CATALYTIC GRAPHITIZATION BY LIGHT METALS

Abstract

The catalytic effects of light metals (Mg and Li) on the graphitization process and the effects of precursors, blending conditions, heating conditions, and additives on the graphitization rate and the final graphite morphology were studied using a variety of techniques. Many interesting chemistries were discovered and discussed. These findings could guide to further understanding of the catalytic graphitization process and the resulting products. In general, Mg is a much better graphitization catalyst than Li. Both Mg and Li catalysts were easily removed, resulting in highly pure graphite products. Graphite with various morphologies were discovered, including Voronoi tessellated graphite and hexagonal platelet graphite made from glucose, spherical graphites made from C-Mg-MgCl2 melts, and graphitic dendrites made from cellulose and C-Mg-Al melts, etc. Different morphologies suggested different graphitization mechanisms. The basic mechanism of Mg-catalytic graphite growth might be a combination of carbon dissolution-precipitation and carbide formation-decomposition. Many catalytic graphites are highly graphitized. When cycled in Li half-cells, these graphites displayed good cycling stability and high reversible capacity. The electrochemical performance of some graphites is comparable to battery grade commercial graphites.