Tesla (TSLA) CEO Elon Musk this past week reminded investors of a growing challenge in the US when it comes to the electric vehicle industry — securing refined lithium for EV batteries.

"The choke point is much more on refining capacity than it is on mining. Lithium is actually is very common throughout the world, including in the US," Musk said on Tesla's earnings call. "It's much more a question of where is the refining capacity and can the refining capacity keep up."

Musk highlighted Tesla's plan for a lithium refinery near Corpus Christi, Texas which breaks ground in May.

Musk also took the opportunity, as he's done in the past, to call on other entrepreneurs to refine more of the mineral used in batteries to power electric vehicles.

"Like, instead of making a picture sharing app, please refine lithium. Mining and refining, heavy industry, come on," said Musk.

'Where is all the material going to come from?'

Currently, much of the world's lithium refining happens in China and is directed at the country's own growing EV market.

But the Biden Administration's push towards greener technologies is about to create massive demand for lithium here in the US.

"We currently in the US produce around 20,000 tons of lithium hydroxide refined in the US. We think we need over 700,000 by the second half of this decade. So, 35 times more," Keith Phillips, CEO of Piedmont Lithium, whose customers include Tesla and LG Chem, told Yahoo Finance in an interview.

"All of this is a little more future facing — and the question I think is — where is all the material going to come from?"

Piedmont Lithium is the process of building an integrated mine and refinery in North Carolina, as well as a refining facility in Tennessee. The company is also involved with projects in Quebec and Ghana.

"We need more of both," said Phillips. "We need more refinery capacity, obviously. Because you can't make a battery with [rocks]. You need refined chemicals. And the desperate need — I think — is for more raw material out of the ground. And the more of that we can produce in the US the better."