Elon Musk is calling for more people to get into the business of refining lithium, one of the key materials in electric-vehicle batteries.

The Tesla CEO on Wednesday urged entrepreneurs to start lithium-refining ventures, promising that entering the business is "a license to print money."

"It is basically like minting money right now. There's, like, software margins in lithium processing right now," he said. "So I would really like to encourage, once again, entrepreneurs to enter the lithium refining business. You can't lose."

Lithium is abundant, Musk noted. The challenging part, he said, is processing it to the point that it can be used in battery cells. "You have to refine the lithium into battery-grade lithium carbonate and lithium hydroxide, which has to be extremely high purity," Musk said.

The global transition to electric vehicles has driven frenzied demand for lithium, sending its price through the roof this year. Lithium prices have more than doubled since January and risen nearly 400% in the last year, according to Benchmark Mineral Intelligence.