D. Aurbach et al., THE STUDY OF ELECTROLYTE-SOLUTIONS BASED ON ETHYLENE AND DIETHYL CARBONATES FOR RECHARGEABLE LI BATTERIES .2. GRAPHITE-ELECTRODES, Journal of the Electrochemical Society, 142(9), 1995, pp. 2882-2890
The electrochemical behavior of Li-graphite intercalation anodes in et
hylene and diethyl carbonates (EC-DEC) solutions was studied using sur
face sensitive Fourier transform infrared spectroscopy (FTIR) and impe
dance spectroscopy in conjunction with standard electrochemical techni
ques. Three different solvent combinations, four different salts: LiBF
4, LiPF6, LiClO4, and LiAsF6, and the influence of the presence of CO2
were investigated. Graphite electrodes could be cycled hundreds of ti
mes obtaining a reasonable reversible capacity. The best electrolyte w
as found to be LiAsF6 and the presence of CO2 in solutions considerabl
y increased the reversible capacity upon cycling. This improved perfor
mance is due to precipitation of the ethylene carbonate reduction prod
uct, (CH2OCO2Li)(2), which is an excellent passivating agent, on the e
lectrode surface. Aging processes of these surface films and their inf
luence on the electrode properties are discussed.