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 (LiNi_0.5Mn_0.3Co_0.2O₂) 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

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