It is hard to see but the whole top area is cracked and missing pieces. The white reside is from the tape.
Step 1: Clean Up the Tape Residue With Acetone
If you are going to replace the battery, now is the time to do so, as you will have to cut the Sugru apart next time. Do it now instead of wishing you had done it...
Step 2: Mix the Sugru, and Apply It
Step 3: Smooth Out the Sugru, and Allow to Dry.
I did a finish smoothing by adding a little bit of water to my fingers and worked the Sugru.