Lithium Iron Phosphate (LiFePo, or super capacitors) would skew the figures, and we've advanced upon those already.
I think it is in reference to the most common lithium-ion battery.
https://en.m.wikipedia.org/wiki/Energy_density_Extended_Reference_Table
Lithium Iron Phosphate (LiFePo, or super capacitors) would skew the figures, and we've advanced upon those already.
Not by much, could be up to ~0.576 MJ/kg (160 Wh/kg):
https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery