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

Abstract 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, AlCl 3 , and AlCl 3 ·6H 2 O. 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 LiAlCl 4 crystallites and large amounts of amorphous [Al a O b Cl 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 a O b Cl 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.