Phase Evolution and Electrochemical Performance of MnS Materials for High-Performance Supercapacitors

α- and γ-MnS materials were successfully prepared by a simple hydrothermal method. A thorough investigation was conducted into the phase evolution, morphology, and electrochemical performances. It is found that excessive water shifts the growth of MnS powders to thermodynamic regimes, and the Ostwald ripening process favors the formation of thermodynamically stable α-MnS, while pure γ-MnS can only be prepared with a mixture of ethylene glycol (EG) and water. Both α- and γ-MnS electrodes deliver remarkable electrochemical performances, demonstrating specific capacities of 320 and 477 F/g at 1 A/g and capacity retention rates of 90 and 72% after 3000 cycles at 5 A/g, respectively, outperforming the electrochemical performances of α- and γ-MnS electrodes reported in former literature. The superior specific capacity of γ-MnS to that of α-MnS can be ascribed to its stacked layered structure, which is more conducive to the accommodation of ions.