If the power supply provides 5V (standard USB charger) and the device requires 20V (according to davidgo) it's very, very, very unlikely it will work (unless the laptop can handle a 5V power supply)!
But it will work the other way around, you can use you're laptop power supply to charge you're S9 according to those specs. (which I just saw davidgo already suggested in his answer)
In general lower voltage won't cause any damage within the device (laptop), but it might happen that the device won't charge and/or turn on at all. It depends on the specification and the tolerance of the on the power supply and the device.
But there is a chance that the power supply will be damaged if it doesn't have sufficient protection against loads that are too high. But this happens because of the current (if the device requires more current then the power supply can provide) not because of the voltage.
Regarding the charging duration, the current is the main factor here. Too little current might prolong the charging time or might cause the device not to charge at all depending (because high requirements on current will cause the voltage to break down in the power supply).