Evaluation of Carbon Fibers as An Anode Material of Lithium Ion Secondary Battery and Their Performances

Abstract

In the present paper, various kinds of carbon fibers were studied in order to cover a wide range of crystallinity from disordered to highly graphitized materials. Poly-p-phenylene (PPP)-based granular carbon was also comparatively chosen as one of the highly disordered carbons against low crystalline carbon fibers. The discharge capacity of carbon fiber electrode was shown to depend on the crystallite thickness Lc002. Disordered and well-ordered carbon fibers had larger capacity than those with intermediate crystalline thickness. Milled mesophase pitch-based carbon fibers (MPCF) showed the highest capacity in fibers with high crystallinity, which seemed to be applicable for practical cell. 1 at % B-doped mesophase pitch-based carbon fiber indicated improvement in crystallite thickness and discharge capacity. It was suggested in the present paper that the crystallite thickness of carbon electrode is one of the most important factor for design of Li ion battery. Furthermore well controlled mesophase pitch-based carbon fibers as well as B-doped one are very promissing for the practical application for Li ion battery.