A new 1D lithium-ion cell electrode model is presented, which, for the first time, considers the electrochemical coupling between particles of a real particle size distribution obtained from tomography data. It does so without actually resolving the 3D electrode microstructure in the model, but by including all necessary information in a homogenized manner, using microstructure data from high-resolution X-ray tomography. Additionally, the transport of lithium through the solid-electrolyte interphase (SEI) is considered. The effects of the particle–particle coupling are shown for a graphite negative electrode from a cylindrical high-power cell. The extended homogenized 1D porous electrode model provides an explanation for the vanishing plateaus in the graphite potential curve with increasing charge or discharge rates. This effect is not covered by state-of-the-art models.