Vanadium Oxide 3-D Nanostructures for Lithium Ion Battery Cathodes

Nanostructured electrodes have been a popular area of research in energy storage, where their high surface area and shortened diffusion pathways can provide increased energy and power density over bulk electrodes of the same materials. While a variety of nanostructures have been demonstrated, often these structures are disordered and randomly interconnected, or they must be held together by polymer binder which essentially constitutes a dead weight and volume in the electrode. It can be difficult to draw broadly applicable conclusions to pursue optimized electrode geometries without the ability to test electrodes with systematically variable geometries. As 3-D structures have become of greater interest in energy storage, there is a need to be able to explore the relationship between structure and performance systematically.

Here we present electrodes produced by controllably interlinking an array of uniform nanotubes. The aspect ratio of the nanotubes and the number of interconnecting points can be modified systematically. 3-D branched anodized aluminum oxide (AAO) membranes are used as templates for the atomic layer deposition of vanadium oxide (V₂O₅).  AAO templates have frequently been used to produce uniform high aspect ratio arrays of materials, and the systematic introduction of branch points allows our templates to be expanded into three dimensional networks. The use of an ALD deposition process allows these templates to be uniformly and conformally coated with V₂O₅, creating nanostructured cathodes whose morphology can be carefully and systematically controlled.

We successfully produced a series of V₂O₅ cathodes with varying aspect ratios as well as the number and spacing of branch points.  These cathodes were then characterized by a variety of electrochemical methods, including cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge. These studies will lay the groundwork for rationally designed 3-D electrodes and full battery devices in the future.