Calendering of Silicon-Containing Electrodes and Their Influence on the Mechanical and Electrochemical Properties

Abstract

The process chain of electrode production includes calendering as a crucial process step to enhance the volumetric energy density as well as to influence the particle-pore-structure and simultaneously the mechanical and electrochemical properties of the electrode coating. A further way to improve the volumetric energy density is the usage of other materials with higher specific capacity, such as silicon instead of graphite as the active material for anodes. In this study, both opportunities, calendering and using silicon-containing composites, are combined to investigate the relations between material, process and performance. The applied line loads for the compaction are correlated with the silicon mass fraction and lead to a silicon-dependent mathematical model to estimate further line loads for silicon-graphite-composite electrodes. On the basis of established analyzing methods for adhesion strength and deformation behavior, it is shown that with increasing silicon content, the elastic deformation of the electrode coating rises. In addition, the overall porosity of the electrodes is less affected by silicon than the pore size distribution compared to graphite electrodes. Furthermore, the electrical conductivity decreases at higher silicon contents independent of coating density. Moreover, the long-term electrochemical stability deteriorates with increasing silicon content and coating density.

The Influence of Calendering on the Fast Charging Performance and Lithium Plating of Hard Carbon Blend Anodes

“…Due to the aforementioned more elastic deformation behavior of the HC particles compared with the Gr particles, higher line loads are apparent for the Gr/HC blend anodes. Consequently, the formation of new particle bonds with the current collector at higher calendering forces is impeded, which was also recently shown for silicon/Gr composites by Scheffler et al [ 32 ]…”

“…Due to the aforementioned more elastic deformation behavior of the HC particles compared with the Gr particles, higher line loads are apparent for the Gr/HC blend anodes. Consequently, the formation of new particle bonds with the current collector at higher calendering forces is impeded, which was also recently shown for silicon/Gr composites by Scheffler et al [32] Moreover, it can be observed that blending Gr and HC leads to an overall increase in adhesive strength compared with the pure material of Gr. This can be explained by the distribution of the HC in the blend.…”

The Impact of Calendering Process Variables on the Impedance and Capacity Fade of Lithium‐Ion Cells: An Explainable Machine Learning Approach

“…A calendering study with multiple compression levels is conducted in ref. [25] considering silicon-containing composites in electrodes. It shows that the silicon content directly affects the electrode deformation after calendering.…”

Influence of Different Alginate and Carboxymethyl Cellulose Binders on Moisture Content, Electrode Structure, and Electrochemical Properties of Graphite‐Based Anodes for Lithium‐Ion Batteries

“…Since it has been shown in various studies that calendering can significantly influence the microstructure of electrodes, the anodes were not calendered. [14][15][16]…”

“…The decrease of mechanical properties occurs due to the breakage of particle-binder interactions, since the increase of mechanical properties can be traced back to increasing particle-particle interlockings. [14,15] In contrast, electrodes with a too dense microstructure, due to high calendering, can lead pore blockage for electrolyte wetting, and this increase of density can ultimately lead to limitations of lithium diffusion. [14,41,42] In the context of high calendering of electrodes, improved mechanical properties through particle-particle interlocking cannot be guaranteed, and too high calendering should be avoided.…”