Effect of polymers on gel electrolyte properties in lead acid battery

Abstract

This thesis studied the effects of additives on the performance of gelled-electrolyte by measuring the conductivity values and discharge capacities of valve-regulated lead-acid (VRLA) batteries. The gelled-electrolyte containing 2%(w/v) of fumed silica and 35%(w/v) of sulfuric acid provided the highest conductivity () of 838 mS/cm at 25oC. This gelled electrolyte was selected for development by adding various additives. In order to improve the battery rechargeability, the textural evolution of the positive active material, life cycle and the electrical conductivity of gelled-electrolyte were optimized by using sodium sulfate, orthophosphoric acid, conducting polymers (polyaniline, polypyrrole and poly(1,4-phenylene sulfide)), mixtures of sodium sulfate and orthophosphoric acid, mixtures of sodium sulfate and conducting polymers and mixture of sodium sulfate, orthophosphoric acid and conducting polymers. Moreover, the gelling time and the oxygen recombination process of gelled-electrolytes with various types of additives were investigated. Finally, the discharge capacity was compared with the standard capacity (at 25oC) of VRLA battery containing a liquid electrolyte at a 1-hour rate. From the results, it was found that fumed silica, sulfuric acid and additives affected the electrical conductivity and the gelling time of gelled electrolyte. The conductivity of the gelled electrolytes was related to the discharge capacity of VRLA batteries containing gelled-electrolytes. The high discharge capacities were obtained from gelled electrolytes containing only polypyrrole and a mixture of polypyrrole and sodium sulfate. These electrolytes provided the least water loss. In addition, the gelled electrolytes containing conducting polymers including polyaniline, polypyrrole and poly(1,4-phenylene sulfide) and/or sodium sulfate and without adding additives increased the capacity when compared to the standard VRLA battery containing liquid electrolyte. On the contrary, the gelled electrolytes containing phosphoric acid showed the lowest conductivity and discharge capacity.