Polyaniline nanofiber/vanadium pentoxide layer-by-layer electrodes for energy storage
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Both polyaniline and vanadium pentoxide (V 2O 5) are promising electrode materials for electrochemical energy storage, but each has limitations. As a composite, the two components can interact synergistically to form an electrode better than either material alone. Using layer-by-layer (LbL) assembly as a processing technique, we successfully assembled hybrid electrodes containing polyaniline and V 2O 5. Assembly conditions were chosen to yield films that grew reliably and had a large cycle thickness. Assembly pH and concentration are critical parameters for this particular LbL system. For lower molar mass polyaniline, exponential film growth was observed; for higher molar mass polyaniline, linear growth was obtained. The electrochromic behavior of the film was characterized using UV-vis spectroscopy, and it was found that polyaniline dominated the electrochromic response. However, the electrochemical response possessed contributions from both polyaniline and V 2O 5. Films made from lower molar mass polyaniline had a charge storage capacity of 264 mAh/cm 3. The films' ability to store charge was also dependent on film thickness, as was the fraction of electrochemically accessible material. This work highlights how LbL assembly can be applied to produce intimately mixed electrodes containing both organic and inorganic materials. 2011 American Chemical Society.