Minutes‐Scale Ultrafast Synthesis of New Oxyhalides Solid Electrolytes with Interfacial Ionic Conduction for All‐Solid‐State Batteries

Abstract Halide solid‐state electrolytes (SSEs) show exceptional promise for all‐solid‐state batteries (ASSBs), yet their dependence on prolonged ball milling to achieve required ionic conductivity critically compromises energy efficiency. Here, we report a novel Zr‐based oxyhalide SSE (oh‐LZC) synthesized via an ultrafast ball‐milling process (18 min)—a record for halide SSEs. Remarkably, extending processing to just 1.5 h boosts ionic conductivity from 0.11 to 1.09 mS cm −1 —outperforming most reported Zr‐based halides at equivalent synthesis durations. Critical to this advance is the strategic substitution of expensive Li 2 O with cost‐effective Ta 2 O 5 as the oxygen source—which simultaneously acts as a core‐like pseudo‐catalyst. During ultrafast milling, this drives formation of a shell‐like conductive amorphous oxyhalide, directly enabling a novel interfacial conduction mechanism as confirmed by high‐resolution microscopy and spectroscopy. ASSBs assembled with oh‐LZC synthesized in 18 min exhibit excellent compatibility with uncoated LiCoO 2 , delivering robust cycling stability (>80% capacity retention after 450 cycles). Validated with alternative oxygen sources (Nb 2 O 5 ), this pseudo‐catalyst approach demonstrates versatility, pioneering accelerated synthesis protocols for halide SSEs and beyond.