Real‐Time Phase Monitoring of Solid‐State Electrolytes: A Glovebox‐Integrated In Situ Wide‐Angle X‐Ray Scattering

Lithium‐ion batteries are regarded as highly advanced energy storage technologies, but the organic liquid electrolytes are highly flammable, posing significant safety risks. All‐solid‐state electrolytes are foreseen to safer alternative with superior electrochemical performance, and among them, halide solid‐state electrolytes (HSSEs) represent a breakthrough in next‐generation battery technologies. Herein, an in situ wide‐angle X‐ray scattering setup that is fully integrated into a glovebox is demonstrated, enabling real‐time monitoring of phase changes under controlled inert atmospheric conditions. To showcase the capabilities of the system, the thermal stability and phase transitions of two HSSEs: Li 2 ZrCl 6 (LZC) and Fe‐substituted Li 2.25 Zr 0.75 Fe 0.25 Cl 6 (LZFC) is investigated. The measurements reveal that LZC exhibits excellent thermal stability, maintaining its trigonal crystalline structure up to 200 °C. In contrast, trigonal LZFC remains stable up to 100 °C but begins decomposing into LiCl beyond this temperature. The findings underscore LZC's superior performance as a promising electrolyte for high‐performance energy storage systems and highlight the critical role of advanced in situ characterization techniques in optimizing materials for solid‐state battery technologies.