A Ni-P@NiCo LDH core–shell nanorod-decorated nickel foam with enhanced areal specific capacitance for high-performance supercapacitors

Recently, transition metal-based nanomaterials have played a key role in the applications of supercapacitors. In this study, nickel phosphide (Ni-P) was simply combined with NiCo LDH via facile phosphorization of Ni foam and subsequent electrodeposition to form core-shell nanorod arrays on the Ni foam; the Ni-P@NiCo LDH was then directly used for a pseudocapacitive electrode. Owing to the splendid synergistic effect between Ni-P and NiCo LDH nanosheets as well as the hierarchical structure of 1D nanorods, 2D nanosheets, and 3D Ni foam, the hybrid electrode exhibited significantly enhanced electrochemical performances. The Ni-P@NiCo LDH electrode showed a high specific capacitance of 12.9 F cm-2 at 5 mA cm-2 (3470.5 F g-1 at a current density of 1.3 A g-1) that remained as high as 6.4 F cm-2 at a high current density of 100 mA cm-2 (1700 F g-1 at 27 A g-1) and excellent cycling stability (96% capacity retention after 10 000 cycles at 40 mA cm-2). Furthermore, the asymmetric supercapacitors (ASCs) were assembled using Ni-P@NiCo LDH as a positive electrode and activated carbon (AC) as a negative electrode. The obtained ASCs delivered remarkable energy density and power density as well as good cycling performance. The enhanced electrochemical activities open a new avenue for the development of supercapacitors.