It's 31st in the crust, there's more than Lead.

Then it's all over the world in other areas in higher concentrations like in brines (the easiest way for us to get it) or clays, and there's over 200 billion tons of it in the ocean. Granted the ocean stuff would take some figuring out how to get, but it's a ridiculous amount.

Whenever we go looking for it, we keep finding vast reserves of it.

Such as this just this month: https://finance.yahoo.com/news/1-5-trillion-lithium-deposit-114805186.html?guccounter=1

Edit: for the sea water stuff, capturing it as a side product of desalination or a next step in desalination might be a starting way to begin extracting it without massively increasing costs as some of the costs will already be part of desalination, which could help bring desalination costs down via another revenue stream.