Solid polymer electrolytes (SPEs) are a classification of polymer electrolytes that consist of solvent-free material. One type of SPE is single-ion conducting polymer electrolytes (SIPEs), which contain cations covalently bonded to the polymer backbone to prevent electrode polarization. Due to the restricted cation mobility caused by the slow relaxation of the polymer as well as insufficient free charge carriers, SIPEs have poor ion conductivity. To remedy this, SIPEs can be swollen with polar organic solvents to allow for partial solvation and diffusion of cations along the solvent-polymer interface. Prior research has shown that multiblock copolymers composed of nonpolar alkyl blocks of fixed length strictly alternating with polar blocks containing a single lithium ion and sulfonate group exhibit distinct properties depending on their nanoscale morphology. The polar sulfonate groups in these polymers self-assemble to form periodic morphologies that facilitate ion transport.

          In this study, we investigate random copolymers with aperiodic morphologies, where ionic aggregates either adopt spherical or percolated forms. We utilize propylene carbonate (PC) for its high boiling point and its selective swelling of lithium-sulfonate moieties. This swelling enhances cation transport by allowing the cations to be more favorably associated with the relatively mobile PC molecules than with the sulfonate backbone.6 The polymer in this study is 13%-sulfonated polystyrene with a lithium counterion (SPS13Li). By varying the degree of sulfonation and other parameters, we aim to investigate the influence of aggregate morphology on ion transport in solvent-swollen SIPEs.