Regensburg 2025 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 32: Transport in Materials: Diffusion, Charge or Heat Conduction

MM 32.1: Vortrag

Donnerstag, 20. März 2025, 15:00–15:15, H22

Kinetic analysis of lithium transport in silicon anode using operando optical microscopy — •Shihao Wei, Monica Mead, Yug Joshi, and Guido Schmitz — Institute of Materials Science University of Stuttgart, 70569 Stuttgart, Germany

The performance of silicon(Si) anodes in lithium(Li)-ion batteries is significantly influenced by the kinetics of Li insertion and migration, particularly at the phase boundaries formed during cycling. Traditional techniques, such as EIS, SIMS, and NMR, are limited in providing detailed kinetic information at internal phase boundaries. This study proposes a novel approach to measure Li migration across phase boundaries in Si-based anodes. First, reflectance spectroscopy is employed to examine the optical response of Si thin films sputtered onto copper current collectors at various charge states, revealing reversible electrochromic behavior and the effect of Li content on spectral characteristics. Based on this, operando optical microscopy is developed to track the lithiation front, by using SU-8 photoresist as a patterning tool. The lithiation process is predominantly governed by diffusion-controlled parabolic growth, with minimal evidence of interface-controlled linear growth. Interestingly, applying the same method during delithiation, a significant slow-down of delithiation front appears. In addition, temperature-dependent diffusion behaviors are explored, quantified with an Arrhenius-like model. By altering the geometry of the photoresist patterns, the transport dynamics are analyzed under two distinct scenarios: a 1D semi-infinite planar configuration and a 2D finite circular configuration.

Keywords: Chemical Diffusion; Si; Li-ion Battery