Dumb question: Who is the supplier of the batteries for the other automotive companies?
You can typically find that pretty easily by just checking the Wikipedia page for a vehicle. LG Chem does a lot of the cells for GM, Panasonic works with Tesla.
One thing that many people misunderstand, though, is the difference between the battery cells and the battery pack. How the cells are packaged (density, how thermals are managed, the software that manages charging and discharging, etc) is one way to add value. As Samsung has discovered with the Note 7, what you do with the cells matters a lot.