Improving the Comprehensive Performance of Na0.7MnO2 for Sodium Ion Batteries by ZrO2 Atomic Layer Deposition.

Sodium ion batteries with Na-Mn-O compounds as cathodes have been widely studied as substitutes for lithium ion batteries due to their abundant resources. However, the relatively poor cycling stability and low capacity of Na-Mn-O compounds significantly limit their applications. Different approaches, including element substitution and surface modification, have been applied to improve the electrochemical performance of those cathode materials. Herein, element doping and coating of ZrO2 on Na0.7MnO2 particles have been achieved by atomic layer deposition followed by post-annealing. The rate capability and cycling stability of the modified materials were significantly improved, and the mechanism of performance enhancement was revealed. The ZrO2 coatings acted as a stable interfacial layer to enhance the cycling stability of Na0.7MnO2 by suppressing side reactions between the electrode and electrolyte. The doping of transition metal ions reduced energy barriers for sodium ion insertion and deintercalation during charge/discharge cycling, further improving the charge/discharge capacity and rate performance of Na0.7MnO2.