You have no idea as to the danger that thing has become.
It is the reason the airlines are considering banning them as carry-on items.
Do not try to fix it, and do not throw it in the trash.
Put it in a old METAL toolbox with a locking lid. Take it to your phone store.
( Most states require all battery sellers, must provide disposal. )
I know this is not the answer you wanted, but I learned the hard way.