Design of FeCo2S4@Ni(OH)2 core-shell hollow nanotube arrays on carbon paper for ultra-high capacitance in supercapacitors

Abstract

In this paper, we design a novel FeCo2S4@Ni(OH)2 core-shell hollow nanotube arrays on carbon paper for superior capacitance of supercapacitors. FeCo2S4 hollow nanotube arrays vertically grow on carbon paper via hydrothermal reaction served as a “core” to shorten the ion transport path, Ni(OH)2 nanosheets modified on the hollow nanotube arrays based on constant voltage electrodeposition reveal outstanding pseudocapacitance characteristic. The ultrathin Ni(OH)2 nanosheets act as a “shell” layered to expand the specific surface area, effectively increasing the active sites of the faraday reaction. The subtle heterogeneous synergistic effects significantly improve their electrochemical performance. The unique core-shell structure of FeCo2S4@Ni(OH)2 displays a superior capacity of 239.72 mA h g−1 at 1 A g−1, even at 8 A g−1 still has a capacity of 128.0 mA h g−1, indicating the excellent rate performance. Significantly, the asymmetric supercapacitor assembled by the FeCo2S4@Ni(OH)2 nanoarrays positive electrode and activated carbon (AC) negative electrode exhibits superior electrochemical performance with ultra-high energy density (55.33 Wh Kg−1 at 800 W kg−1) and power density (8000 W kg−1 at 15.78 Wh Kg−1). After 10000 charge-discharge cycles, the device still has capacitance retention of 93.8%. Therefore, FeCo2S4@Ni(OH)2 nanoarrays can be widely used in high-performance supercapacitors as potential and promising electrode materials.