Phase transformation of LixNi1−yCoyO2 along with lithium deintercalation

A systematic investigation of the structural change of LixNi1−yCoyO2, a possible cathode material in lithium ion secondary battery, has been performed during lithium deintercalation. Three representative models, LiNiO2, LiCoO2 and LiNi0.8Co0.2O2, are constructed initially and then the molecular simulations according to the lithium content are performed using the modified universal force field. The phase transformations from rhombohedral to monoclinic and finally to rhombohedral have occurred for all three models by successively decreasing the lithium content. The ranges of lithium content where the phase transformation occurred agree well with the experimental results. This simple force field-based calculations are successfully applied to the structural changes including phase transformation of LixNi1−yCoyO2 system.