Designing pinecone-like and hierarchical manganese cobalt sulfides for advanced supercapacitor electrodes

Abstract

Transition metal sulfides with nanoporous structures draw widespread interest in various applications, such as energy storage and solar cells, owing to their unique features and intriguing properties. However, research on manganese cobalt sulfide composites is very limited even though they are promising candidates for supercapacitor electrodes. Herein we design a manganese cobalt sulfide with a pinecone-like and hierarchical porous nanosphere structure, namely pinecone-like and hierarchical manganese cobalt sulfide (PHMCS). The MnS and CoS nanospheres are synthesized individually, and they possess specific capacitances of 119 F g⁻¹ and 632 F g⁻¹ at a current density of 1 A g⁻¹, respectively. The physical mixture of MnS and CoS (MIX) only shows 193 F g⁻¹ at 1 A g⁻¹ which may be attributed to the unconsolidated connection between two independent sulfides. In order to improve the electrochemical performance of manganese and cobalt sulfides, PHMCS is produced with a specific capacitance of 992 F g⁻¹ and 102.35% retention after 5500 cycles at 10 A g⁻¹. The synergistic effect between the hierarchical CoS and pinecone-like MnS nanospheres contributes to the improved specific capacitance. The unique porous structures of PHMCS create sufficient space for electrode materials to expand and shrink when reacting with ions from the electrolyte, which turns PHMCS into an extremely durable material for supercapacitor electrodes.