MOF-derived Co-Fe-P@NiCo-layered double hydroxides with high areal capacity for supercapacitor electrodes

Cobalt iron phosphide (Co-Fe-P), a metalloid-like material with zero band gap and high specific capacity, has received much attention in the field of supercapacitors, but the poor rate performance and cycling stability limit its commercial applications. Herein, we used cobalt-iron metal organic framework as the precursor (under the modulation of the polyvinylpyrrolidone (PVP), the morphology changes from three-dimensions to one-dimension), to synthesize the Co-Fe-P@NiCo-layered double hydroxide (LDH) core-shell nanostructure on conductive nickel foam (NF). Profiting of high conductivity of Co-Fe-P nanowires as the core and large surface area of NiCoLDH nanosheets as the shell, the fabricated Co-Fe-P@NiCoLDH/NF electrode exhibits outstanding electrochemical properties, such as high special capacity of 5.67 C cm(-2) at a current density of 1 mA cm(-2), remarkable rate capability (78.59% from 1 to 20 mA cm(-2)). Moreover, the asymmetric supercapacitor assembled by Co-Fe-P@NiCoLDH/NF and activated carbon/NF, also delivers excellent electrochemical performance with high energy density of 0.164 mW h cm(-2) (30.4 mW h cm(-3)) and a superior cyclic life span of 91.67% over 5000 cyclic tests under 20 mA cm(-2). This work proposes a unique route for the application of Co-Fe-P with elaborate structures, which may excite new significant findings in the energy storage field.