Improvement of Electrode/ Electrolyte Interfaces in Graphite/LiNi0.5Mn1.5O4 Batteries at High Voltage with Lithium Trimethyl Alkyl Borates As Electrolyte Additives

Monday, October 12, 2015: 15:00
101-A (Phoenix Convention Center)
B. L. Lucht (University of Rhode Island), M. Xu, L. Zhou (Silatronix), Y. Dong (University of Rhode Island), U. Totempudi (University of Rhode Island), A. Garsuch (BASF SE), and F. F. Chesneau (BASF SE)
Lithium trimethyl alkyl and aryl borates (LTMB) has been prepared and investigated as a novel cathode film forming additive to improve the performance of LiNi0.5Mn1.5O4 cathodes cycled to high potential (4.8 V).  Addition of LTMB to 1.2 M LiPF6 in EC/EMC (3/7) improves the capacity retention of graphite/LiNi0.5Mn1.5O4 cells cycled at 55 oC.  The added LTMB is sacrificially oxidized on the surface of the cathode during the first charging cycle.  The LTMBs can be used as a functional group delivery agent via reaction of trimethyl borate with of the appropriate lithium alkoxide.  Over 40 different LTMBs have been prepared and investigated.  Ex-situ surface analysis of the LiNi0.5Mn1.5O4 by Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), Transmission Electron Microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) reveals inhibition of electrolyte oxidation on the cathode surface and the presence of a borate based passivating layer.  The novel cathode electrolyte interface (CEI) leads to the performance improvements.