The performance and operation of an energy storage device are significantly influenced by the electrolyte and electrode materials. Therefore, it is crucial to develop an electrode material with a rational design and achieve compatibility with the electrolyte. In this study, we prepare Ni-MOF derived nickel phosphides/carbon (NP@C) nanostructure as an electrode for supercapacitor application. The as synthesized material provides more redox-active sites, better spatial utilization, improved conductivity, and a high-polarized surface that will speed up ion migration at electrode/electrolyte. Also, the usage of redox additive electrolyte (0.2 M K3[Fe (CN)6] in 1 M Na2SO4) further complements the redox active sites and hence the improved charge transport. Therefore, NP@C electrode achieved a remarkable 2136.3 F/g of capacitance at 3 A/g with 90.6 % of capacitance retention after 5000 charge-discharge cycles. In addition, the surface-diffusion studies confirms that NP@C shows high diffusion contribution of 82.6 % in redox electrolyte than that of 25.1 % in 1 M Na2SO4. Furthermore, NP@C//NP@C symmetric supercapacitor device in redox additive electrolyte also delivered remarkable performance rendering high energy density of 52.5 Wh/kg at a power density of 750 W/kg. In addition, NP@C//NP@C also shows the long-term stability with attenuating only 7.2 % of initial capacitance value after 10000 charge-discharge cycles. In addition to this, the device performs extremely well when tested for self-discharge studies. Hence, this study demonstrates the perfect harmony of NP@C electrodes and redox additive electrolyte to fabricate a high-performance supercapacitor.