Chemical-mechanical modeling of SEI on Silicon particles

Kurzfassung

Lithium-ion batteries combine good long-term stability and performance. These properties havemade Lithium-ion batteries the benchmark energy storage for hand-held electronics and electricvehicles. Nevertheless, there is an industrial urge to further push the technology towards highercapacities and longer battery life. Increasing the lifetime of Lithium-ion batteries is currently afundamental challenge for battery research. One important mechanism contributing to the capacity loss isthe growth of a solid-electrolyte interphase (SEI) during storage and cycling.Silicon anodes are a promising approach for further increasing the capacity of Lithium-ion batteries,as they show the tenfold theoretical specific capacity of the currently used graphite anodes.However, the SEI growth is even more severe for silicon anodes: large volume expansions of~300% exert high mechanical stresses and fracture the SEI. The resulting cracks subsequentlyexpose the pristine electrode leading to SEI reformation and thereby continuous capacity decrease.In order to further understand SEI growth, our group developed a model describing SEI growth ongraphite during storage [1-4]. Thereby, the diffusion of neutral Li interstitials from the electrode to theelectrolyte was found to cause the long-term growth of the SEI [1,2]. Additionally, a thermodynamical framework was developed to describe the coupling of chemical,electrical and thermal effects [5]. We extend this model for mechanical effects and investigate how theinterplay of chemistry and mechanics impacts stability and growth of the SEI during battery operation.Understanding these relationships identifies critical operating conditions and aid in the design ofnew electrodes. Thereby, batteries with higher capacity and long-term stability can be developed.1. Horstmann, B., Single, F. & Latz, A. Review on Multi-Scale Models of Solid-Electrolyte InterphaseFormation. 13, 1\u20138 (2018). doi:10.1016/j.coelec.2018.10.0132. Single, F., Latz, A. & Horstmann, B. Identifying the Mechanism of Continued Growth of the Solid-Electrolyte Interphase. ChemSusChem 1\u20137 (2018). doi:10.1002/cssc.2018000773. Single, F., Horstmann, B. & Latz, A. Revealing SEI Morphology: In-Depth Analysis of a ModelingApproach. J. Electrochem. Soc. 164, E3132\u2013E3145 (2017). doi:10.1149/2.0121711jes4. Single, F., Horstmann, B. & Latz, A. Dynamics and morphology of solid electrolyte interphase (SEI).Phys. Chem. Chem. Phys. 18, 17810\u201317814 (2016). doi:10.1039/C6CP02816K5. Latz, A. & Zausch, J. Multiscale modeling of lithium ion batteries: Thermal aspects. Beilstein J.Nanotechnol. 6, 987\u20131007 (2015). doi:10.3762/bjnano.6.102