Correct. Liquid or gel electrolyte makes a battery non-solid state. The goal is to have a battery where you can't have "tin whiskers" grow between the two halve

Correct. Liquid or gel electrolyte makes a battery non-solid state. The goal is to have a battery where you can't have "tin whiskers" grow between the two halves, which is both a safety hazard and puts a limit on how fast they can be charged.