| Abstrakt: |
Background: Failure of polymer/active material interfaces, in commercial composite electrodes, is one of the mechanisms by which batteries loose capacity. In spite of the importance, no systematic study to characterize and understand the interface failure behavior of battery electrodes exists at present. Objective: The objective is to develop an experimental method to characterize the fracture behavior of polymer/active material interfaces in rechargeable battery systems. Methods: Axisymmetric blister test samples were prepared by depositing PVdF (polyvinylidene fluoride) polymer on SiO2 surface with a series of nanofabrication processes. The PVdF/SiO2 samples were then pressurized in a novel electrochemical cell until the film delaminated from SiO2. The mechanical response of the pressurized film was measured, and the PVdF/SiO2 interface fracture was characterized in terms of critical energy release rate Gc. The fracture surfaces were analyzed to determine failure mechanism. Results: The X-ray photoelectron spectroscopy and scanning electron microscopy analysis of the fracture surfaces showed that the crack path was predominantly at the PVdF/SiO2 interface, i.e., the mechanism of failure was adhesive. Hence, the measured Gc = 2.46 J/m2 can be considered as the energy required to break the bonds to separate PVdF from SiO2. Using this Gc value in a finite element model, the failure pressure of plane strain blister samples has been predicted successfully. Conclusion: We have experimentally demonstrated that Gc is a fundamental fracture parameter, and G = Gc as a failure criterion can be used to predict PVdF/SiO2 interface failure irrespective of sample geometry, which can be extended to battery electrodes. [ABSTRACT FROM AUTHOR] |
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