My iphone is death

Hello to everybody

This morning i tried to turn on my iPhone 8+ but it didin't,so i just thought it was a battery's fault and tried to charge his battery,i tried charging it for around 2-3 hours but it's still death.. If i try to turn on it it does nothing and if his battery should be exhaust a picture of a exhausted battery should appear,but it doesn't... Can someone help me? Yesterday it hadn't any problem,i used it as everyday! Just this morning it was death...