## 3 Results
### Simulations with Spatially-Resolved Equivalent Electrical Circuit  
With the srEEC introduced in Section 2.3 the performed EIS sets on the test cell were simulated. In Figure 8 the current distribution together with the local SoC, the voltages over the RC-elements, the resistance values for \(R_{ct,x}\) as well as the simulated cell voltage \(V_{cell}\) are shown over time during discharging of 5% SoC with \(-3\) I\({}_{20}\). On the left side, the results for homogeneous electrolytes are shown. The local SoCs differ by less than 2% from each other at the end of simulation time. The difference was generated during the previous cycles with \(\pm 4.5\) I\({}_{20}\), \(\pm 1.5\) I\({}_{20}\) and \(\pm 8\) I\({}_{20}\). Because of the grid resistance the currents \(I_{t}\) and \(I_{b}\) differ from each other. In the example in Figure 8 the current difference is 0.1 A (6.7% of \(-3\) I\({}_{20}\)). This generates the difference between the SoC values. The differences between top and bottom of the voltage drops and of the resistance values are small, too. On the right side the results of the same discharge pulse are presented, but with stratified electrolyte as it was the case during _Strat. 1_. The local SoCs have already a difference of almost 60%, differences between local currents and voltages are clearly visible. The top part of srEEC is discharged with only \(-0.23\) A, while the bottom part is discharged with \(-1.27\) A. This difference generates a difference in the charge-transfer resistances and also a huge SoC difference. While the current rate in the bottom part is larger during discharging, it is smaller during charging, when the electrolyte is stratified. During the simulated reference measurements after stratification (_Ref. 2_), the current rate in the top part is larger for charging and discharging. Because of the lower  
Figure 8: Simulated current distribution in the srEEC during discharging with \(-3\) I\({}_{20}\). \(SoC_{x}\), \(V_{cell}\), \(V_{RC,x}\), \(I_{x}\) and the values for \(R_{ct,x}\) are shown. On the left side the results from simulation with homogenous acid are presented, on the right side with stratification as during _Strat. 1_. SoC in the bottom part and the consequently larger resistance values, this inhomogeneous current distribution arises during simulated _Ref._2. The corresponding impedance spectra for the discharge pulses in Figure 8 are presented in Figure 9 on the left side. On the right side spectra with \(+3\) I\({}_{20}\) DC-current are presented. The spectra with homogeneous electrolyte can be compared with _Ref._1 and the spectra simulated with stratification can be comparable with _Strat._1. The first semi-circle increased with the presence of stratification. The increase is larger for charging DC-current, like in the measurements. The high-frequency tail, which crosses the x-axis, is also increased with stratification, which was not the case in the measurements. In Figure 10 the fitting results of the simulated spectra during _Ref._1, _Strat._1 and _Ref._2 are presented. For fitting an EEC with only one layer of inductance, ohmic resistance and one RC-element was used like for the fitting of the measured spectra. The values for \(R_{ct,neg}\) from simulation increased from _Ref._1 to _Strat._1, as in the measurements. Between _Strat._1 and _Ref._2 the charge-transfer resistance does not change. The capacitance \(A_{dl,neg}\) at stratification is for some currents smaller and for some currents larger than at the reference _Ref._1. For _Ref._2 the capacitance is decreased, which is differently to the measurements. \(\zeta\) is not affected by stratification as it could be observed in the measurements. The resistance \(R_{oblmic}\), is larger at stratification than at _Ref._1 for the DC-currents \(\pm 3\) I\({}_{20}\), \(\pm 1\) I\({}_{20}\) and \(+8\) I\({}_{20}\), which does not match to the measurements.