物理化学学报 >> 2022, Vol. 38 >> Issue (8): 2009073.doi: 10.3866/PKU.WHXB202009073

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原位透射电镜研究正交相五氧化二铌纳米片的电化学储钠机制

许国光1,2, 王琪2, 苏毅3, 刘美男1,2, 李清文1,2, 张跃钢2,3,*()   

  1. 1 中国科学技术大学纳米技术与纳米仿生学院, 合肥 230031
    2 中国科学院苏州纳米技术与纳米仿生研究所, 江苏 苏州 215123
    3 清华大学物理系, 北京 100084
  • 收稿日期:2020-09-22 录用日期:2020-10-26 发布日期:2020-11-02
  • 通讯作者: 张跃钢 E-mail:yuegang.zhang@tsinghua.edu.cn
  • 基金资助:
    国家重点研发计划(2016YFB0100100);国家自然科学基金(U1832218);国家自然科学基金(21433013)

Revealing Electrochemical Sodiation Mechanism of Orthogonal-Nb2O5 Nanosheets by In Situ Transmission Electron Microscopy

Guoguang Xu1,2, Qi Wang2, Yi Su3, Meinan Liu1,2, Qingwen Li1,2, Yuegang Zhang2,3,*()   

  1. 1 School of Nano Technology and Nano Bionics, University of Science and Technology of China, Hefei 230031, China
    2 Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, Jiangsu Province, China
    3 Department of Physics, Tsinghua University, Beijing 100084, China
  • Received:2020-09-22 Accepted:2020-10-26 Published:2020-11-02
  • Contact: Yuegang Zhang E-mail:yuegang.zhang@tsinghua.edu.cn
  • About author:Yuegang Zhang, Email: yuegang.zhang@tsinghua.edu.cn; Tel.: +86-10-62788965
  • Supported by:
    the National Key R & D Program of China(2016YFB0100100);the National Natural Science Foundation of China(U1832218);the National Natural Science Foundation of China(21433013)

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摘要：

由于正交相五氧化二铌(T-Nb2O5)为ReO3型层状结构，锂、钠离子可以在其(001)平面快速脱嵌，而在[001]方向的传输一般较难。本研究通过原位透射电子显微镜(Transmission Electron Microscope，TEM)方法研究钠在T-Nb2O5纳米片(001)面内及[001]方向的钠离子电化学嵌入行为，发现由于纳米片晶体存在大量的位错和畴界，钠离子可通过这些缺陷穿越(001)面扩散，并进而在深层的(001)面内快速扩散。同时，本研究还发现刚合成的T-Nb2O5纳米片在[001]方向上存在调制结构，存在交替分布的压应变和张应变区域，而钠离子的嵌入可以调节这些应变分布。

关键词: 原位透射电镜, T-Nb2O5纳米片, 钠离子电池, 钠化机理

Abstract:

With the development of clean energy sources such as solar and wind power, large-scale energy storage technologies will play a significant role in the rational utilization of clean energy. Sodium ion batteries have garnered considerable attention for large-scale energy storage owing to their low cost and the presence of abundant sodium resources. It is particularly crucial to develop electrode materials for sodium battery with good rate capability and long cycle life. Orthogonal-phase niobium oxide (T-Nb2O5) exhibits good potential to be used as anode material for sodium-ion batteries owing to its high theoretical specific capacity (200 mAh·g−1) and high ionic diffusion coefficient. Furthermore, it demonstrates a better performance than that of graphite and exhibits a higher specific capacity than that of Li4TiO4 when used in sodium-ion batteries. However, its poor electrical conductivity has hindered its practical application. Recently, effective strategies such as coating with carbon materials or metal conductive particles have been developed to overcome this issue. Although the electrochemical performance of T-Nb2O5 has been improved, the sodiation mechanism of T-Nb2O5 is still unclear. It is considered to be similar to the lithium mechanism wherein lithium ions diffuse rapidly on the (001) planes, but exhibit difficulty in diffusing across the (001) planes. In this study, the electrochemical sodiation behaviors along the (001) lattice planes and the [001] direction of the T-Nb2O5 nanosheet are studied by in situ transmission electron microscopy (TEM). The results indicate that there are a large number of dislocations and domain boundaries in nanocrystals. Furthermore, it was observed that, sodium ions can diffuse across the (001) lattice planes through these defects, and then diffuse rapidly on the (001) planes. Meanwhile, we found a modulation structure in the [001] direction of the original nanosheet, in which alternating compressive and tensile strains were observed. These strain distributions can be regulated by the insertion of sodium ions, while the modulation structure is maintained. Moreover, the in situ TEM method used in this work can be applied to various energy materials.

Key words: In situ transmission electron microscopy, T-Nb2O5 nanosheet, Sodium ion battery, Sodiation mechanism