Efficacy of atomic layer deposition of Al 2 O 3 on composite LiNi 0.8 Mn 0.1 Co 0.1 O 2 electrode for Li-ion batteries.

LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) is a popular cathode material for Li-ion batteries, yet degradation and side reactions at the cathode-electrolyte interface pose significant challenges to their long-term cycling stability. Coating LiNi x Mn y Co 1-x-y O 2 (NMC) with refractory materials has been widely used to improve the stability of the cathode-electrolyte interface, but mixed results have been reported for Al 2 O 3 coatings of the Ni-rich NMC811 materials. To elucidate the role and effect of the Al 2 O 3 coating, we have coated commercial-grade NMC811 electrodes with Al 2 O 3 by the atomic layer deposition (ALD) technique. Through a systematic investigation of the long-term cycling stability at different upper cutoff voltages, the stability against ambient storage, the rate capability, and the charger transfer kinetics, our results show no significant differences between the Al 2 O 3 -coated and the bare (uncoated) electrodes. This highlights the contentious role of Al 2 O 3 coating on Ni-rich NMC cathodes and calls into question the benefits of coating on commercial-grade electrodes.