Sea urchin-like architectures and nanowire arrays of cobalt-manganese sulfides for superior electrochemical energy storage performance

Cobalt-manganese (Co-Mn)-based bimetallic compounds (such as Co-Mn oxides, hydroxides) have been investigated as a new type of high-performance electroactive materials for energy storage device. Nevertheless, Co-Mn sulfides are seldom investigated, especially for those with hierarchical architectures and structures. Herein, we first adopt a facile two-step hydrothermal route and synthesize Co-Mn sulfides with sea urchin-like architecture and nanowire array structure. The anion-exchange sulfuration process gives rise to hierarchical structure with numerous nanosheets grown on the surface. Benefiting from the attractive structures and the high electrochemical activity of Co-Mn sulfides, the Co-Mn sulfides show improved performance than Co-Mn oxides with similar morphology. Especially, the Ni foam-supported Co-Mn sulfide nanowire arrays exhibit superior performance of 502 C g(-1) at 1 A g(-1) as well as excellent cycling stability with 107% of capacity retention after 2000 cycles. In addition, a hybrid supercapacitor Co-Mn sulfide nanowire arrays/RGO displays an energy density of 18.4 Wh kg(-1) at 375 W kg(-1). More importantly, an ultrahigh power density (22.5 kW kg(-1) at 9.5 Wh kg(-1)) and outstanding cycling stability can also be achieved. The excellent electrochemical performance can be ascribed to the attractive structure and high electrochemical activity of Co-Mn sulfide.