Air-Stable High-Entropy Layered Oxide Cathode with Enhanced Cycling Stability for Sodium-Ion Batteries.

Zhan, Jiajia; Huang, Jiawen; Li, Zhen; Yuan, Jujun; Dou, Shi-Xue; Liu, Hua-Kun; Wu, Chao · Nano Lett · 2024

basic_science · Level V

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Abstract

O3-type layered oxides have been extensively studied as cathode materials for sodium-ion batteries due to their high reversible capacity and high initial sodium content, but they suffer from complex phase transitions and an unstable structure during sodium intercalation/deintercalation. Herein, we synthesize a high-entropy O3-type layered transition metal oxide, NaNi<sub>0.3</sub>Cu<sub>0.05</sub>Fe<sub>0.1</sub>Mn<sub>0.3</sub>Mg<sub>0.05</sub>Ti<sub>0.2</sub>O<sub>2</sub> (NCFMMT), by simultaneously doping Cu, Mg, and Ti into its transition metal layers, which greatly increase structural entropy, thereby reducing formation energy and enhancing structural stability. The high-entropy NCFMMT cathode exhibits significantly improved cycling stability (capacity retention of 81.4% at 1C after 250 cycles and 86.8% at 5C after 500 cycles) compared to pristine NaNi<sub>0.3</sub>Fe<sub>0.4</sub>Mn<sub>0.3</sub>O<sub>2</sub> (71% after 100 cycles at 1C), as well as remarkable air stability. Finally, the NCFMMT//hard carbon full-cell batteries deliver a high initial capacity of 103 mAh g<sup>-1</sup> at 1C, with 83.8 mAh g<sup>-1</sup> maintained after 300 cycles (capacity retention of 81.4%).