CHARGE-DISCHARGE PROPERTIES OF COMPOSITE OF SYNTHETIC GRAPHITE AND POLY(3-N-HEXYLTHIOPHENE) AS AN ANODE ACTIVE MATERIAL IN RECHARGEABLE LITHIUM-ION BATTERIES

Electrochemical properties of a composite film made from synthetic gra phite and poly(3-n-hexylthiophene) (graphite/PHT) have been studied wi th focusing its use as an anode active material in rechargeable lithiu m-ion batteries. When a graphite-free PHT film was used as anode activ e material, a charge capacity of 43.5 mAh g(-1) and coulombic efficien cy of 94.6% were obtained in a potential range between 2.0 and 0 V vs. Li/Li+. Charge-discharge tests of the graphite/PHT (10.00 mg graphite , 1.10 mg PHT) indicated a specific capacity of 312 mAh g(-1) for the deintercalation of Li-. By subtracting the capacity involved in the re dox reaction of PHT from the capacity of the graphite/PMT, the utiliza tion of graphite was determined to be 0.92, which implies that the che mical formula of C6.52Li, was obtained. This result is in accordance w ith that obtained for an electrode prepared by using poly(vinylidene-f luoride) as a binder (graphite/PVDF). The irreversible capacity which appeared during the first cycle of the charge-discharge test of the gr aphite was apparently reduced by the use of PHT as the binder in place of PVDF. the degree being greater with an increase in the amount of P HT in the electrode. The n-type doped PHT of graphite/PMT served as a good electrically conducting binder for graphite, requiring no mechani cal pressing in electrode preparation.