Mobile phone battery have a protective board, which will be APO (Automatic Power-Off) in special occasion.
A. Overcharge protection. It will automatically stop charging when battery full.
B. Overdischarge protection. When battery discharged to 3.2V, it will automatically stop.
C. Short-circuit protection.
It means the battery will be provided with automatic short-circuit protection when it happens to short circuit. That is to say, generally the battery needs about 2-3 hours to reach full charging. Then the circuit will be disconnected, so it makes no sense to continue charging.