Improved electrochemical performance of Li-doped natural graphite anode for lithium secondary batteries

Lithium-doped natural graphite is synthesized by a simple wet ball-milling method and use as an anode material in lithium secondary batteries. The modified natural graphite is examined with a view to improved cycleability and columbic efficiency on the first charge-discharge cycle (irreversible capacity loss). Lithium-doping results in marked improvements in electrochemical performance. These are investigated by means of X-ray powder diffraction, impedance measurement, high resolution transmission electron microscopy, field emission scanning electron microscopy, and measurement of electrochemical capacity. LiOx intercalated at the edge planes reduces the electrolyte breakdown by passivating the highly reactive sites along these planes. The Li-doped natural graphite exhibits similar to5% reduction in the first irreversible capacity while the reversible capacity remains unchanged in comparison with pristine graphite electrode. Also, it has an excellent capacity retention of similar to99% after 50 cycles. (C) 2004 Elsevier B.V. All rights reserved.