This talk by Dr Sadoway is pretty amazing regarding his team's design for utility-scale liquid metal batteries: https://www.youtube.com/watch?v=NiRrvxjrJ1U It's an hour long, but it's well worth the time investment.

This is not merely a theoretical technology. A company has been created around this technology: http://www.ambri.com

(I am not connected to any of this, but I am quite excited by it.)