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I read with interest your article on batteries and learned a lot more.   Please do you have the answer
to the following questions :

a) Since cathode electrodes are coated with PbO2 (s), how is this product ( PbO2 ) obtained. Is it a natural
product or does it need to be chemically produced. What is therefore the equation of the chemical reaction
and under what conditions is the reaction possible.

b) Is there any technique for coating lead with PbO2. I understand both products are solids.

c) Is the voltage of the lead acid battery you described in your interesting article predictable? What is
therefore its value? Is this value constant during the discharge period?

d) I read somewhere that lead reacting with oxygen produces the following products : PbO, PbO2, Pb3O4.
Do you have any idea on the conditions needed for obtaining those leads oxides? Are they rather found
in nature? in which state ( solid, liquid or gaseous ?)

                           

a) General information about PbO2 (lead dioxide) at: NIST Webbook
Lead is usually found in nature as PbS in an ore called "galena". When the ore is roasted with oxygen, the reaction:
2PbS + 3O2 --> 2PbO + 2SO2
occurs. I don't know the reaction temperature or pressure though. Once you have PbO, it would probably be reacted with an acid or perhaps even water to obtain PbO2. Again, I'm unsure of the exact reaction and the conditions. Notice that the sulfur gas in the first reaction would have to be scrubbed out and would probably be reacted with water to form H2SO4 which is a saleable product.

b.) The coating would be attached by simple melt dipping or electroylsis outside of the battery during the production. Since this reaction is reversible as in rechargeable batteries, the PbO2 must "voluntarily" attach itself to the lead cathode..otherwise the reverse reaction wouldn't be feasible.

c.) Lead battery voltage is very predictable, that's why we use it in batteries (it's certainly not environmentally friendly, so there had to be some motivation for using it). I expect that the voltage is related to the speed at which the ions travels through the electrolyte (H2SO4). I think that is the key value considered when an electrolyte is chosen for a battery. The voltage is not a constant throughout the life of a battery....ever hear a tape player operate on "dead" batteries...they tend to slow down due to the decrease in voltage. If the value was constant, batteries wouldn't "slow down", they would simply cease working without notice. Voltage from lead based batteries range from 6, 12, 24, 32 volts.

d.) I'm not familar with Pb3O4, but you can see where the other two products come from. (the ore mentioned in part a.) Again, I'm not sure of the reaction conditions.

Wow, hope I helped a little. If you're really interested in battery technology, you may want to turn your attention from lead batteries to photovoltaics or fuel cells, they're much more interesting....but no one should be held at fault for increasing their knowledge. Good Luck