The switching frequency is independent of the output current. You can have a charger running at 500kHz, or at 50kHz. The important thing is the output current and voltage and how they are supplied to the battery.
Depending on the type of battery, these parameters vary. You should check carefully the datasheet for the battery you are using to establish the best charging algorithm. There are also specialized IC's (from TI for example) which can determine the battery chemistry, based on measurements of voltage vs. test currents, and then they use the correct algorithm. But if you are going to only charge one type, you can implement a simpler circuit.