Macbook Battery swollen and completely broken

I've had my macbook for almost 3 1/2 years now, and I've loved it. This is a recent problem, and is NOT caused by a fall or any tramautic damage: the laptop has been sitting on a desk for the past two or so months, and has only been moved rarely and never suffered any damage, major or minor, during this time period. I think this battery problem could be a long-term design defect(?). The warran has long expired, but I was wondering if the Apple store could help? I've already made an appointment, so hopefully something will get fixed 😀