Enhanced catalytic graphitization of resorcinol formaldehyde derived carbon xerogel to improve its anodic performance for lithium ion battery

Abstract

Resorcinol-formaldehyde (RF)–derived carbon xerogels are hard carbons, which are not explored thoroughly as anodes in lithium-ion batteries as they exhibit poor crystallinity, conductivity and significant capacity fading during cycling. Graphitization of hard carbons, using metal catalysts at elevated temperatures, may be an effective method to enhance their crystallinity. In this study, RF xerogels were graphitized using an iron catalyst at a moderate temperature (1100 °C) in nitrogen atmosphere. Three different catalyst loadings (2, 5, and 10 wt. %) were used to study the extent of graphitization and thereby the effect on physiochemical properties of these RF-derived carbon xerogels. X-ray diffraction and Raman spectroscopy revealed an increase in the degree of graphitization and crystallinity, while high-resolution transmission electron micrographs showed an enhancement in the structural ordering of graphene layers with increase in catalyst loading. Interestingly, when tested electrochemically, the 5 wt.% catalyst loaded RF carbon xerogel was found to exhibit the best anodic performance as ever reported. A specific reversible capacity of 470 mA h/g at 0.2 C rate was retained even after 100 continuous charge/discharge cycles, with nearly 100% columbic efficiency. Furthermore, even at high C-rates (1C), a reasonably high reversible capacity of 348 mA h/g was maintained during cycling.