Finding non-aqueous proton conductors for polymer-based electrolytes using density functional theory*

Polymer electrolytes, used in energy storage and conversion devices like fuel cells and lithium-ion batteries, offer benefits such as high electrochemical stability, mechanical flexibility, and interface stability, positioning them above their liquid and ceramic counterparts. However, their reliance on water restricts their working temperature below the boiling point of water, thus limiting polymer electrolyte membrane fuel cell performance. This study employs density functional theory to investigate amphoteric molecules, capable of both accepting and donating protons, as potential non-aqueous proton conductors. Using the proton affinity energy as a proxy for the proton transfer barrier, we examine how changes in electron donating and withdrawing groups can enhance or reduce the hopping of protons between molecules. Extending previous work by Zawodzinski et al., our simulations help to elucidate how these modifications can be used to identify novel molecules with proton affinities mirroring water. Consequently, this research provides the basis for the use of data science methods that can expedite the design and discovery of high-temperature, water-free electrolytes.