[sc_rufctr]

It's certainly possible (easy) to cut open a battery and neutralize the acid...

But reclaiming the lead is not easy to do safely.

You have to heat the plates with a blow torch or something and let the lead drip off into a container.
Now this is the dangerous bit... The thing is as you do this there will be vapor in the air coming off the molten lead and you don't want to breath this stuff in.
So you need a full face mask with an independent air supply like they use in a 2pak spray booth.
You can get a face mask with a filter rated for metallic vapors but these are not easy to find. >>> If it was me I would go with the full face option.

While you're considering this it may be easier to buy some lead in a block form and melt it down yourself for bullet making.

I used to make my own fishing weights from lead when I was a kid and we followed some simple rules like standing upwind so we wouldn't poison ourselves.
I'm not sure you could get away with that today. Lead poses special problems for kids developing brains.