On the mechanism of the P2-Na0.70CoO2→O2-LiCoO2 exchange reaction -: Part I:: proposition of a model to describe the P2-O2 transition

A model was proposed to describe the exchange reaction of sodium by lithium in P2 crystals. The exchange consists oil the formation of nucleation centers and then on the growth of 02 domains in P2 crystals from these nucleation centers. Octahedral environments for lithium ions are obtained when one slab over two glides by (2/3,1/3,0) or by (1/3,2/3,0) in P2 structure. The existence of two different gliding vectors should lead to stacking faulted structures that can be simulated using DIFFaX software. The comparison of simulated and experimental XRD patterns for O2-LiCoO2 (ex-Na0.7CoO2) has shown that in that case the growth of the O2 domains in the P2 crystals is faster than the formation of nucleation centers. (C) 2004 Elsevier Inc. All rights reserved.