Advantages
1) Lithium-ion batteries can be formed into a wide variety of shapes and sizes so as to efficiently fill available space in the devices they power.
2) Lithium-ion batteries are lighter than other energy-equivalent secondary batteries—often much lighter. A key advantage of using lithium-ion chemistry is the high open circuit voltage that can be obtained in comparison to aqueous batteries (such as lead acid, nickel-metal hydride and nickel-cadmium).
3) Lithium-ion batteries do not suffer from the memory effect. They also have a self-discharge rate of approximately 5-10% per month, compared with over 30% per month in common nickel metal hydride batteries, approx. 1.25% per month for Low Self-Discharge NiMH batteries and 10% per month in nickel-cadmium batteries. According to one manufacturer, Li-ion cells (and, accordingly, "dumb" Li-ion batteries) do not have any self-discharge in the usual meaning of this word. What looks like a self-discharge in these batteries is a permanent loss of capacity (see below). On the other hand, "smart" Li-ion batteries do self-discharge, mainly due to the small constant drain of the built-in voltage monitoring circuit.