Femtosecond Laser Treatment of Copper Current Collectors and Their Application in Li-Ion Batteries

Current collectors (CCs) play an important role in enhancing the electrochemical performance of lithium-ion batteries (LiB). Research shows that increasing the surface roughness of copper foil helps improve the bonding strength between the current collector and the active material, reduces the contact resistance between them, and consequently enhances the battery's rate discharge performance and cycling stability. In the present work, a copper current collector modification by femtosecond laser treatment forming quasiperiodical nanostructures was proposed. The modified current collectors were examined through scanning electron microscopy (SEM) imaging and roughness measurements and further tested with silicon particles in Li-ion cells through galvanostatic charge/discharge experiments. As a result of the laser process, one can observe increasing contact between the current collector and the active material grains, which creates a buffer zone for the volume expansion of the active material during charging and discharging. The results show increased specific capacities, cyclabilities, and Coulombic efficiencies for modified current collectors compared with standard copper foil. It was demonstrated that implementing laser treatment into standard procedures of electrode manufacturing for lithium-ion batteries can easily improve the electrochemical performance of active materials, especially those that experience large volume changes during cycling.