Peptide-Based Block Copolymer Electrolytes as Sustainable Material Platforms for Tunable Ion Transport and Mechanical...

Nanostructured poly(ethylene oxide) (PEO)-based block copolymer electrolytes enable mechanical-ionic decoupling but typically rely on rigid, oil-derived polymers such as polystyrene (PS) for mechanical reinforcement and exhibit limited room-temperature ionic conductivity. Here, we report peptide-based block copolymer electrolytes composed of poly(l-histidine)-block-poly(ethylene oxide) (PHis-b-PEO) as a sustainable alternative to conventional PS-b-PEO systems. PHis-b-PEO/LiTFSI electrolytes display thermally activated PEO-mediated ion transport while maintaining a predominantly solid-like mechanical response with storage moduli in the MPa range over a wide temperature window, demonstrating effective mechanical-ionic decoupling. To overcome the limited room-temperature conductivity, a proof-of-principle plasticization of ion-conducting phase strategy is introduced by incorporating low-molecular-weight PEO into the block copolymer matrix. Structural analysis confirms preferential swelling of the PEO-rich conducting domains without disruption of the PHis-rich reinforcing framework, leading to over an order-of-magnitude enhancement in ionic conductivity and a transition toward diffusion-dominated ion transport while preserving solid-state mechanical integrity. These results establish peptide-based block copolymers as a versatile, bioderived platform for designing mechanically robust solid polymer electrolytes.