can my 2015 mac battery be replaced?

you should use the link provided by ku4hx to first see if you can get an actual apple battery and apple service.

if that proves un-doable, I would recommend going to OWC’s website. they provide quality batteries. and there are DIY battery replacement videos on their site. if the DIY solution is outside your skill set, they do also offer service for apple products.

Possibly: Mac Repair & Service - Apple Support

I suggest using an Apple battery as others don't meet Apple's strict standards and can often be substandard in performance.