Lithium Tetrafluoro Oxalato Phosphate as Electrolyte Additive for Lithium-Ion Cells

Lithium tetrafluoro oxalato phosphate (LTFOP) was investigated as an electrolyte additive to improve the life of mesocarbon microbead (MCMB)/Li(1.1)[Ni(1/3)Co(1/3)Mn(1/3)](0.9)O(2) (NCM) cells for high power applications. With the addition of 1-3 wt % LTFOP to MCMB/NCM cells, the capacity retention after 200 cycles at 55 degrees C significantly improved. Electrochemical impedance spectroscopy showed that the LTFOP addition in the electrolyte increased the initial impedance but lowered the impedance growth rate during cycling. Aging tests at 55 degrees C indicated that the capacity retention of the negative electrode significantly benefited as a result of the LTFOP addition. Differential scanning calorimetry showed that the safety of the lithiated MCMB is significantly improved with the LTFOP addition. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3261738] All rights reserved.