The amorphous ZnO particles encapsulated in porous nitrogen-doped carbon nanofibers (ZnO@PN-CNFs) are synthesized by electrospinning process and heat treatment. The enhanced electrochemical properties of ZnO@PN-CNFs are based on the porous nanostructure, high length/diameter (L/D) ratio, doped nitrogen, and uniform distributed amorphous ZnO nanoparticles. The results show amorphous ZnO particles in carbon nanofibers avoid the pulverization and alleviated the volume expansion, as well as make the cycling of the anode quickly reach stable. Furthermore, the nitrogen-doped carbon improves electron conductivity while one-dimensional (1D) nanofibers with high L/D ratio own a short diffusion path and high electronic transportation efficiency along the longitudinal direction. Meanwhile, the porous nanostructure from urea pyrolysis produces thinner wall and further shortens the ionic transport distance. Therefore, high capacity and long-cycling life are achieved. And the ZnO@PN-CNF electrode shows a high discharge capacity (1073.2 mAh g⁻¹ at 0.1 A⁻¹) after 100 cycles. Moreover, the ZnO@PN-CNF electrode presents a high discharge capacity of 703.1 mAh g⁻¹ even at 1 A⁻¹ after 400 cycles. In this work, urea not only stops the ZnO from crystallization, leading to uniform distributed amorphous small ZnO particles, but also makes numerous pores in the carbon nanofibers, enlarging the touching area with electrolyte and shortening the transport distance to ZnO particles. It is a promising way by adding urea to alleviate volume expansion and pulverization of the crystal particles and then enhance the performance of electrode.

中文翻译：

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封装在碳纳米纤维中的ZnO作为锂离子电池负极材料的增强电化学性能

通过电纺丝工艺和热处理合成了包埋在多孔氮掺杂碳纳米纤维（ZnO @ PN-CNFs）中的非晶态ZnO颗粒。ZnO @ PN-CNFs增强的电化学性能是基于多孔纳米结构，高长径比（L / D），掺杂氮和均匀分布的无定形ZnO纳米粒子。结果表明，碳纳米纤维中的无定形ZnO颗粒避免了粉化，减小了体积膨胀，并使阳极的循环迅速达到稳定。此外，氮掺杂的碳改善了电子传导性，而具有高L / D比的一维（1D）纳米纤维具有短的扩散路径和沿纵向的高电子传输效率。与此同时，尿素热解产生的多孔纳米结构产生更薄的壁，并进一步缩短了离子的传输距离。因此，实现了高容量和长循环寿命。ZnO @ PN-CNF电极显示出高放电容量（1073.2 mAh g在100个循环后于0.1 A ^-1时为^-1）。此外，即使在400次循环后在1 A ^-1下，ZnO @ PN-CNF电极也具有703.1 mAh g ^-1的高放电容量。在这项工作中，尿素不仅阻止了ZnO的结晶，导致均匀分布的无定形小的ZnO小颗粒，而且在碳纳米纤维中形成了许多孔，扩大了与电解质的接触面积，并缩短了向ZnO颗粒的传输距离。通过添加尿素以减轻晶体颗粒的体积膨胀和粉化然后增强电极性能是一种有前途的方法。