Energy density alone is a misleading metric, because what matters is how much energy actually gets delivered to the drive mechanism. It's actually not that hard

Energy density alone is a misleading metric, because what matters is how much energy actually gets delivered to the drive mechanism. It's actually not that hard to beat gasoline, because despite its excellent energy density, gasoline engines are only 30% efficient. First and foremost a gasoline engine is a machine for producing heat and noise, and only incidentally for producing forward motion.