ifixit battery has 5-minute life and cracked rear case

I replaced my original battery with the Samsung battery from Ifixit.com I reassembled the phone with new adhesive. Upon starting the phone said 7% battery, then it died before I could plug it in. I plugged it in, and the screen said 0%. I turned it on with the charger plugged in to let it charge fully (uninterrupted).

The next day the battery died after about 30 minutes off of the charger even though it read 95%. It started to boot loop since it was not enough power to boot the phone. I plugged it in and turned it on and the phone said 3%. So, I let it charge fully - uninterrupted again.

At this point, the back case showed signs of serious swelling of the battery and upon removing my soft gel cover, the case cracked in the center and then sprung off of the lower edge.

Why is an original Samsung battery having these problems, and how do I fix this? Will Ifixit warranty the battery? Will they provide me with a replacement back cover????