Independent of the thinner design than the previous iPhone 6, it is rumored that the new iPhone 7 shall be having a bigger internal battery than its previous model.
Currently, the phones have a 1715 mAh internal battery while the 6S Plus has a 2750 mAh battery along with 5.5 inch Retina display. Weibo says that the iPhone 7 shall go further by having a 1735 mAh battery wile the iPhone 7 Plus shall have a 2810 mAh battery.
It might not seem too much of an improvement but think of all the extra time that it ‘could’ get you despite the slimmer design. This is definitely a bigger opportunity for Apple to make the best use of it through manageable OS and other power options that drain battery life unnecessarily or else no better apps shall be ever fruitful.
Expected to arrive this fall, the phone isn’t expecting much changes in its aesthetics to be in the 6s range while a slightly thinner reorganized layout and antenna redesign has been seen.
Chinese sites might not be the best reliable sources but an increased battery is not something too astonishing not to believe.