If solid state batteries are decades away at scale, then so are...

If solid state batteries are decades away at scale, then so are a new fleet of Toyota BEVs. Toyota is using solid state batteries.

Yes you can use lithium in solid state batteries. You can also use any other metal ion you want.

Lithium unlike the transition metals only has one crystal spin state. If weight or ion size is no longer a significant reason to use lithium (as they can't move through the thin layers, we're not making a semiconductor) then Vanadium has EIGHT oxidation states. Sulfur has NINE.

Even a concept like V, S-doped thin layer solid state batteries should give a pause for concern.