Structural and electrochemical properties of disordered carbon prepared by the pyrolysis of poly(p-phenylene) below 1000°C for the anode of a lithium-ion battery

The structural and the charge-discharge characteristics of poly(p-phenylene)(PPP)-based carbon materials pyrolyzed at temperatures from 650 to 1000 degrees C are investigated by a series of structural analyses and charge-discharge electrochemical techniques. The charge-discharge capacity is then correlated with the change in structure of the PPP-based carbon. It is found that the sizes of the crystallites only increase a little, while both the charge and the discharge capacities decrease sharply with increasing heat-treatment temperature (HTT), and the carbon material pyrolyzed at 650 degrees C has the largest charge capacity (>600 mA h g(-1)). The charge capacity for each sample includes two components, one is probably related to that of lithium intercalation into graphene layers, and the other to that of lithium species doped on the surface of the porosities existing in the PPP-based carbon. The charge capacity of the first component hardly changes, while that of the second one decreases sharply with increasing HTT, which corresponds to a sharp decrease in the amount, the total specific surface areas of porosity 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 increases, resulting in an increase in the butanol displacement density. (C) 1999 Elsevier Science Ltd. All rights reserved.