Electrochemical reaction between lithium and beta-quartz GeO2

A first study on the electrochemical reaction between lithium and germania (beta-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. Li+/Li, some germania particles may react with lithium to form an amorphous lithium germanate, (Li2O)(y)GeO2, 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. (C) 2004 The Electrochemical Society.