Little battery after screen replacement

I have huawei P8 lite and tried to replace the screen.

But my mistake I ripped the battery adhesive and when trying to pry up gently the battery, it got swollen and Ruined so from the fear of blowing up, I spilled a cold water on the battery.

I checked and figured out that I have all I need to reassemble the phone if I’ll buy a new battery except 1 thing - maybe a little battery? a circle shape thing that I don’t really know what’s that.

I didn’t find how to upload a picture here so here is a link for the picture: https://ibb.co/jQhQKQ