Synthesis of Br-rich argyrodite electrolytes enables all-solid-state batteries with superior battery performances at different operating temperatures

Solid-state batteries have attracted significant attention owing to their high energy density and high safety. Nevertheless, highly conductive solid electrolytes with ultrafast Li-ion mobility are greatly demanded. In this work, bromine-rich argyrodite electrolytes have been synthesized by the typical high-rotation milling followed by an annealing method. The precursor with pure argyrodite structure is first obtained and a subsequent sintering process is applied to enhance the Li-ion conductivity. Br dopant is tailored to obtain the optimum composition with the highest conductivity. Li_5.6PS_4.6Br_1.4 electrolyte delivers a high conductivity of 6.91 mS/cm at room temperature. The solid-state battery using the pristine LiNi_0.6Mn_0.2Co_0.2O₂ cathode and Li-In anode shows a high discharge capacity of 143.4 mAh g⁻¹ and excellent capacity retention of 92.3% after 100 cycles at 0.2C under room temperature. Moreover, the assembled all-solid-state battery also displays high discharge capacities of 156.6 mAh g⁻¹ at 0.2C under 60 °C and 97.1 mAh g⁻¹ at 0.02C under -20 °C. Due to the good lithium metal compatibility of Li_5.6PS_4.6Br_1.4 electrolyte, LiNi_0.6Mn_0.2Co_0.2O₂/Li_5.6PS_4.6Br_1.4/Li all-solid-state Li metal is successfully constructed and displays excellent performances.