Oxygen-Mediated Nanocrystalline-Amorphous LaCl3-Based Composite Electrolytes for All-Solid-State Lithium Batteries

Chlorine-based halide solid-state electrolytes (SSEs) have emerged as promising candidates for all-solid-state lithium batteries (ASSLBs) due to their high ionic conductivities and oxidative stability. Among them, LaCl3-based SSEs feature a non-close-packed lattice that provides intrinsically wide one-dimensional transport channels; however, their practical application is often constrained by rigid crystalline transport pathways and grain boundary resistance. Inspired by dual-anion engineering, by substituting LiCl with Li2O in Li0.388Ta0.238La0.475Cl3, a series of LaCl3-based composite electrolytes, Li2xTa0.25La0.5Cl2.75Ox (0.15 ≤ x ≤ 0.2, LTLCO), were synthesized. Atomic and local structure analysis reveals that, although elements are uniformly distributed at the macroscopic level, distinct local structural variations exist. Oxygen preferentially coordinates with Ta to form distorted octahedral Ta-Cl-O polyhedra, while the LaCl3 framework maintains structural integrity as a rigid backbone. The optimized Li0.35Ta0.25La0.5Cl2.75O0.175 SSE achieves a high ionic conductivity of 2.05 mS cm-1 at 30 °C and exhibits superior mechanical deformability, effectively mitigating interfacial failure in ASSLBs. ASSLBs assembled with LiNi0.83Co0.11Mn0.06O2 (NCM83) cathodes demonstrate exceptional rate performance and long-term cycling stability with 83.4% capacity retention after 300 cycles.