(296d) Polyaniline Nanofiber/Vanadium Pentoxide Layer-by-Layer Electrodes for Energy Storage

Li-ion batteries have garnered much interest in portable power, but in some aspects, they are limited. For example, some commercial Lithium-ion battery electrodes are subject to volumetric expansion, safety concerns, and high cost. However, nanostructured electrodes comprised of alternative materials can potentially address many of these limitations. Here, we report the layer-by-layer assembly of polyaniline (PANI) nanofibers and V₂O₅ to form hybrid electrodes for electrochemical energy storage. PANI nanofibers assist in forming a highly porous electrode (density = 0.247g/cm³), and impart electronic conductivity. Both PANI and V₂O₅ store charge through Faradaic reactions. Together, this composite may form an electrode that surpasses either material alone. The growth of the film was investigated using profilometry and quart crystal microbalance; the thickness of these films increased linearly with respect to the number of layer pairs deposited. The non-aqueous electrochemistry of the electrode was explored using lithium as a counter and reference electrode. It was found that the electrochemical response possessed contributions from both PANI nanofibers and V₂O₅, and that the electrochemical performance of this LbL system was dependant on film thickness. A maximum capacity of 233 mAh/g at a current of 2µA/cm² was measured for a film of 16 layer pairs. In addition, PANI nanofibers were found to dominate the electrochromic response measured using UV-Vis spectroscopy. The composition of the film and the oxidation state of vanadium were measured and monitored using X-ray photoelectron spectroscopy (XPS). No appreciable volumetric expansion after charge/discharge cycling. Based on our current study, the formation of pernigraniline base polyaniline was attributed to the performance degradation of these films. This study indicates how LbL assembly can be used to fabricate high-performance electrodes for electrochemical energy storage.