https://www.cnet.com/news/apple-now-makes-smart-battery-cases-for-the-iphone-xs-and-xr/

They also have that familiar battery bulge that was on previous models. (Here's my review of the first one for the iPhone 6S.)

Like Apple's previous line of smart battery cases, they'll charge via Lightning independently, show battery status in iOS under the "battery" widget, and discharge the case's battery before tapping into the phone's battery supply.