There's some interesting companies in this space. https://gofourth.com/ https://gofourth.com/ - focusing on grid storage, uses graphite (carbon) and liquid tin

There's some interesting companies in this space. https://gofourth.com/ https://gofourth.com/ - focusing on grid storage, uses graphite (carbon) and liquid tin for heat transfer https://antoraenergy.com/ https://antoraenergy.com/ - industrial heat and electricity https://rondo.com/ https://rondo.com/ - industrial heat You can find interviews with their founders on the Volts podcast.