Promote the conductivity of solid polymer electrolyte at room temperature by constructing a dual range ionic conduction path

Abstract

Poly(ethylene oxide) (PEO) is a classic matrix model for solid polymer electrolyte which can not only dissociate lithium-ions (Li+), but also can conduct Li+ through segmental motion in long-range. However, the crystal aggregation state of PEO restricts the conduction of Li+ especially at room temperature. In this work, an amorphous polymer electrolyte with ethylene oxide (EO) and propylene oxide (PO) block structure (B-PEG@DMC) synthesized by the transesterification is firstly obtained, showing an ionic conductivity value of 1.1 × 10−5 S/cm at room temperature (25 °C). According to the molecular dynamics (MD) simulation, the PO segments would lead to an inconsecutive and hampered conduction of Li+, which is not beneficial to the short range conduction of Li+. Thus the effect of transformation of aggregation state on the improvement of ionic conductivity is not enough, it is necessary to further consider the different coupled behaviours of EO and PO segments with Li+. In this way, we blend this amorphous polymer (B-PEG@DMC) with PEO to obtain a dual range ionic conductive solid polymer electrolyte (D-SPE) with further improved ionic conductivity promoted by constructing a dual range fast ionic conduction, which eventually shows a further improved ionic conductivity value of 2.3 × 10−5 S/cm at room temperature.