As propriedades eletroquímicas de compósitos do tipo Pani(DMcT-íon Cu)/fibra de carbono, obtidos eletroquimicamente, são analisadas em função tanto do procedimento de preparação como do sal de cobre (CuCl 2 .2H 2 O ou CuSO 4 ) utilizado para a incorporação de íons Cu 2+ no compósito. Dois procedimentos foram utilizados: adicionando-se o sal de cobre diretamente ao eletrólito durante a eletropolimerização da polianilina (procedimento A), ou adsorvendo-se os íons cobre juntamente com o DMcT sobre a fibra de carbono antes da eletropolimerização (procedimento B). A estabilidade eletroquímica, as propriedades elétricas e a morfologia desses compósitos foram analisadas, por voltametria cíclica, espectroscopia de impedância eletroquímica e microscopia eletrônica de varredura, respectivamente.The electrochemical properties of Pani(DMcT-Cu ion)/carbon fiber composites, obtained by electrochemical means, are analysed as a function of the preparation procedure and the different copper salts (CuCl 2 .2H 2 O or CuSO 4 ) used as source of Cu 2+ ions to be incorporated into the Pani(DMcT)/carbon fiber composite. The composites were prepared according to two procedures: by adding the copper salt directly to the electrolyte during the polyaniline electrosynthesis (procedure A), or by allowing the copper ion to be physically adsorbed onto the carbon fiber prior to the polymer electroformation (procedure B). The electrochemical stability, electrical properties and morphology of the composites were analysed by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy, respectively.Keywords: polyaniline, carbon fiber, DMcT, composites, impedance spectroscopy
IntroductionIn the recent past decades, the demand for rechargeable batteries has exploded due to the enormous increase in the variety and number of portable devices, especially cellular phones. At the same time, the need has increased for batteries that are smaller, lighter, with higher energy density and more environmentally benign. It is expected that this dependence on batteries as energy sources will become even greater in the future due to an increase in the number of miniaturized devices. Therefore development of novel electrode materials is currently demanded so as to increase the energy density of batteries for different applications, including those for electric vehicles and the load leveling of electric power consumption.Disulfide compounds have been recently proposed as alternative materials for high-energy cathodes in lithium batteries. 1-14 A series of compounds having -SH groups are thought to have a significant potential as energy storage materials, whereby energy exchange occurs according to a reversible polymerization-depolymerization process (2 SH ↔ S-S). 1,2 Among these compounds, 2,5-dimercapto-1,3,4-thiadiazole (DMcT) was first studied by Visco and co-workers 6 as an active cathode material for lithium secondary batteries. However, its redox reaction is too slow at room temperature. Thus, to improve the redox dynamics of DM...