Mapping the Structure-conductivity Landscape of Polymer Electrolytes

Daniel Jacobson, California Institute of Technology

Photo of Daniel Jacobson

Lithium batteries have become ubiquitous, but their liquid electrolyte is flammable and this can have disastrous consequences. We would like to replace this with a less flammable polymer electrolyte, but current generation polymers are not conductive enough to fulfill this purpose. In order to design new highly conductive materials, we must first understand how ion transport occurs within a polymer and how this depends on the polymer chemistry. Computational studies can potentially provide us with exactly this type of information. However, polymers are plagued by extremely long relaxation times that make direct calculation of diffusion constants using molecular dynamics intractable. In the Miller Group, we have examined ion transport in polymers computationally over the last several years and discovered that ions move by hopping between solvation sites that display regular structure. This means that the connectivity of the network of potential solvation sites in the neat polymer plays a critical role in determining the ease of ion transport. We have been able to harness this mechanistic hopping-based picture to build a chemically specific coarse-grained model of ion transport process. This model allows us to obtain accurate lithium ion diffusivities using short molecular dynamics trajectories. As a result, we can now, for first time, map out the structure-conductivity landscape of a large, chemically diverse set of polymer electrolytes.

Abstract Author(s): Daniel Jacobson, Thomas F. Miller III