A Scalable and Versatile Synthetic Strategy of Halide Electrolytes for High-Performance All-Solid-State Lithium Batteries

Halide electrolytes have emerged as promising candidates due to their high ionic conductivity, good compatibility with high-voltage cathodes, and excellent mechanical properties. However, traditional synthesis methods, such as high-energy ball milling, face challenges, including high energy consumption, long processing times, and limited scalability. Additionally, the large particle size of electrolytes results in poor interfacial contact and ion transport, making it difficult to achieve stable cycling in all-solid-state batteries (ASSLBs). Here, we developed a scalable ammonia-assisted hydrolysis combined with a freeze-drying (AAH-FD) method for synthesizing halide electrolytes. The Li₃YCl₆ electrolyte synthesized via AAH-FD exhibited an orthorhombic (Pnma) structure with a high ionic conductivity of 0.50 mS cm^–1. The method was also successfully applied to synthesize Li₃ErCl₆ and Li₃HoCl₆, confirming its versatility. ASSLBs with AAH-FD Li₃YCl₆ demonstrated superior electrochemical performance, including a higher discharge capacity, better rate capability, and enhanced cycling stability. The LiCoO₂-based ASSLB retained 77.6% of its capacity after 400 cycles at 1C, while the NCM622-based battery retained 79%. These improvements result from the optimized microstructure, smaller particle size, and reduced interfacial resistance, enhancing the lithium-ion transport. Moreover, AAH-FD enables 100 g of batch production, demonstrating excellent scalability. This study establishes AAH-FD as an efficient, versatile, and scalable synthesis strategy, offering a promising approach for the next-generation high-performance ASSLBs.