Femtosecond Laser-Structured Nickel Foams in Different Atmospheres as Current Collectors for Supercapacitor Applications

Currently, three-dimensional (3D) porous nickel (Ni) foams and meshes are widely used as electrodes or current collectors due to their remarkable electrochemical properties, making them popular in the development of high-performance supercapacitors. In this study, we investigate the effects of femtosecond (fs) laser structuring on Ni foams in both air and inert argon atmospheres to increase their specific surface area by generating micro/nanostructures and laser-induced periodic surface structures (LIPSS). These surface modifications are intended to improve the electrochemical performance of Ni foams as electrodes and current collectors for stable and efficient supercapacitors. The femtosecond-structured Ni foams demonstrated up to a 165% increase in surface area, attributed to the formation of uniform LIPSS with a periodicity of 1.0 ± 0.2 μm due to laser ablation. Ni foams structured in an argon environment, featuring both micro/nanostructures and LIPSS, achieved the highest specific capacitance of 1796.7 mF/cm² at a 2 mV/s scan rate and 406.3 mF/cm² at a 3 A/g current density, outperforming those structured in air and unstructured foams. Nyquist plots revealed that fs-structured Ni foams exhibited minimal ohmic and charge transfer resistance, indicating excellent charge transfer properties. Consequently, the choice of the gaseous environment during laser ablation plays a crucial role in enhancing electrical characteristics, including cyclic stability, energy density, and power density.