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Hydrochloric acid, as well as nitric acid, are also strong acids like sulfuric acid. So, why are not they used commercially in lead-acid batteries?

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    $\begingroup$ HCl and HNO3 can't be used because they both would participate in redox reactions. $\endgroup$
    – Ivan Neretin
    Dec 13, 2016 at 19:52
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    $\begingroup$ @DwiparnaDatta Well, there is a relationship between the cell voltage and the acid used, but for numerous reasons (like the redox participation mentioned by Ivan) the identity of the acid used has a huge effect on Pb-acid battery performance, far beyond just the achievable cell voltage. $\endgroup$
    – hBy2Py
    Dec 13, 2016 at 19:55

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In the lead battery it is very important that the electrodes transform into insoluble lead sulfate when discharged, especially at the cathode where lead(IV) oxide is turning into lead(II) sulfate. Consider the two half reactions of the lead-acid battery:

$$\ce{Pb(s) + HSO4−(aq) → \color{red}{PbSO4(s)} + H+ (aq) + 2e−}$$ $$\ce{\color{red}{PbO2(s)} + HSO4−(aq) + 3H+ (aq) + 2e− → \color{red}{PbSO4(s)} + 2H2O(l)}$$

Lead nitrate is soluble, so metal ions would go into solution. The lead(IV) oxide would not form again from these ions on charging, metallic lead from the electrode would dissolve. The battery would no longer be rechargeable.

Lead chloride is insoluble, but lead(IV) oxide on the cathode would oxidize chloride into chlorine. Thus no more battery.

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Along with the battery issues identified by Stapke, there is the matter of toxic emissions. The lead-acid battery with sulfuric acid just undergoes reactions involving the lead and gives contained, nonvolatile products. By way of contrast, hydrochloric acid could be oxidized to chlorine gas at the anode and nitric acid could be reduced to nasty nitrogen oxides at the cathode. We would not want such fumes coming from car batteries, especially when we already have to deal with the exhaust from most cars burning gasoline.

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