Aluminum is abundant. If we need more, we refine more; it mainly takes electrical power, which is getting cheaper all the time.
Sure, I don't mean to imply it's not possible or anything even close to that, merely that it's something that will take a while rather than be ready this decade.
I'm kinda leaning towards expecting batteries (specifically batteries and not storage in general) to be the first way a continental power grid gets to 100% renewable, even though I prefer the aesthetic of a global grid. But I don't have any skin in the game, and wouldn't bet against e.g. a cheap high temperature superconductor grid or liquid hydrogen.
Batteries will always be the expensive choice of storage. There will be a certain amount of it anyway. But utilities, for bulk storage, will favor cheaper alternatives.
Perhaps it will be the expensive choice, but I expect batteries produced for cars to be moved to grid storage when any given vehicle's capacity drops below the level useful for transport, and the combined capacity of the reused batteries of a fully-electric-car-nation, even with those batteries in a worn state, will suffice for grid storage.
My guess is this transition will take 15-20 years to complete, but I have low certainty on that.
A worldwide grid is absolutely possible from a technical perspective even with boring non-superconducting aluminium and/or copper, it's just that the combined cross section needs to be in the order of 3m^2, which is 17 years of current global output of both metals combined and has a current cost of a few trillion USD: https://news.ycombinator.com/item?id=32198057
(That said, my old linked estimates are over-simplified, that's a single minimal ring, and only works if the 64% resistive losses for current existing HVDC cables over that distance match the possibly lower demand because people do less at night).