Nanosize SnO₂ confined in the porous shells of carbon cages for kinetically efficient and long-term lithium storage.

We explore a hybrid material consisting of SnO(2) nanoparticles (NPs) embedded in the porous shells of carbon cages (SnO(2)-PSCC). The hybrid material exhibits improved kinetics of lithiation-delithiation and high reversible capacity, and excellent cyclic stability without capacity loss over 100 cycles at 500 mA g(-1) with a coulombic efficiency close to 100% after the initial cycle. This can be ascribed to the high electrical conductivity, the hierarchical porosity and the confinement effect of the PSCC on the volume change of SnO(2) NPs. The material has a large reversible capacity of 460 mA h g(-1) at a high current density of 5 A g(-1) due to a short ion diffusion length in the bulk and large number of inter-pore ion transport channels. These results provide insight into improving the lithium storage performance of SnO(2) by facilitating the reaction kinetics and indicate that this hybrid material has great potential for use in high-rate and durable lithium ion batteries.