Understanding Modulus Variation of the Active Layers of Silicon Composite Electrodes.

The variation of the effective modulus of silicon composite electrodes, which is a fundamental feature to analyze the coupled mechanical–electrochemical behavior of Si-based electrodes in high-capacity lithium-ion batteries, remains qualitatively controversial. To clarify the contradictory experimental results, numerical modeling of a representative volume element with silicon particles, carbon-binder domains (CBDs), and pores has been performed for the lithiation process. The key parameters for modulus variation were identified and evaluated. A mesostructure change is proposed to be a crucial mechanism that affects the modulus variation, and silicon softening is another key mechanism. Silicon softening and the decreasing CBD volume fraction collectively result in a decrease in the effective modulus of the composite, whereas an increase in the silicon volume fraction along with a decrease in porosity has the opposite effect. The findings of this work provide an in-depth and fundamental understanding of the mechanical properties of silicon composite electrodes. [ABSTRACT FROM AUTHOR]