Potentiodynamic polarization assisted phosphorus-containing amorphous trimetal hydroxide nanofibers for highly efficient hybrid supercapacitors

Abstract

Due to their high capacity, nickel–cobalt-based cathode materials have attracted significant attention as potential components of hybrid solid-state supercapacitors (HSSCs). However, their poor cycling stability and low rate capability have impeded their implementation. In the present study, a single-step, binder-free potentiodynamic polarization approach is presented for the preparation of battery-type phosphorus-containing amorphous trimetal nickel–ruthenium–cobalt hydroxide (P@NRC-OH) nanofibers on Ni foam for use in high-energy, stable HSSCs. The phosphate dopant and the trimetal-rich electrode surface increase the intrinsic electron conductivity and redox activity and generate a large number of active defects. As a consequence, a P@NRC-OH electrode exhibited enhanced energy storage properties in terms of specific capacity (541.66 mA h g⁻¹ at 3 mA cm⁻²), cycling durability (90.35% over 20 000 cycles), and rate capability (308.64 mA h g⁻¹ at 20 mA cm⁻²). An assembled full-cell HSSC with P@NRC-OH nanofibers as the cathode material and porous activated carbon as the anode material produced a maximum specific energy of 90.02 W h kg⁻¹ at a specific power of 1363 W kg⁻¹ which remained as high as 37.87 W h kg⁻¹ at a power density of 6818.18 W kg⁻¹, with remarkable cycling stability over 15 000 charge–discharge cycles. The proposed approach thus represents a scalable and efficient strategy for the design of electrodes and devices with superior electrochemical performance.