A General Deep Eutectic Solvent‐Mediated Scalable Preparation of Halide Solid‐State Electrolytes for All‐Solid‐State Batteries

In the pursuit of high‐energy‐density all‐solid‐state lithium batteries, halide solid‐state electrolytes (HSSEs) have attracted increasing interest due to their high ionic conductivity and superior high‐voltage stability. Developing cost‐effective and scalable preparation methods is essential for their practical deployment, yet the current mainstream solid‐state preparation routes either require stringent environmental control with prohibitive costs or suffer from low efficiency. Herein, we report a universal deep eutectic solvent (DES)‐mediated wet‐chemical method that enables the efficient and scalable preparation of HSSEs. Taking Li 3 YCl 6 as a typical HSSE, we revealed the competitive coordination and hydrogen‐bond formation mechanisms through combined modeling and experiments. This method shows low cost, and good scalability for various HSSEs, and the resultant HSSEs show a similar conductivity (>0.30 mS cm −1 ) as that prepared by the solid‐state mechanical method. Notably, the humidity‐degraded HSSEs can also be readily regenerated by this method. The all‐solid‐state lithium batteries assembled with the resultant Li 3 YCl 6 deliver impressive performance, achieving a high initial Coulombic efficiency of 98.6% with a LiCoO 2 cathode and a remarkable discharge capacity of 195.9 mAh g −1 with a single‐crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode. This work establishes a new paradigm for the sustainable and scalable manufacturing of HSSEs for next‐generation all‐solid‐state batteries.