Electrochemical Reduction of Ag0.48VOPO4: A Mechanistic Study Employing X-Ray Absorption Spectroscopy and X-Ray Powder Diffraction

The electrochemical reduction of Ag0.48VOPO4 • 1.9H2O is accompanied by vanadium and silver oxidation state changes, characterized with X-ray absorption spectroscopy (XAS), and by structural changes, characterized with X-ray powder diffraction (XRD). The XAS data suggest that the initial reduction process, involving 0 to 0.5 electron equivalents, involved primarily the reduction of vanadium cations, while most of the silver cations are reduced between 0.5 to 1.0 electron equivalents. The XRD data display significant intensity decreases of absorbances associated with the 004 and 006 planes upon electrochemical reduction, consistent with a reduction-displacement of Ag+ with insertion of Li+. Retention of intensity of the absorbance associated with the 002 plane, with only minor decrease in interlayer spacing, indicates retention of the VOPO4 sublattice structure. Uncovering the details of the discharge mechanism of bimetallic cathode materials such as Ag0.48VOPO4 should enable the design of future high current cathodes for secondary batteries displaying an enhanced current capacity based on a reduction-displacement strategy. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0621508jes] All rights reserved.