Is this a battery leak?

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?

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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.