Oxygen-Mediated Structural Modulation and Ionic Transport in xNa2O-TaCl5 Glass Electrolytes

Understanding the structure-property relationship in glass solid electrolytes remains a major challenge due to their inherent disorder and the difficulty of probing local structures, particularly in relation to oxygen incorporation. Despite recent interest in multi-anion halide solid electrolytes, there are few systematic studies on how varying oxygen content affects the local structure and ion transport. Here, we investigate a series of amorphous sodium oxychloride SEs with the composition xNa2O-TaCl5 (0.1 ≤ x ≤ 1.5), revealing three distinct conductivity regimes and achieving a maximum of 4.1 mS cm–1 at room temperature. Synchrotron and lab X-ray total scattering and Raman spectroscopy indicate the gradual formation of Ta-O-Ta that bridges the two or more metal chloride polyhedral, while ab initio molecular dynamics simulations clarify the distinct roles of bridging and non-bridging O2− species. These findings not only provide mechanistic insights into oxygen-mediated glass formation but also establish guiding principles for multi-anion engineering in the design of next-generation solid electrolytes.