Femtosecond laser cutting of LiFePO₄ electrodes: Kerf geometry, process optimization, and electrochemical performance

Electrode cutting is crucial to the safety, performance and cost of various batteries. Femtosecond laser is emerged recently as an accurate and manipulable cutting technology. However, in the early stages of its development, fundamental aspects encompassing kerf quantification, edge characterization, processing mechanism, parameters optimization, and performance improvement have not been systematically investigated yet. This study delves into the laser cutting of the widely-used LiFePO₄ electrode, meticulously elucidating the influence of laser cutting on the chemical composition, crystallographic structure, kerf geometry and morphology of LiFePO₄ electrode. The characteristic dimensions of the cut kerf, including delamination width, gap width, melt width, and heat affected zone (HAZ), are explicitly defined. The effect of processing parameters, i.e. laser power and cutting speed, on the cutting quality and electrochemical properties is specifically analyzed. In particular, the severe consequence of HAZ is intentionally studied. Our findings indicate that, laser-cut electrodes exhibit superior kerf quality and battery performance compared to that of mechanically cut electrodes when the laser energy density is less than 2500 J cm⁻², and the mechanism of performance improvement by optimized laser cutting is comparatively discussed with traditional mechanical cutting. This work provides a comprehensive evaluation framework of laser-cut electrodes, combining assessments of kerf quality and electrochemical performance. It lays a theoretical and technical foundation for novel laser cutting in the fabrication of high-quality and high-performance battery electrodes.