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Title: Germanium as a Sodium Ion Battery Material: In Situ TEM Reveals Fast Sodiation Kinetics with High Capacity

Amorphous germanium (a-Ge) nanowires have great potential for application as anodes in Na-ion batteries. However, the Na-Ge reaction is much less studied and understood compared with other metal alloy anodes. Here, in situ transmission electron microscopy (TEM) is used to study the sodiation/desodiation behavior of a-Ge nanowires. Unexpectedly, our experiments revealed that a-Ge nanowires can be charged at a very fast rate and the final sodiation product, with over 300% volume expansion, is close to Na3Ge instead of NaGe which was considered as the ultimate sodiation state that Ge could achieve. Porous structure was observed in desodiation and, in contrast to delithiation, Na extraction is more likely to create pores in the nanowires due to the much larger radius of the Na ion. This porous structure has demonstrated excellent robustness upon cycling: it could recover flawlessly from the giant pores that were created during experimentation. These results show that the potential of a-Ge for Na-ion battery applications may have been previously underestimated.
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Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0897-4756; 48266; KP1704020
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 28; Journal Issue: 4
American Chemical Society (ACS)
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
in situ TEM; germanium nanowire; sodium-ion batteries; amorphous; Environmental Molecular Sciences Laboratory