P2-type transition metal layered oxides (TMOs) have gathered significant interest by virtue of their low-cost and excellent cycling stability. However, the extensive practical application of TMOs is constrained by inherent factors, such as inferior rate performance and deficient interfacial stability. Herein, the gradient Ta-doped Na0.78(Ni0.33Mn0.67)1-xTaxO2 (NMT) cathode material was synthesized via a one-step solid-state reaction method to overcome these obstacles. The Ta modification augments the Ni2+/Ni3+ redox couple activity, in accordance with the principle of charge conservation, thus bolstering the reversible capacity of the material. Furthermore, the gradient Ta-doping not only preserves the stability of the bulk phase of TMOs but also serves as a potent suppression against the emergence of deleterious interfacial side reactions. As a result, the NMT cathode delivers an improving initial discharge specific capacity of 105 mAh g−1 at 0.1 C and sustains an excellent capacity retention of 91.4 % after 500 cycles at 5 C within the voltage range of 2.0–4.0 V. Benefiting from the robust Ta–O bond, the highly reversible structure evolution of the gradient Ta-doped material during the Na+ extraction/insertion process is clearly elucidated through in-situ XRD. This research provides a straightforward and efficacious approach to elevate the electrochemical performance of TMOs for sodium-ion batteries (SIBs) in the future.

中文翻译：

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通过梯度钽掺杂增强 Ni2+/Ni3+ 氧化还原对的活化，以获得高比容量和出色的界面稳定性


P2 型过渡金属层状氧化物 （TMO） 因其低成本和出色的循环稳定性而受到广泛关注。然而，TMO 的广泛实际应用受到固有因素的限制，例如较差的速率性能和界面稳定性不足。本文通过一步固态反应法合成了梯度 Ta 掺杂 Na0.78（Ni0.33Mn0.67）1-xTaxO2 （NMT） 正极材料，以克服这些障碍。根据电荷守恒原理，Ta 改性增强了 Ni2+/Ni3+ 氧化还原对活性，从而增强了材料的可逆能力。此外，梯度 Ta 掺杂不仅保持了 TMO 本相的稳定性，而且还有效抑制了有害界面副反应的出现。因此，NMT 阴极在 0.1 C 时的初始放电比容量为 105 mAh g-1，并在 2.0–4.0 V 的电压范围内在 5 C 下循环 500 次后仍能保持 91.4% 的出色容量保持率。得益于强大的 Ta-O 键，梯度 Ta 掺杂材料在 Na+ 提取/插入过程中的高度可逆结构演变通过原位 XRD 清晰地阐明了。这项研究提供了一种简单有效的方法，以在未来提高钠离子电池 （SIB） TMO 的电化学性能。