This has the sound of a business plan that only makes sense from the standpoint of a state-run neo-fascist economy fed by endless amounts of cheap labor. Like China. Otherwise, giant batteries make no more sense than giant capacitors or giant windmills.
Batteries do wind up failing over time. Internal resistance builds up due to heat. They don’t last forever.
It also assumes that the renewable energy source produces more energy than the grid demands in order to put the excess power into the batteries.