Li
Ni
2O
4 spi
nel-type phases were prepared by thermal treatme
nt of electrochemically dei
ntercalatedlayered Li
~0.5NiO
2. The phase tra
nsformatio
n was followed by
7Li NMR, showi
ng a gradual cha
nge ofthe sig
nal from the layered compou
nd. The characteristic sig
nal of the latter (related to local Li/vaca
ncya
nd Ni
3+/Ni
4+ orderi
ng) va
nishes after heati
ng to 150
ntities/deg.gif">C a
nd is replaced by a
new sig
nal showi
ng fasterexcha
nge ki
netics (origi
nati
ng from Ni
3+/Ni
4+ hoppi
ng arou
nd Li), which progressively tra
nsforms i
ntoa broad distributio
n of sig
nals. Arou
nd 200
ntities/deg.gif">C, a set of three positively shifted sig
nals is observed,correspo
ndi
ng to the appeara
nce of the spi
nel phase as see
n from XRD; these sig
nals disappear afterheati
ng to 240
ntities/deg.gif">C, correspo
ndi
ng to the begi
nni
ng of decompositio
n of the spi
nel i
nto a disordered
Rntities/thremacr.gif">
mtype phase with oxyge
n evolutio
n as previously show
n by Guilmard et al. (
Chem. Mater. 2003,
15, 4476a
nd 4484). I
n a
n ideal LiNi
2O
4 spi
nel, o
nly o
ne
7Li NMR sig
nal is expected. DFT (GGA) calculatio
nswere carried out a
nd show that the mecha
nism for the electro
n spi
n de
nsity tra
nsfer from NiO
6 octahedrato cor
ner-shari
ng LiO
4 tetrahedra with close to 120
ntities/deg.gif"> Ni-O-Li co
nfiguratio
n is a delocalizatio
n o
ne,although the p orbitals o
n oxyge
n do
not prese
nt ideal orie
ntatio
n, leadi
ng to a much weaker tra
nsfercompared to cases where both Ni a
nd Li are i
n octahedral coordi
natio
n with 180
ntities/deg.gif"> Ni-O-Li co
nfiguratio
n.The complex but well-defi
ned experime
ntal NMR sig
nals co
nsiste
ntly observed show that the materialis far from the ideal spi
nel structure. However, it could
not be correlated to the actual stoichiometry ofthe compou
nd. It was therefore te
ntatively assig
ned to structural defects resulti
ng from i
ncomplete migratio
nof Ni io
ns from their site to the Li layer i
n the pristi
ne compou
nd, such as partial occupatio
n of tetrahedralsites.