Processing of a Large-Scale Microporous Group on Copper Foil Current Collectors for Lithium Batteries Using Femtosecond Laser

Due to the thin thickness (≈8 μm) and soft nature of copper foil current collectors, it is extremely difficult to process large-scale micro–nano holes on their surface. In this study, trepanning drilling of a copper foil current collector with a 1030 nm femtosecond laser system is investigated with emphasis on developing the processing technology of copper foil current collectors with different entry and exit sizes while maintaining good hole quality. The effects of laser parameters on the processing quality of copper foil current collectors are comprehensively studied. The relationship between geometric morphology and processing parameters as well as the formation mechanism is fully discussed. The smallest hole taper is found at a defocusing amount of −1.8 mm. Consequently, a group of holes with 250 000 micropores is obtained on a (2 cm × 2 cm) current collector, demonstrating the high efficiency and high quality of femtosecond laser-based processing. Half-cells with a modified current collector operate with a more stable response than half-cells with unmodified copper foil at cycle performance and rate performance.