2D MOF-derived CoS1.097 nanoparticle embedded S-doped porous carbon nanosheets for high performance sodium storage

Abstract

Metal-organic framework (MOF) derived nanomaterials have attracted widely attention for energy storage application. Among them, cobalt sulfides are considered as one of the promising anodes for sodium-ion batteries due to their high theoretical capacity and low cost. In fact, different phases of cobalt sulfide tend to show component dependent electrochemical performance. Herein, we make full use of the nature of MOF to achieving phase-controlled synthesis of cobalt sulfides @S-doped porous carbon nanosheets (CoSx@SPCN) through the simultaneous carbonization and sulfidation. As result, CoS1.097@SPCN and Co9S8@SPCN are obtained respectively, and both of them show outstanding cycling stability and excellent rate performance. Ex-situ X-ray diffraction measurement further reveals the conversion reaction mechanism of CoS1.097@SPCN composite. Interestingly, we find that CoS1.097@SPCN would convert to Co9S8 in the first cycle. Compared with Co9S8@SPCN obtained directly by adjusting proportion of precursors, CoS1.097@SPCN composite shows higher reversible capacity of 231 mAh·g−1 at a current density of 5 A g−1 after 1800 cycles.