Effect of calendering on structure and electrochemical performance of LiNi0.33Mn0.33Co0.33O2 cathodes via 3D reconstruction based on X-ray computed tomography images with different pressures

Abstract

Calendering, a key step in electrode manufacturing process, directly changes the 3D electrode structure through applied pressure, thereby significantly influencing electrochemical performance. To establish quantitative relationships of calendering-electrode structure-electrochemical performance, 3D microstructures of LiNi_0.33Mn_0.33Co_0.33O₂ cathodes are reconstructed based on X-ray computed tomography images under different calendering pressures. Four microstructure-resolved half-cell models with lithium (Li) anodes were developed for 3D electrochemical simulations, validated against experimental discharge curves. The evolution of the electrode structure caused by calendering and its effect on the electrochemical performance are discussed. The simulated discharge curves are in good agreement with the experimental data. The results show that increasing the calendering pressure can significantly reduce the thickness and porosity of the electrode, increase the tortuosity of the electrode, and significantly improve the discharge capacity of the electrode. An increased discharge rate reduces the state of lithiation (SOL) of active material (AM) particles, thereby reducing the discharge capacity of the electrode. Furthermore, calendering increases the gradient of the SOL of AM particles and decreases the gradient of the Li-ion concentration of electrolyte in the thickness direction of the electrode. The developed integrated model deepens our understanding the relationship of calendering-electrode structure-electrochemical performance and provides a valuable physical basis for optimizing the electrode manufacturing process.