This isn't a thermal option, but the iron-air chemistry has promise too. It's basically rusting and de-rusting iron. Much more environmentally benign than lithium ion, and likely way less expensive. AFAIK, this company is the frontrunner: https://formenergy.com/technology/battery-technology/
If so, the metal-air systems have a major advantage on the discharging side of things by avoiding the need of a fuel cell and being able to harvest electrons directly via galvanic current.
The galvanic discharge rate is extremely slow and not really suitable as part of a rechargeable battery system. Any practical metal-air will have some way of discharging faster. The problem is that we have basically solved this for hydrogen-air but not for anything else.