Structural and electrochemical study of Al₂O₃ and TiO₂ Coated Li_1.2Ni_0.13Mn_0.54Co _0.13O₂ cathode material using ALD

Nanolayers of Al₂O₃ and TiO₂ coatings were applied to lithium- and manganese-rich cathode powder Li_1.2Ni _0.13Mn_0.54Co_0.13O₂ using an atomic layer deposition (ALD) method. The ALD coatings exhibited different surface morphologies; the Al₂O₃ surface film appeared to be uniform and conformal, while the TiO₂ layers appeared as particulates across the material surface. In a Li-cell, the Al₂O₃ surface film was stable during repeated charge and discharge, and this improved the cell cycling stability, despite a high surface impedance. The TiO ₂ layer was found to be more reactive with Li and formed a Li _xTiO₂ interface, which led to a slight increase in cell capacity. However, the repetitive insertion/extraction process for the Li ⁺ ions caused erosion of the surface protective TiO₂ film, which led to degradation in cell performance, particularly at high temperature. For cells comprised of the coated Li_1.2Ni_0.13Mn _0.54Co_0.13O₂ and an anode of meso-carbon-micro-beads (MCMB), the cycling stability introduced by ALD was not enough to overcome the electrochemical instability of MCMB graphite. Therefore, protection of the cathode materials by ALD Al₂O₃ or TiO₂ can address some of the capacity fading issues related to the Li-rich cathode at room temperature.