...This assumes the batteries last 10 years. The problem is that they probably won't except for some very-specific corner cases.Oh.
The reason is how batteries work. They start to degrade chemically on the day they're made, and do so more-or-less linearly. There's nothing you can do about that -- this happens even under ideal storage conditions. In addition there's a "per-cycle" penalty too, because batteries operate through ion exchange across the electrolyte -- that is, the physical movement of ions between cathode and anode.....
So those "utility-grade" batteries used to store sunshine- and wind- produced electricity.....how much will utility customers PAY for these marvels of short-term usefulness?