Triple-shelled nickel-cobalt-manganese sulfides hollow spheres for advanced hybrid supercapacitors

To design high-performance hybrid supercapacitors, positive and negative electrode materials with superior electrochemical features are needed. This paper proposes the fabrication of a hybrid supercapacitor using hollow ternary mixed metal sulfides as a positive electrode and iron oxide-decorated nitrogen-doped reduced graphene oxide (Fe3O4/N-rGO) as the negative electrode. Triple-shelled hollow spheres of nickel-cobalt-manganese-sulfides (NCMS) are synthesized using an optimum calcination temperature, followed by post-sulfurization. As the positive electrode, NCMS produced at 350 °C (NCMS-350) displays a high specific capacity of 797 C g−1 (1885 F g−1) at 1 A g−1 with excellent rate capability (79.5% at 20 A g−1). On the other hand, the negative Fe3O4/N-rGO electrode is synthesized hydrothermally without post-calcination and exhibits a maximum specific capacity of 454 C g−1 (378 F g−1) at 1 A g−1. Moreover, the NCMS-350//Fe3O4/N-rGO hybrid device delivers an impressive energy density of 67.9 Wh kg−1 at 474 W kg−1. These promising electrochemical performances provide a facile strategy for optimizing and integrating electrode materials to develop high-performance hybrid supercapacitors for efficient energy storage.