Microstructure design of battery electrodes is key to enable fast charge and higher capacity in next-generation lithium and sodium ion batteries. While porous-electrode (Doyle–Fuller–Newman-type) models capture the coupled transport–reaction physics governing cell performance, they typically treat the electrode as a homogenized medium and encode microstructure only through fitted, scalar “effective” parameters (e.g., Bruggeman-type tortuosity). This assumption is often adequate for uniform electrodes, but it breaks down for modern architectures with graded porosity, binder migration, bimodal particle distributions, or bilayer designs, where transport resistance is heterogeneous and reaction rates localize, leading to non-uniform utilization and premature rate limitations.