Current production of lithium is low because demand for lithium is low. Lithium @ 17 ppm is actually more common than Lead @ 10ppm in the earths crust. https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...
PS: 37,000 tonns of Lithium are produced in 2012 vs 5,200,000 of lead.
I know next to nothing about geology, but a little browsing suggests that it is easy to find galena and that it is a much more productive ore than the typical lithium ores.
My point was, it's not really a question of how much can be produced, but at what price you can produce it. Right now the market is paying ~6,000$ per tonne which has been fairly steady if slowly growing over time. With battery's making up about ~1/3 of the market. At say ~12,000$ per tonne production could double in well under 5 years.
So, as long as Tesla is happy to pay 12k/tonne they can get more or less as much lithium as they could ever want. More importantly the price need not spike anywhere near that much as long as demand is predictable. In 5 years the price for most commodities is often more or less a function of the delta between expected demand and actual demand.
If you can get into production at say 4k/ tonne it's no question the market is growing so at the price is unlikely to crash any time soon. At ~6k/tonne cost cutting is going to be really important fairly quickly, but it's a reasonable investment. At 7+k/tonne it's a huge risk which is only worth it IMO if you can line up a long term contract at a fixed and profitable price or if you can tightly control costs and only ramp up in case demand spikes (ex: your mining something else, but you could also exact lithium from your tailing).
However, even when adjusting for heaver Lead atoms we produce far more Lead.