Electrochemical Performance of Artificial Graphite Coated By Petroleum Pitch for Anode Material in Li-Ion Battery

Abstract

In recent years, carbon-based materials have been extensively investigated as anode materials for Li-ion battery (LIB). Carbon materials have been considered as promising materials for LIB anodes in portable electronic devices and electric/hybrid vehicles for their low material cost, abundance, nontoxicity and high capacity. Despite these advantages, the practical application of the carbon-based materials is still limited by their poor electrochemical performances. To enhance the electrochemical performances, we have performed the surface coating of graphite with pitch based on pyrolyzed fuel oil (PFO) using solvent fraction method. As solvents, n-hexane, toluene, tetrahydrofuran (THF) and quinoline were used. The PFO was heat-treated at 420 °C for 3 h to prepare the pitch and the softening point of prepared pitch was 240 °C. In this study, the effects of the solvent agents and graphite/pitch ratios on electrochemical performances were investigated. The PFO-pitch-coated graphite was analyzed by TGA, FE-SEM, and TEM. The coating thickness of the prepared graphite was about 100-500 nm and the graphite coated with THF solvent had a smoother surface than that using other solvents. Also the electrochemical performances of the PFO-pitch-coated graphite as an anode were investigated by constant current charge/discharge, cyclic voltammetry and impedance tests in the electrolyte of LiPF6 dissolved in organic solvents (EC:DEC=1:1 vol%). The coin cell using the PFO-pitch-coated graphite (Graphite:pitch =9:1 in weight) had the better discharge capacity (382 mAh/g) than that of other composition coin cells. Also, PFO-pitch-coated graphite was observed to give lower irreversible capacity and resistance than pristine graphite.