I am a computer repairer based in Townsville, Queensland Australia.
One day, my wife passed me her iPhone 6, saying "I think there's something wrong with my phone". The front screen panel had 'domed' upwards in the middle from the rest of the phone by about 3mm, and there was resistance when I tried to push it back into the casing. Straight away I suspected that there may be a problem with the Lithium Ion battery.
Opening up the phone revealed that the battery had indeed swelled, pushing the display Assembly upwards.
I jumped online and ordered an iFixit iPhone 6 Replacement Battery Kit from Macfixit in Melbourne Australia, which came with everything I would need to open up the phone, including the pesky Pentalobe screws at the base of the unit.
Following the iFixit repair procedure from the iFixit website, I had the new battery installed and the phone back together and working within 20 minutes.
I repair iPhones and iPads as part of my everyday business, so there hasn't nessessarily been any enlightenment from this repair, as that had happened a few years ago when I first discovered the iFixit website!
But it did highlight the constant monitoring we face with Lithium Ion Batteries, and what may cause problems such as overcharging them.
I honestly hadn't seen anything like this with an Apple product before. Just goes to show that the battery issues are more wide spread than I had first thought.