Method Development for Quality Control of Suspensions for Lithium-Ion Battery Electrodes

Abstract

A method to determine the agglomerate and aggregate sizes of carbon black (CB), commonly used in anode and cathode suspensions for lithium-ion battery electrodes, is presented. An analysis via light diffraction and scattering was evaluated, and measuring parameters and the development of sample preparation are described in detail. Within this work, different dispersing additives were tested with regard to their ability to stabilize the CB agglomerates and aggregates after dispersing. Furthermore, a sample preparation routine was set up which enables the determination of CB particle sizes in about 10 min. This includes the separation of active material particles and the particle size analysis itself. Furthermore, the method was tested with discontinuously and continuously processed suspensions using a laboratory dissolver and a pilot-scale extruder. In these experiments, the progress of CB deagglomeration in the dispersing step could be proven. For this reason, the method represents a suitable instrument for a quality check in an early production stage.

Extrusion‐Based Processing of Cathodes: Influence of Solid Content on Suspension and Electrode Properties

“…To understand the outcome better, Figure shows the size distribution of the CB particles. In accordance with other authors, a bimodal distribution in a range of 10 µm to below 1 µm is apparent . The first peak in the range below 1 µm represents the CB aggregates, whereas the second peak between 1 and 10 µm portrays the CB agglomerates.…”

“…The slurry characterization was done by rheological and particle size analysis. The size of the CB particles was measured according to Dreger et al Two samples were taken and measured after the extrusion process. The CB particles in the slurry of each sample were stabilized with 80 wt% TEGO 670 (Evonik).…”

“…Dreger et al developed a method for measuring the size distribution of CB in the suspension via a pretreatment and laser diffraction analysis. As a result, the influence of different mixing process parameters on the CB particles within the suspension and, later on, their influence on electrode properties as well as electrochemical performance could be assessed …”

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

“…CB (measured by laser diffraction) used in this work consists of permanently bound primary particles (aggregates, Figure : peak at ≈– and Figure b), which merge to agglomerates (Figure : peak at ≈– and Figure a) . During dispersion, these particles are stressed by fluid forces and agglomerates break into aggregates, as seen by the decreasing agglomerate peak.…”

“…The particle size of CB was measured via the laser diffraction and scattering method based on the Fraunhofer diffraction and Mie scattering theory with a Horiba LA‐960. The measurement procedure and the sample preparation for cathode slurries were according to Dreger et al…”