Replaced the dead battery in an old iPod Nano I bought (really wanted a cheap Product Red one) and not even 2 days later the replacement battery expanded. I would call this
iPod Nano 2nd Gen Battery Replacement
iPod Nano Battery 2G 2nd Gen Replacement 400 mAh
Original New Replacement Battery For Ipod Nano2 2g 2nd Generation Mp3 Li-polymer Rechargeable Nano 2 616-0282 Batteries + Tools - Mobile Phone Batteries - AliExpress