Three-dimensional hollow spheres of porous SnO2/rGO composite as high-performance anode for sodium ion batteries

Three-dimensional porous SnO2/rGO hollow spheres with abundant internal void space were designed to resolve the volume expansion problem of SnO2-based anode materials for sodium-ion batteries. The unique hollow spheres with a porous wall of SnO2 decorated GO sheets were realized by a facile spray drying method. Nanosized SnO2 particles, which uniformly anchored on graphene sheets, in situ formed at the hydrolysis stage. Ethanol was used as porosity tuning agent to achieve template free pore-forming. The hollow spheres of porous SnO2/rGO composite show superior sodium storage performance with large specific capacity, remarkable cycling stability and excellent rate capability. The as-prepared SnO2/rGO composite delivered a high initial discharge capacity of 821.6 mA h g-1 at 200 mA g-1, and even after 1500 charge/discharge cycles a discharge capacity of 204 mA h g-1 still can be obtained. The SnO2/rGO composite achieved a capacity of 213.1 mA h g-1 at 500 mA g-1 after 500 cycles. And maintained an enhanced rate capability of 231 mA h g-1 at 2000 mA g-1. The excellent cyclability and high-rate capability of the composite can be ascribed to its unique hollow/porous architecture and the synergistic effect between SnO2 nanoparticles and the conductive matrix of rGOs.