## 3 Results
### Voltages Losses during Cell Cycling  
The voltage drop during discharging can generally be described in terms of the resistances in the cell [29]. As explained at the beginning, these resistances are due firstly to the charge transport (ionic and electronic) and secondly to the charge transfer on the cathode and anode side (Equations (13) and (14)).  
Figure 6a shows the ionic resistance in the cathode compartment for a discharge rate of 1/8C. The resistance profiles across DoD for four exemplary segments are plotted in this figure, with segment #20 located closer to the separator and segment #70 located closer to the current collector. For each segment, an increase in resistance is observed as the discharge progresses, which can be related to the change in porosity since the solid fraction increases with the DoD. However, the more dominant factor is the position of the segment in the cathode space. Segments closer to the center of the cathode have a smaller exchange surface area due to the cylindrical shape of the cell. Accordingly, the resistance value changes with the position of the segment (Equations (13) and (14)).  
During the discharge process, ions must migrate from the separator to the site of the reaction in the cathode. At the beginning of the discharge process, the site of the reaction is on the inside of the separator (segment #1) and migrates deeper into the cathode space as the discharging continues. The so-called reaction front has already been described in the literature by [PERSON] et al. [32] and can also be reproduced by the model presented here. The longer the distance of the ions to the reaction front, the higher the resistance to be overcome. This effect is amplified by the increasing resistance value of segments close to the current collector. Thus, the voltage value slowly decreases at the beginning of the discharging cycle and the \(NiCl_{2}\) plateau is formed. Due to the longer distance to the reaction front and the increasing resistance of the segments, the voltage drops more and more until it finally reaches the open circuit voltage of \(FeCl_{2}\). Here, a second reaction front corresponding to the iron reaction is formed, which again starts at the segment directly facing the separator. Accordingly to this, the voltage losses become small again and the iron plateau is formed.  
Due to the Ohmic character of the ionic resistance, a stronger voltage drop is observed for higher C-rates (Figure 5a). With this voltage drop, the end-of-discharge voltage is already reached at smaller DoDs, which is accompanied by a loss in capacity for higher C-rates. This is particularly evident in the voltage curve for 1/2C discharge in Figure 5a.  
Besides the ion transport resistance, the released electrons must also overcome a resistance in the metallic network. The electron resistance is plotted across the segments in Figure 6b for 1/8C discharge as an exemplary case. The highest value is found directly at the current collector due to the smallest exchange surface area, which is consistent with the results for ionic resistance. Nevertheless, the overall electron resistance is relatively small in comparison to the resistance due to ion transport. Therefore, the impact of electron transport on the cell voltage is neglected in this model. This finding is also consistent with the results in the literature [14; 15]. The electron resistance may become important for different cathode compositions, for much higher current rates or due to changes in the particle morphology, for instance, by ageing effects.