The research group of teacher Huang Jianyu of Yanshan University used advanced in-situ environmental transmission electron microscopy technology to study the sodium deposition/stripping (Plating/stripping) process, and found that sodium metal grew into some polyhedral structures during the early deposition process, and the {100} crystal face family was exposed. In the stripping (Stripping) process of sodium, Na is stripped along the layer of the {110} facet family, turning to the {112} facet family while gradually stripping to the corners of the polyhedron. There are differences in the deposition and exfoliation processes of sodium and lithium metal. DFT theoretical simulations show that the deposition and stripping of sodium follow the minimum energy path or Woolf's law, and the special shape of sodium deposition process is the result of the interaction of atomic deposition rate and mass flux. The research results were published in "Journal of Materials Chemistry A" under the title of "In situ imaging the dynamics of sodium metal deposition and stripping". Teachers Huang Jianyu, Zhang Liqiang and Tang Yongfu of Yanshan University, Ding Feng of Korea Institute of Basic Science are the co-corresponding authors of the paper, and Geng Lin (1/2) and Zhao Chao (2/2) are the co-first authors of the paper.

In-situ link: https://pubs.rsc.org/en/content/articlelanding/2022/TA/D2TA02513B

Figure 1 The PicoFemto of Zeyu Technology (ZepTools) was used in this study.®The series of in-situ TEM-STM sample rods set up an in-situ test environment.

Figure 2 In-situ charging and discharging

Figure 3 In-situ charging and discharging

Figure 4 In-situ charging and discharging

In summary: it is very important for sodium metal batteries to control the morphology of sodium deposition and alleviate the growth of sodium dendrites. This in situ study is of great significance for battery research. In the experiment, sodium was grown in a carbon dioxide atmosphere, and the surface of the sodium polyhedron has a layer of sodium carbonate that is very similar to the SEI in sodium ion batteries. The researchers found that the shape of sodium deposition process is the result of the combined effect of atomic deposition rate and mass flux. It is possible to control the shape of sodium deposition by controlling the deposition voltage and environment, which is instructive for the future good control of sodium metal deposition.

This is the second work of Mr. Huang's research group in the recent in-situ sodium dendrite growth research. We have already pushed the article on electrochemical Oswald ripening mechanism in sodium dendrite growth. For details, please refer to the previous article. Thank Dr. Geng Lin for his review of the public article!

In-situ sample rod used in the article in Figure 5