Oxygen-Mediated Structural Modulation and Ion Transport in <i>x</i> Na ₂ O-TaCl ₅ Glass Electrolytes

Understanding the structure-property relationship in glass solid electrolytes (SEs) 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 multianion halide solid electrolytes, there are few systematic studies on how varying the oxygen content affects the local structure and ion transport. Here, we investigate a series of amorphous sodium oxychloride SEs with the composition <i>x</i>Na₂O-TaCl₅ (0.1 ≤ <i>x</i> ≤ 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 bonds that bridge the two or more metal chloride polyhedra, while <i>ab initio</i> molecular dynamics simulations clarify the distinct roles of bridging and nonbridging O^2- species. These findings not only provide mechanistic insights into oxygen-mediated glass formation but also establish guiding principles for multianion engineering in the design of next-generation solid electrolytes.