Characterization of Adhesion in Lithium-Ion Battery Electrodes With Laser-Textured Current Collectors

Large volumetric changes during lithiation and delithiation of high-energy-density active materials, together with variations in mechanical properties associated with water-based binders, exacerbate problems relating to loss of contact between the active materials and metallic current collectors in Li-ion battery electrodes. Laser texturing has been proposed as a possible solution to the problem, representing an alternative to chemical surface treatments. To facilitate the evaluation of this process, the present work seeks to characterize mechanical adhesion between active materials with carboxymethylcellulose (CMC) binder and aluminum and copper current collectors, providing information linking laser processing parameters, surface topography, and oxide formation to adhesion. Experiments were performed with a 104-ns pulsed fiber laser, varying the pulse fluence and separation distance in both the scanning and lateral directions. Topography analysis revealed values of interfacial area ratio (Sdr) in the range of 21–53% for laser-textured current collectors. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analysis showed oxygen content in the range of 4–13 at% for laser-textured current collectors compared to 1.5–2.1 at% for untextured materials. Mechanical scratch tests revealed large increases in mechanical adhesion between the active material and current collectors of complete electrodes after laser texturing of the latter, with the critical load increasing from 2 N to more than 4 N (maximum: 5.3 N) for cathodes and from 2.3 N to more than 9 N (maximum 12.7 N) for anodes.