Utilizing Molecular Architecture to Develop High-Efficiency Single-Ion Polymer Electrolytes for Energy Storage.

Creating single-ion solid polymer electrolytes (SI-SPEs) with high ionic conductivity is essential for developing safe, long-lasting, and high-energy batteries. Despite significant advancements in SI-SPE research, a major challenge persists: achieving materials with a cation transference number near unity and robust mechanical properties without diminishing ionic conductivity. In this work, we present a novel approach using nanostructured polyanionic particles as additives to low-molecular-weight, liquid PEO to synthesize nanostructured SI-SPEs that effectively decouple the typically conflicting properties of ion conductivity and mechanical strength. This specific macromolecular design allows for a well-dispersed polyanionic particle structure at various concentrations, enabling the formation of a nanostructured single-ion electrolyte with interconnected liquid PEO channels that enhance ion conductivity through cation diffusion. Remarkably, while the ion conductivity remains nearly constant at around 10⁻⁵ S/cm for wt% ≤ 55, the shear modulus, G', increases by more than five orders of magnitude as wt% rises. These results highlight how the proposed macromolecular design strategy provides a new pathway for designing SI-SPEs, supporting the development of high-energy, safe lithium metal batteries.