# Investigation of Laser Cutting Width of LiCoO\({}_{2}\) Coated Aluminum for Lithium-Ion Batteries
## 3 Result and Discussion  
The cutting width of the laser cut samples can be defined by Top Width, Melting Width, and Kerr Width. Each width is shown in Figure 2. The top width is the width where the active electrode material is ablated by the laser, the melting width is the width where the current collector is melted with melting marks, and the kerf width is the width where the all layers are fully separated. Figures 3-6 show the change of the widths depending on the laser parameters. The Y axis shows the width, and the X axis of the graph is the laser cutting speed (a) and volume energy (b). The volume energy (\(E_{line}\)) is defined as follows  
\[E_{line}=\frac{P_{laser}}{V_{s}\,\times\,A}\,\,[\frac{\mathrm{J}}{\mathrm{m}^{ 3}}] \tag{1}\]  
where \(P_{laser}\) is a laser power, \(V_{s}\) is scanning speed, and \(A\) is a laser spot area. This volume energy can be defined also as dividing laser power by scanning speed. This study takes the former definition, which considers both the laser intensity and scanning speed, since the laser intensity is a more effective parameter than the laser power for cutting applications. Figure 3 shows the variation of top width depending on the scanning speed (a) and volume energy (b). As the laser scanning speed increases, the top width decreases. No top width is observed when the laser scanning speed is greater than 2500 mm/s when the laser power is 50 W. According to Figure 3b, the top width increases as the volume energy increases. However, when the volume energy is less than 6.0172 \(\times\) 10\({}^{10}\) J/m\({}^{3}\), no active electrode material is removed. Therefore, the threshold of the volume energy to the remove active electrode material is between \(4.8138\times 10^{10}\) J/m\({}^{3}\)-\(6.0172\times 10^{10}\) J/m\({}^{3}\). In addition, two regions are \begin{table}
\begin{tabular}{c c} \hline \hline
**Category** & **Cathode** \\ \hline Structure & One-side sandwich \\ Active electrode Material & LiCoO2 \\ Active electrode Thickness & 30 [\(\mathrm{\SIUnitSymbolMicro m}\)] \\ Binder & Polyvinylidene fluoride \\ Conducting agent & SuperC65 \\ Ratio & 90:5:5 wt \% \\ Solution & N-Methyl-2 pyrrolidone \\ Current collector Material & Aluminum \\ Current collector Thickness & 20 [\(\mathrm{\SIUnitSymbolMicro m}\)] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cathode manufacturing parameters. Figure 1: Cathode sample and Experimental set-up. observed with two different slopes. Since the slope decreases, we expect that plasma may be formed and affect to the cutting process [16]. Not only this plasma formation, but also the complete penetration of the sample may affect to the slope decrease. Figure 4a shows the melting width depending on the laser scanning speed and laser power. The melting width decreases as the scanning speed increases, which is a very similar trend to the top width. The melting width is always observed when the laser power is between 100 W and 250 W. However, no melting is observed when the laser power is 50 W. When the laser power is greater or equal to 100 W, both the top and melting widths are clearly observed. This indicates that the volume energy under these laser power and scanning speed is enough to remove the active electrode material. On the other hand, it is only the top width that is observed when the laser scanning speed is less than 2500 mm/s and the laser power is 50 W. This indicates that there is not enough volume energy to  
Figure 3: (**a**) Top width VS. Scanning speed; (**b**) Volume energy. Figure 2: Definition of measured width. remove the active electrode material. For the laser power of 50 W, it is assumed that the top width is invariable in depth and material removal rate can be calculated as follows  
\[MRR\ [\frac{\mathrm{mm}^{3}}{\mathrm{min}}]=D*W_{\mathrm{top}}*v \tag{2}\]  
where \(D\) is depth, \(W_{\mathrm{top}}\) is top width, and \(v\) is velocity.