Geometrical size effect on tensile properties of ultrathin current collector foils for lithium-ion batteries

Mechanical properties of the current collector foils are of great urgency to the reliability design and security assessment of high-performance lithium-ion batteries, but non-standard specimens with different dimensions and geometries have been frequently used to evaluate the properties of materials. Here, we investigated the effects of specimen dimensions on the mechanical properties of current collector Al and Cu foils with different gauge lengths and widths by using the digital image correlation technique. Our results revealed that the wider specimens and shorter gauge lengths tended to have higher total elongation. A widely cited Oliver formula and a new probabilistic model for crack nucleation were proposed to describe the geometrical size-dependent elongation. The proposed models have been proved to be in excellent agreement with the present metal foils and the reported ones.