The professor in the CMU video, which you watched, said there is about 140 mAh/gm of cathode material. The formula is LiFePO4. Using the atomic weight of each atom, how much lithium does that tell you there is in a 100 Ah cell, and in a 30kWh pack with nominal 3.2V/cell?
China gets lithium mainly from Atacama Chile, which has the largest known reserves (estimated at around 7 million tonnes of lithium metal). Uyuni, Bolivia has the next largest reserves, then China/Tibet. These are all in the form of brine, the easiest to mine. Next largest reserves are in North Caroline in pegmatite, which is much more difficult to mine. Next largest are in the Congo, also pegmatite, next largest is in Kings Valley Nevada in clay, which is much easier to mine than pegmatite, but not as easy as brine. These sources together are estimated to have over 21 million tonnes of lithium metal. With the above calculation, how many 30kWh packs would that make?
There are other sources, for example Argentina is estimated to have around 2 million tonnes, Russia 1 million. I have no idea how thorough the exploration for Li has been, so there may be more. The Kings Valley area is estimated to have a little over 2 million tonnes of lithium metal, or 11 million tonnes of lithium carbonate equivalent (LCE), which is the form in which lithium is sold. Reference for reserve estimates: April/2009 presentation from Western Lithium Corporation (developer of the Kings Canyon mine).