The Performances of Li Secondary Battery Using Various Kinds of Graphite Fibers as a Positive Electrode

Abstract

In order to develop Li secondary battery with high performances, various kind of graphite fibers were used as a positive electrode of Li secondary battery. The characteristics of Li/LiClO₄-PC/graphite fibers battery, charging and discharging properties and discharging capacity were examined, and the battery performances were evaluated as functions of the structure of the fibers. Highly ordered vapor-grown graphite fibers heat treated at 2700°C showed the cell potential as high as 4.5V (2mA out-put current, vs Li) with high out-put stability. More than 400 times of charge and discharge cycles were possible. The fibers heat-treated at 2740°C showed the 270C/g of capacity (at 5mA out-put current) and the out-put energy density of 310 Wh/kg. Other types of graphite fibers exhibited less performances than those of the well-ordered ones. It is shown that with increasing the crystallite thickness of the fibers, the performance is largely improved.