Synthesis and characterization of new LiNi1-yMgyO2 positive electrode materials for lithium-ion batteries

• Published in: Journal of the Electrochemical Society 2000-06, Vol.147 (6), p.2061-2069
• Main Authors: POUILLERIE, C, CROGUENNEC, L, BIENSAN, P, WILLMANN, P, DELMAS, C
• Format: Article
• Language: English
• Subjects: Applied sciences; 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
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1393486

New LiNi1-yMgyO2 (y = 0-0.20) layered oxides were synthesised by a coprecipitation method followed by a high-temperature thermal treatment. Rietveld refinements of their XRD patterns showed that they exhibit a quasi-two-dimensional structure, isostructural to LiNiO2, for small substitution amounts (y less than or equal to 0.10). For larger amounts (y = 0.15, 0.20), the Li/(Ni+Mg) ratio is significantly lower than unity. In all cases, the extra ions located in the interlayer space for lithium deficiency compensation are preferentially Mg2+ ions. A magnetic study confirmed the cationic distributions which result from the size difference between Ni3+ and Mg2+ ions. An electrochemical study showed reversible behaviour for all materials. A high capacity (greater than or equal to 150 Ah/kg) was found for LiNi1-yMgyO2 phases (y less than or equal to 0.02), which decreased when y increased. The presence of Mg2+ cations in the interlayer space, which cannot be oxidised and have a size close to Li+, prevents the local collapses of the structure which occurs for the Li1-zNi1+zO2 system; therefore good cycling stability is observed. 65 refs.