Li-Ion Cell Charger Tips:
Are you aware that a cellphone charger, although it is called a charger, is actually NOT a charger ?? It is just a power supply. In all phones there is a chip that sits between this adapter and the battery and this chip takes care of the actual charging. Did you know that Lithium based cells can EXPLODE / CATCH FIRE when not charged properly ?

Please get a proper charger circuit like this TP4056 based module it will fit all your requirements, has indicators, you can set the maximum charging current with a resistor.
Be safe, just get such a module it costs almost nothing.

Another item to consider if you only charge 18650 cells is this one.