Detect power interruption on NodeMCU Im using a 5v 1A power supply and connected to VIN pin on the NodeMCU. I also use 18650 battery to keep NodeMCU running in case the power supply shuts off due to power interruption.

I'm planning to use the 5V from power supply, convert it to 3.3V with voltage divider and connect it to the gpio to detect power interruption.

Is it possible? Can the NodeMCU handle the current from the power supply?
Yes, you can.  You need to convert the 5V down to 3.3V with a voltage divider. You also need to consider how you are going to operate the ESP8266 when there is no power.