Voltage in Photon II's is 3V for yellow, orange and red. 6V for white, blue and turquoise. Green comes in either 3V or 6V.
Since a typical AA is 1.5 V, paranoid9999 is correct; the Photon II's do run at a higher voltage.
Which of course, brings up the possibility of using a 3V Li AA cell in the ITL. Frank C., why don't you try it out? It definitely increase the brightness. There is only one problem. While it is true that the Photon II LED's are all rated at 3V, and that the white, blue and turquoise were always run at 6V, and the green is now available at 6V as well, this does NOT mean all Photon II's can be run at 6V. The yellow, orange and red if run at 6V will have a drastically shortened LED life. This is due to the different colors being from different mfrs. The yellow orange and red are HP, IIRC, and the rest are from another mfr. (Nichia? Help me out here, Brock).
Therefore, if you run the ITL at 3V, it may work great, or blow the LED in a short while. Let us know what happens, OK?
My other concern would be the switch. The ITL seems to be an enlarged version of the Mag Light Solitaire. This was an OK light in use, but the switch sucked. It would tend to turn on accidentally, leaving you with a dead light unexpectedly. Further, if you didn't use the light for a while, the switch wouldn't function at first. You had to screw and unscrew it, whack on the light, and mutter imprecations before it would finally work. So, let us know how the switch behaves on the ITL, OK, Frank?
Onward through the fog, Walt