Quite an intriguing website.
Especially the graph of element abundance in the Earths upper crust normalized to Silicon (which is pretty abundant)
Sodium is (literally) as cheap as table salt.
Lithium got its jump on other choices because (at some point) a chemist did an energy density calculation. Li is lightest Anode element QED highest density.
But IRL you can't use pure Lithium/Sodium/Calcium and once you start needing high molecular weight polymers in there achievable density starts dropping (but Lithium prices stay the same or rise).
So Lithium is the Gold standard in battery energy density even in "Lithium"
Which suggests Sodium might be quite worthwhile.