Elon Musk is pleading for more investment in lithium, the silvery-white metal that's crucial to making electric-car batteries. He recently complained about the metal's "insane" costs and said anyone who enters the refining business basically gets a "license to print money." The billionaire has a point. As the auto industry shifts away from dirty fossil fuels and toward cleaner battery power, lithium is in the spotlight. Demand for the metal has skyrocketed in recent years, as has its price. Questions still remain about whether the world will manage to mine, refine, and ship enough lithium to support the green revolution...