Construction of 2D–2D Plate-on-Sheet Cobalt Sulfide–Reduced Graphene Oxide Nanocomposites for Enhanced Energy Storage Properties in Supercapacitors

Cobalt sulfides, as a class of promising electrode materials for supercapacitors, are still limited by an unsatisfactory rate capability and cyclic instability, which are caused by their easy agglomeration and large volume changes during repeated charge–discharge processes. Herein, two-dimensional (2D)–2D plate-on-sheet CoS2-reduced graphene oxide (rGO) nanocomposites were constructed by a facile solvothermal reaction followed by heat treatment. In such heterostructured nanocomposites, interconnected rGO nanosheets as supports are revealed to disperse CoS2 nanoplates well on the surface, providing many electroactive sites. More importantly, the face-to-face contact via the C–O–Co bonds creates a highly coupled interface, which not only efficiently promotes interface charge transfer but also increases the mechanical strength to accommodate volume variation. As a result, the synthesized CoS2-rGO nanocomposites exhibit specific capacitances of up to 1417 (1119) F g–1 at 2 (20) A g–1, together with 92% capacitance retention after 5000 cycles at 10 A g–1. Furthermore, the charge storage behavior of CoS2-rGO nanocomposites is investigated by ex situ characterization techniques. Our findings not only further the understanding of the energy storage mechanism of 2D–2D heterostructured CoS2-rGO nanocomposites but may also be extended to the rational design of other high-performance metal sulfide-based nanocomposite electrodes.