[lerouxb]

There is a LOT of lithium in the world and that's just near the surface - you can always dig down.

But at that scale you don't have to use lithium anyway. When it comes to grid or off-grid storage, you don't need the best energy density as cost per watt-hour is probably the most important factor and there are already other chemistries on the market that will work just fine with many more on the way. Sodium or Aluminium based batteries seem particularly promising.