Of all the metals, lithium is the lightest, has the highest electrochemical potential, and offers the most specific energy per weight. The anode of rechargeable batteries containing lithium metal could offer extremely high energy densities.

Between the anode and cathode, a micro-permeable separator allows the lithium ions to move through. Li-ion batteries can have a very high voltage as well as charge storage per unit mass and volume in part due to lithium's small size—it ranks third only to hydrogen and helium. Li-ion batteries are significantly more beneficial than other high-quality rechargeable battery technologies (nickel-cadmium or nickel-metal-hydride).