Reversible Electrochemical Insertion of Lithium in Fine Grained Polycrystalline Powders of SnO₂

Abstract

Fine grained SnO₂ powders have been obtained using an unconventional method. It deals with the well known polymerization method starting from the metallic halide SnCl₄ with polyethylene oxide (PEO). With this method, SnO₂ powders, which are free from water and hydroxyl group contaminations and possess small crystallite size (≈50 A∘), are obtained by appropriate pyrolysis of the polymer. Consequently, these powders show good ability to insert reversibly lithium ions in the Li/Li⁺/LixSnO₂ cell. Indeed, by minimizing the size of the crystallites, the formation of defect-bonds is favored, particularly at the crystallite surface, acting as reversible (de)grafting sites of Li⁺. Finally, an easy-to-carry out method to determine the chemical diffusion coefficient of lithium has been proposed.