Adhesion strength of the cathode in lithium-ion batteries under combined tension/shear loadings

To understand the failure mechanism and establish reliable deformation tolerances for lithium-ion batteries under mechanical loading, accurate testing and modeling of individual components are indispensable. This paper is focused on one of the most common failure scenarios, which is the de-bonding between the coating material and the current collector. A new specimen is carefully designed to measure the failure strength of the coating-foil interface. The electrode is bonded to two acrylic substrates using liquid formula glue for one side and gel formula glue for the other. Compared with conventional peeling tests using double-sided tape, the major advantage of this new specimen is that it realizes conducting shear tests. Using this special specimen, the failure strength of the coating-foil interface is obtained under combined tension/shear loadings. The new method is less susceptible to the testing conditions such as loading rate. For the cathode studied in this paper, the shear strength of the coating-foil interface turns out to be almost twice its tensile strength, which emphasizes the necessity of carrying out combined tension/shear loading tests. Moreover, a combined adhesion and cohesion failure mode is observed at the failure interface, where with larger shear component, the adhesion failure becomes dominant.