Minimum Co content limit in layer-structured cathode materials for Li-ion batteries

초록

Research to decrease the Co content in layer-structured cathode materials for Li-ion batteries is ongoing to increase the battery capacity and decrease the cost of material by increasing the relative Ni content. However, no clear guidance has yet been provided on the minimum possible Co content. In this study, energetically stable structures of delithiated cathodes are investigated, and a complete crystal structure is modeled as a combination of these structures. By the statistical processing of Co distribution within the model crystal, as well as considering the interfacial energy between differently structured domains induced by stacking faults of the O layers, the lower limit for the Co content is calculated. The result indicates that a minimum of 10.2% Co is necessary to prevent degradation of the crystal structure. For further reduction of the Co content, the Co distribution must be concentrated in certain regions of the crystal, which can be achieved by doping with a small amount of a third element. In this manner, the Co content could be ideally reduced to 4.17%.

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