SK On Seosan Plant EV Battery Expansion Faces Investment Delay

SK On Seosan Plant EV battery expansion plans have been revised as the company reassesses the pace of capacity addition in response to shifting electric vehicle market demand. Multiple South Korean media reports indicate that SK On Co. Ltd. the battery manufacturing arm of SK Innovation Co. Ltd. has decided to defer capital expenditure for its third battery facility in Seosan.
SK On adjusts Seosan expansion timeline amid EV demand uncertainty
The No.3 Seosan Plant, currently under construction in Seosan-si, Chungcheongnam-do, was earlier fast-tracked to support mass production from 2026. Following the revised investment schedule, the start of full-scale operations is now expected to shift to around 2027. The company clarified that the final commissioning timeline will depend on how global electric vehicle demand evolves over the coming period.
Existing SK On Seosan battery manufacturing footprint
SK On already runs two operational battery plants in Seosan that support its growing EV customer base:

• No.1 plant with an annual production capacity of 1 GWh

• No.2 plant with an annual production capacity of 6 GWh

Together, these facilities form the backbone of SK On’s domestic battery manufacturing operations.
Planned capacity of the No.3 Seosan Plant
Once completed and fully operational, the third Seosan facility is expected to significantly scale up output:

• Planned annual production capacity of 14 GWh

• Designed to support next-generation EV battery supply

The delayed investment highlights how battery manufacturers are increasingly aligning capacity expansion with real-time EV market signals rather than aggressive pre-emptive scaling.