My iPod nano 6th generation is not holding its charge

I have had my iPod nano 16gb 6th generation for at least 6 years now I think. It works just fine except that I've noticed the battery seems to be dying much faster than it used to. I would be able to use it throughout the day on a full charge, and there would still be good amount of the charge left by the end of the day. Now I charge it fully, use it for a few hours, and the charge has depleted to about 50%. I was wondering if changing the battery was possible and if that would fix my problem? I love my current iPod and really don't want to upgrade to a newer version.