The nitrate mite combine, or the chlorine ion (an ion is a part of hydrochloric acid, as the nitrate ion is part of nitric acid, both "charged" with electron, the one that is conducted, through the battery cables, to the starter etc.) might also and( deeper theory excepted ), suggests an interesting experiment... ALL SAFTY PRECAUTIONS ARE NEEDED AND ONE MUST HAVE A REAL EXPERT STANDING BY ! Of course.
To do it right, of course, one should start with an unsulfated one, one without ether sulfuric acid nor 'sulfation' ( not lead sulfate embedded plates; just pure lead), perhaps hard to come by. I'd be very interested in your results: A) Would it work?, b) How much charge would it hold? C) Would it take a charge? D) in a resonable time? E) without OVER HEATING ( WITCH IS THE SECOND WORST DANGER { AFTER DEALING WITH WITH VERY(!) CAROSEVE CHEMICALS } ) [ YOU NEED PROFESSIONAL TRAINING].
Drop me a line if you persew this, would you?