title: Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide.
abstract: Vanadium sulfide VS4 in the patronite mineral structure is a linear chain compound comprising vanadium atoms coordinated by disulfide anions [S2](2-). (51)V 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 [S2](2-) resulting in oxidation of V(4+) to V(5+) and reduction of the [S2](2-) to S(2-) to form Li3VS4 containing tetrahedral [VS4](3-) anions. On further lithiation this is followed by reduction of the V(5+) in Li3VS4 to form Li3+xVS4 (x = 0.5-1), a mixed valent V(4+)/V(5+) compound. Eventually reduction to Li2S 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 (51)V 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.
authors.affiliation: †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Britto
authors.affiliation: †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Michal
authors.initials: M
authors.lastname: Leskes
authors.affiliation: †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Xiao
authors.initials: X
authors.lastname: Hua
authors.affiliation: ‡College of Creative Studies, University of California, Santa Barbara, California 93106, United States.
authors.forename: Claire-Alice
authors.initials: CA
authors.lastname: Hébert
authors.affiliation: §Department of Chemistry and Department of Energy Engineering, Ulsan National Institute of Science and Technology, Korea.
authors.forename: Hyeon Suk
authors.initials: HS
authors.lastname: Shin
authors.affiliation: ∥Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, U.K.
authors.forename: Simon
authors.initials: S
authors.lastname: Clarke
authors.affiliation: ⊥X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Illinois 60439, United States.
authors.forename: Olaf
authors.initials: O
authors.lastname: Borkiewicz
authors.affiliation: ⊥X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Illinois 60439, United States.
authors.forename: Karena W
authors.initials: KW
authors.lastname: Chapman
authors.affiliation: #Mitsubishi Chemicals Center for Advanced Materials Research Laboratory, University of California, Santa Barbara, California 93106, United States.
authors.forename: Ram
authors.initials: R
authors.lastname: Seshadri
authors.affiliation: ¶Nano Energy Materials Lab, Interdisciplinary School of Green Energy, Ulsan National Institute of Science and Technology, Korea.
authors.forename: Jaephil
authors.initials: J
authors.lastname: Cho
authors.affiliation: †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Clare P
authors.initials: CP
authors.lastname: Grey