Panasonic (PCRFY) and Tesla Motors (TSLA) announced that the two companies have reached an agreement in which Panasonic will expand its supply of automotive-grade lithium-ion battery cells to Tesla. With this agreement, the two companies update and expand their 2011 arrangement to now supply nearly 2B cells over the course of four years. The lithium-ion battery cells purchased from Panasonic will be used to power the award winning Model S as well as Model X, a performance utility vehicle that is scheduled to go into production by the end of 2014. This agreement builds upon a multi-year collaboration between Panasonic and Tesla to develop next-generation automotive-grade battery cells and accelerate the market expansion of electric vehicles. Panasonic's cells combined with Tesla's proven EV battery expertise have already enabled more than 130M customer miles driven in Tesla Roadsters and Model S.