Structural characterization of an amorphous VS4 and its lithiation/delithiation behavior studied by solid-state NMR spectroscopy

Keiji Shimoda, Kazuto Koganei, Tomonari Takeuchi, Toshiyuki Matsunaga, Miwa Murakami, Hikari Sakaebe, Hironori Kobayashi, Eiichiro Matsubara

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Vanadium sulfide (VS4) is one of the promising positive electrode materials for next-generation rechargeable lithium-ion batteries because of its high theoretical capacity (1196 mA h g-1). Crystalline VS4 has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the c axis are loosely connected to each other through van der Waals interactions. In this study, an amorphous VS4 is prepared by mechanical milling of the crystalline material, and its lithiation/delithiation behavior is investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy. The amorphous VS4 shows a chain structure similar to that of crystalline VS4. The amorphous host structure is found to change drastically during the lithiation process to form Li3VS4: the V ions become tetrahedrally coordinated by S ions, in which the valence states of V and S ions simultaneously change from V4+ to V5+ and S- to S2-, respectively. When the Li insertion proceeds further, the valence state of V ions is reduced. After the 1st cycle, the amorphous VS4 recovers to the chain-like structure although it is highly disordered. No conversion to elemental V is observed, and a high capacity of 700 mA h g-1 is reversibly delivered between 1.5 and 2.6 V.

Original languageEnglish
Pages (from-to)23979-23985
Number of pages7
JournalRSC Advances
Volume9
Issue number41
DOIs
Publication statusPublished - 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)

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