Hybrid cars that can recharge their batteries by plugging into electrical outlets could enable nearly gas-free commutes and even provide extra storage on the electrical grid, but they're not yet commercially available. This year, however, Toyota Prius owners will be able to turn their cars into plug-ins by installing a new battery pack from A123 Systems, a company based in Watertown, MA. The pack stores five kilowatt-hours of electricity and uses a new nanostructured electrode material that makes high-­capacity lithium-ion batteries safe enough for automotive use.

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