it is thought that the worlds oceans hold 2.6 x10^11 tonnes of lithium. that works out at 325 tonnes of lithium for every person on the planet. Even if every vehicle on the planet went electric we would still have probably 95% of it left.
Ah, you say, but we have not found a way to extract it.
That is the news: despite being 0.2 parts per million in the ocean, a team at King Abdullah university of Science and Technology in Saudi Arabia have found a way of extracting lithium at far lower prices. While the ocean contains 5000 times more lithium than on land, it is still a very small fraction. They found by using a very carefully designed electrochemical cell containing a ceramic membrane made from lithium lanthanum titanium oxide. When this and several other processes have occurred, the lithium reaches concentrations of more than 9000 parts per million. By then adjusting the ph of this solution, solid lithium phosphates containing only trace other elements are formed. these are pure enough for battery manufacturers to take over.
Incredibly, this method would only take $5 of electricity to create 1 kg of lithium (and the hydrogen and chlorine that are by-products are already worth this amount. One kg of lithium is currently worth about $35, making this a very profitable venture.