Advanced Supercapacitor Electrodes: Trimetallic Co–Mn–Fe Selenide Nanoflowers Encased in Reduced Graphene Oxide

Metal selenides (MSes) are increasingly recognized for their robust redox activities and notable conductivity, positioning them as promising materials for advanced energy-storage applications. Nonetheless, their practical utilization is often hampered by challenges, such as poor cycle life and limited rate capabilities. In this study, we address these issues by integrating MSes with reduced graphene oxide (RGO) to construct a nanostructured electrode with enhanced performance characteristics. Specifically, we developed a binder-free electrode comprising trimetallic Co–Mn–Fe selenide nanoflowers encapsulated within an RGO matrix on nickel foam (CMFS-RGO/NF), which is tailored for use in hybrid supercapacitors. This innovative electrode architecture offers several advantages: the CMFS nanoflowers facilitate swift ion diffusion and provide abundant electroactive sites, while the RGO wrapping enhances the electrical conductivity, prevents the aggregation of nanoflowers, and maintains the structural integrity during extended cycling. The resultant CMFS-RGO/NF electrode demonstrates superior electrochemical efficiency, achieving a capacity of 1112.5 C/g at 1 A/g, an excellent rate performance with 79.4% capacity retention at 25 A/g, and a fantastic lastingness of 94.6%. Further, when configured into a hybrid apparatus with activated carbon (AC) (CMFS-RGO/NF//AC), the apparatus exhibits exceptional electrochemical behavior, showcasing an energy density (E_den) of 65 Wh kg^–1 at a power density (P_den) of 802.5 W kg^–1 and a remarkable lastingness of 91%. These results underscore the potential of our fabrication strategy, leveraging RGO-encapsulated MSes to boost the efficiency of supercapacitors, thereby providing a scalable and effective approach for developing next-generation energy-storage systems.