The structure of lithium intercalated graphite using an effective atomic charge of lithium

Using the experimental graphene layer spacing of the stage 1 model as a con straint, the effective atomic charge of lithium, delta (Li), in lithium-int ercalated graphite (LIG) was determined. In order to confirm that Lithium i n LIG exists in a partially ionic state, quantum mechanical calculations we re also carried out for several lithium-carbon systems. Using a fixed delta (Li), the graphene layer spacing and structures for hexagonal graphite, st age 3, stage 2, and stage 1 models, were obtained. The more lithium is inte rcalated into the graphite, the wider the layer spacing becomes. The distor tion of structures due to Lithium intercalation was not observed until the stage 1 model was formed. In stage 1 and stage 2 models, the graphene layer s shifted from ABAB to AAAA stacking as lithium was intercalated to the hex agonal graphite. However, the stage 3 model showed a shift of layers from A BABAB to AB'AAB"A stacking, where B' and B" represent the graphene layers w hich have shifted slightly from B. Only the graphene layers that have the i ntercalated lithium layers between them shifted to AA stacking. (C) 2001 Th e Electrochemical Society.