Highly Stable Na_2/3(Mn_0.54Ni_0.13Co_0.13)O₂ Cathode Modified by Atomic Layer Deposition for Sodium‐Ion Batteries

Abstract

For the first time, atomic layer deposition (ALD) of Al2 O3 was adopted to enhance the cyclic stability of layered P2-type Na2/3 (Mn0.54 Ni0.13 Co0.13 )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 Al2 O3 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 Al2 O3 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 Al2 O3 reveal the best results for SIBs. This study provides a promising route toward increasing the stability and CE of electrode materials for SIB application.

Enhanced Performance of P2‐Na0.66(Mn0.54Co0.13Ni0.13)O2 Cathode for Sodium‐Ion Batteries by Ultrathin Metal Oxide Coatings via Atomic Layer Deposition

“…Figure 1c illustrates the high-resolution transmission electron microscope (HR-TEM) image of 10 cycles of amorphous Al 2 O 3 coated MCN particles and the coating thickness can be measured as ≈1.5 nm with uniform deposition. [27,28,31] The presence of various metal oxide coating layers on the surface are further confirmed through X-ray photoelectron spectroscopy (XPS) analysis with the corresponding spectra given in Figure 2. [27,31] In addition, the uniformity of metal ions and coating material distribution on MNC powder was examined using energy-dispersive X-ray spectroscopy (EDX) and their corresponding EDX mapping are presented in Figures S2-S5 (Supporting Information).…”

“…[32,33] Conversely, the surface of MCN particles was found to become rough after deposition of metal oxides by ALD, as presented in Figure S1 (Supporting Information). [27,31] In addition, the uniformity of metal ions and coating material distribution on MNC powder was examined using energy-dispersive X-ray spectroscopy (EDX) and their corresponding EDX mapping are presented in Figures S2-S5 (Supporting Information). Figure 1c illustrates the high-resolution transmission electron microscope (HR-TEM) image of 10 cycles of amorphous Al 2 O 3 coated MCN particles and the coating thickness can be measured as ≈1.5 nm with uniform deposition.…”

“…[42,43] Hence, enhanced cyclic stability can be obtained from MCN-Al electrode. [27,31] Figure 3c illustrates the rate performance of the cells cycled at different current densities from 0.016 to 2.4 A g −1 within 2-4.5 V. It is well known that electrode material experiences high stress change during charge-discharge processes at high current densities. [39] Besides, metal oxide coating layer on the surface was provided a flexible structure against the mechanical strain and stress formed during the cycling process, which causes the poor electrochemical behavior.…”

“…[4,[23][24][25][26][27][28] Nevertheless, the effective application of ALD in RSB is limited. [25,26,30,31] In spite of increased structural stability from thicker coatings (5, 10, or 20 ALD cycles), increased thickness was found to hinder the active species from participating in the electrochemical reactions. [25,26,30,31] In spite of increased structural stability from thicker coatings (5, 10, or 20 ALD cycles), increased thickness was found to hinder the active species from participating in the electrochemical reactions.…”

“…The first report of Al 2 O 3 ALD deposition on a tin anode for RSB application was demonstrated by Han et al [29,30] Additionally, it was also reported by other groups that metal oxides coated with 2 ALD cycles were optimal for improving capacity and cyclic stability. [24,26,27,30,31] In this regard, different metal oxide coatings (Al 2 O 3 , ZrO 2 , and TiO 2 ) with 2 cycles of ALD was performed on the MCN electrode herein. [24,26,27,30,31] In this regard, different metal oxide coatings (Al 2 O 3 , ZrO 2 , and TiO 2 ) with 2 cycles of ALD was performed on the MCN electrode herein.…”