Electrochemical effects of annealing on atomic layer deposited AL2O3 coatings on LiNi0.5Mn0.3Co0.2O2

This study investigated the annealing of atomic layer deposited (ALD) Al2O3 coated onto Li-ion battery cathodes to enhance their electrochemical properties. LiNi0.5Mn0.3Co0.2O2 (NMC) cathode powders were coated with 5 ALD cycles at 100 degrees C, annealed between 300 and 700 degrees C, cast into electrode sheets and assembled into coin cells. Cells were characterized using charge-discharge cycling, electrochemical impedance spectroscopy, pre-casting and postmortem X-ray photoelectron spectroscopy, and charge endpoint 'slippage measurement. Diffusion of Al into bulk NMC was observable at >500 degrees C, and extent of diffusion increased with increasing temperature. Un-annealed ALD-coated cathodes showed exceptional capacity retention at high charge-discharge rates, while annealed cells showed recovery of initial charge capacity lost upon ALD coating. High quantities of LiF forming surface species were detected in cells annealed at 500 degrees C. This study approaches post-deposition annealing as a parameter that may be used to explore the electrochemical properties of ALD-coated battery cathodes. (C) 2017 Elsevier B.V. All rights reserved.