Enhanced ion transport by tuning intra-domain structure and dynamics in nanostructured block polymer electrolytes

Nanostructured block polymer (BP) electrolytes with modified ion/monomer segment distributions have demonstrated the potential to boost the performance and safety in lithium-ion batteries by enabling intra-domain structures that are challenging to realize in conventional BPs. We synthesize BPs with gradient monomer segment composition profiles between the homogeneous blocks (i.e., tapered BPs) to tune the abovementioned distributions. Through a combination of reflectometry experiments and coarse-grained molecular dynamics simulations that include strong ion solvation effects, we identify that the addition of a tapered region increases transport by reducing chain stretching and conducting segment/ion content near the confining interface. To further elucidate the connection between intra-domain structure and local mobility, we create a quantitative framework and validate it through nuclear magnetic resonance spectroscopy studies on solid electrolyte samples. In addition to segmental mixing, chain stretching, and confinement effects, the dynamical heterogeneity within a monomer segment (e.g., along a side chain) also influences local mobility significantly. This link between local and global dynamics can facilitate the design of next-generation electrolytes.