The effect of different kinds of aprotic organic solvents on the discharge performance and discharge products in Li-O2 batteries was systematically investigated. The discharge products deposited in air cathodes were analyzed by X-ray diffraction, in situ gas chromatography/mass spectroscopy and X-ray photoelectron spectroscopy. We found that a significant amount of Li2O2 can be formed in glyme-based electrolytes during the discharge process, while only small amount of Li2O2 is produced in electrolytes of phosphate, nitrile, ionic liquid and sulfoxide. However, in all the seven types of solvent systems we studied, Li2CO3 and LiF were still formed as byproducts whose compositions are strongly related to the solvents. Li2CO3 is produced not from the carbon air electrode but from oxidation and decomposition of the solvent as we verified by using a 13C-labeled carbon electrode and the solid-state 13C-MAS NMR technique. The formation of Li2CO3 and LiF during discharge will greatly reduce the Coulombic efficiency and cycle life of the Li-air batteries. Therefore, better electrolytes that can ensure the formation of Li2O2 but minimize other reaction products formed on air electrodes of Li-air batteries need to be further investigated.
Revised: April 19, 2013 |
Published: May 18, 2012
Citation
Xu W., J.Z. Hu, M.H. Engelhard, S.A. Towne, J.S. Hardy, J. Xiao, and J. Feng, et al. 2012.The Stability of Organic Solvents and Carbon Electrode in Nonaqueous Li-O2 Batteries.Journal of Power Sources 215.PNNL-SA-85748.doi:10.1016/j.jpowsour.2012.05.021