Nickel-iron and lead-acid batteries have a lot of historical use for grid-backup applications, and lead-acid ones are still cheaper than lithium, but I don't think the resources are there to scale to an all-solar civilization. Nickel-iron batteries might be cheaper (the resources are a lot more abundant) but nobody sells them anymore I think?
There are whole classes of all kinds of energy sources that haven't been industrialized yet, including, to a great extent, nuclear energy. EGS comes to mind. The critical thing about PV is that it's crossed the chasm to mass production and the ensuing price drops. So I think it's crucial that current lithium production won't scale to the needs of an all-solar grid — but that oceanic extraction could.
If you liked this thread, you might also enjoy https://news.ycombinator.com/item?id=26219000
https://pubs.acs.org/doi/10.1021/acsenergylett.0c02181
Then there are entire classes of flow batteries that have not been industrialized yet, that have a lot of potential too.
We're using lithium batteries on the grid because we need the high specific energy for EVs, and now that we have an industry it's easy to dual purpose them. But we could also start using those same factories to rolling entire other chemistries that use the same form factor.