Structural and Electrochemical Properties of Calendered Lithium Manganese Oxide Cathodes

Abstract

Lithium manganese oxide in a spinel structure (LiMn2O4, LMO) is a cathode material of non‐toxicity, low costs, and a high electrochemical potential. In contrast manganese dissolution, structural fatigue, and microcracks lead to poor cycling stability and capacity fading. Regarding a basic understanding of the influence of the calendering process and the consequent electrode structure on the life span of sensitive active materials, cathodes with various coating densities have been manufactured and analyzed in terms of structural and mechanical properties. Consequences of high mechanical stress applied by calendering in order to achieve the desired cathode densities are breakages of the active material particles, leading to a diminished life span during the electrochemical characterization. An optimal coating density of ca. 2 g cm−3 for the investigated cathodes as a compromise of C‐rate performance, due to electrical conductivity, and long‐term cycling has been found.

Analyzing Bending Stresses on Lithium‐Ion Battery Cathodes induced by the Assembly Process

“…Cathode electrodes were provided and characterized by Christiane Schilcher (Institute for Particle Technology, TU Braunschweig). Further details are published in “Structural and electrochemical properties of calendered LMO cathodes” …”

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

“…The curve described previously corresponds to the graph shown in the literature and has already been explained. [11,28,29] The shear stress between the roller and electrode bonds the interface between substrate and coating at low compaction rates. At higher compaction rates, the adhesion strength increases again, for example by better embedding of the particles in the binder carbon black matrix or by pressing the hard NMC particles into the substrate foil (see Figure 6).…”

“…[5] However, there is a conflict of objectives in the selection of the target porosity between good ionic conductivity (high porosity) [6][7][8] and high electrical conductivity (low porosity). [6,7,[9][10][11] To resolve this conflict, a specific porosity is calendered, which represents the best possible compromise between the two properties described. [12,13] Output parameters of each subprocess of battery production are simultaneously the input parameters for the subsequent process step due to the linear production sequence (see Figure 1 on the left).…”

Influence of the Carbon Black Dispersing Process on the Microstructure and Performance of Li‐Ion Battery Cathodes

“…Hence, to optimize the properties of lithium‐ion battery electrodes, the structure has to be improved . Several research projects have already investigated the influence of the active material type or additives on electrode properties and cell performances. These previous studies showed that it is difficult to define a direct correlation between the process and the product because physical changes in the electrode microstructure are not considered.…”