New sulhalide solid electrolytes with soft and high lithium ionic conductivity for all-solid-state batteries

All-solid-state batteries (ASSBs) are widely regarded as a promising successor to conventional lithium-ion batteries owing to their enhanced safety and high energy-density. A key challenge lies in developing solid electrolytes (SEs) that simultaneously exhibit high ionic conductivity, negligible electronic conductivity, and strong electrochemical stability. Although chloride-based electrolytes such as Li 3 InCl 6 (LIC) offer oxidation stability and compatibility with oxide cathodes, their moderate ionic conductivity limits practical applications. Herein, we propose an anionic regulation strategy to enhance Li + transport by introducing sulfur into the chloride framework, constructing a new class of sulhalide solid electrolytes (Li–In–S–Cl). Benefiting from the larger ionic radius and lower electronegativity of sulfur, Li + –anion interactions are weakened, thereby reducing the migration energy barrier. The optimized Li 3.2 InCl 6 S 0.1 electrolyte sintered at 420 °C achieves a high room-temperature ionic conductivity of 2.61 mS cm −1 and an ultralow electronic conductivity of 1.2 × 10 −9 S cm −1 . Structural analysis reveals that sulfur incorporation induces a homogeneous amorphous phase, enabling isotropic ion transport and reduced grain boundary resistance. Moreover, the electrolyte exhibits a wide electrochemical stability window of 1.4–4.16 V (vs. Li + /Li) and favorable rate performance. This work provides a viable strategy for designing high-performance halide-based SEs toward practical ASSBs.