Methodology for enhancing the ionic conductivity of superionic halogen-rich argyrodites for all-solid-state lithium batteries

The development of high-performance all-solid-state lithium-ion batteries depends on the realization of solid-state electrolytes with high ionic conductivity. In this study, halogen-rich argyrodites with high ionic conductivities were fabricated, and their structural evolution was studied. In addition, the optimum heat treatment protocol for enhancing the ionic conductivity of halogen-rich argyrodites (Li 5.3 PS 4.3 Cl 1.7 ) was determined by interpreting the reaction mechanism. Structural and thermal analyses revealed that fast heating results in the formation of intermediates containing PS 4 3- units and Cl - ions, which remain in the material and decrease the ionic conductivity (~1.6 mS/cm at 25 °C). Surprisingly, slow heating, such as step heating, can promote the slow reaction that produces argyrodite from an intermediate, resulting in a high ionic conductivity (~5.0 mS/cm at 25 °C). Furthermore, we examined the performance of all-solid-state batteries assembled with Li 5.3 PS 4.3 Cl 1.7 as a solid-state electrolyte and found that the batteries employing Li 5.3 PS 4.3 Cl 1.7 treated by a slow heating protocol performs better than the batteries employing Li 5.3 PS 4.3 Cl 1.7 treated by a fast heating protocol, with an impressive specific capacity of 151.8 mAh/g at 1.0 C. Herein, we assert that further developing halogen-rich argyrodites as glass-ceramics may provide a long-sought solution to realizing ASSBs capable of achieving a high rate.