Comment by dirck-norman

The only thing different from this list is the ceramic separator. It’s not polymer. However, the ceramic is ultra thin to the point that it’s flexible so volume expansion isn’t a problem and it solves the dendrite problem.

Perhaps a polymer will be invented that can’t be pierced by dendrites. But existing polymers need to be heated for ion transfer efficiency and are combustable.

Technically, QuantumScape also uses an organic liquid catholyte inside the cathode. So it’s not “pure” solid state.