Structural Relaxation of LixNi0.8Co0.1Mn0.1O2 and LixNi0.55Co0.20Mn0.25O2 after Lithium Extraction to High Voltage Region (x ≤ 0.12) at 0.1 C-rate

The structural relaxation analysis has been carried out on LixNi0.8Co0.1Mn0.1O2 (NCM-811) and LixNi0.55Co0.20Mn0.25O2 (NCM-552025) after the lithium extraction at 0.1 C-rate to the high-voltage region (x ≤ 0.12). For NCM-811, the H3 phase appeared as the major phase with a small amount of the H2 phase after the lithium extraction. At the relaxation period, no significant phase change was observed and the structural variation including Li- and Ni-interlayer distances was small. On the other hand, NCM-552025 exhibited the single phase of the H2 even at deep lithium extraction up to x = 0.06. In the H2 phase, a slight increase in c-length was observed during the relaxation, which is the result of an increase in the Li-interlayer distance with a decrease in the Ni-interlayer. The relaxation behavior of interlayer distances can be explained by the localization of a small number of mobile lithium-ions.