I attended a seminar given by the Duracell folks years ago. I don't recall much of it, but a salient point was the challenge of stabilizing that much chemical energy in a limited volume. They had potential chemistries that were impressive, on paper, but simply unstable, or they had other issues (recharge time, deep cycle issues, etc.)
And cost of course.
We were supposed to collaborate with them, but as is usually the case, smart people don't often have decent ideas in a field they don't know where other smart people have worked for decades.
Not being a smart people I sat on my hands.
Not many takers for my nuclear proposition, which I think is a sign of the obvious.