Design and Synthesis of Zinc-Activated Cox Ni2-x P/Graphene Anode for High-Performance Zinc Ion Storage Device.

Zinc ion capacitors (ZICs) composed of capacitor-type cathodes and battery-type anodes have attracted widespread attention thanks to the huge potential in the next generation of low-cost energy-storage devices. It is a challenge to explore a universal anode for aqueous ZICs with high-efficiency energy-storage characteristics. In this work, the double-transition-metal composite Cox Ni2-x P/reduced graphene oxide (rGO) with sufficient electrochemical activity and charge-transfer kinetics was successfully synthesized. The Zn@CoNiP/rGO anode obtained by zinc-ion activation and a biomass-derived porous carbon cathode (PC) were assembled into an aqueous ZIC (CNP-ZIC) in 2 m ZnSO4 . Finally, the CNP-ZIC reveals excellent energy and power densities with a working potential range of 0.2-1.9 V. CNP-ZICs shows high capacitance of up to 356.6 F g-1 at 0.5 A g-1 (based on the mass of active material on the PC cathode), which is far superior to the performance of conventional asymmetric energy storage devices (CoNiP/rGO//PC and Co2 P/rGO//PC). The CNP-ZIC exhibits both a very high energy density of 143.14 Wh kg-1 and good cycling life (∼92.2 % retention after 10000 charge-discharge cycles at 7.5 A g-1 ). There is no doubt that this work provides a promising strategy for assembling novel zinc ion hybrid supercapacitors with high efficiency and stable output.