Premium
6/7 Li NMR study of the Li 1– z Ni 1+ z O 2 phases
Author(s) -
Chazel Cédric,
Ménétrier Michel,
Croguennec Laurence,
Delmas Claude
Publication year - 2005
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1639
Subject(s) - chemistry , stoichiometry , carbon 13 nmr satellite , anisotropy , nmr spectra database , homonuclear molecule , magic angle spinning , carbon 13 nmr , analytical chemistry (journal) , crystallography , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , spectral line , fluorine 19 nmr , molecule , stereochemistry , physics , organic chemistry , quantum mechanics , astronomy
A series of Li 1− z Ni 1+ z O 2 materials have been synthesised by the coprecipitation route. An X‐ray diffraction study was carried out on these materials using the Rietveld method to determine the departure from the ideal stoichiometry z , which ranges from 0 to 0.138. The actual Li/Ni ratio was also checked by chemical analyses using inductively coupled plasma (ICP) for each sample. The stoichiometric sample ( z ∼ 0) was obtained using a 15% Li excess. 6/7 Li NMR results from LiNiO 2 ( z ∼ 0) show that the asymmetric shape of the NMR signal is due to anisotropy. Calculations give evidence that the paramagnetic dipolar interaction from the electron spins carried by Ni is anisotropic but does not completely explain the experimental anisotropy. 6 Li MAS NMR (magic angle spinning NMR) experiments and temperature standardisation NMR measurements unambiguously assign the isotropic position at +726 ppm. The static‐echo NMR spectra of the non‐stoichiometric Li 1− z Ni 1+ z O 2 phases also exhibit an asymmetric shape whose width increases with the departure from the ideal stoichiometry z . 6/7 Li static and MAS NMR show that the 2 z Ni 2+ ions thus formed modify the dipolar interaction within the materials and also affect the Fermi contact interaction, since a distribution of Li environments is observed using 6 Li NMR for non‐stoichiometric samples. Copyright © 2005 John Wiley & Sons, Ltd.