Maximum *charging* voltage for Li-Ion battery
But at this point youre charging with way too much current, or want to really fast charge, im not sure this is actually safe for the chemistry but i maybe mistaken, it could be fine. The point is the voltage sets the current, and with a 4.5v your more then maxing the current, the reason you dont want to put 4.2v on a 2.5 cell is because the current will be too high.