Anionic Redox Activity as a Key Factor in the Performance Degradation of NaFeO2 Cathodes for Sodium Ion Batteries

Title
Anionic Redox Activity as a Key Factor in the Performance Degradation of NaFeO2 Cathodes for Sodium Ion Batteries
Authors
정경윤장혜정조민경김형석김지영굴람 알리디키 수산토남경완
Keywords
sodium ion battereis; NaFeO2; degradation
Issue Date
2019-05
Publisher
Chemistry of materials
Citation
VOL 31, NO 10-3651
Abstract
The origin of the irreversible capacity of O3-type NaFeO2 charged to high voltage is investigated by analyzing the oxidation state of Fe and phase transition of layered NaFeO2 cathodes for sodium-ion batteries during the charging process. In-situ X-ray absorption spectroscopy results revealed that charge compensation does not occur through the Fe3+/Fe4+ redox reaction during sodium extraction as no significant shift to high energy was observed in the Fe K-edge. These results were reinforced with ex-situ near-edge X-ray absorption spectroscopy, which suggests that oxygen redox activity is responsible for charge compensation. Formation of Fe3O4 product occurs because of oxygen release at high voltage when more than 0.5 Na is extracted from the structure; this is observed by transmission electron microscopy. NaFeO2 irreversibility is due to the formation of Fe3O4 with oxygen release, which inhibits Na insertion into the structure.
URI
http://pubs.kist.re.kr/handle/201004/69525
ISSN
0897-4756
Appears in Collections:
KIST Publication > Article
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