The study of electrolyte solutions based on solvents from the “glyme” family (linear polyethers) for secondary Li battery systems

The behaviour of Li electrodes was studied in solutions of dimethoxy ethane (DME), ethyl glyme (EG, CH3CH2OCH2CH2OCH2CH3) and diglyme (DG, CH3OCH2CH2OCH2CH2OCH3). Salts from the LiAsF6, LiClO4, LiSO3CF3, LiN(SO2CF3)2, LiBF4, LiBr and LiI list were used as electrolytes and 1–3 Dioxolane (DN), propylene, ethylene and dimethyl carbonates were used as co-solvents. The correlation amongst the surface chemistry, morphology and cycling efficiency of Li electrodes in these solutions was studied using surface sensitive FTIR spectroscopy, electron microscopy (SEM) and chronopotentiometry. Basically, solutions of the above salts in the three glyme solvents tested, as well as those tested in solvent mixtures containing DN or alkyl carbonates with any one of the glyme solvents, do not seem suitable for use in rechargeable Li battery systems having Li metal anodes because the rough morphology of Li upon deposition-dissolution cycling in them leads to low Li cycling efficiency. The key factor in this respect seems to be the surface chemistry developed on Li in these solvents. This point is discussed thoroughly in this paper.