which battery is suitable for macbook air 13 inch early 2015

Mac Service & Repair - Apple Support

The only reason to use an aftermarket battery is when a Mac becomes obsolete and no longer eligible for authorized repairs. Installing an aftermarket battery will render it ineligible for authorized repairs.

This is an often recommended vendor. Please note that no replacement battery will be OEM quality

https://eshop.macsales.com/installvideos/macbook_air_2015/