Precision Chemical Routes to Achieve Superior Oxyhalide Solid Electrolytes in Advanced All-Solid-State Batteries

/Li. As global efforts such as the HELENA Project and multiple academic breakthroughs converge on the development of safer and more scalable battery chemistries, oxyhalide SSEs stand out as a frontier platform with significant implications for future electric vehicles, grid storage, and aerospace energy systems.This Account provides a timely overview of the synthesis-structure-property relationships in oxyhalide SSEs. It meticulously charts the tailored chemical pathways employed in their synthesis, offering a comprehensive understanding of the design principles that govern their exceptional performance. We embark on a detailed examination of the crucial role played by diverse oxygen sources, spanning the spectrum from fundamental alkali metal oxides to sophisticated metal oxychlorides, in building the unique structural frameworks of these electrolytes. Unraveling the structure-property relationships is paramount, and this Account provides critical insights into how these oxygen sources profoundly influence the mechanisms of ion transport and ultimately dictate the overall ionic conductivity, a key metric for battery efficiency. Furthermore, we illuminate the essential characterization methodologies utilized to probe the structural, morphological, and electrochemical attributes of these fascinating materials, providing a toolkit for researchers in the field. Beyond fundamental synthesis and characterization, this Account casts a forward-looking lens onto the promising applications of oxyhalide SSEs in next-generation energy storage devices. By understanding the precise interplay between synthesis, structure, and performance, we aim to accelerate the development and implementation of safer, more energy-dense, and longer-lasting batteries for a sustainable future, impacting everything from electric vehicles to grid-scale storage.