Cailin Buchanan

Expander molecules like Vanisperse A are added to the negative electrodes in lead acid (PbA) batteries to enhance surface area and discharge performance. These expanders typically reduce charging rates, however, which limits the use of PbA batteries in advanced applications. A deeper understanding of the ways that expander molecules interact with lead species and ultimately control discharge and charge performance remains elusive. Additionally, investigations of alternative expander molecules are often based on a “trial and error” approach, which is a slow experimental process that limits researchers’ abilities to draw broader conclusions. We have developed an automated electrochemistry platform to screen model expander molecules (MEMs) systematically as a function of their functional groups using cyclic voltammetry. Electrochemical performance is quantified through discharge and charge enhancement factors relative to a baseline performance without expanders. We establish four categories of MEMs: enhancers, inhibitors, traditional, and rheology modifiers. Although many MEMs that have been screened to date have been categorized as traditional or inhibitor, a novel class of enhancers have been identified as well, which were not even considered possible. The automated platform has accelerated the pace of electrochemical screening and allowed for better reproducibility and quality control through repeat measurements. The results of the electrochemical screening can be used to draw correlations between performance and structural motifs of the expanders, especially when we couple the electrochemical performance results with density functional theory calculations. Ultimately, the accelerated MEMs investigation will help lead to a deeper understanding of relevant performance mechanisms for PbA batteries.