I had a broken tablet, so I got it from there… but as far as I see from these old pictures a 3.7V 3000mAh battery with size 2867144 what was installed here. If you unable to find exact same size then I would go with any fitting size which is closely matching.
Obviously, if you do not know what you are doing then please DO NOT play with the battery! It can cause fire or other type of damages!!!
PS: quick search gave me this (I have not tried to install it or buy it - this is only a search result)
ONLY FOR EXPERIENCED ELECTRICIANS!
It is not impossible to clean the removed connector from the panel parts and then glue the connector back on the panel. It depends how much connection is left on the board (you might able to clean a bit of green carefully to increase connection size) with a bit of experience you can solder it back/together again. The power and ground needs better connection since it needs to able to carry the current. The RPM signal has the least connection size on this side of the board but it needs only a bit of connection.
Other possibility to bring from the board other side the 3 fan connection points with some tiny cables but that is more labour intensive and you might need to cut a bit from the metal panel to make space of the cables.
Anyway it is a doable job for an experienced repair person.
I have also ripped off the connector and only realized when I wanted to put together.
You do not need to separately remove the back and the frame. You can do it in 1 step if you start around the screen and remove the frame and back together.