One-Step Sintering Coating toward Air-Stable O3-Type Layered Oxide Cathodes for Sodium-Ion Batteries

Layered oxides are one of the most promising cathode materials for sodium-ion batteries due to their high theoretical capacity, high voltage platform, and low manufacturing cost. However, the poor air stability severely limits the practical application of the O3-type layered oxide. In this study, a simple one-step sintering coating method is explored to construct a uniform and dense heavy metal oxide (Sb₂O₃) coating layer on Na(Ni_1/3Fe_1/3Mn_1/3)O₂ (NFM333), and the coating layer effectively improved the air stability of NFM333 by mitigating the contact of H₂O and CO₂ in the air. Consequently, NFM333-0.5 wt % Sb₂O₃ obtains a specific capacity of 92.1 mAh g^-1 with a capacity retention of 84.6% after 200 cycles at 1C after exposure in air with 60% humidity for 2 days, while NFM333 without a coating layer has a specific capacity of just 85.4 mAh g^-1 with a capacity retention of 65.3% after 200 cycles at 1C after the same exposure handling. This study presents a facile coating method to improve the air stability of O3-type NFM33, which provides insights for the development of air-stable NFM333.