Designing efficient polymer electrolytes via end-group controls

There has been an increasing demand for the development of high-conductivity solid-state polymer electrolytes (SPEs) to be used in lithium batteries by replacing liquid electrolytes. The most widely studied SPEs are based on poly(ethylene oxide) (PEO) and its derivatives owing to PEO’s high solvating capability for lithium salt and low glass transition temperature. Given that lithium ion conduction occurs through the segmental motion of PEO chains, high mobility of lithium ion was feasible in amorphous phases. This prompted extensive research efforts to suppress PEO crystallinity by various physical and chemical approaches. In the present study, we investigate PEO-based polymers incorporated with various terminal functional groups as an effective means of controlling crystallinity of PEO phases. Further, by attaching various di-functional groups to the end of PEO chains, it has been revealed that morphology, ionic conductivity, and lithium transference number of PEO electrolytes are fine-tunable, attributed to the alteration of inter- and intramolecular interactions within.