Orientation-Dependent Distortion of Lamellae in a Block Copolymer Electrolyte under DC Polarization

Lithium-salt-doped block copolymers have the potential to serve as solid electrolytes in rechargeable batteries with lithium metal anodes. In this work, we use small-angle X-ray scattering (SAXS) study structure of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) doped bis-(trifluoromethylsulfonyl)amine salt (LiTFSI) during direct current (dc) polarization experiments lithium–lithium symmetric cells. The copolymer studied is nearly composition, has a total molecular weight 39 kg mol–1, and exhibits lamellar morphology at all concentrations. When ionic passed through electrolyte, concentration gradient forms that induces spatial domain spacing, d. dependence d on distance from positive electrode, x, was determined experimentally by scanning incident beam one electrode other. By studying two-dimensional (2D) SAXS patterns function azimuthal angle, find lamellae PS/PEO interfaces oriented perpendicular flow (LAM?) swell contract greater degree than those parallel direction (LAM||). While domains LAM? do not provide conducting pathways between electrodes, our analysis suggests they play an important role establishing necessary for sustaining large expansion contraction.