in perfect harmony to generate a high-performance supercapacitor.