My Ipad Battery is about to explode

I have a seen a lot of videos lately talking about samsung phone batteries swelling up, so I decided to check my old collection of Samsung and Apple gadgets, it turns out my ipad battery is swollen or has been swelling and I didn't even know it. But is is this happening? why are samsung phones swelling up? why are ipads swelling up? why are phone batteries swelling up rapidly this days?