The need for creating safe electrolytes for lithium batteries is significant given the continued safety problems associated with current lithium-ion batteries. Nonflammable polymer electrolytes offer a possible solution but the rate of lithium ion transport is too low for practical applications. In this talk, I will discuss some of the fundamental factors that limit ion transport in polymers. In all electrolytes, the current generated at steady state is governed by the applied potential. This relationship, which one might call a modified Ohm’s Law, depends on Stefan-Maxwell diffusion coefficients. We find that these diffusion coefficients are negative over a substantial salt concentration range in polymer electrolytes. I will use these diffusion coefficients to analyze and predict battery performance. A crucial ingredient in the analysis is a “condition” that my PhD student Danielle Pesko arrived at.