Final answer:
During battery discharge, lead (Pb) is the species that is oxidized.
Step-by-step explanation:
During battery discharge, the species that is oxidized is lead (Pb). In the lead-acid battery reaction, the lead (Pb) atoms lose electrons and are converted into lead (II) sulfate (PbSO₄) during the discharge process. This oxidation reaction occurs at the anode, which is the negative electrode of the battery. The lead (II) sulfate (PbSO₄) that forms during discharge accumulates on the plates within each cell of the battery.