Any chemistry still being considered can operate at your "grid scale". If you need more storage, you buy more battery. Pumped hydro dominates mainly because the

Any chemistry still being considered can operate at your "grid scale". If you need more storage, you buy more battery. Pumped hydro dominates mainly because the dams and turbines were already there. So "can it operate at grid scale?" is a bullshit question. All storage alternatives can operate at grid scale by adding more units. What matters is cost, and costs are changing. Even Energy Vault's fraudulent hi-rise condo for concrete blocks could scale up, in principle. It would just be stupidly expensive, and its cost cannot come down noticeably, so they won't sell any condos. People holding NRGV shares will lose badly, and people with call options on it, much worse. You might make a lot of money betting it will collapse, but they could in the meantime swap equity for something that works, and then not ruin that. Unlikely, though: who would be smart enough to have something that works, but dumb enough to swap? Some technologies and battery chemistries will win big, reliably. We just don't know which ones.