The higher the better? Thermal stability and electrochemical properties of Cl-rich lithium argyrodite solid state electrolyte

Argyrodite Li 6-x PS 5-x Cl 1+x with high ionic conductivity and excellent mechanical performance is an attractive solid electrolyte candidate for all-solid-state lithium batteries (ASSLBs). Adjusting Cl content is an effective strategy to enhance the ionic conductivity, however its effect on the thermal stability remain uncovered. Herein, our study shows that the increase of Cl content in Li 6-x PS 5-x Cl 1+x significantly enhances the ionic conductivity and electrochemical properties but significantly reduces its thermal stability. We reveal that the thermal stability of Li 6-x PS 5-x Cl 1+x is heavily dependent on its Cl content and can be significantly enhanced by elemental doping. LiNi 0.6 Co 0.2 Mn 0.2 O 2 based ASSLBs using Cl-rich argyrodite with pure phase shows better cycle performance. Achievements from this study could serve as a guidance for optimizing and applicating argyrodite solid electrolytes towards high-performance and safe ASSLBs.