Every battery is like that (one in the video) The only difference you're missing is the tin casing around it.
Did you know Polaroid cameras use that same type of foil battery? And did you ever think about WHERE in the camera that battery is?
Here's another one, did you know that a 9V battery has 6 tiny (AAAA?) 1.5V batteries inside?
And no that is not a capacitor, those don't hold charge long enough to be used as batteries.