## 3 Results and Discussion
By charging the fresh cell, the barycenter position of the anode distributions shifts from 0.5014 \(\pm\) 0.0002 to 0.4589 \(\pm\) 0.0001 in the Compton scattering intensity and from 1.3510 \(\pm\) 0.0017 to 1.3977 \(\pm\) 0.0017 in the S-parameter. By discharging the cell, the barycenter position of the cathode distributions shifts from 0.4937 \(\pm\) 0.0001 to 0.4896 \(\pm\) 0.0001 \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Averaged S-Parameter**} & \multicolumn{2}{c}{**Lithium Composition**} \\ \cline{2-5}  & **Charged State** & **Discharged State** & **Charged State** & **Discharged State** \\ \hline Cathode & 1.590 \(\pm\) 0.005 & 1.590 \(\pm\) 0.005 & 0.124 \(\pm\) 0.077 & 0.130 \(\pm\) 0.078 \\ \hline Anode & 1.785 \(\pm\) 0.005 & 1.783 \(\pm\) 0.006 & 0.055 \(\pm\) 0.022 & 0.046 \(\pm\) 0.023 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The averaged S-parameter and corresponding lithium composition in the charged and discharged states in the aged cell. Figure 4: In the aged cell: (**a**) The Compton scattering intensity distribution in the charged state. (**b**) The Compton scattering intensity distribution in the discharged state. (**c**) The S-parameter distribution in the charged state. (**d**) The S-parameter distribution in the discharged state. in the Compton scattering intensity and from 1.5723 \(\pm\) 0.0014 to 1.5928 \(\pm\) 0.0019 in the S-parameter. These results correspond to Figure 3.  
The distributions between the Compton scattering intensity and S-parameter in the aged cell are different from those of the fresh cell, as shown in Figure 5c,d. The barycenter positions of the cathode and anode distributions do not show a significant change between the charged and discharged states. These values in the cathode of the charged and discharged states are 0.4840 \(\pm\) 0.0001 and 0.4836 \(\pm\) 0.0001 in the Compton scattering intensity and 1.5903 \(\pm\) 0.0016 and 1.5898 \(\pm\) 0.0016 in the S-parameter, respectively. These values in the anode of the charged and discharged states are 0.4177 \(\pm\) 0.0001 and 0.4155 \(\pm\) 0.0001 in the Compton scattering intensity and 1.7802 \(\pm\) 0.0016 and 1.7807 \(\pm\) 0.0017 in the S-parameter, respectively. The distribution of the anode in the 0.37-0.4 regions in the Compton scattering intensity and the 1.6-2 regions in the S-parameter appears in the aged cell. This region is highlighted in orange dotted circles in these figures. As the lattice volume of the anode expanded with degradation, as shown in both the Compton scattering intensity and S-parameter distributions in Figure 4, a stable phase of the LiAl alloy is formed in the VL2020 cell by repeating the charge-discharge cycle. Here, the three possible alloys are AlLi, Al\({}_{2}\)Li\({}_{3}\), and Al\({}_{4}\)Li\({}_{9}\) in the Al-Li binary diagram [33]. Additionally, two phases of \(\beta\)-AlLi and AlLi\({}_{2-x}\) are also confirmed experimentally [34]. As a result, the distributions that are shown in the orange dotted circles in Figure 5c,d appeared. The region with low Compton scattering intensity and a high S-parameter value near the interface between the cathode and separator in Figure 4 corresponds to the 0.2-0.3 regions in the Compton scattering intensity and to 2.3-2.8 in the S-parameter values in Figure 5c,d. This region is highlighted  
Figure 5: The correlation between the Compton scattering intensity and S-parameter. The data obtained from the cathode, anode, and separator are shown in green, red, and blue circles, respectively. (**a**) The charged state of the fresh cell. (**b**) The discharged state of the fresh cell. (**c**) The charged state of the aged cell. (**d**) The discharged state of the aged cell. The distribution regions characterizing the aged cell are highlighted in blue and orange dotted line circles in Figure 5c,d. in the blue dotted circles in these figures. A possible reason for this distribution appearing near the surface of the separator on the aged cell is the electrolyte decreasing due to the generated microbubbles.