According to the source on the original post, the images of the these alleged iPhone 7 batteries come from the same source who leaked the dual camera module in the iPhone 7 Plus "Pro."
It's hard to tell whether or not bigger batteries in the iPhone 7 would lead to better battery life. Considering the relatively small increase in size, battery life may not be significantly affected.
Regardless, if this leak turns out to be true, the iPhone 7 would still have a smaller battery than the iPhone 6. Apple actually introduced slightly smaller batteries in last year's iPhone 6s generation - that change can be attributed to those phones' A9 chip, which was more power efficient than the A8 chip in the iPhone 6 generation. So despite these changes to the battery size, there wasn't a big difference in battery life between the iPhone 6 and iPhone 6s.
The iPhone operating system, iOS, also plays an important role in power efficiency as it can manage how much power is allocated to the iPhone's components when performing certain tasks.
The iPhone 7 is said to run on a new Apple chip, which will probably be called the A10. There's no information on whether or not it'll be more or less power-efficient than the A9 chip, but we'd guess its efficiency would be either equal or greater than last year's chip.
There's no good way to validate or debunk the leaked images of this alleged iPhone 7 battery, but overall we're not expecting any significant leap or decrease in battery life. iPhones can generally last over a day with mixed usage, and heavy users can feel free to top up their battery charge throughout the day without worrying about wearing down the battery.