Online Real-Time Detection of the Degradation Products of Lithium Oxygen Batteries

Since the decomposition of electrolyte is one of the most important issues in the development of lithium–air batteries (LABs), which are considered to be promising energy storage devices for the future sustainable society, we examined the molecules produced during discharge/charge of a tetraethylene glycol dimethyl ether (TEGDME)-based LAB, or a lithium oxygen battery (LOB), as we used pure oxygen as an active material, in real time by using a newly developed online cold-trap pre-concentrator–gas chromatography/mass spectroscopy system. A total of 37 peaks were detected, and 27 of them were assigned to specific molecules. Several molecules were present as impurities in TEGDME, and a few molecules were generated during discharge, but most of the molecules were generated during charge. Some of the molecules generated at the end of charge were also generated without discharge, indicating that these molecules were formed by direct electrochemical oxidation without involvement of active oxygen.