ELECTROCHEMICAL INTERCALATION OF LITHIUM INTO GRAPHITE

The results of a study of the electrochemical intercalation of lithium into Lonza KS15 artificial graphite in 1M LiClO4 PC/EC (50:50) electrolyte are presented here. Electrolyte decomposition reactions occur during the first discharge at about 0.8 V vs. Li metal and their extent is greatly reduced-by addition of crown ethers with 12 crown 4 being most effective. A mechanism is proposed for electrolyte decomposition reactions which includes at least two types of process, namely, propylene and ethylene evolution and formation on the surface of graphite of a solid electrolyte interphase film which includes lithium alkyl carbonates. The stoichiometry of lithium intercalation into graphite is found to be inversely dependent on the cycling rates and electrode thickness and proportional to the amount of carbon black added to the graphite.