The role of nickel content on the structure and electrochemical properties of Li x(Ni yCo 1− y)O 2

• Published in: Journal of power sources Vol. 97; pp. 316 - 320
• Main Authors: Gover, Richard K.B., Kanno, Ryoji, Mitchell, Brian J., Hirano, Atsushi, Kawamoto, Yoji
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2001
• Subjects: Charge/discharge properties; Structure analysis; X-ray diffraction; X-ray diffraction; Structure analysis; Charge/discharge properties
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/S0378-7753(01)00623-1

Samples have been prepared with nominal composition Li x (Ni y Co 1− y )O 2 ( x≈1.25, y=0.7–1.0) with the structures being examined using Rietveld analysis of X-ray diffraction data. Rietveld analysis shows that the samples prepared with y=0.70 and 0.75 have no Ni present on the 3a Li site, with all other samples showing a small degree of nonstoichiometry. Structural analysis of the 3b Ni+Co occupancy also suggests the possibility of 3b site disorder, which is in agreement with the results of previous studies. Charge/discharge measurements show an increase in discharge capacity with increasing Ni content, which suggests cobalt plays a very small part in the electrochemical capacities of these phases using the current voltage limits. Samples with y=0.75, 0.8 and 0.85 were found to have very high efficiencies over a number of cycles, typically >99% over 15 cycles. Samples prepared with y=0.85 and 0.90 show evidence of a phase change which resembles that seen for LiNiO 2. This would suggest that the stabilizing effects of Co in Li x (Ni y Co 1− y )O 2 is lost when y≥0.85. Therefore, these particular compositions are probably not suitable for use in Li ion cells.