Study of the consumption of the additive prop-1-ene-1,3-sultone in Li [Ni0.33Mn0.33Co0.33]O2/graphite pouch cells and evidence of positive-negative electrode interaction

The consumption of the additive prop-1-ene-1,3-sultone (PES) in Li[Ni0.33Mn0.33Co0.33]O-2/graphite (NMC(111)/graphite) pouch cells during the first cycle and after hold periods at different cell potentials was measured using gas chromatography coupled with mass spectrometry (GC-MS). GC-MS measurements of the electrolyte of NMC(111)/graphite pouch cells during the first charge showed that the amount of PES consumed, and the cell impedance, increased with increasing starting concentration up to a starting concentration of 5 wt% and then seemed to slow down at higher starting concentration. Additive consumption measurements after holding periods showed that PES is consumed in measurable amounts at the positive electrode, suggesting that PES oxidizes at potentials as low as 4.27 V vs. Li/Li+ on the NMC(111) surface. Electrochemical impedance spectroscopy on symmetric cells as well as X-ray photoelectron spectroscopy of electrodes salvaged from NMC(111)/graphite cells after hold periods at various cell potentials strongly support the existence of a positive-negative electrode interaction. (c) 2016 Elsevier B.V. All rights reserved.