3D microscale modeling of NMC cathodes using multi-resolution FIB-SEM tomography

The electrochemical performance of the lithium-ion battery (LIB) is intimately linked to the electrodes' microstructure dictated by the arrangement of the different constituents. The conductive binder domain (CBD) is of critical importance to battery performance; however, the impact of CBD content on electrode performance is not uniquely identified without altering its morphology. Herein, we use realistic digital cathode microstructures reconstructed from focused ion beam scanning electron microscopy (FIB-SEM) tomography with multiple magnification levels for two NMC111 cathodes to assess the sensitivity of the effective electronic conductivity to the intrinsic conductivity of the CBD and active material (AM), deconvolute the impact of CBD content from morphology on effective transport properties, and highlight the impact of CBD nanoporosity on the pore phase tortuosity. The effective electronic conductivity is more sensitive to changes in the bulk conductivity of the conductive additives where increasing their conductivity by one order of magnitude results in a 10-fold increase in the effective conductivity. Additionally, while the CBD content alone with fixed morphology brings about a nonlinear change in the effective conductivity, the CBD morphology is critical even though it becomes less significant at high CBD contents. Finally, the CBD nanoporosity can lower the tortuosity by similar to 17%.

Automated summary

By using realistic digital microstructures of cathodes, it was found that the conductivity of conductive additives has a larger impact on the effective electron conductivity of the electrodes. The morphology of the conductive binder domain also affects the effective conductivity, while nanoporosity within the binder can decrease tortuosity.