Properties of the Interphase formed between Argyrodite-type Li6PS5Cl and Polymer-based PEO10:LiTFSI

All-solid-state lithium metal batteries using thiophosphate solid electrolytes (SE) present a promising alternative to state-of-the-art lithium ion batteries due to their potentially superior energy and power. However, reactions occurring at the lithium metal | SE interface result in an increasing resistance and limited cycle life. A stable solid polymer electrolyte (SPE) may be used as protective interlayer to prevent the SE from direct contact and reaction with lithium metal. This creates a new and rarely studied hetero-ionic interface between the inorganic SE and the SPE, which we investigate here. The interface resistance between argyrodite-type Li6PS5Cl and a polyethylene oxide/LiTFSI based SPE is quantified by four-point electrochemical impedance measurements using two wire-shaped reference electrodes (2.4 Ω cm2 at 80 °C). The activation energy for lithium ion transport through the solid polymer electrolyte interface (SPEI) is 0.67 eV. Two distinct interface processes are observed and attributed to ...