The Air Stability of Sodium Layered Oxide Cathodes

Sodium-ion batteries (NIBs) are listed as one of the ideal alternatives for lithium-ion batteries (LIBs), due to the abundant sodium resources, cost-effective electrode materials of NIBs, and same architecture of NIBs to LIBs. To enable the practical implementation of NIBs, advanced cathodes with higher energy/power densities, better safety and cycle life, as well as lower cost are required. Layered lithium transition metal oxides (LiTMO 2 ) are one of the most successful cathode materials for commercial LIBs. Similarly, layered sodium transition metal oxides (Na x TMO 2 , also termed as sodium layered oxides) are of particular interest for commercial NIBs owing to their high specific capacity, a wide variety of redox-active elements, and the possibility for the manufacturers to employ established synthesis processes as their lithium counterparts. Sodium layered oxides are built up by ordered stacking of alternate alkali-metal (Na + ) layers and transition metal layers (TmO 2 ). The two-dimensional structure makes them the natural hosts for alkali-metal ions and other ions or small molecules, such as H 2 O. Therefore, when exposed to moist atmospheres, layered oxide materials tend to react with H 2 O which adsorbed on their surface and thus deteriorate their structure and electrochemical performances. Accordingly, the air-sensitive sodium layered oxides should be well protected from the moist atmospheres, rendering a higher manufacturing and preservation cost. Here, based on the reaction mechanisms, critical influencing factors, and modification methods of layered oxides in moisture, we try to reach a comprehensive understanding of the air-stability of sodium layered oxides. Moreover, future efforts to resolve the air-stability of sodium layered oxides from Argonne National Laboratory will be also presented. References 1. Han, M. H.; Gonzalo, E.; Singh, G.; Rojo, T. A comprehensive review of sodium layered oxides: powerful cathodes for Na-ion batteries. Energy Environ. Sci. 2015 , 8 , 81-102. 2. Zuo, W.; Qiu, J.; Liu, X.; Ren, F.; Liu, H.; He, H.; Luo, C.; Li, J.; Ortiz, G. F.; Duan, H.; Liu, J.; Wang, M. S.; Li, Y.; Fu, R.; Yang, Y. The stability of P2-layered sodium transition metal oxides in ambient atmospheres. Commun. 2020 , 11 , 3544. 3. Xu, G. L.; Liu, X.; Zhou, X.; Zhao, C.; Hwang, I.; Daali, A.; Yang, Z.; Ren, Y.; Sun, C. J.; Chen, Z.; Liu, Y.; Amine, K. Native lattice strain induced structural earthquake in sodium layered oxide cathodes. Commun. 2022 , 13 , 436. 4. Zuo, W.; Xiao, Z.; Zarrabeitia, M.; Xue, X.; Yang, Y.; Passerini, S. Guidelines for Air-Stable Lithium/Sodium Layered Oxide Cathodes. ACS Materials Letters 2022 , 4 , 1074-1086. 5. Fu, F.; Liu, X.; Fu, X.; Chen, H.; Huang, L.; Fan, J.; Le, J.; Wang, Q.; Yang, W.; Ren, Y.; Amine, K.; Sun, S. G.; Xu, G. L. Entropy and crystal-facet modulation of P2-type layered cathodes for long-lasting sodium-based batteries. Commun. 2022 , 13 , 2826.