Developing various design strategies for poly (ethyleneoxide) (PEO) based dry polymer electrolytes (SPEs)

Poly (ethylene oxide) (PEO) based electrolytes promise high ionic conductivity because of high solubility of various lithium salts and fast ion mobility coupled with segmental dynamics of the polymer. Due to its simple monomer structure with no bulky side groups, PEO crystallizes at room temperature, therefore impedes ion transportation. Furthermore, its low glass transition temperature (-55oC) results in poor mechanical performance. Obtaining highly conductive solvent-free polymer electrolytes without much sacrificing mechanical stability near room temperature remains as a major challenge. In this work, we systematically investigate the role of polymer architecture on crystallization, segmental dynamics, and ionic conductivity in various PEO-based solid polymer electrolyte types, including homopolymers, polymer blends, and nanocomposites. While the homopolymer electrolytes allowed to understand the effect of branching and nanoscale dynamics on Li-ion transport at the fundamental level, the blends of PEO of non-linear architectures of PEO,such as stars, hyperbranched, and bottlebrush, with linear PMMA and their nanocomposites with silica (SiO2) nanoparticles enabled us to decouple segmental dynamics from ionic conductivity. Our results showed a remarkable suppression of crystallization of PEO in the nonlinear blends. Furthermore, the ionic conductivity of the electrolytes which depends on the salt concentration and polymer architecture could be improved with increased mechanical performance by simply modifying the PEO architecture from linear to branched structures. Overall, our study provides a promising and compelling experimental evidence that macromolecular architecture could be a powerful new tool for tuning the ionic conductivity PEO-based electrolytes, opening a new research avenue in the field of polymer electrolytes for lithium-ion batteries.