Operando soft X-ray emission spectroscopy of the Fe2O3 anode to observe the conversion reaction

Daisuke Asakura*, Yusuke Nanba, Masashi Okubo, Hideharu Niwa, Hisao Kiuchi, Jun Miyawaki, Masaharu Oshima, Eiji Hosono, Yoshihisa Harada

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Drastic electronic-structure changes in an Fe2O3 thin film anode for a Li-ion battery during discharge (lithiation) and charge (delithiation) processes were observed using operando Fe 2p soft X-ray emission spectroscopy (XES). The conversion reaction forming metallic iron due to the lithiation reaction was confirmed by operando XES in combination with the analysis using full-multiplet calculation. The valence of Fe at the open-circuit voltage (OCV) before the second cycle was not Fe3+, but Fe2+ with a weak p-d hybridization, suggesting a considerable irreversibility upon the first discharge-charge cycle and a weakened Fe-O bond after the first cycle. Moreover, we revealed that the Fe 3d electronic-structure change during the second cycle was to some extent reversible as Fe2+ (2.7 V vs. Li/Li+: open circuit voltage) → Fe0 (0.1 V vs. Li/Li+: discharged) → Fe(2+δ)+ (3.0 V vs. Li/Li+: charged). This operando Fe 2p XES in combination with the full-multiplet calculation provides detailed information for redox chemistry during a discharge-charge operation that cannot be obtained by other methods such as crystal-structure and morphology analyses. XES is thus very powerful for investigating the origin and limitation of the lithiation function of anodes involving conversion reactions.

Original languageEnglish
Pages (from-to)26351-26357
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume21
Issue number48
DOIs
Publication statusPublished - 2019
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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