ANODE PERFORMANCE OF VAPOR-GROWN CARBON-FIBERS IN SECONDARY LITHIUM-ION BATTERIES

Chopped vapor-grown carbon fibers (VGCFs) were studied as anodes for secondary lithium ion batteries using a 1 mol . dm(-3) LiClO4 in a 1:1 (by volume) mixture of ethylene carbonate (EC) and diethylcarbonate (DEC) electrolyte. VGCFs were prepared from hydrocarbons by a vapor-grown method and chopped to ca. 10 mu m length. Three different diameters of the VGCFs, 1, 2, and 3 mu m (1GWH, 2GWH, and 3GWH, respectively) were used. The VGCFs chopped after graphitization (the 2A method-VGCFs) displayed a higher capacity than those chopped before (the 1A method-VGCFs). In particular, 2GWH-carbon, 1.6-fold higher than the capacity of 2GWH-1A; this is almost equal to the theoretical intercalation capacity of an ideal graphite (LiC5). The cyclic voltammogram of 2GWH-2A showed the most significantly different profile from that of natural graphite among all of the VGCFs. It is suggested that a new structural change is induced in the well-graphitized VGCFs during the chopping process that affects the lithium storage reaction.