Apple has its own smart battery cases for iPhone XS and XR
 

Yes, the rumors and leaks were true -- Apple has a new battery case after a lengthy absence, and it appears to have learned a few lessons in the process. The Smart Battery Case for iPhone XS, XS Max and XR extends your handset's battery to as much a...

https://www.engadget.com/2019/01/15/...-iphone-xs-xr/