Oxychloride Polyanion Clustered Solid‐State Electrolytes via Hydrate‐Assisted Synthesis for All‐Solid‐State Batteries

Solid-state electrolytes (SSEs) play a vital role in the development of high-energy all-solid-state batteries. However, most adopted mechanical ball milling and/or high-temperature annealing are ineffective approaches for large-scale synthesis. Herein, a universal and scalable hydrate-assisted strategy for the synthesis of oxychloride SSEs is developed based on the chemical reaction among alkali chlorides, AlCl₃, and AlCl₃·6H₂O. The synthesized aluminum-based oxychloride SSEs possess a high Li⁺ conductivity over 1 mS cm^-1 at 30 °C. The final aluminum-based oxychloride SSEs are structurally heterogeneous with nm-sized LiCl-like and LiAlCl₄ crystallites and large amounts of amorphous [Al_aO_bCl_c]^{(2 b + c -3 a )-} components. Faster local mobility of Li⁺ ions in amorphous structures is verified and is attributable to weakened Li⁺-X^- interactions ensured by the [Al_aO_bCl_c]^{(2 b + c -3 a )-} polyanions. The potential applications for this synthesis technique are further demonstrated by kilogram-scale reactions and synthesis of other oxychloride SSEs including zirconium-based and tantalum-based analogs. These findings not only provide a new simple, scalable, and energy-efficient synthesis route for oxychloride SSEs but also further promote their application in all-solid-state batteries.