[Incipient]

Sorry I should have said LIKE a capacitor in terms of function. You are correct they are not a capacitor in terms of design and function. I'd have expected people here be able to understand that.

Fundamentally, at a grid level, lithium batteries can't provide what the average person considers "storage", that is running the grid from said storage. When people hear lithium battery, they think of a phone or laptop - the battery is the sole source of power for 6-12 hours.

On a grid however, lithium batteries provide very short duration stabilisation from "noisy" supply, absorb spikes in generation and boost troughs.

You cannot cost effectivly power the grid from lithium batteries on a still night. Pumped hydro etc are needed to cover prolonged periods of low supply (and absorb prolonged periods of oversupply).