The image showed up at 9to5Mac late Thursday night. The elongated nature of the new battery agrees with the rumors about an iPhone 5 with a 4-inch screen that is stretched lengthwise to a new 16:9 aspect ratio. The capacity of the new battery is shown to inch up to 1440mAh, from 1430mAh in the iPhone 4S (the iPhone 4 had a 1420mAh battery, so Apple must not like leaps of greater than 10mAh).
It's such a slight increase, it would seem insufficient to offset all the new added features in the iPhone 5, or even the most-hoped for one: LTE. LTE support still sucks battery as though it were going out of style. If that's the case, this should keep makers of iPhone battery extenders in business, since the iPhone does not have a user-replaceable battery.
It's possible, though, that this is not the actual battery for the iPhone 5, but according to 9to5Mac, this came from a reliable parts source.
In addition to the slightly larger capacity, the purported iPhone 5 battery has a new voltage, up slightly to 3.8 volts from 3.7 on both the iPhone 4 and 4S. It also has increased WHr measurement, 5.45 WHr, but that is a proportional increase due to the larger capacity (the increase is from 5.25 on the iPhone 4 and 5.3 on the iPhone 4S).
The sheer number of leaks that have been occurring recently are consistent with an iPhone release that is very near. The latest rumor has said the iPhone 5 will be announced on Sept. 12, with a release to retail on Sept. 21.