Observing Fibrillation Processes in Dry Battery Electrode Materials Using X-ray Diffraction

Introduction

In the traditional slurry-based electrode coating process, binders, additives and active materials for lithium-ion batteries (LIBs) are mixed with a solvent to create a battery slurry. This slurry is then applied onto a current collector before evaporating the solvent by drying. The drying process, including the recovery of the solvent for subsequent use, is an energy- and time-intensive step that requires complex machinery, occupying a significant amount of space on the production line. Additionally, the solvents commonly used are often toxic, posing an environmental and health risk.

The production of dry battery electrodes (DBE) is a promising alternative that avoids solvents and uses polytetrafluoroethylene (PTFE) binders, that form fibrils under elevated temperatures and shear. During this fibrillation process, the PTFE particles transform into highly oriented fine strands, The resulting cohesive powder mixture can then be processed into free-standing films or directly be applied to current collectors. 

Different PTFE binder types show different fibrillation behavior and processability, and each of them has a specific process window (i.e. PTFE amount in electrode mixture, temperature, processing time) to achieve the ideal cohesive intermediate for further processing and electrochemical performance of the final battery cell.

While PTFE is only partially crystalline (1), it can clearly be identified by X-ray diffraction due to the significant 100 reflection at approx. 18° 2θ (Cu radiation). With increasing processing input energy for fibrillation, the crystallinity decreases, indicated by an intensity loss of the crystalline peaks. To determine the fibrillation progress and to establish the most suitable process windows for fibrillation, representative DBE materials can be extracted during processing and investigated with X‑ray diffraction.

References

1. “Determining the Percentage Crystallinity of Polymers using X-ray Diffraction” available at: https://www.anton-paar.com/corp-en/services-support/document-finder/application-reports/determining-the-percentage-crystallinity-of-polymers-using-x-ray-diffraction/, 2025