Structural and Electrochemical Study of Al₂O₃ and TiO₂ Coated Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ Cathode Material Using ALD

Abstract

Abstract Nanolayers of Al 2 O 3 and TiO 2 coatings were applied to lithium‐ and manganese‐rich cathode powder Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 using an atomic layer deposition (ALD) method. The ALD coatings exhibited different surface morphologies; the Al 2 O 3 surface film appeared to be uniform and conformal, while the TiO 2 layers appeared as particulates across the material surface. In a Li‐cell, the Al 2 O 3 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 x TiO 2 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 TiO 2 film, which led to degradation in cell performance, particularly at high temperature. For cells comprised of the coated Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 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 Al 2 O 3 or TiO 2 can address some of the capacity fading issues related to the Li‐rich cathode at room temperature.