Effect of Ni incorporation in KCoPO4 on the charge storage capacity of KCo1-xNixPO4 (0≤x≤0.5) Electrodes for the Fabrication of High-Performing Hybrid Supercapacitors

To fulfill the increasing energy demands of the world through renewable energy sources requires the utilization of a highly efficient large-scale electrochemical energy storage device. A hybrid Supercapacitor (HSC) that consists of a battery-type electrode coupled with the counter capacitive electrode, while in principle offering supercapacitor-like power and cyclability values and higher energy density can be a potential device as a large-scale energy storage device to cater to the energy needs through renewable energy sources. The KCo 0.5 Ni 0.5 PO 4 electrode demonstrated a notably enhanced electrochemical performance attributed to the synergistic interaction of Co 2+ and Ni 2+ ions in a phosphate framework. The incorporation of redox-mediated diffusive charge storage through the incorporation of Ni 2+ on the Co 2+ site resulted in a large-scale charge storage capacity coupled with capacitive-type surface charge storage on the KCo 1-x Ni x PO 4 electrodes. The KCo 0.5 Ni 0.5 PO 4 delivers 173 mAh/g (capacitances: 1038 F/g) at a current density of 0.5A/g in an aqueous 2M KOH electrolyte accompanied by cyclic stability up to 5000 cycles. HSC mode consists of Activated Carbon as the negative electrode along with KNi 0.5 Co 0.5 PO 4 as the positive electrode displaying high energy density and power density of 183.7 Wh/kg and 7952W/kg respectively, in 2M aqueous KOH electrolyte. The superior full performance in HSC mode makes KCo 0.5 Ni 0.5 PO 4 a potential positive electrode for the development of high-performing HSCs.