Metal‐Organic Framework Derived Ni2P/C Hollow Microspheres as Battery‐Type Electrodes for Battery‐Supercapacitor Hybrids

Abstract Nickel phosphide (Ni2P/C) hollow microspheres were synthesized via a facile two‐step route based on metal‐organic framework (MOF) precursors. Unlike direct phosphating the MOF by calcination that would damage the MOF structure and that would form multiple phases, solvothermal method was able to convert the Ni‐based MOF to one‐pure‐phase nickel phosphide with the MOF skeleton maintained, as suggested by XRD, XPS, and SEM. When using as the battery‐supercapacitor hybrids electrode material, the optimized Ni2P/C exhibited the specific capacity 670.4 C/g (1676 F/g) at 1 A/g in a three‐electrode system, and a maximum energy density 42.74 Wh/kg at 764.23 W/kg in an asymmetric supercapacitor. It also delivered an energy density of 35.39 Wh/kg at 7000 W/kg with the rate capability retention of 92 % after 5000 cycles. The high specific surface area and the increased amount of electrochemically active sites endowed by the unique morphology, together with the low charge transfer resistance all contribute to the excellent electrochemical performance of the Ni2P/C material. These also indicate that solvothermal method is feasible in converting MOF to metal phosphide for the application in energy storage and conversion systems.