Samsung SDI Buys Out GM’s Stake in Battery JV

Illustration of a battery plant under construction in Indiana, USA

Written by

As of August 12, 2026, Samsung SDI has bought out General Motors' stake in their EV battery joint venture, giving the Korean battery maker its first wholly owned plant in North America. Separately, the two companies signed a new R&D pact to co-develop next-generation prismatic battery cells.

27GWhAnnual capacity of the New Carlisle, Indiana plant

49.99%GM's stake acquired by Samsung SDI

$3.5BTotal investment when the JV was founded in 2024

Key points

Samsung SDI acquired GM's 49.99% stake in their joint venture, Ultium… wait — the venture is named SynergyCells, giving Samsung SDI full ownership.
The plant sits in New Carlisle, Indiana, and is being built out to an annual capacity of 27GWh.
The two firms also signed a new agreement to co-develop next-gen prismatic batteries with higher energy density and faster charging.
Samsung SDI plans to add an energy storage system (ESS) production line at the same site.

Samsung SDI on Aug. 11 laid out two separate moves in its relationship with GM: a fresh R&D agreement on next-gen EV batteries, and a restructuring of the ownership behind a jointly built battery plant.

Under the new research pact, engineers from both companies will keep refining prismatic cell technology aimed at higher energy density and faster charging. Batteries built on that tech are expected to show up in GM's future EV lineup over time.

At the same time, Samsung SDI bought out GM's full 49.99% stake in SynergyCells, the joint venture the two companies formed in 2024, taking sole control of the business. The venture is building a battery plant in New Carlisle, Indiana, backed by $3.5 billion in total investment, with annual output eventually expected to hit 27GWh once complete.

With full ownership secured, Samsung SDI now has its first solo-run battery plant in North America. The company said the site will produce more than just prismatic EV cells — it also plans to build out a dedicated line for energy storage system (ESS) batteries, aiming to tap into the fast-growing US ESS market.

Samsung SDI has spent the past year locking down large ESS battery supply deals with US energy firms, steadily expanding its American footprint. Landing sole control of the Indiana plant makes clear the company is leaning harder on ESS as a growth engine while EV battery demand cools.

In Korea right nowBack home, Korea's battery industry — which has been squeezed by slowing EV demand — is watching this as a sign of how local players might pivot toward the US market. Keeping the automaker partnership intact while taking sole ownership of the plant could become a template other Korean battery makers follow for their own North American investments.

FAQ

What is SynergyCells?

It's the EV battery joint venture Samsung SDI and GM founded together in 2024 in New Carlisle, Indiana, with $3.5 billion in combined investment to build a 27GWh plant.

Does Samsung SDI's buyout end its partnership with GM?

No. Separate from the ownership change, the two companies signed a new agreement to keep co-developing next-generation prismatic batteries together.

What will the plant produce?

Prismatic batteries for GM's EVs, plus a dedicated line for energy storage system (ESS) batteries to serve growing US demand.