Hierarchical Metal Sulfide/Carbon Spheres: A Generalized Synthesis and High Sodium-Storage Performance

The development of suitable anode materials is far from satisfactory and is a major scientific challenge for a competitive sodium-ion battery technology. Metal sulfides have demonstrated encouraging results, but still suffer from sluggish kinetics and severe capacity decay associated with the phase change. Herein we show that rational electrode design, that is, building efficient electron/ion mixed-conducting networks, can overcome the problems resulting from conversion reactions. A general strategy for the preparation of hierarchical carbon-coated metal sulfide (MS⊂C) spheres through thermal sulfurization of metal glycerate has been developed. We demonstrate the concept by synthesizing highly uniform hierarchical carbon coated vanadium sulfide (V₂ S₃ ⊂C) spheres, which exhibit a highly reversibly sodium storage capacity of 777 mAh g^-1 at 100 mA g^-1 , excellent rate capability (410 mAh g^-1 at 4000 mA g^-1 ), and impressive cycling ability.