Y. Shaohorn et al., STRUCTURAL FEATURES OF LOW-TEMPERATURE LICOO2 AND ACID-DELITHIATED PRODUCTS, Journal of solid state chemistry (Print), 140(1), 1998, pp. 116-127
X-ray diffraction and transmission electron microscopy were used to st
udy the structural features of low-temperature LiCoO2, (LT-LiCoO2) sam
ples prepared at 400 degrees C either by a simple solid-state reaction
or via a sol-gel process. Single-crystal electron diffraction analysi
s showed that both a lithiated-spinel Li, [Co-2]O-4 (Fd3m) and a layer
ed-type structure (R (3) over bar m) were present in LT-LiCoO2, sample
s hut that the lithiated-spinel structure was the major phase. Electro
n diffraction analysis also indicated that some crystallites in the LT
-LiCoO2, samples had a cation distribution in the spinel notation, {(L
i16-4x)(16c)[Li-4x](16d)}(layer1) {(Co16-4x)(16d)[Co-4x](16c)}(layer2)
O-32 (0 < x < 1) that was intermediate between the ideal layered (x =
1) and ideal lithiated-spinel (x = 0) structures. Electron diffraction
confirmed that acid-delithiation of LT-LiCoO2, resulted in a lithium-
deficient spinel, Li-0.8[Co-2]O-4, with lithium ions on the tetrahedra
l sites of the spinel structure. The structural features of LT-LiCoO2,
and the acid-delithiated Li0.4CoO2 products provide reasons for the p
oor electrochemical properties of Li/LT-LiCoO2, cells and are consiste
nt with earlier studies. (C) 1998 Academic Press.