Samsung SDI takes sole control of unbuilt GM battery plant

Samsung SDI and GM signed their original joint venture agreement in 2023; in 2026, Samsung SDI took full ownership of the plant it produced

(Image courtesy of Samsung SDI)

Samsung SDI has taken full ownership of its New Carlisle, Indiana battery plant, buying out General Motors’ 49.99% stake in the SynergyCells joint venture the pair formed in April 2023. The move ends a $3.5 billion joint venture whose construction stalled months before the sale, and it redirects the site toward stationary energy storage rather than the EV cells it was built for. GM and Samsung SDI have simultaneously signed a separate agreement to co-develop prismatic EV cells, keeping their technical partnership alive even as the ownership structure changes.

Samsung SDI takes full control of the Indiana battery plant

Samsung SDI announced the acquisition on August 11, confirming it now holds all of SynergyCells, the venture it set up with GM in April 2023 to build a cell plant in New Carlisle. GM had owned 49.99% of the entity. The two companies first announced the plant in April 2023, then finalised commercial terms at a signing ceremony in August 2024, committing roughly $3.5 billion to a plant with 27 GWh of initial annual capacity, expandable to 36 GWh, across a 275-hectare site. The companies originally targeted 2026 for production, then pushed that date to 2027. Construction stalled as the demand outlook softened, and GM confirmed in May 2026 that work at the site would pause “to align production capacity with current demand.”

Energy storage takes priority over EV cells

Once construction resumes and finishes, Samsung SDI plans to use the plant first for energy storage system batteries, aiming at the fast-growing US ESS market, before any EV cell production begins. That pivot fits a broader retreat from dedicated EV cell capacity across the industry. GM already exited a separate cell joint venture in Lansing, Michigan with LG Energy Solution, announced in December 2024. The automaker recorded a $6 billion EV business write-down in January 2026, after a $1.6 billion write-down the previous October. Those write-downs came amid the expiry of the federal EV tax credit on September 30 2025, alongside a broader slowdown in EV demand. Ford and Stellantis have made comparable moves. The former dissolved its BlueOval SK joint venture with SK On in December 2025 and restructured its loss-making Model e EV division in April 2026. Stellantis has held talks about exiting its own Indiana battery joint venture with Samsung SDI, StarPlus Energy, though no final decision has been reported.

A new prismatic cell agreement survives the split

Despite dissolving the manufacturing joint venture, Samsung SDI and GM signed a separate agreement to co-develop next generation prismatic battery cells for potential future EV use. The cells are designed for high energy density and fast charging. The primary release stops short of confirming a production date for the jointly developed cells, framing New Carlisle’s eventual EV role as a future possibility rather than a firm commitment. That distinction matters for a specialist audience. In practice, the arrangement lets the two companies keep cell chemistry and powertrain integration work alive while removing fixed manufacturing risk from GM’s balance sheet, without committing either company to a production date.

What the Samsung SDI Indiana battery plant means for the US EV supply chain

For procurement and supply chain planners, the shift toward ESS cells ahead of EV cells removes a near-term source of domestic EV cell capacity that GM had planned into its electrification programme. Samsung SDI becomes the plant’s sole developer, gaining a wholly owned North American production base. In principle it can now supply that capacity to other customers rather than dedicating it to one partner, though its own release names only ESS and the GM prismatic cell programme as current plans. The facility’s construction remains paused, so timelines for both ESS output and any future prismatic EV cells now depend on when Samsung SDI restarts the site, without GM sharing the capital commitment.

Samsung SDI has not set a date for ESS production to begin at New Carlisle, and the prismatic EV cell agreement carries no confirmed production timeline. The next signal worth watching is whether Samsung SDI files updated capacity or investment plans with regulators now that it holds the site outright, and whether GM identifies a replacement source for the cell architecture New Carlisle originally existed to supply.