Composition engineering strategy of carbon–coated bimetallic phosphide for high energy density hybrid supercapacitors

Abstract

Bimetallic phosphides hold great promise for using in hybrid supercapacitors (HSCs) as electrode material due to their synergistic effect of hetero-metal ions in ameliorating specific capacity and electrical conductivity. The production of bimetallic Ni1-xCoxP nanocrystals based on carbon-coated (Ni1-xCoxP@C) is described, and their potential application as positive electrodes in HSCs is also discussed. We give an insight into the significance of composition engineering for nickel-cobalt bimetallic phosphides in obtaining excellent electrochemical performance for supercapacitors. Ni0.9Co0.1P@C electrode reaches a maxima specific capacity as high as 4250 ± 48 mC cm−2 at 1 mA cm−2 (1327 ± 15 C g−1 at 1 A g−1), outperforming most transition metal phosphides (TMP)-based electrodes reported recently. Utilizing Ni0.9Co0.1P@C as electrode, the obtained HSC device provides a desired energy density of 46.9 ± 2.2 Wh kg−1 at 1600 W kg−1 and continues to sustain 26.2 ± 1.3 Wh kg−1 at a significant power density of 8000 W kg−1, capacitance retention remaining at 89.4 % after 10,000 cycles. It is believed that the Ni0.9Co0.1P@C has significant promise for application in extremely effective and affordable HSCs, as well as probably in other energy storage devices.