Structure of Li 2MnO 3 with different degrees of defects

Abstract

The synthesis and structural properties of the layered oxide Li 2MnO 3 have been studied in details. It represents a key for a better understanding of the complex structural evolutions pointed out in the materials like Li(Li,Ni,Mn,Co)O 2 when they are used as positive electrode materials in lithium-ion batteries. Li 2MnO 3 samples were prepared either via coprecipitation or via a two step solid state reaction followed by different annealing treatments. Using X-ray and electron diffraction in combination with diffraction data simulations, we show that in function of the synthesis conditions, Li 2MnO 3 is obtained with various degrees of disorder, along the c monoclinic direction, in the stacking of the ordered Li 1/3Mn 2/3 sheets within the cfc oxygen packing. We show that this disorder decreases when the synthesis temperature increases but the synthesis of a material free of stacking faults is not possible with these synthesis routes. Finally, the similarities between the evolutions pointed out in Li 2MnO 3 due to the synthesis conditions and those previously observed in the materials like Li(Li,Ni,Mn,Co)O 2 related to the evolution of the cations distribution in the slabs are underlined.