Structure and dynamics in poly(ethylene oxide)-blended single-ion conducting polymer electrolytes based on side-chain ionomers

Abstract

While single-ion conducting polymer electrolytes (SICPEs) are highly promising candidates for safer polymer electrolytes due to their stability and high transference number, their practical application is often hindered by substantially lower ionic conductivities. In this study, we investigate morphology and dynamics of a family of SICPEs based on a side-chain ionomer blended with poly(ethylene oxide) (PEO) at various ratios. In the pure state, the side-chain ionomer is liquid crystalline with dense ionic layers. PEO addition reduced the primary glass transition temperature, accompanied by the emergence of a new glass transition attributed to the ionomer's polystyrene backbone. Morphologically, blends with lower PEO content maintained the lamellar structure of the pure ionomer, while higher PEO ratios resulted in increased disorder. The ionic conductivity of the blend at high PEO content (EO–Li ratio of 20–1) reached 7.9 × 10⁻⁵ S cm⁻¹ at 90 °C, approximately four orders of magnitude greater than that of pure ionomer and similar to that of other PEO-ionomer blends containing tethered –sulfonyl(trifluoromethylsulfonyl)imide (–TFSI⁻) anions. Dielectric spectroscopy revealed that PEO addition leads to increased coupling between dielectric relaxation and long-range ion transport.