Solid polymer electrolytes (SPEs) have the potential to unite all the key advantageous properties of liquid electrolytes (high ion conductivity, wettability, and easy fabrication) with those of solid inorganic electrolytes such as ceramics and glasses (inflammability, compatibility with metal anodes and high voltage cathodes, and prevention of dendrite formation). SPEs with low temperature ion conductivities of more than 10 mS/cm require glass transition temperatures (Tg) around room temperature or below and high content of charge carrier salts. With atomistic simulations we extensively investigated and analyzed how the polymer formulation and the charge carrier salt concentration affect Tg, the ion conductivity, the electrochemical stability, and also the mechanical stability of SPEs. All calculations are performed with the software environment MedeA® [1,2] which integrates the best simulation approaches with comprehensive databases, efficient computing and analysis tools, and utilities to convert results from simulations into innovative material formulations. REFERENCES [1] M. Christensen, M. et al. Software Platforms for Electronic/Atomistic/Mesoscopic Modeling: Status and Perspectives. Integrating Materials and Manufacturing Innovation (2017), doi:10.1007/s40192-017-0087-2. [2] MedeA®, Materials Design, Inc., San Diego, CA, USA, 2019, http://www.materialsdesign.com