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

For the first time, atomic layer deposition (ALD) of Al2O3 was adopted to enhance the cyclic stability of layered P2-type Na-2/3(Mn0.54Ni0.13Co0.13)O-2 (MNC) cathodes for use in sodium-ion batteries (SIBs). Discharge capacities of approximately 120, 123, 113, and 105 mAhg(-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 1m 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 (E-g= 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.