https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...
Here's the USGS lithium report from 2010 that this Stanford web page got lithium reserve and resource numbers from: https://s3-us-west-2.amazonaws.com/prd-wret/assets/palladium...
Here's the corresponding USGS lithium report from this year: https://pubs.usgs.gov/periodicals/mcs2022/mcs2022-lithium.pd...
See the tables "World Mine Production and Reserves" in these reports and following paragraphs.
From the 2010 report to the current report, world lithium resources went up from 25.5 million tons to 89 million tons even as extraction rates rose from 18,000 tons per year to 100,000 tons per year. That alone brings us up to 37 billion Nissan Leafs.
How can resources go up even as we're using lithium faster? It's because reserves and resources are determined by a combination of economics and technology. The Earth's crust contains 20 ppm of lithium now and 12 years ago (or a million years ago, for that matter). The geology doesn't change but the effort put into identifying potential sources of lithium and means of extracting and purifying lithium does change. Geologically speaking, the Earth has a lot of lithium. For as long as the USGS has been keeping records -- only a few decades, admittedly -- world lithium reserves have been increasing faster than they have been depleted, because the industrial demand that causes reserve depletion also spurs additional research to identify potential lithium sources and extraction processes. This Economist article is about such new processes.
Theoretical quantity - That would be the 20ppm as you said. Based on knowledge and estimates.
Identified reserves - How much of this stuff do we actually know about and is in a suffciently enough pooled location. This would be less than the 20ppm - how much less is a different question.
Technically available - How much of the known resource could we actually extract? It is ok if we know about it but if it is 10KM below a lake, could we get to it?
The most important stage after those three - Economic availability. Can we actually afford it and have people pay for it?
The argument from absurdity I use on this one is that there is effectively near infinite clean energy in the form of hydrogen in the sun. No one owns it - now go get it! The technical and economic scale ruins the argument a fair bit.
I'm not even arguing against lithium here, it seems to be more output restricted than resource limited. The two elements in batteries I worry about is Cobalt and Nickle - they could become the weakness. That said it does look like some folks are working on some neat alternatives in that space.
Problem is that until recently lithium was not a hugely in demand element. As a result not a lot was invested in finding the stuff. Now that it is important large investments will be made and a lot more is likely to be found. It’s a light element and is very abundant in the solar system.
So this means that after not really trying very hard we have already found enough to give every human an EV. That is encouraging. If we try a bit harder and find say 50% more we are good for a really long time.
Oil is an example of something we have tried really really hard to find. We’ve found a ton more than we thought we would.