Re: Pollution impact
Batteries are not a huge problem from an environmental impact viewpoint and anyway I expect that carbon based super-capacitors will start to become common in about 5 to 10 years at which point you could simply burn them when you want to dispose of them.
Lithium batteries in cars now appear to last much longer than everyone was worrying about a few years ago and I think average battery lifetime in a car will probably exceed 10 years. After this point the battery will not be able to deliver the high peak power that a car needs but it will certainly be good enough for grid or home power storage probably for something like another 15 years.
Try doing that with a second hand car engine or fuel tank!
 Well, apart from digging the lithium out of the ground that is.