Three-dimensional coral-like NiCoP@C@Ni(OH)2 core-shell nanoarrays as battery-type electrodes to enhance cycle stability and energy density for hybrid supercapacitors

Abstract

Transitional metal phosphides (TMPs) are regarded as comparatively promising electrode materials for energy storage and conversion. However, the poor cycling performance of TMPs remains to be a major challenge of their practical application for supercapacitor. In this work, coral-like NiCoP@C@Ni(OH)2 core-shell nanoarrays are vertically grown on nickel foams using two-step hydrothermal reaction, followed by carbonization and phosphorization treatment. The participation of amorphous carbon layer and ultrathin Ni(OH)2 nanosheets is expected to improve the performance of cycling stability and energy density. This NiCoP@C@Ni(OH)2 NAs exhibit high specific capacitance of 2300.8 F g−1 at a density of 1 A g−1, good rate capability (72.1% of capacitance at 20 A g−1) and long-term cycling stability (81.2% retention after 3000 cycles at 10 A g−1). Moreover, with the help of ultrathin Ni(OH)2 nanosheets, a hybrid supercapacitor assembled by the NiCoP@C@Ni(OH)2 NAs electrode against activated carbon achieves a high energy density (49.5 Wh kg−1 at a power density of 399.8 W kg−1). These results demonstrate that such NiCoP@C@Ni(OH)2 NAs hold great promise as novel battery-like electrode for hybrid supercapacitors in energy conversion.