Improved electrochemical performance of modified natural graphite anode for lithium secondary batteries

Modified natural graphite is synthesized by surface coating and graphitizing process on the base of spherical natural graphite. The modified natural graphite is examined discharge capacity and coulombic efficiency for the initial charge-discharge cycle. Modification process results in marked improvement in electrochemical performance for a larger discharge capacity and better coulombic efficiency. The mechanism of the enhancement are investigated by means of X-ray powder diffraction, scan electron microscopy, and physical parameters examination. The proportion of rhombohedral crystal structure was reduced by the heat treatment process. The modified natural graphite exhibits 40 mAh g(-1) reduction in the first irreversible capacity while the reversible capacity increased by 16 mAh g(-1) in comparison with pristine graphite electrode. Also, it has an excellent capacity retention of similar to 94% after 100 cycles and similar to 87% after 300 cycles. (C) 2007 Elsevier B.V. All rights reserved.