Anodic Stability of Electrolyte Solvents and Additives at the Ni-Rich NMC Cathode-Electrolyte Interface in Li-Ion Batteries

Abstract

One of the key challenges facing Li-ion batteries with Ni-rich layered cathodes is the poor interfacial stability at both electrodes. Several recent reports have investigated the reactivity of the electrolyte at the surface of LiNixMnyCo1-x-yO2 (NMC) as a function of Ni content and electrolyte composition,1,2 but many of the complex processes taking place are not fully understood. In this work, we use a rapid electrochemical-based screening protocol3 to quantify the anodic stability of single-solvent electrolytes and additive-containing electrolyte solutions with respect to the fraction of Ni in the NMC cathode. The current that flows during a high voltage hold at 4.6 V vs Li/Li+ is found to be sensitive to the NMC surface chemistry, the degree of delithiation, and the composition of the electrolyte. Post-test XPS, solution NMR, and online electrochemical mass spectroscopy (OEMS) are combined to study the electrode- and electrolyte-dependent degradation products that are insoluble on the surface of the electrode, soluble in the electrolyte, and released as gas. The insights from quantification of the electrolyte anodic stability and the degradation signatures identified through this work highlight the importance of developing unique solutions to lower the interfacial reactivity of Ni-rich cathodes, which is a critical step to prolong the cycle life of high-energy Li-ion batteries.References Y. Zhang, Y. Katayama, R. Tatara, L. Giordano, Y. Yu, D. Fraggedakis, J. G. Sun, F. Maglia, R. Jung, M. Z. Bazant, Y. Shao-Horn, Energy Environ. Sci., 13, 183, 2020.J. Wandt, A. T. S. Freiberg, A. Ogrodnik, H. A. Gasteiger, Mater. Today, 21, 825, 2018.A. Tornheim, S. E. Trask, Z. Zhang, J. Electrochem. Soc., 163, A1717, 2016.