Salt batteries are really bad, but, you know, at least they’re salt. I don’t know much about salt batteries at the expert level, but I also work on an e-chem system that is low current low density. There’s definitely applications, especially because materials and tanks are cheap, but it turns out power is stupid cheap as well.
I don’t think anyone can really predict a new “winner” right now, but it’s the biggest reason why I’m a proponent of electronification in general; we absolutely won’t be tied to Lithium forever.