The improved battery charging feature that comes with MIUI 12.5 is a novelty intended to extend the direct battery life of your Xiaomi phone. Artificial intelligence will learn how to charge your device and use habits for longer battery life. For example, charging at night will take longer and your battery will stay healthy for longer.
Xiaomi phones came with a lot of innovations and optimizations with MIUI 12.5, but Xiaomi does not seem to explain them all. With the 21.2.1 daily version of MIUI 12.5, this feature has begun to be tested for a few models. It is not yet known which devices will support this feature, but it is certain that flagship devices such as Mi 11 and Mi 10 will have priority.