Delmas, C. and Peres, J.P. and Rougier, A. and Demourgues, A. and Weill, F. and Chadwick, A.V. and Broussely, M. and Perton, F. and Biensan, P. and Willmann, P. (1997) On the behavior of the LixNiO2 system: an electrochemical and structural overview. In: 8th International Meeting on Lithium Batteries (IMLB 8), jUNE 16-21, 1996, Nagoya, Japan.
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Lithium nickel oxide exhibits a departure from stoichiometry (Li1-zNi1+zO2) consisting in the presence of extra-nickel ions within the lithium sites. Using optimized experimental synthesis conditions, compositions very close to the ideal stoichiometry (z = 0.02) can be obtained. By using the sensitivity of the lithium site isotropic temperature factor to the stoichiometry, the amount of extra-nickel ions can be determined in a very precise way. The loss of reversibility at the first cycle is mainly related to the change in the oxidation state of the extra-nickel ions, which induces a local collapse of the structure and makes difficult the lithium re-intercalation, A systematic structural study of LixNiO2 phases has been performed by extended X-ray absorption fine structure (EXAFS) as well as X-ray and electron diffraction. In the case of the starting Li0.98Ni1.02O2 phase, a local distortion of the NiO6 octahedra, resulting from a dynamic Jahn-Teller effect of low spin trivalent nickel ions has been evidenced from the EXAFS study. For the partially de-intercalated materials (0.50 < x < 0.75) which crystallize in the monoclinic system, the EXAFS study shows that the NiO6 octahedra are only slightly distorted due to the occurrence of a hopping phenomenon between Ni-IV and Ni-III. Electron diffraction experiments show the existence of a superstructure due to a peculiar lithium-ion ordering. Systematic electrochemical studies have shown that this ordering is strongly sensititve to the presence of extra-nickel ions. (C) 1997 Elsevier Science S.A.
|Item Type:||Conference or workshop item (Paper)|
|Uncontrolled keywords:||lithium; nickel oxides; intercalation|
|Depositing User:||T. Nasir|
|Date Deposited:||24 Oct 2009 14:56|
|Last Modified:||24 Oct 2009 14:56|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/18391 (The current URI for this page, for reference purposes)|
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