There are lots of articles on it but here is one from 6S/7 regarding 300-400 cycles [1]. You can look for Apple battery swelling and nearly every gen since 5 ha

There are lots of articles on it but here is one from 6S/7 regarding 300-400 cycles [1]. You can look for Apple battery swelling and nearly every gen since 5 has some issues with it, it seems related to overcharging. Even iPhone 8 is having issues with swelling. [2] [1] http://bgr.com/2016/11/30/iphone-7-vs-iphone-6s-battery-drain/ http://bgr.com/2016/11/30/iphone-7-vs-iphone-6s-battery-drai... [2] https://www.macrumors.com/2017/10/01/apple-looking-into-iphone-8-battery-failures/ https://www.macrumors.com/2017/10/01/apple-looking-into-ipho...