Compressing neon gas won't do much, aside storing energy as compressed fluid. My point was the traditional fuels (incl. the edible ones) use more material/weig

Compressing neon gas won't do much, aside storing energy as compressed fluid. My point was the traditional fuels (incl. the edible ones) use more material/weight than their own. So it is very likely they'll be more efficient. The batteries require a reversible action by just applying current - this is quite the climb compared to most chemical reactions. We have not done much since the li-ion inception, using FePO4 instead of cobalt is more sensible from an economic point of view but the energy density is even lower.