Excellent Electrochemical\nPerformance and Air Storage\nStability of Na-Ion Layered Oxide Cathodes Benefiting from Enhanced\nCe–O Binding Energy

The widespread application of layered oxides is constrained\nby\ntheir low electrochemical performance and complex irreversible phase\ntransition. The high entropy oxide NaNi<sub>0.25</sub>Fe<sub>0.15</sub>Mn<sub>0.3</sub>Ti<sub>0.1</sub>Sn<sub>0.05</sub>Co<sub>0.05</sub>Li<sub>0.1</sub>O<sub>2</sub> (HEO) is synthesized by leveraging\nthe entropy stabilization effect, which offers a partial solution\nto this issue, but electrochemical performance and air stability imperative\nto be improved. On the high entropy oxide HEO, due to the strong bond\nenergy of Ce–O, the introduction of Ce<sup>4+</sup> improves\nthe specific discharge capacity and reduces the battery gas production\nproblem. It also improves the air stability. NaNi<sub>0.25</sub>Fe<sub>0.15</sub>Mn<sub>0.3</sub>Ti<sub>0.1</sub>Sn<sub>0.03</sub>Ce<sub>0.02</sub>Co<sub>0.05</sub>Li<sub>0.1</sub>O<sub>2</sub> (HEO-Ce2)\ndemonstrated a specific discharge capacity of 160 mA h g<sup>–1</sup> at 0.1 C. The discharge-specific capacity retention rate of the\nmaterial is 86%, after air exposure for 10 days. The high entropy\neffect and introduction of Ce<sup>4+</sup> provide a viewpoint for\na layered oxide of sodium-ion batteries.