Hydrothermal Synthesis Of SnO₂/C Microsphere And Its Electrochemical Performance

Li-ion batteries（LIBs） with high energy density and supercapacitors with high power density have attracted significant attention due to their high energy efficiency, long cycle life and environmentally friendly nature. Such outstanding advantages make them good candidates for applications in hybrid electric vehicles, portable electronics, large industrial equipments, and other renewable energy storages. The electrochemical properties of LIBs and supercapacitors mainly depend on their electrode materials, unfornately, currently used commercial electrode materials with low energy density cannot meet the higher requirements of future systems, alternative materials are highly desired.In present work, SnO₂/C microspheres were prepared by a facile hydrothermal method with SnCl4·5H₂O and soluble starch as the precursors of SnO₂ and carbon material, respectively. Porous SnO₂/C microspheres were obtained by subsequent ZnCl2 activation. The soluble starch used as carbon source plays a key role in the formation of spherical SnO₂/C microspheres, and the hydrothermal synthesis mechanism of SnO₂/C microspheres has been proposed. Both SnO₂/C microspheres and porous SnO₂/C microspheres are mainly in spherical shape with particle size of 1-5 μm and SnO₂ nanoparticles are homogeneously distributed in carbon microspheres. The supercapacitor electrodes based on porous SnO₂/C microspheres show higher specific capacitance, lower equivalent series resistance and better rate capability than the electrodes based on porous carbon microspheres prepared via the same method, indicating a promising application prospect of porous SnO₂/C microspheres in supercapacitors in the future.SnO₂/C microsphere/graphene composites were prepared by a facile hydrothermal method. The effects of hydrothermal temperature、reaction time、the amount of SnCl₂·2H₂O、 urea and post heat-treatment on the electrochemical performances of the obtained SnO₂/C microsphere/graphene composites were investigated. SnO₂/C microsphere/graphene prepared with the mass ratio of graphene oxide（GO）、SnCl₂·2H₂O and glucose at 1:1:1, hydrothermal temperature at 160 oC and reaction time at 12 h has a specific capacitance of 74 F/g at 20 mA/g of the current density.Double layered core-shell SnO₂ microspheres have been synthesized by a facile hydrothermal method with a post heat-treatment in air. SnO₂/C microspheres, double layered core-shell SnO₂ microspheres and SnO₂ particles deliver reversible discharge capacities of 568 mAh/g, 935 mAh/g at a constant current density of 100 mA/g in the 2nd cycle, respectively, which are much higher than the theoretical capacity of graphite（372 mAh/g）. SnO₂/C microspheres exhibit superior rate capability and cyclic stability while double layered core-shell SnO₂ microspheres show improved electrochemical performances than SnO₂ particles. The Li B electrodes based on SnO₂/C microspheres deliver a reversible discharge capacity of 379 mAh/g（67% retention） even after the 50 th cycle, suggesting SnO₂/C microspheres a promising candidate for LiB anode. Based on this present work, SnO₂/C microspheres show good application future in the field of energy storage.