Domestic mobile phone charging voltage should be 5v, but the current size is not the same. Some 1.2A, some 1.1A. In fact, it is similar, the market charging treasure, generally have two charging ports, a 5v, 1A; One 5v, 2.1A. It's just a normal charge and a quick charge.
You can see the upper limit is 2.1A and the lower limit is 1A. This is probably the safe current range, but you can use as little as possible without high current. It is no problem to charge any mobile phone on the market with Xiaomi's charging bank