Controllable synthesis of hierarchical NiCo2S4@Ni3S2 core–shell nanotube arrays with excellent electrochemical performance for aqueous asymmetric supercapacitors†
Abstract
In this study, unique NiCo2S4@Ni3S2 core–shell nanotube arrays (NTAs), a promising positive electrodes for supercapacitors, have been successfully synthesized on Ni foam via a novel method. Electrochemical tests show the highest area specific capacity of 4.25 C cm−2 at 4 mA cm−2, maintained at 3.12 C cm−2 at 40 mA cm−2. In addition, a 3D reduced graphene oxide (rGO) aerogel has been fabricated as a negative electrode for supercapacitors, and this displays an excellent capacitance performance of 286.9 C g−1 at 1 A g−1. An asymmetric supercapacitor denoted as NiCo2S4@Ni3S2//rGO has been assembled based on NiCo2S4@Ni3S2 core–shell NTAs and rGO aerogel. The NiCo2S4@Ni3S2//rGO device achieves an outstanding performance with a specific capacity of 163.15 C g−1, an energy density of 32.75 W h kg−1 at a power density of 0.36 kW kg−1. Moreover, it displays a remarkable cycling performance (77.5% capacity retention after 5000 cycles). These results indicate potential applications of NiCo2S4@Ni3S2//rGO in asymmetric supercapacitors (ASCs).