Enhancing the Lithium Ion Conductivity of an All Solid-State Electrolyte via Dry and Solvent-Free Scalable Series Production Processes

Abstract

This work is about the possibility to enhance the lithium ion conductivity of a polymeric solid-state electrolyte via scalable production processes which can directly be utilized for series production. The solid electrolyte consists of PEO, LiTFSI and SiO2 and achieved a maximum ionic conductivity of σIon = 2.4 ·10−3 S cm−1 at 90 °C and σIon = 1.26 ·10−3 S cm−1 at 80 °C. For that, we present a scalable completely dry process chain consisting of granulation, plastification and calendering without the need of any solvents. Within these production processes the influence of process parameters like specific energy input, production temperature and filling degree to the properties of the polymeric solid electrolyte components (among others lithium ion conductivity, chain length, density) are investigated. One key finding is that a suitable process window in terms of specific energy input during plastification is very small and can be quantified for the given process geometry. Under- or overshooting these barriers can directly lead to a degradation of the whole system and as a result directly decreased lithium ion conductivities. Besides process parameters, we also investigate material and formulation parameters, like salt concentration, annealing time and measurement temperatures. Finally, a model is presented to describe the maximum achievable lithium ion conductivity as a function of the specific energy input during production.