4.8 V and All‐Climate (−60 to 55°C) All‐Solid‐State Batteries Enabled by Dual‐Phase Symbiotic Halide Solid Electrolytes

ABSTRACT Overcoming the intrinsic trade‐off between high‐voltage compatibility, thermal stability, and low‐temperature ionic conductivity in halide solid electrolytes remains a critical challenge for advancing all‐solid‐state lithium batteries (ASSLBs). Here, we propose a chemical symbiosis strategy to design a dual‐phase halide electrolyte integrating nanocrystalline LiAlCl 4 with amorphous Li‐M‐O‐Cl (M = Ta/Al) phases. This innovative architecture synergistically combines the ultra‐high‐voltage stability (up to 4.8 V) of the crystalline phase with the low‐energy‐barrier ion transport pathways in the amorphous matrix. The designed electrolyte exhibits exceptional electrochemical performance under extreme conditions. It enables the ASSLBs to achieve a 90.5% capacity retention after 100 cycles at 4.8 V, maintain a specific capacity of 133 mA h g −1 over 500 cycles at 55 °C and 3 C, and deliver unprecedented low‐temperature performance with a capacity of 109.6 mA h g −1 and 1800‐h stability under dual extreme conditions of −60°C and 4.8 V. Comprehensive characterization reveals the amorphous phase facilitates facile percolation networks for rapid Li + conduction, while the nanocrystalline domains maintain structural integrity against high‐voltage degradation. The electrolyte's broad compatibility with diverse cathodes (LiCoO 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) also underscores its versatility for high‐energy ASSLBs.