Solid oxide fuel cells (SOFCs) can convert the chemical energy of fuels directly into electricity. This endows them with high efficiency, clean operation and fuel flexibility, positioning SOFCs as an attractive solution for distributed generation, heavy-duty transport and portable power. The commercialization is accelerating, and the performance bottlenecks shift from materials to interface. The existing electrodes and seals meet most requirements, the electrode-interconnect contact becomes the immediate determinant of stack performance. This review represents recent progress on the electrode-interconnect interface in SOFC stacks, covering microstructural evolution, contact-resistance mechanisms and optimization strategies, enlarging the contact region, tuning stack clamping pressure, improving current-collector materials and refining protective coatings to inform the design of next-generation, high-power, long-life and low-cost stacks.

The anode side is always in a strongly reducing atmosphere, so the interface is essentially metal-to-metal (Ni versus metallic interconnect) and can, in principle, yield an extremely low contact resistance. The cathode side is an oxide-to-oxide non-metallic contact with much higher resistance. In a previous work, the anode-interconnect contact resistance was only 6 µΩ·cm², whereas the cathode-interconnect value approached 200 mΩ·cm²-five orders of magnitude higher-rendering the anodic contribution negligible.

Contact resistance is approximately inversely proportional to the real contact area. Increasing the contact area is thus a primary route to lower losses and higher power. Moderate enlargement improves electron collection, but an excessive coverage shrinks the oxygen diffusion cross-section and rapidly raises concentration polarization.

Current collector layers are not flat. Micron-scale "peaks and valleys" contact at room temperature, and mismatched thermal expansion during heat-up widens these gaps, sharply increasing resistance or even causing electrode spalling. A controlled external clamping load introduced during stack assembly therefore becomes essential to reduce contact resistance, while maintaining flatness and gas-tightness. Resistance decreass nonlinearly with pressure. It is therefore critical to balance low contact resistance with structural integrity. It is demonstrated that cathode imprint area and penetration depth can serve as quantitative indicators.

Enlarging contact area or penetration depth both require an added current-collector layer that simultaneously acts as a "high-speed electron highway" and a "stress cushion". Its intrinsic conductivity, high-temperature oxidation resistance and thermo-mechanical compatibility govern interface resistance and long-term stability. Noble metals (i.e., Pt, Ag) are first considered for the cathode side due to their stability and conductivity. Perovskites and spinels are also viable alternatives. To marry the performance of noble metals with cost-effective oxides, composite collectors such as LSM+Ag and LSM+Pd are fabricated. Completely noble-metal-free routes employ low-softening glass or inorganic binders that sinter into glass-ceramic interpenetrating networks to enhance adhesion.

For practical stacks, metallic interconnects inevitably oxidize in high-temperature air, causing the increase of ASR and threatening lifetime. A single coating that suppresses oxidation and maintains a low interfacial resistance is therefore highly desirable. Previous studies used perovskite cathodes directly as protective layers, but their high densification temperature hindered large-scale application. Spinel coatings-especially Mn-Co spinel are preferred because they combine high electronic conductivity, excellent oxidation resistance and moderate sintering temperatures.