One-pot synthesis of carbon-coated SnO ₂ nanocolloids with improved reversible lithium storage properties

We report a simple glucose-mediated hydrothermal method for gram-scale synthesis of nearly monodisperse hybrid SnO ₂ nanoparticles. Glucose is found to play the dual role of facilitating rapid precipitation of polycrystalline SnO ₂ nanocolloids and in creating a uniform, glucose-derived, carbon-rich polysaccharide (GCP) coating on the SnO ₂ nanocores. The thickness of the GCP coating can be facilely manipulated by varying glucose concentration in the synthesis medium. Carbon-coated SnO ₂ nanocolloids obtained after carbonization of the GCP coating exhibit significantly enhanced cycling performance for lithium storage. Specifically, we find that a capacity of ca. 440 mA h/g can be obtained after more than 100 charge/discharge cycles at a current density of 300 mA/g in hybrid SnO ₂-carbon electrodes containing as much as 1/3 of their mass in the low-activity carbon shell. By reducing the SnO ₂-carbon particles with H ₂, we demonstrate a simple route to carbon-coated Sn nanospheres. Lithium storage properties of the latter materials are also reported. Our results suggest that large initial irreversible losses in these materials are caused not only by the initial, presumably irreversible, reduction of SnO ₂ as generally perceived in the field, but also by the formation of the solid electrolyte interface (SEI). © 2009 American Chemical Society.