Substitution Effects on Nucleation and Crystal Growth of Lead Sulfate on Barite for Battery Applications

The common and widespread use of lead-acid batteries is due to the reliability and cost-efficiency of this energy storage option. These batteries contain a Pb anode, PbO₂ cathode, and a microporous separator, all saturated with H₂SO₄ electrolyte. The common failure mechanism of “hard sulfation” involves the irreversible large crystal growth of non-electroactive PbSO₄ on the surface of the anode. Expanders are chemical additives, such as BaSO₄, used to uniformly distribute PbSO₄ nucleation sites and to minimize hard sulfation in the battery. Our studies combine methods using both <i>in-situ</i>, <i>ex-situ, </i>and<i> in-operando</i> imaging using 3D optical microscopy during electrochemical cycling to observe and better understand the nucleation and growth mechanisms of PbSO₄ on crystals of expanders BaSO₄ and Ba_1-xSr_xSO₄. Fine tuning the ability of expanders (by Sr-substitution) to limit large crystal growth of PbSO₄ may improve overall lead-acid battery cycling.