Improved performance of rechargeable alkaline batteries via surfactant-mediated electrosynthesis of MnO2

An innovative application of surfactant-mediated modifications of electrolytic MnO2 (EMD), proved to be a major step toward enhancement of the rechargeability in alkaline batteries. Presence of different surfactants in boiling acidic solutions of manganese sulfate, under atmospheric pressure, enhanced a variety of EMD products, with various structural and electrochemical properties. Surfactants employed consisted of: anionic sodium n-dodecylbenzenesulfonate (SDBS), cationic cetyltrimethylammonium bromide (CTAB) and non-ionic t-octyl phenoxy polyethoxyethanol (Triton X-100). Among them, EMDs produced in the presence of CTAB has a slight positive effect on the cycle performances, while SDBS inhibits it. Interestingly, the EMD powders prepared from the micellar solution, in the range of 0.3 wt.% of Triton X-100, exhibited much higher discharge capacities, as well as better cyclabilities in comparison with the commercial EMD sample known as TOSOH (TM). The superiority of the former EMD was further confirmed through electrochemical cyclic voltammetry and also electrochemical impedance spectroscopy (EIS). Modifications of electrolytic MnO2 via mediations of different surfactants were perceived through changes in their compositions, crystal structures and morphologies. The characteristics of the produced materials were determined by thermogravimetric analysis (TGA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Enhancements of electrochemical properties, observed for Triton X-100 modified EMD, could be attributed to a homogeneous current distribution with unique crystalline structure, based on the modified electrode/solution interface, through adsorbed surfactant layers. Moreover, the observed improvements appear connected to the enhanced film growth, with different degrees of mesoscopic organizations. Higher cycle performances, mechanical stabilities and the ease of production make this method excellent for being employed in a number of industrial applications. (c) 2004 Elsevier B.V. All rights reserved.