Of course, Li-ion batteries will never cover large-scale power demand. Not primarily because of lack of lithium, but because it’s a technology that scales far too poorly into the MWh/TWh scale, and has a far too short lifetime.
The battery tech we need for truly large scale storage is different from what we need for small, portable storage. Stuff like redox-flow batteries are looking promising.
There’s also hydrogen, with different storage methods being actively researched- from direct storage to using ammonia as a carrier.
The issue with using mechanical storage (like pumped hydropower) is threefold (off the top of my head):
It has ridiculously low energy density
Even after > 100 years of pumps and turbines, the power loss in a pump/release cycle is very high.
It’s heavily limited by geography
I’m not saying pumped hydropower isn’t part of the solution: I believe the solution is that we need many solutions. I just think it’s important to point out that battery tech isn’t some monolithic thing, and that there are issues with pumped hydropower (and mechanical storage in general).