Well, the theoretical floor is much further if one goes beyond Lithium. There are various prototypes that oxides aluminum potentially reaching energy densities

Well, the theoretical floor is much further if one goes beyond Lithium. There are various prototypes that oxides aluminum potentially reaching energy densities greater than gasoline. Now, those are currently only reversible in the sense of using aluminum smelter to restore aluminum from the oxidized form. Still we do not know if reversible process is not possible at all in a compact device and the supply of aluminum is vast.