I must say this sounds like a very energy-expensive method of storing energy and I think I agree with the poster who prefers to bike to the nearest e-train :-)  There's a presupposition in a lot of these "gee wow, here comes the cavalry" articles on energy that the Almighty Automobile is the immutable term and we have to go through whatever shenanigans are necessary to maintain it.  The problem may get much simpler if you factor the Almighty Auto (the Sacred Cow of the industrialised nations) out of the picture and think about smaller/lighter mobility devices plus excellent  rail and water networks.

Also of course, as an aluminium customer (for boat parts) I rather dislike the idea of the metal suddenly becoming a trendy snake-oil investment oppo -- just what I need is a Tulip Bubble in aluminium when I'm shopping (somewhat ineptly) for industrial pipe...

The difference between theory and practise in practise ...