Scientific Achievement
We studied the structure of block copolymer electrolyte using small-angle X-ray scattering (SAXS) during direct current (dc) polarization and observed the distortion of the lamellae domain spacing d to accommodate the salt concentration gradient.
Significance and Impact
The results shed light on the nature of ion transport in nanostructured block copolymers under dc polarization and indicate that the process of block copolymer rearrangement limits the maximum current (ilim) that can be sustained by a block copolymer electrolyte.
Research Details
- Polystyrene-blockpoly(ethylene oxide) (PS-b-PEO , or SEO) doped with bis-(trifluoromethylsulfonyl)amine lithium salt (LiTFSI) was studied.
- The measured ilim is approximately a factor of two lower than that predicted from concentrated solution theory.
- SAXS experiments show a net increase in the domain spacing of the block copolymer as the salt concentration gradient develops. LAM⊥ grains swell and contract to a greater extent compared to LAM||.
- The observed limiting current originates from the distortion of lamellae domains to accommodate the salt concentration gradient, which is not accounted for by concentrated solution theory.
