Potential-Resolved In Situ X‑ray Absorption Spectroscopy Study of Sn and SnO2 Nanomaterial Anodes for Lithium-Ion Batteries

This work provides detailed analysis of processes occurring in metallic Sn and SnO2 anode materials for lithium ion batteries during first lithiation, studied in situ with rapid continuous X-ray absorption spectroscopy (XAS). The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra provide information on dynamic changes in the Sn atomic environment, including type and number of neighboring atoms and interatomic distances. A unique methodology was used to model insertion of Li atoms into the electrode material structure and to analyze the formation of SnLi phases within the electrodes. Additionally, analysis of fully lithiated and delithiated states of Sn and SnO2 electrodes in the first two cycles provides insight into the reasons for poor electrochemical performance and rapid capacity decline. Results indicate that use of SnO2 is more promising than metallic Sn as an anode material, but more effort in nanoscale and atomic engineering of anodes is required for commercially feasible use of Sn-based materials.