PbSO4 is a key component in the charging and discharging of lead acid batteries—such as the cycling of automotive batteries. PbSO4 is a poor conductor that forms on the positive and negative electrodes during discharging and dissolves during charging of a lead acid battery. Over time, buildup of PbSO4 occurs on the electrodes, ultimately reducing the efficiency of the battery. This study aims to determine the nucleation and growth mechanisms of PbSO4 nanoparticles in various solutions to potentially reduce or control the buildup of PbSO4 on battery electrodes over time. The time dependency of particle morphology was observed using various reaction conditions. PbSO4 particles were created using premixed solutions at various times of reaction. H2O, acetone, methanol, ethanol, and isopropanol were used to stop the reaction and development of the PbSO4 particles. The structure of the nanoparticles was characterized via transmission electron microscopy, high-angle annular dark field scanning transmission electron microscopy, and selected area electron diffraction. This study provides insight into the mechanism by which PbSO4 nanoparticles form in various solutions and reveals that the degree of complexity of the solution plays a large role in the nucleation and growth of the PbSO4 nanoparticles. This insight can provide avenues to reduce unwanted buildup of PbSO4 on battery electrodes over time, which can extend battery life and performance.

During battery discharge, HSO4– ions migrate to the negative electrode and produce H+ ions and PbSO4. At the positive electrode, PbO2 reacts with the electrolyte to form white PbSO4 crystals and water. Both electrodes are discharged to PbSO4, which is a poor conductor, and the electrolyte is progressively diluted as the discharge proceeds. As the cell becomes discharged, the number of ions in the electrolyte decreases and the area of active material available to accept them also decreases because the plates become coated with PbSO4. On charging or converting electrical energy to chemical energy, the reverse electrochemical reaction occurs. The electrodes are converted back to Pb and PbO2 plates, while the electrolyte increases its H2SO4 concentration. Buildup of PbSO4 forming on battery plates is a process known as sulfation, and it occurs naturally over the life of the battery due to the electrochemical reaction that occurs in the battery. Other variables can increase sulfation such as battery overcharge or battery storage in a high-temperature environment. This process is important to study due to PbSO4 crystals being a poor conductor. The crystal size and solubility of these crystals in the electrolyte affect the current in the battery, where crystal size plays a larger role in this effect.

Efforts have been made to optimize the electrochemical reaction by studying the sulfate material created in the batteries to improve overall battery performance. Based on these efforts, it is clear that the surface structure and morphology of the sulfate are an important factor in improving battery performance. The surface properties of the sulfate crystals depend on the crystal faces that are exposed and their relative sizes, which both correlate to engineering desired surface properties, i.e., catalysis of sulfate crystals in a battery. Additives have also been shown to modify the structure and size of crystals that grow during the formation process in these battery cell reactions. PbSO4 formation has been observed to occur through a dissolution/recrystallization mechanism. This process proceeds at the solution/crystal interface, so the PbSO4 crystals that form have well-pronounced walls and edges. Sulfation of lead-oxide pastes has been reported to depend on the size of the lead-oxide crystals. While many studies have examined the microscopic behavior of these PbSO4 crystals, few studies have examined the nanoscopic behavior of crystals at the onset of formation. Moreover, fewer studies have investigated the effect of various solutions on nucleation and growth of these PbSO4 crystals at the nanoscale.