Facile synthesis of lithium argyrodite Li5.5PS4.5Br1.5 with high ionic conductivity for all-solid-state batteries

Bromine-rich lithium argyrodite electrolytes with high ionic conductivity and low cost are promising for the replacement of flammable liquid electrolytes and separators in lithium-ion batteries. However, the synthesis process of argyrodite electrolytes is usually complex and time-consuming. We use a facile solid-state reaction method to obtain a highly Li-ion conductive Li 5.5 PS 4.5 Br 1.5 (LPSB). The influence of annealing temperature on the phase and ionic conductivity of the LPSB was investigated for the first time. High ionic conductivity of 5.21 × 10 −3 S cm −1 at room temperature for the LPSB with minor LiBr impurity was achieved by direct annealing at 430°C for 8 h. The In/InLi | LPSB | LiCoO 2 @ LiNb 0.5 Ta 0.5 O 3 (LCO(coated))-LPSB cell with 8.53 mg cm −2 LCO loading shows a discharge capacity of 102 mAh g −1 with high-capacity retention of 93% after 70 cycles at 0.5 mA cm −2 at 30°C.