Reinvestigation of the OP4-(Li/Na)CoO2- layered system and first evidence of the (Li/Na/NaCoO2 phase with OPP9 oxygen stacking

Romain Berthelot (1) , Michaël Pollet (1) , Dany Carlier-Larregaray (1) , Claude Delmas (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The composition and synthesis conditions of the (Li/Na)CoO₂ phase with an ordered 1:1 Li/Na stacking alternating with CoO₂ slabs were determined from a careful study of the P2-Na_0.7CoO₂−O3-LiCoO₂ system. An in situ X-ray diffraction (XRD) thermal study emphasizes the metastable character of this phase that can be stabilized only by very fast quenching. Its composition, (Li_0.42Na_0.37)CoO₂, is significantly different from the ideally expected one, (Li_0.50Na_0.35)CoO₂, and its structure, confirmed by Rietveld refinement of the XRD pattern, presents an ideal alternate ordering of lithium, cobalt, and sodium layers within OP4-type oxygen packing. The presence of vacancies in both alkali-ion layers was confirmed by electrochemical intercalation of lithium and sodium. For the first time, a new type of layered oxide exhibiting OPP9-type oxygen packing was evidenced. Between the CoO₂ slabs, alkali ions are intercalated in the following order: Li_octa−Na_prism−Na_prism. This material crystallizes in the Rm space group with a_hex = 2.828 Å and c_hex = 46.85 Å cell parameters.

Domaines: Matériaux

Romain Berthelot, Michaël Pollet, Dany Carlier-Larregaray, Claude Delmas. Reinvestigation of the OP4-(Li/Na)CoO2- layered system and first evidence of the (Li/Na/NaCoO2 phase with OPP9 oxygen stacking. Inorganic Chemistry, 2011, 50 (6), pp.2420-2430. ⟨10.1021/ic102218w⟩. ⟨hal-00577803⟩