Measurement of Binder/Active Material Interface Fracture in Rechargeable Batteries and the Effect of Oxide Coating

Abstract

Interface fracture is a critical issue for next-generation rechargeable batteries. The integrity of the binder/active material interface is essential for successful battery operation, and the interface failure is a major capacity fade mechanism. In spite of the importance, no systematic study on understanding/characterization of this issue exists at present. Here, the interface fracture was studied using a model polyvinylidene fluoride (PVdF)/Si system due to its importance in future Li-ion batteries. The interface failure was characterized in terms of critical energy release rate Gc using an experimental technique based on blister test and Michelson interferometry. The effect of the oxide layer on the interface fracture was also quantified. The critical energy release rate Gc of PVdF/Si interface is 0.55 ± 0.14 Jm−2, and the presence of oxide layer at the interface increased the Gc by an order of magnitude higher, i.e., the Gc of PVdF/SiO2 interface is 2.46 ± 0.40 Jm−2. The scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis of the fracture surfaces showed that the crack growth mechanism is adhesive for both interface systems, and the strong adhesion of PVdF to SiO2 surface is attributed to the nature of bonding, i.e., a higher concentration of silanol (Si-OH) group on the SiO2 surface as compared to the Si surface to which PVdF forms a bond with. The experimental methodology proposed here is more general and can be used to study the fracture behavior of interfaces in other electrode systems and with other battery chemistries.