A crystalline-amorphous heterostructured oxyhalide electrolyte for high-performance all-solid-state lithium batteries

All-solid-state lithium batteries (ASSLBs) are poised to revolutionize energy storage technologies, but the development of solid-state electrolytes (SSEs) that simultaneously offer high ionic conductivity, mechanical deformability, and high-voltage stability remains a formidable challenge. Here, we report a novel heterogeneous oxyhalide SSE, LiAl 0.5 Ga 0.5 Cl 2.5 O 0.75 (LAGCO), featuring LiCl nanocrystals embedded within an amorphous Li–M–Cl–O (M = Al, Ga) matrix. This unique architecture, synthesized via a facile mechanochemical route, integrates mechanical resilience with continuous, isotropic Li + transport pathways. LAGCO exhibits a high ionic conductivity of 0.822 mS cm -1 at 25 °C and an intermediate Young's modulus of 2.612 GPa. Its mechanical compliance enables intimate interfacial contact and effectively buffers volumetric strain during cycling. When paired with the high-nickel LiNi 0.88 Co 0.07 Mn 0.05 O 2 (NCM811) cathode with a high active-materials loading of 8.91 mg cm -2 , the LAGCO-based ASSLBs deliver a discharge capacity of 167.67 mAh g -1 . Moreover, the cell exhibits outstanding long-term stability, retaining 86.02% of its capacity after 1000 cycles at 0.5 C (NCM811 loading: 5.35 mg cm -2 ). Furthermore, the estimated raw material cost (40.80 USD kg -1 ) of LAGCO is significantly lower than that of many advanced halide electrolytes containing costly elements. This work provides a potentially scalable and cost-effective strategy for designing heterogeneous SSEs with optimized mechanical and electrochemical properties for next-generation energy storage.