On the outside, the Mi 9 Pro is identical with the non-Pro version; however, the internals have been refreshed with a Snapdragon 855+ SoC, up to 12 GB RAM and up to 512 GB storage, while the 4,000 mAh battery now supports 45 W wired / 30 W wireless / 10 W reverse charging options. There is also an improved speaker with the largest sound chamber among all Xiaomi handhelds.
https://www.notebookcheck.net/Xiaomi-launches-the-Mi-9-Pro-with-45-W-wired-charger-and-support-for-30-W-wireless-charging.435241.0.html