Reticulated vitreous carbon/polypyrrole composites as electrodes for lithium batteries: Preparation, electrochemical characterization and charge-discharge performance

摘要

Polypyrrole (PPy) composites were prepared via electrochemical deposition onto reticulated vitre-ous carbon (RVC) - a tridimensional material - and tested as cathodes in lithium batteries. Different RVC/polypyrrole electrodes were prepared and characterized: PPy doped with ClO_4 ~- (RVC/PPy) as an anion-exchanger film; PPy doped with a large anion - poly(styrenesulphonate) - (RVC/PPyPSS) as a cation-exchanger film; and a bi-layer polymeric film formed by an inner layer of the former and an outer layer of the latter (RVC/PPy/PPyPSS). Photomicrographies, voltammetric profiles and electrochemical impedance spectroscopy data have shown different morphological and electrochemical characteristics for polypyrrole doped with small or large anions, and a peculiar behavior for the bi-layer electrodes-Charge/discharge results indicated that the RVC/PPy electrode can attain specific capacities as high as 95 mAhg~(-1). PSS-doped polypyrrole electrodes also presented high specific-capacity values when the bi-layer configuration (RVC/PPy/PPyPSS) and lower charge-discharge currents were used. Impedance-data indicated that the counter-ion diffusion within the bi-layer is hindered, which explains the slower activation of this composite when compared to that of RVC/PPy.