Ionic conductivity is widely used to evaluate polymer electrolyte performance. In light of the complex ion speciation that occurs in low dielectric constant polymers such as PEO, this may not be a good metric. The PI's preliminary work on salt diffusion indicates an exponential dependence on salt concentration hypothesized to be directly correlated to ion speciation and connectivity of ion transport pathways. The thorough evaluation of transport in polymer electrolytes for lithium batteries could shift the paradigm in understanding what limits the discharge rate in these batteries. For example, salt diffusion and transference number may be more relevant metrics for polymer electrolyte performance than conductivity. Knowledge will be gained of the physical underpinnings of transport using a combination of frontier techniques and novel materials. The research will examine polymer electrolytes with high salt concentrations, a region of promise that has received little attention. The accuracy of battery simulations relies on accurate transport parameters that will be determined without relying on several simplifying assumptions that were recently brought into question. A validated polymer electrolyte battery model will be developed and made publicly available. It will assist the battery community in determining target transport properties for the next generation of polymer electrolytes.