IRREVERSIBLE CAPACITY OF LITHIUM SECONDARY BATTERY USING MESO-CARBON MICRO BEADS AS ANODE MATERIAL

One of the most important problems in lithium secondary battery using carbon anodes is the difference between the charge and discharge capac ity, the so-called 'retention'. It is caused partly by the reaction of Li ion with functional groups on the surface of the carbon. Especiall y, carbons heat-treated at lower temperatures than 1000 degrees C, hav e many functional groups such as -COOH and -OH on the surface. As thes e functional groups are very reactive, Li ions might smoothly react wi th them in the initial charge-reaction process. In order to evaluate t hese contributions to the irreversible capacity, the n-butyllithium me thod was applied for meso-carbon micro beads (MCMB) heat-treated at lo wer temperatures than 1000 degrees C. As a result, there are some reac tive sites such as functional groups and cavities against Li ions exce pt interlayers. However, the irreversible capacity due to the function al groups is a minor factor, and the dominant factor is due to the dec omposition of the solvent followed by the film formation on the surfac e of the carbon electrode or/and the doping of Li species into the rea ctive sites such as cavities.