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Title: Structural and dynamic behavior of lithium iron polysulfide Li₈FeS₅ during charge–discharge cycling
Authors: Shimoda, Keiji  kyouindb  KAKEN_id  orcid (unconfirmed)
Murakami, Miwa  kyouindb  KAKEN_id  orcid (unconfirmed)
Takeuchi, Tomonari
Matsunaga, Toshiyuki
Ukyo, Yoshio
Sakaebe, Hikari
Kobayashi, Hironori
Matsubara, Eiichiro
Author's alias: 村上, 美和
松永, 利之
右京, 良雄
松原, 英一郎
Keywords: Lithium-sulfur batteries
Lithium metal polysulfide
Delithiation-induced amorphization
S-S polysulfide bond
Li diffusive motion
Issue Date: 15-Sep-2018
Publisher: Elsevier BV
Journal title: Journal of Power Sources
Volume: 398
Start page: 67
End page: 74
Abstract: Lithium sulfide (Li₂S) is one of the promising positive electrode materials for next-generation rechargeable lithium batteries. To improve the electrochemical performance of electronically resistive Li₂S, a Fe-doped Li₂S-based positive electrode material (Li₈FeS₅) has been recently designed and found to exhibit excellent discharge capacity close to 800 mAh g⁻¹. In the present study, we investigate the structural and dynamic behavior of Li₈FeS₅ during charge–discharge cycling. In Li₈FeS₅, Fe ions are incorporated into the Li₂S framework structure. The Li₂S-based structure is found to transform to an amorphous phase during the charge process. The delithiation-induced amorphization is associated with the formation of S-S polysulfide bonds, indicating charge compensation by S ions. The crystalline to non-crystalline structural transformation is reversible, but Li ions are extracted from the material via a two-phase reaction, although they are inserted via a single-phase process. These results indicate that the delithiation/lithiation mechanism is neither a topotactic extraction/insertion nor a conversion-type reaction. Moreover, the activation energies for Li ion diffusion in the pristine, delithiated, and lithiated materials are estimated to be in the 0.30–0.37 eV range, which corresponds to the energy barriers for local hopping of Li ions along the Li sublattice in the Li₂S framework.
Rights: © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license
The full-text file will be made open to the public on 15 September 2020 in accordance with publisher's 'Terms and Conditions for Self-Archiving'.
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
DOI(Published Version): 10.1016/j.jpowsour.2018.07.055
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