Dynamic Li‐S Coordination Boosted Superionic Conduction in Cubic LiBS ₂ Solid Electrolyte

ABSTRACT Li thioborate solid electrolytes (SEs) have recently emerged as a typical SE system with theoretical room temperature (RT) ionic conductivity of 80 mS cm −1 . However, experimental explorations on this SE system are still insufficient, leading to a large gap between the experimental performance and the theoretical prediction. In this work, a high‐pressure high‐temperature method is developed for the first time to prepare the new Li thioborate of LiBS 2 with cubic and tetragonal phases. The cubic LiBS 2 SE exhibits the highest RT ionic conductivity of 0.43 mS cm −1 . The diffusion of the Li ions is accompanied with collective local Li‐S coordination and de‐coordination, termed as “Li‐S dynamic coordination”, which are beneficial for lowering the energy barrier and boosting the superionic conduction. The findings in this work can be applied as theoretical guidance for the design of novel sulfide based SE systems.