Controlling interlayer interactions in vanadium pentoxide-poly(ethylene oxide) nanocomposites for enhanced magnesium-ion charge transport and storage

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 and is attributed to enhanced Mg-ion mobility due to 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.

Recent Progress on Layered Cathode Materials for Nonaqueous Rechargeable Magnesium Batteries

“…[40] In operando synchrotron diffraction and X-ray absorption spectroscopy were first used to investigate the structural evolution and charge compensation mechanisms of -V 2 O 5 in magnesium ion batteries (MIBs). As shown in Figure 3b In general, the electrochemical performance of layered V 2 O 5 can be improved by introducing water into the electrolyte and/or structure, or both, [37,41,43] enlarging the interlayer spacing [44] , reducing the particle size [45] , incorporating carbon materials [29,46] , and cation pre-intercalation [42,47,48] . The positive effect of water in the electrolyte for the Mg storage capacity of V 2 O 5 was first discovered by Desilvestro et al [37] Subsequently, Ceder"s group discovered that the discharge voltage of Xerogel-V 2 O 5 can be increased by water co-intercalation with Mg 2+ .…”

Fast kinetics of multivalent intercalation chemistry enabled by solvated magnesium-ions into self-established metallic layered materials

“…Nevertheless, a number of studies have been performed to overcome these intrinsic problems and have shown enhanced electrochemical performances. These include introducing a shielding layer 9 , 10 or using hydrates 11 , 12 aiming at reducing the interaction between the Mg 2+ and the host materials. It is important to note that the shielding molecules should be chosen carefully because they could also participate in the cation shuttle, having a risk to reach the anode side which may cause passivation of the Mg anode.…”

Recent Progress and Challenges in the Optimization of Electrode Materials for Rechargeable Magnesium Batteries

“…introduced PEO during the synthesizing process of V 2 O 5 sol–gel to increase the V 2 O 5 interlayer spaces and reduce the interaction barrier of divalent Mg ions. [ 180 ] As a result of the V 2 O 5 –PEO structure, the composite demonstrated about fivefold increasing of Mg‐storage capacity, enhanced rate performance and improved cycling stability compared with V 2 O 5 xerogels. Both of the two works point out a new direction for RMBs and even other multivalent‐ion batteries.…”