The iPad Air 2 is probably most impressive for its design. The original was super slim, and somehow Apple managed to make the new iteration even thinner. But as iFixit's teardown of the new tablet reveals, that hot design comes with a smaller battery.
Maybe it's not totally surprising that the battery got smaller. You have less room to work with. The new battery is 27.62 Wh whereas the previous battery was 32.9 Wh. Still, Apple claims that the iPad will have the same 10 hour battery life as its predecessor. And that's believable, that new A8X processor surely brings performance and efficiency improvements compared to the A7. [iFixit]