Single-ion conducting polymer electrolytes: Molecular design strategies for high cation transference and ionic conductivity

Single-ion conducting polymer electrolytes (SICPEs) have emerged as promising solid-state electrolytes for next-generation rechargeable batteries, offering high ion transference number and improved safety compared to conventional dual-ion systems. However, achieving simultaneous high ionic transfer number and ion conductivity remains a critical challenge due to the inherent trade-off between anion immobilization and polymer chain mobility. This review provides a comprehensive analysis of molecular and structural design strategies aimed at decoupling Li + transport from bulk polymer segmental motion. Key approaches include backbone engineering, crosslinked network architectures, block copolymer self-assembly, star-shaped oligomers, hydrogen-bonding networks, polymer blends with locally high-concentration domains, and targeted grafting of ion-conducting segments. The mechanisms by which these designs enhance Li + dissociation, migration pathways, and interfacial stability are critically examined, supported by quantitative performance metrics from recent literature. Finally, emerging trends such as multifunctional polymer frameworks, synergistic plasticization–reinforcement strategies, and interface-oriented molecular design are discussed, outlining a roadmap toward SICPEs with room temperature conductivities exceeding 10 − 3 S cm − 1 and sufficient modulus for effective dendrite suppression.