Hello. Well done for opening the phone up. By the looks of the photo, you have pulled the protective covering to the battery management system. It is what stores the data on the phone about the number of charge cycles and the battery health. The adhesive to pull the battery up is like this photo.
[image|3663097]
The smell is probably the lithium from the battery where some part of the battery has been pierced. You need to dispose of the battery correctly. They can't be recycled, but you can take it to an electrical recycle centre to dispose of it.
Hope this helps