iPad Air batteries
Can I use the battery from an iPad Air (1) in an iPad Air 2 or vice versa
Question marked as
Likely no.
Your iPad contains no user-serviceable parts. If your battery requires service, this should be entrusted to Apple or an Apple Authorised Service Provider (AASP).
Genius Bar Reservation and Apple Support Options - Apple
iPad Repair - Official Apple Support
Be aware that if you open the iPad, or attempt a self-repair, you will forfeit all service support from official Apple sources. If the internal battery is disconnected, the TouchID sensor must be reset - this being a procedure that can only be performed by Apple or one of the AASPs.