Analyses of the Calendaring Process for Performance Optimization of Li-Ion Battery Cathode

Abstract

Olivine structure LiFePO 4 (LFP) was synthesized via solid state processes, using Li 2 CO 3 , NH 4 H 2 PO 4 , and FeC 2 O 4 ⋅H 2 O and C 12 H 22 O 11 as precursor materials. The effects of calendaring are analyzed in terms of electrochemical performance, cycle life, surface morphology, and ac impedance analysis. The resulting LFP electrode was divided into calendared and uncalendared samples. Under electrochemical impedance testing, the calendared and uncalendared electrodes exhibited a charge transfer resistance of 157.8 Ω and 182.4 Ω, respectively. The calendared electrode also exhibited a higher discharge capacity of about 130 mAh/g at 0.1 compared to a discharge capacity of 120 mAh/g at 0.1 for the uncalendared electrode.

Current and future lithium-ion battery manufacturing

“…Although few studies have been done on the new calendering methods due to the low manufacturing cost (5.19% of the total cost) and mature state-of-the-art technology, the significance of calendering parameters should not be ignored. The studies showed that both calendered LiFePO4 and organic dilithium benzenediacrylate cathode had better electrochemistry performance and cycle stability than the cathodes without calendering ( Oladimeji et al., 2016 ; Oltean et al., 2016 ). The swelling behavior after calendering can increase the pressure inside the cell and may cause further safety concerns.…”

Evaluation of Deformation Behavior and Fast Elastic Recovery of Lithium‐Ion Battery Cathodes via Direct Roll‐Gap Detection During Calendering

“…Through the calendering process, the electrode volumetric energy density increases and the mechanical properties become more uniform, reducing the product variations. [1][2][3][4][5][6] The calendering is a continuous roll compaction process during which the electrode, a composite of a particulate system coated on a thin collector foil, moves into the gap between two rolls where a load is applied on the electrode, resulting in a reduction of the coating thickness and thus an increase in coating density. While the effects of the electrode compaction on the product properties, especially on electrochemical performance, are published in several studies and are well known, the machine behavior during compaction, the circumstances within the gap, as well as the fast elastic recovery also known as the springback (SB) effect only has received little attention until now and shall therefore be main object in this study.…”

“…The impact of the electrode compaction on anodes and cathodes is different, as the used material systems differ. While it was shown for anodes that a high compaction leads to an ionic diffusion limitation and thus, a deterioration in electrochemical performance, [2][3][4]6] a gentle compaction can reduce the irreversible capacity loss and improve the cyclability. [7] Sheng et al [8] found similar correlations for wettability.…”

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.…”

“…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 . An analysis of the pore structure by mercury porosimetry shows that compressing cathodes leads to smaller pore sizes .…”