I have some batteries labelled as Extra Heavy Duty with a picture of a trashcan and the letters Pb for lead, and an x over the trashcan which I believe means not to discard in the trash. The batteries also say not for retail sale, so I suspect that they were the original batteries in some children's toys from which I pulled them out. I found on the web that the likely chemistry is zinc chloride, and I don't see any lead in the chemical reaction.
What is the source of the lead? Is it just impurities in the zinc, as can occur with zinc-galvanized hardware? I know that in the galvanization process lead is added to the kettles for metallurgical reasons. Is there something similar going on here?