Construction of Hierarchical NiCoP@NiFe-LDH Nanoflakes Heterostructure for High Energy Asymmetric Supercapacitor

Abstract

Layered double hydroxides (LDHs) are attractive electrode materials for supercapacitors due to their high theoretical capacitances and adjustable compositions, but also subjected to their intrinsic poor electrical conductivity and easy structure collapse properties. To resolve these intractable issues, LDHs are usually integrated with high conductivity and specific surface areas (SSAs) matrixes. Herein, NiCoP@NiFe-LDH nanoflakes array has been successfully grown on nickel foam by a facile phosphorization and subsequent hydrothermal process. The hierarchical porous structure, large SSA, as well as the strong interfacial reactions between NiFe-LDH and conductive NiCoP layer has enabled NiCoP@NiFe-LDH to deliver quantities of electroactive sites, fast ion diffusion and facile electron transfer, hence remarkably boosting the supercapacitive performance. Therefore, NiCoP@NiFe-LDH electrode has achieved a high specific capacitance of 2216 F g−1 at 1 A g−1 and retained 1038 F g−1 at 20 A g−1, whose specific capacitance and rate capability are much higher than those of NiCoP and NiFe-LDH electrodes. In addition, NiCoP@NiFe-LDH is assembled with an activated carbon electrode to fabricate an asymmetric supercapacitor, which displays a high energy density of 57.4 W h kg−1 and good cycling stability with 88.2 % capacitance retention after 5000 cycles. Therefore, the binder-free electrode composed of hierarchical NiCoP@NiFe-LDH nanoflakes array is promising for use in energy storage.