Dry-film technology employing cryo-pulverized polytetrafluoroethylene binder for all-solid-state batteries

Sulfide-based all-solid-state batteries (ASSBs) are promising candidates for next-generation lithium-ion batteries (LIBs) owing to their improved safety and high energy density. However, when the wet process commonly employed in LIBs is applied to sulfide-based ASSBs, it can result in several issues, including side reactions of solid electrolytes and non-uniform distribution of binders/carbon in the cathode after solvent drying. To address such issues, we employ a dry-processed electrode technology utilizing a polytetrafluoroethylene (PTFE) binder in this study. The effect of PTFE particle size is explored using cryogenic pulverization to reduce PTFE resistance and evenly distribute it. Tuning the PTFE particle size to a few micrometers serves to enhance both ionic and electronic conduction by reducing the contribution of insulating components within the composite cathode. Furthermore, the even distribution of the binder enables the maintenance of tight contact between the components of the composite cathode even after cycling. Consequently, the ASSBs incorporating cryo-pulverized PTFE exhibit improved capacity (188 mAh/g at 0.2 C) and cycle performance (90.4 % capacity retention after 100 cycles) with current density of 3.0 mA cm−2. These findings represent a significant advancement in the development of the dry-film process for ASSBs.