Continuous Mixing of Solid Polymer Electrolyte via Solvent-Free Extrusion with Automated Material Addition

The next-generation technology that promises to reduce safety concerns and improve the battery performance of currently used Lithium-ion batteries (LiB) is the so-called all-solid-state batteries (ASSBs). The future energy demands are forcing research and industry to move from laboratory-scale production of ASSB components to larger industrial-scale production. Thus, this study investigates the hot melt extrusion process of poly(ethylene oxide):Lithium bis (trifluoromethylsulfonyl)imide (PEO:LiTFSI) solid-state electrolytes at a ratio of 20:1 (EO:Li) using automated material addition. For extrusion, a co-rotating, intermeshing twin-screw extruder with two feeders that works under inert conditions is used. We investigate the influence of process parameters and screw design on the product quality. Therefore, we used different screw designs consisting of conveying, kneading, and mixing elements for the extrusion. This study elucidates that screw designs with kneading elements give the best results in terms of mixing and dissolving Li salt within the polymer matrix. These findings are supported by microscopy, by the determination of Tm using DMA showing the lowest Tm of 43°C, and by the calculated ionic conductivity of (8.4 ± 0.2) × 10-4 S cm-1 at 80°C using electrochemical impedance spectroscopy.