Samsung SDI takes full control of its Indiana battery plant as GM walks away from EVs
Samsung SDI now owns its first North American factory outright after buying General Motors' 49.99% stake in their joint venture, SynergyCells, on August 11. The Indiana plant — originally a $3.5 billion investment designed to pump out battery cells for GM electric vehicles — will now focus on energy storage systems (ESS) instead. The pivot is a concrete sign of how badly US EV demand has missed projections.
The breakup
The SynergyCells factory in New Carlisle, Indiana, was supposed to start mass production in 2027, eventually reaching up to 36 GWh of prismatic cell output and employing more than 1,600 people. Prismatic cells use a rigid rectangular casing that packs energy more efficiently than cylindrical cells — the format favored by most Chinese automakers and increasingly by Western ones.
GM's exit came down to one thing: the US EV market is growing far slower than either company anticipated when they signed the original deal. The elimination of the federal EV tax credit, signed into law in July 2025 and effective from September 30, gutted the demand assumptions underpinning the entire venture. Rather than stay locked into a capital-heavy joint ownership during that uncertainty, GM chose to step back and become a buyer rather than a co-owner.
The new plan
Samsung SDI isn't walking away from GM entirely. The two companies signed a new joint development agreement for next-generation prismatic batteries — keeping the technology partnership alive even as the factory ownership changed hands. GM will effectively be a future customer rather than a partner with skin in the game.
In the near term, the Indiana plant will target the booming US energy storage market. Samsung SDI locked in a $1.35 billion, three-year ESS supply deal back in December 2025, per Charged EVs, and US demand for grid-scale storage is projected to double to 142 GWh by 2030. That's the market Samsung SDI is positioning itself to serve — as a non-Chinese prismatic cell supplier at scale, at a time when supply chain diversification is a political as much as a commercial priority.
The bigger picture
This restructuring isn't an isolated case. BloombergNEF projects battery demand through 2035 to come in roughly 8% lower than previously forecast, with the US slowdown accounting for 2.8 TWh of that gap. Several North American battery joint ventures are dissolving or pivoting under the same pressure. The SynergyCells story is less about Samsung SDI winning and more about what happens when EV ambitions collide with a market that isn't ready to move as fast.
