Hierarchical layer-by-layer porous FeCo₂S₄@Ni(OH)₂ arrays for all-solid-state asymmetric supercapacitors

Engineering multicomponent active materials as electrodes with a rationally structured design is an effective strategy to meet the high-performance requirements of supercapacitors. In this report we describe the fabrication of a hierarchical layer-by-layer porous FeCo₂S₄@Ni(OH)₂ three-dimensional (3D) network on nickel foam, which shows both an excellent specific capacitance of 2984 F g^-1 at 5 mA cm^-2 and cycling stability over 5000 cycles. The outstanding performance is ascribed to the distinctive self-supported structure and the synergistic effect between FeCo₂S₄ and Ni(OH)₂. Moreover, the all-solid-state FeCo₂S₄@Ni(OH)₂//reduced graphene oxide asymmetric supercapacitor exhibits a high energy density of 64 W h kg^-1 at a power density of 800 W kg^-1 and excellent cycling stability (92.9% of capacity retention after 10000 cycles), while the output voltage can reach 1.6 V. This rational design of the layer-by-layer structured electrode provides an innovative strategy for fabricating electrodes for future energy storage devices.