BCI Battery Poster Research Showcase

Students will contribute to the scientific community’s research of battery innovations during the BCI Poster Research Showcase hosted at the 2024 Battery Council International (BCI) Convention & Power Mart Expo in Fort Lauderdale, Florida, April 21-24, 2024.

This poster experience is intended to support researchers in university, governmental and commercial settings in building awareness about the scientific opportunity and objectives of careers in battery technology, preferably with a focus on lead, and to share cutting-edge science and technology across this critical industry. Current entrants for this year’s showcase include:

Fundamental Studies of Lead Acid Batteries – Discharge Mechanism and Capacity Limits of Positive Active Materials

Frederick Agyapong-Fordjour, Argonne National Laboratory

The irreversible transition to clean renewable energy requires the deployment of energy storage systems at unprecedented scales. Lead batteries have the potential to continue serving as a crucial energy storage technology for a sustainable decarbonized energy economy because it is earth-abundant, inexpensive, and 99% recyclable. To advance the design of lead batteries with higher material utilization, fast recharge rates, and long-cycle life, will require a fundamental understanding of the electrochemical and chemical processes happening at the atomic and molecular scales. Here we discuss how the use of well-defined lead electrodes allows us to gain insights into the fundamental limits of discharge capacity and recharge rates. We unveil the relationships between discharge rates and PbSO4 particle size/layer thickness that ultimately governs the maximum discharge capacity accessible as a function of discharge rate on both the negative and positive lead electrodes. This data helped us develop a mathematical model that captures the key processes concerning lead ion and (bi)sulfate ion gradients coupled to nucleation and growth that explain, from first principles, the origin of the well-known empirical Peukert law. In this context, we explored how variables such as acid concentration, temperature, and the presence of lignosulfonate additives in the electrolyte further influence discharge capacity, allowing us to understand how thermodynamic, kinetic, and mass transport play a huge role in controlling the accessible capacity of the electrodes. This study paves the way for an in-depth understanding of the important variables in designing a lead acid battery performing at its full potential.

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

Cailin Buchanan, Argonne National Laboratory

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

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.

Non-stoichiometry and its influence in the Positive Active Material and Corrosion Layer of Lead Acid Batteries

Tiffany Kinnibrugh, Argonne National Laboratory

The malleable nature of lead oxides ranging from PbO to PbO2 plays a significant role in the positive electrode of lead batteries. Drawing from decades of thermal studies, engineering a conductive PbO1+x phase in the corrosion layer is necessary to avoid premature capacity loss driven by stoichiometric PbO. Within the active material, both α- and β-PbO2 are thought to be nonstoichiometric, with both oxygen [2] and Pb vacancies that are accompanied by proton interstitials[1]. The importance of non-stoichiometric retention was found in a neutron study which monitored the lead site’s vacancies in the PAM for conventional and fast charged batteries and showed a decrease from βPbO2 stoichiometry through the first 250 cycles with the fast charged battery continuing 750 cycles further than the conventional battery[3]. Our work sets out to provide a better understanding of non-stoichiometric phases and the conditions where they form to improve battery life and performance. We revisited PbOx phases associated within the corrosion layer using in situ diffraction and x-ray absorption and found the presence of metastable Pb3O5 and Pb2O3 phases during thermal decomposition of β-PbO2. Separately, changes in the stoichiometry of β-PbO2 in an electrochemical environment were also investigated using in situ diffraction during cycling of a Planté cell at oxidizing conditions. Both studies were supported by density functional theory calculations which provide context on the overall stability and structure of these phases and the origins of their electronic and oxygen mobility.

Advancing Lead Acid Batteries: Comprehensive Insights into the Evolution of Active Materials and Interfacial Processes through Multimodal Analysis

Vijayakumar Murugesan, Pacific Northwest National Laboratory

The lead-acid battery is a time-tested and robust rechargeable battery technology that has withstood the test of time and is still widely applicable owing to its reliability and high power-to-weight ratio. However, its integration into grid-scale stationary energy storage applications faces challenges, as its performance lags newer battery chemistries. The charge-discharge cycles in lead-acid batteries involve multiscale chemical, morphological, structural, and microstructural evolution, driven by repeated dissolution-nucleation-precipitation of active materials under an applied electric field. Understanding these interfacial-driven processes at the atomistic and molecular scales, as well as elucidating the role of additives facilitating these multiscale transformations, are crucial for enhancing battery life and performance. At PNNL, we have adopted a multimodal analysis approach to uncover the underlying mechanisms occurring at the electrode-electrolyte interfaces in Pb-acid batteries. By utilizing a combination of in-situ and ex-situ tools, we address the most challenging issues surrounding the dissolution-nucleation and phase transformation regimes of active materials. This presentation will discuss our efforts to provide atomistic insights into PbOx phase evolution during in-situ heating, PbSO4 nucleation over native and strontium-doped barite surfaces, and the ion dynamics of sulfuric acid-based electrolytes, all derived from our multimodal analysis. Our goal with these multimodal analyses is to establish a predictive regime for designing active materials with outcomes that can withstand the harsh demands of grid-scale stationary energy storage applications.

Evaluation of Model Expander Molecules in Lead Batteries

Sahar Nazeer, University of Toledo

Lead acid batteries represent the oldest rechargeable battery technology, still widely used. In addition to automotive applications, exploring their application for large-scale energy storage is desirable. However, the sulfation process in the battery is affecting its charging capacity and performance. Lignosulfonates, which are also referred to as “negative expanders”, are used as an additive in lead acid batteries to overcome some of the issues related to sulfation. Negative expanders perform versatile functions in batteries. They affect the morphology of lead sulfate crystals, the rate of oxidation of lead sulfate, and reduce the sintering of the porous active mass. Lignosulfonates are complex molecules with multiple functional groups, but which functional group interacts with the battery component and improves the performance is still unknown. So, model expander molecules that resemble the various groups of these commercial expanders were synthesized instead. The main motivation of this project was to analyze these interactions and how these interactions can be exploited to enhance the performance of lead batteries. In this research, the synthesis of various MEMs was accomplished by alkylation and sulfonation reactions. The purity of the MEMs was characterized by proton nuclear magnetic resonance (H-NMR) spectroscopy and elemental analysis. Moreover, electrochemical properties were investigated by Cyclic Voltammetry. Their effect on the charge/discharge behavior of lead electrodes in 5 M sulfuric acid was studied by collaborators at Argonne National Laboratory, and several compounds were found to improve charge, discharge, or both.

Novel Characterization of Pb-acid Materials Utilizing XRM paired with Micro-CT

Grant Spencer, University of North Texas, Department of Materials Science and Engineering

Lead-acid (Pb-acid) battery cells are a growing electrochemical choice for renewable energy grid-storage, while remaining the premier choice for combustion engine start-up sources. Up until recently, very few non-destructive experimentation techniques have been utilized for Pb-acid cell characterization – such techniques are useful to identify performance-defining heterogeneities that may develop within a cell during electrochemical cycling. X-ray microscopy (XRM) is a non-destructive, advanced characterization technique that, when paired with micro-computational tomography (µCT), renders 3-dimensional images that can be utilized to analyze features with resolution dimensions as small as 700 nm, depending on sample material, thickness, and geometry. This study applied XRM with µCT to analyze Pb-acid minicells and such performance-defining heterogeneities that might develop under voltametric cycling, such as secondary phase growth and evolution, and crack and porosity formation, as well as inclusions. Utilizing ORS Dragonfly software for 3D image refinement and final stage analysis, large phase transformation was recognized for the Pb-paste within the cell between initial and final volumes, when considering secondary phase growth. Feature sizes with resolutions of 4-5 microns were observed using the NDE technique. Due to XRM’s large depth of field, this technique is considered advantageous for region of interest analysis for more in-depth studies involving Pb-based materials, that include smaller feature sizes, below submicron range, as well as for a selection stage for region of interest investigation utilizing scanning electron microscopy (SEM) or transmission electron microscopy (TEM), which was utilized for investigation of features with nm sizes.

Effect of Model Expander Molecules on the Morphology of Lead Sulfate Crystals

Radha Shah, University of Toledo

Rechargeable lead-acid batteries have found widespread use over the past century, with applications ranging from the commonly encountered SLI (starting, lighting, ignition) batteries in motor vehicles to applications like backup power storage for critical infrastructure. The global drive to reduce dependence on fossil fuels and increase the use of renewable energies requires the development of vast amounts of reliable and safe energy storage. Lead batteries are attractive for such applications because of the high abundance of raw materials, excellent recycling of spent batteries, reliability and safety. However, current batteries suffer from limitations during deep discharge or rapid charging, which must be overcome if they are to be used for grid storage.  During the discharge of lead-acid batteries, lead sulfate forms on both the negative and positive electrodes of the battery; this is a process known as sulfation. The morphology of the lead sulfate particles has a strong effect on the reversibility of this process when the battery is recharged. It is known that problems for battery life arise when coarse, needle-like lead sulfate deposits form on the electrodes of the batteries. Such deposits contribute to gradual inhibition of the battery.  The electrodes in lead-acid batteries contain additives to the electroactive lead species that improve the cycling performance of the batteries. These include carbon, barium sulfate and lignosulfonates (LS), which are referred to as expanders. The presence of these compounds affects the morphology of the lead sulfate particles formed on the electrodes, and through this the ease of reversing the initial discharge reaction. LS are known to enhance discharge rates several fold, but interfere with rapid charging. However, it is not known what functional groups on the lignosulfonates play specific roles in this process. Smaller molecules that mimic specific functional groups on lignosulfonates, which are referred to as “model expander molecules” (MEMs), can be used to explore such effects in more detail. In this poster, the effect of MEMs on the morphology of PbSO4 was explored by carrying out precipitation reactions by controlled addition of Pb2+ and sulfate solutions. Scanning electron microscopy was used to evaluate differences in morphology, while phase identification and evaluation of crystallinity was carried out by power x-ray diffraction.

Nucleation and Growth of Barium Sulfate as a Proxy for Lead Sulfate in Lead-Acid Batteries

Andrew Stack, Oak Ridge National Laboratory

Lead acid battery charge and discharge rates and efficiency likely depend in part on the texture of lead sulfate crystals. That is, the distribution, size and plate-connectivity of the crystals during their formation in the discharge cycle likely influence their dissolution rates during the charging cycle. Here, we use the precipitation of a natural material, barium sulfate, as an analog to establish a fundamental basis to understand how lead sulfate texture might be affected by the rate of nucleation and growth, as well as additives to solution, such as electrolyte ions. The work may have provide some guidance on a strategy to tailor lead-acid battery composition and cycling characteristics for specific applications.