Lithium salt-induced microphase separation in photopolymerized solid polymer electrolytes

This paper reports on lithium salt-induced microphase separation of linear and star block copolymers (BCPs) dispersed in monomer to produce solid polymer electrolytes (SPEs). The proposed one-step photopolymerization methodology uses pre-synthesized BCPs of Poly (styrene-co-benzyl methacrylate)-b-Poly [oligo(ethylene glycol) methyl ether acrylate] (P(S-co-BzMA)-b-POEGA) solubilized with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in oligo (ethylene glycol) methyl ether acrylate (OEGA). The resulting kinetically arrested glassy nano-domains of P(S-co-BzMA) are later fixed during the POEGA homopolymer matrix photopolymerization. A variety of morphologies can be produced by adjusting lithium salt content and BCP architectures, i.e., linear or star-like. Embedding the BCP nanostructures in the POEGA matrix acted as physical crosslinking that enhances the mechanical strength by a factor of seven, compared to un-crosslinked POEGA, without sacrificing on ionic conductivity. Remarkably, these innovative materials not only match the mechanical properties and conductivity of traditional cross-linked POEGA-based SPEs, but also open a valuable way towards recyclability.