title: The structural conversion from α-AgVO3to β-AgVO3: Ag nanoparticle decorated nanowires with application as cathode materials for Li-ion batteries.
abstract: The majority of electrode materials in batteries and related electrochemical energy storage devices are fashioned into slurries via the addition of a conductive additive and a binder. However, aggregation of smaller diameter nanoparticles in current generation electrode compositions can result in non-homogeneous active materials. Inconsistent slurry formulation may lead to inconsistent electrical conductivity throughout the material, local variations in electrochemical response, and the overall cell performance. Here we demonstrate the hydrothermal preparation of Ag nanoparticle (NP) decorated α-AgVO3nanowires (NWs) and their conversion to tunnel structured β-AgVO3NWs by annealing to form a uniform blend of intercalation materials that are well connected electrically. The synthesis of nanostructures with chemically bound conductive nanoparticles is an elegant means to overcome the intrinsic issues associated with electrode slurry production, as wire-to-wire conductive pathways are formed within the overall electrode active mass of NWs. The conversion from α-AgVO3to β-AgVO3is explained in detail through a comprehensive structural characterization. Meticulous EELS analysis of β-AgVO3NWs offers insight into the true β-AgVO3structure and how the annealing process facilitates a higher surface coverage of Ag NPs directly from ionic Ag content within the α-AgVO3NWs. Variations in vanadium oxidation state across the surface of the nanowires indicate that the β-AgVO3NWs have a core-shell oxidation state structure, and that the vanadium oxidation state under the Ag NP confirms a chemically bound NP from reduction of diffused ionic silver from the α-AgVO3NWs core material. Electrochemical comparison of α-AgVO3and β-AgVO3NWs confirms that β-AgVO3offers improved electrochemical performance. An ex situ structural characterization of β-AgVO3NWs after the first galvanostatic discharge and charge offers new insight into the Li+reaction mechanism for β-AgVO3. Ag+between the van der Waals layers of the vanadium oxide is reduced during discharge and deposited as metallic Ag, the vacant sites are then occupied by Li+.
authors.affiliation: Department of Chemistry, University College Cork, Cork, T12 YN60, Ireland.
authors.forename: David
authors.initials: D
authors.lastname: McNulty
authors.affiliation: SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD, UK.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Ramasse
authors.affiliation: Department of Chemistry, University College Cork, Cork, T12 YN60, Ireland and Micro-Nano Systems Centre, Tyndall National Institute, Lee Maltings, Cork, T12 R5CP, Ireland. c.odwyer@ucc.ie.
authors.forename: Colm
authors.identifier: http://orcid.org/0000-0001-7429-015X
authors.initials: C
authors.lastname: O'Dwyer