Are you sure you can use that? Your MacBook comes with a USB-C power supply. The 29W USB-C power adapter that came with your MacBook specifically puts out 14.5V at up to 2.0A.
This is what you were thinking of using?
https://shop.antigravitybatteries.com/products/micro-starts/xp-1/
It looks like there are 12V and a 19V coax outputs, and I can't see how those are going to work. There's nothing that can really translate that to USB-C, and it needs to be a smart supply that meets the USB Power Delivery spec. It's got a couple of 5V USB-A outputs, but you would need a USB-A to USB-C cable or a combination of cables and adapters to do that. Apparently it can take in 5V from a USB-A supply, but I think the charging will be very slow.
https://mashable.com/2015/04/13/apple-new-macbook-external-battery-charging/
I think perhaps a more practical solution would be one of those big USB-C power packs. Here's an article on them:
The Best USB-C Battery Packs and Power Banks: Reviews by Wirecutter | A New York Times Company