Poor migration dynamics and low energy density are the main challenges of Na3V2(PO4)3 as a cathode material for sodium ion batteries. Herein, a nanoscale polyhedron high-entropy cathode of Na3V1.47(Fe,Al,Ga,Mg,Mn)0.5Mo0.01Nb0.02(PO4)3 is designed to modify the crystal structure and enhance the electrons transfer. Distributed nanoparticles improve the electrolyte interface, promoting rapid migration of Na+, while the abundant specific surface area offers extra sites for Na+ storage. High entropy and multi-metal synergistic effects increase the number of occupied Na(1) and Na(2) sites, maintaining multiple redox couples (V3+/4+/5+ and Mn2+/3+/4+) and obtaining a reversible 2.18-electron reaction. Consequently, the high-entropy cathode of Na3V1.47(Fe,Al,Ga,Mg,Mn)0.5Mo0.01Nb0.02(PO4)3 delivers excellent specific capacity of 130.2 mAh g−1 at 0.5 C, achieving high energy density of 448.3 Wh kg−1, and exhibiting the capacity retention of 95 % after 500 cycles at 5 C and 86.5 % after 1000 cycles at 15 C, respectively. In situ XRD, ex situ XAS and DFT calculations reveal the influence of structural evolution, valence changes, and high-entropy effects on chemical kinetics. This study provides a guideline for designing advanced polyanionic phosphate cathode materials for sodium ion batteries.

中文翻译：

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解锁先进的钠储存性能：高熵通过可逆多电子反应调节晶体学位点


迁移动力学差和能量密度低是 Na3V2（PO4）3 作为钠离子电池正极材料的主要挑战。本文设计了Na3V1.47（Fe，Al，Ga，Mg，Mn）0.5Mo0.01Nb0.02（PO4）3的纳米多面体高熵阴极，以改变晶体结构并增强电子转移。分布式纳米颗粒改善了电解质界面，促进了 Na+ 的快速迁移，而丰富的比表面积为 Na+ 储存提供了额外的位点。高熵和多金属协同效应增加了占据的 Na（1） 和 Na（2） 位点的数量，维持了多个氧化还原对（V3+/4+/5+ 和 Mn2+/3+/4+）并获得可逆的 2.18 电子反应。因此，Na3V1.47（Fe，Al，Ga，Mg，Mn）0.5Mo0.01Nb0.02（PO4）3 的高熵阴极在 0.5 C 下提供 130.2 mAh g-1 的优异比容量，实现了 448.3 Wh kg-1 的高能量密度，在 5 C 下循环 500 次后表现出 95% 的容量保持率，在 15 C 下循环 1000 次后分别表现出 86.5% 的容量保持率。原位 XRD、非原位 XAS 和 DFT 计算揭示了结构演变、价态变化和高熵效应对化学动力学的影响。本研究为设计先进的钠离子电池用聚阴离子磷酸盐正极材料提供了指导。