The technology is reportedly ten times cheaper than lithium-ion batteries and far more powerful and efficient than any other thermal battery.
Which isn't saying much, really. It exposes "solar" cells to the white hot bricks to regain the energy, but that's going to be maybe 30% efficient. It also uses tin as the heating fluid, at least in the prototype, which is (in spite of popular confusion) a very rare metal.
It's an interesting idea, but I doubt this is going anywhere. Even pumped water or solid weights seems more practical, and sodium ion battery is apparently coming on the market as an option.
Heat in general seems like the shittiest way to store electricity. The real application there is when you wanted heat anyway, like that cement plant (I think?) in Finland that keeps a tower superheated with renewables and then blows air through it into the kiln.