Nickel phosphide nanoparticles decorated on polypyrrole nanowires as battery-type electrodes for hybrid supercapacitors

Abstract

Metal phosphides as electrode materials for hybrid supercapacitors (HSCs) still face many challenges, such as insufficient electroactive sites, sluggish reaction kinetics, and low structural stability. To resolve these problems, we here integrate nickel phosphide (NiP) with polypyrrole (PPy) to construct PPy@NiP nanocomposites using a two-step electrochemical approach. Such nanocomposites are composed of amorphous NiP nanoparticles decorated on PPy nanowires. They are featured by increased amount of electroactive sites, enhanced electrical conductivity and electrolyte diffusion rate, and improved structural stability compared to the pure NiP particles. As a result, the PPy@NiP nanocomposites as HSC electrodes yield specific capacities of up to 364 mAh g−1 at 3 A g−1 and 159 mAh g−1 at 20 A g−1 as well as a 91% initial capacity retention over 5000 cycles at 10 A g−1. Their charge storage performance is superior to that of the pure NiP electrode. Furthermore, the fabricated PPy@NiP-based HSC device demonstrates an energy density of 57.3 Wh kg−1 at 798 W kg−1. This strategy for constructing PPy@NiP electrodes may be extended to other metal phosphide-based electrodes with enhanced charge storage performance for HSCs.