Na₄MnV(PO₄)₃ (NMVP) has emerged as a cost-effective alternative to Na₃V₂(PO₄)₃, which is considered a promising cathode material for sodium-ion batteries. However, challenges such as low electronic conductivity, fast capacity fading resulting from the dissolution of Mn and polarization due to irreversible structural transformation impede the widespread application of NMVP. In this study, a facile sol–gel method is employed to dope NMVP with Mo, aiming to address these limitations. Synchrotron extended X-ray absorption fine structure data, neutron powder diffraction results, and density functional theory (DFT) calculations indicate a preferential occupation of the P site by Mo. Mo-doped NMVP demonstrates an outstanding discharge capacity of 97.5 mA h g⁻¹ at 0.2C and 46.4 mA h g⁻¹ at 20C, along with impressive long-term stability, retaining 78.8% capacity after 300 cycles at 1C. DFT calculations reveal a significant reduction in the band gap of Mo-doped NMVP, enhancing electronic conductivity and thereby improving rate capability retention. In operando X-ray absorption spectroscopy reveals changes in the valence of V, Mn, and Mo in the material during charge/discharge, confirming the complete reversibility of redox reactions. The outstanding performance of the novel Mo-doped NMVP cathode highlights its promising potential for application in large-scale energy storage systems.

中文翻译：

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通过调整 NASICON 框架实现高性能和高倍率能力的 Na4MnV（PO4）3 钠离子电池阴极


Na₄MnV（PO₄）₃ （NMVP） 已成为 Na 3 V 2（PO 4）3 的一种经济高效的替代品，Na₃V₂（PO₄）₃ 被认为是一种很有前途的钠离子电池正极材料。然而，低电子电导率、Mn 溶解导致的快速容量衰减以及不可逆结构转变导致的极化等挑战阻碍了 NMVP 的广泛应用。在这项研究中，采用一种简单的溶胶-凝胶方法用 Mo 掺杂 NMVP，旨在解决这些限制。同步加速器扩展 X 射线吸收精细结构数据、中子粉末衍射结果和密度泛函理论 （DFT） 计算表明 Mo 优先占据 P 位。Mo 掺杂 NMVP 在 0.2C 时表现出 97.5 mA h ^g-1 的出色放电容量，在 20C 时为 46.4 mA h ^g-1，以及令人印象深刻的长期稳定性，在 1C 下循环 300 次后仍保持 78.8% 的容量。Mo 掺杂 NMVP 的带隙，增强了电子电导率，从而提高了倍率能力保持。In operandoX 射线吸收光谱揭示了材料在充电/放电过程中 V、Mn 和 Mo 的价态变化，证实了氧化还原反应的完全可逆性。新型 Mo 掺杂 NMVP 阴极的出色性能凸显了其在大规模储能系统中的应用潜力。