스퍼터링에 의한 고성능 세라믹 전해질 나노구조 및 박막 고체산화물연료전지 적용 최적화에 관한 연구
- Solid oxide fuel cell (SOFC) is a new type of green energy technology developed in recent years, which has the advantages of no corrosion, high energy conversion efficiency, strong fuel adaptability and long life. A solid oxide fuel cell is an all-solid-state fuel cell that uses a ceramic material (YSZ, GDC) that can conduct oxygen ions as an electrolyte. Since only two phases (gas phase and solid phase) are required, the principle is more efficient than any other fuel, so the principle is more straightforward than any other fuel cell. SOFC does not have the electrolyte management issues faced by phosphoric acid fuel cells (PAFC) and molten carbonate fuel cells (MCFC). The high operating temperature also means that no precious metal electrocatalyst is required, clean and efficient energy.
However, at the same time, the exceptionally high working temperature of SOFC has higher requirements on the thermal stability, high-temperature strength, electronic conductivity, thermal expansion matching and chemical stability of each component, which increases the difficulty of material selection. The anode or cathode supported electrolyte film can be prepared to reduce the fuel cell's internal resistance by reducing the electrolyte's thickness. This paper uses the magnetron sputtering technology in physical vapor deposition (PVD) to prepare thin-film electrolytes. It has many advantages, such as high deposition rate, wide sputtering range, high density of film formation, and sputter deposition of large-area targets.
With the continuous development and improvement of magnetron sputtering technology, the properties of thin films have been greatly improved. However, the process conditions during the sputtering process play an essential role, and the sputtering conditions have become the main factor affecting the properties of the thin film/substrate. In this experiment, the effects of different sputtering conditions on the structure and properties of the electrolyte film were studied by changing the process conditions such as sputtering pressure, sputtering power, and the distance from the target to the substrate.
During the preparation of fuel cells, due to the difference in thermal expansion coefficient and elastic modulus of the matrix and film materials, each component's degree of shrinkage and expansion is different, and residual stress will be generated in the film. The excessive residual stress will reduce the strength of the material. Moreover, even lead to peeling and tearing of the film, failing the film structure. Therefore, it is of great significance to accurately measure the residual stress of the fuel cell film. In this paper, XRD is used to analyze the stress state of the film. The experiments show that with the increase of sputtering pressure, the stress state of the YSZ film changes from compressive stress to tensile stress, and the lattice spacing is calculated according to Bragg's law. As a result, the lattice spacing is more significant than In the normal phase, the existence of residual stress is proved.
To characterize the effect of electrolytes prepared under different sputtering pressure conditions, each electrolyte was applied on AAO-supported SOFCs composed of Ni anode and Pt cathode. No obvious defects or pinholes were seen in the electrolyte, while the electrodes exhibited a highly porous structure that provided sufficient channels for the reactants. The formed thin film solid oxide fuel cell was electrochemically characterized, and finally, the YSZ thin film solid oxide fuel cell prepared at 3mTorr sputtering pressure achieved an open-circuit voltage (OCV) of 1.043 V, and a maximum power density of 1.593W/cm^2 were achieved at 500 °C, providing guidance and reference for improving and improving the film properties.
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