Impacts of Variations in Manufacturing Parameters on Performance of Lithium-Ion-Batteries

Abstract

Cell performance of lithium-ion-batteries (LIB) can be tailored to particular hybrid or full electric vehicle applications by targeted adjustment of manufacturing parameters. Furthermore there is a large number of cathode material compositions which can be used. Knowing the correlations between these parameters, electrode structures and cell performance is important to reach the high requirements posed by electromobility. Within this study, impacts of essential manufacturing parameters, being active material mass loading, calendering stress load and carbon black content on the cell performance were investigated for two different, promising cathode materials. For NMC and LMO, the respectively highest calendering stress load and carbon black content yielded the best performance as losses due to poor electronic conductivity were reduced. The active material mass loading rather influenced the ratio between specific energy and specific power. Finally two optimally performing parameter configurations could be identified which were, depending on the required application: NMC with high mass loading and LMO with medium mass loading; in both cases the highest calendering load and carbon black content were applied. An analysis of statistical reproducibility dependent on various parameter configurations was carried out as well. A significant improvement of reproducibility could be achieved by increase of calendering stress load.

Modelling of the Calendering Process of NMC‐622 Cathodes in Battery Production Analyzing Machine/Material–Process–Structure Correlations

“…This can be explained by lower inhomogeneities within the particle‐pore structure at higher densities . Calendering is also important to reduce product quality deviations in terms of C‐rate performance . Investigations of lithium iron phosphate (LFP)‐cathodes have shown that the influence of densification increases significantly with higher C‐rates as well as rising number of cycles.…”

“…The mechanical homogenization through calendering [17] leads to a homogeneous aging of the cell [17,18] and results in a lower standard deviation of the discharge capacities. [18] This can be explained by lower inhomogeneities within the particle-pore structure at higher densities. [19] Calendering is also important to reduce product quality deviations in terms of C-rate performance.…”

“…[19] Calendering is also important to reduce product quality deviations in terms of C-rate performance. [18,20] Investigations of lithium iron phosphate (LFP)-cathodes have shown that the influence of densification increases significantly with higher C-rates as well as rising number of cycles. The compacted LFP-cathodes have a lower capacity loss over the number of cycles compared with the uncalendered counterpart.…”

“…[13] As indicated in the literature, the porosity determines the area of application of the lithium-ion cell in addition to the materials used. [18] In previous works, the machine behavior was not taken into account although the porosity differs depending on the condition of the electrode before calendering, on the machine behavior of the calender as well as on the selected process parameters. Since the calender rolls are in direct contact with the electrodes, it is important to consider the machine as a further influencing factor in addition to the other process parameters mentioned.…”

Analysis of the 3D microstructure of experimental cathode films for lithium‐ion batteries under increasing compaction

“…In recent years, the systematic structuring of electrodes has become more and more important in battery research, see Song et al (2010), Wang et al (2012) and Vu et al (2012). The cathode manufacturing process, which involves, among others, mixing, coating, drying or calendering, strongly influences the electrochemical performance, see Bockholt et al (2013), Lenze et al (2017), Lenze et al (2018) and Bockholt et al (2016). For example, the electrical pathways can be improved, among others, by adding graphite or calendaring, see Bockholt et al (2016).…”