Hard carbon as a typical anode material for sodium ion batteries has received much attention in terms of its low cost and renewability. Herein, phosphorus‐functionalized hard carbon with a specific “honeycomb briquette” shaped morphology is synthesized via electrospinning technology. When applied as an anode material for Na⁺ storage, it exhibits an impressively high reversible capacity of 393.4 mA h g⁻¹ with the capacity retention up to 98.2% after 100 cycles. According to first‐principle calculation, the ultrahigh capacity of the as‐prepared anode is ascribed to the enhancement of Na‐absorption through formation of PO and PC bonds in graphitic layers when doped with phosphorus. Moreover, the increase of electron density around the Fermi level is found to be mainly caused by O atoms instead of P atoms.

中文翻译：

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深入了解磷功能化硬碳作为超高容量阳极的Na +储存机理

就其低成本和可再生性而言，作为钠离子电池典型阳极材料的硬碳已受到广泛关注。在此，通过静电纺丝技术合成了具有特定“蜂窝煤块”形形态的磷官能化硬碳。当用作Na ⁺储存的阳极材料时，它表现出令人印象深刻的393.4 mA hg ^-1的高可逆容量，在100次循环后容量保持率高达98.2％。根据第一原理计算，所制备的阳极的超高容量是通过形成PO和P的归因于钠吸收的增强掺杂磷时，石墨层中的C键。此外，发现费米能级附近的电子密度增加主要是由O原子而不是P原子引起的。