BCI Battery Poster Research Showcase

Poster Submission Highlights:

Investigation of organic expander molecules to advance understanding of structure-function relationships in lead acid batteries

Cailin Buchanan, Argonne National Laboratory, Winner

Expander molecules like Vanisperse A are added to the negative electrode pastes used in lead acid (PbA) batteries to promote high surface area and favorable discharge performance. Despite these advantages, expander molecules typically inhibit charging rates, limiting the use of PbAs in advanced applications that require repeated deep discharge/charge cycling. A deeper understanding of the atomic-level mechanisms that control additive-lead species interactions is necessary to optimize expander molecules for both discharge and charge performance. A collaborative project between government, academia, and industry has screened over one hundred model expander molecules (MEMs) using cyclic voltammetry, density functional theory, and various spectroscopy methods to characterize their chemical and electrochemical stability and performance properties. The MEMs are categorized by their lignin structural motifs and the presence of functional groups, e.g., sulfate, sulfonate, and carboxylate, with the goal of establishing structure-function relationships. Discharge (DEF) and charge (CEF) enhancement factors were established as the metrics for electrochemical performance relative to sulfuric acid without expanders as the baseline. Four categories of expander molecules were defined based on their DEF and CEF values: traditional, e.g., Van A, inhibitors, enhancers, and rheology modifiers. The set of materials evaluated to date demonstrates that expander molecules that can enhance both the discharge and charge performance are possible and do exist. On the other hand, the inhibitor class may lead to a deeper understanding of the expander degradation processes and their impact on cycle life. These results help us identify the design rules for expander molecules targeted to advanced PbA applications.

Design, synthesis and structural evaluation of model expander molecules for advanced lead-acid battery storage applications

Madhu Chennapuram, The University of Toledo, Winner

Lead acid batteries provide a day-to-day reliable energy storage application in various fields like automotive, standby power, renewable energy, telecommunication, industrial and robotics. 1 In addition to the electrochemically active lead species, these batteries contain a number of additives that improve performance and cycle life. Lignosulfonates (LS) are organic biopolymers that are used as additives in a variety of applications, including the production of lead acid batteries (Figure 1) 2. In lead acid batteries, LS serve as organic expanders to improve the performance of the battery’s storage capacity and extending its service life, as well as by acting as a wetting agents and improving the conductivity of the electrolyte, which tends to improve battery efficiency. 3 To be able to understand the interaction of specific functional groups with lead species in detail, small molecules that mimic portions of LS can be used as model expander molecules (MEMs). In this study, we are designing and synthesizing lignosulfonate-based MEMs. A series of MEMs were prepared from different synthetic methods (Scheme 1).  The MEMs’ stability under conditions relevant for battery applications was investigated by cyclic voltammetry in 5 M H2SO4. Additionally, the interaction of the MEMs with Pb2+ and their stability at elevated temperature and in 5 M sulfuric acid was studied by spectroscopic and diffraction techniques.