Decomposition reactions involving (1) the electrode active material, (2) conductive carbon and (3) binder, as well as (4) the electrolyte solvent, (5) salt, along with (6) eventual additives, will be discussed. The Ni-rich layered mixed transition metal oxides (LiNixCoyMnzO2) are currently the best performing Li-ion cathode materials on the market. Surface phase transformations during the initial cycles however lead to composition- and potential-dependent evolution of O2, which is shown to be strongly related to the Ni-content of the oxides.1 Decomposition of electrode-processing-related residues and of electrolyte solvents leads to evolution of CO2, particularly in the first cycles, and initiates further chemical reactions with electrolyte salt (e.g. observed as HF and POF3).2 Electrolyte additives (e.g. vinylene carbonate, silyl-phosphates, etc.) can however suppress these side-reactions, e.g. by scavenging intermediate side-products and OEMS provides further verification of their reaction mechanism. In addition, electrolyte additives may also be exploited as chemical probes enabling operando monitoring of the degradation of other cell components, such as for example the electrode binder.3
- D. Streich, C. Erk, A. Guéguen, P. Müller, F. Chesneau, E. J. Berg, Submitted.
- A. Guéguen, D. Streich, M. He, M. Mendez, F. F. Chesneau, P. Novák, E. J. Berg, J. Electrochem. Soc. 163 A1095-A1100 (2016).
- A. Guéguen, C. Bolli, M. Mendez, F. F. Chesneau, E. J. Berg, Submitted.