Two‐Step Fluorination Route Enabling Li 2 ZrCl 6 Solid Electrolytes Towards High‐Voltage Li Batteries

Cost‐effective Zr‐based chloride electrolytes are attractive for practical all‐solid‐state lithium batteries, but their limited oxidative stability restricts their use with high‐voltage cathodes. Fluorine incorporation can enhance the high‐voltage stability of chloride electrolytes, yet the strong electrostatic interaction between F − and Li + and the kinetic limitations of conventional one‐step synthesis often compromise Li + transport and compositional homogeneity. Herein, we propose a two‐step synthesis strategy coupled with Zn/F co‐modification to regulate anion incorporation and local structural disorder in Li 2 ZrCl 6 ‐based electrolytes. This stepwise pathway promotes multicomponent solid‐state reactions, facilitates Cl/F anion co‐occupancy, and resolves the tradeoff between high‐voltage stability and ionic transport. The optimized composition achieves an improved overall performance including oxidation stability, mechanical deformability, and ion transport. When paired with high‐voltage LiCoO 2 cathodes, the optimized solid electrolyte enables a high discharge capacity, together with good rate capability and cycling performance. Interfacial analyses reveal that F‐containing species redistribute toward the cathode surface during cycling, forming a LiF‐rich cathode–electrolyte interphase that suppresses oxidative decomposition and maintains intimate solid–solid contact. This work provides an effective reaction pathway engineering strategy for developing high‐voltage‐compatible Zr‐based halide electrolytes through dual‐halogen chemistry and aliovalent cation modification.