Coating of graphite anode with coal tar pitch as an effective precursor for enhancing the rate performance in Li-ion batteries: Effects of composition and softening points of coal tar pitch

Effects of compositions and softening points of coal tar pitches (CTPs) on the electrochemical performances especially for first cycle Coulombic efficiency and rate performance, of the amorphous carbon coating on the graphite surface were closely examined. CTPs with higher softening points could afford the better homogeneous amorphous carbon coating on the graphite surface, resulting in the better enhancing rate performance of graphite anode without decreasing the first cycle Coulombic efficiency. CTP with almost complete absence of hexane soluble (HS) fraction always showed the good enhancing effect of the rate performance. HS fraction of CTP, which is a reason for inducing surface defects on the coated carbon, hindered the enhancing effect of electrochemical performances. CTP derived amorphous carbon coating could effectively decrease charge transfer resistance on the graphite electrode–electrolyte interface.