Sunday, 28 May 2017: 17:20
Grand Salon D - Section 24 (Hilton New Orleans Riverside)
Cathode materials that have high reversible magnesium-ion capacities and reasonable operating voltages are needed for rechargeable magnesium batteries. Layered materials are a particularly promising class of materials for electrochemical Mg-ion charge storage, however additional research is needed to increase Mg-ion capacities, improve capacity retension upon cycling, and understand the nature of interlayer interactions. Our work has investigated hydrated vanadium pentoxide (V2O5) xerogels that incorporate poly(ethylene oxide) (PEO) between the layers as an approach to improve Mg-ion charge storage and control interlayer structure and dynamics. V2O5 nanosheets were grown in the presence of PEO to allow inimate interaction with the V2O5 layers and allow control of the PEO content in V2O5-PEO nanocomposites. X-ray diffraction and high resolution transmission electron microscopy demonstrate that the interlayer spacing between V2O5 layers was increased by incorporating PEO within the layers. The Mg-ion diffusion coefficient was shown to be strongly dependent on not only interlayer spacing, but also interlayer composition. With specific polymer compositions, Mg-ion diffusion within V2O5-PEO nanocomposites was significantly increased compared with V2O5 xerogels. Raman spectroscopy supports that the polymer interacts with the V2O5 lattice resulting in interlayer water that is less strongly bound to the V2O5 lattice. The V2O5-PEO nanocomposite with specific PEO compositions exhibited significantly improved Mg-ion specific capacity compared with V2O5 xerogels and showed improved capacity retension upon cycling. Our work supports that in addition to interlayer spacing, controlling interlayer interactions between V2O5 layers, PEO, H2O, and Mg-ions allows significant improvements in Mg-ion charge transport and storage. The design of layered materials with controlled interlayer compositions provides a novel route to significantly improve charge storage and transport in layered materials.