Crystal structural changes and charge compensation mechanism during two lithium extraction/insertion between Li2FeSiO4 and FeSiO4

Titus Masese, Cédric Tassel, Yuki Orikasa, Yukinori Koyama, Hajime Arai, Naoaki Hayashi, Jungeun Kim, Takuya Mori, Kentaro Yamamoto, Yoji Kobayashi, Hiroshi Kageyama, Zempachi Ogumi, Yoshiharu Uchimoto

Research output: Contribution to journalArticlepeer-review

53 Scopus citations

Abstract

Li2FeSiO4 is a promising cathode material for lithium ion batteries because of its theoretically high capacity if two lithium ions can be extracted/inserted per formula unit; however, the extraction/insertion of two lithium ions from Li2FeSiO4 remains a challenge. Herein, we successfully synthesized carbon-coated Li2FeSiO4 nanoparticles which exhibit a capacity commensurate to a reversible two-lithium extraction/insertion at elevated temperature. This study investigates the mechanism underlying a two lithium ion extraction/insertion in Li2FeSiO4 using synchrotron X-ray absorption spectroscopy and X-ray diffraction. Our results reveal that the contribution of the Fe-3d band is dominant for the first lithium extraction process from Li2FeSiO4 to LiFeSiO4. During the second lithium extraction process from LiFeSiO4 to FeSiO4, however, ligand holes are formed in the O-2p band rather than further oxidation of Fe3+. Structural analyses further reveal a phase transformation between Li2FeSiO4 and LiFeSiO4, while a single-phase behavior is observed for Li2-xFeSiO4 (1.0 ≤x≤ 2.0). Together with a tentatively refined crystal structure of the FeSiO4 phase (x = 2.0), we discuss the charge compensation mechanism during two lithium extraction/insertion in Li2FeSiO4.
Original languageEnglish (US)
Pages (from-to)10206-10211
Number of pages6
JournalJournal of Physical Chemistry C
Volume119
Issue number19
DOIs
StatePublished - May 14 2015
Externally publishedYes

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