Higher Capacity Battery

I noticed a “new” higher capacity e200 battery listed on eBay.

It is 3.7V, 1300mAh, 4.81Wh - almost 2 times the capacity of “standard” batteries (650 & 750mAh).

Is it possible to double the mAh’s without increasing the physical size?

Sansa e200 battery 1300mAh

Probably not double, but the capacity has been increasing yearly, so if you compare a 2006 battery to a 2010 battery, it’ll probably hold a lot less per volume then the newer models.