Unlike alkaline batteries, lithium batteries have much longer lives. For this reason, they are ideal for power-hungry devices like cameras and MP3 players. Since lithium batteries use the same voltage as alkaline batteries, they can be used interchangeable in clocks and toys so that these devices can run much longer without needing new batteries. On the downside, they are more expensive. But since you will be changing batteries less often, in the end you will save money. Also, you won't be throwing out so many batteries which contain harmful chemicals. Buying a large number of cheap lithium batteries with a free shipping offer will help keep costs down.