[layoric]

"time-smoothed electric grids". Exactly, this is actually where Lithium batteries make the most sense, especially with solar. It isn't to provide 100% backup output at a grid/utility scale but to make output more consistent when it comes to voltage variance and output. Time shifting power output even by minutes via storage combined with solar forecasting (disclaimer: I work for a solar forecasting company), from what I can tell, can remove a large chunk of uncertainty. The better the forecasting, the smaller the battery can be whilst maintaining low levels of uncertainty.

Grid scale "backup" via Lithium batteries IMO, doesn't make any sense. Generating hydrogen from excess power for grid scale generation actually does make sense. As power generation gets cheaper still and the "now" value of it also becomes less, I think it will make financial sense to locally "bank" energy in the form of hydrogen for versatile use during peak times where grids are overloaded with renewable energy (and wholesale price is 0 or negative which is common quite often in some networks).