Compared to the older Nickel-Cadmium and Nickel Metal Hydride rechargeable batteries, Lithium-Ion batteries are preferable as they have a greater specific energy density (energy stored per unit volume), have a much lower self-discharge rate, plus they lack the characteristics that required the older types of battery to go through complete charge cycles in order to avoid "memory effect" (where shallow discharges would prevent the cells from being unable to discharge properly in future).