Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide
Shin, Hyeon Suk
Chapman, Karena W.
Grey, Clare P.
Journal of the American Chemical Society
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Britto, S., Leskes, M., Hua, X., Hébert, C., Shin, H. S., Clarke, S., Borkiewicz, O., et al. (2015). Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide. Journal of the American Chemical Society, 137 (26), 8499-8508. https://doi.org/10.1021/jacs.5b03395
This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/jacs.5b03395
Vanadium sulfide VS_4 in the patronite mineral structure is a linear chain compound comprising vanadium atoms coordinated by disulfide anions [S_2]^2–. 51V NMR shows that the material, despite having V formally in the d^1 configuration, is diamagnetic, suggesting potential dimerization through metal–metal bonding associated with a Peierls distortion of the linear chains. This is supported by density functional calculations, and is also consistent with the observed alternation in V–V distances of 2.8 and 3.2 Å along the chains. Partial lithiation results in reduction of the disulfide ions to sulfide S^2–, via an internal redox process whereby an electron from V^4+ is transferred to [S_2]^2– resulting in oxidation of V^4+ to V^5+ and reduction of the [S_2]^2– to S^2– to form Li_3VS_4 containing tetrahedral [VS_4]^3– anions. On further lithiation this is followed by reduction of the V^5+ in Li_3VS_4 to form Li(_3+x)VS_4 (x = 0.5–1), a mixed valent V^4+/V^5+ compound. Eventually reduction to Li_2S plus elemental V occurs. Despite the complex redox processes involving both the cation and the anion occurring in this material, the system is found to be partially reversible between 0 and 3 V. The unusual redox processes in this system are elucidated using a suite of short-range characterization tools including 51V nuclear magnetic resonance spectroscopy (NMR), S K-edge X-ray absorption near edge spectroscopy (XANES), and pair distribution function (PDF) analysis of X-ray data.
S.B. acknowledges Schlumberger Stichting Fund and European Research Council (EU ERC) for funding. J.C. thanks BK21 plus project of Korea. We thank Phoebe Allan and Andrew J. Morris, University of Cambridge, for useful discussions. We also thank Trudy Bolin and Tianpin Wu of Beamline 9-BM, Argonne National Laboratory, for help with XANES measurements. The DFT calculations were performed at the UCSB Center for Scientific Computing at UC Santa Barbara, supported by the California Nanosystems Institute (NSF CNS-0960316), Hewlett-Packard, and the Materials Research Laboratory (DMR-1121053). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
External DOI: https://doi.org/10.1021/jacs.5b03395
This record's URL: https://www.repository.cam.ac.uk/handle/1810/248880