Pore-scale modeling and investigation on the effect of calendering on lithium-ion battery cathodes

Abstract

The cathode of lithium-ion batteries (LIBs) is a porous electrode that has a crucial influence on cell performance and durability. In making the electrode, a metal foil is first coated with a cathode slurry and dried. The electrode then undergoes a hard-pressing by rollers, i.e., calendering process. In the present study, the effects of calendering on the cathode's effective transport properties and its impact on the battery's charging performance are investigated using a multiscale approach. Microscopic images of LiNi0.8Co0.1Mn0.1O2 samples are obtained using X-ray computed tomography and SEM. This material's three-dimensional microstructure is generated using a numerical reconstruction algorithm based on the distribution characteristics of active material, additives, and pores observed from the microscopic images. Pore-scale simulations are performed on models of various calendering ratios (CRs) to evaluate the pore distribution, effective lithium-ion diffusivity, and electrical conductivity of the cathode material at different CRs. The computed effective transport properties of the cathode are applied to a macroscopic model to study the charging performance of LIBs at various CRs. It is found that the battery performance increases with CR and reaches optimal electrochemical performance at CR = 20 %. When the cathode is calendered to CR = 35 %, the battery's charging performance deteriorates, and this effect is more pronounced at high charging rates. The present study demonstrates a multiscale approach combining experiment characterization and pore-scale simulation for investigating the effects of calendering on LIB cathode. This approach can be employed for the future optimization of LIB fabrication processes.