Do you mean you want to make a charger for the phone? Typically the charge control circuitry is in the phone. If you're charging the battery outside of the phone then it may have saftey cutoffs but it can't control it's own charging, the phone has to do that.
What is typically called a phone charger nowdays is nothing of the sort, it's nothing more than a regulated 5 volt power supply.
If you're just trying to create a portable charger for the phone all that needs to be done is to use as large an external battery pack as you desire and feed it into a decent SEPIC converter to produce a regulated 5V output, the output needs to be nothing more complicated than the USB charging cord that the phone already uses.
Making one of these yourself is probably a waste of time, they're commercially available, and believe me they probably thought of a few more things than you did about what makes a good circuit =)