Here’s how I was able to open the battery from my Dell. I had to take it apart because the locking mechanism was broken. I decided to fix it by using the locking mechanism from another similar dead Dell battery.
I wasn’t sure if I can open the battery because it looked sealed.
To my surprise, it wasn’t difficult but you have to be very careful. If something goes wrong you can (and most likely will) destroy the battery or will not be able to assemble it back together. Proceed on your own risk.