Complexing of Ni_xMn_y sulfides microspheres via a facile solvothermal approach as advanced electrode materials with excellent charge storage performances

Mixed metal sulfides with high specific capacitances and superior rate capabilities can meet the need of new materials for technological advancement of energy storage systems. We demonstrate in this study a facile fabrication of microspheres-like Ni_xMn_y sulfides with different molar ratios of metallic salts through a one-step solvothermal route. The hierarchical Ni_xMn_y sulfides-based compounds feature spherical architectures with relatively rough surfaces and assembled from ultrasmall and self-aggregated nanoprimary crystals. Especially, the Ni_xMn_y sulfide (x/y = 1:1) presents an excellent battery-like performance with a high specific capacitance (219.4 mAh g⁻¹ at current density of 1 A g⁻¹) and a good rate capability (123 mAh g⁻¹ at 50 A g⁻¹), benefiting from the greatly improved faradaic redox processes boosted by the synergistic effect of Ni and Mn electroactive components and as well as fast mass transfer. Furthermore, the as-fabricated asymmetric supercapacitor based on Ni_xMn_y sulfide (x/y = 1:1) presents a maximum energy density of 34 W h kg⁻¹ at a power density of 868.1 W kg⁻¹ with both superior rate and long-term cycling stabilities. In view of low cost and improved electrochemical performance, such integrated compound proposes a new and feasible pathway as a potential electrode configuration for energy storage devices.