In Search of Electrolyte Additives for High Voltage LiNi0.5Mn1.5O4/Graphite Batteries

Wednesday, 8 October 2014: 08:30
Sunrise, 2nd Floor, Star Ballroom 7 (Moon Palace Resort)
S. A. Delp, J. L. Allen, and T. R. Jow (U.S. Army Research Laboratory)
Current lithium ion battery research has focused on increasing energy density. This can be accomplished by using electrode material with a higher gravimetric/volumetric capacity or using cathode material that operates at a higher voltage than that of today’s lithium ion batteries (~4V). One promising material, LiNi0.5Mn1.5O4 (LNMO), has a gravimetric capacity of ~140 mAh g-1 and an operating voltage of ~4.7 V, yielding an energy density of 658 Wh kg-1, compared to current state of the art (SOA) cathode materials LiCoO2 (518 Wh kg-1), LiMn2O4 (480 Wh kg-1) or LiFePO4 (578 Wh kg-1). However, the SOA electrolyte (LiPF6 in carbonate solvents) is not stable above ~4.5 V and undergoes oxidation reactions at the cathode surface. A possible solution to this problem is using additives that preferentially oxidize on the cathode surface and form a protective layer that prevents further electrolyte oxidation while still allowing lithium ions to transport back and forth. Current additives under investigation as well as results and interpretation will be discussed.