In situ observation of LiNiO2 single-particle fracture during Li-ion extraction and insertion

Electrochemical lithium-ion extraction/insertion properties of Li1-xNiO2 si ngle particles were investigated by attaching a filament microelectrode to the particle in 1 mol/dm(3) LiClO4/ethylene carbonate + propylene carbonate electrolyte. High-resolution cyclic voltammograms and galvanostatic chrono potentiograms were recorded. In addition, we observed in situ particle frac ture during charge-discharge using an optical microscope equipped with a ch arge-coupled device camera. We found that the particle fractures when it is polarized above 4.2 V vs. Li/Li+. This phenomenon was explained by the cha nge in crystal parameters expected to occur for x > 0.75 in Li1-xNiO2. (C) 2000 The Electrochemical Society. S1099-0062(99)11-042-3. All rights reserv ed.