SEOUL, July 17 (Reuters) - South Korea's SK Innovation , parent of the country's largest oil refiner and battery maker SK On, plans to merge with energy affiliate SK E&S as the nation's No. 2 conglomerate undertakes a major overhaul to boost profitability, the Yonhap news agency reported on Wednesday.

The companies did not have an immediate comment. (Reporting by Joyce Lee, Editing by Louise Heavens)