Calendering is a critical component of the electrode manufacturing process that dictates the electrical conductivity and structural integrity of a lithium-ion battery. If advances are to be made in integrating energy dense, thick electrodes into gigafactory production, then understanding the impact of calendering on the underlying microstructural evolution during processing is crucial.

Research has been undertaken to develop a digital calendering and electrochemical testing workflow by researchers at the University of Sheffield and UCL. Expertise in simulation of large-scale particulate systems at Sheffield was overlayed with simulations at UCL to produce accurate models of the calendering process, which was correlated with subsequent electrochemical analysis. A high-resolution 3D image of an electrode was acquired, which formed the basis of discrete element method (DEM) calendering simulations. Whilst DEM simulations have traditionally relied on simplified electrode structures, uniquely, this work has been able to accurately recreate features resolved from tomographic data within the DEM framework. DEM simulations can be used to study mechanical and transport properties at active material particle scales, as well as microstructure evolution under different calendering conditions.

The workflow enables new rational insight into the calendering process, which has traditionally been optimised empirically. This work paves the way for the evaluation of next generation electrodes and the required step change in the manufacturing process for improving the energy and power density of lithium-ion batteries.

Image: An electrochemical simulation of active material utilisation within a realistic, X-ray CT-based, NMC622 electrode microstructure

Case study published December 2022.