Swollen battery on iPod Touch 4 - what to do?

So an old iPod Touch 4 from 2010 has been sitting in a box in my cupboard for who-knows how long.. Anyway, the battery is now expanding. I’ve opened the case and removed the tray to the point where I can see the mainboard and the battery.

The battery is quite fat, to say the least! I’m terrified here and would like to get it out of my house as soon as possible - however, I want to separate it from the mainboard so that all of my personal data is protected. What is the best way to do this? I don’t have a soldering iron and the extent of my electronics wisdom is in building computers; can I slice the battery’s wires with a knife and unpeel it from the case? Or is there something else I should do?

Many thanks in advance for any advice!