The interface between electrolyte and cathode is a primary factor affecting the performance of solid oxide fuel cells (SOFCs). Enhancing the chemical compatibility of the interface, fortifying the charge conduction, and mitigating the interdiffusion of elements between the interfaces are imperative to optimize the performance of SOFC single-cells and ensure a long-term operational stability. This review represents the methodologies used to enhance the interface between electrolyte and cathode in recent years. These methodologies encompass the optimization of cathode composition and structure, the design and construction of multilayer composite electrolyte, and interfacial reinforcement methods. These approaches serve as a valuable reference for SOFC development and application.

At the cathode layer, a dense electrolyte and a porous electrolyte backbone are constructed. A solution infiltration technique is utilized to prepare highly active nano-cathodes within the porous electrolyte backbone, thereby eliminating the macroscopic interface between the electrolyte and the cathode. Advanced coating techniques and infiltration technique are employed to modify the cathode surface, thereby enhancing cathode electrochemical performance and single-cell operational durability. The development of novel cathode materials, regulation of component ratios within composite cathodes, and the addition of negative thermal expansion materials prove effective in enhancing the thermal expansion compatibility of the cathode. The thermal-expansion offset enhances long-term electrode durability and ORR activity.

At the electrolyte layer, constructing multi-layer electrolyte films and optimizing the structure of single cell enhance performance and reduce degradation. Multi-layer composite structures improve an electrolyte reliability and a cathode interface chemical compatibility. However, the preparation becomes a challenge and primarily relies on advanced coating technologies. Low-cost, high-density coating technologies are urgently needed, and a hydrothermal in-situ growth technique emerges, thus reducing production costs, while enhancing single-cell performance and long-term durability.

At the electrolyte-cathode interface, the contact between the electrolyte and the cathode directly affects the interface resistance, oxygen ion conduction, and interface bonding strength. Therefore, interface reinforcement can effectively improve the energy efficiency and stability of single cells. The dense nanostructure functional layer (NFL) overcomes the physical limitations of the porous cathode-dense electrolyte interface, thus enhancing single-cell performance, interfacial bonding, and long-term durability.

This review summarizes some research work related to the interface between the electrolyte and cathode in SOFCs, thus providing a reference for the development of high-performance and long-term durability. This review also provides a reference for SOEC research and development since the materials and structure of solid oxide electrolysis cells (SOECs) are similar to those of SOFCs.

The interfacial contact and charge conduction between the electrolyte and cathode have a direct impact on the performance and efficiency of single cells, which is a crucial area in both fundamental research and technological development of SOFCs. The following perspectives for future development are provided.

The development of novel electrolytes and electrode materials represents an effective strategy to address interfacial issues. Concurrently, the exploration of innovative interfacial structural designs can enhance the performance and stability within existing material systems. Future research endeavors should prioritize meeting the practical demands of industrial applications. Furthermore, it is essential to optimize the preparation process. The quality of the interface between the electrolyte and the cathode directly affects the overall performance of SOFCs. Therefore, optimizing the preparation process is of crucial importance. Currently, coating technologies such as pulsed laser deposition (PLD) and chemical vapor deposition (CVD) can achieve a precise preparation of specific compositions and structures. In the future, it is necessary to focus on the research and development of new high-performance, low-cost thin film preparation technologies with large-scale manufacturing capabilities to further improve interface quality. In addition, there is a focus on interdisciplinary research. Various in-situ spectroscopic characterization methods, machine learning and artificial intelligence technologies will also contribute to SOFCs research, including material performance prediction, parameter optimization design, and operating condition performance simulation. This can promote the connection between theoretical models and practical applications, driving SOFCs technology toward higher efficiency and lower costs. Finally, despite significant progress in lab-scale research, the commercialization of SOFCs still faces some challenges. In the next phase, it is necessary to further optimize the cell preparation process and operating conditions, such as electrolyte structure, composite electrode materials, and sintering processes. Reducing costs, improving cell reliability and lifespan can promote SOFCs widespread application in the energy sector.