  Block-copolymer electrolytes with lamellar microstructure show promising
results regarding the ion transport in experiments. Motivated by these
observations we study block-copolymers consisting of a polystyrene (PS) block
and a poly(ethylene oxide) (PEO) block which were assembled in a lamellar
structure. The lamella was doped with various amounts of
lithium-bis(trifluoromethane)sulfonimide (LiTFSI) until very high loadings with
ratios of EO monomers to cations up to 1:1 were reached. We present insights
into the structure and ion transport from extensive Molecular Dynamics
simulations. For high salt concentrations most cations are not coordinated by
PEO but rather by TFSI and THF. More specifically, LiTFSI partially separates
from the PEO domain and forms a network-like structure in the middle of the
lamella. This central salt-rich layer plays a decisive role to enable
remarkably good cationic mobilities as well as high transport numbers in
agreement with the experimental results.
