Phase-Field Modeling of Solid Electrolyte Interphase (SEI) Evolution: Considering Cracking and Dissolution during Battery Cycling

Abstract

Lithium-ion battery (LIB) degrade over time, which compromise its electrochemical performance and mechanical integrity, eventually battery safety. The evolution of solid electrolyte interphase (SEI) layer, which is a passivation layer forming and growing between electrode and electrolyte, is one of the main reasons for the above degradation of LIB. The performance and longevity of LIB highly depend on the stability of the SEI. Unfortunately, it is believed that the SEI layer is not electrochemically and mechanically stable due to the dissolution and cracking of the SEI during the de/lithiation process. Up to date, very few studies have investigated the dissolution and cracking of the SEI layer during the lithium-ion diffusion. In this work, a phase field model is developed to provide insight on the interaction effect of cracking and dissolution of the SEI layer on LIBs performance. We assume that the SEI layer is formed by different solid species precipitated from the electrolyte, which are not stable during the de/lithiation cycling. SEI layer experiences stress concentration and volume change, which lead to the cracking of layer. In the meanwhile, the SEI species may have further reactions with the electrolyte which may lead to the dissolution. The cracking of the SEI layer results in more surfaces to react with electrolyte, and further dissolution, as shown in Figure 1. Moreover, we carry out experiments to focus on imaging the SEI as well as battery performance degradation during SEI formation and evolution. Figure 1