Cobalt-free NaNi_1/3Fe_1/3Mn_1/3O₂ is considered as one of the most promising cathode materials for sodium-ion batteries due to its high specific capacity, low cost and facile synthesis method. However, its electrochemical performance deteriorates rapidly due to serious structural degradation in the charge–discharge process, and it is difficult to store O3-type layered oxides in air, which seriously affects its commercialization process. Therefore, in this work, the yttrium element was used to partially substitute the NaNi_1/3Fe_1/3Mn_1/3O₂ material to achieve microscopic modulation of the crystal structure. The strong Y–O bond can stabilize the crystal structure, inhibit the slipping of the transition metal layer, and prevent the occurrence of an irreversible phase transition, thus improving the cycling performance of the material. At the same time, the sodium-ion diffusion layer expands with the introduction of Y, and the sodium-ion diffusion coefficient and rate capability of the material are significantly enhanced. In addition, Y³⁺ substitution reduces the ratio of Mn³⁺/Mn⁴⁺ in the material, mitigating the Jahn–Teller effect, which is another important factor for increasing the stability of the layered structure. Moreover, even after storing NaNi_1/3Fe_1/3−0.01Mn_1/3Y_0.01O₂ in air for 7 days, its crystal structure did not undergo significant changes, indicating a substantial improvement of air stability compared to the pristine material of NaNi_1/3Fe_1/3Mn_1/3O₂.

中文翻译：

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一种高倍率空气稳定性钠离子电池正极材料：钇取代O3型Ni/Fe/Mn基层状氧化物


无钴NaNi _1/3 Fe _1/3 Mn _1/3 O ₂ 被认为是最有前途的钠离子电池正极材料之一由于其比容量高、成本低且合成方法简便。然而，由于充放电过程中严重的结构降解，其电化学性能迅速恶化，并且难以在空气中储存O3型层状氧化物，严重影响了其商业化进程。因此，本工作采用钇元素部分替代NaNi _1/3 Fe _1/3 Mn _1/3 O ₂ 材料来实现晶体结构的微观调控。强的Y-O键可以稳定晶体结构，抑制过渡金属层的滑移，防止不可逆相变的发生，从而提高材料的循环性能。同时，钠离子扩散层随着Y的引入而扩大，材料的钠离子扩散系数和倍率能力显着增强。此外，Y ³⁺ 取代降低了材料中 Mn ³⁺ /Mn ⁴⁺ 的比率，减轻了 Jahn-Teller 效应，这是材料中的另一个重要因素。增加层状结构的稳定性。另外，即使将NaNi _1/3 Fe _1/3−0.01 Mn _1/3 Y _0.01 O ₂ 在空气中保存7天后，其晶体结构没有发生明显变化，表明与原始材料NaNi _1/3 Fe _1/3 Mn _1/3 O 。