the case for grid-scale batteries is getting stronger every month:

the more people driving EVs the more used EV batteries will become available… EVs require a pretty good energy density, but grid storage can buy up a bunch of dirt cheap EV batteries with 60% capacity and call it a day, and then onsell them for recycling in 10 years for exactly the same price (because the raw materials are the same: recyclers don’t care if the battery has 100% or 60% or 50% max capacity)

other battery tech is also getting much more interesting, like sodium batteries. they don’t have the energy density of lithium, but they’re more durable and have less fire risk. they’re pretty ideal for grid-scale storage, and when commodities of scale kick in with them they’re likely to become pretty common in grid storage and prices and usefulness just gets better from there

also, afaik gravity batteries aren’t really being used… the most common thing these days looks like it’s going to be flywheels, but using them more like capacitors: smoothing out load spikes and maintaining grid frequency (which with PV can go downhill fast)