Effects of cationic CTAB and anionic SDBS surfactants on the performance of Zn–MnO2 alkaline batteries

Abstract

Inhibiting properties of two kinds of surfactant, cationic cetyl trimethyl ammonium bromide (CTAB) and anionic sodium dodecyl benzene sulfonate (SDBS) with three different concentrations, in relation to zinc passivation have been explained in the primary Zn/MnO2 alkaline batteries. Discharge performance of alkaline cell affected by utilization of surfactant in anodic gel. Therefore, electrochemical properties of anodic zinc have been investigated by cyclic voltammetry, X-ray diffraction, scanning electron microscopy (SEM) and ac impedance techniques. The results show that alkaline cell with 0.01 g l−1 of anionic SDBS surfactant decreased effectively the rate of zinc-passivation reaction. Also, it exhibited ZnO morphology with smaller grain size, causing longer service life gradually, step by step. By contrast, 0.01 g l−1 of cationic CTAB surfactant remarkably increased the rate of charge transfer and mass transfer in the alkaline cell, on impedance data. Consequently, more volumetric energy density obtained in first discharge step due to more activated zinc surface area. Furthermore, scanning electron microscopy (SEM) has shown non-homogenous morphology with coarse ZnO growth. This was confirmed by X-ray diffractograms showing the highest intensity of ZnO peak. When the concentration of these surfactants (CTAB and SDBS) increased, more inhibiting properties were observed. This property was stronger in the cells with anionic SDBS surfactant. Our study is mainly focused on the understanding the mechanism of zinc passivation in the presence of the surfactants.