Catalytic graphitization of resorcinol-formaldehyde xerogel and its effect on lithium ion intercalation

Abstract

Resorcinol formaldehyde (RF) derived xerogels were synthesized by polymerization of resorcinol and formaldehyde using sol–gel method followed by sub-critical drying. Thus prepared RF xerogel samples were then pyrolyzed at different temperatures ranging from 900 to 1800°C with and without catalyst to understand the role of catalyst in graphitization while varying the temperature. These RF derived carbon xerogels were structurally characterized extensively by Raman spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy and small angle X-ray scattering. Structural characterization studies confirmed that RF xerogels pyrolyzed at moderate temperatures in the presence of a catalyst were graphitized however the degree of graphitization achieved was only 10% in case of no catalyst even at elevated temperatures (2500°C). Later, these RF derived catalytically graphitized carbon xerogels were tested for their electrochemical performance as potential anode materials for rechargeable batteries. Galvanostatic charge discharge experiments were performed at 0.1C rate (37.2mA/g current density) to examine the effect of degree of graphitization on lithium ion intercalation. It was found that with increased degree of graphitization, specific capacity increased with decrease in irreversible capacity along with excellent cyclic stability and coulombic efficiency more than 97%.