Estimating Surface Layer Thickness on Electrodes from Lithium-Ion Batteries By Surface Analysis

As energy density and operational requirements increase, traditional battery electrolytes are pushed to the breaking point. Silatronix® organosilicon (OS) electrolyte materials are a key building block in next-generation Li-ion systems. Silatronix® has developed and synthesized an entirely new class of OS molecules with superior thermal, chemical, and electrochemical properties including lower anode and cathode impedance and reduce gas generation after high temperature cycling 1 . The surface layers that form on the electrodes during battery aging are one of the main factors affecting the performance of lithium-ion batteries and can be key to understanding battery electrochemistry 2 . Thicker surface layers may lead to higher impedance while composition of the surface layer can also affect impedance. In this work, X-ray photoelectron spectroscopy (XPS) was used as the main tool to estimate the thickness of the surface layers on both cathode and anode (Figure 1). The anode surface layer thickness was estimated using depth profiling through the decomposition layer to reveal signal from the bulk anode. The cathode surface layer thickness was estimated using the PVDF signal from the bulk cathode and calculating the attenuation of the pristine signal due to the overlying decomposition species 3 . Utilizing these methods, the surface layer thicknesses on the anode and cathode were estimated after formation, after HT cycling and after HT storage 4 . The trend of anode surface layer thickness with aging was explored, as well as the effects of different OS materials on surface layer thickness after different stages of aging, and the correlation between the cell impedance and surface layer thickness. References : Guillot, S.L.; Usrey, M. L.; Peña-Hueso, A.; Kerber, B.M.; Zhou, L.; Du, P.; Johnson, T. Reduced gassing in Lithium-ion batteries with organosilicon additives. Journal of The Electrochemical Society 2021, 168, 030533-030543. Wang, A.; Kadam, S.; Li, H.; Shi, S.; Qi, Yue. Review on modeling of the anode solid electrolyte interphase (SEI) for lithium-ion batteries, npj Computational Materials 2018, 4, 15. Cumpson, P.J. The Thickogram: a method for easy film thickness measurement in XPS. Surf. Interface Anal. 2000, 29, 403-406. Niehoff, P.; Passerini, S.; Winter, M. Interface investigations of a commercial Lithium-ion battery graphite anode material by sputter Depth Profile X-ray Photoelectron Spectroscopy. Langmuir 2013, 29, (19), 5806–5816. Figure 1