Electrochemical properties of PAN-based carbon fibers as anodes for rechargeable lithium ion batteries

Polyacrylonitrile(PAN)-based carbon fibers were tested as anodes for Lithium ion rechargeable batteries. PAN-based fibers were first stabilized under tension in air at about 200 degreesC (stabilization tension) and then carbonized in different gas environments (carbonization atmospheres) at heat treatment temperatures (HTT) between 700 and 1500 degreesC. The carbon fiber electrodes were prepared at various conditions using the stabilized PAN fibers and then their electrochemical characteristics were investigated. The PAN-based carbon fiber prepared at an oxidative stabilization tension of ca. 10 MPa showed the highest discharge capacity in our experimental range. We found that the effective diffusion coefficient of lithium in the carbon fiber electrode was influenced by the carbonization environment employed. The electrochemical intercalation process depended on mass transfer of lithium into carbon layer which is rate-determining during the electrode charge-discharge process. The effect of HTT on discharge capacity varied depending on the combined effect of both the amount of intercalation sites available and the electric conductivity of the carbon fiber used. (C) 2001 Elsevier Science Ltd. All rights reserved.