Sandwiched spherical tin dioxide/graphene with a three-dimensional interconnected closed pore structure for lithium storage

Abstract

Low reversion of lithium oxide (Li₂O) and the tin (Sn) coarsening causing irreversible capacity loss is the main reason for the poor cycle performance in tin dioxide (SnO₂) based composites. In this research, a novel sandwiched spherical tin dioxide/graphene with a three-dimensional interconnected closed pore structure is synthesized. The microstructural characterization shows that the spherical graphene with submicron sized diameters interconnects with each other forming an interconnected flexible conductive network, whereas a large number of SnO₂ nanoparticles (approximately 5 nm) are limited homogeneously in between the interlayers of the sphere-like graphene shell. The sandwich structure of the SnO₂/graphene and the closed graphene sphere can provide double protection for the SnO₂. When it is used as an anode material for energy storage, the generated Li₂O can remain in close contact with Sn to make the conversion reaction (SnO₂ + 4Li⁺ + 2e⁻ ↔ Sn + Li₂O) highly reversible in situ and the reversibility even does not diminish markedly after 100 cycles. A high reversible specific capacity of 914.8 mA h g⁻¹ is expressed in the sandwiched spherical SnO₂/graphene composite at 100 mA g⁻¹ after 100 cycles, which is significantly higher than that of a SnO₂/graphene aerogel with an open pore structure.