Manganese-based layered oxides with anionic redox activity are considered as one of the most promising cathode candidates for sodium-ion batteries (SIBs) owing to their abundant resources and high theoretical specific capacities. However, the severe Jahn-Teller (J-T) effect of Mn and irreversible lattice oxygen loss result in rapid structural degradation and electrochemical performance deterioration. Herein, the functioning mechanism of F-doping in regulating the local and electronic structures of Mn-based layered oxides is unraveled. The introduction of the more electronegative F ions on one hand breaks the electronic symmetry of the MnO octahedra and effectively alleviates the J-T distortion, on the other hand suppresses the Zn ions migration through the strong Zn-F bonds and stabilizes the oxygen redox chemistry and facilitates the Na diffusion. The above reaction mechanisms are systematically validated by in-situ/ex-situ analyses and theoretical computations. As a result, the optimum P2-NaZnMnOF cathode demonstrates significantly improved rate capability (178.6 mAh g at 0.1 C with 64.4 mAh g at 10 C) and enhanced cycling durability (83.1 % capacity retention over 400 cycles at 3 C) compared to the un-doped P2-NaZnMnO material. This study clarifies the F-doping mechanism in layered oxides and provides new perspectives for designing high-energy and high-stability cathodes for SIBs.

中文翻译：

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揭示锰基层状氧化物阴极中氟掺杂增强钠离子存储性能的作用机制

具有阴离子氧化还原活性的锰基层状氧化物由于其丰富的资源和较高的理论比容量而被认为是钠离子电池（SIB）最有前途的正极候选材料之一。然而，Mn的严重Jahn-Teller（JT）效应和不可逆晶格氧损失导致结构快速退化和电化学性能恶化。在此，揭示了氟掺杂在调节锰基层状氧化物的局域和电子结构中的作用机制。电负性更强的F离子的引入一方面打破了MnO八面体的电子对称性，有效缓解了JT畸变，另一方面抑制了Zn离子通过强Zn-F键的迁移，稳定了氧的氧化还原化学，促进了Na扩散。上述反应机理通过原位/异位分析和理论计算得到系统验证。因此，与未使用的 P2-NaZnMnOF 正极相比，最佳的 P2-NaZnMnOF 正极表现出显着提高的倍率性能（0.1 C 时为 178.6 mAh g，10 C 时为 64.4 mAh g）和增强的循环耐久性（3 C 下 400 次循环后容量保持率为 83.1%）。掺杂P2-NaZnMnO材料。这项研究阐明了层状氧化物中的氟掺杂机制，为设计高能、高稳定性的SIB阴极提供了新的视角。