Thin battery attached to the bottom of some laptop computers to increase the overall battery life, sometimes up to 10-hours. The battery slice is the same horizontal and vertical diameter of the bottom of the laptop, once attached it slightly increases the overall height and weight of the laptop. To help prevent the laptop from overheating there is a small gap between the laptop and the battery slice to keep proper air flow. Dell, Hewlett Packard, and Toshiba are just a few of the laptop manufacturers who have battery slices available for some of their models.
Also see: Battery definitions