Relationship between Phase Behavior and Ion Transport in Single-ion Conducting Polymer Blends Electrolyte

Poly(ethylene oxide) (PEO) has been widely studied as a candidate for solid-state electrolytes in next generation lithium metal batteries due to its ability to dissociate lithium salts and enable fast ion transport. However, PEO-based electrolytes possess low cation transference numbers, which results in the formation of steep lithium ion concentration gradients across the electrolyte and limits the maximum charging rate of the battery. Single-ion conducting polymers, wherein the anions are immobilized onto the polymer backbone, inhibit the formation of lithium ion concentration gradients, which greatly increases the cation transference number (t⁺). Nevertheless, these ion-containing polymers typically exhibit low ionic conductivity due to their high glass-transition temperatures. In this presentation, I will introduce a novel class of electrolytes, single-ion conducting polymer blend electrolytes (SIPBE), generated by blending two distinct classes of polymers together. I will present how SIPBEs form miscible blends and possess both high ionic conductivity and high t⁺ values. The phase diagram of new SIPBE systems will be determined through differential scanning calorimetry (DSC) to investigate the effect of polymer molecular weights and salt concentrations on phase behavior. In addition, the miscibility of SIPBE systems can be used to help interpret the ion transport properties measured with electrochemical impedance spectroscopy (EIS). The results will provide insight into thermodynamics and structure-conductivity relationship of the novel SIPBE system.