Li_1.6AlCl_3.4S_0.6: A low-cost and high-performance solid electrolyte for solid-state batteries

Solid electrolytes (SEs) are crucial for advancing next-generation rechargeable battery technologies, but their commercial viability is partially limited by expensive precursors, unscalable synthesis, or low ionic conductivity. Lithium tetrahaloaluminates offer an economical option but exhibit low Li+ conductivities with high activation energy barriers. This study reports the synthesis of lithium aluminum chalcohalide (Li1.6AlCl3.4S0.6) using inexpensive precursors via one-step mechanochemical milling. The resulting Cl-S mixed-anion sublattice significantly improves the ionic conductivity from 0.008 mS cm-1 for LiAlCl4 to 0.18 mS cm-1 for Li1.6AlCl3.4S0.6 at 25 C. Structural refinement of the high-resolution XRD patterns and 6Li magic-angle-spinning (MAS) NMR quantitative analysis reveals the formation of tetrahedrallycoordinated, face- and edge-shared LiClxSy octahedra that facilitate 3D Li+ transport. Ab initio molecular dynamics (AIMD) simulations on Li1.6AlCl3.4S0.6 support an enhanced 3D network for Li+ migration with increased diffusivity. All-solid-state battery (ASSB) half-cells using Li1.6AlCl3.4S0.6 exhibit high-rate and long-term stable cycling performance. This work highlights the potential of Li1.6AlCl3.4S0.6 as a costeffective and high-performance SE for ASSBs.