Chosen Solution
I opened an iPad Mini earlier to replace the screen and found a shiny coating on one end of the battery. Does this look like a battery leak? Image The coating is already dry and feels fairly smooth. It only appears along the top of the battery along the edge that’s exposed under the LCD shield plate. There’s no sign of fluid below the battery or elsewhere in the iPad. This device has been repaired before. If it’s not from the battery, is there anything else in there that might leak? The LCD looks fine. There were no reported battery issues, either.
That does not look right.. Looks like something melted at the bottom of the battery.
Yes, you will probably have to replace the battery and any components that have been damaged by the leakage. It looks at though the battery acid has dried up.