Achieving superior ionic conductivity of Li6PS5I via introducing LiCl

Li6PS5I electrolyte shows significant potential as solid electrolytes due to its low cost and high stability. However, the poor room temperature Li-ion conductivity (10−6 S/cm) limits its applications in solid-state batteries. This work aims to increase the conductivity of Li6PS5I by introducing LiCl in the structure using high-rotation mechanical milling. Structure analysis confirms that a minor dopant of Cl− can form a single-phase of Li6PS5ClxI1-x argyrodite electrolytes, while a large doping amount yields a mixture of the Li6PS5I and Li6PS5Cl phases. The modified electrolytes with “composition” Li6PS5Cl0.7I0.3 show the highest room temperature Li-ion conductivity among the milled and sintered sample, 7.37 × 10−4 and 2.33 × 10−3 S/cm, both of which are much higher than the conductivity of pristine Li6PS5I. Solid-state batteries using the above solid electrolytes combined with LiNbO3-coated LiNi0.7Mn0.2Co0.1O2 cathode and LiIn anode display excellent electrochemical performances. The battery using annealed Li6PS5Cl0.7I0.3 electrolyte delivers improved discharge capacities and extended cycling performances at different operating temperatures. This work provides an effective strategy to design high conductivity Li6PS5I-based solid electrolytes for solid-state batteries.