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
Original Replacement Battery 616-0407 For Ipod Nano 4 4g 4th Generation Mp3 Nano4+ Free Tools - Mobile Phone Batteries - AliExpress
Amazon.com: SWARK Battery 616-0406 616-0467 Compatible with iPod Nano (4th Gen) A1285 MP3, MP4, PMP Battery with Tools : Electronics