The kinetics and thermodynamics of oxygen reduction reactions (ORR) in aprotic Li electrolyte were shown to be highly dependent on the surrounding chemical environment and electrochemical conditions. Numerous reports have demonstrated the importance of high donor number (DN) solvents for enhanced ORR, and attributed this phenomenon to the stabilizing interactions between the reduced oxygen species and the solvent molecules. We focus herein on the often overlooked effect of the Li salt used in the electrolyte solution. We show that the level of dissociation of the salt used plays a significant role in the ORR, even as important as the effect of the solvent DN. We clearly show that the salt used dictates the kinetics and thermodynamic of the ORR, and also enables control of the reduced Li2O2 morphology. By optimizing the salt composition, we have managed to demonstrate a superior ORR behavior in diglyme solutions, even when compared to the high DN DMSO solutions. Our work paves the way for optimization of various solvents with reasonable anodic and cathodic stabilities, which have so far been overlooked due to their relatively low DN.
Bibliographical noteFunding Information:
A.A.F. thanks the Israel Science Foundation (ISF, Grant 1469/13) as well as the Ethel and David Resnick Chair in Active Oxygen Chemistry for their kind and generous support. Partial support for this study was also obtained by the INREP project of the ISF. D.S. thanks the Israel Ministry of Science Technology and Space. M.N. was funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award DESC0001160
© 2016 American Chemical Society.
- Li-O batteries
- glyme solvents
- ionic association
- lithium salts