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

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 Li₂O with cost-effective Ta₂O₅ 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 LiCoO₂, delivering robust cycling stability (>80% capacity retention after 450 cycles). Validated with alternative oxygen sources (Nb₂O₅), this pseudo-catalyst approach demonstrates versatility, pioneering accelerated synthesis protocols for halide SSEs and beyond.