Advancing Interface Engineering for Non-Close-Packed Halide-Based All-Solid-State Lithium Batteries

The growing demand for high-energy-density batteries has positioned all-solid-state lithium batteries (ASSBs) as a leading technology with the potential for significant impact. As a key material for ASSBs, halide solid electrolytes (SEs) have emerged as a current research hotspot, especially for non-close-packed halide SEs with ultrahigh ionic conductivity (>10 mS cm–1 at room temperature). However, they still suffer from insufficient compatibility with high-voltage cathode materials (>4.3 V vs Li/Li+) and poor reduction limit (>0.9 V vs Li/Li+). Based on the recent advancements, those challenges have been alleviated through cation/anion regulation engineering and the introduction of extra interlayers. This review distinguishes itself from previous works by systematically examining interfacial failure mechanisms and modification strategies for emerging non-close-packed halide SEs. Surpassing conventional halide SEs with close-packed structures, the non-close-packed ones enable broader cationic/anionic doping versatility, including multi-element co-doping and facilitate the improvement of interfacial engineering through more diverse interlayers. This focused review is expected to inspire more research on improving the interfacial stability between non-close-packed halide SEs and electrode materials, which would promote the development of high-performance ASSBs.