碳纳米纤维储钠机制的原位透射电镜研究

碳纳米纤维储钠机制的原位透射电镜研究

皇甫磊磊，翟阿敏，田  鹤^*，张  泽

（ 浙江大学电子显微镜中心，硅材料国家重点实验室，材料科学与工程学院，浙江 杭州 310027）

摘  要  在钠离子电池负极材料的研究中，纳米管、纳米线和纳米纤维等一维纳米结构由于具有均匀的结构和良好的导电连接性，而被认为是一种高容量和稳定的电极材料，但在实际应用中其循环稳定性还有待进一步提高。研究发现采用静电纺丝法制备的碳纳米纤维却具有十分优异的循环稳定性。为了从微观结构上深层次地解释这一原因，本文采用原位透射电镜技术，对单根碳纳米纤维嵌钠过程进行了研究，并发现其体积膨胀率仅约为44.6%，且材料结构在嵌钠前后不发生明显变化，所以具有良好的循环稳定性。另外，实验中发现钠离子在碳纳米纤维中的嵌钠机制是由长程扩散控制的，为钠离子电池用碳纳米纤维的生产提供了指导意义。

关键词  钠离子电池负极材料；碳纳米纤维；原位透射电镜；嵌钠机制

中图分类号：O646；TM911；TB383；TG115.21⁺5.3   文献标识码：A    doi:10.3969/j.issn.1000-6281.2019.06.003

In situTEM study on mechanism of sodium storage in carbon nanofibers

HUANGFU Lei-lei, ZHAI A-min, TIAN He^*, ZHANG Ze

(Center of Electron Microscope, State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou Zhejiang 310027, China)

Abstract  In the study of negative electrode materials for sodium ion batteries, one-dimensional nanostructures, such as nanotubes, nanowires and nanofibers, are considered as high-capacity and stable electrode materials because of their uniform structure and good conductive connectivity. But, in practical application, its cycle stability needs to be further improved. However, it is found that the carbon nanofibers prepared by electrospinning have excellent cycling stability. In order to explain the reason from the microstructure, in situ TEM study about the sodiation process of a single carbon nanofiber was carried out. It was found that the volume expansion rate of the single carbon nanofiber was only about 44.6%. And the structure of the material does not change obviously before and after sodium intercalation. That may explain it’s good cycle stability. What’s more, it was found that the mechanism of sodium intercalation in carbon nanofibers was controlled by long-range diffusion, which provides guidance for the production of carbon nanofibers for sodium ion batteries.

Keywords  sodium-ion batteries；anode materials；carbon nanofibers；in situ TEM；sodiation mechanism

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