ENHANCED SUPERCAPACITOR PERFORMANCE WITH NICKEL OXIDE AND ACTIVATED CARBON COMPOSITES IN WATER-IN-SALT ELECTROLYTE (WISE)
Abstract
Supercapacitors are high-power density energy storage systems, yet increasing their energy density remains a key challenge. Activated carbon (AC) is a widely used electrode material in supercapacitor due to its high surface area, but its capacitance is often limited. In this work, integrating AC with nickel oxide (NiO), which offers a high theoretical capacitance of up to 2584 F g-1 has been explored to enhance charge storage and further boost energy density. The electrochemical performance of supercapacitors using NiO/AC composites with weight ratio (g/g) of 1:3 (NC513), 1:1 (NC511) and 3:1 (NC531) was investigated and compared to a pure AC electrode (NC50). NiO was synthesized via precipitation, calcined at 400 °C, and characterized using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Electrochemical testing was conducted using a three-electrode system for linear sweep voltammetry (LSV) analysis. A symmetrical two-electrode system was fabricated for cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) analysis in a water-in-salt electrolyte of 15 M Ca(NO3)2. All electrodes achieved a 2.5 V potential window, with electric double-layer capacitor (EDLC) behavior. SEM analysis reveals a fragmented structure and increased roughness on NC513, enhancing electrolyte accessibility. This explains NC513’s optimized performance, with the highest specific capacitance of 35.32 F g-1 at 10 mV s-1 and an energy density of 9.96 Wh kg-1 at 0.5 A g-1, with the lowest iR drop (0.1 V), outperforming NC50. These findings highlight the potential of optimized NiO/AC (NC513) composites for enhancing supercapacitor performance by improving charge storage capability and conductivity. This study advances safer, high-performance supercapacitors, offering valuable insights into electrode material design for next-generation energy storage.
