Cu2Sb Thin-Film Electrodes Prepared by Pulsed Laser Deposition for Lithium Batteries

Abstract

Thin films of prepared on stainless steel and copper substrates with a pulsed laser deposition technique at room temperature, have been evaluated as electrodes in lithium cells. The electrodes operate by a lithium insertion/copper extrusion reaction mechanism, the reversibility of which is superior when copper substrates are used, particularly when electrochemical cycling is restricted to the voltage range 0.65-1.4 V vs. The superior performance of films on copper is attributed to the more active participation of the extruded copper in the functioning of the electrode. The continual and extensive extrusion of copper on cycling the cells leads to the isolation of particles and a consequent formation of Sb. Improved cycling stability of both types of electrodes was obtained when cells were cycled between 0.65 and 1.4 V. A low-capacity lithium-ion cell with and electrodes, laminated from powders, shows excellent cycling stability over the voltage range 3.15-2.2 V, the potential difference corresponding to approximately 0.65-1.4 V for the electrode vs. Chemical self-discharge of lithiated electrodes by reaction with the electrolyte was severe when cells were allowed to relax on open circuit after reaching a lower voltage limit of 0.1 V. The solid electrolyte interphase (SEI) layer formed on electrodes after cells had been cycled between 1.4 and 0.65 V vs. was characterized by Fourier transform infrared spectroscopy; the SEI layer contributes to the large irreversible capacity loss on the initial cycle of these cells. The data contribute to a better understanding of the electrochemical behavior of intermetallic electrodes in rechargeable lithium batteries. © 2004 The Electrochemical Society. All rights reserved.