Design and Synthesis of Zinc-Activated CoxNi2−xP/Graphene Anode for High-Performance Zinc Ion Storage Device

Graphical The power of doubles : A zinc ion capacitor assembled using a zinc ion-activated double transition metal phosphide/graphene battery anode material shows excellent energy density and cycling stability. The anode well compensates for the lack of electrochemical kinetics of the anode during the energy storage process and also effectively inhibits the formation of zinc dendrites and other by-products. This provides more feasibility for the long-term stable output of zinc ion capacitors. 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 Co x Ni 2− 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 ZnSO 4 . 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 Co 2 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.