Effect on water consumption by metallic impurities into electrolyte of lead-acid batteries

Abstract

Because of the continuous increment of the use of recycled lead in the manufacturing of Lead-Acid Batteries (LABs), the presence of metallic impurities in the batteries has also increased. These impurities have a high impact in this industry as they can be catalytic precursors of the secondary reactions that occur in the LAB performance: the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER). When the secondary reactions are catalyzed, the water consumption of a battery might be increased. In this way, negative effects such as the decrease of high-temperature durability and the increase of self-discharge could occur, even the safety of the battery itself could be jeopardized. Due to these facts, the aim of the present research work was to develop a quick-low-cost system that measured the effect of metallic impurities in the LAB electrolyte. This system consisted of a three electrode cell, able to detect low concentration effect of metallic impurities in the battery electrolyte, applying the Cyclic Voltammetry (CV) technique. In addition, a qualitative study was carried out comparing the catalytic impurity effect on HER in two different systems: a three electrode cell and a 2 V/ 1 Ah lead-acid mono cell. The following impurities were studied at different concentrations: nickel, bismuth, zinc, silver and selenium. The results show that the study by CV allows detecting the effect of impurities qualitatively at low concentrations of all impurities studied, except zinc. Furthermore, it was observed that an increment in the concentration of nickel and selenium in the LAB electrolyte leads to a noticeable increase in HER both in the three electrode and 2 V/ 1 Ah cell systems.