A copolyether with pendant cyclic carbonate segment for PEO-based solid polymer electrolyte

The application of PEO-based solid polymer electrolyte (SPE) is limited by the low ionic conductivity and lithium-ion transference number near room temperature. In this paper, a pendant polyether poly (EO-co-PCGE) (PECP) with low molecular weight is prepared by copolymerization of ethylene oxide (EO) monomer with typical lithium-ion conduction group and propylene carbonate glycidyl ether (PCGE) monomer with high dielectric group. By blended with PECP, the PEO-based SPE is obtained and its ionic conductivity can be increased to 3.54 × 10−5 S cm−1 at room temperature and 1.32 × 10−4 S cm−1 at 40 °C. In one aspect, the pendant structure and low molecular weight are beneficial to the reduction of the crystallinity of PEO matrix; in a further aspect, the cyclic carbonate pendant offers a competitive effect on segmental motion and the lithium-ion complexation of PEO, thus affecting the conduction mechanism of lithium-ions in the conventional PEO-based SPE and significantly increasing the lithium-ion transference number. The synergistic effect of these two aspects makes the prepared PEO-based SPE have excellent properties of ionic conduction especially at room temperature, and the LiFePO4/Li batteries with the SPE present excellent cycling performance at the temperature of 40 °C with a discharge capacity of about 100 mA h g−1 after 150 battery cycles.