Strategies for Counteracting Hydrogen Evolution and Water Loss in Lead–Acid Batteries
Excessive gassing during final charge and floating of lead–acid batteries leads to water loss, positive plate corrosion and eventually premature failure of batteries. The root cause of the problem is antimony poisoning which is known to speed up the hydrogen evolution reaction. Today, water losses due to gassing impact many of the new applications of lead–acid batteries that are particularly popular in India and other Asian countries, e.g., light electric vehicles, e-rickshaws, inverters. This presentation examines the mechanism of antimony-catalysed water losses and proposes ways to prevent them.
Separators play an important role with respect to antimony poisoning of deep-cycle batteries. Among the different mechanisms proposed for their beneficial effect, capturing antimony ions in the separator or ‘de-activating’ antimony in the negative plate (i.e., inhibition of hydrogen evolution reaction) are the two most elaborated in the literature. These effects are linked to the specific materials from which the separators are made. For instance, the various types of rubbers that are most commonly used in modern separators and are known for their antimony-suppressing ability.
This presentation attempts to identify the mechanism by which some natural materials (rubbers, wood chips) and chemical substances such as surface-active molecules (benzaldehydes, polyglycols, surfactants) effectively prevent the poisoning of negative active-mass (NAM) by antimony, and in a more general sense by metal contaminants. Experimental work is reported that takes special care to mimic the complex chemical environment of the negative electrode of a battery in every detail. This approach offers a bridge towards an effective implementation of this knowledge in operating batteries. Based on this exploration of antimony poisoning, strategies to prevent negative effects on lead–acid batteries are proposed. The role of the separator for providing long and robust operation of batteries prone to metal poisoning — in particular deep-cycle designs — is explained. This understanding can assist lead–acid batteries to perform better in new applications that require frequent cycling and also help reduce their maintenance (water refill) and thereby become less susceptible to accidental contamination of electrolyte.
Mateusz Donten is a trained electrochemist whose scientific experience includes corrosion, metal plating and energy storage. He graduated from the Faculty of Chemistry at the University of Warsaw and received a PhD at the University of Zurich. Mateusz joined Amer-Sil in 2014 and is now the R&D Manager. His team is seeking improvements not only in separators and gauntlets for lead–acid batteries, but also in membranes for other battery technologies.