## 4 Conclusions and Outlook  
Positive electrodes with porosities ranging from 18% to 44% were prepared and analyzed regarding their porosity and pore size distribution. Each measuring technique showed its advantages and different insights into the microstructure of the electrodes, whereby possible inaccuracies of the methods were discussed and compared in detail. Therefore, variations in the total porosity should be specified as integer values, as the significance of the decimal place is considered unreasonable for composite electrodes. Moreover, the entire pore size range of composite electrodes cannot be covered by applying only a single method. Only a combination of the methods enabled a complete characterization of the electrode microstructure. For the complete range of pore sizes (except micropores) in LIBs, MIP provides the best overview and reproducibility, and due to the large number of samples, is representative for electrode production. However, closed pores cannot be measured directly and the electrode densities, measured with a gauge, He-pycnometry, and X-ray diffraction, are necessary for the correct interpretation of MIP results. A comparison with N\({}_{2}\)-physisorption enables the determination and exclusion of deviations induced by effects such as pore-blocking. With the technique access to micropores, gas-based methods are particularly relevant for electrodes that are highly densified and have a major fraction of micro- and mesopores or other battery systems such as solid-state batteries. A combination of FIB/SEM tomography and 3D modeling of the electrode provides the most descriptive overview for all types of pores and the opportunity for a direct transfer to other topics of interest, such as Li-ion mobility, hence, the electrochemical performance of the electrodes in LIBs. Here, an unresolved nanoporosity of the CBD with a given tortuosity can be respected in electrochemical GeoDict [56]. Above all, the importance of the correct representation of the CBD becomes clear.  
The effects of different porosities on the electrochemical performance of LIBs and lithium metal batteries are currently under investigation and will be published shortly. For hands-on research, it is particularly relevant how the pore structure within the electrodes behaves in combination with an electrolyte and how it changes as the cells cycle. In any case, as a basis for further investigations of electrode properties, an in-depth understanding of the electrode microstructure and porosity is essential.  
The following are available online at [[https://www.mdpi.com/article/10.3390/batteries/7040070/s1](https://www.mdpi.com/article/10.3390/batteries/7040070/s1)]([https://www.mdpi.com/article/10.3390/batteries/7040070/s1](https://www.mdpi.com/article/10.3390/batteries/7040070/s1)), Figure S1: Additional SEM cross-sectional images of embedded electrodes, Figure S2: \(t\)-plots from N\({}_{2}\)-physisorption, Figure S3: 3D model of the FIB/SEM tomography.  
Conceptualization, methodology, investigation, writing--original draft preparation, T.B.; simulation, model building and validation, M.F. and C.W.; supervision, writing--review and editing, M.W. and M.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Federal Ministry of Education and Research: 03 XP0109A; Federal Ministry for Economic Affairs and Energy: 03 ETE018B; Federal Ministry of Education and Research: FoFeBat.  
Not applicable.  
The authors would like to thank the German Federal Ministry of Education and Research (BMBF) for financial support within the \"BCT--Battery Cell Technology\" project (03 XP0109A) and the Research Fab Battery Cells (FoFeBat). The authors of Math2 Market GmbH would like to thank the German Federal Ministry of Economic Affairs and Energy for financial support within the \"structure\" project (03 ETE018B).  
The authors declare no conflict of interest.