Interfacial Coordination Engineering to Boost Li‐Ion Conduction in Economic Zr‐Based Halide Electrolytes

Halide solid electrolytes (HSEs) have seen rapid progress in the development of all‐solid‐state lithium batteries (ASSLBs), offering favorable lithium‐ion transport properties, broad electrochemical stability, and strong interfacial compatibility with high‐voltage oxide cathodes. However, developing HSEs that simultaneously offer high ionic conductivity and low cost remains a significant challenge. Most high‐conductivity halides rely on expensive metal elements, whereas cost‐effective Zr‐based halides are limited by their relatively low ionic conductivity. In this study, a new composite electrolyte (LA/LZCO) is developed via an interfacial coordination reaction between Zr‐based oxychlorides (LZCO) and Li1.3Al0.3Ti1.7(PO4)3 (LATP). The coordination between PO43− groups in LATP and Zr4+ in LZCO induces local structural disorder, promoting LZCO amorphization. As a result, the ionic conductivity of LA/LZCO composite electrolyte is enhanced by more than twofold compared to LZCO, reaching 2.81 mS cm−1, among one of the highest reported for Zr‐based halide electrolytes. When integrated into ASSLBs with NCM83125 cathodes, the composite electrolyte enables excellent cycling stability, with 92.4% and 87.5% capacity retention after 1000 cycles at 0.5 and 2 C under 4.25 V. Even at an elevated cut‐off voltage of 4.5 V, 85.1% capacity is retained after 380 cycles, highlighting the promise of this composite strategy for high‐energy, long‐life ASSLBs.