LAUSR

Abstract Rechargeable magnesium batteries provide the potential for lower cost and improved safety compared with lithium-ion batteries, however obtaining cathode materials with highly reversible Mg-ion capacities is hindered by the high polarizability of divalent Mg-ions and slow solid-state Mg-ion diffusion. We report that incorporating poly(ethylene oxide) (PEO) between the layers of hydrated vanadium pentoxide (V 2 O 5 ) xerogels results in significantly improved reversible Mg-ion capacities. X-ray diffraction and high resolution transmission electron microscopy show that the interlayer spacing between V 2 O 5 layers was increased by PEO incorporation. Vibrational spectroscopy supports that the polymer interacts with the V 2 O 5 lattice. The V 2 O 5 -PEO nanocomposite exhibited a 5-fold enhancement in Mg-ion capacity, improved stability, and improved rate capabilities compared with V 2 O 5 xerogels. The Mg-ion diffusion coefficient of the nanocomposite was increased compared with that of V 2 O 5 xerogels which is attributed to enhanced Mg-ion mobility due to the shielding interaction of PEO with the V 2 O 5 lattice. This study shows that beyond only interlayer spacing, the nature of interlayer interactions of Mg-ions with V 2 O 5 , PEO, and H 2 O are key factors that affect Mg-ion charge transport and storage in layered materials. The design of layered materials with controlled interlayer interactions provides a new approach to develop improved cathodes for magnesium batteries.