Facile fabrication of core-shell structured Ni(OH)₂/Ni(PO₃)₂ composite via one-step electrodeposition for high...

Metal metaphosphates, particularly those with core-shell structure, have showed extraordinary potential in energy storage field due to their superior chemical and physical properties. However, the core-shell metal metaphosphates with high energy density in supercapacitor application is rarely reported. Here, the core-shell structured Ni(OH)₂/Ni(PO₃)₂ (NNP) hybrid electrode were prepared by one-step electrodeposition, which exhibits a superior specific capacitance of 1477 F g^-1 at a current density of 1 A g^-1. Furthermore, an aqueous asymmetric supercapacitor (ASC) based on NNP hybrid composite as cathode and reduced graphene oxide (rGO) as anode is assembled successfully to deliver a prominent energy density of 67 Wh kg^-1 at 775 W kg^-1 and splendid stability with capacitance retention of 81% after 8000 cycles. The outstanding electrochemical capabilities are attributed to the porous nanoflake and hierarchical core-shell structure of NNP hybrid composite, which can accelerate ion diffusion and charge transfer in redox reaction. These results indicate that nanohybrid NNP material has promise to be an advanced energy storage material.