Structural and electrochemical properties of disordered carbon prepared bythe pyrolysis of poly(p-phenylene) below 1000 degrees C for the anode of alithium-ion battery

The structural and the charge-discharge characteristics of poly(p-phenylene )(PPP)-based carbon materials pyrolyzed at temperatures from 650 to 1000 de grees C are investigated by a series of structural analyses and charge-disc harge electrochemical techniques. The charge-discharge capacity is then cor related with the change in structure of the PPP-based carbon. It is found t hat the sizes of the crystallites only increase a little, while both the ch arge and the discharge capacities decrease sharply with increasing heat-tre atment temperature (HTT), and the carbon material pyrolyzed at 650 degrees C has the largest charge capacity (>600 mA h g(-1)). The charge capacity fo r each sample includes two components, one is probably related to that of l ithium intercalation into graphene layers, and the other to that of lithium species doped on the surface of the porosities existing in the PPP-based c arbon. The charge capacity of the first component hardly changes, while tha t of the second one decreases sharply with increasing HTT, which correspond s to a sharp decrease in the amount, the total specific surface areas of po rosity in carbon materials. Small pores can collapse and coalesce with each other and form larger pores due to an increase in crystal size when HTT in creases, resulting in an increase in the butanol displacement density. (C) 1999 Elsevier Science Ltd. All rights reserved.