Simple synthesis of hollow tin dioxide microspheres and their application to lithium-ion battery anodes

Hollow tin dioxide (SnO2) microspheres were synthesized by the simple heat treatment of a mixture composed of tin(IV) tetrachloride pentahydrate (SnCl4 center dot 5H(2)O) and resorcinol-formaldehyde gel (RF gel). Because hollow structures were formed during the heat treatment, the pre-formation of template and the adsorption of target precursor on template are unnecessary in the current method, leading to simplified synthetic procedures and facilitating mass production. Field-emission scanning electron microscopy (FE-SEM) images showed 1.7-2.5 mu m sized hollow spherical particles. Transmission electron microscopy (TEM) images showed that the produced spherical particles are composed of a hollow inner cavity and thin outer shell. When the hollow SnO2 microspheres were used as a lithium-battery anode, they exhibited extraordinarily high discharge capacities and coulombic efficiency. The reported synthetic procedure is straightforward and inexpensive, and consequently can be readily adopted to produce large quantities of hollow SnO2 microspheres. This straightforward approach can be extended for the synthesis of other hollow microspheres including those obtained from ZrO2 and ZrO2/CeO2 solid solutions.