Enhancement of lithium argyrodite interface stability through MoO2 substitution and its application in lithium solid state batteries

Abstract

A recently developed sulfide solid electrolyte in lithium solid-state batteries has a low critical current density, which can cause battery failure. Therefore, the metal oxide substitution in the Li-argyrodite structure was considered as a strategy to enhance the interface stability. In this work, the interface stability of the Li-argyrodites was improved using metal and oxygen substitution in the P- and S-sites of the Li6PS5Cl structure; furthermore, their structural and electrochemical performances were evaluated. For this study, the MoO2 substituted argyrodite (0 ≤ x ≤ 0.2) was synthesized using a high-energy ball-milling process. Structural analysis revealed that impurity phases occurred when x was over 0.05; this indicated the so lubility limit of the metal oxide substitution. The ionic conductivity analysis demonstrated that Li6PS5Cl MoO2-0.05 electrolyte maintained an ionic conductivity of 4.16 mS cm−1. Additionally, the Li6PS5Cl-MoO2-0.05 composition exhibited a higher critical current density (0.55 mA cm−2) than that of Li6PS5Cl (0.20 mA cm−2). It should be further noted that the electrochemical performances were examined against lithium as a reference.