Structural characterization of Li1-z-xNi1+zO2 by neutron diffraction

Pristine Li1-zNi1+zO2 (z = 0.02, 0.07, and 0.25) and deintercalated LixNi1. 02O2 (x = 0.82 and 0.63) phases were characterized by neutron diffraction, In all cases, the amount of nickel in the lithium sites was found to be ide ntical to that deduced from X-ray diffraction experiments. The sensitivity of the neutron studies allowed us to show that no lithium ions are in the N iO2 slabs for z = 0.02 and 0.07, A Li/Ni mixing appears only for the most l ithium-deficient phase leading to the [Li0.73Ni0.27](3b)[Ni0.98Li0.02](3a)O -2 cationic distribution for the Li0.75Ni1.25O2 phase. Determination of the anisotropic atomic displacement parameters confirms the results previously obtained from EXAFS data. The structural characterization of partially dei ntercalated phases was in good agreement with the XRD analysis. However, in the case of Li0.63Ni1.02O2, it gave evidence for the presence of a small a mount of rhombohedral phase due to fluctuations in the composition of the s tarting material. (C) 2001 Academic Press.