Simulation-Supported Analysis of Calendering Impacts on the Performance of Lithium-Ion-Batteries

Abstract

A combination of experimental and model based analysis was performed to investigate calendering impacts on the performance of lithium-ion-batteries. When discharging, not only geometric parameters, such as electrode thicknesses and porosities are affecting performance. Calendering also impacts on other parameters, such as the effective ionic conductivity within the electrolyte, the effective electronic conductivity of solid active material and the effective solid-liquid interfacial area. The simulation supported method is shown to complement experimental analysis to understand correlations between calendering and these parameters; it enables to identify cell internal parameters which are hard to measure and to analyze how the lithium transport is affected. In experiments, cells containing non-calendered cathodes performed significantly worse than ones with 22%-calendered cathodes. Simulation indicated that this losses consist mainly of a deterioration of effective electronic conductivity leading to overpotentials close to the separator. Minor contributions to the losses in non-calendered cathodes caused by the geometric compaction and a reduction of effective solid-liquid interfacial area were found as well, whereas the impact of effective ionic conductivity turned out to be only insignificantly small.

Manufacturing Process for Improved Ultra‐Thick Cathodes in High‐Energy Lithium‐Ion Batteries

“…Therefore, we assign an average conductivity of the AM and carbon black to the solid phase. The resulting effective conductivity of the entire electrode was 0.0914 (±0.0025) S m −1 , which was in the range commonly reported in the modeling of Li‐Ion batteries . An extension of the model considering the contribution of the CBD separately is planned for future work.…”

Physico‐Chemical Modeling of a Lithium‐Ion Battery: An Ageing Study with Electrochemical Impedance Spectroscopy

“…The surface isolation of the SEI/electrolyte interface as well as the thickness of the SEI show a constant increase within the overall cycle range. Nevertheless, even if the loss of active material at the two electrodes does not have an equal impact on the capacity and impedance of the cell, it is reported to occur on the anode due to SEI isolations [45][46][47] and on both electrodes due to particle cracking and loss of connectivity between active material and current collector. For the cathode a high degree of isolated area is identified.…”

“…The percental loss of active material after 350 cycles (13.27 %) is not in complete agreement with the measured percentage loss of the SoH (16.67 %) of the cell until this cycle, because we assume to loose active material at both anode and cathode, while the loss of the limiting electrode has a higher impact on the capacity change. Nevertheless, even if the loss of active material at the two electrodes does not have an equal impact on the capacity and impedance of the cell, it is reported to occur on the anode due to SEI isolations [45][46][47] and on both electrodes due to particle cracking and loss of connectivity between active material and current collector. [28,48] In conclusion, the values for the identified ageing parameters might not be completely exact, because the newly introduced ageing model has not been validated yet and might not include all relevant ageing processes, but it could be shown, that the chosen set of ageing parameters is not only sufficient to reproduce the measured change in the impedance spectrum but is also in the right order of magnitude and can be reasonably well correlated to physical processes.…”

Model‐Based Uncertainty Quantification for the Product Properties of Lithium‐Ion Batteries

“…[2–7] and by simulation in refs. [2,3,8]. In addition, thermodynamic properties of the active material will deviate due to processes before the actual manufacturing process; for example, the specific capacity of graphite is dependent on the degree of disorder, which is caused by the temperature in the prior processes …”