This report presents a life-cycle assessment (LCA) study of lithium-ion (Li-ion) batteries used in electric and plug-in hybrid electric vehicles. The study also assesses a next-generation technology involving single-walled carbon nanotubes (SWCNTs) being developed to increase the energy capacity and marketability of these battery systems. The study was undertaken through the Li-ion Batteries and Nanotechnology Partnership (hereinafter referred to as ―partnership‖), formed in July 2009, with EPA‘s Design for the Environment Program in the Office of Chemical Safety and Pollution Prevention, and EPA‘s National Risk Management Research Laboratory in the Office of Research and Development . Li-ion battery manufacturers, research and trade organizations, battery recycling companies, and the Department of Energy‘s Argonne National Laboratory also participated in the partnership.