Abstract
<jats:p>Reliable assessment of buried solid–solid interfaces is essential for understanding and improving electrochemical devices including solid-state batteries. Electrical measurements such as electrochemical impedance spectroscopy provide an attractive (operando) diagnostic but probe interfacial contact only indirectly through its influence on charge transport. Consequently, the extent to which interfacial morphology can be inferred from the electrical response remains unclear. Here, we use 3D electric network simulations to study how interfacial morphology governs the impedance detectability of non-ideal contacts at constriction-dominated interfaces. The resulting general principles are discussed using metal dissolution at interfaces with fast charge-transfer kinetics as a representative case. We show that no universal detection threshold exists. Instead, detectability depends on the remaining contact area, the lateral distribution of contact and non-contact regions, and the sample thickness. In limiting cases with small, finely distributed pores, contact losses exceeding 90% may remain largely undetectable, whereas localized contact loss produces pronounced impedance features at substantially higher remaining contact areas. These findings reveal a morphology-induced diagnostic blind spot in impedance-based interface analysis and demonstrate that the absence of a measurable interface signal does not necessarily imply intimate or stable interfacial contact. This diagnostic blind spot therefore challenges the reliability of conclusions and material parameters derived from electrical measurements without independent knowledge of the underlying interface morphology.</jats:p>