This is a decent nerd video that talks about lithium mining. I enjoyed it. Skip to 13 min for the answer . https://www.youtube.com/live/inq_ypJeiZk?si=o34J3qJVNoDJ2FBy
I think it is an interesting lecture if you are interested in a sort of geographical answer of where they might look for it, but at least after skipping around a bit and watching some stretches at double speed, she hasn’t gotten to the sort of economic answer of, like, do there exist sources that can turned into batteries easily (since we are mostly programmers who mostly care about whether or not the batteries will exist to power the devices we want to program).
> do there exist sources that can turned into batteries easily
Yes, but only a few. There aren't many high-concentration lithium deposits. (There are many more low-concentration)
Which is essentially the mining industry in a nutshell: concentration of raw mined feedstock -> economically efficient processing -> finished product (bought by consumers who don't care where it came from, and so has a single market price)
See: https://en.m.wikipedia.org/wiki/Lithium_carbonate#Production