Thermal behavior of Li1-xNiO2 (R3̄m or C2/m) up to 400°C was studied using thermogravimetry (TG), differential scanning calorimetry (DSC), and high-temperature X-ray diffraction measurements and its decomposition mechanism was proposed. Delithiated Li1-xNiO2 was thermally decomposed to LiNi2O4 spinel (Fd3m) at the temperature range of 180-250°C. For x ≤ 0.5, Li1-xNiO2 was decomposed to LiNiO2 and LiNi2O4 and the fraction of the spinel in the decomposed product increased almost linearly with x. For 0.5 < x ≤ 0.8, Li1-xNiO2 was converted into LiNi2O4 spinel and this reaction was accompanied by oxygen evolution. Li1-xNiO2 of all compositions turned into a rock-salt phase (Fm3m) with oxygen liberation at temperatures above 270°C. The temperature for the decomposition of Li1-xNiO2 to a spinel or a rock-salt phase decreased with x in Li1-xNiO2. The thermal behavior of Li1-xNiO2 could be interpreted as an overlap of the exothermic rearrangement of cations (nickel and lithium ions) to form a spinel or a rock-salt phase and the endothermic oxygen evolution reaction.
Bibliographical noteFunding Information:
Authors would like to thank LG Chemical Ltd. for financial support and Korea Basic Institute for TG and DSC Measurement. This study was supported by the Brain Korea 21 project.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Energy Engineering and Power Technology
- Physical and Theoretical Chemistry
- Electrical and Electronic Engineering