STUDIES OF LI ANODES IN THE ELECTROLYTE SYSTEM 2ME-THF THF/ME-FURAN/LIASF6/

The correlation between Li cycling efficiency, Li morphology, Li surfa ce chemistry, and the properties of the Li-solution interphase was inv estigated in the THF, 2Me-THF, 2Me-Furan (MF), LiAsF6, electrolyte sys tem. Surface sensitive FTIR, EDAX-x-ray microanalysis, SEM, and impeda nce spectroscopy were used in conjunction with standard electrochemica l techniques. Using THF as a cosolvent to 2Me-THF decreases the detrim ental impact of contaminants such as water as it is more reactive towa rd lithium than 2Me-THF. The presence of MF (a few percent)influences the Li surface chemistry since its reduction to surface compounds with alkoxy groups suppresses solvent and salt reduction. However, its eff ect on Li morphology and cycling efficiency is marginal. It is conclud ed that the main positive impact of this additive reported in the lite rature is due to the stabilizing effect of the ethers by its possible reaction with trace Lewis acid contaminants in the solutions. The supe riority of LiAsF6 as an electrolyte for these solutions is attributed to the precipitation of elementary arsenic and arsenic compounds (e.g. , Li3As, LixAsFy) on lithium, which modifies Li deposition to become u niform and smooth.