Using Gaussian and HF, via ab initio method and selecting 4-31G basis set, the transformation connection between the structure and binding energy was investigated in the process of lithium ion interca-lating into polythiophene. And when the thiophene polymerized, it was found that tri-polymer or tetra-polymer were main products. As the intercalation of lithium atom (or Li^＋ ion ) into the polymer, the distance between the polythiophenes was shortened obviously. At the same time, the intercalation substances became stable due to the electric charges transferring, which made bond order of the C-α—C-β decreased in the thiophene. The HOMO, LUMO energy level of the system was calculated when the lithium ion (or atom) intercalated into. The LUMO orbit energy level of polythiophene turned negative with the lithium ion intercalating into, and became the positive pole of the cell reaction that received electron. While after the metal Li₂ released Li^＋, the HOMO energy level of Li^－ was 0.7427 eV, and became the negative pole which was given electron. Thus, the discharge process of lithium/polythiophene was finished in the electrolyte of the lithium perchlorate. It was also indicated that the conception of the intercalation bond order was used to denote the combination degree of lithium between the polythiophene.

Key words: intercalated compound, bond order, intercalated bond order, cell reaction