Dependence of properties, crystal structure and electrode characteristics on Li content for LixCo1/3Ni1/3Mn1/3O2+δ as a cathode active material for Li secondary battery

We investigated the dependence of the properties, crystal structure and electrode characteristics on the Li content of LixCo1/3Ni1/3Mn1/3O2+delta. The crystal structure was determined by Rietveld analysis using neutron diffraction. The electron density images were determined by X-ray diffraction, Rietveld analysis and Maximum Entropy Method. The cycle performance was slightly lower, but the discharge capacity increased at x = 1.122. From the crystal structure analysis, the amount of cation mixing was changed by the Li content, that is, a small amount of Ni2+ ions is present in the lithium layers (3a) and extra Li is located in transition metal layer (3b). Ni2+ ions occupied about 4% of the 3a site and Li is located in the 3b site at 0.915 <= x <= 1.052. On the other hand, Ni2+ ions occupied about 1.2% of the 3a site for x = 1.122. In other words, 12% of the total amount of Ni existed in the 3a site at 0.915 <= x <= 1.052, but, 3.8% of the total amount of Ni existed in the 3a site for x = 1.122. The bond length between 3b and 6c (oxygen site) increased with the increasing Li content. From the results, the discharge capacity increased with the decreasing Ni in the 3a site.