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

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.