Synthesis of Uniquely Structured SnO₂ Hollow Nanoplates and Their Electrochemical Properties for Li-Ion Storage

A new mechanism for the transformation of nanostructured metal selenides into uniquely structured metal oxides via the Kirkendall effect, which results from the different diffusion rates of metal and Se ions and O₂ gas, is proposed. SnSe nanoplates are selected as the first target material and transformed into SnO₂ hollow nanoplates by the Kirkendall effect. SnSe-C composite powder, in which SnSe nanoplates are attached or stuck to amorphous carbon microspheres, transforms into several tens of SnO₂ hollow nanoplates by a thermal oxidation process under an air atmosphere. Core–shell-structured SnSe-SnSe₂@SnO₂, SnSe₂@SnO₂, Se-SnSe₂@SnO₂, and Se@SnO₂ and yolk–shell-structured Se@void@SnO₂ intermediates are formed step-by-step during the oxidation of the SnSe nanoplates. The uniquely structured SnO₂ hollow nanoplates have superior cycling and rate performance for Li-ion storage. Additionally, their discharge capacities at the 2nd and 600th cycles are 598 and 500 mA h g^-1, respectively, and the corresponding capacity retention measured from the 2nd cycle is as high as 84%.