Can you please suggest the IC for designing the DC voltage booster 3.7volts to 18 volts?

 

First, I present the viewpoint documented by Robert Heinlein:
TANSTAAFL
Or it's English translation, There Ain't No Such Thing As A Free Lunch.

In this case, when you boost the voltage, you decrease the current. What is your load restance? And how much current does the load require? Knowing these two parameters, you can calculate the required current.

 

I would run right to the Simple Switcher page, but there is no amount of current or power or impedance defined.