Due to battery fire accidents while driving and charging an electric vehicle, research on improving battery safety as well as increasing the energy density has been extensively performed. For this purpose, an all-solid-state battery without the flammable liquid electrolyte is being more actively conducted. Among various solid electrolyte types, the sulfide-based solid electrolyte has been investigated as the most promising candidate owing to its high ionic conductivity and ductility. However, since sulfide solid electrolyte is too reactive to organic solvents like N-methyl pyrrolidone, a few nonpolar solvents (xylene or toluene) can be used to fabricate sulfide solid electrolyte. Thus, except for rubber binders such as nitrile butadiene rubber, other conventional adhesive binders are excluded from candidates. So, to solve this limitation fundamentally, a dry process without any solvents must be an attractive method for using the sulfide electrolyte in battery manufacturing process. For example, polytetrafluoroethylene (PTFE) is frequently used for fabricating all-solid-state electrode (ASSE) with sulfide electrolytes due to its wonderful fibrilization property. However, comparing to the wet process, it is more challenging to distribute all the electrode components uniformly in the dry process, where all the components are mixed through kneading the electrode dough. That is, to maximize the electrochemical performances of ASSEs, it is essential to evaluate the mechanical properties of ASSEs fabricated from dry process and to quantify them for optimization. However, most of research on ASSEs have been focused on their electrochemical performances up to now.
Thus, in this work, we attempted to measure the mechanical properties of ASSEs with sulfide electrolyte using a surface and interfacial cutting analysis system (SAICAS). The ASSEs were fabricated through dry process while changing the PTFE binder content. Subsequently, both bulk and interfacial adhesive strengths were analyzed systematically and deliberately by a few μm resolution. Furthermore, to unveil the surface, bulk, and interfacial electrical properties are also measured using an electrode resistance measuring instrument (HIOKI RM2610). Thus, we can provide a correlation between binder content and mechanical/electrical properties of dry ASSEs. Finally, comparative results based on wet processed ASSEs will also be included in this work.
