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

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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