Nissan has opened the largest lithium-ion battery plant in the US at its Smyrna, Tenn., facility, to go under the hood during ramp-up of production of its 2013 Nissan Leafs early next year. The milestone also marks the two year anniversary of the Nissan Leaf in the US market, where 18,000 units have been sold and 46,000 worldwide. So far, it’s the largest selling battery electric vehicle in history.