Theory 82/Energy Limits/Batteries
Energy Density Is a Chemistry Ceiling
The claim
Battery energy density is capped by the ratio of cell voltage to the mass of the redox couple, so chemistry sets the ceiling and engineering only approaches it.
01Mechanism
Energy is charge times voltage per unit mass; both terms are set by the couple, and packaging adds mass that lowers the achievable value.
02Prediction
Density should track the couple's ratio.
03Refutation
Density improving without chemistry change would remove the ceiling.