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The effects of Li 2 CO 3 and LiOH on the ionic conductivity of BaCe 0.9 Y 0.1 O 3 (BCY)-x%Li 2 CO 3 (x = 0, 5, 10 and 30) and BCY-y%LiOH (y = 0, 2, 5 and 8) composite electrolytes were investigated. Symmetrical cells with the structure of foam Ni–Ni 0.8 Co 0.15 Al 0.05 LiO 2 (NCAL)∖BCY-x%Li 2 CO 3 or y%LiOH∖foam Ni-NCAL and Pt∖BCY-x%Li 2 CO 3 or y%LiOH∖Pt were prepared with NCAL-coated foam Ni and porous Pt as symmetrical electrodes, respectively. The ionic conductivity test results of the cells with Pt as the symmetrical electrode showed that the addition of LiOH did not improve the ionic conductivity of the BCY electrolyte, while the addition of Li 2 CO 3 could significantly improve the ionic conductivity of the BCY electrolyte. The maximum power density of the cells with the structure of foam Ni-NCAL∖BCY-x%Li 2 CO 3 or y%LiOH∖foam Ni-NCAL decreases with the increase in the amount of Li 2 CO 3 or LiOH, which indicates that adding Li 2 CO 3 or LiOH to BCY via mechanical mixing did not improve the electrochemical performance of the cells with NCAL as the electrode, and the NCAL electrode has the greatest impact on the performance of the cells. The interface of Li 2 CO 3 and BCY should be a high-speed channel for ion conduction. Increasing the effective area of the interface between BCY and Li 2 CO 3 and optimizing its continuity in the electrolyte should be the main development direction for improving the ionic conductivity. • Adding Li 2 CO 3 could significantly improve the ionic conductivity of BCY electrolyte. • Adding LiOH cannot improve the ionic conductivity of BCY-LiOH composite electrolyte. • NCAL anode has the greatest impact on the performance of new structure SOFC. • Increase the effective interface area of Li 2 CO 3 /BCY is the key to enhance conductivity. [ABSTRACT FROM AUTHOR]

A solid oxide fuel cell with 1.2 mm thick nanocrystalline BCY (BaCe 0.9 Y 0.1 O 3) electrolyte was prepared by the copressing method, and its electrochemical performance was tested in H 2 /air conditions. The maximum power density of the nanocrystalline electrolyte cell prepared with BCY powders calcined at 1000 °C and operated at 550 °C in H 2 is 405.2 mW cm−2. The carriers of nanocrystalline BCY electrolyte were studied by using double-layer electrolyte cells with pure oxygen ion conductor GDC (Gd 0.1 Ce 0.9 O 2) and proton conductor SCY (SrCe 0.95 Y 0.05 O 3), sintered at high temperatures as proton and oxygen ion filters. It is found that nanocrystalline BCY is a mixed conductor of oxygen ions and protons. The results of hydrogen and oxygen concentration cells show that the transference number of oxygen ions in the nanocrystalline BCY prepared in this study is higher than that of protons. XPS and HRTEM results of BCY particles before and after performance testing showed that an amorphous layer containing a high concentration of oxygen vacancies and suspected carbonate was formed on the surface of BCY particles after fuel cell performance testing. We believe that the amorphous layer should be a high-speed ion conduction channel for nanocrystalline BCY electrolyte during performance testing. • The ionic conduction mechanism of nanocrystalline BZY electrolyte was studied. • It is found that nanocrystalline BCY is a mixed conductor of oxygen ion and proton. • The transference number of oxygen ions in BCY is higher than that of proton. • An amorphous layer on the surface of BCY is considered to be ion conduction channel. [ABSTRACT FROM AUTHOR]