[andagainagain]

I just looked up the volume of aluminum vs lithium here: https://www.periodic-table.org/lithium-atomic-radius/

They have the same atomic radius of 121 pm. The length of bonds might change the calculation when you actually look at chemistry, but the increase in number of orbitals is not an issue.

Also, no battery uses 100% of their electrons for storage. Your calculation of using the number of electrons on the outer orbital vs the atomic mass is completely misguided. their claims don't say aluminum ion holds more energy per unit mass, but simply looking at the ions available per unit of molecular mass also doesn't tell you this.

[datameta]

You're correct - my assumption about atomic radius was off, which leads to an erroneous conclusion.