I don't see a threat in other metals to replace Lithium (Li); we have to remember in the periodic table we have H, He and then Li.
Having this metal in the third place is a bliss:
- high reactivity
- low weight
- it is solid at room temperature.
Comparing with Sodium (Na) , for both (Li and Na) valence (ion charge) equals 1 but Na is more than three times heavier and a bit less reactive; these would conduct to much lower energy density (theoretically starting 3 times lower for Na) and requiring special conditions (usually higher) temperature for a similar power performance.
Magnesium would be even worst; I don't think it would be considered as a candidate in this race.
Regarding the price, yes, Na is abundant, present in high concentration deposits (salt - NaCl) and easy to extract. This is the main benefit for Na - cheap. So it might be considered for bulky energy storage but it would be out of discussion for EV or other transportation solutions.
So, Lithium is still the king.
