Several small models of graphite, lithium intercalated graphite (LJG) and lithium have been calculated at the ab initio/HF and DFT/B3LYP levels with the 6-31G and 6-31G~* basis sets to explore the charging-discharging mechanism of 1IG as a negative electrode in the secondary lithium battery. The obtained results demonstrate that, whilst lithium enters and leaves the graphite lattices reversibly, the continuous charge transfer between lithium and the graphite layers synchronizes with the shift of the graphite layer stacking sequences between the AB type and the AA type. Additionally, die processes of the lithium intercalation into and deintercalation out of graphite lattices are essentially that the secondary lithium battery deposits and releases the electric energy, respectively. The above charging- discharging mechanism of 1JG enriches the SEI (solid electrolyte interphase) mechanism and single electron reduction mechanism of lithium into graphite very well.

Key words: AB INITIO CALCULATION, LITHIUM ION, BATTERIES, GRAPHITE, REDUCTION