Mechanical properties of commercial copper current-collector foils

Abstract

The functionality and reliability of the current collector (CC) are crucial to design and fabricate electrodes for Li-ion batteries because the CC serves as the bridge between external electronic and internal Li-ion transports. Therefore, understanding the mechanical behavior of CCs is of great importance for battery design and manufacturing. In this paper, we report the measured values of the elastic moduli of six commercial copper current-collector (CCC) foils. Measurements were performed using three techniques: a standard microtensile testing machine equipped with a laser sensor, dynamic mechanical analysis (DMA), and nanoindentation. For electrolytic copper (E-Cu) foils, we find elastic moduli of approximately 70 GPa, and for rolled copper (R-Cu) foils, we find elastic moduli of approximately 50 GPa. Values for yield strength and fracture strength of the foils were determined from load-deflection curves; the results are consistent with values recommended by the manufacturer. Crystalline structures, which influence values for the elastic moduli of the foils, were investigated by X-ray diffraction. Surface morphologies of the foils before testing and the fracture morphologies after testing were studied by scanning electron microscopy.