rumors

Afaik, there are many experiments and ventures on energy storage, like natrium, Solid State etc. But at the moment they aren't vialable for commercial, technical or production reasons . Lithium as an element has unique storage & cycle properties, as I understand it. You need more energy and space for natrium battery in cars, which won't make them usable for now.

Then again, tomorrow may come a breakthrough, but this is what we've been hearing for many years. So it seems they will stick with lithium.