Issue 41, 2019

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

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.

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

Supplementary files

Article information

Article type
Paper
Submitted
10 Jun 2019
Accepted
29 Jul 2019
First published
05 Aug 2019
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2019,9, 23979-23985

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

K. Shimoda, K. Koganei, T. Takeuchi, T. Matsunaga, M. Murakami, H. Sakaebe, H. Kobayashi and E. Matsubara, RSC Adv., 2019, 9, 23979 DOI: 10.1039/C9RA04338A

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