(Invited) Modeling Cyclic Voltammetry during Solid Electrolyte Interphase Formation

The solid electrolyte interphase (SEI) is an electronically insulating film on anode surfaces in Li-ion batteries (LIBs), formed by the reaction of Li-ions with reduced electrolyte species [1]. The SEI leads to a reduction of the electrochemical current in heterogeneous electrochemical redox reactions at the electrode-electrolyte interface, thereby passivating the electrode surface [2]. Accordingly, the growth of the SEI is, in principle, self-limited. However, under realistic conditions, these phenomena are much more complex and not well understood. Towards a better understanding of SEI formation and passivation, we have developed a baseline quantitative model within Butler–Volmer electrode kinetics that describes the cyclic voltammetry (CV) of a flat macroelectrode during SEI formation [3]. We assumed that the SEI, which builds up electrochemically during CV, forms a homogeneous, single-phase, electronically insulating thin film due to the corresponding current. The model is based on a dynamically evolving electron tunneling barrier with increasing film thickness. Our framework allows both the qualitative, intuitive interpretation of the characteristic features of CV measurements and the quantitative extraction of physicochemical parameters through model fitting. In this contribution, we will introduce the basic concepts and equations of our baseline model, illustrate several examples, discuss its limitations, and provide a brief outlook for improvements and for more complex scenarios. Finally, comparisons are presented to exemplary CVs from the literature relevant to LIB science and to self-inhibition phenomena. References [1] P. Verma, P. Maire, P. Novák, Electrochim. Acta 2010, 55, 6332 [2] F. T. Krauss, I. Pantenburg, B. Roling, Adv. Mater. Interfaces 2022, 2101891 [3] H.-G. Steinrück, J. Chem. Phys. 2021, 154, 174703 [4] I. Bhugun, J.-M. Savéant, J. Electroanal. Chem. 1995, 395, 127