Na3(VO)2(PO4)2F cathode has garnered extensive interest for its stable structure, abundant Na+ migration channels, and high working voltage, though higher energy densities are sought for commercial applications. This study enhances energy density by activating multi-electron reactions through the partial substitution of V4+ and dangling O2− with Fe3+ and F⁻, respectively, using a straightforward hydrothermal method. This substitution successfully activates the V3+/V4+ redox couple, facilitating multi-electron reactions. The modified cathode, Na₃(VO)1.8Fe0.2(PO4)2F1.2 (N(VO)1.8Fe0.2PF1.2), exhibits a reversible specific capacity of 213.3 mAh g−1 at 50 mA g−1. Characterization techniques, including in situ X-ray diffraction and ex-situ X-ray photoelectron spectroscopy, confirm that the activated V3+/V4+ redox reaction proceeds via a solid-solution mechanism. Density functional theory analysis suggests that Na3(VO)1.8Fe0.2(PO4)2F1.2 offers improved electronic conductivity and structural stability, elucidating the origins of low Na+ migration energy barriers and ideal diffusion kinetics. When paired with a hard carbon (HC) anode, the full cell (HC//N(VO)1.8Fe0.2PF1.2) achieves a reversible capacity of 196.6 mAh g−1 and an energy density of 287.0 Wh kg−1 at 50 mA g−1, demonstrating exceptional long-term cyclic stability with a capacity retention of 94.7% after 200 cycles at 500 mA g−1. This study opens new avenues for the commercial application of sodium-ion batteries (SIBs) cathodes.

中文翻译：

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通过 Fe/F 双掺杂激活 Na3（VO）2（PO4）2F 阴极的可逆多电子反应，实现高能和稳定的钠储存


Na3（VO）2（PO4）2F 阴极因其稳定的结构、丰富的 Na+ 迁移通道和高工作电压而引起了广泛的兴趣，尽管商业应用寻求更高的能量密度。本研究使用简单的水热方法，通过分别用 Fe3+ 和 F⁻ 部分取代 V4+ 和悬空的 O2− 来激活多电子反应，从而提高能量密度。这种取代成功激活了 V3+/V4+ 氧化还原对，促进了多电子反应。改性阴极 Na₃（VO）1.8Fe0.2（PO4）2F1.2 （N（VO）1.8Fe0.2PF1.2） 在 50 mA g-1 时表现出 213.3 mAh g-1 的可逆比容量。表征技术，包括原位 X 射线衍射和非原位 X 射线光电子能谱，证实活化的 V3+/V4+ 氧化还原反应通过固溶机制进行。密度泛函理论分析表明，Na3（VO）1.8Fe0.2（PO4）2F1.2 具有更好的电子电导率和结构稳定性，阐明了低 Na+ 迁移能垒和理想扩散动力学的起源。当与硬碳 （HC） 阳极配对时，全电池 （HC//N（VO）1.8Fe0.2PF1.2） 在 50 mA g-1 时可实现 196.6 mAh g-1 的可逆容量和 287.0 Wh kg-1 的能量密度，表现出卓越的长期循环稳定性，在 500 mA g-1 下循环 200 次后容量保持率为 94.7%。本研究为钠离子电池 （SIB） 阴极的商业应用开辟了新的途径。