Sodium-Air batteries can theoretically achieve an energy density...

Sodium-Air batteries can theoretically achieve an energy density of 1,600 Wh/kg.

Lithium Air (3460Wh/kg)

Unless some miracle happens and they re-write the Periodic Table. Lithium will ALWAYS have a higher energy density than Sodium.(By 2fold+)
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In the past, Sodium has been used as a battery. This is nothing new. They were combined with sulphur to form the NaS battery.

NaS batteries did have some Difficulties.


Safety concerns.
•Corrosion of the insulators was found to be a problem in the harsh chemical environment as they gradually became conductive and the self-discharge rate increased. Dendritic-sodium growth can also be a problem.


•Pure sodium presents a hazard because it spontaneously burns in contact with air and moisture, thus the system must be protected from water and oxidizing atmospheres.

•In 2011, NGK-manufactured NaS batteries for storing electricity installed at the Tsukuba, Japan. -The plant caught fire. Following the incident, NGK temporarily suspended production of NaS batteries.

These are just some quick examples, but there are countless articles written on the topic of using Sodium in batteries.