Tailoring I-rich argyrodite sulfides via low-energy mechanical alloying for all-solid-state Li-metal batteries

Abstract

I-rich argyrodite sulfides have significant potential to enhance the interfacial stability of Li metal and suppress dendrite growth by forming a LiI-based interphase. However, conventional high-energy mechanical alloying often leads to poor Li-ion conductivity owing to the intrinsically low crystallization temperature of I-rich compositions, limiting their application as solid electrolytes. In this study, we synthesized I-rich argyrodites via low-energy mechanical alloying and successfully optimized the composition of Li_5.6PS_4.6Cl_0.8I_0.6. This electrolyte exhibited high Li-ion conductivity of 2.44 mS cm⁻¹, a moderate elastic modulus of 12.37 GPa, and a critical current density of 1.6 mA cm⁻². Furthermore, all-solid-state batteries employing this electrolyte demonstrated stable operation, achieving 99% capacity retention after 250 cycles at 1C. These results highlight that the low-energy alloying strategy effectively overcomes the limitations of conventional high-energy processes, thereby enabling the mechanical advantages of Cl–I substitution. We also demonstrate that enhancing the electrochemical and mechanical properties of I-rich argyrodites directly improves interfacial stability and cell durability.