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Abstract：
Iron/manganese-based layered transition metal oxides have risen to prominence as prospective cathodes for sodium-ion batteries (SIBs) owing to their abundant resources and high theoretical specific capacities, yet they still suffer from rapid capacity fading. Herein, a dual-strategy is developed to boost the Na-storage performance of the Fe/Mn-based layered oxide cathode by copper (Cu) doping and nanoengineering. The P2-Na0.76Cu0.22Fe0.30Mn0.48O2 cathode material synthesized by electrospinning exhibits the pearl necklace-like hierarchical nanostructures assembled by nanograins with sizes of 50-150 nm. The synergistic effects of Cu doping and nanotechnology enable high Na+ coefficients and low ionic migration energy barrier, as well as highly reversible structure evolution and Cu/Fe/Mn valence variation upon repeated sodium insertion/extraction; thus, the P2-Na0.76Cu0.22Fe0.30Mn0.48O2 nano-necklaces yield fabulous rate capability (125.4 mA h g-1 at 0.1 C with 56.5 mA h g-1 at 20 C) and excellent cyclic stability (≈79% capacity retention after 300 cycles). Additionally, a promising energy density of 177.4 Wh kg-1 is demonstrated in a prototype soft-package Na-ion full battery constructed by the tailored nano-necklaces cathode and hard carbon anode. This work symbolizes a step forward in the development of Fe/Mn-based layered oxides as high-performance cathodes for SIBs.
摘要：
铁/锰基层状过渡金属氧化物由于其丰富的资源和较高的理论比容量，已成为钠离子电池（SIB）的潜在阴极，然而，他们仍然遭受容量迅速下降的困扰。在这里，开发了一种双重策略，通过铜（Cu）掺杂和纳米工程来提高基于Fe/Mn的层状氧化物阴极的Na存储性能。通过静电纺丝合成的P2-Na0.76Cu0.22Fe0.30Mn0.48O2阴极材料表现出由尺寸为50-150nm的纳米晶粒组装的珍珠项链状分层纳米结构。Cu掺杂和纳米技术的协同作用使得高Na+系数和低离子迁移能垒,以及在反复插入/提取钠时高度可逆的结构演变和Cu/Fe/Mn化合价变化；因此，P2-Na0.76Cu0.22Fe0.30Mn0.48O2纳米项链具有出色的倍率性能（0.1C时为125.4mAhg-1，20C时为56.5mAhg-1）和出色的循环稳定性（300次循环后约79%的容量保持率）。此外,在由定制的纳米项链阴极和硬碳阳极构造的原型软包装Na离子全电池中，证明了有希望的能量密度为177.4Whkg-1。这项工作标志着Fe/Mn基层状氧化物作为SIBs高性能阴极的开发迈出了一步。
