Integrated Materials xLi[sub 2]MnO[sub 3]⋅(1−x)LiMn[sub 1/3]Ni[sub 1/3]Co[sub 1/3]O[sub 2] (x=0.3, 0.5, 0.7) Synthesized

Abstract

We report herein on the synthesis of “layered-layered” integrated xLi2MnO3⋅(1−x)LiMn1/3Ni1/3Co1/3O2xLi2MnO3⋅(1−x)LiMn1/3Ni1/3Co1/3O2 materials ( x=0.3x=0.3 , 0.5, and 0.7) using the self-combustion reaction in solutions containing metal nitrates and sucrose. The nanoparticles of these materials were obtained by further annealing of the as-prepared product in air at 700°C700°C for 1 h and submicrometric particles were obtained by further annealing at 900°C900°C for 22 h. The effect of composition on the electrochemical performance was explored in this work. By a rigorous study with high resolution transmission electron microscopy (HRTEM), it became clear that the syntheses with the above stoichiometries produce two-phase materials comprising nanodomains of both rhombohedral LiNiO2LiNiO2 -like and monoclinic Li2MnO3Li2MnO3 structures, which are closely integrated and interconnected with one another at the atomic level. Stable reversible capacities ∼220mAh/g∼220mAh/g were obtained with composite electrodes containing submicrometer particles of 0.5Li2MnO3⋅0.5LiMn1/3Ni1/3Co1/3O20.5Li2MnO3⋅0.5LiMn1/3Ni1/3Co1/3O2 . Structural aspects, activation of the monoclinic component, and stabilization mechanisms are thoroughly discussed using Raman spectroscopy, solid-state NMR, HRTEM, and X-ray diffraction (including Rietveld analysis) in conjunction with electrochemical measurements. This work provides a further indication that this family of integrated compounds contains the most promising cathode materials for high energy density Li-ion batteries.