Role of the binder in the mechanical integrity of micro-sized crystalline silicon anodes for Li-Ion batteries

Stable electrochemical performance and mechanical integrity for large-volume-change alloy anodes with high capacity remain a formidable challenge in battery industries. The roles of diverse binders, crucial for the stability of electrode microstructure in alloy electrodes, are not yet fully comprehended. For a good understanding of interactions between binders and active materials, in this work, by turning real silicon-based electrodes with irregular geometries into constrained silicon micropillars with regular ones, chemomechanical functions of binders for silicon electrodes are conducted by experimental observations and numerical simulations. The observations suggest that the addition of binder can enhance the fracture behaviors of silicon micropillars and hinder the debonding of the lithiated silicon for all solid, isometric-hollow and anisometric-hollow geometric designs. Accordingly, the constrained electrodes have more superior electrochemical performance than free-standing ones, which is ascribed to the improvement of mechanical integrity. The results emphasize the vital roles of suitable binders in structural stability and provide an instructive design for real composite alloy electrodes in Li-ion batteries.