Batteries are always based on chemistry. But since you said that portable device batteries today are little-changed from 40 years ago, I wanted to point out tha

Batteries are always based on chemistry. But since you said that portable device batteries today are little-changed from 40 years ago, I wanted to point out that the lithium ion battery is newer than that, and still improving. That's why cordless saws and leaf blowers are practical now but weren't practical 40 years ago. Better batteries made them work. They didn't benefit from Moore's Law.