Investigation of calendaring parameters on the microstructure of graphite anodes within lithium-ion batteries: Insights from ultrasonic testing
Erdogan Guk, Mona Faraji Niri, Timothy A. Vincent, Geanina Apachitei, Calum Briggs, Begum Gulsoy, Sheng D. Chao, Zhen Guo, Jonathan E.H. Sansom, James Marco
Abstract
The study explores the application of ultrasonic testing to analyse the impact of the calendaring process on the microstructure of graphite anodes within a lithium-ion battery. It examines the correlation between calendaring parameters such as roll gap and line speed, and their impacts on ultrasonic signal characteristics. Our study reveals that different sample thicknesses responded differently to the calendaring process. Specifically, the amplitude of the first peak increased for thinner samples (<45 μm) post-calendaring, indicating improved material uniformity, whereas thicker samples (>50 μm) demonstrated increase in Time of Flight with reduced attenuation in acoustic signal. Notably, thinner electrodes (45 μm) exhibit a substantial density increase from 0.95 to 1.6 gr/cm³, surpassing the density gain in thicker electrodes (100 μm) which rise from 1.0 to 1.3 gr/cm³ under identical calendaring conditions. This initial study confirms that a clear correlation exists between the properties of the acoustic waveform and variations in the calendaring process parameters. These results will form the basis of a future study investigating the possible in-line sensing, process control and quality assessment of electrode manufacture. The data obtained from this study's characterisation process has the potential to underpin a data-driven model to predict calendaring performance using machine-learning methods.