Unravelling the O-doping effect on chemical/electrochemical stability of Li5.5PS4.5Cl1.5 for all-solid-state lithium batteries

Chlorine-rich Li-argyrodite sulfide solid electrolytes Li5.5PS4.5Cl1.5 are applied in all-solid-state batteries (ASSBs) due to the promising ionic transport and structural stability. However, the poor air/moisture stability and incompatibility to Li metal impede their practical applications. Herein, we synthesized a Li5.5PS4.5Cl1.5-based argyrodite exhibiting improved moisture stability and electrochemical performance to metallic Li, as well as high-voltage cathodes through O doping. The prepared oxygen-doped Li5.5PS4.5Cl1.5 samples (Li5.5PS4.425O0.075Cl1.5) possess significantly enhanced air stability and lower migration barrier in comparison with pristine Li5.5PS4.5Cl1.5. Moreover, Li5.5PS4.425O0.075Cl1.5 exhibits lower polarization voltage and better compatibility with lithium metal in the constant current charge-discharge tests of Li-Li symmetrical cell. This is attributed to the Cl-O coexistence coating interface that observed in the interface of Li/Li5.5PS4.425O0.075Cl1.5. To fully leverage the ultrafast ionic conductivity of Li5.5PS4.5Cl1.5, we construct ASSBs using optimized Li5.5PS4.425O0.075Cl1.5 as buffer layer between pristine LiNi0.6Mn0.2Co0.2O2 cathode materials and Li5.5PS4.5Cl1.5, leading to higher discharge capacities and elevated capacity retention. Based on above results, we further introduce LiNbO3-coated LiCoO2 as cathode, combined with Li5.5PS4.425O0.075Cl1.5 as an isolating layer between Li anode and Li5.5PS4.5Cl1.5 to suppress the growth of Li dendrite and achieve superior cyclability at wide voltage windows. Consequently, the all-solid-state lithium batteries exhibit promising application in a wide temperature range. This work provides a compelling strategy for achieving improved Chlorine-rich Li-argyrodite solid electrolytes with excellent air stability, high ionic conductivity and Li dendrite suppression capability, hence enabling all-solid-state batteries with high energy density and superior cyclability.