Novel intercalated nanocomposites based on vanadium pentoxide xerogel and sodium iron oxide

Energy is a vital component of our economies and lifestyle. Unfortunately, most of the current sources of energy are not renewable or environmentally friendly. Among the efforts made to tackle this problem is the development of rechargeable batteries. Rechargeable batteries are transducers that convert chemical energy to electrical energy and vice versa. This project was designed to develop green materials that can be used in lithium/Li-ion batteries. The lithium battery chemistry is currently the most promising battery system because of its superior properties such as high voltage and energy density.

The project involved the successful intercalation of highly ionically conducting polymers Poly(oxymethylene-oxyethylene) (POMOE), Poly[oligo(ethylene glycol) oxalate] (POEGO) and Poly[bis-(methoxyethoxyethoxy)phosphazene] (MEEP) into the layered structure vanadium pentoxide xerogel (V 2O5nH2O) and the characterization of the resulting nanocomposites. Intercalation of POMOE and POEGO lead to the bilayer loading of the polymer into the gallery spaces of V2O5nH 2O. This was a significant achievement because the resulting nanocomposites have potential to intercalate more Li-ions compared to monolayer nanocomposites. Intercalation of MEEP into V2O5nH2O leads to nanocomposites whose interlayer expansions increased with increasing concentration of MEEP. The intercalates with higher MEEP concentration were mixed (electronic and ionic) conductors while the intercalates with lower concentration were electronic conductors.

Direct intercalation of the ionically conducting polymers into sodium iron oxide (NaFeO2) was not achieved. However, the projects lead to successful de-intercalation (removal) of Na from NaFeO2 via a hydrolysis reaction to produce Na1-xFeO2 (hydrolysis residue) and sodium carbonate hydrate (hydrolysis aqueous solution). The Na1-xFeO2 where x ≈ 1 had been previously predicted as an ideal alternative electrode material to the currently used LiCoO 2 in lithium batteries but had not successfully synthesized. Therefore, this was a major breakthrough in synthesizing this material. The methodology developed here has the advantage of being easily scaled up to industrial production. It was also discovered that the sodium carbonate hydrate had a layered structure and can be intercalated with guest molecules.

The new materials reported here were characterized with powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and AC impedance spectroscopy.