Reducing the working temperature of the solid oxide fuel cell (SOFC) to a intermediate temperature of 600~800 ℃, or even a low-temperature region below 600 ℃, is an important direction for the future development of solid oxide fuel cells. The development of electrolytes with high ionic conductivity at low temperatures plays an important role in its development,while the traditional three-layer electrolyte has inevitable drawbacks in structure. Merely designing electrolyte materials cannot fundamentally solve the effect of the interface between the solid oxide fuel cell electrolyte and the cathode and anode on the performance of the fuel cell. In response to this problem, researchers have developed a new type of electrolyte free fuel cell (EFFC) through the design of solid oxide fuel cell structure and functional layer materials. This paper outlines the development history of traditional three-layer solid oxide fuel cell electrolytes using yttria-stabilized zirconia (YSZ), doped ceria , and doped LaGaO3 as electrolytes, and briefly describes the use of advanced thin film preparation technologies (electrophoretic deposition, magnetron sputtering, atmospheric plasma spraying, high velocity oxygen fuel flame (HVOF) spraying, etc. ) in the preparation of solid oxide fuel cell electrolyte layers. The focus is on the research progress of a new type of electrolyte free fuel cell (EFFC) designed by the energy band theory, and the prospects of using energy band theory and its properties to design materials with electronic conduction characteristics as functional layers are prospected.