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 Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP). The coordination between PO₄ ^3- 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.