They have many pros and few cons. the pros include their extremely long life. they can hold a charge for long periods of time, they only loose %5 of charge a month compared to a regular battery that looses %20 a month. One of the cons is the price. Lithium-ion batteries are really expensive because of the computer they have on them to manage their functions. They also are heat sensitive and will loose their life in heat. They begin to loose their life as soon as they leave the factory and their is a 2 or 3 in a million chance that they will burst in to flames for no reason.
Lithium has many other uses. One is in greases because it is thicker. It is used in pills for mood disorders. Their are also pills for bipolar disorders.