A hard carbon/microcrystalline graphite/carbon composite with a core-shell structure as novel anode materials for lithium-ion batteries

Hard carbon and microcrystalline graphite (MG) core-shell structured composite materials are prepared, and their electrochemical performances as an anode material for lithium-ion batteries are reported. The composite materials are obtained by coating a mixture of MG and pitch onto hard carbon particles, followed by heating at 1200 degrees C under an argon atmosphere for 1 h. The surface of the hard carbon is subsequently covered with a layer of the MG/pitch carbon composite. In the coating layer of the MG/pitch carbon composite, the MG particles are divided into nanoscale graphite sheets, and uniformly dispersed within the pitch of carbon matrix. The composite particles have a rounded shape, especially when the content of MG increases, which can improve their packing density compared to hard carbon having sharp edges. Anodes prepared from these composite materials exhibit enhanced electrochemical performances, including a high reversible capacity, high initial coulombic efficiency, high charging/discharging rate capability, and desirable cycling stability. (C) 2014 Elsevier Ltd. All rights reserved.