Unravelling the electrochemistry of Ni-MOF derived nickel phosphide/carbon composite electrode and redox additive electrolyte for high performance supercapacitors
Prashant Dubey, Mansi, Marcin Hołdyński, Akash Deep, Umesh Tiwari, Wojciech Nogala, Vishal Shrivastav, Shashank Sundriyal
Abstract
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.