Effect of magnesium substitution on the cycling behavior of lithium nickel cobalt oxide

• Published in: Journal of power sources 2001-06, Vol.96 (2), p.293-302
• Main Authors: Pouillerie, C, Perton, F, Biensan, Ph, Pérès, J.P, Broussely, M, Delmas, C
• Format: Article
• Language: English
• Subjects: Applied sciences; Cycling; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Lithium batteries; Lithium-ion batteries; Rietveld refinement; Substituted lithium nickelate
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/S0378-7753(00)00653-4

LiNi 0.91Co 0.09O 2 and LiNi 0.86Co 0.09Mg 0.05O 2 phases were comparatively cycled in 4/5 ‘A’-size lithium-ion cells (500 cycles, 60°C, C rate, 2 h floating at 4.1 V at each charge). The MgCo substituted positive electrodes exhibit a very small capacity fading versus the Co substituted one. Comparative Rietveld refinements of the XRD patterns before and after cycling show unambiguously that an irreversible migration of Mg 2+ ions from the slabs to the interslab spaces occurs upon cycling. The variation of the cell parameters of the Li x Ni 0.86Co 0.09Mg 0.05O 2 deintercalated phases, obtained during the 1st and the 501st charges, were determined. The smaller changes observed after the Mg-migration suggest that the mechanical constraints typically observed during lithium intercalation–deintercalation are reduced by the simultaneous presence of magnesium ions in the lithium sites and of vacancies in the slabs, leading to a smaller capacity fading.