Structural Relaxation of Li x Ni 0.874 Co 0.090 Al 0.036 O 2 after Lithium Extraction down to (x ≤ 0.12)

Abstract

Structural relaxation experiments have been carried out on Lix(Ni0.874Co0.090Al0.036)O2 (Co-9.0 NCA) after the lithium extraction down to x ≤ 0.12. X-ray diffraction has been made during the relaxation process, which were analyzed by the Rietveld method assuming two phases (H2 and H3) co-existence with R-3m symmetry. For the lithium extraction to x = 0.12, Co-9.0 NCA seems to show single H2 phase for all the relaxation period, while H2 and H3 coexistence is detected for x = 0.09 or 0.06. Even for the smaller lithium concentration region, H2 phase is predominant rather than H3. Comparing with the previous study of LiNiO2 and Co-3.1 NCA, very small H2-H3 transition has been observed during the relaxation time, which is due to the relatively larger c-length in H3 phase for highly extracted region (x = 0.06).