You're a techno-optimists making claims of certainty about the future based on your ideas. Fact is, it's not being used now for a reason. Such exoskeletons have been around for over 25 years, and have not come to fruition.
Claiming they must, that it's certain, when they haven't is a faulty corporate logic, on par with "LLMs will be super intelligent one day" and "we're in the singularity all technology will keep becoming infinitely better"
Battery density is ultimately a hard problem. Physics and science has limits. Expecting those to be traversed just because you have beliefs or really like a technology. Is foolish.
There's literally hundreds of "next gen battery" claims each year that don't pan out. Go look how many times a salt-battery has been attempted. Some problems are more difficult than infinite growth techno-optimists realise.