Achieving superior moisture-resistant and electrochemical properties of chlorine-rich Li-argyrodites via high oxygen dose

Cl-rich Li-argyrodites are promising solid electrolytes (SEs) used in all-solid-state Li batteries (ASSLBs) owing to the fast ion transport. However, they are unstable in the air and their compatibility to metallic Li still needs to be strengthened. Here, we improve these properties through O doping with a relatively high concentration. The high O solid solution in the argyrodite lattice is verified. The optimized Li5.7PS4.5O0.2Cl1.3 SE possesses an enhanced room temperature ionic conductivity. In parallel, in the sample with a relatively high oxygen dose, a Cl-O coexistence interface layer is revealed at the Li|SE interface region, associated with the formation of LiCl and Li3OCl interphases. The highest amount of Li3OCl appears also in the interface of Li5.7PS4.5O0.2Cl1.3 SE. Along with a more stable PS4-xOx unit, a proper O doing concentration is beneficial to mitigate the decomposition rate of SEs and to improve the compatibility of SE against Li metal. Moreover, Li5.7PS4.5O0.2Cl1.3 gains significantly enhanced air stability in contrast to the O-free sample. Consequently, the ASSLBs using both pristine and air-exposed Li5.7PS4.5O0.2Cl1.3 SE demonstrate decent electrochemical performance. In sharp contrast, the ASSLBs using the O-free argyrodite SE after air exposure cannot work for even one cycle. A high amount of O incorporation in Cl-rich Li-argyrodite SEs is thus a facile and effective route for achieving good overall performance including a high ionic conductivity, Li|SE interface stability, Li dendrite suppression capability, and notably, air stability.