FeCoP nanosheets@Ni-Co carbonate hydroxide nanoneedles as free-standing electrode material for hybrid supercapacitors

Abstract Developing advanced battery-type electrode materials with versatile morphologies and micro-/nanostructures is crucial to realize high-performance hybrid supercapacitors with high energy density and excellent cycle life. Herein, a facile approach is proposed to design free-standing FeCoP nanosheets decorated by Ni substituted Co carbonate hydroxide (Ni-CoCH) nanoneedles on carbon cloth as a novel cathode for hybrid supercapacitor. This smart hetero-network assembled by conductive FeCoP nanosheets as a core and redox active Ni-CoCH nanoneedles as a shell exhibits increased surface area, improved availability of redox active sites, and facilitated ion/electron transport for faradaic reactions when compared to a single component. Benefiting from its unique core/shell nanostructure, multifunctionality and synergistic effect of two components, the as-prepared FeCoP@Ni-CoCH electrode acquires a high specific capacity of 795.5 C g−1 at a current density of 1 A g−1 and outstanding rate capability and good long-term cyclic stability (89.7% of the initial capacitance after 5000 cycles). Furthermore, a hybrid supercapacitor device consisting of FeCoP@Ni-CoCH as cathode and hierarchical porous carbon as anode in 2 M KOH electrolyte delivers a high energy density of 72.7 Wh kg−1 at a power density of 404.9 W kg−1 and superior cyclic stability.