Drone Battery Modification: Extending Flight Time with Removable Phone Batteries, 3.7V 550mAh Li-Po

Hello, I bought a drone, but for a short time, it is powered by a Li-Po battery, 3.7V 550mah, 2Wh, 15C, charge 1A max. I would like to add cells, i.e. stick batteries from the phone, but I am VERY beginner electronics wants to spoil. How do I attach the second battery to be removable, e.g. from the bottom of the drone on an elastic band? I would like the whole modification to be the least invasive and easy to implement. The battery from the phone is quite light so I think it would be possible ...
This is the general outline of the plan .. will someone suggest?

Thanks in advance and waiting for answers

czerstwyed wrote:

How can I load the second battery to be removable, e.g. from the bottom of the drone on an elastic band? I would like all modifications to be as minimal as possible and easy to implement. The battery from the phone is quite light so I think it would be possible ...

Purchase a larger capacity battery for this application and replace the current one. The battery from the phone, in this application, will not work well (it is not suitable for quick discharge with high current). The idea of connecting two different lithium batteries in parallel is quite dangerous.
When replacing the battery with a larger one, think about how the drone will react to its greater weight, before buying, make a simulation by attaching an equivalent load.