Catalytically Graphitized Nanostructured Carbon Xerogels As High Performance Anode Material for Lithium Ion Battery

Abstract

Carbon materials are most widely used anode materials for Lithium ion battery since their introduction in 1991. Among various types of carbonaceous materials, graphite is still being used widely as anode material in commercial Lithium ion batteries because of its reasonable capacity and good cyclic efficiency. The problem with long term availability and less purity of macro crystalline natural graphite which is more suitable for battery application led researchers to look into preparation of synthetic graphite, basically prepared by carbonizing various graphitizing carbons like petroleum coke, pitch coke etc.. Various other forms of carbons and their composites have been tested for Li ion intercalation. Though they have higher capacity, their poor cyclability and higher irreversible capacity, higher reduction potential restrict them as commercial Li ion battery anode. Other than carbon materials, Ti, Si and Sn based alloys and oxides have been reported in recent years with 3 to 5 times increase in their intercalation capacity compared to graphite but capacity fade is high due to pulverization. In this presentation, we will present the ways to capitalize the higher capacity of hard (non graphitizing) carbons but at the same time minimizing the irreversible capacity losses and thus maximizing the energy density by catalytic graphitizing them at much lower temperature (< 1800 0C) than as usual graphitization temperature (2800-30000C). Although it is reported that control of internal nanostructure is difficult during catalytic graphitization of various organic precursors, some of the recent studies show that for organic aerogels, one can tune porosity by controlling synthesis and processing conditions during the catalytic graphitization. However although highly porous aerogels shows higher initial capacity due to adsorption of lithium ions inside the pores but also have larger irreversible capacity due to increased overall resistance (impedance) by increased double layer capacitance of the active electrode material. In this work, we shall present preparation of RF xerogel derived graphitic carbon with controlled porosity and thus specific surface area by catalytic graphitization in which metal nanoparticles as additive will be mixed with RF sol. During graphitization, these embedded metal additives react with carbon and forms metal carbide before decomposing to form graphite which will act as nuclei for further graphitization. Intercalation capacity of carbon xerogels have been earlier reported as 145 mAh/g however catalytic graphitization of these xerogels not only enhances it significantly but also increase the electrical conductivity by ordering of graphite layers in disordered carbon xerogels, which are the important characteristics of good electrode material. Thus, these nanoporous graphitic carbon behaves as an excellent anode material because of their minimal double layer capacitance compared to aerogels and good inlayer conductivity because of graphitization.