Quantifying Lithium Salt and Polymer Density Distributions in Nanostructured Ion-Conducting Block Polymers

Abstract

Block polymer (BP) electrolytes offer significant advantages relative to existing liquid or polymer electrolytes due to their independently tunable ion transport and mechanical stability properties as a result of nanoscale self-assembly. Many of these nanostructured electrolytes are composed of a BP that is doped with a lithium salt to impart conductivity but which also alters the self-assembly (structure and thermodynamics) in comparison to the neat BP. By elucidating the effects of lithium salt concentration and counterion chemistry on the relevant salt and polymer density distributions, BP electrolytes with more efficient conductivity pathways can be developed. In this work, neutron and X-ray reflectometry (NR and XRR, respectively) were harnessed to determine the spatial distribution of salt and polymer in lamellae-forming polystyrene-block-poly(oligo-oxyethylene methacrylate) [PS-b-POEM] films doped with various lithium salts. From the NR results, the distribution of lithium salts across domains appe...