Charging 24/7 and dangerous Expanding Batteries

So I use my old iPhone 6 essentially as a Clock Radio with a Clock app. One day the screen begins to pop off; and I discover its because of an expanding battery. This can be dangerous; and Apple will replace the entire phone tomorrow for me at no charge. However, this should not happen. Im simply using it as a clock radio by my bedside and yes I do keep the charger plugged in all the time. Should I unplug it daily in the morning? Is there a good solution for this? Should I get a real clock radio?????

Thanks