Identification of Organic Species Generated at Each Electrode during Potentiostatic Hold of a Two-Compartment Lithium-Ion Cell By Liquid Chromatography-Electrospray Ionization Mass Spectrometry (HPLC/ESI-MS) Analysis

Abstract

Chemical structure identification of electrolyte decomposition species formed during aging of a lithium-ion battery can help deepen our understanding of the various reaction mechanisms occurring inside the battery, which in the long run can help in a rational design and synthesis of future electrolyte formulations. In this work, a two-compartment cell was made following the design proposed earlier by different groups.1-2 Essentially, a non-porous Li+-ion conductive glass ceramic disc was used as separator instead of the traditional porous polypropylene separator. This will eliminate any cross-talk between the electrodes and identify species formed at anode and cathode individually. NMC532 (LiNi0.5Mn0.3Co0.2O2) was used as the cathode, graphite was used as the anode, and 1.2 M LiPF6 in EC/EMC (3/7 wt./wt.) was used as the electrolyte. For identification of decomposition species, we used HPLC/ESI-MS which has been shown multiple times as a viable technique for identification of decomposition species which are typically present in small concentrations.3-4 Since only molecular weights of the species can be obtained via ESI-MS, structural identification was performed using a combination of isotope-peak analysis and already proposed reaction mechanisms. The results from two-compartment cell were also contrasted with a traditional lithium-ion cell made with porous polypropylene separator and aged under similar conditions. This abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02- 06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. References Metzger, M.; Strehle, B.; Solchenbach, S.; Gasteiger, H. A., Origin of H2 Evolution in Libs: H2o Reduction Vs. Electrolyte Oxidation. Journal of The Electrochemical Society 2016, 163, A798-A809.Vadivel, N. R.; Ha, S.; He, M.; Dees, D.; Trask, S.; Polzin, B.; Gallagher, K. G., On Leakage Current Measured at High Cell Voltages in Lithium-Ion Batteries. Journal of The Electrochemical Society 2017, 164, A508-A517.Takeda, S.; Morimura, W.; Liu, Y.-H.; Sakai, T.; Saito, Y., Identification and Formation Mechanism of Individual Degradation Products in Lithium-Ion Batteries Studied by Liquid Chromatography/Electrospray Ionization Mass Spectrometry and Atmospheric Solid Analysis Probe Mass Spectrometry. Rapid Communications in Mass Spectrometry 2016, 30, 1754-1762.Laruelle, S.; Pilard, S.; Guenot, P.; Grugeon, S.; Tarascon, J.-M., Identification of Li-Based Electrolyte Degradation Products through Dei and Esi High-Resolution Mass Spectrometry. Journal of The Electrochemical Society 2004, 151, A1202-A1209.