Electrochemical Reaction Between Lithium and β-Quartz GeO[sub 2]

Abstract

A first study on the electrochemical reaction between lithium and germania (β-quartz germanium oxide) is reported. Galvanostatic and potentiostatic discharges are defined by three voltage regions where different processes take place. In region I, delimited between open-circuit voltage and 0.65 V vs. some germania particles may react with lithium to form an amorphous lithium germanate, detectable by infrared spectroscopic measurements. Crystallinity degradation is also observed in region II (0.55-0.35 V) where germania and lithium germanate react with 4.2 mol of Li to yield a germanium/lithia nanocomposite and LiGe. Region III (0.35-0.05 V) corresponds to further reaction between lithium and germanium particles that promotes huge volume changes in the electrode. A solid electrolyte interface (SEI) developed at every step of discharge thus consuming extra lithium. Both factors, the particles expansion and the SEI, are mainly responsible for capacity fade upon cycling. © 2004 The Electrochemical Society. All rights reserved.