Physio-Electrochemically Durable Dry-Processed Solid-State Electrolyte Films for All-Solid-State Batteries

The dry process is a promising fabrication method for all-solid-state batteries (ASSBs) to eliminate energy-intense drying and solvent recovery steps and to prevent degradation of solid-state electrolytes (SSEs) in the wet process. While previous studies have utilized the dry process to enable thin SSE films, systematic studies on their fabrication, physical and electrochemical properties, and electrochemical performance are unprecedented. Here, different fabrication parameters are studied to understand polytetrafluoroethylene (PTFE) binder fibrillation and its impact on the physio-electrochemical properties of SSE films, as well as the cycling stability of ASSBs resulting from such SSEs. A counter-balancing relation between the physio-electrochemical properties and cycling stability is observed, which is due to the propagating behavior of PTFE reduction (both chemically and electrochemically) through the fibrillation network, resulting in cell failure from current leakage and ion blockage. By controlling PTFE fibrillation, a bilayer configuration of SSE film to enable physio-electrochemically durable SSE film for both good cycling stability and charge storage capability of ASSBs is demonstrated.