Ion Transport in Polymer Electrolytes: Effect of Glass Transition Temperature

Polymer Electrolytes (PEs) are promising alternative materials to conventional organic electrolyte systems since they are nonflammable and suppress lithium dendrite growth. However, PEs possess much lower ionic conductivity undermining their ability to be used in lithium-ion batteries. It has been suggested that polymer segmental relaxation is one of the main mechanisms of Li⁺ transport. Given a polymer chemistry, this mechanism is correlated to the glass transition temperature (T_g). However, a systematic understanding of the dependence of T_g on system properties is still lacking. To this end, we conduct coarse-grained molecular dynamics simulations of salt-doped polymers. In our work, we focus on the combined effects of temperature and salt concentration on ionic conductivity and how glass transition affects ion transport, within the same polymer. Our results hint towards a temperature-salt concentration superposition of the ionic conductivity. We will present possible implications of this finding and its relation to the glass transition temperature.