What is the Purpose of the Supercapacitor for Battery?

The supercapacitor resembles a regular capacitor with the exception that it offers very high capacitance in a small package. Energy storage is by means of static charge rather than of an electro-chemical process that is inherent to the battery. Applying a voltage differential on the positive and negative plates charges the supercapacitor.
This concept is similar to an electrical charge that builds up when walking on a carpet. The supercapacitor concept has been around for a number of years. Newer designs allow higher capacities in a smaller size. Supercapacitors are relatively expensive in terms of cost per watt. Some design engineers argue that the money would be better spent in providing a larger battery by adding extra cells. But the Supercapacitors and chemical battery are not necessarily in competition. Rather, they enhance one another.

Compaq Presario V2000 battery
Cell Type : Li-ion
Volts : 11.1V
Capacity :4400mAh,8800mAh
Battery Cells: 12 Cells(8800mAh), 6 Cells(4400mAh)
Color : Black
Dimension : 205.20 x 59.20 x 37.50 mm
Net Weight : 604.50 g(8800mAh), 310.00 g(4400mAh)