It sure won't be a microUSB port. To charge a middle-of-the-road 2500mAh capacity battery in, say, 10 seconds, you must flow something like 70A @ 5V, and that's ignoring the fact that capacitor charge curves are of the exponential decay variety (i.e. drastically higher initial power draw).

(A real-world application would probably kick up the voltage and lower the current, but USB is always 5V)