Sulfate Alteration of Lead Acid Batteries

Lead-acid batteries (accumulators) are rechargeable devices for storing electric energy generated by electrochemical processes. The batteries consist of electrodes made of lead (Pb) and lead dioxide (PbO2) and dilute sulfuric acid (37% H2SO4) as electrolyte.

During discharge of lead-acid batteries, finely dispersed lead sulfate (PbSO4) forms on electrodes in a process that is reversed by recharging. However, sulfation, a permanent alteration process characterized by the formation of coarse crystalline lead sulfate deposits, may lead to progressive inhibition and power loss of the battery until complete failure upon short-circuit. The nature, kinetics and spatial distribution of these crystalline deposits is thus of major research interest for battery manufacturers as well as for developers of technologies preventing sulfation. X-ray element maps are ideal for investigating the nature and spatial distribution of sulfation deposits.

QUANTAX WDS is a powerful analytical tool which can well resolve X-ray overlaps of Pb and S and therefor determine the nature and spatial distribution of chemical phases generated during battery alteration.

X-ray element distribution map for S and Pb acquired on an electrode of a lead acid battery
Section of the X-ray spectrum for lead sulfate showing the high spectral resolution of WDS in contrast to EDS