To make the rechargeable batteries for hybrids like the Prius lineup, Highlander Hybrid and Camry Hybrid,Toyota buys materials from Sumitomo Metal Mining. That supplier has just bought 2,124,500 shares in their customer.
This gives SMM an ownership of 0.062% of Toyota. Neither company has declared the cost of the transaction but say it is part of strengthening the partnership between the two firms. Since 2010 the two companies have worked along with Primearth EV Energy on their nickel metal hydride
(NiMH) batteries recycling program. This program is the first of its kind and reuses the nickel from these batteries as material for fresh batteries. Toyota buys cathode materials for their hybrid batteries from SMM.
See the Press Release for more info