Engineering the surface of LiCoO₂ electrodes using atomic layer deposition for stable high-voltage lithium ion batteries

Developing advanced technologies to stabilize positive electrodes of lithium ion batteries under high-voltage operation is becoming increasingly important, owing to the potential to achieve substantially enhanced energy density for applications such as portable electronics and electrical vehicles. Here, we deposited chemically inert and ionically conductive LiAlO₂ interfacial layers on LiCoO₂ electrodes using the atomic layer deposition technique. During prolonged cycling at high-voltage, the LiAlO₂ coating not only prevented interfacial reactions between the LiCoO₂ electrode and electrolyte, as confirmed by electrochemical impedance spectroscopy and Raman characterizations, but also allowed lithium ions to freely diffuse into LiCoO₂ without sacrificing the power density. As a result, a capacity value close to 200 mA·h·g^–1 was achieved for the LiCoO₂ electrodes with commercial level loading densities, cycled at the cut-off potential of 4.6 V vs. Li⁺/Li for 50 stable cycles; this represents a 40% capacity gain, compared with the values obtained for commercial samples cycled at the cut-off potential of 4.2 V vs. Li⁺/Li.