If muln were anywhere close to developing a real solid state battery that could do what muln says it could do. Then the world would be beating a path to their front door and trying to make all kinds of partnerships and license deals, or trying to acquire muln (would be easy for a Tesla or other big company to get controlling stake in muln if they wanted, stock is cheap and there are no >10% holders).
Instead, what do you hear about Mullen from others in the industry? Crickets, absolutely nothing. Because muln has absolutely nothing. They just issue press releases with no proof.