metal-air fuel cells are in many respects even better. And with metal content around 50% they become weight comparable or better than 30% efficient ICE.

In that case you have lithium oxide to take care of and you have heavier plane with each second (of course most of the fuel is wasted on lifting the plane, so it may be better)

the electric planes, at least at first, isn't about just swapping ICE for electric. It is about building different planes. The current planes have evolved significantly under the limitations of ICE. The electric planes, at least initially, is about short-hoppers ("flying car" like functionality) where ICE is a no-go because of cost and noise. The electrics are well suited to build STOL and VTOL (multi-copters). With years the electrification can make its way through various hybrid schemes into much more efficient long-haulers.