## 3 Results and Discussion
### Mercury Intrusion Porosimetry and N\({}_{2}\)-Physisorption
In addition, insights into different porosities (total, accessible), pore shape, structural homogeneity, and specific pore surface area can be gained and result in a comprehensive overview of the electrode microstructure. Measuring the pore throats instead of pore bodies with MIP can be beneficial to understand ionic transport within an electrolyte, as ion mobility is limited by the narrowest passage on a pathway through the electrode pore network. Therefore, MIP is considered to be a major method for characterizing LIB composite electrodes. Considering N\({}_{2}\)-physisorption, information about micro- (<2 nm), meso- (2-50 nm), small macropores (>50 nm) and the BET specific surface area, \(\sigma_{BET}\), can be gained, which can support the correct interpretation of the MIP results. The linear isotherms of the N\({}_{2}\)-adsorption experiments are shown in Figure 6a (type II isotherm [14]). As determined by MIP, the specific inner surface area of the electrodes increased for lower porosity, which was attributed to cracking of secondary AM particles during calendering. Fitting of the linear region of the isotherms with the BET model resulted in a linear trend with regard to increasing \(\sigma_{BET}\) at reduced total electrode porosities as shown in Figure 6b. The specific surface area doubles from uncalendered electrodes (44%) to highly densified electrodes (18% porosity), which can be used as indicators for the quantification of the extent of particle cracking as a consequence of extensive calendering. Due to the presence of micropores, the quantitative validity of the BET model is limited, as the processes of micropore filling and monolayer-multilayer adsorption might interfere [14; 47]. Therefore, the results of the BET model represent an apparent specific surface area. From the \(t\)-plot (Figure S2), a micropore surface area of \(\approx\)0.3 m\({}^{2}\) g\({}^{-1}\) was found for all investigated electrode porosities. With a constant micropore surface area, the comparison of the BET surface areas remains valid. In comparison to the specific pore surface area from MIP, MIP showed approximately twice the values of N\({}_{2}\)-physisorption (Table 2 compared to Figure 6b). One reason is the possible shift in the PSD to smaller values in the MIP measurement, which results in a higher amount of smaller pores and a higher surface area. Another reason lies in the use of different models of the two methods to calculate the specific surface area. The BET model based on the specific monolayer capacity of the adsorbent in the electrode and \(\sigma_{porc}\) from MIP simplifies the pore network to geometric shapes (here: conical). The latter model was also affected by changes in the pore shape due to the calendering of the electrodes. Therefore, \(\sigma_{BET}\) calculated from N\({}_{2}\)-physisorption should be used to describe the structure of the porous electrodes and to calculate the tortuosity (quadratic correlation between surface area and tortuosity) based on the model of Carniglia [16]. A change in the specific surface area can have a significant effect on the LIB performance and cycle life [48]. Cracking of AM particles results in an increased active specific surface area, which, however, can ultimately lead to enhanced detrimental side reactions between the AM surface and electrolyte [49]. Looking at the hysteresis of the isotherm (Figure 6c, inserted graph, type H3 [14]), mesopores were present in the calendered electrode, while they were absent in the uncalendered electrode showing no AM particle cracking or densification of the CBD. The shape of the hysteresis indicates the presence of slit-shaped pores, since the desorption branch was shallow and parallel to the adsorption branch over a wide pressure range [50].