Structure, and magnetic and electrochemical properties of layered oxides, Li2IrO3

The layered oxide Li2IrO3 was synthesized and characterized by X-ray Rietveld analysis, and magnetic and electrochemical measurements. Li2IrO3 has a monoclinic cell similar to the Li2RuO3 structure. X-Ray Rietveld analysis showed that Li2IrO3 has a layered structure with different cation layers (Li only layers and layers of a mixture of Li and Ir) stacking alternately along the c axis and Ir hexagonal networks in successive LiIr2 layers. In addition, it was shown that the degree (g) of formation of the Ir hexagonal network depended on the synthesis conditions and was close to complete Ir hexagonal at higher synthesis temperatures. Magnetic measurements showed that Li2IrO3 (g = 0.92) was antiferromagnetic with T-N = 15 K. Lithium deintercalation from Li2IrO3 (g = 0.94) proceeded from monoclinic symmetry (Li2IrO3) to cubic (Li0.5IrO3) through orthorhombic symmetry (Li1.0IrO3). Electrochemical tests clarified that the Li/Li2IrO3 (g = 0.87) cell showed better cycling performance compared with the Li/Li(2)IrO3 (g = 0.94) cells. The Li/Li2IrO3 (g = 0.87) cells showed cycling capacities of 135 and 100 mA h g(-1) in the voltage range of 3.0-4.4 V and 3.0-4.2 V, respectively, and showed excellent cycling performance in the voltage range of 3.0-4.2 V.