Si-doped Li6PS5I with enhanced conductivity enables superior performance for all-solid-state lithium batteries

Lithium argyrodites Li6PS5X (X = Cl, Br, I) show great potential as solid electrolytes for solid-state lithium batteries due to their high Li-ion conductivities and excellent electrode compatibility. However, the relatively low conductivity of Li6PS5I (10−6 mS/cm) compared to the other two compositions limits its applications. Herein, Si-doped Li6.5P0.5Si0.5S5I electrolyte is designed and synthesized with superior high conductivity of 3.6 mS/cm. Structural characterization proves the increase due to the anion disorder and volume expansion caused by Si-doping. However, the poor interfacial stability between layered oxide cathode LiNi0.6Co0.2Mn0.2O2 and Li6.5P0.5Si0.5S5I inhibits its battery performance. By introducing Li3InCl6 electrolyte in the configuration, the corresponding battery delivers high initial discharge capacity of 150.2 mAh/g and superior cyclability during 250 cycles at 0.5 C. This work offers design strategy to obtain Li6PS5I-based electrolytes for high performance solid-state batteries.