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 graphite and poly(3-n-hexylthiophene) (graphite/PHT) have been studied with focusing its use as an anode active material in rechargeable lithium-ion batteries. When a graphite-free PHT film was used as anode active material, a charge capacity of 43.5 mAh g(-1) and coulombic efficiency 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 redox reaction of PHT from the capacity of the graphite/PMT, the utilization of graphite was determined to be 0.92, which implies that the chemical formula of C6.52Li, was obtained. This result is in accordance with that obtained for an electrode prepared by using poly(vinylidene-fluoride) as a binder (graphite/PVDF). The irreversible capacity which appeared during the first cycle of the charge-discharge test of the graphite 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 PHT in the electrode. The n-type doped PHT of graphite/PMT served as a good electrically conducting binder for graphite, requiring no mechanical pressing in electrode preparation.