Spray-Drying-Induced Assembly of Skeleton-Structured SnO₂/Graphene Composite Spheres as Superior Anode Materials for High-Performance Lithium-Ion Batteries

Three-dimensional skeleton-structured assemblies of graphene sheets decorated with SnO₂ nanocrystals are fabricated via a facile and large-scalable spray-drying-induced assembly process with commercial graphene oxide and SnO₂ sol as precursors. The influences of different parameters on the morphology, composition, structure, and electrochemical performances of the skeleton-structured SnO₂/graphene composite spheres are studied by XRD, TGA, SEM, TEM, Raman spectroscopy, and N₂ adsorption-desorption techniques. Electrochemical properties of the composite spheres as the anode electrode for lithium-ion batteries are evaluated. After 120 cycles under a current density of 100 mA g^-1, the skeleton-structured SnO₂/graphene spheres still display a specific discharge capacity of 1140 mAh g^-1. It is roughly 9.5 times larger than that of bare SnO₂ clusters. It could still retain a stable specific capacity of 775 mAh g^-1 after 50 cycles under a high current density of 2000 mA g^-1, exhibiting extraordinary rate ability. The superconductivity of the graphene skeleton provides the pathway for electron transportation. The large pore volume deduced from the skeleton structure of the SnO₂/graphene composite spheres increases the penetration of electrolyte and the diffusion of lithium ions and also significantly enhances the structural integrity by acting as a mechanical buffer.