Can I make this batter ahead of time & store in the refrigerator for 1-2 days?

I wouldn't recommend it because the only leavening comes from the whipped egg whites. They will begin to lose volume rapidly, and the batter needs to be used right away once they are folded in. That said, you could probably mix up everything except the egg yolks and whites, and add them the day you plan to make the pancakes. Whisk the egg yolks, then whisk in a bit of batter before adding them to the rest of the batter so that they incorporate evenly. Finally, whip the whites and fold them in.