Someone tell me if my concept is clear about voltage?
1.5 V is a measure of electrical potential.  It is not energy, so electrical potential energy doesn't make sense.

One way to look at EMF is the potential of charge to do work.  3 Coulombs at a potential of 5 V can do 15 joules of work when flowing down to 0 potential.  This is like a brick can do work while falling from a high spot (high gravitational potential) to a low spot (lower gravitational potential).

A battery is a pump for charge.  As some charge flows from the higher to lower potential, the battery keeps replacing that charge at the high potential.  This is like a pump moving water uphill so that you can run a water wheel from it.  The water wheel is your circuit that is using power from the water to perform its function.  The battery is the pump that takes the water from the bottom of the water wheel (at low potential) and moves it back up to the top (at high potential), where it can be used to run the water wheel again.