Xindong Yu, Kaiyuan Ji, Weiran Fu, Xianhang Lu, Yuanhua Xie, Dechun Ba, Kun Liu, Northeastern University, Shenyang, China
Flexible films are typically fabricated by depositing metallic layers onto polymeric substrates, thereby combining the electrical conductivity of the metal with the flexibility of the underlying polymer, and are widely employed in applications such as power batteries and aerospace.1 The bond strength (peel force) between the film and substrate serves as a crucial indicator for evaluating film performance. When the bond strength is weak, the film-substrate interface may fail in various ways under tensile or bending loads. Buffer layer materials such as alumina (Al₂O₃) and chromium (Cr) can form chemical bonds with the polymeric substrate, thereby enhancing the film–substrate interfacial bond strength.2 In this study, the 90° peel behavior of flexible films was numerically simulated using the Dynamic-Explicit module of the ABAQUS finite element software, and cohesive elements were employed to describe the interfacial adhesion characteristics between the metal layer and the polymeric substrate. On this basis, the effects of different substrate materials (PP, PI, PET), the thickness of the copper layer, and the introduction of a chromium interlayer on the film–substrate interfacial bond strength of flexible films were investigated. The findings indicate that the peel force at the flexible film-substrate interface increases with the elastic modulus of the substrate material, the maximum peel strength of the PI substrate is 0.455 N/mm. The interfacial bond strength of the flexible film increases gradually with increasing metal-layer thickness. Taking the system without a buffer layer (PET polymer substrate and a 500 nm copper layer) as a reference, the introduction of a chromium buffer layer increases the film–substrate interfacial bond strength by approximately 10%. Through simulation analysis, the parameters of the substrate and buffer layer can be optimised to enhance the interfacial bond strength between the rigid and flexible film substrates, thereby reducing the risk of flexible film failure.
Funding: The LiaoNing Transplant with Soil Program of Revitalization Talents Plan (XLYC2204011).
References:
1. X. H. Lu, M. Hao, K. Liu*, et al. Metalized plastic current collectors: Bridge to high energy density reconciling high safety for lithium-ion batteries. Journal of Energy Storage, 2025, 125, 116813.
2. Marx V. M., Toth F., Wiesinger A., et al. The influence of a brittle Cr interlayer on the deformation behavior of thin Cu films on flexible substrates: Experiment and model[J]. Acta materialia, 2015, 89: 278-289.