Isn't this what Quantumscape is already betting on ?
I've heard nothing about them for a solid 16 months, so I'm guessing the shorters were right.
Solid State batteries appear pretty easy to crank out a demonstration cell with lots of density advantages over the production cells, and handwave away the scaling of production as a detail resolved in investment. There are a solid dozen companies I've seen with that basic approach.
None of the solid state companies appear close to scaling production.
Likely the sulfur chemistries will beat them to market with far superior material cost and density and scalability. Solid state still has a good opportunity in cell phones / laptops / etc, which is a big market, but the real play in batteries is grid storange and tranportation, which will dwarf phones/laptops by several orders of magnitude in volume.
Not sure where people got the idea that they claimed they are on the verge of large scale production.
They were on a little bit more then lab scale production.