No, please don't do that. If you have a good grasp of how a battery charger controls the voltage/current during a charge cycle then you can pretty safely rig up something that more or less duplicates what a charger does, but just by asking this question that's a pretty good indication you don't understand it well enough yet.
Get it wrong and at best you'll damage the cells, at worst you'll start a fire and end up in the hospital.
Output voltage: 12-35V (adjustable)
Output current range :0.5-5A (100W MAX) (continuously adjustable)
1. Step-up structure, Wide input voltage range (input less than output)
2. Constant current and voltage, Used to drive high power LEDs, and to charge the battery
3. Efficiency as high as 92%
4. Can be used for laptop power supply (voltage 16-20V)
5. Even the Step-up structure breakdown, Will not damage equipment, security design
6. With input reverse and undervoltage protection
7. Aluminum shell potting design, shockproof, Waterproof, Heat-Sink, harsh environments adaptable
8. Pluggable terminal design, easy assembly and disassembly, wiring more convenient
9. Can be Parallel work in power is not enough occasions
If you have a DC supply, and can set it to a fixed open circuit voltage of 4.21-4.22v, and the current can be limited to a safe range, then it's pretty safe to use. But it'll take much longer than a proper charger that follows the correct algorithm.
In the CV phase, it should really be maintaining a fixed voltage across the cell of 4.21-4.22v, to do that will require a higher open circuit voltage. As the cell charges and its voltage rises, it'll require less voltage from the charger to maintain that target 4.21-4.22v. Unless you want to babysit the charger and 'drive' it manually, constantly monitoring volts/amps and adjusting it the whole time, just buy a charger that does it properly.