Studies of Li ion conduction mechanism for zwitterionic polymer electrolytes using molecular dynamics simulations*

Polymer electrolytes are attracting attention due to their ability to improve the safety and durability of commercial Li ion batteries traditionally consisting of liquid electrolytes; however, they exhibit a lower Li ion conductivity. Recent studies suggested that a class of polyzwitterions with LiTFSI as the added lithium salt improves low temperature conductivity and Li transference numbers compared with generally known polymer electrolytes such as PEO, but the mechanism of the fast Li transport in polyzwitterion systems is not yet understood. To clarify the mechanism, we built model systems of polyzwitterions that capture the important features of experimentally reported polyzwitterions and analyzed the Li ion motion using all-atom molecular dynamics simulations. We discuss the dynamic properties, detailed structural features, and the interactions between Li ions and polyzwitterions/TFSI anions at the atomic level.