Are you charging the iPad while using the charger that came with the iPad and do you have that plugged into a known good wall outlet? You should not need a new battery for an iPad air yet. Way too soon.
First thing to try is to reset your device. Press and hold the Home and Sleep buttons simultaneously until the Apple logo appears. Let go of the buttons and let the device restart. See if that fixes your problem.
Make an appointment at an Apple Store to have your device examined by a technician. Or contact Apple Support.