New Insight into the Reaction Mechanism for Exceptional Capacity of Ordered Mesoporous SnO₂ Electrodes via Synchrotron-Based X-ray Analysis

Tin oxide-based materials, operating via irreversible conversion and reversible alloying reaction, are promising lithium storage materials due to their higher capacity. Recent studies reported that nanostructured SnO 2 anode provides higher capacity beyond theoretical capacity based on the alloying reaction mechanism; however, their exact mechanism remains still unclear. Here, we report the detailed lithium storage mechanism of an ordered mesoporous SnO 2 electrode material. Synchrotron X-ray diffraction and absorption spectroscopy reveal that some portion of Li 2 O decomposes upon delithiation and the resulting oxygen reacts with Sn to form the SnO x phase along with dealloying of Li x Sn, which are the main reasons for unexpected high capacity of an ordered mesoporous SnO 2 material. This finding will not only be helpful in a more complete understanding of the reaction mechanism of Sn-based oxide anode materials but also will offer valuable guidance for developing new anode materials with abnormal high capacity for next generation rechargeable batteries.