CHAZEL, Cédric; MÉNÉTRIER, Michel; CROGUENNEC, Laurence; DELMAS, Claude

doi:10.1021/ic051593n

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CHAZEL, Cédric
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

MÉNÉTRIER, Michel
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

CROGUENNEC, Laurence
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

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Inorganic Chemistry. 2006, vol. vol. 45, n° 3, p. p. 1184-1191

American Chemical Society

Résumé en anglais

Deintercalated "LixNiO2" materials (x = 0.25, 0.33, 0.50, 0.58, and 0.65) were obtained using the electrochemical route from the Li0.985Ni1.015O2 and Li0.993Ni1.007O2 compounds. Refinements of X-ray diffraction data using the Rietveld method show a good agreement with the phase diagram of the LixNiO2 system studied earlier in this laboratory. Electronic conductivity measurements show a thermally activated electron-hopping process for the deintercalated Li0.5NiO2 phase. In the LixNiO2 materials investigated (x = 0.25, 0.33, 0.50, and 0.58), 7Li NMR shows mobility effects leading to an exchanged signal at room temperature. A clear tendency for Li to be surrounded mainly by Ni3+ ions with the 180 configuration is observed, particularly, for strongly deintercalated materials with smaller Li+ and Ni3+ contents, even upon heating, when this mobility becomes very fast in the NMR time scale. This suggests that Li/vacancy hopping does occur on the NMR time scale but that Ni3+/Ni4+ hopping does not occur independently. The position of Li seems to govern the oxidation state of the Ni around it at any time; the electrons follow the Li ions to satisfy local electroneutrality and minimal energy configuration. The observed NMR shifts are compatible with the Li/vacancy and Ni3+/Ni4+ ordering patterns calculated by Arroyo y de Dompablo et al. for x = 0.25 and x = 0.50, but not for x = 0.33 and x = 0.58.< Réduire

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Ion

Electron

Lithium batteries

Nuclear magnetic resonance

7Li

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Coupled Ion/Electron Hopping in LixNiO2: A 7Li NMR Study

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