Relaxation Analysis of Li x Ni 0.8 Co 0.1 Mn 0.1 O 2 after Lithium Extraction to High-Voltage Region (x ≤ 0.12)

After the lithium extraction from LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM-811) to high-voltage region, structural variation has been investigated during relaxation process. When the lithium ions are extracted to x ≤ 0.12 for Li x Ni 0.8 Co 0.1 Mn 0.1 O 2 , H3 phase is mainly observed in addition to small amount of H2 phase. For highly lithium extraction up to x = 0.09 or 0.06, excess amount of H3 phase is created at the charging which turns into H2 at the relaxation. On the other hand, no significant variation is observed for the sample of x = 0.12. In comparison with LiNiO 2 , less amount of transformation from H3 to H2 occurs during the relaxation for NCM-811. For all the samples, Ni interlayer distance of H3 phase decreases with relaxation time, which is presumably due to the increase in valence of Ni for diminishment of lithium concentration in the remaining H3 phase.