Energy density has a fixed upper bound for any given battery chemistry: the amount of energy that would be bound/released if all of the material in the battery

Energy density has a fixed upper bound for any given battery chemistry: the amount of energy that would be bound/released if all of the material in the battery would participate in a cycle by turning from one state to the other and back. The amount of energy per reacting molecule/mol/kilogram is fixed and well known. Someone who is not as terrible at chemistry as me won't find or hard to come up with concrete numbers. And those numbers are hard constants, you can only come closer to them (within a given battery chemistry), they are impossible to exceed. And another angle: our perception of energy density increase is heavily disturbed by the much faster reduction in cost, we are just not very good at telling those two apart.