Energy storage technologies, particularly lithium batteries, have been identified by the US Department of Energy (DOE) as critical enabling technologies for the development of advanced, fuel-efficient vehicles, especially for plug-in hybrid electric vehicles (PHEVs). Although significant progress has been made during the last 20 years in various battery systems, none of them satisfy all of DOE’s targets for PHEV applications. Improvements are needed with respect to energy density, power density, cycle life, safety, and cost, as described in DOE’s 2007 Plug-In Hybrid Electric Vehicle R&D Plan . Recent DOE , reports indicate that R&D on high-energy batteries for PHEVs and EVs should focus on: (1) High-capacity positive electrode materials; (2) Electrolytes stable at 5V; and (3) Alloy-based, high capacity anodes.