Silicon Nanowires as Anodes for Lithium-Ion Batteries: Full Cell Modeling

Abstract

Silicon (Si) anodes attract a lot of research attention for their potential to enable high-energy density lithium-ion batteries (LIBs). Many studies focus on nanostructured Si anodes to counteract deterioration. Herein, LIBs are modeled with Si nanowire anodes in combination with an ionic liquid (IL) electrolyte. On the anode side, elastic deformations to reflect the large volumetric changes of Si are allowed. With physics-based continuum modeling, insight into usually hardly accessible quantities like the stress distribution in the active material can be provided. For the IL electrolyte, the thermodynamically consistent transport theory includes convection as relevant transport mechanism. The volume-averaged 1d+1d framework is presented and parameter studies are performed to investigate the influence of the Si anode morphology on the cell performance. The findings highlight the importance of incorporating the volumetric expansion of Si in physics-based simulations. Even for nanostructured anodes — which are said to be beneficial concerning the stresses — the expansion influences the achievable capacity of the cell. Accounting for enough pore space is important for efficient active material usage.