DETROIT — General Motors is forming a joint venture with Posco Chemical of South Korea to build a North American battery materials plant as it brings more steps in the electric vehicle supply chain under its umbrella.

The Detroit automaker said today that details of the venture are being worked out, including investment amounts and the plant location. GM said the factory will supply materials to make cathodes, the energy center of a battery that amounts to 40% of the cost.

The plant will employ hundreds of people and will start making materials in 2024, said Doug Parks, GM’s global product development and supply chain head.

The plant will supply four North American battery cell factories that GM plans to build. Two of those locations have been announced, Spring Hill, Tenn., and Lordstown, Ohio.

“Scaling battery production is central to our strategy to drive mass adoption of EVs,” Parks told reporters Wednesday. “I think this helps to solidify the supply chain and add security to it.”

Automakers are racing to line up suppliers for scarce battery materials and components in anticipation of a widespread shift from internal combustion vehicles to those powered by electricity.

GM plans to build 30 electric vehicles globally by 2025 and says it will spend $35 billion between 2020 and 2025 on electric and autonomous vehicles.

The new plant will make materials for GM’s new Ultium battery chemistry, using nickel, cobalt, manganese and aluminum, Parks said. A cathode is the negative terminal where current leaves a battery,