Well, no, actually. Lithium is literally #3 in the list of elements. We are using it because it is lighter then the other elements we could use from it's group and because it is not completely unsafe.

There are other potential elements for storing energy, yes. Liquid aluminum is one that people are looking into for storing energy from solar for night-time use. But that is completely impractical for what Elon cares about: electric cars. Pound for pound, lithium is the best we got and that ain't soon changing.

The most nicest take I can make here is that Elon had to say something so his shares don't tank. There is no magical solution to this. Literally everyone wants better ways to store electricity and has wanted them for as long as we have been using it. If Elon had even an inkling if a sliver of an idea on how to 'revolutionize batteries', we would know about it not in an abstract statement but because investors would be showering him in money to develop it. He has nothing.