From Ballistic site:
Ballistic Performance Components EVO2 Batteries use lithium ferrous phosphate (LiFePO4) cells. The chemistry was originally discovered by John Goodenough’s research group at the University of Texas in 1996. Because of its relatively low cost, non-toxicity, excellent thermal stability, safety characteristics, good electrochemical performance, and high specific capacity it is the perfect chemistry for powersports applications. Simply, LiFePO4 cells can deliver an enormous amount of power over a very short time and then recover very quickly.