Dr. Pietro Lopes, Electrochemist Scientist, Argonne National Laboratory
Lead batteries have the economical potential to serve as a key energy storage technology for a sustainable energy future powered by renewable energy. Despite lead abundance, low commodity level cost and robust industrial base with 99% recyclability rates for current lead battery technologies, improvements in material utilization (discharge capacity), rechargeability and cycle life are paramount to truly enable lead battery use in grid energy storage, particularly for long-duration energy storage (LDES). While continuous progress in battery performance has been achieved over the past few decades, a step change in performance and durability is required, which drives us to re-examine the electrochemical and chemical processes of both negative and positive electrodes at the fundamental level. In this talk, we will focus on new insights about the discharge and recharge process in lead batteries gained from studying well-defined lead, lead dioxide and lead sulfate-sulfuric acid interfaces. Through an electrolyte-mediated dissolution-precipitation mechanism we discuss how the maximum discharge capacity attained at either negative or positive electrodes is defined by the surface passivation process from the nucleation and growth of lead sulfate layers over the active materials surface. In turn, we were able to derive from first principles the well-known Peukert relationship between discharge capacity and discharge rates. By exploring the influence of temperature, acid concentration and the presence of lignosulfonate molecules we were able to shed new light on how thermodynamic, kinetic, and mass transport effects regulate the lead sulfate layer thickness and consequently the maximum discharge capacity. By exploring the role of the lead sulfate layer thickness as well as particle size from well-defined chemically synthesized PbSO4 we were able to reveal how the kinetics of the chemical dissolution step is the rate-determining step governing the recharge rates. We will then conclude by demonstrating how the understanding of the discharge limits of lead batteries creates new opportunities in the design of advanced expander molecules that can enhance both the charge and discharge properties of negative lead battery electrodes.
