The high energy density of lithium-air batteries have made them potential energy storage systems for overcoming existing obstacles in large scale applications such as electric vehicles. However, the electrochemical stability and physicochemical properties of the electrolyte significantly alters the performance of these batteries. Ionic liquids, which have relatively wide electrochemical stability window and very low vapor pressure, can play a crucial role as electrolytes for enhancing the cyclic performance and safety of lithium-air batteries. The electron transfer rate constant of the electrochemical reactions at the surface of the electrodes influences the local current density and therefore ultimately affects the performance of lithium-air batteries. In this work, a novel method, based on Marcus’s theory is employed to conduct a fundamental study to determine the effect of dielectric constant of the ionic liquid electrolyte on the kinetics and energetics of the electron transfer reaction at the anode-electrolyte interface. Density functional theory (DFT) was used to calculate the necessary free energies for all the species involved in the oxidation of pure lithium metal into positively charged lithium ions at the anode. Our results indicate that the magnitude of the thermodynamic driving force for the anodic reaction increases with increase in the static dielectric constant of the electrolyte. Moreover, it is observed that the electron transfer rate constant for the anodic reaction is directly related to the static dielectric constant of the ionic liquid. The presented results provide important insight into kinetics and thermodynamics of electron transfer reactions in lithium-air batteries that will help in the identification of appropriate electrolytes for enhanced performance of lithium-air batteries.

Modeling the electron transfer reaction at the lithium metal anode-liquid electrolyte interface in lithium-air batteries

249th National Meeting (2015)

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