Charging a 18650 battery using a 5V charger
ATTENTION! If you overcharge a lithium-ion cell it can explode and cause some serious damage. Also if you get the cell into undervoltage condition and try to charge it again it will explode too.

This is why lithium cells should never be used without a battery management system which supervises every cell condition. 

Lithium cell should be charged with a CC-CV algorithm. Every cell is different about the end of charge voltage, under voltage border, maximum currents and so on. Without out knowing anything about the cell I would not risk burning down my house while experimenting with lithium-ion cells.

Mixing different cell types can also be dangerous because there can be compensations currents which are not intended.

(Source: I work at a company which develops battery management systems and builds battery packs. Even with a high experience we have burning cells from time to time for example when we get packs back from a customer and do not know what he has done with it.)