Effect of Li-Doping on Electrochemical Performance of Natural Graphite Anode for Lithium Secondary Batteries

Abstract

Lithium-doped natural graphite to be used as an anode material for lithium secondary batteries was synthesized by a simple wet ballmilling method. The Li-doping of the natural graphite greatly improved the cycling stability, coulombic efficiency in the first charge-discharge cycle (irreversible capacity), and C-rate performance of the material. The Li-doped graphite exhibited an excellent capacity retention of ∼99% after 50 cycles. The graphite electrode-doped lithium also showed ∼5% reduction in the first irreversible capacity while the reversible capacity remained unchanged in comparison with the pristine graphite electrode. It was shown using transmission electron microscopy that Li atoms intercalated at the edges of the natural graphite. It is conjectured that the intercalated Li atoms at the edges prior to cycling help to reduce the electrolyte breakdown by passivating the highly reactive sites along the edge planes, thus improving the cycling stability. © 2004 The Electrochemical Society. All rights reserved.