## 3 Results and Discussion
### Width, Removal Energy, and Cut Surface of the Uncompressed Cathode  
Figure 7a shows the kerf width of the uncompressed cathode. Uncompressed cathodes have a narrower kerf width than compressed cathodes at the equal volume energy. The kerf width is not formed with the laser power of 50 W. When the scanning speed is faster than 2500 mm/s, the kerf width is not formed at the laser power of 100 W. Increasing the scanning speed from 500 mm/s to 2500 mm/s exponentially decreases the kerf width at the laser power of 100 W. According to volume energy, the volume energy greater than 9.628 \(\times 10^{10}\) J/m\({}^{3}\) is required to form the kerf width with the laser power of 100 W. When the laser power is the 150 W, the kerf width is formed from the scanning speed of 500 mm/s to 5000 mm/s. The kerf width exponentially decreases as the scanning speed increases from 500 mm/s to 2500 mm/s and then linearly decreases. When the kerf width decreases exponentially, kerf width shows a relatively greater variation. However, when the kerf width decreases linearly, its value is around 10 um with relatively little variation. When the laser power is the 200 W and 250 W, a similar trend as observed from the kerf width with the laser power of 150 W is observed. Figure 7b shows the top width. Overall, the top widths decrease as the scanning speed increases. The top width with the laser power of 250 W and 200 W linearly decreases from the scanning speed of 500 mm/s to 5000 mm/s. When the scanning speed is between 500 mm/s and 1500 mm/s, almost similar values are observed. When the scanning speed is faster than 1500 mm/s, the variation of the top width  
Figure 6: The cross-section of the compressed cathode with the scanning speed of 2000 mm/s. is smaller than the variation of the top width from 500 mm/s to 1500 mm/s. On the other hand, the top widths at the laser power of 200 W and 50 W linearly decrease from 500 mm/s to 5000 mm/s. More interesting characteristics can be observed at the laser power of 150 W. Increasing the scanning speed from 500 mm/s to 1500 mm/s decreases the top width exponentially. Also, increasing the scanning speed from 2000 mm/s to 5000 mm/s linearly decreases the top width. The relationship between the volume energy and the kerf width as well as the volume energy and the top width are shown in Figure 7 (right) with trend lines. The kerf width and the top width are dependent on the volume energies. Furthermore, an increase in volume energy causes a logarithmic increase in the kerf width and the top width. The correlation coefficient of the kerf width is 0.9049 and the correlation coefficient of the top width is 0.8929. Since it is rather close to 1, it was indicated that the variables are positively logarithmically related. Figure 8 shows the average values of energy required to remove cathodes. This is obtained by Equation (5). Remove energy decreases exponentially as increasing scanning speed for all laser powers. Remove energy also decreases when the laser power decreases. In addition, remove energy logarithmically increases as the volume energy increases. Unlike the compressed cathode, the remove energy required for the uncompressed cathode depends on laser intensity and interaction time. Figure 9 shows SEM images with the laser power of 250 W. Figure 9a is the top view and Figure 9b is the cross-section view. The melting width is not formed as shown in Figure 9a and it is invisible to all cut samples used in this study. Thus, no clearance width can be seen. Figure 7: Comparison of (**a**) kerf width and (**b**) top width of the uncompressed cathode. For the cathodes cut at the scanning speed of 500 mm/s to 2000 mm/s, the kerf width is not uniform as shown in Figure 9a. Likewise, from the scanning speed 500 mm/s to 2000 mm/s, the cross-section of the current collector was not a clean surface, because the current collector was re-solidified. Thus, excessive cutting is observed with the laser cutting of 500 mm/s to 2500 mm/s.