Coating ultra-thin TiN layer onto LiNi0.8Co0.1Mn0.1O2 cathode material by atomic layer deposition for high-performance lithium-ion batteries

Highlights: • High conductive material TiN is deposited on the surface of Ni-rich NCM particles by atomic layer deposition (ALD). • The TiN coating layers which can be controlled precisely by ALD are able to improve the electrochemical performance of NCM811. • The TiN coating layer suppresses the structure and surface damage of active materials from the electrolyte during the battery cycling. -- Abstract: Layered structural LiNi_xCo_yMn_1−x-yO₂ (NCM, Ni ≥ 60%), as a competitive cathode material for high-energy density lithium-ion batteries, has been studied for a long time. However, the structural instability at high cut-off voltage and the erosion of the electrolyte by-product HF during the cycling can result in obvious capacity loss for bare NCM materials, which needs to be overcome for long charge mileage and safety of lithium-ion batteries. In this paper, an ultra-thin TiN film is deposited on the surface of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) particle by atomic layer deposition (ALD) to improve the electrochemical performance. The TiN coating layer was successfully found to hinder the side reaction and inhibit the damage of the structure during the cycling, reduce the contact resistance between the NCM811 particle and improve the electronic conductivity of the particle surface during the cycling. As a result, the TiN modified NCM811 cathode materials exhibit significantly improved cycling capacities and rate performance. The methodology in this study provides a new path to achieve thin layer surface modification to enhance the performance of electrode materials.