There is no shortage of lithium. It is a very common metal. But a handful of companies control the great majority of its production, so Elon would like to see more competition. And actually, there is not a heck of a lot of Lithium used in a Lithium ion battery. In South America, they just pump brine onto an open field, and wait for the water to evaporate --- its hard to compete with that cost structure with big equipment digging a hundred feet underground and then milling and processing the ore -- that's why you see few lithium mines up here.
Some of the other metals in a lithium ion battery are pretty expensive (such as cobalt, nickel, manganese , but there are many possible chemistries to use in a lithium ion battery, and there is constant development of better, cheaper chemistries. So think twice before buying stock in that cobalt mine --- right now the chemistry using cobalt is considered best for most applications, but you could wake up tomorrow morning and somebody has come up with a chemistry that uses no cobalt and works just as good for those applications.
