Honeycomb-like mesoporous cobalt nickel phosphate nanospheres as novel materials for high performance supercapacitor

Cobalt nickel phosphate nanospheres with honeycomb-like mesopores (CoxNi(3-x)(PO4)2) are firstly synthesized via a facile hydrothermal process combining with low temperature pyrolysis. The dehydration process of the hydrated cobalt nickel phosphate plays an important role in the formation of the honeycomb-like mesopores, which are illustrated in detail. The uniform honeycomb-like mesoporous structure offers more active sites for electrochemical reaction and short transport path for the electrolyte ions. For these reasons, as well as the synergistic effect between the cobalt species and the nickel species, the as-prepared porous cobalt nickel phosphate electrodes, which are primary used in supercapacitor, exhibit both high specific capacitance (1409 F g−1 at 0.25 A g−1 for Co0.86Ni2.14(PO4)2 electrode) and high rate-performance. An asymmetric supercapacitor, assembled with the as-prepared cobalt nickel phosphate as positive material and a home-made activated carbon as negative material, exhibits a high energy density of 45.8 Wh kg−1 at the power density of 42.4 W kg−1, and even 30.7 Wh kg−1 at the power density of 2.8 kW kg−1.