Caracterização eletroquímica, morfológica e estrutural dos aditivos carbon black e óxido de grafite usados em precursores de placas negativas de baterias chumbo-ácido

Abstract

Lead-acid batteries are widely used in society, especially in motor vehicles. Both the negative and positive plates of these batteries are reinforced with additives that seek to improve their performance. In the negative plate, the most commonly used additives are: BaSO4, lignosulfonates and carbon materials. In this work, we studied how 2 different carbon additives affected morphological properties of the precursor material of the negative plate of the battery, namely carbon black and graphite oxide. Firstly, the characterization of the additives and the precursor material was carried out by Infrared Absorption Spectroscopy, thermogravimetric analysis, Raman spectroscopy, x-ray diffraction and atomic force microscopy, obtaining important information about their structures. Regarding the effects of the additives, the volume of macropores and surface area that they generated in the plates of the precursor material with different concentrations (0%, 0.4%, 0.6% and 0.8%; ratio of additive mass/mass of lead oxide) was verified. The carbon black plates showed higher macroporosity values, a fact that was a consequence of their structure presenting a higher volume of mesopores (0.4261 cm3 /g) than graphite oxide (0.0108 cm3 /g). However, graphite oxide provided higher area values for the plates. In addition, a capacitive behavior for carbon black was verified by cyclic voltammetry, a behavior that was not verified in graphite oxide voltammetry, as a consequence of having a lower BET area than carbon black (2.4134 m2 /g and 215.1797 m2 /g) and for being an electronic conductor. The higher macroporosity of the precursor material with carbon black will lead to the formation of negative active materials with higher porosity, which is important for automotive batteries.