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.