One of the trade offs is that engines are actually ridiculously heavy. Compact, extreme high power electric motors are starting to be commercialised. But also, fuel burns so you lose weight as you’re flying whereas batteries stay the same.

Electric aviation is interesting but as someone who knows a bit about the industry, biofuels make more sense here.

Structural batteries were supposed to be the solution where the density wasn't so important. I don't really have a good understanding of the ration of fuel weight to structural weight in existing aircraft though.

Jet engine and wing efficiency have increased enormously over the last 50 years.