Polymer electrolytes are of utmost relevance for many applications of lithium ion batteries. Close to the electrodes they are exposed to high electric fields. Here we present extensive molecular dynamics simulations of a standard polymer electrolyte (poly(ethylene oxide) with a lithium salt) for different applied electric fields up to a few Volt per nanometer. We observe a prominent dependence of structural and dynamical properties on the electric field, reflecting nonlinear effects. It is shown that studying the field dependence allows one to characterize the motional mechanisms for the lithium transport in these electrolytes. Furthermore, several key questions can be answered: (1) Does the strong increase of the mobility upon increasing electric field result from the corresponding change of structural features? (2) Is it possible to identify the underlying reasons for structural field dependencies? Of particular interest is the response of the system after switching of or on the field. The results are compared with corresponding experiments on similar or different ion conductors. Finally, the additional contribution of an electrode interface in analysed.

Impact of electric fields on ion and polymer dynamics in polymer electrolytes

ACS Fall 2020 Virtual Meeting

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