Highly Stable Na2/3(Mn0.54Ni0.13Co0.13)O2 Cathode Modified by Atomic Layer Deposition for Sodium‐Ion Batteries

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Abstract
For the first time, atomic layer deposition (ALD) of Al2O3 was adopted to enhance the cyclic stability of layered P2‐type Na2/3(Mn0.54Ni0.13Co0.13)O2 (MNC) cathodes for use in sodium‐ion batteries (SIBs). Discharge capacities of approximately 120, 123, 113, and 105 mA h g−1 were obtained for the pristine electrode and electrodes coated with 2, 5, and 10 ALD cycles, respectively. All electrodes were cycled at the 1C discharge current rate for voltages between 2 and 4.5 V in 1 M NaClO4 electrolyte. Among the electrodes tested, the Al2O3 coating from 2 ALD cycles (MNC‐2) exhibited the best electrochemical stability and rate capability, whereas the electrode coated by 10 ALD cycles (MNC‐10) displayed the highest columbic efficiency (CE), which exceeded 97 % after 100 cycles. The enhanced electrochemical stability observed for ALD‐coated electrodes could be a result of the protection effects and high band‐gap energy (Eg=9.00 eV) of the Al2O3 coating layer. Additionally, the metal‐oxide coating provides structural stability against mechanical stresses occurring during the cycling process. The capacity, cyclic stability, and rate performance achieved for the MNC electrode coated with 2 ALD cycles of Al2O3 reveal the best results for SIBs. This study provides a promising route toward increasing the stability and CE of electrode materials for SIB application.
Funding Information
  • Nature Sciences and Engineering Research Council of Canada (NSERC)
  • Canada Research Chair (CRC) Program
  • Canada Foundation for Innovation (CFI)
  • Ontario Research Fund (ORF)
  • Canadian Centre for Electron Microscopy (CCEM) at McMaster University
  • University of Western Ontario

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