Yeah, I've seen several of Donald Sadoway's long talks, that is promising tech, the iron-flow and liquid-metal batteries. The only problem for nearer future I see, is they are currently geared toward large-scale energy storage (of course they have to honor where they can get research money for it to get going), but it'll be awhile before you could get one for your backyard.
Don't get me wrong, this is a huge global problem we need to solve, the power companies need to be able to store the energy for all the intermittent solar and wind they collect (for nighttime use, or lack of wind), before it makes practical sense for them to scale larger with renewable sources. So the focus is going to be on large-scale industrial application for awhile anyways.
I hope they can work something out sooner rather than later for the consumer market, but for now it doesn't make a lot of financial sense for them to pursue consumers, they can make so much more money by bringing the technology to the power companies. This is kind of like big oil in that sense. But also, the opportunity to make larger contribution to pollution control and cleaning the air is greater as well, so not like big oil in that sense...
But I do think you're right about this being a game-changer for battery storage, because they already have working systems out in the field at tester sites. I did try to email Ambri a few months ago, to enquire about a large 'storage container' battery for our off-grid ag coop ranch (for community-level use), but they never replied back to me, maybe we're not big enough.
I got my hopes high though, and have my eyes on this one