Study of Microstructural Evolution and Strain Analysis in SiOx/C Negative Electrodes Using In-situ X-ray Tomography and Digital Volume Correlation

Abstract

Increasing the silicon content in batteries is expected to enhance their capacity. However, its implementation comes with challenges, as silicon exhibits a large volumetric expansion. This is a significant factor contributing to the decreased lifespan of these batteries, one of the critical degradation mechanisms from a mechanical perspective is the delamination of electrode structure. The cyclability of these anodes is noted to be influenced by the interaction between the binder and particles during battery cycling. The heavy local strain experienced by particles in these electrodes often leads to binder failure, resulting in particle detachment, or delamination over multiple cycles. A good understanding of the local evolution of the strain is essential in advancing the mechanical modelling of the degradation mechanism and in realizing the complete potential of silicon-based electrodes. In this work, in situ global and local strain measurements were performed by combining synchrotron tomography with Digital volume correlation (DVC). The measurements showed that there is significant local strain in these electrodes which can lead to delamination. In addition to this, the spatial variability of the composite electrodes was characterized by estimating the characteristic length to strain, which can be used to replicate the strain field and model the delamination.