Because of its high reactivity and low mass, lithium is used as the charge carrier in the lightest and most energy-dense rechargeable batteries on the market. Ignore talk of "peak lithium." The element is abundant and environmentally benign.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.