Diffusivity and Solubility of Oxygen in Solvents for Metal/Oxygen Batteries: A Combined Theoretical and Experimental Study

Abstract

The solubility and the diffusion constant of oxygen in the electrolyte are crucial parameters in the kinetics of metal/oxygen batteries since they govern the discharge current that can be achieved. However, both parameters are often unknown or scatter widely in literature. Evaluating these parameters in typical solvents and electrolytes is therefore essential toward better quantitative understanding and improvement of metal/oxygen batteries. Using oxygen uptake experiments and molecular dynamics simulations, we compare theoretical and experimental approaches to determine oxygen diffusion coefficients in several molecular solvents that are commonly used. We report diffusion coefficients and Henry's law constants of oxygen for a series of glymes with different chain length and perfluorinated solvents, and discuss the benefit of using both experiment and simulation to determine these parameters. In all nine investigated solvents, the difference between simulated and measured diffusion coefficients is small in comparison to the magnitude of the coefficients. The methodology and the reported values for oxygen solubility and diffusivity form a solid starting point for further investigations into more complex electrolyte solutions. Ultimately, they might help to propel research on metal/oxygen batteries even further.