Batteries are polluting yes, but they are very much net carbon negative, especially lead acid as most of the lead is recycled into new batteries.

The process of recycling lithium is a bit harder and not used as much.

I like this idea, but with gas prices still too low it doesn't make economic sense. Maybe with a proper carbon market this would change. If you are using a hydrogen process in existing pipelines you would be burning carbon neutral energy and this would entice people to develop large offshore wind developments to feed into these existing pipelines.