Engineered Interfaces in Hybrid Ceramic–Polymer Electrolytes for Use in All-Solid-State Li Batteries

Composites of inorganic lithium ion conducting glass ceramics (LICGCs) and organic polymers may provide the best combination of properties for safe solid separators in lithium or lithium ion batteries to replace the currently used volatile liquid electrolytes. A key problem for their use is the high interfacial resistance that develops between the two, increasing the total cell impedance. Here we show that the application of a thin conformal SiO<sub>2</sub> coating onto a LICGC followed by silanization with (CH<sub>3</sub>CH<sub>2</sub>O)<sub>3</sub>–Si–(OCH<sub>2</sub>CH<sub>2</sub>)–OCH<sub>3</sub> in the presence of LiTFSI results in good adhesion between the SiO<sub>2</sub> and the LICGC, a low resistance interface, and good wetting of Li<sup>0</sup>. Further, the cross-linked polymer formed on the surface of the silanated SiO<sub>2</sub> interface formed from excess (CH<sub>3</sub>CH<sub>2</sub>O)<sub>3</sub>–Si–(OCH<sub>2</sub>CH<sub>2</sub>)–OCH<sub>3</sub> prevents corrosion of the LICGC by Li<sup>0</sup> metal. The use of SiO<sub>2</sub> as a “glue” enables compatibilization of inorganic ceramics with other polymers and introduction of interfacial pendant anions.