High power LED's

I have an old project in which an Arduino runs an array of high power LED's. One uses CREE XPG R5 emitters and the other one uses CREE's XML T6 emitters.

Its been a while now and I would like to redesign the same circuit but making it more lightweight, by running from a single lithium cell. Any suggestions for usable LED's that would be more efficient than the ones above?