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 _0.5Ni _0.5PO 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-xNi _xPO ₄ electrodes. The KCo _0.5Ni _0.5PO 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 _0.5Co _0.5PO 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 _0.5Ni _0.5PO ₄ a potential positive electrode for the development of high-performing HSCs.